RadiationSimulationPublicResults
Introduction
This page shows public results from the Radiation Simulation Working Group.The FLUKA simulations have focused more on the needs of the ID/ITK communities, and FLUGG for the muon systems. The GCALOR and GEANT4 studies have focused more on radiation background issues in the calorimeter systems.
Interactive web page for radiation environment exploration
A set of interactive web-pages to explore radiation backgrounds in the ATLAS experiment is presented, obtained with the Athena/GEANT4 simulation framework for a configuration corresponding to the Run 2 data taking period (2015-2018). Particle fluence, energy spectra, ionising dose and detector material compositions are easily inspected at different locations of the experiment. Cavern region: WebRadMaps_Full_R2_public.html Calorimeter/InnerDetector region: WebRadMaps_Zoom_R2_public.htmlComparisons between measurement and simulation:
Timepix (April 2021)
New methods have been developed for measuring radiation field quantities in ATLAS with the Run-2 data of the Timepix detector network [1,2]. After a first iteration of Timepix/Geant4 comparisons [3], charged particle fluences can now be compared to Geant4 predictions with improved reliability and thermal neutron fluence comparisons are introduced. The counting of charged particles uses the tracking capabilities of the Timepix ASICs as well as pattern recognition algorithms that reject background, which is mainly composed of gamma particles. The reconstruction efficiency of algorithms and the impact of detector packaging on incident particles were assessed using dedicated simulations for different particle types and energies. This allowed the computation of detection efficiency distributions that could be used to extract a signal at the different locations of the Timepix hodoscopes, given the predicted spectra. Two approaches were considered to compare the Timepix and Geant4 particle fluences. First, an exclusive approach involved subtracting the Geant4-predicted background to the Timepix measurement. While being a standard approach, this technique suffers from large uncertainties where background is dominant. To mitigate this effect, an inclusive approach was additionally developed, by assuming equality between the signal-over-measurement ratios between Timepix and Geant4. The thermal neutron fluence determination with a Timepix hodoscope involves counting events below a LiF neutron converter layer, placed in-between the two silicon sensors of the hodoscope. Subtracting events from a converter-free area leads to a net signal, which was calibrated in a known thermal neutron environment. The predicted neutron energy spectra from Geant4 are convoluted with the neutron capture cross-section for 6Li [6] normalized to its value at 0.025 eV to calculate the thermal neutron fluence in Li-rich environments. While this method leads to greater discrepancies than ionizing dose and charged particle fluence benchmarking, and will need further efficiency studies, results are in reasonable agreement with Geant4. Geant4 simulations used for the presented comparisons were performed with the A3 Pythia tune [4] and a typical Run-2 ATLAS geometry tag [5]. They are obtained from 50k simulated proton-proton collision events, assuming an inelastic cross section of 78.42 mb at a center-of-mass energy of 13 TeV. An update of Geant4/Timepix comparisons of total ionizing dose is also presented here, which was done with the same methodology as in [3] but with the more recent simulation [5]. [1] B. Bergmann et al., ATLAS-TPX: a two-layer pixel detector setup for neutron detection and radiation field characterization, J. Instr. 11 no. 10 (2016).[2] B. Bergmann et al., Characterization of the Radiation Field in the ATLAS Experiment With Timepix Detectors, IEEE Trans. Nucl. Sci. 66 no. 7 (2019).
[3] T. Billoud, Total Ionizing Dose and Minimum Ionizing Particle fluence measurements in ATLAS using Timepix detectors and comparison with GEANT4 simulations, ATL-COM-GEN-2019-10, https://cds.cern.ch/record/2693024
[4] The ATLAS Collaboration, The Pythia 8 A3 tune description of ATLAS minimum bias and inelastic measurements incorporating the Donnachie-Landshoff diffractive model, ATL-PHYS-PUB-2016-017, https://cds.cern.ch/record/2206965
[5] The ATLAS Collaboration, Interactive web pages for radiation environment exploration of ATLAS, ATL-SOFT-PUB-2020-003, https://cds.cern.ch/record/2742378
[6] A. Trkov et al., IRDFF-II: A New Neutron Metrology Library, Nuclear Data Sheets, Volume 163, ISSN 0090-3752 (2020)
| Map of material density in the ATLAS cavern for Run 2. This illustrates the ATLAS detector geometry used in the following Geant4 simulations, with the same axis ranges. |
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| Map of Geant4-simulated charged particle fluences (G4) normalized to an integrated luminosity of 1 fb-1 and comparison with Timepix measurement at different locations in the ATLAS cavern for Run 2 (proton-proton collisions at √s = 13 TeV). The Timepix signal (TPX) is obtained using an exclusive approach, where the Geant4-simulated background is subtracted from the raw Timepix measurement (for TPX08, the predicted background is larger than the measurement). The simulation is performed using Geant4, the A3 Pythia8 tune and the Shielding physics list, for 50k events with a 78.42 mb cross-section. Overlaid are material density contour lines highlighting the boundaries of the geometry. The fluence map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. The uncertainties are a quadrature sum of contributions from measurement (statistical, detector position, detection efficiency) and simulation (statistical). Minbias related generator variations and G4 physics list changes are not included in the systematics. |
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| Map of Geant4-simulated charged particle fluences (G4) normalized to an integrated luminosity of 1 fb-1 and comparison with Timepix measurement at different locations in the ATLAS cavern for Run 2 (proton-proton collisions at √s = 13 TeV). The Timepix signal (TPX) is obtained using an inclusive approach, where the Geant4-simulated background is added to the convolution of Geant4- simulated fluences and Timepix efficiencies as a function of energy. The map is efficiency weighted, includes the gamma background, and is normalized to the effective exclusive fluences. The simulation is performed using Geant4, the A3 Pythia8 tune and the Shielding physics list, for 50k events with a 78.42 mb cross-section. Overlaid are material density contour lines highlighting the boundaries of the geometry. The fluence map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. The uncertainties are a quadrature sum of contributions from measurement (statistical, detector position, detection efficiency) and simulation (statistical). Minbias related generator variations and G4 physics list changes are not included in the systematics. |
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| Map of Geant4-simulated total ionizing dose (G4) normalized to an integrated luminosity of 1 fb-1 and comparison with Timepix measurement (TPX) at different locations in the ATLAS cavern for Run 2 (proton-proton collisions at √s = 13 TeV). The simulation is performed using Geant4, the A3 Pythia8 tune and the Shielding physics list, for 50k events with a 78.42 mb cross-section. Overlaid are material density contour lines highlighting the boundaries of the geometry. The dose map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. The uncertainties are a quadrature sum of contributions from measurement (statistical, detector position, internal consistency) and simulation (statistical). Minbias related generator variations and G4 physics list changes are not included in the systematics. |
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| Map of Geant4-simulated thermal neutron fluences (G4) normalized to an integrated luminosity of 1 fb-1 and comparison with Timepix measurement (TPX) at different locations in the ATLAS cavern for Run 2 (proton-proton collisions at √s = 13 TeV). The simulation is performed using Geant4, the A3 Pythia8 tune and the Shielding physics list, for 50k events with a 78.42 mb cross-section, and for a temperature of 20°C. Overlaid are material density contour lines highlighting the boundaries of the geometry. The fluence map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. The uncertainties are a quadrature sum of contributions from measurement (statistical, detector position, internal consistency) and simulation (statistical). Minbias related generator variations and G4 physics list changes are not included in the systematics. |
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Radmons (March 2021)
Total Ionizing Dose (TID) and 1 MeV equivalent neutron fluences are measured with RadFETs and diodes, respectively. These are located at 14 locations in the ATLAS ID and at 38 locations in calorimeters and muon detectors. In the Inner Detector radiation monitors are installed on the pixel support tube, on the ID end plate and on the cryostat wall. In LAr and Tile calorimeters monitors are installed near readout electronics and power supplies. Monitors are installed also on the Big Wheel and the Small Wheel of the muon detector. Response from radiation sensors increases with total integrated dose and fluence. Sensors are read out approximately once per hour and results are stored in the DCS database. A set of graphs show doses and fluences at various locations as measured by the radiation sensors as the function of time during Run 2. Measurements are compared with doses and fluences predicted by Fluka and Geant4 simulation of radiation background, scaled with measured integrated luminosity. Summary plots show measured doses and fluences per unit of integrated luminosity and comparison with simulation. In run 2 the total delivered luminosity is estimated to 160 ± 3 fb-1. This is slightly higher than the normally reported luminosity delivered in stable beams because for radiation exposure also the collisions outside of stable beam conditions have to be accounted for. Simulation results are from a dataset of 50000 events generated by Pythia 8 with minimum bias tune A3 [3] and an assumed inelastic cross section of 78.42 mb at √s=13 TeV. The events were processed with FLUKA 2011 or Geant4 [1,2] with the shielding physics list. A description of the ATLAS FLUKA simulation framework can be found in [4] and information about specifics of Geant4 based simulation in [5]. The geo tag for the Geant4 results is ATLAS-R2-2016-01-02-00. The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with the event generator, Geant4/FLUKA physics models, geometry description accuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The present estimate for the combined uncertainty from these sources is 50% in the ID volume, but assumed larger in the calorimeter and muon detector regions. [1]GEANT4 Collaboration, GEANT4: a simulation toolkit, Nucl. Instrum. Meth. A 506 (2003) 250.[2] ATLAS Collaboration, The ATLAS Simulation Infrastructure, Eur. Phys. J. C 70 (2010) 823, arXiv: arXiv:1005.4568 [physics.ins-det].
