TEST SETUP FOR HF PMT AT IOWA LAB

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TEST SETUP FOR HF PMT AT IOWA LAB

• CMS HCAL Meeting
• FNAL, November 16-18
• Y. Onel
• U. of Iowa
• W. Anderson
• Iowa State U.
• D. Winn
• Fairfield U.

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 Hardware and Software Tools for Test and
Calibration of HF PMT 

• The hardware system for the quality control of HF
  PMT at delivery will be installed at UI CMS lab.
• Test Station Components
•  
• 1 - Light sources LASER, LED, Radioactive
  sources Scintillators
•  
• 2 - Light-tight Test Box
•  
• 3 - Readout Electronics
•  
• 4 - Data Acquisition, Analysis and Storage PC -
  controlled System
•  

UI CMS HF Test Lab
Electronics
Light-tight
Laser Bench
Racks
Test Box
Scope
5 m
PC
Storage Cupboards
6 m
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Tasks of the Test System

• HF PMT Quality Control, Calibration and
  Monitoring System should address the following
  items
• label and catalogue each PMT at delivery and
  storage (StorageIN)
• mechanical assembly with HV power supply and
  base
•  installation in Test Box individually or in
  groups (6 - 9)
• measure (a) - gain vs HV G-HV
• (b) - pulse shape PS
• (c) - single photoelectron response SPR
• (d) - noise and dark current N/DC
• (e) - photocathode uniformity PCU
• (f) - linearity of response LR
• (g) - pulse rate dependence PRD
• (h) - quantum efficiency vs wave-length
  QE-WL
• (i) - timing response and intrinsic delay
  TR-D.

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Procedures for measurements

• The following sequence of measurements will be
  performed for each PMT
• 1 - PMT's installed in Test-Box are let to
  stabilize at standard HV
• 2 - Check of normal operating conditions
  source scint.
• 3 - Noise and dark current measurements vs.
  HV
• 4 - Gain vs. HV laser
• 5 - Single photoelectron level
• 6 - Linearity for 1- 2000 p.e.
• 7 - Rate dependence for 0.1 - 40 Mz LED
• 8 - Photocathode uniformity
• 9 - Quantum efficiency (300-600 nm) dye
  laser
• 10 - Pulse shape measurements at nominal HV.
• According to specifications of the PMT
  (manufacturer's data sheet and preliminary
  measurements on a test sample) and requirements
  of HF application (Nphe/GeV, dynamic range, etc.)
  the test setup working conditions will be
  adjusted in a range of light yield and
  sensitivity appropriate for the standard test
  procedure. Three light sources will be used for
  the specific measurements
• - laser
• - LED
• - Rad. sources radiator

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(a) Gain vs HV G-HV

• The signal charge QA at the PMT anode for a pulse
  of Nph photons of w. l. l hitting the
  photocathode of quantum efficiency h(l) is
• QA G(V) h(l) Nph qe
• where G(V) is the PMT gain, h(l) Nph Nphe is
  the number of photoelectrons (charge qe) at the
  cathode. For fixed illumination (ltNphegt
  const.), the relation ltQAgt A Vk determines k.
• At any voltage V, and fixed illumination (ltNphegt
  const.), A is related to ltQAgt/ltNphegt qe
  DQA2/ltQAgt, where ltNphe gt is estimated as
• ltNphe gt (1d) (ltQAgt/DQA ) 2
• d 0 for pure Poisson photoelectron distribution,
  d 0.25 taking into account first dynode
  collection efficiency and SER DQA is the RMS
  spread (0.85 HWHM) of the anode charge QA
  distribution (see SER measurement).
• Measurements of gain vs HV can be performed with
  laser, LED, or source radiator. The HV supply
  settings are stepped through the useful HV range
  for the PMT via computer control and pulse
  amplitude distribution measured with ADC.

