108,106Sn run autumn 2006
Target issues:
* Used LaC
#286, W surface ioniser mk8
* To improve
the Sn/In ratio run with consecutive pulses with the beam gate closed,
thereafter empty pulses with beam gate open.
Yield values from logbook
The 108Sn/108In ratio would increase to
3:1 if gating of 10 s and more would be used. Target temperature could be
further increased with great caution.
On mass 106, little Sn is coming on top of large In beam. Maybe a few % seen
after 5-10s. There target/line temperature is the only variable for this run.
Other strategies could be developped (Quartz, low work function cavity as Ta,
and even more exploratory materials) /TS
108Sn
MINIBALL taking pulses 6,7,8 and 10 at
1.4E13. Beam gate open 1.5 s after supercycle pulse with 6 s duration. 10
pulses in supercycle. Estimated 60% 108Sn, 40% 108In in the beam./JC
106Sn
Short test with pulses 6,7,8 at 3E13 pp
gives 44% 106Sn in the beam from miniball laser on/off measurement. Total
current approx 1-2 pA after the EBIS. Gate opens 2.5 s after last pulse.
Duration 5 s. /JC
isotopes run:
108Sn26+ and 106Sn26+ with lasers
breeding time
and extraction: 67 ms, peak charge at
26+
slow
extraction, 500 us ramping time, FWHM Text=200 us
efficiency and
currents:
*
* With 30 ms
beam gate, 70 ms period time and 12 pA 115In+ on the injection plate we have a
total (trap+EBIS) efficiency of 9% for In26+. For slow extraction total
efficiency 8.5%.
* With 6/12
pulses, 3E13 p/p we have for 108Sn:
Trap inj plate: 36-80 pA, BTS.FC20=19-38 pA, RFQ.FC20(26+)=70-145 pA
=> Total efficiency 7-7.5%
No beam gate, slow extraction, 67 ms breeding time, 70 ms period time.
* With 2
pulses/sc, 3.2E13 p/p we have for 106Sn:
4 (+-1) pA in peak on trap inj plate, 2.5 pA in peak on BTS.FC20
7.8
pA (26+) in peak on RFQ.FC20
=> Trap eff <62%, EBIS eff >12%
No beam gate,
slow extraction, 67 ms breeding time, 70 ms period time.
Linac currents:
With 3/10 pulses/sc, 3.2E13 p/p we have for 108Sn26+
:
RFQ.FC20= 25
– 41 pA
IHS.FC40= 21 – 37 pA
With 2 pulses/sc, 3.2E13 p/p for 106Sn26+
:
RFQ.FC20= 0.7
– 9 pA
IHS.FC40= 1.4 – 8.6 pA
Linac transmission and energy:
60%
for 108Sn at 2.82MeV/u (not optimised for best transmission)
77%
for 106Sn at 2.83 MeV/u
Comments
* No major problems with REX
* No protons during day time for during the period of
setup
* Reference
settings for
REX_2006-09-18.csv
*
Miniball is now using two colimators: more difficult to get the beam through
but no beam on the CD quadrants
with empty frame.
Technical problems
* A couple of reboots of BD FEC
* The air conditioning for the RF room switched off
and caused interlock stops for a couple of amplifiers (9-gap and 7-gap 2)
* The
Simatics
* A stop of
a Penning gauge in the REX separator section caused the vacuum interlock for
the electrostatic elements in the separator line to switch off. At the same
time acqusition for all elements in the linac showed zero. Had to
reboot the Linux consolde machine.
Lessons learned
* Always set up linac without 9gap at first.