Scope Review (draft): Purity Monitors for DUNE Jianming Bian (UC - - PowerPoint PPT Presentation

Scope Review (draft): Purity Monitors for DUNE

Jianming Bian (UC Irvine)

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Scope and Motivation

• Build 6 PrMs in the DUNE cryostat, 4 standard and 2 long
• Build 2 standard PrMs within recirculation (inline), reduced

from 4 after studying diagram of recirculation system

• Detector and cryogenic operation: 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 data analysis
• Measure purity stratification
• Verify CFD

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Purity measurements

• Gas Analyzers: measure GAr purity, useful to

alarm cryogenics issues

• Purity Monitors: localized high precision LAr

purity measurements, alarm cryogenic (inline PrMs) and cryostat (cryostat PrMs) issues, also useful in recirculation studies and analyses

• TPC: use cosmic rays to measure electron lifetime

in cryostat, useful for analysis. If there are enough cosmic rays could measure electron lifetime across the detector. DUNE FD doesn’t have enough cosmic rays for this.

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Cryostat Purity Monitors

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One of DN250 instrumentation ports on each side, if not available then use part of manhole on each side

Need ports for straight deployment 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 Similar system runs successfully in ProtoDUNE-SP Locations for Inline Purity monitors under discussion

Flange for straight deployment

4X 2-3/4 CF Flanges (3-HV and signal) (1-Fiber optics) 2X 1/5” VCR (For gas fill and relief) 1X 1.33” CF Flange (Vacuum pumping) Custom support tube adapter, protect optical fibers Side view

3 X Optical feedthroughs HV feedthroughs

• Guarantee electronic and optical

connectivity

• Completed PrM assembly needs to be

tested in vacuum tube before insertion

• Quartz fibers need to be protected and

can not be bent too much

Inline Purity monitors

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2 PrMs outside of cryostat inline with cryogenics system, before and after filtration system PrM PrM

ProtoDUNE-SP Purity Monitors

Top PrM Middle PrM Bottom PrM

Individual PrMon:

• A miniature TPC
• Xe flash lamp light source
• Al-Ti-Au photocathode for drift electron

generation

• Faraday cage and optimized grounding

scheme for minimal noise pickup

• Cathode/anode readout electronics
• M. Adamowski et al., JINST 9, P07005 (2014).

Qanode/Qcathode = e-tdrift/t

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Clean LAr Distribution Dirty LAr pump

At ProtoDUNE-SP, all 3 purity monitors have same drift length, 25 cm Cathod/Anode disks, field shaping rings and grids from ICARUS PrMs

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Improved PrM Signal in ProtoDUNE-SP

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• PrM HV varied (0.25 kV-3 kV) allows for range of drift

time from 150 us to 3 ms

• Increase UV light by using 8 optic fibers for each PrM
• At ProtoDUNE-SP regular purity 6 ms, Qa/Qc = 0.7 à no

saturation

• Each PrM measurement lasts 20 seconds with 200 UV

flashes, provide high precision, localized electron lifetime

• Measured e-lifetime at ProtoDUNE-SP: 35us - 8 ms

ProtoDUNE PrM signals at e-lifetime = 6 ms

Charge Questions

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• How was output from the purity monitors used in ProtoDUNE and for which
• perational phases was the data collected critical?
• Is the purity stratification observed within the ProtoDUNE-SP cryostat real

and if so, is this consistent with initial purity measurements from cosmic rays?

• 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?

• 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?

• Do the purity monitors need to be designed to operate over the full lifetime of

the experiment?

• Are the proposed mechanisms for supporting the monitors within the cryostat

and connecting them to the outside of cryostat mechanically sound and cost effective?

• 1. How was output from the purity monitors used in

ProtoDUNE and for which operational phases was the data collected critical?

