Be run autumn 2005
Target issues:
* Target number #308, Ta rolls, W surface ioniser
isotopes
run: 12Be4+ and 11Be3+
breeding
time: 18 ms for 4+ and 10 ms for 3+
currents:
* For 12/12 pulses, 2E13 p/p with 12Be4+:
No currents seen anywhere for 12Be
* For 12/12 pulses, 2E13 p/p with 11Be3+:
Nothing seen on the injection plate (large offset);
BTS.FC20=1.5-2 pA; RFQ.FC20=0.6-0.8
pA; BL2.FC10=0.6 pA
(An average 11Be of about 10E5/sec at the experiment, after
the collimator)
efficiency:
*
(Varied
since the magnet calibration drifted.)
Ne
buffer gas (6.6-6.8 V)
* Trap: 20% efficiency for stable 7Li
(short beam gate, 20 ms cooling time);
Trap: 23% efficiency for stable 9Be (10 ms
beam gate, 20 ms cooling)
* EBIS: 13% for 7Li3+
(15 ms breeding time)
EBIS: 13% for 7Li2+ (5 ms breeding time)
EBIS: 20% for 9Be3+ (10 ms breeding time)
EBIS: 12% for 11Be3+ (10 ms and 6.7 V)
Ar buffer gas (5.3 V)
* Trap: 5% efficiency for 6Li (cooling time 20 ms)
* EBIS: 8% efficiency for 6Li3+ (breeding time 16 ms)
* Linac transmission: ~85% for 11Be3+ (to
BL2.DC10)
Linac
energy:
* 2.24-2.25 MeV/u
(9-gap cavity not used)
comments:
* We used isotopically enriched
20Ne (~500 euro for 1.5 l atm)
* For 11Be we used 20Ne and then Ar
as buffer gas.
* The experiment saw an increase in the beam rate 20 min
before we ran out of 20Ne gas in the trap.
* We used stripper
foils 50 ug/cm2 to convert 11Be3+ to 11Be4+ and decrease the remaining
parasitic 22Ne.
technical problems:
* Magnet calibration
drifted for light masses.
* Miniball
venting at the end of the run triggered the RF to switch off in the Linac.
* Discharges inside the trap with
running with Ar as buffer gas higher than 5.3 V.
lessons
learned:
* The trap can be
operated with 100 Hz with maintained efficiency compared with 50 Hz. Tried with
stable Li so far.
* Lasers
have to be retuned when the isotope is changed.
* The EBIS efficiency
for Be can be improved by adding He gas to enhance the
ion-ion cooling.