Towards the automation of the test of photomultiplier tubes in Barcelona

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Towards the automation of the test of
photomultiplier tubes in Barcelona

• Rafael Ballabriga Suñé
• Xavier Xirgu Aleixandre

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Introduction

• Measures performed
• Instruments and Automation
• Summary
• Future Plans
• Open Questions

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Measures Performed
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Measures performed

• Absolute Gain
• Linearity
• Scintillation Pulses Analysis
• Crosstalk

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Gain Measurement

• Two Methods have been tested
• Fitting the spectrum of large number of
  photoelectrons chosen
• 2 measures spectrum/pedestal
• Easy to compute

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Gain Measurement (Setup)
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Gain Measurement (Results)
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Linearity measurement

• Double pulse method has been used.
• Deviation from linearity expressed as

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Linearity Measurement (setup)
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Linearity Measurement (results)
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Linearity as a function of High Voltage

• Linearity is a parameter dependent on the High
  Voltage
• The aim of this measure is to study this
  dependence
• Relative linearity has been found
• A small high frequency noise has been observed
  when the LED driver is pulsed (400µV peak)

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Linearity as a function of High Voltage
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Linearity as a function of High Voltage
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Scintillator Pulse Analysis

• Objective To study the performance of the system
  Scintillator-Fiber-PMT
• A 12x12 pad has been used with 101 cmts WLS fiber
• Aiming at
• Mean number of photoelectrons/MIP
• Percentage of signal within 25 ns windows

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Scintillator Pulse Analysis (Setup I)
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Finding the fibers optimal position (setup)
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Scintillator Pulse Analysis (results)
Histogram of the number of photoelectrons per
signal
Time response waveform
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Scintillator Pulse Analysis (results)
Mean time waveform in lineal axis (time vs
voltage)
Mean time waveform in logarithmical axis (time vs
voltage) Slope-0.8768E-1 Statistics9568signals
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Scintillator Pulse Analysis (results)
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Scintillator Pulse Analysis (results)
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Crosstalk Measurement

• A measure of the system Scintillator-Fiber-PMT
• A system to position automatically the fibers in
  the cathode has been designed
• The mask used in this test places diagonally the
  fibers in the fired pixel

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Crosstalk

• Crosstalk results of two studied channels.
• 2 diagonal WLS fibers are placed in close contact
  with each channel.

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Crosstalk

• In the upper figure the fibers are placed in
  close contact with the cathode. In the bottom the
  fibers are placed 0.5 mm from the pixel.

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Instruments automation
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Instruments and automation

• 2x64 channels PMT H7546
• 2x1 channel PMT XP2262
• Light source (mimics scintillator pulses)
• 4 channel High Voltage Source
• 2x32 channel charge ADC (CAEN V792)
• PC with VME-MXI-2 interface (with LabVIEW
  software)
• 3 axis-motion stage ( X-Z motorized, Y manual)
• Oscilloscope TDS 380
• Timers, discriminators, logic units

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Some pictures of the setup
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Some pictures of the setup
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Some pictures of the setup
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Some pictures of the setup
The LED pulser
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Summary
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Summary

• The setup in Barcelona has been shown
• It is still under construction aiming at a fully
  automated system
• Some measures have been made in order to test the
  performance of the PMT and calibrate the system

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Future plans

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Future plans

• Deadline October 2003
• Reduction of the noise of the LED pulse (1 month)
  in parallel with signals analysis
• Which tests are to be performed on each PMT?
• Absolute Gain of each channel
• Tests to be performed on some PMTs?
• Linearity
• Scintillator pulse analysis (Crosstalk)

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Open questions
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Open questions

• Define the tests to be performed on each tube
  criteria to decide which cannels
• Base study status
• Aging problem
• Performance under magnetic field?
• Possibility to test in the lab a complete set of
  Scintillators-fibres-PMT