RPC Longevity @ GIF++

Plots approved: April 2018 updated

Figure	Description
	RE2/2 Irradiated current scans at different integrated charge. Current remains stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 Irradiated and reference current at 6.5 kV (ohmic contribute). Current remains stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 Irradiated and reference current at 9.6 kV (gas amplification contribute). Current remains stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 Current and rate ratio between irradiated and non-irradiated reference chambers as a function of the integrated charge. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE4/2 Current and rate ratio between irradiated and non-irradiated reference chambers as a function of the integrated charge. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Average resistivity as a function of the time for the four chambers. Resistivity values corrected for the temperature. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 and RE4/2 resistivity variation (Irr-Ref/Irr) as a function of the integrated charge. Resistivity values corrected for the temperature. Contact : cms-rpc-upgrade-coordinators at cern.ch

Plots approved: August 2018 TB update

Figure	Description
	RE2/2 hit efficiency as a function of the effective HV taken with no irradiation. The efficiency of the RE2/2 chamber is measured during different Test Beams (TB) corresponding to different fractions of the target charge to integrate. No significant variations have been observed in the detector performance. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 hit efficiency as a function of the effective HV taken with a background rate of around 600 Hz/cm2. The efficiency of the RE2/2 chamber is measured during different Test Beams (TB) corresponding to different fractions of the target charge to integrate. An 100V variation of the working point has been observed after having accumulated 45% of the expected integrted charge. The working point increase is due to the bakelite resistivity increase. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 irradiated efficiency as a function of the effective high voltage applied to the gas volume, at different integrated charge values and different background radiation. The effective voltage applied to the gas (HV gas ) is defined as: HV_gas = HV - RI , where the effective voltage applied to the electrodes (HV) is reduced by the voltage drop across the electrodes, which is proportional to the current (I) produced by the ionizing particles and to the bakelite resistance (R). The detector operation regime is invariant with respect to HV_gas , therefore the efficiency as a function of HV_gas does not depends anymore on the background radiation and on the bakelite resistance. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 irradiated efficiency measured at 51% of the expected integrated charge as a function of the effective high voltage, at different background radiation. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 irradiated efficiency measured at 51% of the expected integrated charge as a function of the effective high voltage applied to the gas volume, at different background radiation. The effective voltage applied to the gas (HV gas ) is defined as: HV_gas = HV - RI , where the effective voltage applied to the electrodes (HV) is reduced by the voltage drop across the electrodes, which is proportional to the current (I) produced by the ionizing particles and to the bakelite resistance (R). The detector operation regime is invariant with respect to HV_gas , therefore the efficiency as a function of HV_gas does not depends anymore on the background radiation and on the bakelite resistance. Contact : cms-rpc-upgrade-coordinators at cern.ch

RPC R&D Approved Results for Conferences

Plots approved for IEEE-NSS-MIC-2018: 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference on CINCO

