Minutes from REX meeting 2006-07-26
Present:
REX low energy part
* The trap,
EBIS and mass separator were working well with record global efficiencies of up
to 10%.
* A
booster turbo pump has been installed on the primary vacuum line of the trap to
compensate for a less good primary vacuum following the move of primary pumps
in the shielded area. This pump is for the moment operated manually (no
interlocks). Extra care should be taken when working on REX vacuum.
* One of
the turbo in the separator his faulty and causes outgassing. It is hoped to be changed
before next run.
* The
noise problem on the trap TOF has been solved.
REX linac
* The problem on IHS has now been solved. Instabilities
observed during last run were connected with the position of tuner 1. It is believed
the tuner was accidentally moved (close to a forbidden position?) during
reinstallation of the stepping motor in June.
Forbidden positions of the tuners should be
re-established during next shutdown.
* The
tuners on the 7 gaps cavities have become stiff and move with difficulty. They
need to be repaired/changed. Maybe need a new design.
* All
tuners should be checked and maintained during next shutdown.
* A lot
of oil has been found in the exhaust line of REX primary pumps. This oil
started contaminating the dry pumps of the linac. Oil traps should be installed
on all roughing pump exhausts.
* A new
RF timing system is ready to be installed in the RF room. This should make RF
independent of EBIS timing.
Beam Diagnostics
* The
gateway is working well and the windows BD applications are also running more
stably.
* BEN.FC40
on the linac has now been fixed enabling to read beam current before the
bender. The FC shield was not grounded. This should also be checked on all
other REX FC (shutdown work).
* FC and profiler
actuators are now all working except for BEN.FC100 which still has to be
operated by hand. Spare parts have been ordered.
Mg run
* Following
the poor result of last week’s run (two hours of high quality beam delivered) a
number of problems have been identified:
- IH problem already mentioned
- shifts in
planning (shutdown work postponed) and several technical problems (vacuum leak
in cavity) lead to a very late start for REX. The linac could only be started 5
days before the run! A start-up period of several weeks before the first run is
necessary so problems can be identified and fixed before the runs.
- operation of WITCH in parallel with
setting up of REX meant the settings were useless when WITCH magnet was
switched off. Need better coordination/planning.
- an important time was wasted trying to
find a discrepancy of several orders of magnitude between Isolde yield measurements and Miniball count
rates for Mg29/Mg31 which was in fact largely due to mistakes/misunderstanding.
In the end a ratio of 1/12 was found in the trap TOF between 31 and 29 which is
coherent with the yield measurement. However the count rate at Miniball was
still lower than expected by approximately a factor of 10(?). This has not been
clarified yet.
In the
future a tape station should be installed after the separator to enable proper
diagnostics of radioactive beams transmissions.
Control and applications
* New
control applications are working generally well, although a few problems/bugs
remain to be fixed: peak identification, crash connected with open/save
*
Protections should be implemented in the FEC to avoid SEP power supplies going
to their max values for example in case of application crash or errors.
*
Migration of EBIS and control of new power supplies for Minimove are planned
for next year.
* A
separate VME crate for the control of the extra quadrupole lenses for the
Minimove would be required for the new power supplies. 2/3 weeks programming
work. Estimated cost: 20kCHF.
*
Programming work should start quickly for EBIS migration to happen next
shutdown. Isolde will hire a new operator/programmer for REX, starting in
Septembre, who should take up this task.
General comments
* All valves
are still operated manually on PLCs. When will they be implemented in the
vacuum control system?
* Scaling
for the dipoles should be done with magnetic field and not current. New hall probes and regulation cards would be
required. Nicolas David will look into the problem.
Minutes taken by Didier Voulot