• July 23 - Sep 29: Continuously (hourly) monitor LAr purity during
• filling. Data taking started when bottom PrM fully submerged in
• LAr. Found saturation of LAr filter during filling —> report sent to

cryogenics team and filter cartridges regenerated

• Sep - Dec 2018: Monitor LAr purity a few times per day during

beam data taking period. This alerted the experiment to several problems: recirculation pump stoppages, false alarms, problems from the cryostat level gauges. This prevented situations which

• therwise would have gone unnoticed for some time, with severe

consequences to the ability to take data. Neither the gas analyzers nor the TPC caught these problems in time.

• Sep 2018 - Present: Monitor LAr purity during cosmic ray data
• taking. Provides a benchmark for LAr purities for recirculation

studies and TPC calibration by measuring the e-lifetime for the TPC.

• Critical to LAr filling, commissioning and data taking

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Monitor LAr Purity during filling

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As soon as the lowest purity monitor was immersed: ~40 us -> 7.5 ppb O2eq On Thursday 30st of August purity was compatible with ~60 us Cathode signal Anode signal ProtoDUNE-SP: On Friday 31st of August, 2018 the purity of the bulk liquid argon dropped from 40 us purification cartridges needed to be regenerated. Regeneration took till the 3rd of September. Filling restarted immediately after. Filippo Resnati - DUNE Collaboration Meeting - CERN - 28th January 2019

Monitor purity during LAr filling, find saturation during the filling

Monitoring LAr Purity During Operation

13 Relative lifetime uncertainty only

Purity drops (dips) during ProtoDUNE-SP operation caught by purity monitors. Reasons

• f purity drops include recirculation pump stoppages, false alarms, and problems from

the cryostat-level gauges

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Purity from PrMs as benchmark for cryogenic operation and recirculation studies

Lifetime for TPC calibration

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• Cosmic rate is low in DUNE FD, and cosmic ray based TPC calibration needs to add up

many cosmic ray runs taken at different periods à Choose TPC cosmic runs under same PrM purities for e-lifetime calibration

• PrM-TPC combined lifetime measurement

Purity Monitor TPC Cathode Anode Cathode

• 2. Is the purity stratification observed within the

ProtoDUNE-SP cryostat real and if so, is this consistent with initial purity measurements from cosmic rays?

• See hints of purity stratification: Purities measured by PrMs are different at

different heights. Purities became more consistent when pump and venting stopped.

• But, still need to cross calibrate systematic differences between PrMs to

confirm if stratification is real. For ProtoDUNE-SP, the calibration will be done in the long vacuum tube in ENH1@CERN when we pull the three purity monitors out to prepare for ProtoDUNE run-2

• The small statistic uncertainty give PrMs potential to make stratification with

high precision, see answers to Q3.

• TPC lifetime measurements affected by statistics, space charge effects and other

non-uniformity issues, therefore, until now ProtoDUNE-SP TPC hasn’t provided consistent electron lifetime measurements, and there is no purity stratification measurement reported from TPC

• There are people considering alternative ways of generating free electrons such

as UV LEDs in a photocathode or radioactive sources. These would allow movable devices and reduce the systematics of the stratification measurements

16

Lifetime with 1-sigma band for absolute (overall) uncertainty

17 Absolute uncertainty 5-13% 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

Hints for e-lifetime stratification

Lifetime for Cryogenic System Studies

Mar 12, 2019 18

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

Ilsoo Seong

PrMs are sensitive to purity change Typically no regular TPC data when testing recirculation

Lifetime Ratio compared with Mid PrM

Ilsoo Seong 19

P1 P2 P3 P4 P5 pump stop pump off All boil-off vented pump off All boil-off GAr condensed and returned

• When the pump was off (no flow), the lifetime difference getting smaller

PrM vs. TPC e-lifetime

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Bottom PrM Mean = 4.85ms RMS = 0.19 ms Mid PrM Mean = 6.20ms RMS = 0.40 ms Top PrM Mean = 6.99ms RMS = 0.36 ms TPC lifetime 2, One run taken in a few hours, each entry is lifetime from one cosmic track Mean = 6.1ms RMS = 2.0 ms PrM : 200 flashes/measurement TPC lifetime 1 Mean = 4.6, 6.1ms RMS = 1.0, 1.4 ms

• PrM e-lifetime stat error is much smaller than TPC because it measures

localized purity with large statistics

• Electron lifetime: tau = 1/kA*ns , where kA is the electron attachment rate

and ns is the concentration of a certain type of impurity. Attachment rates kA at different E-fields are different. Since PrM and TPC operate at different HVs, electron lifetime and Qa/Qc measured by PrM and TPC are different.

