4.28.2014 Meeting

Agenda:

- Update on beam line installation - François

- Continue discussion of "Beam on Initially procedures."

Below you will find section G) and H) - last week time ran out of time before we finished these two sections. In particular, I would like to understand better the comments made last week about "timing". 

1) Timing of the ECal wrt the beam. Is this necessary or do cable lengths, etc. insure accurate timing. What timing accuracy is required? What is the time between fine structure in the beam due to cavity bunching in CEBAF. Is this small compared to 25 nanoseconds. Can we run CEBAF so that only one cavity bunch comes to the HPS at some repetition rate and use that to verify the ECal timing is centered on the beam? Or, does it even matter?

2) Timing of Silicon detector wrt to ECal. I suspect this is critical and needs to be timed in to within some fraction of 25 nanoseconds. How is this done (it is not a beam-line issue, but I am interested)?

- Status of HPS PC collimator material: Has it been sent?

a) Dieter recommends using another tungsten type materials, like W-26Re, or W-Ta alloys that are machinable and still have a Z that is about the same as W.  Dieter has the material and can ship it to you. It may be easier to machine the 3mm and 2 mm slits out of one piece (say 3cm by 2.5cm - 1 cm thick) than use three separate pieces. 

2 May 2014

b) Do we need a slit collimator in front of the thin gold foil?

- Other?