FLUKA studies for a new sampling calorimeter in the forward ECAL

Contents:

Objective

  • HL-LHC (High-Luminosity LHC): 10 x higher instantaneous Luminosity (up to 10^35 cm-2s-1 )
  • Replacement of the ECAL Endcaps
  • Future EE calorimeter challenged in terms of performance and radiation hardness:
    • Harsh radiation environment and energetic hadron fluences (ca. 10 x higher), pile-up
  • Sampling calorimeter is one option for a new electromagnetic calorimeter

FLUKA studies for a sampling calorimeter for EE

Goal:
  • FLUKA designed for calculations of flux maps, particle spectra, energy depositions, dose distributions, activation etc.
  • Rather “minimum bias” scenario in CMS than “detector response” studies (Geant)
  • Implementation of a configurable sampling calorimeter for the HL-LHC
  • Determination of dose rates and particle fluxes within CMS for and in the presence of different calorimeters
  • Examination and tracking of
    • Creation of isotopes that might produce a prohibitive background signal
    • Simulation of thermal neutrons as some elements have high neutron cross section
    • E.g. how much energy is deposited by the decaying isotopes?
  • CMS description in FLUKA:
    Implementation_of_CMS_ECAL_in_FLUKA.png

Electromagnetic sampling calorimeter

  • Configurable materials, number and size of layers
  • Divided in 5 η bins: 1.48-1.6-1.8-2.2-2.6-2.9
  • FLUKA CMS geometry with sampling calorimeter:
    sampcaloinFLUKA.png * Current study based on a 25 X0 sampling calorimeter
  • Total length maximal 22 cm
  • If smaller than 22 cm the rest of the current EE region (Lead Tungsten) is filled with a low density material, also used for the tracker region (rho=0.047g/cm3: 30% Fe, 23% Al, 30% C, some Air)
  • Sampling calorimeter with alternating layers of * 20 X0 of passive absorber Tungsten (14 layers) * 5 X0 of an heavy inorganic scintillator: cerium fluoride (CeF3), LYSO, YSO (15 layers) * Corresponding sampling fraction, sampling resolution and Moliere Radius simulated with Geant4 standalone simulation by Sasha Ledovsky. This specific simulation was done by Francesco Pandolfi:
    geant4_Results.png * The Geant4 simulation shows, that the chosen parameters give reasonable results * The layer number and size is chosen such that any conflicts with the energy calculations of the Monte Carlo program FLUKA can be excluded

Studies with different sampling calorimeter geometries

  • All plots are created with FLUKA2011.2b.5 and based on the CMS FLUKA nominal geometry version 1.0.0.0
  • FLUKA parameters for HL-LHC running conditions:
    FLUKAparameters_HL-LHC.png

FLUKA activation studies for HL-LHC up to LS5

  • FLUKA parameters for activation study:
    FLUKAparameters_activation.png

Irradiation cycle until LS5 as used by BRIL radiation simulation group

* CMSirrProf_Sophie.xls: Irradiation cycle until LS5 as used by BRIL radiation simulation group

Additional material for plots for approval

PLOTS FOR APPROVAL

1. part: Validation of FLUKA geometry with a sampling calorimeter as replacement for ECAL forward calorimeter

  • samp_calorimeter_forEE.png:
    samp_calonewwithoutnaming.png
The implementation of the sampling calorimeter in the ECAL forward region is based on the FLUKA geometry version 1.0.0.0, the available baseline geometry version, corresponding to the situation prior to LS1. Only the region of the current Lead Tungstate crystals in the ECAL forward region is modified ( 320 cm - 342 cm in z). The sampling calorimeter versions are tagged with respect to the scintillator choice, version 1.0.1-1.0.3 for YSO, LYSO,CeF_3, respectively. The sampling calorimeter consists of 15 layers of scintillator material and 14 layers of Tungsten. It has a total radiation length of 25 X_0, split into 5 X_0 for the scintillator and 20 X_0 for the absorber. If the total length is smaller than 22 cm, the rest of the volume will be filled with a region of very low density (ρ=0.047g/cm3), reflecting a region filled with cables and electronics. Identical to nominal geometry 1.0.0.0: the transition region between barrel and endcap region consists of an averaged material, accounting for the mechanics and cables in this region. The preshower in front of the sampling calorimeter acts as a placeholder for a possible timing device and the polyethylene moderator to shield the tracker. Directly behind the sampling calorimeter, the Aluminium plate for the mounting of the current Lead Tungsten crystals is used as a placeholder for a similar support structure. The electronics, mechanics and cooling for this calorimeter are implemented as an averaged material, the same low density material as used for the tracker region, together with a polyethylene volume for shielding.