• Lisa Lin and Tianle Liu (U Chicago) and Tingjun Yang (Fermilab)

developed a PrM-TPC combined analysis to cancel SCE in TPC and obtain PrM/TPC lifetime difference (Qa/Qc)TPC/ (Qa/Qc)PrM = 1.05-1.07

• After this correction, PrM e-lifetime is ~11 ms, consistent with TPC

lifetime estimate 12 ms made by Flavio and Xiao

Craig Thorn, Compendium of LAr properties," LBNE-Doc-4482-v1 , Xin Qian, Requirements on Purity Uniformity, 2017/04/18, FD Meeting Flavia Cavanna , Xiao Luo, A new model for Ion transport and Space Charge field distortion, Model predictions on experimental

• bservables; Tianle Liu, Lisa Lin, Lifetime study - 2019 May DUNE

collaboration meeting:

• 3. 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 and cryogenic operation (relative measurement):

• (almost) No limitations to relative measurement from the current

design

• 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 < (100%-5*1%)

= 0.95, equivalent to ~42 ms lifetime for regular PrM drift time 2.2ms

• PrM’s high sensitivity of catching purity change is proved in

ProtoDUNE-SP, when pump or venting stopped at high purity, PrMs immediately saw the electron lifetime change

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• 3. 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 absolute lifetime measurements:

• Current PrM design and calibration: Systematic uncertainty is up to 13% in lifetime (3.8%

in Qa/Qc) at 7 ms (equivalent ~10 ms in TPC)

• With current design at ProtoDUNE-SP, to make 2.2ms drift time, PrMs are run with a low

anode/cathode HV ratio, so a transparency correction is needed to correct electron loss in the grid. The correction is based on two PrM runs taken at high HV (full transparency) and low HV. The statistic uncertainties in the two runs cause an major systematic uncertainty in Qa/Qc. The proposed 4 x longer purity monitor can remove this uncertainty.

• Another large systematic uncertainty is anode/cathode gain difference, which can be

reduced by calibrating PrMs cathode/anode gains with signal generators.

• Current PrM design, with anode/cathode gain calibration, up to 7.5% in lifetime at 7 ms
• 4 x long purity monitor, no transparency correction uncertainty, with anode/cathode

calibration: up to 4.5% in lifetime at 7 ms.

• In TPC, maximum energy loss at 7ms lifetime is ~27%, dQ/dx uncertainty due to lifetime

measurement will be 4.5%*27% = 1.2%,

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Source Bot Mid Top statistical error of QA/QC in single run 0.13% 0.15% 0.12% % in QA/QC QA/QC fluctuation b/w runs 0.63% 0.74% 0.52% % in QA/QC statistical error of drifttime 0.02% 0.02% 0.02% % in tdrift cathode rise time trise

C

0.12% 0.03% 0.02% % in trise

C

anode rise time trise

A

0.40% 0.15% 0.17% % in trise

A

cathode RC time constant tRC

C

0.22% 0.18% 0.14% % in tRC

C

anode RC time constant tRC

A

0.80% 0.24% 0.10% % in tRC

A

gain uncertainty 3.63% 2.32% 0.76% % in QA/QC transparency correction 0.91% 1.79% 1.26% % in QA/QC

Uncertainties

• Included the run-to-run variations as a systematic error
• Note that the table shows the relative error of each source, not the lifetime

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τ lifetime = − tdrift log QA QC f RC

A

f RC

C

ftrans !