[3] ATLAS Collaboration, A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model, ATL-PHYS-PUB-2016-017, https://cds.cern.ch/record/2206965
[4] S. Baranov et al., Estimation of Radiation Background, Impact on Detectors, Activation and Shielding Optimization in ATLAS, (2005), url: https://cds.cern.ch/record/814823
. [5] ATLAS Collaboration, Interactive web pages for radiation environment exploration of ATLAS, ATL-SOFT-PUB-2020-003, CERN, (2020), url: http://cds.cern.ch/record/2742378/
| Summary of measurements and simulations of TID (left) and 1 MeV neutron equivalent fluences (right) per unit of integrated luminosity in the Inner Detector during Run 2. Measurements are averages from sensors at same (r, z) but at different azimuth angles. Error bars include variation of dose/integrated_luminosity ratios during run 2, variations between sensors and 20% uncertainties of calibration. TID is measured with REM 0.13 µm RadFETs. Neutron equivalent fluence is measured with two types of sensors at each location: BPW34 diodes (forward bias) and epitaxial diodes (reverse bias). In run 2 delivered luminosity contributing to radiation dozes is estimated to 160 fb-1 ± 3 fb-1. Error bars on simulation points include the statistical uncertainty and the position uncertainty of radiation monitors. The latter has been estimated from the variation of the predicted levels within r: ± 1 cm (± 2 cm Fluka) , z: ± 2 cm on PST, r:± 2 cm at r = 54 cm and r:± 4 cm at r = 80 cm , z: ± 2 cm on the ID End Plate and r: ± 2 cm, z: ± 4 cm on the cryostat wall. The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description accuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The present estimate for the combined uncertainty from these sources is 50% for both radiation quantities in the ID region. |
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| Summary of measurements and simulations of TID (left) and 1 MeV equivalent fluences (right) per unit of integrated luminosity in LAr and Tile calorimeters and in muon detector for run 2. Measurements are averages from sensors at same (r, z) but at different azimuth angles. Error bars include variation of dose/integrated_luminosity ratios during run 2, variations between sensors and calibration uncertainties. The total delivered luminosity in run 2 is estimated to 160 ± 3 fb-1. Error bars on simulation points include the statistical uncertainty and the position uncertainty of radiation monitors. The latter has been estimated from the variation of the predicted levels within r ± 10 cm and z ± 10 cm around the nominal monitor position. For tight regions deviations from the ± 10 cm rule are possible to stay away from shielding. The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in relevant sections in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description accuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The large differences between measurements and simulations in calorimeter regions is where the material distribution is particularly complex, with strong variations in azimuth, and this is likely to be oversimplified in the simulations. |
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| TID (left) and 1 MeV eq. neutron fluence (right) measured with radiation monitors in the Muon detector during run 2. Doses are measured with LAAS RadFETs (1.6 µm thick oxide) and fluences are measured with high sensitivity PiN diodes (CMRP) under forward bias. Sensors are installed on Small Wheels at r ~ 2.1 m and z ~ 6.9 m and on Big Wheels at r ~ 1.8 m and z ~ 13 m at four azimuthal angles (0,90,180 and 270) on sides A and C. On Small Wheels 7 out of 8 and on Big Wheels 3 out of 8 sensors were operating during run 2. Points with error bars represent measured values: points are averages from sensors at same r and z and error bars are calculated as E = √(σ2 + (σcal)2) , where σ is the standard deviation of measurements and σcal = 0.2∙D is the 20% accuracy of calibration. Only one point for every ~ 7 days is shown. Hatched bands show Geant4 simulation of doses and fluences at monitoring locations. Centres of bands are calculated as D = Lint ∙ Dnorm where Lint is the integrated luminosity and Dnorm is the dose/fluence per unit of luminosity obtained from simulation. Widths of the bands represent statistical uncertainty of simulation and uncertainty of radiation monitor position. The latter has been estimated from the variation of the predicted levels around the nominal monitor positions. For the Small Wheel (red) simulation values are from one 4 cm x 4 cm bin and for the Big Wheel (blue) from two 10 cm x 10 cm bins. Different simulation volumes were used where necessary to avoid shielding material. The total delivered luminosity in run 2 is estimated to 160 ± 3 fb-1. The simulations are based on 3D models but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description accuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. |
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| Fluence (1 MeV neutron equivalent) measured with BPW34 diodes from bias voltage at 1 mA forward current on Pixel Support Tube. Sensors are located at r = 23 cm and z = 90 cm at 4 different angles φ (0° and 180° on side C and 90° and 270° on side A). Red points represents measured values: points are averages from 4 sensors on PST and error bars are calculated as E = √(σ2 + (σcal)2) , where σ is the standard deviation of measurements from the four sensors and σcal = 0.2 ∙ Ф is the 20% accuracy of calibration. Only one point for every ~ 7 days is sown. Black bands show Geant4 (left) and Fluka (right) simulation of fluences at r and z coordinates of monitors scaled by integrated luminosity. Fluence (centre of the band) is calculated as Ф = Lint ∙ Фnorm where Lint is the integrated luminosity and Фnorm is the fluence per unit of luminosity obtained from simulation. Width of the band represents standard deviation of Фnorm values in intervals of coordinates: r = 23 cm (± 1 cm in Geant4, ± 2 cm in Fluka) and z = 90 cm ± 2 cm and the luminosity uncertainty. The total delivered luminosity in run 2 is estimated to 160 ± 3 fb-1 . The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description inaccuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The present estimate for the combined uncertainty from these sources for fluence estimates in the ID is 50%. |
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IBL Run 2 (April 2018)
Fluence-per-luminosity conversion factors extracted from leakage current fits as a function of distance along the IBL stave, compared with Pythia 8 + FLUKA 2011 and Pythia 8 + Geant 4 [0,1]. The Hamburg model [2] is used to fit the leakage current data, with the Fluence-per-luminosity conversion factor as one of the fit parameters:
Ileak = (Φ / Lint) x V x Σi=1n Lint,i x [α Iexp(-Σj=in tj/τ(Tj)) + α0* - βlog(Σj=in Θ(Tj) x tj / t0)]
where V is the sensor volume, Φ is the fluence, Lint is the integrated luminosity, t is time, T is temperature and the sum is over all time periods i. The values for the various parameters can be found in [2] and Φ/Lint is fit to the data. The error bars from the leakage current extraction are dominated by a conservative 10% uncertainty, accounting for the variation in the bias voltage at full depletion. Uncertainties due to the annealing model (0.1%) and data fit (0.5%) are subdominant. Note that the uncertainty in the parameters of the Hamburg annealing model are about 5% [2], but the quoted uncertainty is the impact of those uncertainties on the extracted value of Φ/Lint.