2. part: benchmark of simulation: overall particle flux and dose rate

Technical specifications which all plots have in common: Primary proton-proton collisions with an energy of 7TeV per beam. Inelastic collision cross section used for normalization is 80 mb. Used simulation cut offs in ECAL endcap region: Hadrons 100 keV, Neutrons 0.01 meV, Photons 50 keV, Electrons 100 keV. In the surrounding regions, photons and electrons have higher cutoffs, 100keV and 300keV respectively. The FLUKA geometry version 1.0.0.0, the available baseline geometry version, corresponding to the situation prior to LS1, the EE is modeled with a single volume of Lead Tungstate. Version 1.0.1-1.0.3 for the respective calorimeter options are based on version 1.0.0.0. Only the region of the current Lead Tungstate crystals in the ECAL forward region is modified ( 320 cm - 342 cm in z). The sampling calorimeter consists of 15 layers of scintillator material and 14 layers of Tungsten. It has a total radiation length of 25 X_0, split into 5 X_0 for the scintillator and 20 X_0 for the absorber. If the total length is smaller than 22 cm, the rest of the volume will be filled with a region of very low density (ρ=0.047g/cm3), reflecting a region filled with cables and electronics.

* ElectronPositronfluence.png:
elpofluence140320.png * CMSpp_EEcomp_elpo_eta1.8_2.6_140319.eps: CMSpp_EEcomp_elpo_eta1.8_2.6_140319.eps Monte Carlo estimation of the electron and positron fluence in CMS with a forward ECAL sampling calorimeter (EE) under HL-LHC conditions using FLUKA. The plot shows the electron and positron fluence in the EE for an integrated luminosity of 3000.0 fb-1 as a function of the radiation length X_0. The radius of 48 cm - 109 cm corresponds to 1.8 < η < 2.6 for z= 320 cm. The z-coordinate is converted to radiation length by scaling with the effective radiation length for each calorimeter. The conversion factors are: 0.88 X0/cm for PbWO4, 0.88 X0/cm for YSO/W, 0.508 or LYSO/W and 0.616 for CeF3/W. The bin size is 10% of the effective radiation length of the respective calorimeter to visualise differences between the active and passive layers.The fluence for Lead Tungstate is depicted as a reference. The sampling fraction and density of the scintillator materials influences the distribution up to 7 X_0. Most of the electromagnetic particles in a minimum bias environment have an energy of a few MeV up to 1 GeV. The maximum electromagnetic particle flux develops in the first 4 X_0, particularly in the second scintillator layer.

Monte Carlo estimation of the "absorbed dose" for CMS with a forward ECAL sampling calorimeter (EE) under HL-LHC conditions using FLUKA. The plot shows the dose absorbed in the EE for an integrated luminosity of 3000.0fb-1 as a function of the radiation length X_0. The radius of 48 cm - 109 cm corresponds to 1.8 -< η < 2.6 at z=320 cm. The z-coordinate is converted to radiation length by scaling with the effective radiation length for each calorimeter. The conversion factors are: 0.88 X0/cm for PbWO4, 0.88 X0/cm for YSO/W, 0.508 or LYSO/W and 0.616 for CeF3/W. The bin size is 10% of the effective radiation length of the respective calorimeter to visualise differences between the active and passive layers. The calculated dose corresponds to the dose absorbed in the implemented material. Any material not implemented in the geometry might have a different dose due material dependent interaction coefficients. The absorbed dose for Lead Tungstate is depicted as a reference. The absorbed dose is a conversion of the deposited energy and depicts as such the different sampling fractions of the sampling calorimeter options. The increase of the dose rate in LYSO/W at the end is explainable looking by the high thermal neutron cross section of Lutetium. In contrast to the other options is the absorbed dose in the scintillator layer higher than in the Tungsten layers. The absorbed dose rate in LYSO increases significantly to the end of the calorimeter because of the higher thermal neutron fluence in the low density regions next to the calorimeter. A thin absorber layer made out of Boron polyethylene is advisable to moderate neutrons and absorb the thermal neutrons.

