Purity Monitor Update and Plan Ilsoo Seong, Jianming Bian (UCI) - - PowerPoint PPT Presentation

Purity Monitor Update and Plan

Ilsoo Seong, Jianming Bian (UCI) Andrew Renshaw (UH) Nov 27, 2018

Purity Monitors at NP04

• Three Purity Monitors (PrMs) installed at the

different depths

• Measure the charges on the cathode and

anode, and the time of drifting e- in the PrM

• Applied HV on the cathode and anode to

drift electrons

• e- lifetime ! is calculated with
• Managing the drift time (t_drift) allows to

measure the reliable lifetime in different ranges

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Bot PrM Mid PrM Top PrM

Qanode = Qcathode e−tdrift/τ

University of California, Irvine

Purity Monitor History at NP04

• We are taking data since August 21st
• We took the data smoothly while filling and recirculating LAr
• The Bot PrM seems to have an issue with the electronics
• At the beginning, the lifetime was 45 us, and On Nov 19th, we achieved the lifetime 6.3 ms
• To achieve the lifetime a few ms level we apply the transparency correction
• PrM system alerted the NP04 system twice which helps to take early action to prevent any

potential issues

• Filter and recirculation issues

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University of California, Irvine

First Report: Aug. 31st

• On August 31st, the cathode signals are dropped and the anode signals are disappeared
• Before this issue, the lifetime was about 45 us
• The filter was saturated, the lifetime was dropped to around 35 us.

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University of California, Irvine

recirculation start Issue found

Another Report: Oct. 29th

• On October 29th, PrMs saw the lifetime drop
• Unfortunately, the PrM system had an issue, we couldn’t measure the lifetime for 1.5 days
• Once we fixed the PrM system, we measured the lifetime 3 ms dropped from 6 ms
• The recirculation pump was off à saved the beam runs

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University of California, Irvine

beam run beam run

Transparency Correction

• Typically, configure the HV to achieve 100% transparency on

the ground-grid

• When the QA/QC ratio close to 1, the uncertainty on the lifetime becomes larger

à lower HV à longer drift time à lower QA/QC ratio

• We change the HV setting à low transparency à lose electrons on the ground-grid
• Applied the correction factors to recover the charge lose: first attempt
• This new method enables us to measure the lifetime longer than 6 ms

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6.6 ms

University of California, Irvine

PrM Data in DQM

• Now the lifetime history plot and

results can be found at the DQM webpage: p3s-content.cern.ch/Monitor/PRM/ (this link is only working at CERN)

• If you want to access it outside

from CERN, please check https://wiki.dunescience.org/wiki/D QM_Shifter_Manual

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University of California, Irvine

Future Plans for DUNE-FD

• With the NP04 system, study to receive the trigger signal from the detector to operate the

PrMs between the trigger intervals

• will enable to do real-time measurement
• Design 3 different lengths of PrM to achieve the larger lifetime range
• From a few us to > 10 ms
• Future PrM system R&D
• Study the degradations of photo-cathode and optical fiber for long-term use: 10+ years
• Systematic study of transparency correction method
• Study electron recombination in LAr for different electric fields

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University of California, Irvine