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RIE pre-production VPT Brunel tests

RIE pre-production VPT Brunel tests. Peter R Hobson with Barbara Camanzi , Derek Imrie, Mark Osborne, Christopher Selby and Omar Sharif Department of Electronic and Computer Engineering, Brunel University, UK. Automated VPT test system.

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RIE pre-production VPT Brunel tests

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  1. RIE pre-production VPTBrunel tests Peter R Hobson with Barbara Camanzi, Derek Imrie, Mark Osborne, Christopher Selby and Omar Sharif Department of Electronic and Computer Engineering, Brunel University, UK

  2. Automated VPT test system • Superconducting (persistent current) 4.0T axial field magnet • VPT gain at 4.0T relative to 0.0T measured with tube at 15 degrees to field axis • DC gain at 0.0T measured using anode and cathode currents • Pulsed gain at 4.0T and 0.0T measured using fast blue LED at 1kHz repetition rate • Data taken with Vanode = 1000 V, Vdynode = 800V • Single tube torpedo in current use, 6 VPT torpedoes under construction

  3. DAQ system A PC controls the anode & dynode HT and measures voltages and currents. This instrumentation is IEEE 488.2 based The same PC also controls a step motor via RS232, and has a 32 channel differential 16-bit ADC card for the anode signals (pulsed LED tests).

  4. The production system at Brunel GPIB control system and DAQ 4T magnet Single VPT in torpedo

  5. Relative pulsed gain The ratio of the gain at 4.0T to that at 0.0T for a tube angle of 15° to the magnetic field is a critical parameter. All but 1 tube tested (86 in first batch, 60 in second batch) pass the acceptance criterion.

  6. DC gain from automated system DC gain measured in the automated test system. Mean gain = 9.3

  7. Repeatability A number of tubes (18) from batch 1 were measured twice, usually after about a 12 hour delay. Repeatability of the system is good.

  8. Photocathode Uniformity • Photocathode response (VPT operated as a diode) measured with stable blue-violet LED (spectrum a good match to PbWO4 emission) • Repeat scans show repeatability is reasonable. Positioning errors are ± 0.5 mm and ± 3°. • Three diameter scans at 120 degree intervals. • System is now semi-automated, results are preliminary. Scanning of tubes with visual photocathode defects is underway.

  9. Photocathode uniformity

  10. Future work • Complete testing of the pre-production batch of 500 tubes • Complete construction and commissioning of the 6-VPT torpedoes • Complete the construction of the step-motor automated VPT feed system • Prepare for the production run later in 2001

  11. Conclusions • System is working • Approximately 25 tubes per working day can be tested at present, this should rise to 50 with completion of the final system (new 6 VPT torpedoes plus automated feed) • Repeatability of the relative gain at high field is very good • Photocathode scan work looks promising • So far so good, but a great deal of work to do in the next four years!

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