30, 31Mg run Sep
2007
Target
issues:
* #362 UCx, MK8, laser ionisation
* K and Mg mass markers
*
* Yield values:
Yield
measurement gave 31Mg
of 2.3E5 part/uC protons
No
yield measurement for 30Mg
Miniball
measured between 4200 and 13000 31Mg/s
Overall
REX efficiency therefore between 1.8 and 5.6%
(REX-estimated
efficiency 0.9*0.12*0.5~5%)
Experimental issues:
* Miniball
* IS409 and IS410
* 30Mg7+ and 31Mg9+
breeding time, efficiency and currents:
Normal EBIS extraction
used throughout all run
Breeding times 28.5 ms
for Mg9+ and 15 ms for Mg7+
39K10+
(stable)
Tperiod=30 ms, Tbeamgate=5 ms, Tbreed=14 ms
(optimized)
I(inj
plate)=21 pA, BTS.FC20=10.5pA, RFQ.FC20=26pA =>
TRAP+EBIS
eff= 12.4%
24Mg9+ (stable)
Tperiod=30 ms, Tbeamgate=15 ms, Tbreed=28.5 ms
(optimized)
I(inj
plate)=17 pA, RFQ.FC20=20 pA
=> TRAP+EBIS eff= 12-14%
currents
* no currents measured on any FCs
for 31Mg
* 1-3 pA on trap inj plate for 30Mg
linac energy and transmission:
For 31Mg9+ 3.0 MeV/u 50-60% transmission for A/q=3.5 pilot beam
For 30Mg7+ 2.275 MeV/u 61% transmission for A/q=4 pilot beam
1.91
MeV/u 60%
transmission for A/q=4 pilot beam
1.56
MeV/u 60%
transmission for A/q=4 pilot beam
Technical problems:
* The IHS amplifier
stopped occasionally when operating with the high A/q-value due to cavity
sparking.
* Difficult
to find a stable and efficient transmission for the linac.
Suspected charging up of beam elements in the QP before the
RFQ. Quadrupole XRFQ.QS50 was grounded during the run, hence the low linac transmission.
Comments and lessons
learned
* A smooth
run where different beam energies could be delivered.