  • Backscattering neutrons at front surface of sampling calorimeters for 3000 fb^{-1}:
    neutronbacksacttering140320.png

Monte Carlo estimation of the neutron fluence energy spectrum for CMS with a forward ECAL sampling calorimeter (EE) under HL-LHC conditions using FLUKA. The plot shows the fluence energy spectrum of backscattered neutrons from the first scintillator layer to air in 2.2<η<2.6. for 3000 fb^{-1}. This boundary crossing estimator is integrated over the full solid angle and given as a differential distribution in energy, the value of each energy bin is thus multiplied by the width of the bin. Only backscattered neutrons from the first scintillator layer are recorded.In the region or low-energy neutrons, the number and width of the bins is limited by the thermal neutron cross section library in FLUKA which consists of 260 data sets from 0.01 meV (simulation cutoff ) up to 20 MeV. Thermal neutrons carry an energy up to a few eV, followed by a resolved resonance region up to a few 1 keV. This region shows different resonances for each option due to their different elements. LYSO/W shows a significantly lower fluence for thermal neutrons, as it has a high thermal neutron capture cross section, resulting in a higher absorbed dose. From a few MeV upwards all options show a similar shape for the albedo neutrons.

3. part: activation study for sampling calorimeter

  • Neutron fluence energy spectrum:
    neutronspectra.png

Monte Carlo estimation of the neutron fluence energy spectrum for CMS with a forward ECAL sampling calorimeter (EE) under HL-LHC conditions using FLUKA. The plot shows the fluence energy spectrum of neutrons for the maximal particle flux, which is in the second scintillator layer in 2.2<η<2.6. for 3000 fb^{-1}. This boundary crossing estimator is given as a differential distribution in energy, the value of each energy bin is thus multiplied by the width of the bin. In the region or low-energy neutrons, the number and width of the bins is limited by the thermal neutron cross section library in FLUKA which consists of 260 data sets from 0.01 meV (simulation cutoff ) up to 20 MeV. Thermal neutrons carry an energy up to a few eV, followed by a resolved resonance region up to a few 1 keV. This region shows different resonances for each option due to their different elements. The resonances are distinct as they are recorded in the scintillator material. LYSO/W shows a significantly lower fluence for thermal neutrons, as it has a high thermal neutron capture cross section, resulting in a higher absorbed dose. From a few MeV upwards all options show a similar shape for the albedo neutrons. The spectrum contains also high energy neutrons of a few GeV, evoking a hadronic shower.

Monte Carlo estimation of the absorbed dose rate due to the prompt electromagnetic shower and of the decay products for an LYSO/ Tungsten sampling calorimeter for the forward ECAL sampling calorimeter (EE) under HL-LHC conditions using FLUKA. The absorbed dose rate is projected to the calorimeter length in z, from 320 cm - 332.8 cm. The volume behind the sampling calorimeter is filled with a region of very low density (ρ=0.047g/cm3), reflecting a region filled with cables and electronics. The plot compares the absorbed dose rate for a collision rate of 1.44*10^11 pp-int./h with the absorbed dose rate by decaying particles at the irradiation stop after 2475 fb^-1, starting from LS3 until LS5. The absorbed dose rate is visualised for two regions in R-Z: 48 cm - 71 cm and 109 cm -135 cm, corresponding to η = 1.6-1.8 and 2.2-2.6 at z= 320 cm. Both rates differ in average by two orders or magnitude. The inelastic cross section of the prompt EM shower is normalised to running conditions whereas the part from the decay products at the irradiation stop of LS5 is normalised to a higher cross section as an upper limit for activation studies (recommendation from radiation protection recommondation). The absorbed dose rate of the decay products is dominated by short lived radionuclides.