Figure	Description

	Integrated charge versus time, accumulated during the longevity test at GIF++ for RE2/2 (red) and RE4/2 (blue) irradiated chambers. The RE4/2 chamber has been turned on a few months later because of total gas flow limitations. Different slopes account for different irradiation conditions during data taking. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Evolution of the hit efficiency at the working point, for RE2/2 irradiated chambers as a function of the gamma rate per unit area. The measurements have been repeated after different periods of irradiation (corresponding to 0%, 18%, 31%, 45% and 51% of the total integrated charge expected by the end of HL-LHC), and the efficiency remains stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 Irradiated dark current (without background) curves at different integrated charge. The dark current remains almost stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 Irradiated (red) and reference (blue) dark current (without background) at 6.5 kV (ohmic contribute). The dark current remains almost stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 Irradiated (red) and reference (blue) dark current (without background) at 9.6 kV (gas amplification contribute). The dark current remains almost stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 Irradiated (red) and reference noise rate (without background) (blue) at 9.6 kV (gas amplification contribute). The noise rate remains almost stable and below 1 Hz/cm2. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 Current (red) and rate (blue) ratio between irradiated and reference chambers as a function of the integrated charge. The ratio between values of the irradiated and reference chambers is to exclude the dependence on the external parameters. The measurements show a decreasing trend at the beginning of the irradiation period, up to ≈ 300 mC/cm2 , when the operating conditions, in terms of gas flow rate and relative gas humidity, were too low with respect to the high gamma background rate. These operating conditions leads to the electrodes’ resistivity increase, which caused the observed rate and current decrease. Contact : cms-rpc-upgrade-coordinators at cern.ch
	RE2/2 resistivity variation (blue) and current ratio (red) as a function of the integrated charge. The resistivity is measured running the RPCs filled with pure Argon. The resistivity variation allows to cancel out the dependence on the environmental conditions, and is defined as (Irr-Ref/Irr). The measurements show a decreasing trend at the beginning of the irradiation period, up to around 300 mC/cm 2 , when the operating conditions, in terms of gas flow rate and relative gas humidity, were too low with respect to the high gamma background rate. These operating conditions leads to the electrodes’ resistivity increase, which caused the observed rate and current decrease. These plots show also that the resistivity increase is a recoverable effect, in fact the resistivity start to decrease, and the current and rate to increase, when the gas flow and the gas relative humidity have been increased. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Evolution of the density current at the working point, for RE2/2 irradiated chambers as a function of the gamma rate per unit area. The measurements have been repeated after different periods of irradiation (corresponding to 0%, 18%, 31%, 45% and 51% of the total integrated charge expected by the end of HL-LHC), and the current remains stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Evolution of the muon cluster size at the working point, for RE2/2 irradiated chambers as a function of the gamma rate per unit area. The muon cluster size is defined as the number of fired strips per muon. The measurements have been repeated after different periods of irradiation (corresponding to 0%, 18%, 31%, 45% and 51% of the total integrated charge expected by the end of HL-LHC), and the muon cluster size remains stable. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Evolution of the gamma cluster size at the working point, for RE2/2 irradiated chambers as a function of the gamma rate per unit area. The muon cluster size is defined as the number of fired strips per gamma. The measurements have been repeated after different periods of irradiation (corresponding to 0%, 18%, 31%, 45% and 51% of the total integrated charge expected by the end of HL-LHC), and the gamma cluster size remains stable.Contact : cms-rpc-upgrade-coordinators at cern.ch

Plots approved for ICHEP2018 on CINCO

Figure	Description
	Time difference of the time arrival between the first strip end and that of the trigger T1-T0 . Contact : cms-rpc-upgrade-coordinators at cern.ch

Plots approved for ELBA2018: 14th Pisa meeting on advanced detectors on CINCO

Figure	Description
	Detector sensitivities to 137 Cs gammas measured at GIF++ (red squares) at different background conditions (ABS) compared with the simulated sensitivity: without energy threshold (black circles) and with energy thresholds of 100 keV (green inverse triangles) and at 200 keV (blue stars). Contact : cms-rpc-upgrade-coordinators at cern.ch
	iRPC sensitivity with respect to the different background particles (neutrons, photons, electrons and positrons) as a function of the incident particles energy. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Background hit rate expected in the RE3/1 station during HL-LHC as a function of the energy of the incoming particles. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Expected background hit rate in the RE3/1 station during HL-LHC as a function of R. Contact : cms-rpc-upgrade-coordinators at cern.ch