Relative uncertainties, affect sensitivity to catch purity change

Uncertainty of Lifetime at 7.0 ms Bot Mid Top Relative measurement 2.04% 2.63% 1.68%

Uncertainty of Lifetime at 7.0 ms Bot Mid Top Total Uncertainty 12.87% 11.39% 5.08%

Limitations of purity measurement

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Uncertainty in Lifetime (%) Uncertainty in Lifetime (%) Uncertainty in Lifetime (%) Uncertainty in Lifetime (%)

Relative uncertainty 1.7-2.6% at 7.0 ms (eq. ~10ms in TPC) Limit (Qa/Qc 5s from 1): 42ms

4-7.5% at 7 ms (eq. ~10ms in TPC)

5-13% at 7ms (eq. ~10ms in TPC)

2.5-4.5% at 7ms (eq. ~10ms in TPC) Relative Uncertainty vs. lifetime Current absolute Uncertainty Absolute Uncertainty, with anode/cathode calib.

Absolute Uncertainty, long PrMs, with anode/cathode calib.

• 4. 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? 6 PrMs in cryostat

• After reviewing the recirculation diagram, we found the number of of

designed vessels for inline purity monitors is 2 instead of 4. So per far detector module we need 8 PrM total, 6 inside and 2 inline.

• DUNE FD is huge, liquid argon takes hours to flow from one side to the
• ther side. Using strings on opposite side of cryostat will help inform

where contamination is coming from if measurements are different.

• For each string measuring purity at 3 different heights
• Monitor purity right after filling à bottom PrM
• Monitor purity closer to outgas from surface à top PrM
• Monitor purity at mid-point of the cryostat heightà middle PrM
• Measure purity stratification

2 inline purity monitors, before and after LAr filtering

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• 5. Do the purity monitors need to be designed to operate over the full

lifetime of the experiment?

• Because purity is essential to DUNE’s operation and data taking, we need inline

PrMs on the input and the output argon to operate over the full lifetime of DUNE.

• There will be cryostat PrMs and inline PrMs. Inline PrMs can be replaced and

hence can be maintained to operate over the lifetime of the experiment

• Cryostat PrMs are critical for the LAr filling, detector commissioning and

understand impurity distribution which can be done in the first few years.

• From ProtoDUNE and other experiments, it has been sufficiently demonstrated that

PrM can operate for these phases for the first few years of DUNE running.

• It will be very useful to have cryostat PrMs to identify problems and measure

electron lifetime in cryostat in long term running, but it is not an absolute requirement since we have inline PrMs to alert cryogenic accidents and to extrapolate purity from recirculation system to cryostat after mapping impurity distributions correctly

• Developing methods to extend lifetime of PrMs, but DO NOT need to re-design the

them to achieve longevity

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• The major issue that prevents purity monitor’s long term running in

ProtoDUNE is photocathodes degradation

• There has been some understanding of cathode degradation from

ProtoDUNE experience. We found that photocathode degradation only happen when operating purity monitors with high frequency in low purity LAr for recirculation study, daily running doesn’t degrade photocathodes

• Therefore, understanding the operation and purity conditions that makes

PrM cathode degrade and setup long-term PrM operation rule will allow cryostat PrMs run for long term

• We have three purity monitors on each side, this will provide good

redundancy for long-term running of at least one purity monitor in each side

• We can use inline monitors (that can be replaced) for recirculation studies

instead of the cryostat monitors to avoid degradation. This can help improve the longevity of the cryostat monitors.

• Will develop methods to use high frequency UV and heat to recover

photocathode

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• 5. Do the purity monitors need to be designed to operate over the full

lifetime of the experiment?

ProtoDUNE-SP top PrM Cathode Signal over time

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At ProtoDUNE-SP, we found that photocathode degradation only happen when operating purity monitors with high frequency in low purity LAr, daily running doesn’t degrade photocathodes

Recirculation study when purity was low (<3ms) and PrMs ran with high frequency (every 10min-1 hour)

• 6. Are the proposed mechanisms for supporting the monitors

within the cryostat and connecting them to the outside of cryostat mechanically sound and cost effective?

• According to ProtoDUNE-SP, the supporting mechanism is robust.

PrM supporting tubes are mechanically connected by the flange and directly threaded on mounting disks on each purity monitor, which is easy to install and very strong

• The supporting infrastructure on the top of the cryostat is minimal

and all robust.