The Pythia 8 simulation uses either the A2 minimum bias tune [3], or the A3 tune [4]. A description of the ATLAS FLUKA simulation framework can be found in [5]. The ATLAS detector geometry models are not identical between Geant 4 and FLUKA - the former uses the full geometry model employed by the standard ATLAS Monte Carlo production system [1] while the latter uses a simplified standalone geometry. The predictions are mirrored for +/- |z|, so there is symmetry by construction. Only Monte Carlo statistical uncertainties are shown for the simulation predictions. Due to the more complex geometry used by Geant 4, the statistical uncertainties are enhanced (from the tilt of the IBL staves in φ); the FLUKA simulation also uses a factor of 5 more events than the Geant4 prediction.
[0] GEANT4 Collaboration, GEANT4: a simulation toolkit, Nucl. Instrum. Meth. A 506 (2003) 250.
[1] ATLAS Collaboration, The ATLAS Simulation Infrastructure, Eur. Phys. J. C 70 (2010) 823, arXiv: arXiv:1005.4568 [physics.ins-det].
[2] See M. Moll, Radiation damage in silicon particle detectors: Microscopic defects and macroscopic properties, PhD thesis: Hamburg U., 1999 and references therein.
[3] ATLAS Collaboration, Summary of ATLAS Pythia 8 Tunes, ATL-PHYS-PUB-2012-003, https://cds.cern.ch/record/1474107
[4] ATLAS Collaboration, A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model, ATL-PHYS-PUB-2016-017, https://cds.cern.ch/record/2206965
[5] S. Baranov et al., Estimation of Radiation Background, Impact on Detectors, Activation and Shielding Optimization in ATLAS, (2005), url: https://cds.cern.ch/record/814823.
| This comparison includes Pythia 8 (ATLAS A3 tune) + FLUKA or Geant 4 predictions. The right axis displays the relative reduction in the leakage current extraction in data as a function of z, with 100% at z=0. |
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| This comparison includes the Pythia 8 A2 and A3 ATLAS tunes using the FLUKA transport simulation as well as A3 + Geant 4 predictions. In the Geant 4 simulations, the results for protons, pions and neutrons are compared with the contribution from all particles, i.e. including also the damage from kaons and electrons, as in FLUKA. The right axis displays the relative reduction in the leakage current extraction in data as a function of z, with 100% at z=0. |
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Inner Detector Radmons (April 2018)
| Plots show total ionizing dose measured with REM radfets with 0.13 um oxide thickness. The colour bands represent measured values: centres of bands are averages of values from sensors at certain type of location (at same r and z, see slides 1 and 2). The width of the band w is calculated as w = √(σ2 + (σcal)2) , where σ is the standard deviation and σcal = 0.2*D describes the 20% accuracy of calibration. Dotted lines are PYTHIA 8 + FLUKA predicted doses: Dose = Integrated_luminosity * dose_factor, where the dose factor (in Gy/fb-1) is taken from the ATLAS Radiation Simulation Working Group. |
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| Plots show 1 MeV equivalent neutron fluences measured with BPW34 diodes (forward bias). The colour bands represent measured values: centres of bands are averages of values from sensors at certain type of location (at same r and z, see slides 1 and 2). The width of the band w is calculated as w = √(σ2 + (σcal)2) , where σ is the standard deviation and σcal = 0.2*D is the 20% accuracy of calibration. Dotted lines are PYTHIA8 + FLUKA predicted fluences: Fluence = Integrated_luminosity * fluence_factor The fluence_factor (in n/cm2/fb-1 ) is calculated from simulation of 49900 events for 13 TeV and obtained from the ATLAS Radiation Simulation Working Group. |
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FLUKA Simulations:
HGTD results (Dec 2019)
The following set of plots from FLUKA simulations shows the Silicon 1MeV neutron equivalent fuence (Si1MeVneq), the total dose and the hadron fuence above 20MeV in the inner (z = 343.5 cm) and the outer (z = 347.9 cm) silicon layer of the HGTD detector. The results correspond to the ATLAS Fluka 3.1q7 geometry layout which includes the ITk geometry version Step 3.1 and the optimised moderator design between the endcap and the HGTD. The latter consists of a 50 mm BPE layer at r < 90 cm, continued with a 20 mm thick layer to the outer radius of the endcap. Proton-proton events at √s = 14 TeV were generated using Pythia 8 with the A2 tune. All results are scaled to the HL-LHC target integrated luminosity of 4000 fb-1 assuming an inelastic cross section of 80mb.| Si1MeVneq fluence in the inner (open blue circles) and outer (red circles) silicon detector layers of the HGTD from r = 120mm to r = 700mm. The results correspond to the ATLAS FLUKA 3.1q7 geometry layout which includes the ITk geometry version Step 3.1 and the optimised moderator design between the endcap and the HGTD. The latter consists of a 50 mm BPE layer at r < 90cm, continued with a 20 mm thick layer to the outer radius of the endcap. Proton-proton events at √s = 14 TeV were generated using PYTHIA8 with the A2 tune. All results are scaled to the HL-LHC target integrated luminosity of 4000 fb-1, assuming an inelastic cross section of 80mb. The pseudorapidity (η) range shown on the top of each plot corresponds to the outer layer. |
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| Total dose in the inner (open blue circles) and outer (red circles) silicon detector layers of the HGTD from r = 120mm to r = 700mm. The results correspond to the ATLAS FLUKA 3.1q7 geometry layout which includes the ITk geometry version Step 3.1 and the optimised moderator design between the endcap and the HGTD. The latter consists of a 50 mm BPE layer at r < 90cm, continued with a 20 mm thick layer to the outer radius of the endcap. All results are scaled to the HL-LHC target integrated luminosity of 4000 fb-1 assuming an inelastic cross section of 80mb. The pseudorapidity (η) range shown on the top of each plot corresponds to the outer layer. |
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| Hadron fluence above 20MeV in the inner (open blue circles) and outer (red circles) silicon detector layers of the HGTD from r = 120mm to r = 700mm. The results correspond to the ATLAS FLUKA 3.1q7 geometry layout which includes the ITk geometry version Step 3.1 and the optimised moderator design between the endcap and the HGTD. The latter consists of a 50 mm BPE layer at r < 90cm, continued with a 20 mm thick layer to the outer radius of the endcap. All results are scaled to the HL-LHC target integrated luminosity of 4000 fb-1 assuming an inelastic cross section of 80mb. The pseudorapidity (η) range shown on the top of each plot corresponds to the outer layer. |
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| Si1MeVneq fluence only from neutrons (red circles) and Si1MeVneq fluence from particles other than neutrons (open blue circles) for the outer silicon layer of the HGTD detector from r = 120mm to r = 700mm. The results correspond to the latest ATLAS FLUKA geometry layout which includes the ITk geometry version Step 3.1 and the optimised moderator design between the endcap and the HGTD. The latter consists of a 50 mm BPE layer at r < 90cm, continued with a 20 mm thick layer to the outer radius of the endcap. All results are scaled to the HL-LHC target integrated luminosity of 4000 fb-1 assuming an inelastic cross section of 80mb. The pseudorapidity (η) range shown on the top of each plot corresponds to the outer layer. |
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Phase II ITk Inclined Duals (April 2018)
These plots shows the results of FLUKA [1] simulations of radiation fluence and dose in the ATLAS Phase-2 Upgrade Inner Tracker (ITk) regions. The ITk layout simulated is the inclined duals layout as described in the Pixel TDR [2]. The minimum-bias pp collisions are simulated with ATLAS-tuned Pythia8 [3] at 14 TeV centre of mass energy and predicted inelastic cross section of 79.3 mb. The tune used is the A2 tune [4]. The radiation environment is characterized by three quantities:1) 1 MeV equivalent neutron fluence, i.e., the fluence of 1 MeV neutrons that would cause the same amount of displacement damage in silicon as the actual mixed particle spectrum. To obtain this quantity each fluence component is weighted by a particle- and energy-dependent damage factor which expresses the damage relative to 1 MeV neutrons. For the latter the Non Ionising Energy Loss (NIEL) in silicon is defined as 95 MeV mb.
