FONT meeting notes of May 18 2007
Present:
Tony, Javier, Phil (Oxford)
Christine, Christina, Glenn, Ben, Hamid (KEK)
Alexander (DL)
Report on ATF shifts (Glenn, Christine, Christina)
--------------------------------------------------
There were 3 shifts but most of the useful data were taken in the last 5 hours
of the last shift!
shift 1:
3 bunches, large bunch-bunch position offsets, large jitter.
FB done with varying gain, probably of limited usefulness.
shift 2:
lost 3 hours due to thyratron fault.
Alexander was able to calibrate his BPMs.
FB set up, but problem with FB input difference signal not changing with beam position.
shift 3:
difference signal problem solved by 6db attenuation! suspect power overload in tunnel,
causing saturation/non-linearity of combiner/mixer?
good beam quality.
lots of high-quality data taken for 7 beam positions (2 deliberately saturated),
3 gain settings per beam position.
large 'banana' on train: order 200um sagitta?
Jitter data taken with FB on/off - FB seems to make a noticeable improvement!
1/Q normalisation tried and looks to have been successful. Noticeable improvement
on FB performance for beam near 0.
Clearly the data will need to be analysed carefully.
** It is clear that we need to bench-test the BPM processor to understand the
'saturation' effect; Christine thinks it's consistent with the data sheet for the
combiner.
BPM resolution studies (Christina)
----------------------------------
Christina has derived resolution numbers from the shift 1 data of week 1.
Sometimes 3-4 um resolution is obtained, at other times the resolution is worse.
There is no obvious pattern or correlation of performance with particular
processor/BPM pairings.
Some data were taken in week 2 with one processor in, and another out of, the tunnel,
for the same BPM: this may give some useful information.
Christina concludes there is a lot to do to understand the apparently varying
performance of the processors.
New BPM studies (Alexander)
---------------------------
Alexander is generally happy with his data.
Calibration and resolution runs were taken.
Some problems generating ADC input clock signals.
Problems with an interference signal in the driver - related to the power supply?
The main conclusion is that the synchronous detector concept has been verified.
Alexander will discuss the 'constant-energy extraction' from the ATF ring with
Kuroda, at the ATF2 meeting on May 28.
Repatriation of hardware
------------------------
Alexander brought his BPM processors back to the UK.
The FONT4 boards will be radiation-tested and, if safe, brought back to Oxford.
Cables, connectors etc. will be left in the new FONT cupboard.
Next meetings:
--------------
Friday May 25: no meeting
Friday June 1: no meeting due to LCWS
Friday June 8: 08.00 SLAC / 16.00 UK
best wishes,
Phil
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