RPCLongHF2019 < CMSPublic

-- Main.RoumyanaHadjiiska - 2019-07-04

---+ Longevity study & HF production in CMS-RPC

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|  *Figure*  |  *Description*  |
|[[%ATTACHURLPATH%/cls_history_b.png][<img width="298"  src="%ATTACHURLPATH%/cls_history_b.png" alt="cls_history_b.png" />]] | *Efficiency Distribution for RE4 chambers*: This plot shows the efficiency distribution of all RE4 chamber produced by January 2014 (roll by roll). Cosmic ray muon tracks reconstructed at the RE4 assembly sites were used for this measurements. Contact: stefano.colafranceschi@cernSPAMNOT.ch |

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---+++ Definitions
| [[%ATTACHURLPATH%/definitions.png][<img alt="definitions.png" src="%ATTACHURLPATH%/definitions.png" width="600" />]] | %BLUE% *Ohmic current* %ENDCOLOR% is defined as current with no beam,  up to around 7000V, in the range where there is no gas amplification contribute and the current follows the ohmic law. The ohmic current values are monitored at  6500 V, between Inject Warning and Squeeze. %BLUE% *Cosmic current* %ENDCOLOR% is defined as current with no beam, at working point voltage, in the region of the gas amplification. The cosmic current values are monitored between Beam Dump and Inject Warning. |

