Minutes
from REX meeting 2004-11-24
Present:
General issues
* The minutes
from the last meeting were approved.
* Heiko Scheit’s
‘REX Scientific Report’ was discussed and the point stating an effective beam
to the experiment delivery time of 50% was criticised.
* An email list
for the closest REX-persons has been created to distribute drafts of minutes
etc; support-rex@cern.ch.
* A summary from
a REX operation point-of-view of the Li and Sn runs
is attached to the end of these minutes.
Control system
* D. Beck will
come down from GSI the 6/12 to assist Romain
transferring the REXTRAP control system to the new Labview
based system.
* Nikolai had two
points concerning the REX control system:
a. It is
difficult to port the hall probe controls for the dipole magnet controls from
PC to UNIX. This would require a significant effort. An alternative solution
has to be found as the field regulating feature is needed.
b. Nikolai
underlined the need for application software for the coming new REX control
system and that the programming should start asap. Mats explained that programming support would
be given from the Operator’s group and that he will get in contact with them. At
some point Mats, Nikolai,
* A technical
meeting between AB/PO and AB/CO, with representatives from REX, is scheduled
for Friday 26/11. Different solutions and strategies for upgrading the REX
control system and the power related hardware is to be discussed.
* Nikolai will come back with a time
estimate for when the REX vacuum system can be remotely controlled from the
consoles. The choice of control strategy has to be agreed upon between the
vacuum and the control groups. Most likely there will again not be any remote
control for the vacuum system from the ISOLDE control room during the next
years running period.
*
Thomas will contact
* Romain has taken two old non-used FEC computers and
converted them from NT to XP. One to be used at the REXTRAP, the other will act
as spare.
REXTRAP and REXEBIS
* The
REXTRAP is stopped.
*
The REXEBIS is under disassembling for next week’s intervention in the
cryostat.
* The
vacuum pumping of the low energy parts (except for the EBIS) will be
recommenced after the power cut by the end of the week.
*
*
The LN2 filling of the REXTRAP over Christmas will be carried out by
LINAC
* The Linac
is switched off and vented.
* Berdermann
from the Bertronix company
has started rebuilding a new anode capacitor for the 200 MHz amplifier. Should be ready before 1st of March.
* Thomas plans to install a
setup for emittance measurements with the linac test
source at 20 keV in building 275.
Shutdown planning
* Mats asked for
a single list of shutdown work covering all parts of REX. It should also
contain priority ratings and deadlines. This is found on the homepage of the
REX minutes. Thomas has already agreed with his section upon a work schedule
and priorities.
* After the
meeting Thomas, Pierre, Fredrik, N David, D Porret
and Nikolai discussed the shutdown work.
a. Nikolai agreed
to order a spare PCI card for the REXEBIS VME.
b. The worklists related to vacuum and power were shown to N.
David and D. Porret. It was agreed on that most of
the work will be performed in January.
c. All equipment
should be back by mid March. The EBIS will not be ready by then due to its
complete disassembling; either it will be ready in the beginning of April or in
the end depending on Fredrik’s other obligations within his section.
d. A major
shutdown work is to implement a vacuum interlock for the HT supplies in the BTS
and mass separator. N. David and D. Porret will deal
with this.
e. D. Porret will
focus on improving the
f. The question
of installation of an extra roughing vacuum balloon was once again raised as
REX might be running radioactive Xe with high
currents next year. Fredrik will check with TIS and Mats if we can operate 2005
without a balloon without running into complications.
Minutes
taken by Fredrik Wenander
Li run
isotopes run: 9,11Li and stable 7Li
run 9Li+ with Ne buffer gas
run 11Li with Ne and Ar buffer gas
yields: 1.3E6/uC for 9Li+ from the ISOLDE target
Jacques was guessing 1000 11Li/uC
target=700 to 750 A A, line=300-350 A
From the logbook
Target test finished. Count rate on 9Li was 12% down compared to measurements made at the beginning of the run. P-beam scan OK and left at (0A,-17A) Target heating 670A > 6800cts, 700A >7700cts, 730A > 8800cts, 760A > 9500, 790A > 10100cts. Target left at 760A...line heating 340A > 10500cts, 350A > 11000cts, 360A > 11700cts. Line left at 350A and target reduced to 730A when taking 4 pulses at 3E+13ppp. Permission is given to increase target temperature if required...to 760A is OK....790A at your own risk and peril. Release curve made on 9Li.
breeding time: 5 and 9 ms for 2+ and 3+ respectively.
efficiencies:
Trap 30-40% for 9Li and Ne gas
10-20% for 11Li and Ar gas
EBIS 7Li2+ 9.3% with 5 ms breeding time
11.6% for 7Li3+ with 16 ms breeding time
5% for 7Li3+ with 8 ms breeding
time
(during these tests the Na+ to Na7+
breeding efficiency was down to a modest 8%)
13.5% for 7Li2+ in the end of the run
With Ar the Trap+EBIS efficiency for 7Li+ was 1.8%
Linac 80% but what about the injection efficiency into the Linac for 9,11Li and focussing on the experimental target?
current after trap and ebis: for 9Li+ 1 pA could be seen after the trap at proton impact
technical problems:
* ISOLDE target vented – ion source and trap section affected, restart the trap
* Can not run synchonised with the protons as the Linac will switch off
* Can not run with 100 Hz due to the linac
* Turbo pump in the mass separator switches of regularly
* Even if 18O4+ goes into the RFQ it’s not sure that 9Li2+ follows. Needed to steer with the deflector before the RFQ.
* Also noticed that different mass separator settings, both optimised for some stable beam, give highly different transmission for 9Li2+. The B-field was scanned and correct. How come?
comments: the breeding efficiency went down from 11.6% to 7.4 when the cooling time was decreased from 20 to 10 ms
lesson: when changing buffer gas the residual peaks disappears completely (<100 fA) after a few minutes
with Ar gas pressure higher than 5.7 V one has discharges in the extraction region
isotopes run: 110Sn27+ radioactive; 112, 118Sn stable
(not accelerated)
also delivered stable 27Al and
39K to the experiment after failing 9-gap resonator
yields:
110Sn
2.5E8/uC, 110In >1E7/uC 110mIn 1-2E7/uC
15-30
minutes before it comes into saturation. -REX
breeding time: 98 ms for 110Sn27+
efficiencies:
Trap 44% (110Sn)
(45% for 112Sn)
EBIS 8-10% for
110 pA of 110Sn+ into trap
(8-16% for 112Sn)
(9.5 to 11.5% for stable 138Ba30+)
Linac 70-80% ??
current after trap and ebis:
110
pA at injection plate trap, 48 pA out of trap and 115 (100-140) pA
after EBIS; depending on number of protons
technical problems:
200
MHz amplifier broke -> had to run at a lower energy
fluctuating ebeam current; between 150 and 220 mA,
correlated with the cathode heating power
comments:
Had to decrease the number of protons to 700E10 per
pulse.
Used
139La+ and 138Ba+ for stable beam setup.
At
least a factor 10 less In than Sn
lesson: target characterised by the target section before