T-474 phone conference

Monday 04 september 2006, 09:00 SLAC time, 17:00 UK time

Phone number : +1 510-665-5437
Meeting code : 0419

hardware points


analysis points

  • ...


Minutes of the T474 phoneconference
Monday 4th of September 2006

- Alex reported on his new proposal for the scheme of the calibration 
  electronics. Schemes can be found linked above. Some notes with his
  explanation :

  o the amplifiers + the switch give 80dB isolation from the source 
    when turned off
  o the power level from the calibration tone in the end station would
    be about 4 dBm, not takin into account other sources of losses
  o a powermeter, which would cost 1500 would probably be too
    expensive, so it probably makes sense to replace it with just some 
    diodes and plug the output into an ADC

- Yury suggested it would probably be better to look at high gain
  crystals for measuring the power. He also wonders about the gain
  stability of the amplifiers when they are turned on and off at 10

  --> need to get manufacturer specifications on stability and
      repeatability of gain of these amps

- Stewart brought up the issue of gain loss in the cables. Yury
  suggests we could monitor a cable in itself by leaving it
  unterminated or even better just shorted. 

- We need to put in a proposal for the cable plant to Mike. Roughly it
  would be

  o 1 long cable (~40 m) for the calibration tone, which runs from the
    counting house. We think of using 1/2 " heliax for this
  o 3 cables for the new BPM (x,y, and Q) for this we probably can use
    1/4 " heliax.
  o if we are moving BPM4, it probably makes sense to have 2 new
    cables at it's new location. 

  Yury mentioned that SLAC doesn't allow heliax cables anymore because
  of fire hazard. They would have to be replaced by so-called LMR
  cables from Times Microwave (www.timesmicrowave.com)

- Bino will have a look into implementing the VSAM data and the second
  filter into Yury's code. It was decided to create a tree next to the 
  position and tilt tree (ntp2) which impements a double filter DDC,
  however this will probably require a parallel set of DDC constants
  etc. Will look into this.

- Filimon's July 06 "good runs" list is linked from the UCL T474
  website now as Stewart suggested. THe list is at 

- Stewart mentioned the software package "SystemVue" which can be used
  for extensive electronics simulations. The website can be found at

- Yury mentioned that Mahsa is doing the geophone vibration
  measurements in the end station. She will report on the T474 eLog.
  He also mentioned that the person that was responsible for getting
  the movers for Chris' BPMs is Gordon Bowden,
  gbb@slac.stanford.edu. Need to contact him about the actuall type of 
  movers used for Chris' BPMs.

- The next meeting will be on Monday, September 18th at 17:30 UK time,
  9:30 US time. 
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