---+++ Figures:
| [[%ATTACHURLPATH%/ohmic_vs_time.png][<img alt="ohmic_vs_time.png" src="%ATTACHURLPATH%/ohmic_vs_time.png" width="600" />]] | Currents measured in four RPC stations are shown on the plot -W0 in the barrel and RE+1, RE+4, RE-4 in the endcap. The measured currents are plotted vs time. From the beginning of 2018 to September, a higher ohmic current has been observed in RE-4 comparing to RE+4 . After the gas flux was doubled in RE-4 (Mid-September) a significant change in its behavior has been observed, up to the point in which it drops below RE+4 curve. The ohmic current increase is directly correlated with the background.  In  the low background regions such as W+0, a very slow increase in the ohmic current has been observed. In RE+1 and W+0 the background rate is less than 10 Hz/cm<sup>2</sup> and both have similar gas flows (0.7 V/h and 0.6 V/h respectively), while in RE4 the background rate is about 40Hz/cm<sup>2</sup> and the gas flow is 1.1 V/h. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/ohmic_vs_lumi.png][<img alt="ohmic_vs_lumi.png" src="%ATTACHURLPATH%/ohmic_vs_lumi.png" width="600" />]] | Currents measured in four RPC stations are shown on the plot -W0 in the barrel and RE+1, RE+4, RE-4 in the endcap. The measured currents are plotted vs integrated luminosity. From the beginning of 2018 to September, a higher ohmic current has been observed in RE-4 comparing to RE+4 .  After the gas flux was doubled in RE-4 (Mid-September) a significant change in its behavior has been observed, up to the point in which it drops below RE+4 curve. The ohmic current increase is directly correlated with the background.  In  the low background regions such as W+0, a very slow increase in the ohmic current has been observed. In RE+1 and W+0 the background rate is less than 10 Hz/cm<sup>2</sup> and both have similar gas flows (0.7 V/h and 0.6 V/h respectively), while in RE4 the background rate is about 40Hz/cm<sup>2</sup> and the gas flow is 1.1 V/h . A clear linear dependence is observed when LHC fills with similar run conditions, i.e. periods in which the integrated luminosity grows at a constant rate. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/ohmic_decay.png][<img alt="ohmic_decay.png" src="%ATTACHURLPATH%/ohmic_decay.png" width="600" />]] | Currents measured in four RPC stations are shown on the plot - W0 in the barrel and RE+1, RE+4, RE-4 in the endcap. RE-4 has double gas flow compared to RE+4. The ohmic currents were measured during the Heavy Ion period, which have very low luminosity, and this allows the RPCs to enter in a “recovery” period. The ohmic currents measured during this period show a clear decrease. The curves were fitted using an exponential function: i(t) = p0 + p1 * exp(-p2 * t) and it was found that the RE-4 current decreases faster than it is in RE+4. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/p1_barrel.png][<img alt="p1_barrel.png" src="%ATTACHURLPATH%/p1_barrel.png" width="600" />]] | *Currents vs Instantaneous luminosity - Slopes*: The RPC currents depend linearly on the instantaneous luminosity [1]. For each LHC fill the linear distributions were fit to a linear function in order to obtain the slope (P1) a.k.a. physics current (i = P1 * L). Due to the nature of the linear fit, P0 (Offset) absorbs the cosmic current (offset + ohmic + gas gain). The slopes (P1) as a function of a time for the five barrel wheels are shown on the plot. As it might be seen from it, P1 is stable in time. The changes in the middle of August are due to different applied HV working points. Wheels, located at equal distances from the interaction point along the beam pipe, have similar slopes (P1 values). They also have very similar rates [1]. No increase due to integrated luminosity is observed for the slopes for the entire year. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/p1_endcap.png][<img alt="p1_endcap.png" src="%ATTACHURLPATH%/p1_endcap.png" width="600" />]] | *Currents vs Instantaneous luminosity - Slopes*: The RPC currents depend linearly on the instantaneous luminosity [1]. For each LHC fill the linear distributions were fit to a linear function in order to obtain the slope (P1) a.k.a. physics current (i = P1 * L). Due to the nature of the linear fit, P0 (Offset) absorbs the cosmic current (offset + ohmic + gas gain). The slopes (P1) as a function of a time for the endcap stations are shown on the plot. As it might be seen from it, P1 is stable in time. The changes in the middle of August are due to different applied HV working points. Endcap staions, located at equal distances from the interaction point along the beam pipe, have similar slopes (P1 values). They also have very similar rates [1]. No increase due to integrated luminosity is observed for the slopes for the entire year. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/ohmic_vs_HV.png][<img alt="ohmic_vs_HV.png" src="%ATTACHURLPATH%/ohmic_vs_HV.png" width="400" />]] | The currents, measured in different years, as a function of the HV, for an example RPC chamber are shown in the plot. The lowest curve depicts for the currents measured in middle of September in 2016. The blue and green markers corresponds to currents measured in July and October in 2017, and the purple ones - to currents measured in the beginning  of 2018. As it might be seen from the plot, the current increases as collisions go on. From the near end of 2017 to April 2018 we observe that the current decreases significantly during the YETS (Year End Technical Stop). Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/HF_vs_time.png][<img alt="HF_vs_time.png" src="%ATTACHURLPATH%/HF_vs_time.png" width="400" />]] | The Hydrogen Fluoride (HF), produced in the gas under high electrical discharge may accelerate the detectors aging and may represents a possible cause for inner detector surface damaging and relative ohmic current increase, due to its electrical conductivity and high chemical reactivity. The HF measurements have been performed using an ion-selective electrode (ISE), which is a transducer (or sensor) that converts the activity of a specific ion [F-] dissolved in a solution into an electrical potential. The measurements have been performed at the gas exhaust of 3 regions: W0 in the barrel and RE+1, RE+4 in the endcap. *The HF concentration is shown as a function of the time*. The amount of HF is accumulated as collisions take place in CMS hence the increasing value. RE+1 and W+0, have a similar HF concentration, gas flow (0.7 V/h and 0.6 V/h ) and background (less than 10 Hz/cm<sup>2</sup>). In RE+4 the amount of HF accumulated is around 2 times higher, higher background (~ 40Hz/cm<sup>2</sup>) and the gas flow is 1.1 V/h, 2 times more than W+0 and RE+1. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/HF_vs_lumi.png][<img alt="HF_vs_lumi.png" src="%ATTACHURLPATH%/HF_vs_lumi.png" width="400" />]] | The Hydrogen Fluoride (HF), produced in the gas under high electrical discharge may accelerate the detectors aging and may represents a possible cause for inner detector surface damaging and relative ohmic current increase, due to its electrical conductivity and high chemical reactivity. The HF measurements have been performed using an ion-selective electrode (ISE), which is a transducer (or sensor) that converts the activity of a specific ion [F-] dissolved in a solution into an electrical potential. The measurements have been performed at the gas exhaust of 3 region: W0 in the barrel and RE+1, RE+4 in the endcap. *The HF concentration is shown as a function of the integrated luminosity*. There is a clear linear dependence between the HF concentration and the integrated luminosity. RE+1 and W+0, have a similar HF concentration, gas flow (0.7 V/h and 0.6 V/h ) and background (less than 10 Hz/cm<sup>2</sup>). In RE+4 the amount of HF accumulated is around 2 times higher, higher background (~ 40Hz/cm<sup>2</sup>) and the gas flow is 1.1 V/h, 2 times more than W+0 and RE+1. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/ohmic_vs_HF.png][<img alt="ohmic_vs_HF.png" src="%ATTACHURLPATH%/ohmic_vs_HF.png" width="400" />]] | The Hydrogen Fluoride (HF), produced in the gas under high electrical discharge may accelerate the detectors aging and may represents a possible cause for inner detector surface damaging and relative ohmic current increase, due to its electrical conductivity and high chemical reactivity. The HF measurements have been performed using an ion-selective electrode (ISE), which is a transducer (or sensor) that converts the activity of a specific ion [F-] dissolved in a solution into an electrical potential. The measurements have been performed at the gas exhaust of 3 region: W0 in the barrel and RE+1, RE+4 in the endcap. *The ohmic current as a function of  HF concentration is shown on the plot*. RE+1 and W+0, have a similar HF concentration, gas flow (0.7 V/h and 0.6 V/h ) and background (less than 10 Hz/cm<sup>2</sup>). In RE+4 the amount of HF accumulated is around 2 times higher, higher background (~ 40Hz/cm<sup>2</sup>) and the gas flow is 1.1 V/h, 2 times more than W+0 and RE+1. There is a clear linear dependence between the ohmic current and HF concentration. HF trapped in the gap may form a thin conductive layer that increase the ohmic current, therefore it is necessary to fine tune the gas flow as a function of the background rate so that the HF is efficiently removed. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/HF_CONCENTRATION_umol_liter_vsRATE.png][<img alt="HF_CONCENTRATION_umol_liter_vsRATE.png" src="%ATTACHURLPATH%/HF_CONCENTRATION_umol_liter_vsRATE.png" width="400" />]] | The Hydrogen Fluoride (HF), produced in the gas under high electrical discharge may accelerate the detectors aging and may represents a possible cause for inner detector surface damaging and relative ohmic current increase, due to its electrical conductivity and high chemical reactivity. The HF production has been studied at GIF++ as a function of the background rate and gas flow. For the test a spare CMS-RPC chamber and standard gas mixture have been used. The HF measurements, at gas exhaust, have been performed using an ion-selective electrode (ISE), which is a transducer (or sensor) that converts the activity of a specific ion [F-] dissolved in a solution into an electrical potential. *The results show a linear dependence of the HF concentration rate on the background rate (and its corresponding current on the top X-axis), indeed the current increase linearly with the background increases.  The blue markers represent the results, obtained with the lowest gas flow, while the red ones - with the higher. The slopes  of the measured curves dependent on the gas flow - higher is the gas flow, less is the HF concentration. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/ratio.png][<img alt="ratio.png" src="%ATTACHURLPATH%/ratio.png" width="400" />]] | Ratio of the fluoride concentration measured in RPC at GIF++, at different gas volume exchanges with respect to 1 gas volume exchange per hour. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/HF_TRAPPED_umolh_vsRate.png][<img alt="HF_TRAPPED_umolh_vsRate.png" src="%ATTACHURLPATH%/HF_TRAPPED_umolh_vsRate.png" width="400" />]]| Fluoride concentration trapped inside the RPC gas gap and not efficiently removed. The HF concentration was measured at GIF++ at different background rate, and with three different gas flow. The estimation was done considering the HF accumulated during 8 hours of measurements, just after the detector switch off. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/noise_rate.png][<img alt="noise_rate.png" src="%ATTACHURLPATH%/noise_rate.png" width="400" />]]|[[%ATTACHURLPATH%/ohmic_GIF.png][<img alt="ohmic_GIF.png" src="%ATTACHURLPATH%/ohmic_GIF.png" width="400" />]]| Few spare RPC chambers are under gamma irradiation at GIF++ for the CMS-RPC system certification at HL-LHC. After having collected ~ 600 mC/cm<sup>2</sup> from 2016 the detector performance and parameters are stable. *Left: Irradiated chamber noise rate profile at 9.8kV*, after having collected different amount of charge. The noise rate remains low, less than 1 Hz/cm<sup>2</sup>, and the profile is stable. *Right: Ohmic current versus the integrated charge*, for the irradiated (blue) and reference (red) chamber, at 6.5 kV. Ohmic current is low and almost stable in time after having collected around 600 mC/cm<sup>2</sup>. Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |

