202Rn run July 2010

Target issues
* Target number #431 UC2, VD plasma, cold line
* Beam on target (no converter)
* Ion source gas: 20%-Ne + 20% Xe + 20% Kr + 40% He
* HRS separator
* 17% ion source efficiency reached for Kr with 1.0 bar buffer-gas pressure
* RFQ cooler operated in cw mode
* Extraction electrode 68 mm (real distance)
* Uht(HRS,CCV)=30.13 kV, Uht(HRS, HT_target)=30.1530 kV, Anode=130 V, Uht(RFQ cooler)=30.20 kV, RFQ extraction=0 V, Uht(trap)=30.00kV, Elec05=177 V

202Rn: 6E4/uC (without SL675 inserted, which reduced the beam with a factor 3)

Experimental issues
* Beam to Miniball
* IS465

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

ISOLDE
Transmission including RFQ-cooler: 61% for 181Ta

HRS.WG470 used throughout the run

Low energy
Stable beam 181Ta
Tperiod=140 ms, Tbeamgate=4.2 ms, Tbreeding=129 ms, Icol=234 mA, Pcol 1.6e-9, Pgun 5.4E-10 (O2 injected)
Trap inj. plate=23 pA, RFQ.FC20(40+)=28 pA
Trap+EBIS efficiency=3.0% (43.5% for REXTRAP)

Did not manage to reproduce last year’s efficiency, 6% for the same running conditions.

Linac transmission and energy: 
88% RFQ.FC20 to XL65.FC50 for A/q 4, 2.84 MeV/u
61% RFQ.FC20 to XL65.FC50 for 181Ta42+, 2.84 MeV/u
Full transmission to Miniball. Used the Kr settings (worked fine without retuning).

Total transmission (radioactive beam)
HRS.FC490_to_trap x Trap_EBIS x Linac 
0.60*0.03*0.61=1.1%

Delivered beams

202Rn47+
* Running with 17 pulses out of 38 pulses, 3E13 ppp
* At the REXTRAP injection plate we saw 1 pA in the peak

* RFQ.FC20=0.5 pA peaks, XL65.FC50=0.3 pA

* Miniball FC=0.3pA

* Miniball count rate: 1.4E3 pps (good agreement with yield measurement -> 1E3 pps at MB but not with measured current -> 4E4 pps)

* Evidence for 202Hg contamination

Setting summary
For HRS we used:
* HRS_SEP_2010-07-21_30280V.csv
* RFQ-2010-07-21_30200V_132Xe.csv
* REX_RFQ_2010-07-21.csv

REX low energy settings saved as:
* REX-30kV-2010-07-30_HRS_181Ta.xml
* BTS-30kV-2010-07-29_HRS_181Ta.xml
* EBIS_100730_1751_HRS_181Ta40+_3%_19800

REX separator and linac base settings (A/q=4) saved as:
100722_1839_SEP_Aq4_2.84MeVu_86%_L65.csv
100722_1839_Aq4_2.84MeVu_86%_L65.csv

REX separator and linac settings optimised for MB:

100730_1948_202Rn47+

100730_1948_SEP_202Rn47+

Technical problems

* Poor efficiency for the low energy part, at least a factor two less than last year (not clear why).

* REX was vented on Friday morning following a vacuum incident at Miniball. The EBIS was not affected thanks to the fast shutting valve and the rest of the linac could be restarted without major problem.

* Run stopped prematurely due to the failure of the target line (3/7 of shifts delivered).

Comments / Lessons learned

* Ebis running with O2 gas injection to avoid cathode poisoning (since beginning of the year). Typical pressures Pcol 1E-9 mb and Pgun 4e-10 mb (computer readings).

* Linac transmission lower for heavier beams. Only 61% for 181Ta47+ was 86% for A/q 4 (Ne5+).

* Set-up was done very fast (about 4h on Friday night). Did not have time to set up slow extraction or test ion-ion cooling.