2) Total Ionising Dose (TID), defined as the energy deposited by ionisation divided by the mass of the material where the energy is deposited.
3) Fluence of hadrons with E > 20 MeV, which can be used to estimate the rate of Single Event Effects (SEE) in electronics components by comparing with the SEE rate of a given device in a beam test. [1] T.T. Bohlen et al., The FLUKA Code: Developments and Challenges for High Energy and Medical Applications, Nuclear Data Sheets 120, 211-214 (2014)
[2] The ATLAS Collaboration, Technical Design Report for the ATLAS Inner Tracker Pixel Detector, ATL-COM-ITK-2018-019
[3] T. Sjöstrand, S. Mrenna and P. Skands, JHEP05 (2006) 026, Comput. Phys. Comm. 178 (2008) 852
[4] The ATLAS Collaboration, Summary of ATLAS Pythia 8 tunes, ATL-PHYS-PUB-2012-003
 png pdf 1 MeV neutron equivalent fluence per 4000 fb-1 of integrated luminosity in the ATLAS Inner Tracker. The minimum-bias pp events are simulated with Pythia8 using A2 tune at 14 TeV centre of mass energy and a predicted inelastic cross section of 79.3 mb. Particle tracking and interactions with material are simulated with the FLUKA 2011 code using the geometry description of inclined duals layout of the ITk. |
 png pdf Total ionising dose per 4000 fb-1 of integrated luminosity in the ATLAS Inner Tracker. The minimum-bias pp events are simulated with Pythia8 using A2 tune at 14 TeV centre of mass energy and a predicted inelastic cross section of 79.3 mb. Particle tracking and interactions with material are simulated with the FLUKA 2011 code using the ITk inclined duals layout geometry description of the ATLAS detector. |
 png pdf Fluence of hadrons with E>20 MeV per cm2 per second in the ATLAS Inner Tracker assuming an instantaneous luminosity of 7.5×1034cm-2s-1. The minimum-bias pp events are simulated with Pythia8 using A2 tune at 14 TeV centre of mass energy and a predicted inelastic cross section of 79.3 mb. Particle tracking and interactions with material are simulated with the FLUKA 2011 code using the ITk inclined duals layout geometry description of the ATLAS detector. |
Phase II Upgrade (Mar 2018)
These plots show the results of FLUKA simulations of the 1 MeV neutron equivalent damage in silicon for the ITk region of the ATLAS Phase II upgrade.The purpose of this set of plots is to illustrate that in inner regions of the ITk, notably in the Pixel detector, the silicon bulk damage is not dominated by neutrons but by other particles. These are mostly pions and other charged hadrons, with minor contribution from neutral hadrons, electrons, positrons, muons and photons.
All particle fluences have been weighted with the corresponding particle- and energy-dependent hardness factors in silicon. The fluences are expressed in terms of silicon 1 MeV equivalent fluence, i.e. the fluence of mono-energetic 1 MeV neutrons (defined to have a non-ionising energy loss (NIEL) of 95 MeV mb) that would cause the same amount of NIEL in silicon as the actual radiation field. Where relevant, the plots are normalised to an integrated luminosity of 4000 fb−1 of pp collisions. The pp collisions are simulated with Pythia8 minimum bias events at 14 TeV centre of mass energy, with an assumed inelastic cross section of 80 mb. The radiation levels are assumed to be symmetric in azimuth and about z = 0.
 png eps Silicon 1MeV equivalent fluence as a function of radius at the center of the ITk, subdivided into the component from neutrons and other particles. The values are averaged in a slice |z|=0–4 cm |
 png eps Silicon 1MeV equivalent fluence as a function of radius at the end of the ITk, subdivided into the component from neutrons and other particles. The values are averaged in a slice |z|= 296–300 cm. |
 png pdf Neutron fraction in the silicon 1 MeV neutron equivalent fluence in the Phase II Pixel detector. |
 png pdf Silicon 1 MeV neutron equivalent fluence, as a function of z, in various layers of the Phase II Pixel detector. The upper plot shows the fluences separately for neutrons and all other particles, while the lower plot shows the fraction at which neutrons contribute to the total. |
Run 2 Inner Detector (Nov 2017)
| 1 MeV neutron equivalent fluence per fb-1 of integrated luminosity in the ATLAS inner detector. The minimum-bias pp events are simulated with ATLAS tuned Pythia8 at 13 TeV centre of mass energy and a predicted inelastic cross section of 78.4 mb. Particle tracking and interactions with material are simulated with the FLUKA 2011 code using the Run 2 geometry description of the ATLAS detector. |
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| Total ionising dose (Gy/fb-1) in the ATLAS inner detector. The minimum-bias pp events are simulated with ATLAS tuned Pythia8 at 13 TeV centre of mass energy and a predicted inelastic cross section of 78.4 mb. Particle tracking and interactions with material are simulated with the FLUKA 2011 code using the Run 2 geometry description of the ATLAS detector. |
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| Total fluence of hadrons with E > 20 MeV per cm2 per second assuming an instantaneous luminosity of 1034cm-2s-1. The minimum-bias pp events are simulated with ATLAS tuned Pythia8 at 13 TeV centre of mass energy and a predicted inelastic cross section of 78.4 mb. Particle tracking and interactions with material are simulated with the FLUKA 2011 code using the Run 2 geometry description of the ATLAS detector. |
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HGTD results (Oct 2016)
| Si1MeVneq fluence in the hottest spot of the outermost ITk Strip disk relative to the baseline without a HGTD. The values correspond to the hottest spot at the lowest edge of the out- ermost disk, defined as an annular ring between r = 38–44 cm and z = 296–300 cm. The horizontal line, showing the baseline configuration with 50mm moderator and no HGTD, is considered the target level for the shielding optimisation. The solid blue circles and the fit show the reduction as a function of the moderator thickness between the ITk and the HGTD. The slope of the fit is 0.285cm−1, which implies that 50mm of moderator should reduce the Si1MeVneq fluence by a factor of 4.2. The significant constant term, due to high energy hadrons, causes the real effect to be only a factor 1.4. The other symbols at 50 mm thickness correspond to configurations in which the HGTD is on the ITk side of the moderator. They differ only in terms of moderator thickness at r > 70 cm. |
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| Neutron spectra averaged over the fourth silicon layer of the HGTD from r = 110mm to r = 700 mm. The plain HGTD is not protected by a moderator while the optimised moderator layout includes a 50 mm BPE layer at r < 90 cm, continued with a 20 mm thick layer to the outer radius of the endcap. The spiky stuctures between 1 keV and 10 MeV are due to resonances. The uncertainties are of the order of 5 %. |
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| Si1MeVneq fluence in the first (open blue circles) and fourth (red circles) detector layers of the HGTD from r = 110 mm to r = 700mm. The results correspond to the optimised moderator design between the endcap and the HGTD that consists of a 50 mm BPE layer at r < 90 cm, continued with a 20 mm thick layer to the outer radius of the endcap. The pseudorapidity (η) range shown on the top of each plot corresponds to Layer-4 at a z-location of 345 cm. |
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| Total ionising dose in the first (open blue circles) and fourth (red circles) detector layers of the HGTD from r = 110 mm to r = 700mm. The results correspond to the optimised moderator design between the endcap and the HGTD that consists of a 50 mm BPE layer at r < 90 cm, continued with a 20 mm thick layer to the outer radius of the endcap. The pseudorapidity (η) range shown on the top of each plot corresponds to Layer-4 at a z-location of 345 cm. |