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(a) Gain vs. HV G-HV
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(b) Pulse Shape PS

• The pulse shape (characterized by rise-time TR
  and FWHM of anode signals) is measured on a
  digital scope with PMT illuminated with a
  radiator and b-source. The digitized pulse shape
  is recorded.

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(c) Single Photoelectron Response SPR

• The light yield is set to a low level, in such a
  way that there is no count in the majority of
  cases for instance, with 80 missing counts,
  according to Poisson statistics, approximately
  90 of the residual counts in these conditions,
  should correspond to single phe.

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(d) Noise and Dark Current N/DC

• Dark current is measured at various HV settings
  with a picoamperometer, recorded with the PMT in
  stable temperature conditions and after a period
  ( 1/2 hour) in dark. Noise spectrum is obtained
  in same situations by measuring ADC pedestal
  spectrum, and subtracting the electronic noise
  contribution.

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(e) Photocathode Uniformity PCU

• The uniformity of response for the photocathode
  is measured by having an illuminating spot (typ.
  1mm diam.) spanning the photocathode surface (via
  a fiber moved with a scanning table) and
  recording pulse amplitude at each position.

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(f) Linearity of Response LR

• The light yield on the photocathode is varied
  over a wide range and PMT response measured as a
  function of light intensity various methods can
  be used to provide different light levels
  calibrated filters, diaphragms, etc. the
  variation of light yield is monitored with linear
  (photodiode) devices the effective steps in
  illumination can be checked and adjusted at low
  light levels, using wide dynamic range ADC (or
  proper attenuation/amplification).

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(g) Pulse Rate Dependence PRD

• The pulse rate dependence is measured with (a
  group of) LED (of equalized yield) mixed in a
  light manifold over a certain range of pulse
  rates, the frequency of LED can be varied
  individually without change of the light pulse
  amplitude or duration for higher frequencies few
  LED, feeding a light mixer, can be pulsed
  together, with short relative delays, thus
  producing a high frequency (defined by the delay)
  pulse train. Alternatively one LED can be pulsed
  for long times with an average light yield
  reproducing the amount of photons of a high
  frequency burst, and short pulses from another
  LED are analyzed as a function of the average
  current load produced by the first LED.

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(h) Quantum Efficiency vs. Wavelength QE-WL

• The response of PMT is measured with definite WL
  of light (of known intensity).
•  
•  

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(i) Timing Response and Intrinsic Delay TR-D

• The PMT is illuminated with radiator/scintillator
  excited with rad. source the time response of
  the PMT and its transit time are measured with
  respect to a calibrated counter viewing the same
  light source.

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• Measurements will be performed at stable
  (controlled) temperature. For each delivery
  batch, sample measurements will be performed for
  temperature and magnetic field dependence.
• The data for each PMT will be stored in
  appropriate archive files on disk and copied to
  permanent storage media. For each PMT an entry
  will be printed and logged to a general PMT
  directory and test logbooks.

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• The PMT's, conforming to acceptance criteria,
  will be sorted in classes and stored (Storage
  OUT), ready for installation. Those not
  conforming will be returned to the manufacturer.
• All measurement procedures will be automated and
  computer-controlled, to minimize individual
  biases and interventions daily test shifts will
  be supervised by an expert, who will also review
  the archived data of the day and certify their
  validity.

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Electronics

• The electronic system for the Test Setup
  includes
• 1 - Pulsers for the Laser, LED and calibration
  pulses
• 2 - Digital control circuits for
• - HV and LV power supplies,
• - Laser parameters and settings,
• - Stepping motors for moving parts in
  Test Box,
• - Probes for temperature, etc., in Test Box
• - Safety circuits on door, sliding
  mechanics, etc.
• 3 - Trigger logic for DAQ, monitors and gates
• 4- ADC and TDC for amplitude and timing
  measurements
• 5- Digital Oscilloscope for measuring and
  recording pulse shapes

Electronics block diagram
PMT's, Monitors, etc.
PMT's, Monitors, etc.
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Test Box

• The Test Box assembly consists of  
• 1 - PMT holder support with position remote
  control
• 2 - Optical Manifold (O. M.) providing fiber
  coupling to individual PMT's and receiving light
  from
• a - laser system with variable wavelength
  (dye),
• b - LED system pulsed at high
  frequencies,
• c - Radioactive sources scintillators
• 3 - Monitoring and control devices.

