Quick VPT Test Rig meeting -
minutes
Date of meeting: 16 August 2000
Venue: RAL
Present: D Cockerill, P Flower, P Hobson, B Kennedy, L Lintern, M
Sproston, A Turner, J Williams
- Status of Brunel test rig
- PRH reported that the superconducting magnet has now been reset to
4.000T, and moved to the test lab.
- Rate of He loss is about 100 litres gas/day - not regarded as a
problem as the room is adequately ventilated.
- Need to refill with He 3 times per year, refill weekly with
nitrogen.
- New DVM works.
- Awaiting GPIB isolator for anode current measurements (expected Aug
24).
- Awaiting MacLennan stepper motor system.
- Plan is to leave current manual system running for the initial batch
of 100 VPTs, and commission the automated system later.
- Possible problem with RG174 HV cable, which is Cu-clad
steel. PRH will measure force on a typical cable in the magnetic field.
- RAL test rig - mechanics
- Rail system partially assembled - awaiting delivery of nylon rod for
sliders.
- Electronics
- Anode current leakage box needs a few days work to finish - ALL is
on leave for most of August from 21st onwards, but will try to complete the box as soon as
possible.
- ALL will wire up 8 more bases for experiments with various LEDs.
- 428nm LED is suitable for RAL - OK for Brunel provided powerful
enough for 7-way fibre-optic fanout. PRH and MS will decide what LED to use, and
place an order.
- Another 5 preamp channels and associated motherboards received from
Bristol. DJAC has brought another 25 channels from CERN, which can be used after
some refurbishment. Summer 2000 test beam supercrystal will soon arrive back from
CERN, including 30 more preamp channels. Combining all of these gives more than
enough preamps for the 48-channel test rig.
- Discussion of measurement details
- All measurements made at Va = 1000V, Vd =
800V.
- RAL measurement cycle will be as follows: dark current @ 0T +
pedestal; pulsed response @ 0T + pedestal; field to 1.8T, wait for temperature to
stabilise; pulsed response v angle (-30o, then 5o steps to +30o,
return to 0o) with continuous leakage current monitoring; magnet off; remeasure
pulsed response at 0T; reverse magnetic field and repeat (for a sample of VPTs);
categorise VPT as good/borderline/bad. Brunel will follow the same cycle, with the
angle always at 15o and the field at 4T.
- A random selection of good VPTs will be selected for destructive
testing; the remainder will go to the Regional Centre for assembly into supercrystals.
- Other issues
- Insurance: PRH pointed out that a batch of 1000 VPTs at about 50SF
each represents a considerable investment, and it might be a good idea to take out
insurance against accidental damage or loss. This has not been the practise in
previous experiments. No decision was taken either way.
- VPT passport: on receipt, Brunel will check that the passports
supplied correspond to the VPTs. JHW will scan the passports for the VPT web
site. The passport data must be extracted somehow and added to the testing
database. For the preproduction batch there is no alternative to paper
passports, but an electronic form would be preferable for the large-scale production
phase.
- Test database: BWK will look into alternative databases.
- Single pins for flying leads: agreed to purchase D-connector pins
and matching sockets. MS will order sufficient for the first 500 VPTs. These
pins should be readily available to the VPT manufacturer for the main production run.
- Bar codes: various items (eg VPT test stations, packing boxes) are
likely to need bar codes outside the CMS coding system. JHW will investigate.
- AOB
- DJAC will visit Brunel next week to see the 4T test rig.
Bruce Kennedy / 05 December 2003