| [[%ATTACHURLPATH%/ratioRE2.png][<img alt="ratioRE2.png" src="%ATTACHURLPATH%/ratioRE2.png" width="400" />]] | Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |
| [[%ATTACHURLPATH%/darkcurrent_IRR_REF_AT_WP.png][<img alt="darkcurrent_IRR_REF_AT_WP.png" src="%ATTACHURLPATH%/darkcurrent_IRR_REF_AT_WP.png" width="400" />]] | Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |
| [[%ATTACHURLPATH%/noiserate_IRR_REF_AT_WP.png][<img alt="noiserate_IRR_REF_AT_WP.png" src="%ATTACHURLPATH%/noiserate_IRR_REF_AT_WP.png" width="400" />]] | Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |
| [[%ATTACHURLPATH%/RE2-2-NPD-BARC-9_CurrentTOT_ALL-overlap.png][<img alt="RE2-2-NPD-BARC-9_CurrentTOT_ALL-overlap.png" src="%ATTACHURLPATH%/RE2-2-NPD-BARC-9_CurrentTOT_ALL-overlap.png" width="400" />]] | Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |
| [[%ATTACHURLPATH%/RE2_ResistivityRATIO_RatioCurrent_overlapped.png][<img alt="RE2_ResistivityRATIO_RatioCurrent_overlapped.png" src="%ATTACHURLPATH%/RE2_ResistivityRATIO_RatioCurrent_overlapped.png" width="400" />]] | Contact: cms-dpg-conveners-rpc@SPAMNOTcern.ch |