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| Hadron fluence above 20MeV in the first (open blue circles) and fourth (red circles) detector layers of the HGTD from r = 110 mm to r = 700mm. The results correspond to the optimised moderator design between the endcap and the HGTD that consists of a 50 mm BPE layer at r < 90 cm, continued with a 20 mm thick layer to the outer radius of the endcap. The pseudorapidity (η) range shown on the top of each plot corresponds to Layer-4 at a z-location of 345 cm. |
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HGTD results for the ECFA Upgrade workshop 2016
| Ionising dose in the readout chips of the HGTD layer closest to the ATLAS endcap calorimeter. The histograms represent the three different HGTD layouts that have been studied: the preshower option (black circles), with 3.5 mm thick borated polyethylene moderator layers from R=47 mm to R=284 mm, continued with tungsten plates of the same thickness from R=284 mm to R=700 mm, an option with the tungsten replaced by borated polyethylene (red triangles), giving a total of 10 mm moderator over the full radial range of the HGTD and an option with no moderator inside the detector (blue squares). While the presence of the tungsten plates increases the dose significantly in the radial range covered by these plates, the borated polyethylene has no influence on the ionising dose. The Z position of the HGTD as described in the FLUKA geometry is: Z=±[3461,3516] mm. |
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| Comparison of the non-ionising energy loss (NIEL) in the ITk region close to the endcap for three alternative HGTD layouts with respect to the baseline configuration without the HGTD, but 5 cm of borated polyethylene all over the calorimeter endcap face. The histograms represent the preshower option (black circles), with 3.5 mm thick borated polyethylene moderator layers from R=47mm to R=284mm, continued with tungsten plates of the same thickness from R=284 mm to R=700 mm, an option with the tungsten replaced by borated polyethylene (red triangles), giving a total of 10 mm moderator over the full radial range of the HGTD and an option with no moderator inside the detector (blue squares). From R=700 mm to R=800 mm a gap for service routing is left. In the simulations this region contains only air – the presence of cables is likely to reduce the fluence to some extent. The fourth histogram (green open squares) shows the baseline case with 5 cm moderator and no HGTD. Depending on the layout the NIEL in the ITk volume just next to the endcap increases, with respect to the baseline, by 40–140% in the radial range covered by the HGTD. The Z position of the HGTD as described in the FLUKA geometry is: Z=±[3461,3516] mm. |
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Athena G4 Simulations
Radiation maps for Run 2 (October 2020)
Radiation Maps from GEANT4 simulations of the ATLAS detector in a configuration for Run-2 for proton-proton collisions at a centre-of-mass energy √s = 13 TeV. All these simulations are based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. The maps are published in ATL-SOFT-PUB-2020-003, supersede the ones from October 2019 and benefit from several improvements in the detector description used in the simulations. Interactive inspection is possible for the full cavern here: WebRadMaps_Full_R2_public.html and the calorimeter/inner detector region here: WebRadMaps_Zoom_R2_public.html.
| The “pseudo-density” values, calculated from the ratio of the total deposited ionisation energy density in a given r-|z|-bin and the total ionising dose in the same bin. Pseudo-density reflects the actual density in homogenous regions and a (biased) bin-average in volumes with material mixes. The values correspond to a GEANT4 simulation with the “Shielding” physics list of the ATLAS detector typical for Run-2. Bin-averages are shown on a colour scale for Δr × Δ|z| = 10 × 10 cm2 in the full detector region, with |z| < 24 m and r < 12 m. |
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| The “pseudo-density” values, calculated from the ratio of the total deposited ionisation energy density in a given r-|z|-bin and the total ionising dose in the same bin. Pseudo-density reflects the actual density in homogenous regions and a (biased) bin-average in volumes with material mixes. The values correspond to a GEANT4 simulation with the “Shielding” physics list of the ATLAS detector typical for Run-2. Bin-averages are shown on a colour scale for Δr × Δ|z| = 4 × 4 cm2 in the calorimeter region, with |z| < 9.6 m and r < 4.8 m. |
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| Total ionising dose from a GEANT4 simulation of the ATLAS detector typical for Run-2 with the “Shielding” physics list at √s = 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a colour scale for Δr × Δ|z| = 10 × 10 cm2 in the full detector region, with |z| < 24 m and r < 12 m. Overlaid are material density contour lines in grey, highlighting the boundaries of the geometry. The dose map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines |
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| Total ionising dose from a GEANT4 simulation of the ATLAS detector typical for Run-2 with the “Shielding” physics list at √s = 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a colour scale for Δr × Δ|z| = 4 × 4 cm2 in the calorimeter region, with |z| < 9.6 m and r < 4.8 m. Overlaid are material density contour lines in grey, highlighting the boundaries of the geometry. The dose map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. |
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| 1 MeV neutron equivalent fluence in Silicon from a GEANT4 simulation of the ATLAS detector typical for Run-2 with the “Shielding” physics list at √s = 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a colour scale for Δr × Δ|z| = 10 × 10 cm2 in the full detector region, with |z| < 24 m and r < 12 m. Overlaid are material density contour lines in grey, highlighting the boundaries of the geometry. The fluence map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. |
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| 1 MeV neutron equivalent fluence in Silicon from a GEANT4 simulation of the ATLAS detector typical for Run-2 with the “Shielding” physics list at √s = 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a colour scale for Δr × Δ|z| = 4 × 4 cm2 in the calorimeter region, with |z| < 9.6 m and r < 4.8 m. Overlaid are material density contour lines in grey, highlighting the boundaries of the geometry. The fluence map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. |
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| Fluence of hadrons with E > 20 MeV from a GEANT4 simulation of the ATLAS detector typical for Run-2 with the “Shielding” physics list at √s = 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a colour scale for Δr × Δ|z| = 10 × 10 cm2 in the full detector region, with |z| < 24 m and r < 12 m. Overlaid are material density contour lines in grey, highlighting the boundaries of the geometry. The fluence map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. |
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| Fluence of hadrons with E > 20 MeV from a GEANT4 simulation of the ATLAS detector typical for Run-2 with the “Shielding” physics list at √s = 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a colour scale for Δr × Δ|z| = 4 × 4 cm2 in the calorimeter region, with |z| < 9.6 m and r < 4.8 m. Overlaid are material density contour lines in grey, highlighting the boundaries of the geometry. The fluence map is also overlaid with 3 white contours per decade - i.e. with a ratio of 2.15 between adjacent lines. |
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Radiation maps for Run 2 (October 2019)
Radiation Maps from GEANT4 simulations of the ATLAS detector in a configuration for Run-2 for proton-proton collisions at a centre-of-mass energy √s = 13 TeV. All these simulations are based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1.