Plots approved for the TDR 2017

iRPC results

Figure	Description
	Average charge per avalanche measured on small size prototypes (65.6X35.6 cm2) using 1.20 mm (full circles), 1.40 mm (open circles), 1.60 mm (triangles), and 2.0 mm (squares) double-gap RPCs, as a function of the effective electric field strength. Electric field values are converted to the effective ones at the reference values of pressure, P = 990 hPa, and temperature, T = 293 K. The test was done at the KOrean DEtector Laboratory (KODEL). Contact : cms-rpc-upgrade-coordinators at cern.ch
	Efficiency and average cluster size are measured for the 1.4-mm double-gap RPC with a fixed threshold value of 300 μV and with three different gamma fluxes. The intensity of the gamma flux impinging on the RPC was defined by adjusting the distance of the detector from the gamma source (triangles and squares, measured at 38 and 28 cm, respectively) and by using a lead absorber (full circles measured with an absorption factor of about 2.5, at a distance of 38 cm). The Working Point (WP) for the 1.4-mm double-gap RPC is defined as the voltage at which the efficiency reaches 95%, increased by 110 V. The rates, Rstr (rate of strips) and Rclus (rate of clusters), measured at the working point with the largest gamma flux yields (at a distance of 28 cm) were found to be 4.14 and 1.85 kHz/cm2, respectively. The test was done at the KOrean DEtector Laboratory (KODEL) on a small prototype (65.6X35.6 cm2) with cosmic rays, with a gamma radiation from a 5.55 GBq^{137}Cs, and witohut irradiation. Contact : cms-rpc-upgrade-coordinators at cern.ch
	εμ and P(Cs >6) measured for the 1.4-mm double-gap RPC with a fixed threshold value of 300 μV and with three different gamma fluxes. The intensity of the gamma flux impinging on the RPC was defined by adjusting the distance of the detector from the gamma source (triangles and squares, measured at 38 and 28 cm, respectively) and by using a lead absorber (full circles measured with an absorption factor of about 2.5, at a distance of 38 cm). The Working Point (WP) for the 1.4-mm double-gap RPC is defined as the voltage at which the efficiency reaches 95%, increased by 110 V. The rates, Rstr (rate of strips) and Rclus (rate of clusters), measured at the working point with the largest gamma flux yields (at a distance of 28 cm) were found to be 4.14 and 1.85 kHz/cm2, respectively. The test was done at the KOrean DEtector Laboratory (KODEL) on a small prototype (65.6X35.6 cm2) with cosmic rays, with a gamma radiation from a 5.55 GBq^{137}Cs, and witohut irradiation. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Efficiency at the working voltage, as a function of the cluster rate for the 1.4 mm double-gap RPC. The data were measured at the fixed threshold of 300 μV. The test was done at the KOrean DEtector Laboratory (KODEL) on a small prototype (65.6X35.6 cm2) with cosmic rays, with a gamma radiation from a 5.55 GBq^{137}Cs, and witohut irradiation. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Average cluster size at the working voltage, as a function of the cluster rate for the 1.4 mm double-gap RPC. The data were measured at the fixed threshold of 300 μV. The test was done at the KOrean DEtector Laboratory (KODEL) on a small prototype (65.6X35.6 cm2) with cosmic rays, with a gamma radiation from a 5.55 GBq^{137}Cs, and witohut irradiation. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Efficiency and average cluster size of a 1.4 mm double-gap RPC, large size chamber (larger base 92 cm, lower base 63 cm, and height 166.3 cm) with 2 cm wide strips, as a function of the effective voltage, tested without gamma background. The data were measured at the fixed threshold of 300 muV and fitted with a sigmoidal function. The test was done at the Gamma Irradiation Facility at CERN (GIF++) with a muon beam. The front-end electronics threshold was fixed at the same value as in the case of the tests done in Kodel. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Efficiency and average cluster size of a 1.4 mm double-gap RPC, large size chamber (larger base 92 cm, lower base 63 cm, and height 166.3 cm) with 2 cm wide strips, as a function of the effective voltage, tested under a gamma background rate of 1.91 kHz/cm2. The data were measured at the fixed threshold of 300 muV and fitted with a sigmoidal function. The test was done at the Gamma Irradiation Facility at CERN (GIF++) with a muon beam. The front-end electronics was developed by KODEL. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Efficiency and Cluster size vs. effective voltage for the CMS gas mixture and an ecological gas mixture. The iRPC prototype was approximately 100X50 cm2 was build at KODEL. The readout consists of 32 strips (2.5 cm pitch) equipped with an electronics developed in the framework of the muon system upgrade of the ATLAS experiment. The test was done at the Gamma Irradiation Facility at CERN (GIF++) with a muon beam and cosmic rays. Contact : cms-rpc-upgrade-coordinators at cern.ch

Efficiency and Cluster size vs. effective voltage for the CMS gas mixture and an ecological gas mixture. The iRPC prototype was approximately 100X50 cm2 was build at KODEL. The readout consists of 32 strips (2.5 cm pitch) equipped with an electronics developed in the framework of the muon system upgrade of the ATLAS experiment. The test was done at the Gamma Irradiation Facility at CERN (GIF++) with a muon beam and cosmic rays. Contact : cms-rpc-upgrade-coordinators at cern.ch

Front-end electronics results

Figure	Description
	Time difference of the time arrival between the first strip end and that of the trigger T1-T0 . Contact : cms-rpc-upgrade-coordinators at cern.ch
	Measured time difference of the signal arrival time of each of the two fired strip ends T2-T1 as a function of the Y position of the scintillator-PM system center with respect to the RPC. Arbitrary origin of the Y axis is used. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Integrated charge versus time collected during the GIF++ studies for the large size iRPC prototype chambers (left), and the current stability at different ABS factor (right). Contact : cms-rpc-upgrade-coordinators at cern.ch

