188,186,184,182Hg
run 2008
Target
issues
* Target
number #388 (Mk3 molten lead with STAGISO low intensity beam)
* Beam on
target (no converter)
* Mass
markers: none
*
* Uht(
Yield
estimations
Estimated yield on
184Hg=2.7e6/uC (Slits In). Measured before the run. Underestimated.
Experimental
issues
* Beam to Miniball
* IS452
* Delivered beams: 184Hg44+,
186Hg44+, 188Hg45+, 182Hg44+
REX
Tuning
* Slow extraction from
EBIS was used with 186Hg and 188Hg
* REXTRAP timing
free-running relative to protons pulses
Low energy
Stable 205Tl from
ISOLDE
Tperiod=200 ms, Tbeamgate=50 ms, Tbreed=160 ms (optimised for 42+)
Trap inj plate 8 pA (with beam gate)
RFQ.FC20=15 pA (42+)
Trap+EBIS eff = 4.5%
Stable 132Xe32+
from ISOLDE
Tperiod=200 ms, Tbeamgate=50 ms, Tbreed=160 ms (not optimised)
GPSFC490
1890pA inj plate 1680pA 88%
Trap inj plate 30 pA (with 2% beam
gate) RFQ.FC20=38 pA XL65.FC50 =23pA
Trap+EBIS eff = 3.9%
Radioactive 184Hg44+ (16 of 40
proton pulses, 5E12 ppp)
Tperiod=204 ms, Tbreed=200
ms (more or less optimised for 44+)
Trap cyclotron freq optimised 245288 Hz
0.1-0.2 pA on trap inj plate, ~2 pA on RFQ.FC20, ~1.3
pA on XL65.FC50 (1.8E5 part/s)
6.8E4 part/s at Miniball
Radioactive 186Hg44+ (10 of 40
proton pulses, 5E12 ppp)
Tperiod=204 ms, Tbreed=200
ms
Trap cyclotron freq optimised 244517 Hz
3.5 pA on trap inj plate, 11 pA on RFQ.FC20, 6.5 pA on
XL65.FC50 (9.2E5 part/s)
Trap+EBIS eff = 7%
2.0E5 part/s at Miniball
Radioactive 188Hg45+ (10 of 28
proton pulses, 4.5E12 ppp)
Tperiod=204 ms, Tbreed=200
ms (not optimum for 45+ but better rep rate)
8 pA on trap inj plate, 18 pA on RFQ.FC20, 10 pA on
XL65.FC50 (1.4E6 part/s)
Trap+EBIS eff = 5%
3.5E5 part/s at Miniball
Radioactive 182Hg44+ (16 of 40
proton pulses, 5E12 ppp)
Tperiod=204 ms, Tbreed=200
ms
No beam seen on any FC, 2.6E3 part/s at Miniball
Linac transmission and energy:
~50-60% RFQ.FC20 to
XL65.FC50 at 2.85 MeV/u
Total
transmission (radioactive beam)
Setting
summary
For
* REX_
REX low energy settings saved as:
* REX-30kV-2008-09-30_
* BTS-30kV-2008-09-30_
REX separator and
linac settings saved as:
* 081001_1001_186Hg44_Aq4.2272_2.85MeVu_60%_MB.csv
* 081001_1001_SEP_186Hg44_Aq4.2272_2.85MeVu_60%_MB.csv
similar settings (scaled) were used for other A/q
Technical
problems
* Water
interlock of
* Failure
of 9GP grid2 supply at the start of the run
* Low
transmission in the linac
* Target
broke down in the end of the run. Suspected no lead left in the target
container.
Comments /
Lessons learned
* Need to
improve the stability and transmission of the linac (need a lot of steering in
the bender section, had to change the 9GP and buncher phase, charging-up effect…)
-> Find the source of instabilities
-> Improve beam transport after the 9GP
* Linac RF
was running very stably. No interruption during the run.
* Used Xe beams from ISOLDE with A/q very close to the A/q of the
radioactive beams to tune the linac. Only very limited
scaling necessary.