Scope Review (draft): Purity Monitors for DUNE Jianming Bian (UC Irvine) Andrew Renshaw (U of Houston) Stephen Pordes (Fermilab) 1
Motivation of Purity Monitors • Cryostat Operation (cryostat+inline): monitor argon filling during commissioning, alert pump and cryogenic accidents during operation, alert unexpected contamination • Provide benchmarks LAr purities for recirculation studies and TPC calibration • Measure e-lifetime for TPC • Measure purity stratification • Verify CDF 2
Scope of work • UCI, UH and Fermilab are involved • Build 6 PrM in the DUNE cryostat, 4 standard and 2 long • Build 4 standard PrM within recirculation (inline) • Build electric and optical feedthroughs • Build two mounting structures and top flanges • Build FEB Electronics • DAQ • Xenon light sources with Faraday cage • HV and LV 3
How was output from the purity monitors used in ProtoDUNE and for which operational phases was the data collected critical? • Continuously (hourly) monitor LAr Purity during filling (July23-Sep29): Start to Monitoring purity right after bottom PrM submerged LAr, found filter saturation during the filling à report to cryo people to regenerate cartridges • During beam data taking (Sep – Dec 2018): Monitoring LAr Purity a few times a day, alerted the experiment solely to serious problems several times - recirculation pump stoppages, false alarms, problems from the cryostat- level gauges. prevented situations which otherwise would have continued unnoticed for some time, with severe consequences to the ability to take any data. Neither the gas analyzers nor the TPC caught these problems in time. • During beam and cosmic ray data taking (Sep 2018 - now): Provides benchmark LAr purities for recirculation studies and TPC calibration, measure e-lifetime for TPC • Critical to LAr filling and beam data taking, critical to TPC calibration and recirculation study 4
Monitor LAr Purity during filling Monitor purity during LAr filling, find saturation during the filling As soon as the lowest purity monitor was immersed: ~40 us -> 7.5 ppb O 2eq On Thursday 30 st of August purity was compatible with ~60 us Anode signal Cathode signal ProtoDUNE-SP: On Friday 31 st of August, 2018 the purity of the bulk liquid argon dropped from 40 us purification cartridges needed to be regenerated. Regeneration took till the 3 rd of September. Filling restarted immediately after. Filippo Resnati - DUNE Collaboration Meeting - CERN - 28 th January 2019 5
Monitoring LAr Purity During Operation During data taking, ProtoDUNE-SP, PrMs have alerted the experiment solely to serious problems several times (dips): Recirculation pump stoppages, false alarms, and problems from the cryostat-level gauges. These alerts are critical to the ProtoDUNE-SP project's success, as they prevented situations which otherwise would have continued unnoticed for some time, with severe consequences to the ability to take any data. Neither the gas analyzers nor the TPC caught these problems in time. 6
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Lifetime for Cryogenic System Studies PrMs are sensitive to purity change Typically no regular TPC data when testing recirculation reduced pump speed All boil-off filtered pump off All boil-off vented pump off All boil-off GAr condensed and returned Pump restart P1 P2 P3 P4 P5 Mar 12, 2019 Ilsoo Seong 8
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PrM vs. TPC e-lifetime TPC lifetime 2 Mean = 6.1ms RMS = 2.0 ms Top PrM Mid PrM Bottom PrM Mean = 6.99ms Mean = 6.20ms Mean = 4.85ms RMS = 0.36 ms RMS = 0.40 ms RMS = 0.19 ms TPC lifetime 1 Mean = 4.6, 6.1ms RMS = 1.0, 1.4 ms PrM : 200 flashes/measurement PrM e-lifetime stat. error is much smaller than TPC because it measures localized purity with large statistics 10
Lifetime for TPC calibrate Choose TPC cosmic runs under same PrM purities for e-lifetime calibration Important for DUNE because cosmic rate is low 11
Lifetime for TPC calibrate Craig Thorn, LBNE-Doc-4482-v1, Xin Qianhttps://indico.fnal.gov/event/14296/contributi on/0 Electron lifetime: tau = 1/k_A*ns , where k_A is the electron attachment rate and ns is the concentration of a certain type of impurity. Attachment rates k_A at different E-fields are different, make electron lifetime and Qa/Qc different in TPC and PrM different due to their different operation HVs Develop TPC-PrM combined lifetime measurement: (Qa/Qc)_TPC= f*(Qa/Qc)_PrM f obtained from fit to (1/tau0-1/tau)_TPC vs. (1/tau0-1/tau)_PrM in data, space charge effects largely cancelled Result consistent with prediction from SCE corrected e-lifetime time prediction by Flavio and Xiao) 12