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Average material density from GEANT4 simulations (Version 10.1 with the Shielding physics list) of the ATLAS detector and cavern in a configuration for Run-2. The values are calculated from the ratio of the total deposited ionisation energy density in a given r-|z|-bin (Δr × Δ|z| = 10 × 10 cm2) and the total ionisation dose in the same bin. They are reflecting the actual density in homogenous regions and a bin-average in volumes with material mixes. The simulation is based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV.
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Average material density from GEANT4 simulations (Version 10.1 with the Shielding physics list) of the calorimeter and inner detector regions of the ATLAS detector in a configuration for Run-2. The values are calculated from the ratio of the total deposited ionisation energy density in a given r-|z|-bin (Δr × Δ|z| = 4 × 4 cm2) and the total ionisation dose in the same bin. They are reflecting the actual density in homogenous regions and a bin-average in volumes with material mixes. The simulation is based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV.
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Total ionisation dose from GEANT4 simulations (Version 10.1 with the Shielding physics list) of the ATLAS detector and cavern in a configuration for Run-2. The simulation is based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a color scale for Δr × Δ|z| = 10 × 10 cm2. Overlaid are material density contour lines highlighting the boundaries of the geometry.
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Total ionisation dose from GEANT4 simulations (Version 10.1 with the Shielding physics list) of the calorimeter and inner detector regions of the ATLAS detector in a configuration for Run-2. The simulation is based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a color scale for Δr × Δ|z| = 4 × 4 cm2. Overlaid are material density contour lines highlighting the boundaries of the geometry.
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1 MeV neutron equivalent fluence in silicon from GEANT4 simulations (Version 10.1 with the Shielding physics list) of the ATLAS detector and cavern in a configuration for Run-2. The simulation is based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Particle fluxes are weighted with energy dependent damage factors for silicon relative to that of a neutron with 1 MeV kinetic energy. Weights for all particles are considered and taken from RD50 Collaboration, http://rd50.web.cern.ch/rd50/NIEL/default.html, Michael Moll, "Displacement Damage in Silicon Detectors for High Energy Physics'', IEEE Transactions on Nuclear Science 65, 1561 (2018). Bin-averages are shown on a color scale for Δr × Δ|z| = 10 × 10 cm2. Overlaid are material density contour lines highlighting the boundaries of the geometry.
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1 MeV neutron equivalent fluence in silicon from GEANT4 simulations (Version 10.1 with the Shielding physics list) of the calorimeter and inner detector regions of the ATLAS detector in a configuration for Run-2. The simulation is based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Particle fluxes are weighted with energy dependent damage factors for silicon relative to that of a neutron with 1 MeV kinetic energy. Weights for all particles are considered and taken from RD50 Collaboration, http://rd50.web.cern.ch/rd50/NIEL/default.html, Michael Moll, "Displacement Damage in Silicon Detectors for High Energy Physics'', IEEE Transactions on Nuclear Science 65, 1561 (2018). Bin-averages are shown on a color scale for Δr × Δ|z| = 4 × 4 cm2. Overlaid are material density contour lines highlighting the boundaries of the geometry.
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Fluence of hadrons with E > 20 MeV from GEANT4 simulations (Version 10.1 with the Shielding physics list) of the ATLAS detector and cavern in a configuration for Run-2. The simulation is based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a color scale for Δr × Δ|z| = 10 × 10 cm2. Overlaid are material density contour lines highlighting the boundaries of the geometry.
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Fluence of hadrons with E > 20 MeV from GEANT4 simulations (Version 10.1 with the Shielding physics list) of the calorimeter and inner detector regions of the ATLAS detector in a configuration for Run-2. The simulation is based on 50k inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model'', ATL-PHYS-PUB-2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1. Bin-averages are shown on a color scale for Δr × Δ|z| = 4 × 4 cm2. Overlaid are material density contour lines highlighting the boundaries of the geometry.
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Run 2 Tile Calorimeter studies (May 2018)
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Total ionisation doses from GEANT4 simulations of the ATLAS detector in the Tile calorimeter (see ATLAS Collaboration, “Mechanical construction and installation of the ATLAS tile calorimeter”, JINST 8, T11001 (2013)) region are presented for proton- proton collisions at a centre-of-mass energy of √s = 13 TeV for a) scintillating tiles, b) steel absorbers and c) all materials as average dose from the sum of individual doses. Scintillators and steel absorbers account for about 93% of the total volume of the Tile calorimeter. The remaining 7% are filled mostly with air and to a minor fraction with glue. The simulation is based on 50000 inelastic proton-proton events generated with PYTHIA 8 using the A3 tune (see ATLAS Collaboration, “A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model”, ATL-PHYS-PUB- 2016-017 (2016), https://cds.cern.ch/record/2206965) and the NNPDF23LO PDF at a centre-of-mass energy of 13 TeV normalised to a cross section of σinel = 78.42 mb and an integrated luminosity of L = 1 fb-1.
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Phase II Upgrade (Mar 2018)
| Average material density from GEANT4 simulations of the ATLAS detector in a configuration for the Phase-II upgrade of the LHC. The values are calculated from the ratio of the total deposited ionisation energy density in a given r − |z|-bin (∆r × ∆|z| = 4 × 4 cm2) and the total ionisation dose in the same bin. They are reflecting the actual density in homogenous regions and a bin-average in volumes with material mixes. The simulation is based on 49150 inelastic proton-proton events generated with PYTHIA 8 using the A2 tune (see ATLAS-PHYS-PUB-2012-003) and the MSTW2008LO PDF at a centre-of-mass energy of 14 TeV. |
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| Total ionisation dose from GEANT4 simulations of the ATLAS detector in a configuration for the Phase-II upgrade of the LHC. The simulation is based on 49150 inelastic proton-proton events generated with PYTHIA 8 using the A2 tune (see ATLAS-PHYS-PUB-2012-003) and the MSTW2008LO PDF at a centre-of-mass energy of 14 TeV normalised to a cross section of σinel = 80 mb and an integrated luminosity of L = 4000 fb-1. Bin-averages are shown on a color scale for ∆r × ∆|z| = 4 × 4 cm2. Overlaid are material density contour lines highlighting the boundaries of the geometry. |
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1 MeV neutron equivalent fluence in silicon from GEANT4 simulations of the ATLAS detector in a configuration for the Phase-II upgrade of the LHC. The simulation is based on 49150 inelastic proton-proton events generated with PYTHIA 8 using the A2 tune (see ATLAS-PHYS-PUB-2012-003) and the MSTW2008LO PDF at a centre-of-mass energy of 14 TeV normalised to a cross section of σinel = 80 mb and an integrated luminosity of L = 4000 fb-1. Particle fluxes are weighted with energy dependent damage factors for silicon relative to that of a neutron with 1 MeV kinetic energy. Weights for neutrons, protons and pions are considered and taken from RD50 Collaboration, http://rd50.web.cern.ch/rd50/NIEL/default.html, Michael Moll, “Displacement Damage in Silicon Detectors for High Energy Physics”, accepted for publication in IEEE TNS (2018). Bin-averages are shown on a color scale for ∆r × ∆|z | = 4 × 4 cm2 . Overlaid are material density contour lines highlighting the boundaries of the geometry.
