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
Stripper foil was used to move the stable contamination 22Ne6+ away from 11Li3+
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