Is the purity stratification observed within the ProtoDUNE-SP cryostat real and if so, is this consistent with initial purity measurements from cosmic rays? • We see hints from purity monitors, but we need to calibrate relative difference among purity monitors to address purity stratification in ProtoDUNE-SP • TPC lifetime measurements affected by statistics, space charge effects and other non-uniformity issues. E- lifetime measurements with different TPC methods are different, varying from 8 – 30ms • Until now ProtoDUNE-SP does not have reliable electron lifetime from TPC, therefore, there is no purity stratification measurements from TPC 13
<latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> <latexit sha1_base64="(nul)">(nul)</latexit> Uncertainties − t drift τ lifetime = ! f RC • Included the run-to-run variations as a systematic error Q A A log f trans • Note that the table shows the relative error of each source, not the lifetime f RC Q C C Relative uncertainties, affect sensitivity to catch purity change 0.55% in eq. Qa/Qc 14
Lifetime with 1-sigma band for absolute (overall) uncertainty Hints for e-lifetime stratification Absolute uncertainty 5-9% in lifetime at ~7ms, dominated by transparency correction and anode/cathode gain correction Gain uncertainty can be calibrated in vacuum à Will do so when we pull PrM Assembly out to prepare for protoDUNE-SP run2 Transparency correction uncertainty can be prevented if we have longer purity monitors 15
PrM vs. TPC e-lifetime TPC lifetime 2 Mean = 6.1ms RMS = 2.0 ms Top PrM Mid PrM Bottom PrM Mean = 6.99ms Mean = 6.20ms Mean = 4.85ms RMS = 0.36 ms RMS = 0.40 ms RMS = 0.19 ms TPC lifetime 1 Mean = 4.6, 6.1ms RMS = 1.0, 1.4 ms PrM : 200 flashes/measurement PrM e-lifetime stat. error is much smaller than TPC because it measures localized purity with large statistics 16
What are the limitations of the purity monitors in terms of measuring high purity levels and what are the benefits that would be obtained by implementing proposed improvements to these devices? For Detector Operation (relative measurement): • Statistical Qa/Qc uncertainty < 1% à very sensitive to catch purity change for LArTPC operation • To catch lifetime change at 5 sigma need Qa/Qc < (1-5*1%) = 0.95, equivalent to 42 ms lifetime for regular PrM drift time 2.2ms For absolute lifetime measurement: • TODO: Draw a plot error vs. lifetime based on current absolute difference • TODO: To understand stratification.draw a plot of observed stratification vs. error vs. purity • TO:DO Double the length Qa/Qc = ½ (Qa/Qc)_0, draw predicted errors • TODO: Remove transparency correction with longer purity monitor? 17
Lifetime with 1-sigma band for relative uncertainty Uncertainty of lifetime measurement relative to each purity monitor is small Very sensitive to catch purity change caused by recirculation problems 18
Lifetime with 1-sigma band for absolute (overall) uncertainty Hints for e-lifetime stratification Absolute uncertainty 5-9% in lifetime at ~7ms, dominated by transparency correction and anode/cathode gain correction Gain uncertainty can be calibrated in vacuum à Will do so when we pull PrM Assembly out to prepare for protoDUNE-SP run2 Transparency correction uncertainty can be prevented if we have longer purity monitors 19
Are the proposed number of purity monitors per far detector module (10 total, 6 inside cryostat, 4 inline within cryogenic infrastructure) necessary to meet critical system requirements? • Two sides purity difference, understand where the contamination from à two strings on each sides, measuring purity at different heights • Monitor purity right after filling à bottom PrM • Monitor purity closer to outgas from surface à top PrM • Monitor purity in the main volume of argon à middle PrM • Needs to measure stratification • à 6 PrMs in cryostat • Two inline purity monitors, before after LAr filtering • Two as replacements for the inline purity monitors • à 4 inline PrMs 20
Cryostat Purity Monitors Two strings of purity monitor assemblies on TCO and back sides, each string mounts 3 purity monitors on a supporting tube, in total 6 purity monitors in cryostat Need straight detector port One of DN250 instrumentation ports on each side, if not available then use part of manhole on each side Similar system runs successfully in ProtoDUNE-SP Locations for Inline Purity monitors under discussion 21
Measure purity stratification • Measure purity non-uniformity and help to tune CFD model (South Dakota) 22
Inline Purity monitors 4 purity monitors outside of cryostat but within both in front of and behind the filtration system. 23
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