HPD Project Status

1
HPD Project Status
Stephan Eisenhardt on behalf of the RICH
group LHCb planary, CERN, 10.03.2006

• Status of HPD Production
• HPD Test Results
• Conclusions

2
HPD Production Status
Expected
today
3
HPD Production Details

• order of 65 spare HPD green light given ?
  total 485 65 550 HPD
• bump bonding of anodes (VTT) completed
• 160 still to be tested at CERN, 90 yield so far,
  expect 50 spare wrt. needed (550 10)
• gold plating of carriers at CERN on track
• one bath of 40 to go, next shipment of 120
  carriers to HCM in March (to complete the 485)
• packaging of assemblies runs smoothly
• next shipment to DEP (120) in April, 50 tested,
  yield gt90
• in total three more shipments needed to cover 550
  HPD
• HPD production (DEP) according to schedule,
  gives high quality tubes
• 160 HPDs delivered (136 Scotland, 15, CERN, 9
  pre-production)
• output 30 HPD/month
• recent problem 9 HPDs showed missing columns at
  DEP tests
• under investigation too early to draw conclusion
• ? DEP now is back to production speed, producing
  good HPDs, overall schedule not affected

4
HPD Tests

• Photon Detector Test Facilities (PDTF)
  (Edinburgh Glasgow)
• test rate 1 HPD / day / site
• 2 test stations per site
• Quantum Efficiency (Edinburgh) and Backpulse
  (Glasgow) measurement setups for 10 of HPDs
  under commission
• stable software for data acquisition
• ongoing improvements on data analysis software
• highest priority database for test results

PDTF station
5
HPD Test Profile
results up to 25.02.2006
136
109
PDTF delivered 136 tested 109 pass 104 fail
5 _at_ CERN delivered 15 accepted
14 rejected 1 pre-production 9
76
today
6
Mechanical Tests

• 107 HPD passed, 2 HPD failed
• 2 leaned by 0.4mm
• (Tower of Pisa)
• ? tubes rejected
• sent back to DEP for repotting

point of first possible contact
mechanical test jig
HPD ? 83.0mm (0.0mm, -0.1mm) Teflon tape
0.1mm Jig ? 83.4mm
gap 0.1mm
any contact failure
7
Quantum Efficiency

• Excellent blue sensitivity _at_ 270nm
• Reasonable low red sensitivity _at_ 800nm
• anti-correlated to blue sensitivity
• cause of thermal e--emission (dark count)
• Setup for independent verification at PDTF is
  under commission

8
Leakage Current

• typical value is 1mA (within specs)
• class of 8 HPD with LCgt5mA
• 7 still perform fine
• 1 did not properly deplete (LC25.1mA)
• ? tube rejected

3 HPD with 3 bake-outs all LCgt10mA
?
rejected
?
rejected
? Dec 05 bake-outs lt2
9
Dark Count

• no dark count problem
• light leak fixed after last LHCb week
• all affected HPD remeasured
• contractual specs DC lt 5kHz/cm2
• safety margin factor 1000
• before we exceed 1 occupancy
• 16 out of 124 HPDs exceed 5kHz/cm2
• two types
• high red sensitivity
• increased IFB probability
• perfectly fine to be used in RICH
• 1 HPD showed problem (H546002)
• DC gt 400 kHz/cm2
• intermittent strong ion feedback
• 3 times baked out
• ? tube rejected

contract spec

• max
• 5kHz/cm2

rejected H546002 DC gt 400 kHz/cm2
including 15 CERN HPD
10
Ion Feedback

• due to e- ionising residual gas atoms
• ? ion produces bunch of photoelectrons at PC
• ? cluster of hits with 200-300ns delay
• we find very low IFB ? very good tube vacuum

HPD response to LED pulses with varied delay
contract spec

• max
• 1

ltIFBgt 0.03
Very low IFB ltlt1
11
Tube Classification

• guideline for usability in RICH
• class A clear pass in all aspects
• class B may fail specs, but recommended for
  usage
• HPDs with slightly increased dark count
• class E flagged with an issue, still usable in
  RICH
• HPDs with increased LC or 15 dead pixels
• class F clear fail ? reject
• 5 failed HPDs
• 2x mechanics Tower of Pisa
• hope to recover
• 1x anode failure
• 1x intermittent IFB
• 1x pixel chip failure
• (not discussed here)

pass 104 of 109 gt95
fail 5 of 109 lt 5
12
Conclusions

• bump bonding completed
• anode production on track
• DEP is delivering high quality HPDs
• at a rate of 30 HPD / month
• we keep up with testing
• at a rate of 1 HPD / day / site
• gt 95 pass rate
• only very few HPD with minor issues
• excellent Quantum Efficiency
• very good tube vacuum