G-plane biasing problem on APA-3 Serhan Tufanli Turning on the - - PowerPoint PPT Presentation

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g plane biasing problem on apa 3
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G-plane biasing problem on APA-3 Serhan Tufanli Turning on the - - PowerPoint PPT Presentation

Aug 11, 2023 116 likes •187 views

G-plane biasing problem on APA-3 Serhan Tufanli Turning on the detector after Christmas break Nominal wire bias voltages 100V/cm space charge test run No tracks on APA3 APA3 APA2 APA1 collection plane Barely visible

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SLIDE 1

G-plane biasing problem on APA-3

Serhan Tufanli

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SLIDE 2

Turning on the detector after Christmas break

  • Nominal wire bias voltages
  • 100V/cm space charge test

run ○ No tracks on APA3 collection plane ○ Barely visible tracks on U plane

  • https://pdspelog.web.cern.ch/e

lisa/display/9941

APA3 APA2 APA1

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SLIDE 3

U plane signal

Barely visible tracks on U plane

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Tried to understand the reason..

  • We checked the Wiener power supply, all high voltage cables and connections on top of the cryostat. All of them were

good.

  • Changed the polarity of U plane → applied +370 V
  • We measured the capacitance of the SHV center conductor to the ground for each wire plane on APA3. While U and

X planes had 3nF capacitance, G plane had only 0.94nF. To cross-check, we performed the same measurements on APA5, and confirmed that all wire planes have ~3nF capacitance. This measurement confirms a connection problem between the high voltage cable and G plane wire biasing circuit on top of the APA. → SHV connector problem ?? Solder-joint problem?? G-plane electrically floating??

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More tests… and G plane is charging up

  • With different bias voltages run for half a day

○ Cathode = - 180 kV ○ G = off no voltage ○ U = - 370V (nominal) ○ V = 0V ○ X = 1640V (double that nominal to help pulling charge from G plane toward the sensing wires). We see tracks in induction and collection planes !!!! G-plane charging up and satisfies the transparency conditions!!! APA3 APA2 APA1

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More tests… and G plane is charging up

  • Repeat measurements with nominal voltages

○ Cathode = - 180 kV ○ G = off no voltage ○ U = - 370V (nominal) ○ V = 0V ○ X = 820V We see induction and collection tracks!!! APA3 APA2 APA1

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Conclusions, questions ..

  • We have G plane biasing problem on APA3 due to SHV connection
  • It is self-healing with G-plane charging up
  • Was SHV cable already disconnected during the beam run?

○ No visual difference in Online monitoring tool ○ Any difference in data? ■ Need input from offline data analysis