• The mounting tubes protect quartz fibers and the assembly Since

DUNE FD is deeper, we will increase the thickness of the support tube and add extra strengthen rods to guarantee mechanical strength, if the space above flange is not enough, joints are needed

• ProtoDUNE-SP doesn’t have inline purity monitors. DUNE inline

PrM supporting structures will follow 35t and LAPD inline purity monitors.

• Overall cost estimate for mounting structure is $11k, based on

ProtoDUNE-SP experiment. Machine shop cost takes about half

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Mounting structure of ProtoDUNE-SP PrMs

• Fibers are contained within support tube, so no worry

about breakage in installation

• Cables will be tied to the support tube
• The entire assembly including the top flange and the

support structure will be tested in vacuum tube before insertion

• After assemble PrMs on support tube, check

electric/optical connections in every step during insertion

Support tube adapter on flange Support tube contains a 0.5” inner tube to contain fibers Hole to vent gas during filling Electric Cables fixed

• n the support tube

with cable ties Bolt hangs support tube

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Backup

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Lifetime for TPC calibrate

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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. Since PrM and TPC operate at different HVs, electron lifetime and Qa/Qc measured by PrM and TPC are different. 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

Craig Thorn, LBNE-Doc-4482-v1, Xin Qianhttps://indico.fnal.gov/event/14296/contributio n/0

DUNE CFDs

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South Dakota simulation Erik A Voirin DUNE-doc-1046-v2 CISC meeting, 5/9/2019

Purity Monitor Components

• Build 8 PrMs
• Build electric and optical feedthroughs
• Build two mounting structures and top flanges
• Build FEB Electronics
• Prepare DAQ system
• Xenon light sources with Faraday cage
• HV and LV delivery to PrMs and electronics

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Electronics

04/26/17 ProtoDUNE-SP Cryogenics Instrumentation Review 36

Purity Monitor Electronics Type 2, Two Channel

• 12 V

• 6 V

• f amplifier. This resistor effects both gain and low frequency roll off.

• 6V

• cerm. disc

• 6V

HV and optical Feedthroughs

HV Feedthroughs: ~ 10kV Optical Feedthroughs:

HV and Slow control

• Programmable HV
• Relay board for NIM bin (PrM electronics)
• Relay board for DC power supply for the light source/or Programmable DC

power supply for the light source.

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Light source

• Hamamatsu Xenon source (1J/flash)
• Faraday cage for grounding

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PrM electronics Signal: 2 channels – cathode, anode < 5V PrM HV Cathod -150V Anode 2500V DAQ PC 110V Digitizers NIM Bin 110 V

DAQ

Need to Develop slow control

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Trigger

• Photo Diode to trigger the

digitizer

• Trigger signal also to

TPC/PDS DAQ to prevent possible noise from purity monitor

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To TPC/PDS DAQ

DP purity monitors

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Total 8 monitors (6 cryostat and 2 inline)

Test PrMs in long tube

• After assemble PrMs on long supporting rods, test the full

assembly in vacuum

SS tube Stephen, Filippo

• After assemble PrMs on long supporting rods, check

electric/optical connections

• Move the PrM assembly to the corridor
• Use crane, lift and rotate the assembly 90 degrees
• Use crane, move the assembly to the top of the port
• Use crane, start to insert the assembly into the port
• Test connections on each PrM vertically during insertion
• After insertion, test overall resistance and capacitance with

electrometer and Capacitance Meter meter

• Mount NIM bin and Xe flash lamp on the PrM.
• Connect cables
• Connect optical fibers to Xe flash lamp
• Make connections to power supplies and slow controls

interfaces

Installation procedure at ProtoDUNE-SP

Check connections one by one during insertion

Crane Port Use multimeter to test connectivity to feedthrough/topflange for cathode, anode, anode grid and ground with faraday cage Insert slowly, stop when checking connections If fibers are not closely attached to the cathode surface, open the side window of the Faraday cage and tune Testing cables x 9 UCI sling <150 lbs