Participants: Fredrik Wenander, Thomas Sieber,
1. Control System and Power Supplies
- Mats has an agreement with Ivan Deloose now, that Ivan will spend ~ 2 hours per week to do maintenance work of the REX control system.
- Nicolas David gave a talk about the REX power supplies. Besides the wide range of different supply types, which makes the maintenance difficult, he pointed out that the spare part situation is quite critical. Only 35% of the power supplies have a spare one. He gave a price estimation for the additional spare parts needed. Fredrik and Thomas will sit together with him and discuss the necessary spendings and also the priorities. Nicolas will produce a report and distribute it to the REX team and in his group.
2. TRAP
- The VME Crate of the Trap could be repaired by Frank Herfurth using an old ISOLTRAP card. It is running since three days now without problems.
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Frank Herfurth and Dietrich
Beck will work on a new control system for the trap, which is based on the
SHIPTRAP system. This work will not be finished before the REX runs. While REX
is running with the current temporary solution,
3. EBIS
- The new cathode is working stable at currents around 240 mA. There are still high losses occurring for unknown reasons. 200 mA can be guaranteed for the runs, but for heavier masses currents up to 300 mA are required. Fredrik tries to solve this.
- In this context Fredrik was asking for a dedicated meeting for cathode and electron beam improvement. The only success in that field is until now a new cathode power supply, which has been bought recently. A summer student will do simulation calculations for the electron beam dynamics, he might be employed as a technical student later on.
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The collaboration with Leif Lilleby
from
- There is still a strong fraction of Nitrogen in the EBIS spectra. Because of the very good vacuum in the EBIS a leak is more and more excluded. It is still unclear where the contamination comes from.
- The Helium filling intervals are the same like before, during the absence of Fredrik, he will pump the system, which avoids filling.
4. LINAC
.
- The REX LINAC has been prepared for the upcoming experiments. On the rf-side, the “old” part of the machine runs now very reliable, having only one Switch off in a whole week of operation.
- The new 200 MHz section is still running unstable, the power level is – due to problems also in the low-level system – limited to 90 kW. Therefore the tuning was done for A/q=3.5 at 2.9 MeV/u. The rf-group will try to solve this problem during Thomas´ absence.
- Another restriction for the maximum energy (or A/q) at REX after the upgrade is the bending magnet in front of the target. At A/q=4 and 3 MeV/u, 1050 mT are required, while the specifications give a limit of 1014 mT. Therefore a compromise in energy (resp. A/q) has to be found for the experiments at high energies.
- Regarding the beam optics settings, the beam spot at the target has improved at 2.9 MeV (because of the smaller emittance). The transmission through the LINAC is similar to what we had at 2.2 MeV, means 80% decreasing to ~70% after optimizing the spot size. The best spot size is 3mm circular.
- The members of the rf-group insist on a change of the ventilation system in the amplifier room because the working conditions there are terrible. Some of them have become ill after staying one or two days in the room. This has been noticed before also by the physicists who worked there, but a solution could never be found without major changes of the whole system. Thomas will search for a new concept and call for an offer.
- The FECs for EBIS and BeamOptics show the same problems now like the BeamDiagnostic FEC. They have to be rebooted each 3-5 hours, which makes operation very difficult. Ivan Deloose has started to look into it, but has not yet figured out where the problem lies.
5. Misc.
- Fredrik will be at a conference and in Holidays from 25.06. to 11.07. Thomas will be in Holidays from 25.06. to 16.07.
Minutes by Thomas