Participants:
Minutes by Thomas Sieber
- Fredrik presented a plan for the improvement and intensity upgrade of the electron beam in the REXEBIS. This plan includes two major points: 1. Improved simulation calculations for the electron beam dynamics. 2. Experimental studies with new cathodes and extraction geometries, which should be done at the twin EBIS at MSL.
The main question is which work
force might be available for this project. It is not yet clear to what extend
the twin EBIS at
The following list with details was distributed at the meeting.
REXEBIS electron beam upgrade
Goals:
* Increased cathode lifetime – cathode change once a year
* Higher electron beam current – reach nominal 0.5 A, at a later
stage 1 A
* Higher electron current density – reach design value of 250
A/cm2, at a later stage 400 A/cm2
* Maintained injection acceptance also for higher electron current
density
Work
force:
Summer student at AB, summer
2004??
Fellow Karin Fritioff at AB, from ??
Manne Siegbahn
Laboratory
* Wishes: doctoral student
(based at MSL?), or at least a diploma student or technical student.
* Estimated work load – one
year
Simulation
1. Implement the present ebeam system in
OPERA 3D (or PBGUN/TRAK/IGUN). The complete structure in one
run, no splitting and splineing. Reliable simulation.
2. Scale voltages – check when space charge effects hampers the
beam propagation.
3. Estimate beam ripple and ebeam behaviour in collector region
4. Simulate higher collector potential
5. Simulate ebeam with and without post
anode
6. Design a high compression gun
j(cathode)~10
A/cm2, r(cathode)~1.25 mm, 25 times compression
Hardware
development
1. IrCe cathode
* investigate
cathode heating, DC or AC
* lifetime
* max current density at cathode
* gun design / mounting
2. Manufacture a post anode gun
3. Construct and manufacture a high compression gun
j(cathode)~10
A/cm2, r(cathode)~1.25 mm, 25 times compression
Tests
1. Higher collector and suppressor voltage (at CERN). Could lead to
lower electron beam losses and enable higher electron current.
2. IrCe cathode tests (at MSL)
3. Post anode tests (at MSL)
4. High compression gun (at MSL)
- The EBIS test bench, which was planned to be used for tests of different EBIS-components (cathodes etc.), will be set up later this year. The test bench will not be installed in building 275 because it would be too far away there from the workshops and the offices of responsible people.
- It is impossible at the moment to order a necessary turbo pump because of difficulties in the contractual situation between CERN and the manufacturer. This would cause a delay of more than 3 weeks. The solution is now to NOT buy a new pump and to use a spare pump from the LINAC until the old pump has been repaired. The price for repair is roughly the same like for the new pump (but the old pump has better performance). If meanwhile a turbo pump is needed for the emittance scanner at the LINAC (quite unlikely) the ECR group has to give back the 150l turbo they borrowed from REX.
- The new collector power supply has been ordered. The price is finally 8.400 €.
- Fredrik reported that a problem with the database for the REX computers has been solved. All FECs are running now.
- The VME crate of the trap gives an error message, saying some addresses are not accessible. Although the system seems to be fully operational, this should be checked before the running period.
- The alignment of the transfer beamline is now - since there was no practicable optical or mechanical solution found - checked by using the beam from the first deflector as a reference. Thomas had some objections concerning the reliability of this measurement. He will try to find another solution, which then can be verified by CERN alignment personnel.
-
For tests of beam injection from Trap to EBIS,
-
It was agreed between
- The end drift tubes of the 9-gap resonator were slightly too short. New drift tubes will be produced in the main workshop next week.
- The new technician in the power supply group will start on 01.03. The group leader agreed with Mats, that he will be at REX for 80% of his working time.
-
Thomas wanted to know who will collect the contributions
to the REX yellow report in future, since Joakim is
going to leave. Fredrik assumed he will continue with this work when he is at
- The REX-ISOLDE web page, which is to be found on the ISOLDE homepage, was partially updated by Elisabeth. Fredrik will give the missing information to the ISOLDE secretary who will take care for this task.
- MINIBALL will not arrive at ISOLDE before August.
- The delivery of the beam from ISOLDE to REXTRAP shall be done by the ISOLDE operators, not by the REX operating team.
- The duration for optimization of beam transport from ISOLDE target to REXTRAP was about 4 hours during the last experiments.
- Duration of REXTRAP setup was 3-4 hours.
- Optimization of injection into the EBIS takes 3-4 hours
- Optimization of transmission through the mass separator: 1-2 hours
- Time for Setup of the LINAC: If A/q prepared 2 hours. If not 4-8 hours (depending strongly on the beam intensity).
- Due to the small number of people working on the machine, switching of the ion species will only be done in the morning. For the same reason there will be no beam tuning during the night and especially during the weekends. During the night and the weekends the operating team will be on call. The physicists must be teached to solve “standard” problems by their own.
- Luis will try to arrange a schedule while keeping the points above in mind.