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| Fluence of hadrons (*) with E > 20 MeV from GEANT4 simulations of the ATLAS detector in a configuration for the Phase-II upgrade of the LHC. The simulation is based on 49150 inelastic proton-proton events generated with PYTHIA 8 using the A2 tune (see ATLAS-PHYS-PUB-2012-003) and the MSTW2008LO PDF at a centre-of-mass energy of 14 TeV normalised to a cross section of σinel = 80 mb and an integrated luminosity of L = 4000fb-1. Bin-averages are shown on a color scale for ∆r × ∆|z| = 4 × 4 cm2. Overlaid are material density contour lines highlighting the boundaries of the geometry. (*Only protons, neutrons and charged pions are considered). |
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GCalor Simulations
Phase II Upgrade (Nov 2017)
| Displacement damage in silicon for an integrated luminosity of 4000 fb-1, expressed as the equivalent fluence of 1 MeV neutrons. The minimum-bias pp events are simulated with Pythia8 at 14TeV centre of mass energy assuming an inelastic cross section of 80 mb. Particle tracking and interactions with material are simulated with the GEANT3/GCALOR code using the latest geometry description of the Phase II ATLAS detector. The geometry model is symmetric in azimuth and about z = 0. |
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| Total ionising dose in Gy/4000 fb-1 in the tracking and calorimeter regions of the Phase II ATLAS detector. The minimum-bias pp events are simulated with Pythia8 at 14 TeV centre of mass energy assuming an inelastic cross section of 80 mb. Particle tracking and interactions with material are simulated with the GEANT3/GCALOR code. The geometry model is symmetric in azimuth and about z = 0. |
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| Total fluence of hadrons with E>20MeV per cm2 for an integrated luminosity of 4000 fb-1. The integrated fluence can be converted to the flux per second at a peak luminosity of 5 × 1034 cm2 by dividing by a factor of 8 × 107. The minimum-bias pp events are simulated with Pythia8 at 14 TeV centre of mass energy assuming an inelastic cross section of 80 mb. Particle tracking and interactions with material are simulated with the GEANT3/GCALOR code using the latest geometry description of the Phase II ATLAS detector. The geometry model is symmetric in azimuth and about z = 0. |
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Archived plots
Radmons (May 2019)
Total Ionizing Dose (TID) and 1 MeV equivalent neutron fluences are measured with RadFETs and diodes, respectively. These are located at 14 locations in the ATLAS ID and at 38 locations in calorimeters and muon detectors. In the Inner Detector radiation monitors are installed on the pixel support tube, on the ID end plate and on the cryostat wall. In LAr and Tile calorimeters monitors are installed near readout electronics and power supplies. Monitors are installed also on the Big Wheel and the Small Wheel of the muon detector. Response from radiation sensors increases with total integrated dose and fluence. Sensors are read out approximately once per hour and results are stored in the DCS database. A set of graphs show doses and fluences at various locations as measured by the radiation sensors as the function of time during Run 2. Measurements are compared with doses and fluences predicted by Fluka and Geant4 simulation of radiation background, scaled with measured integrated luminosity. Summary plots show measured doses and fluences per unit of integrated luminosity and comparison with simulation. In run 2 total the delivered luminosity is estimated to 160 ± 3 fb-1. This is slightly higher than the normally reported luminosity delivered in stable beams because for radiation exposure also the collisions outside of stable beam conditions have to be accounted for. Simulation results are from a dataset of 50000 events generated by Pythia 8 with minimum bias tune A3 [1] and an assumed inelastic cross section of 78.42 mb at √s=13 TeV. The events were processed with FLUKA 2011 [2,3] or Geant 4 [4,5] with the shielding physics list. A description of the ATLAS FLUKA simulation framework can be found in [6]. The geo tag for the Geant4 results is ATLAS-R2-2016-01-01-00. The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with the event generator, Geant4/FLUKA physics models, geometry description accuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The present estimate for the combined uncertainty from these sources is 50% in the ID volume, but assumed larger in the calorimeter and muon detector regions. [1] ATLAS Collaboration, "A study of the Pythia 8 description of ATLAS minimum bias measurements with the Donnachie-Landshoff diffractive model", ATL-PHYS-PUB-2016-017, https://cds.cern.ch/record/2206965[2] "The FLUKA Code: Developments and Challenges for High Energy and Medical Applications", T.T. Bohlen, F. Cerutti, M.P.W. Chin, A. Fasso`, A. Ferrari, P.G. Ortega, A. Mairani, P.R. Sala, G. Smirnov, and V. Vlachoudis, Nuclear Data Sheets 120, 211-214 (2014)
[3] "FLUKA: a multi-particle transport code", A. Ferrari, P.R. Sala, A. Fasso`, and J. Ranft, CERN-2005-10 (2005), INFN/TC_05/11, SLAC-R-773
[4] GEANT4 Collaboration, GEANT4: a simulation toolkit, Nucl. Instrum. Meth. A 506 (2003) 250.
[5] ATLAS Collaboration, The ATLAS Simulation Infrastructure, Eur. Phys. J. C 70 (2010) 823, arXiv: arXiv:1005.4568 [physics.ins-det].
