B-Train System in October 2000 - Overview and Recommendations

1. B-Train, situation in October 2000PSB The old analogue system based on V/F converters is still in operation on the PSB, and J-D. Schnell is responsible. The new digital system, based on modern ADCs, runs in parallel with the old system. It has evolved over several years via F. Caspers, D. Dekkers, M. Lindroos, and T. Salvermoser. The person who is now the most knowledgeable about it is M. Benedikt. The new system is used at the PSB by P. Odier for transformers. However, other clients at the PSB (notably the RF group) do not yet make use of the new system, although the electronics modules are installed (P. Dreesen). The magnetic measurement hardware for the new system uses a long coil and NMR markers in the reference magnet, for which D.Cornuet is responsible. The NMR flat-bottom marker is used routinely but the one on the flat-top is only used by experts. There is also a short coil and another long coil in the PSB reference magnet, which each produce B-trains using the old system. One can wonder why all these should be needed.

2. B-Train, situation in October 2000AD and LEIR AD AD runs with the new system for the diagnostics, but for the moment the synthetic train is used for deceleration. This situation will continue in 2001. However, in the longer term, the intention of S. Maury is to switch over to the new system, for which the electronics modules are installed. New magnetic measurement hardware (long coil and NMR markers) was installed for AD in one of the ring magnets. D. Cornuet is responsible. The NMR markers are not in fact used in routine operation by the electronics for AD, because of the high quality of the digital integrator. If there is a problem with the electronics, P. Dreesen (or I. Garcia Alfonso) is called, and F. Caspers is available for advice. LEIR The old LEAR had its own B-train, but LEIR will be equipped with the new system in due time. The magnetic measurement hardware will be in installed one of the ring magnets.

3. B-Train, situation in October 2000PS J-C. Thomi is in charge of the present (old) PS system, which he says will stay in place until the end of 2002. The new system will be installed on the PS only when it has been fully tested off-line. The magnetic measurement hardware of the present system (a short coil and peaking strips as markers) is in the reference magnet 101 in the temperature-controlled room, and D.Cornuet is responsible. There are in fact 3 separate sets of coils which yield 3 separate B-trains, and operators can switch between them; they have different calibrations, and one can wonder why 3 are needed. One of them simultaneously uses a dB/dt signal in a feedback loop to control the PS main generator. The new system was originally going to have a new long coil and new peaking strips as markers. Now the idea is to use what exists, doing the testing on one of the existing 3 coils and strips. ESR markers are also a possibility (D.Cornuet). Preparations are under way on the electronics hardware of the new system on budget code 78360 in PO group (P. Dreesen and I. Garcia Alfonso). The new modules will be installed in the next shutdown, but further work is needed in RF group before the new system can be tried out on the PS. LHC beams need the new B-train for reasons of precision (<1 G) and reproducibility (dixit R.Cappi). There are also ferrimagnetic (FMR) markers in the PS reference magnet provided by F.Caspers, who will continue to be responsible for them (with G.Adrian for controls). These are not in routine use because the controls are not user-friendly. In principle FMR is less sensitive to field gradients than NMR.

4. B-Train, situation in October 2000Synthetic B-Train The synthetic B-train, based on a model of the machine, is provided by J.Lewis (for the PSB) and B.Holzer (for AD). There are synthetic trains for both the PSB and AD. The synthetic train is software-generated but requires an input from the magnetic measurement hardware. It has been cross-checked with the measured B-train for both the PSB and AD and found to be in good agreement. The synthetic train has been used on occasions at PSB as a substitute for the measured B-train when this was unavailable. In the case of AD, the synthetic train was used initially because there was no measured train, and it is still used at the moment for deceleration. There is also a synthetic train for the PS but this is delicate and unreliable. There would seem to be good reasons to have a synthetic train available for all machines, and for the software to detect any difference between the measured and synthetic, in order to raise a flag.

5. B-Train, situation in October 2000 Suggestions, not in order of priority 1. Develop a synthetic train for all machines, and run a permanent comparison so that any discrepancy is flagged. 2. If there are indeed redundant B-trains on both the PSB and the PS, as seems to be the case, they should be switched off. 3. Use one of the 3 sets of PS magnetic measurement coils for testing the new system on the PS as soon as possible. 4. Decide what is the best marker for use on the PS (peaking strip, NMR, FMR, ESR, quadrupole). 5. Prepare whatever hardware and software is needed to make the new system operational for RF on the PSB as soon as possible. Then turn off the old B-train system of the PSB. 6. As point 5 above, but for the PS. 7. Give the overall responsibility for all aspects of B-trains to one person, to act as the central repository of knowledge. He should report to the Divisional Management regularly. This person should also keep in contact with the SPS.