Quick VPT Test Rig meeting - minutes

Date of meeting: 9 June 2000

Venue: Brunel University

Present: P Flower, H Heath, P Hobson, D Imrie, B Kennedy, L Lintern, C Pattison, O Sharif, M Sproston, J Williams

 1.  Status of RAL 48-channel test rig

• First row of 8 VPT holders glued up and mounted on baseplate.   Whole assembly has been rotated using stepper motor under control of LabView application. BWK showed pictures of the magnet and rig, and the current construction schedule.

• ALL making VPT can for noise studies - should be ready next week.
• Reed relays have arrived
• LabView magnet control works.  Current/field reading next week.
• PRH noted that the HV cables have some steel components - care must be taken when using these in the magnetic field.

2.  Status of Brunel 4T test rig

• Tour of test lab: magnet support frame is ready; magnet lab being prepared.
• The design of the 6-channel "torpedo" is in progress.
• Need crimping tool to begin cabling up first channel; will use correct cable lengths and read out via a 16-bit multiplexed 32-differential ADC (cost under £1000).
• Will use McLennan stepper motor system (same as RAL) - delivery expected by end July.  This motor can be controlled using the same LabView program as the RAL motor.
• Some discussion of data file formats.  It would be advantageous for RAL and Brunel to use compatible formats: HFH, BWK, CAXP, OOS to discuss further.

3.  CRISTAL

• HFH showed examples of the process and data structure specifications required by the CRISTAL experts to set up the database.
• PRH suggested storing data from faceplate transmission measurements in CRISTAL.  At present the db is structured in terms of an heirarchy of parts and subparts, so there is no natural way to store such information - HFH will raise the point with CRISTAL experts.

4.  Dimensioning gauge

• JHW presented a conceptual design for a gauge measuring the VPT radius and the angle of the faceplate wrt the barrel simultaneously.  Unlikely to be ready for preproduction batch, but a fast stop/go gauge will be needed when the production VPTs start to arrive.

5.  VPT Lifetime tests

• MS reported on accelerated ageing tests on two VPTs at RAL, both from the manufacturer chosen for the preproduction batch.  Output from tube 1 is still falling after 20 days at 200nA cathode current, now under 60% of original output.   Tube 2 has reached 78% output after 4 days, but seems to be flattening off.

6.  Helium study

• PSF described preliminary work on exposure of a VPT to a helium atmosphere.  After a few days in 70% He the gain is seen to rise, and the pulse develops a very long tail; gain/tail increase continues for at least 3 weeks.

Bruce Kennedy / 05 December 2003