Longevity studies for the CMS RPC system

Figure	Description
	Current ratio between irradiated and non-irradiated reference chambers as a function of the integrated charge. Red circles correspond to RE2/2 chambers, blue squares to RE4/2. The difference in the ratio between RE2/2 and RE4/2 chambers is due to the different relative position of the chambers with respect to the reference chambers. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Rate ratio between irradiated and reference chambers as a function of the integrated charge. Red circles correspond to RE2/2 chambers, blue squares to RE4/2. The difference in the ratio between RE2/2 and RE4/2 chambers is due to the different relative position of the chambers with respect to the reference chambers. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Integrated charge versus time collected during the GIF++ studies for the RE2/2 and RE4/2 chambers. The RE4/2 chamber has been turned on few months later because of total gas flow limitations. Different slopes account for different attenuation factors during data taking. Contact : cms-rpc-upgrade-coordinators at cern.ch

| | RE2/2 hit efficiency as a function of the effective HV taken with no irradiation (left) and under a gamma background rate of about 600 Hz/cm 2 (right). The efficiency of the RE2/2 chamber is measured during different Test Beams (TB) corresponding to different fractions of the target charge to integrate: 0, 153 (18 %) and 257 mC/cm 2 (31 %). No significant variations have been observed in the detector performance. Contact : cms-rpc-upgrade-coordinators at cern.ch |

	Evolution of the hit efficiency (left) and cluster size (right) at the working point, for RE2/2 chambers as a function of the γ rate per unit area. Both irradiated and non-irradiated reference chambers are shown. The measurements have been repeated after different periods of irradiation (corresponding to 18% and 31% of the total integrated charge expected by the end of HL-LHC). Contact : cms-rpc-upgrade-coordinators at cern.ch
	Hit Efficiency (solid line) and streamer probability (dashed line) as a function of the effective working voltage for gas mixtures with different combinations based on CF3I and CO2. The results are compared with the present RPC CMS gas mixture. The streamer probability is defined as the fraction of events with an induced charge above 20 pC. Contact : cms-rpc-upgrade-coordinators at cern.ch
	Hit Efficiency (solid line) and streamer probability (dashed line) as a function of the effective working voltage for gas mixtures with different combinations of HFO-1234ze gas and CO2 (top). The results are compared with the present RPC CMS gas mixture. The streamer probability is defined as the fraction of events with an induced charge above 20 pC. Contact : cms-rpc-upgrade-coordinators at cern.ch

Plots approved in 2017 for EPS

Aging studies for the CMS RPC system

Figure

Description

The integrated charge collected up to now for the consolidation studies at GIF++ is shown as function of time. The consolidation studies were started in July 2016 including only the RE2 type chamber whereas the RE4 type chamber was only included in October 2016. Different slopes account for different attenuation factors during data taking. The flat periods to test beam periods or winter break. Contact : cms-rpc-upgrade-coordinators at cern.ch

Stability of the current of both RE2 and RE4 type chambers as function of their integrated charge. The ratio is defined as the current of the irradiated over the reference chamber. The measurements were performed under approximately the same conditions concerning background rate and working point. Globally no trend is observed and the current can be considered as stable. Small variations are accounted for different chamber conditions such as gas flow differences and overpressure. The ratio difference between both chamber types is due to the position of the chambers w.r.t. the source. Contact : cms-rpc-upgrade-coordinators at cern.ch

Efficiency versus background rate for both the irradiated and reference chamber of the RE2 type is shown. The data is collected during three test beam periods at GIF++ from October 2015 to May 2017. Error bars account for the uncertainty of the tracking algorithms used to compute the efficiency and the amount of voltage points used. No efficiency drop is observed for background rates up to 600 Hz/cm². Comparing the irradiated and the reference chamber, no degradation of the efficiency is observed up to an integrated charge of 153 mC/cm². Contact : cms-rpc-upgrade-coordinators at cern.ch

Plots approved in 2016

Plots approved for RPC2016 (February 2016)

Figure	Description
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-- IsaPedraza - 2016-07-18