CERN Accelerating science

Prototyping in the SPS using pickups equipped with LHC electronics

Meeting held on Friday 8-05-2001 - reported by Mike Lamont

Present : M. Jonker, A. Butterworth, M. Lamont, O. Berrig, Lars Jensen, Jean-Jacques Gras, Rhodri Jones, Hermann Schmickler, Joerg Wenninger

Agenda :

Prototyping in the SPS using pickups equipped with LHC electronics

Minutes :

Mike presented the now well-established motivation for prototyping local orbit feedback for the LHC in the SPS.

Rhodri presented possible BPM alternatives and electronics issues:

BPMs - 3 options identified:

•  use of existing BPCNs HOR plane available (VER plane used for MOPOS) 123,125; 223,227; 333,337; 611,613.
•  Installation of modified LEP button pickups as in 421. aperture 83mm. Required number will have to be built.
•  Installation of modified BPCK as for TT40. Aperture for beam 117mm. Foreseen to be modified during 2001/2002 shutdown up to 5 available (to be verified)

Electronics

The LHC type acquisition system cable length has to be as short as possible.

• If the BPM position is favourable:  all electronics installed on surface using only electrical links
• If the BPM position is unfavourable:  front-end card in tunnel and a fibre-optic link.
• What data will be available? Average of 20ms of orbit data at 10Hz turn-by-turn & bunch-by-bunch data on demand
• Possible problems component delays, in particular laser transmitters & ferrites

Would still need WorldFIP (or microFIP or digital I/O on VME bus)  for resets etc.- only a few bits flowing.

Hermann explained that the pickups could be used to make beta measurements (1000 turns) to supplement emittance measurements, particularly of they were placed at 40 degrees phase advance with respect to the existing MOPOS equipped pickups. This in point 5 of the SPS.

After discussion it was clear that the favoured solution was 6 modified LEP pickups. Modified aperture, and flange for LEP buttons required.

(Both planes? i.e. two buttons versus four buttons - cost.)

PROPOSAL

Would need to put a small project proposal together by August to get approval ASAP. Long lead time in design of pickups, vacuum modifications, ST pulling cables etc.

Main areas requiring attention

•  BPM design (resp. Rhodri Jones) - approx. 1 man week for design
•  Positioning of pickups in around point 5 (resp. Joerg, Rhodri and Claude Fischer)
•  Infrastructure issues (resp. Rhodri Jones): ethernet availability in LSS5, WorldFIP drivers (resp. JJ Savioz), Timing, positioning of front ends.

The pickups will only work with LHC beams, with potential use on the second (MD) protons cycle, or during the dedicated LHC 25 ns test beams (availability in 2002 to be checked).

Other issues

• Something about whether or not ethernet cards have one or two plugs
• Whether muGefs allowed direct control - to be checked by Olav.
• Olav also suggested a closer look at the theory of local orbit control

Next meeting in a month