Present: Chris Allgower, Andy Bacher, Hermann Nann, Tom Rinckel, Paul Pancella, and Ed Stephenson
Meeting came to order at 3:10 pm.
SEPTUM MAGNET POST-MORTEM
We spent some time discussing the failure of the upper coil of the septum magnet last week. As previously reported, inner and outer windings were powered by two different power supplies, and it is clear that a short developed between these two groups of windings. The electrical potential between these two coil groups was not measured prior to the event, but is believed to have been around 150 V. There is only speculation as to the cause of the short. Some wonder if a shutdown of one power supply could momentarily have increased the potential difference to the breakdown point, while Rinckel is of the opinion that the short circuit caused the power supply trip (by overcurrent), not the other way around. An imperfection in the insulation wrapping or a trapped sliver of metal could have been the initial cause, but there is no evidence. There is no other apparent reason for the failure to occur at the particular location along the coil, other than being at the (extended) boundary between the separately supplied winding groups.
The lower coil is still drying out, under low power, showing a slow increase in the resistance between the coil groups. There does not appear to be any reasonable way to waterproof these coil assemblies.
Our plan is to wind another upper coil as soon as the winding fixture returns from Argonne, which should be early next week. Then instead of splitting each coil between power supplies, one supply would power the whole upper coil, and the other would supply the lower. This removes any possibility of a repeat of this failure mode, as there is ample separation between upper and lower coils. The tradeoff is that we lose the automatic balance between fields generated by upper and lower coils. It is not known exactly what effect an up/down imbalance would have on the beam transport in the channel, nor does PVP know how to simulate it in Transport. We will probably have to look for any effects on the field symmetry about the midplane in the next phase of mapping. It may be advisable to move one of the two Hall probes (now both on the top of the magnet) to the lower part of the magnet as an aid in balancing the two supplies.
SCHEDULING
Recent events put an inescapable delay in our schedule on the order of two or three months. In addition, it now appears that the liquid hydrogen target for the Tagger will not be ready for testing in the Cooler before March. The only possible schedule element that can be moved up into this time is a first look at deuteron beam polarimetry with the Pintex setup in the A-region.
Stephenson showed a revised schedule outline for the next several months. A 4-day deuteron beam run would occur in mid- February, followed by a long access period. During this access, the linacs would be prepared for proton beam and the LH2 target would be tested. Hopefully, septum magnet mapping would also proceed, but the first test of the channel would be moved to the second week of June. There is no longer any room for a second channel test run with protons after any bugs are worked out. We should try to have a target box ready to install by late summer/early fall. We still hope that tagger production running is completed in July/early August.
Can we possibly commission the Pintex setup as a deuteron beam polarimeter in three weeks? The Pintex group is agreeable to this proposal but unable to help much with manpower. We discussed in broad outline what will be required, and agreed it is worth a try. Ed, Chris, and Paul will meet Monday morning to assign tasks in more detail. We will also alert our outside collaborators of this opportunity to participate in this important run.
ELECTRONICS SETUP
We are still waiting for AC power to our electronics racks, which is expected soon. Nevertheless, Chris has continued to make progress, and has a substantial number of jobs on his list which do not depend on this power being available. We have been successful in getting help from the operations group (John Ostler) in making cables, and more will be needed. A cosmic ray setup is cabled in and ready to send events as soon as the power and computer hookups are ready.
FUTURE OF COOLER-CSB
Aside from the inevitable and surmountable technical problems, a significant shortage of manpower puts our ability to complete this experiment into some doubt. The remainder of the meeting was taken up by discussion of this issue. While CE78 is still supported by lab management, it is essential that we have additional personnel actively involved by the middle of this coming summer. That way they can be brought up to speed before Pancella and possibly Allgower leave IUCF. Suggestions from other collaborators off site would be welcome.
The meeting adjourned at about 5:30 pm.