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• The Test Box is a light-tight and
  temperature-stabilized chamber 60 (H) x 60 (W) x
  120 (L) cm3 containing precision
  remotely-controlled slides, supporting the PMT's
  holder and the assembly for O. M. and fibers
  coupling to the PMT's it provides a number of
  sealed cable inlets and outlets for PMT signals,
  HV and LV and control signals as well as for
  fibers from the Laser system.

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DAQ System and Measurement Strategy

• The following sequence of measurements will be
  performed for each PMT
• 1 - PMT's installed in Test-Box are let to
  stabilize at standard HV
• 2 - Check of normal operating conditions source
  scint.
• 3 - Noise and dark current measurements vs. HV
• 4 - Gain vs. HV laser
• 5 - Single photoelectron level
• 6 - Linearity for 1- 2000 p.e.
• 7 - Rate dependence for 0.1 - 40 MHz LED
• 8 - Photocathode uniformity
• 9 - Quantum efficiency (300-600 nm) dye laser,
  source scint.
• 10 - Pulse shape measurements at nominal HV.

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Quality Assurance

• At the manufacturer
• testing/preselection as they arrive
• beam/calibration tests during the installation
  period
• we will eventually have two test stations for
  testing
• PMT can be replaced
• any PMT will function within 20 of any other PMT

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Data Acquiaition System (DAQ)

• We have VAx3200 (with backplane) which is a
  functional DAQ system with CAMAC
• We have also purchased the interface cards and
  software for the mobile DAQ which is LabView
  based
• We have U. of Iowa matching funds to purchase the
  components of the fixed PMT test station

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Manpower and expert team to install the test
system

• UI
• U. Akgun
• A. Ayan
• P. Bruecken
• J.P. Merlo
• M. Miller
• Y. Onel
• I. Schmidt
• A. Tauke
• R. Vogel
• post-doc (to be named)

• ISU
• W. Anderson
• Fairfield U
• P. Winn
• International Team
• E. Gulmez Turkey
• A. Penzo Italy
• M. Zeyrek Turkey

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Test Team

• Post-doc (supervisor)
• M. Acar (graduate student)
• P. Bruecken (Quarknet lead teacher)
• A. Kocbay (graduate student)
• Bettendorf H.S. seniors (2)
• UI undergraduate (2)

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Tests required of the vendor on each tube

• Determine the cathode luminous sensitivity with a
  tungsten filament lamp with a color temperature
  of 2856K.
• Determine the cathode blue sensitivity with a
  2856K tungsten light filtered through a Corning
  CS5-58 filter ground to half stock thickness.
• 2a. Alternatively the vendor may measure and
  report the quantum efficiency of the tube at
  420nm.
• Determine the voltage at which a current gain of
  5x105 is reached.
• Measure the dark current at a current gain of
  5x105.

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Additional tests

• Our institution/university is interested in
  having additional selection tests performed at
  the vendors site. The vendor is invited to
  submit a proposal for PMTs with the following
  additional measurement made at the vendors site.
• The vendor shall determine the pulse height
  resolution at a gain of 5x104 using the following
  method or some other method agreed on between the
  University and vendor.
• The PMT pulse height resolution shall deviate
  less then 30 from the ideal resolution (defined
  as sigma/mean equal to 1/sqrt(t) where Npe is the
  average number of photoelectrons produced by the
  photocathode for a given light pulse intensity)
  at a current gain of 5x104. The vendor and
  University shall agree on an appropriate test to
  determine that this resolution specification is
  met.