[6] S. Baranov et al., Estimation of Radiation Background, Impact on Detectors, Activation and Shielding Optimization in ATLAS, (2005), url: https://cds.cern.ch/record/814823
.| Total ionizing dose measured with REM RadFETs (0.13 um oxide thickness) on the Pixel Support Tube (PST) in the inner detector during run 2. The sensors are located at r = 23 cm and z = 90 cm at 4 different angles φ (0° and 180° on side C and 90° and 270° on side A). Red points represents measured values: points are averages from 3 sensors (one out of 4 failed) and error bars are calculated as E = √(σ2 + (σcal)2) , where σ is the standard deviation of measurements from 3 sensors and σcal = 0.2 *D is 20% accuracy of calibration. Only one point for every ~ 7 days is sown. Black bands show Geant4 (left) and Fluka (right) simulation of doses at r and z coordinates of monitors on PST scaled by integrated luminosity. Dose (centre of the band) is calculated as D = Lint ∙ Dnorm where Lint is the integrated luminosity and Dnorm is the dose per unit of luminosity obtained from simulation. The width of the band represents standard deviation of Dnorm values in intervals of coordinates: r = 23 cm ± 1 cm and z = 90 cm ± 4 cm and the luminosity uncertainty. The total delivered luminosity in run 2 is estimated to 160 ± 3 fb-1 . The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description inaccuracies. The present estimate for the combined uncertainty from these sources for dose estimates in the ID is 50%. |
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| Fluence (1 MeV neutron equivalent) measured with BPW34 diodes from bias voltage at 1 mA forward current on Pixel Support Tube. Sensors are located at r = 23 cm and z = 90 cm at 4 different angles φ (0° and 180° on side C and 90° and 270° on side A). Red points represents measured values: points are averages from 4 sensors on PST and error bars are calculated as E = √(σ2 + (σcal)2) , where σ is the standard deviation of measurements from the four sensors and σcal = 0.2 *D is the 20% accuracy of calibration. Only one point for every ~ 7 days is sown. Black bands show Geant4 (left) and Fluka (right) simulation of fluences at r and z coordinates of monitors scaled by integrated luminosity. Dose (centre of the band) is calculated as F = Lint ∙ Fnorm where Lint is the integrated luminosity and Fnorm is the fluence per unit of luminosity obtained from simulation. Width of the band represents standard deviation of Fnorm values in intervals of coordinates: r = 23 cm ± 1 cm and z = 90 cm ± 4 cm and the luminosity uncertainty. The total delivered luminosity in run 2 is estimated to 160 ± 3 fb-1 . The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description inaccuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The present estimate for the combined uncertainty from these sources for fluence estimates in the ID is 50%. |
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| Fluence (1 MeV neutron equivalent) measured from reverse current in 25 μm thick epitaxial diodes in the Inner Detector End Plate. On ID End Plate sensors are located at r = 54 cm and z = 345 cm at 4 different angles φ (105° and 285° on side C and 15° and 195° on side A). Blue points represents measured values: points are averages from 3 sensors (one of the 4 failed) and error bars are calculated as E = √(σ2 + (σcal)2) , where σ is the standard deviation of measurements from the three sensors and σcal = 0.2 *D is the 20% accuracy of calibration. Only one point for every ~ 7 days is sown. Black bands show Geant4 (left) and Fluka (right) simulation of fluences at r and z coordinates of monitors scaled by integrated luminosity. Dose (centre of the band) is calculated as F = Lint ∙ Fnorm where Lint is the integrated luminosity and Fnorm is the fluence per unit of luminosity obtained from simulation. Width of the band represents standard deviation of Fnorm values in intervals of coordinates: r = 54 cm ± 2 cm and z = 345 cm ± 3 cm and the luminosity uncertainty. The total delivered luminosity in run 2 is estimated to 160 fb-1 ± 3 fb-1 . The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description inaccuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The present estimate for the combined uncertainty from these sources for fluence estimates in the ID is 50%. |
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| Summary of measurements and simulations of TID (left) and 1 MeV neutron equivalent fluences (right) per unit of integrated luminosity in the Inner Detector during Run 2. Measurements are averages from sensors at same (r, z) but at different azimuth angles. Error bars include variation of dose/integrated_luminosity ratios during run 2, variations between sensors and 20% uncertainties of calibration. TID is measured with REM 0.13 um RadFETs. Neutron equivalent fluence is measured with two types of sensors at each location: BPW34 diodes (forward bias) and epitaxial diodes (reverse bias). In run 2 delivered luminosity contributing to radiation dozes is estimated to be 160 fb-1 ± 3 fb-1 . Error bars on simulation (Geant4 and Fluka) points are standard deviations of simulated doses and fluences per fb-1 in intervals of coordinatesaround monitoringlocation:r:±1cm,z:±4cmonPST, r:±2cm,z:±3cmontheIDEndPlateandr:±2cm,z:±4cmonthe cryostat wall. The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description inaccuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The present estimate for the combined uncertainty from these sources is 50% for both radiation quantities in the ID region. |
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| TID and 1 MeV eq. neutron fluence measured with radiation monitors in the Muon detector during run 2. Doses are measured with LAAS RadFETs (1.6 um thick oxide) and fluences are measured with high sensitivity PiN diodes (CMRP) under forward bias. Sensors are installed on Small Wheels at r ~ 2.1 m and z ~ 6.9 m and on Big Wheels at r ~ 2.1 m and z ~ 6.9 m at four azimuthal angles (0,90,180 and 270) on sides A and C. On Small Wheels 7 out of 8 and on Big Wheels 3 out of 8 sensors were operating during run 2. Points with error bars represent measured values: points are averages from sensors at same r and z and error bars are calculated as E = √(σ2 + (σcal)2) , where σ is the standard deviation of measurements and σcal = 0.2 *D is the 20% accuracy of calibration. Only one point for every ~ 7 days is shown. Hatched bands show Geant4 simulation of doses and fluences at monitoring locations. Dose (centre of the band) is calculated as D = Lint ∙ Dnorm where Lint is the integrated luminosity and Dnorm is the fluence per unit of luminosity obtained from simulation at r and z coordinates of monitors. Width of the band represents standard deviation of Dnorm values in ± 10 cm intervals of r and z coordinates around the monitoring location. The total delivered luminosity in run 2 is estimated to 160 ± 3 fb-1 . The simulations are based on a 3D model, but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4 physics models, geometry description inaccuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. |
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| Summary of measurements and simulations of TID (left) and 1 MeV equivalent fluences (right) per unit of integrated luminosity in LAr and Tile calorimeters and in muon detector for run 2. Measurements are averages from sensors at same (r, z) but at different azimuth angles. Error bars include variation of dose/integrated_luminosity ratios during run 2, variations between sensors and calibration uncertainties. The total delivered luminosity in run 2 is estimated to 160 ± 3 fb-1 . Error bars on simulation (Geant4 and Fluka) points are standard deviations of simulated doses and fluences per fb-1 in intervals of coordinates around monitoring location: r: ± 10 cm, z: ± 10 cm. The simulations are based on 3D models (simplified in case of FLUKA), but the radiation maps are averaged in azimuth. Not included in the simulated predictions are the systematic uncertainties associated with event generator, Geant4/FLUKA physics models, geometry description inaccuracies and the damage factors in deriving 1 MeV neutron equivalent fluences. The large TID difference observed in two of the LAr regions is where the material distribution is particularly complex, with strong variations in azimuth, and this is likely to be oversimplified in the simulations. |
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| Graph shows the increase of base current at 10 uA collector current in DMILL bipolar transistors on Pixel Support Tube in run 2. Points are average values from 8 sensors on PST (there are 2 transistor at each monitoring location). Error bars are calculated as E = √(σ2 + (σcal)2), where σ is the standard deviation of measurements from 8 sensors and σcal = 0.2* ΔIb is the 20% systematic uncertainty of measurement. Only one point for every ~ 7 days is shown. The same type of transistor is used in the input stage of the ABCD3TA chip, the readout chip of the Semiconductor Tracker (SCT). The rise of the base current is one of the causes for radiation induced increase of noise in the readout chip. The increase of the base current is the consequence of displacement damage in the base of the transistor. Equivalent fluence of 1 MeV neutrons is the quantity measuring the amount of displacement damage caused by energetic hadrons. In addition, in this particular type of transistors, also thermal neutrons contribute significantly to displacement damage via fragments from B + n -> Li + α reaction in highly doped p+ region near the base. Effects are additive: ΔIb = keq·Фeq + kth ·Фth where Фeq is 1 MeV neutron equivalent fluence and Фth is the fluence of thermal neutrons and keq and kth are measured in calibration irradiations. The increase of base current measured on PST and other locations in the ID is smaller than expected from simulated fluences of 1 MeV equivalent and thermal neutrons. Measured base current increase could be attributed to the effect of fast hadrons (Фeq) alone. This indicates that thermal neutron fluences may be overestimated in simulations. However, because of systematic uncertainties in calibration, the effect of thermal neutrons can not be excluded and reliable estimation of thermal neutron fluences can not be made from these measurements. |
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Major updates:
-- IanDawson - 2017-09-20 -- SvenMenke - 2020-10-21 (added interactive WebRadMaps for Run-2 and published Geant4 plots from Oct 2020 for Run-2) Responsible: AndreasHoecker
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