202,204Rn run 2008

Target issues
* Target number #385 UCx, plasma, cold line
* Beam on target (no converter)
* Mass markers: Ar/Xe mixture
* HRS separator
* RFQ cooler operated in cw mode
* Uht(HRS,CCV)=30.16 kV, Uht(HRS, HT_target)=30.1589 kV, Anode=150 V, Uht(RFQ cooler)=30.20 kV, RFQ extraction=0 V, Uht(trap)=30.00kV, Elec05=160 V

202Rn: 1.3e5 at/uC
204Rn: 6.0e6 at/uC
(NOT corrected for the alfa branching ratio and for 60% RFQ cooler transmission)

Experimental issues
*  Beam to Miniball
* IS465

REX Tuning
* Normal extraction from EBIS
* REXTRAP timing free-running relative to protons pulses

Low energy
128Xe HRS.FC490=2.1 nA, trap inj plate=1.52 nA => 72% transmission (no slits inserted)
76% transmission (HRS slits inserted)

Stable beam 181Ta
Tperiod=140ms, Tbeamgate=14ms, Tbreeding=129ms (optimized for 40+)
Trap inj. plate=60pA (without beamgate), RFQ.FC20=14.5pA
Trap+EBIS efficiency=6%

Radioactive 204Rn (3E13 ppp, 9 out of 40 pulses)
Tperiod=205 ms, beam gate open, Tbreed=200 ms (not optimized for 47+)
Trap inj plate=~2 pA (average), RFQ.FC20(47+)=~2.4 pA (average)
=> trap+EBIS eff~2.6%

Optimum for Tperiod=250 ms, Tbreed=255 ms => => trap+EBIS eff~3.7%
Decided to run with higher repetition rate to avoid dead-time in detectors.
Did not make use of slow extraction.

Linac transmission and energy: 
50% RFQ.FC20 to XL65.FC50 for 204Rn at 2.28 MeV/u
30% RFQ.FC20 to XL65.FC50 for 204Rn at 2.80 MeV/u
70% RFQ.FC20 to XL65.FC50 for 202Rn at 2.80 MeV/u
70% RFQ.FC20 to XL65.FC50 for 202Rn at 2.28 MeV/u
9 mm lead/tantallum collimator ~4 cm before the MB target frame (always present)

Total transmission (radioactive beam)
HRS.FC490_to_trap x Trap_EBIS x Linac 
0.72*0.026*(0.5 or 0.3 or 0.7 or 0.7, see above)=0.3% to 1.3%

Delivered beams
204Rn47+ and 202Rn47+; both without contaminations

204Rd47+: 9/40 proton pulses, 1.7e13 ppp => RFQ.FC20 ~3.2 pA, XBEN.FC100=1.5 pA, XL65.FC50=1.3 pA

202Rd47+: 13/40 proton pulses, 3e13 ppp => saw beam on HRS.FS670, RFQ.FC20 ~0.3pA,
end of the linac ~0.2pA. The beam could be seen on PPAC.

Estimated beam intensities at Miniball online = ~1E5 (204) and 3E4 (202) pps (orders of magnitude)

Setting summary
For HRS we used:
* HRS_SEP_8-08-27b.csv
* HRS_RFQ_8-08-27.csv
* HRS_REX_8-08-27.csv    

REX low energy settings saved as:
* REX-30kV-2008-08-28_HRS204Rn.xml
* BTS-30kV-2008-08-28_HRS204Rn.xml
* EBIS settings attached

REX separator and linac settings saved as:
* None of the saved settings should be used in the future due to low beam transmission and current regulation of the magnets instead of field regulation.

Technical problems
* Target yield dropped a factor 10 between the start of the A=202 and the end of the A=202 run.
* Hall-probes for XSEP.MD100 and XBEN.MD120 behaved non-linearly. Unplugging the power to the power supply to cures the problem.
* The 9-gap amplifier broke during the first night. Was then repaired but broke again on Tuesday morning during an intervention.
* Linac scaling problems and ‘charging up’ behaviour hampered the transmission significantly.

Comments / Lessons learned
* By changing the focusing in the first quads in the HRS separator the RFQ cooler transmission increased from 50 to >72%. The non-response to frequency and amplitude changes also disappeared.
* Difficult to setup low energy when no mass marker in the mass region is available. We managed because of 181Ta out from the target/ion source.
* The machine should have been setup for slow extraction; then we could have increased the breeding time and therefore the efficiency.
* Never touch a running machine.