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng 140416_LYSO_PWO_comp_color.png r1 manage 13.6 K 2014-03-16 - 20:11 MilenaQuittnat Compare the expected remnant radioactivity ḢIND among crystals of similar dimensions in terms of radiation lengths
Microsoft Excel Spreadsheetxls CMSirrProf_Sophie.xls r1 manage 159.0 K 2014-03-18 - 04:24 MilenaQuittnat Irradiation cycle until LS5 as used by BRIL radiation simulation group
Unknown file formateps CMSpp_EECeF3_Dose2d_140319.eps r1 manage 891.1 K 2014-03-19 - 23:23 MilenaQuittnat  
Unknown file formateps CMSpp_EELYSO_Neutron2d_140319.eps r1 manage 1500.6 K 2014-03-19 - 23:23 MilenaQuittnat  
Unknown file formatdat CMSpp_EEYSO_Dose140319_eta1.8-2.6_1d_radbinning.dat r1 manage 12.7 K 2014-03-19 - 23:26 MilenaQuittnat  
PDFpdf CMSpp_EEcompPbWO4_sampcalo_dose_eta1.8-2.6_140302.pdf r1 manage 56.1 K 2014-03-16 - 20:43 MilenaQuittnat dummy
Unknown file formateps CMSpp_EEcomp_dose_eta1.8-2.6_140319.eps r1 manage 111.7 K 2014-03-20 - 10:42 MilenaQuittnat  
Unknown file formateps CMSpp_EEcomp_elpo_eta1.8_2.6_140319.eps r1 manage 112.1 K 2014-03-20 - 10:47 MilenaQuittnat  
PNGpng ElectronPositronfluence.png r1 manage 25.7 K 2014-03-18 - 00:07 MilenaQuittnat  
PNGpng FLUKAconditions_foractivation.png r1 manage 66.2 K 2014-03-18 - 04:25 MilenaQuittnat FLUKA parameters for activation study
PNGpng FLUKAparameters_HL-LHC.png r1 manage 74.6 K 2014-03-19 - 15:45 MilenaQuittnat FLUKA parameters for HL-LHC running conditions
PNGpng FLUKAparameters_activation.png r1 manage 79.3 K 2014-03-20 - 11:14 MilenaQuittnat  
PNGpng FLUKAparamters_activationstudy.png r1 manage 71.1 K 2014-03-18 - 21:35 MilenaQuittnat FLUKA parameters for activation study
PNGpng Implementation_of_CMS_ECAL_in_FLUKA.png r1 manage 195.1 K 2014-03-19 - 15:07 MilenaQuittnat CMS description in FLUKA
Unknown file formateps LYSO_dose_differenteta_140320.eps r2 r1 manage 131.5 K 2014-03-20 - 11:10 MilenaQuittnat  
PDFpdf Lu_all_reactions.pdf r1 manage 157.7 K 2014-03-19 - 14:13 MilenaQuittnat Lutetium high neutron capture cross section
PNGpng Neutron_scatteringcomparison.png r1 manage 26.7 K 2014-03-19 - 15:14 MilenaQuittnat Comparison of forward and backscattering neutrons at front surface of calorimeter
PDFpdf X4R19961_x4.pdf r1 manage 58.0 K 2014-03-19 - 14:13 MilenaQuittnat Lutetium high neutron capture cross section
PNGpng absorbed_dose.png r1 manage 31.9 K 2014-03-18 - 19:03 MilenaQuittnat Absorbed dose rate for sampling calorimeter
PNGpng absorbed_dose_rateYSO.png r1 manage 24.5 K 2014-03-19 - 15:58 MilenaQuittnat Absorbed dose rate in YSO/W calorimeter
Unknown file formateps allparticlespectra_EEYSO_eta1.6_140319.eps r1 manage 72.0 K 2014-03-19 - 23:23 MilenaQuittnat  
PNGpng dose140320.png r1 manage 16.9 K 2014-03-20 - 10:56 MilenaQuittnat  
PNGpng doseLYSO140320.png r1 manage 18.3 K 2014-03-20 - 11:10 MilenaQuittnat  
Unknown file formateps dose_differenteta_140317.eps r1 manage 143.9 K 2014-03-17 - 10:03 MilenaQuittnat CeF3 sampling calorimeter comparison absorbed dose rate
Unknown file formateps electron_backwardscattering_140319.eps r1 manage 33.7 K 2014-03-20 - 10:41 MilenaQuittnat  
PNGpng elpofluence140320.png r1 manage 19.1 K 2014-03-20 - 10:56 MilenaQuittnat  
PNGpng geant4_Results.png r1 manage 32.4 K 2014-03-18 - 04:17 MilenaQuittnat  
Unknown file formateps isoleth_neutron_spectra_showermax140319.eps r1 manage 114.2 K 2014-03-20 - 12:03 MilenaQuittnat  
Unknown file formateps neutron_backwardscattering_140319.eps r1 manage 112.4 K 2014-03-19 - 23:23 MilenaQuittnat  
Unknown file formateps neutron_backwardscattering_140320.eps r1 manage 111.9 K 2014-03-20 - 11:02 MilenaQuittnat  
PNGpng neutron_fluence_backscattering.png r1 manage 32.9 K 2014-03-18 - 11:56 MilenaQuittnat Neutron backscattering per proton collision
Unknown file formateps neutron_scatteringcomparison_140319.eps r1 manage 207.9 K 2014-03-19 - 23:23 MilenaQuittnat  
PNGpng neutronbacksacttering140320.png r1 manage 19.0 K 2014-03-20 - 11:02 MilenaQuittnat  
PNGpng neutronspectra.png r2 r1 manage 18.6 K 2014-03-20 - 11:10 MilenaQuittnat  
PNGpng samp_calonewwithoutnaming.png r1 manage 39.6 K 2014-03-18 - 00:09 MilenaQuittnat  
PNGpng sampcaloinFLUKA.png r1 manage 200.9 K 2014-03-16 - 20:27 MilenaQuittnat FLUKA CMS geometry with sampling calorimeter
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