---++ References
[1] RPC Detector Performance Results for 2016 and 2017, [[https://cds.cern.ch/record/2305542?ln=en][CMS-DP-2018-001 ; CERN-CMS-DP-2018-001]]

Attachments

Topic attachments
I	Attachment	History	Action	Size	Date	Who
png	HF_CONCENTRATION_umol_liter_vsRATE.png	r1	manage	30.4 K	2019-09-30 - 18:25	UnknownUser
png	HF_TRAPPED_umolh_vsRate.png	r1	manage	20.4 K	2019-09-30 - 18:25	UnknownUser
png	HF_vs_current_GIF.png	r1	manage	25.8 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	HF_vs_lumi.png	r1	manage	22.5 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	HF_vs_time.png	r1	manage	18.1 K	2019-07-04 - 10:37	RoumyanaHadjiiska
png	RE2-2-NPD-BARC-9_CurrentTOT_ALL-overlap.png	r1	manage	99.1 K	2020-01-27 - 16:30	AndresCabrera
png	RE2_ResistivityRATIO_RatioCurrent_overlapped.png	r1	manage	19.2 K	2020-01-27 - 16:30	AndresCabrera
png	darkcurrent_IRR_REF_AT_WP.png	r1	manage	22.1 K	2020-01-27 - 16:30	AndresCabrera
png	definitions.png	r1	manage	69.8 K	2019-07-04 - 10:45	RoumyanaHadjiiska
png	noise_rate.png	r1	manage	18.5 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	noiserate_IRR_REF_AT_WP.png	r1	manage	22.8 K	2020-01-27 - 16:30	AndresCabrera
png	ohmic_GIF.png	r1	manage	32.6 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	ohmic_decay.png	r1	manage	88.6 K	2019-07-04 - 10:37	RoumyanaHadjiiska
png	ohmic_vs_HF.png	r1	manage	19.0 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	ohmic_vs_HV.png	r1	manage	34.8 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	ohmic_vs_lumi.png	r1	manage	272.3 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	ohmic_vs_time.png	r1	manage	294.8 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	p1_barrel.png	r1	manage	246.2 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	p1_endcap.png	r1	manage	275.7 K	2019-07-04 - 10:36	RoumyanaHadjiiska
png	ratio.png	r1	manage	12.4 K	2019-09-30 - 18:25	UnknownUser
png	ratioRE2.png	r1	manage	20.0 K	2020-01-27 - 16:30	AndresCabrera

This topic: CMSPublic > PhysicsResults > MuonDPGResults > RPCLongHF2019
Topic revision: r4 - 2020-01-27 - AndresCabrera

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