208,220Rn run 14-17 July 2011

Target issues
* Target number #452 UC-CP (line made of Ta, not Mo, to avoid contamination at A=96)
* Beam on target (no converter)
* Mass markers: noble gas -> Ar(20%)/Xe(20%)/Kr(20%)/He(40%), leak rate 1e‐6 mbar.l/s
* HRS separator
* Extraction electrode 53 mm (real distance)
* Uht(HRS, CCV)=30.15 kV, Uht(RFQ,CCV)=30.25 kV, Uht(trap, CCV)=30040 V, Elec05=175 V

Yield measurements

No measurements performed

Ionization chamber result “No beam contaminants from other mass-regions” MB logbook 21:05 14/7

Experimental issues
* Beam to Miniball
* IS506/475

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

ISOLDE
For 220Rn, 3 .0 pA on HRS.FC490, 2.1 pA on CA0.FC68 and 2.0 pA on XTRAP.FC10 =>67% transmission

Low energy
Stable beam

181Ta, XTRAP.FC10=13.5 pA without beam gate

Tperiod=201 ms, Tbeamgate=50 ms, Tbreed 150 ms, Icol 201 mA Efficiency 5.1% (40+)

Tperiod=201 ms, Tbeamgate=50 ms, Tbreed 198 ms, Icol 201 mA Efficiency 6.0% (43+)

Radioactive beam

220Rn

Tperiod=300 ms, no beam gate, Tbreed 298 ms, Icol 200 mA Efficiency 5.9% (49+)

Tperiod=350 ms, no beam gate, Tbreed 348 ms, Icol 200 mA Efficiency 2.6% (52+)

Tperiod=400 ms, no beam gate, Tbreed 398 ms, Icol 200 mA Efficiency 4.4% (52+ not optimum)

Linac transmission and energy: 
No stripper foils. WITCH magnets 0.1 and 3T.

Transmission from RFQ.FC20 to XL65.FC50 at 2.82 MeV/u

- 58% for A/q = 4.209 181Ta43+

Total transmission (radioactive beam)
HRS.FC490_to_trap x Trap_EBIS x Linac
0.67*0.044*0.57=1.7% (for 220Rn52+)

Delivered beams

220Rn52+

for 0.5 uA proton current, 3.2E13 ppp, XL65.FC50 2.6 epA 220Rn52+ on average, same current on Miniball FC, this corresponds to 3.1e5 pps

Miniball saw around 3E5 pps for an average proton current of 1.3 uA.

208Rn50+

Miniball saw 5.6e5 pps for 0.2 uA proton beam.

Setting summary
For HRS we used:

HRS_SEP_2011-07-14_30kV_181Ta.csv

RFQ_2011-07-14_30kV_220Rn.csv

REX_RFQ_2011_07_12_220Rn_30Kv.csv

REX low energy settings saved as:

110714_1448_TRAP_HRS_181Ta40+.csv

110714_1448_BTS_HRS_181Ta40+.csv

EBIS_110714_1823_HRS_220Rn52+_4.4%_slowextr.csv

REX separator and linac settings saved as:

110714_1830_SEP_Aq4.23_220Rn52+_2.82MeVu_L65_WITCH on_57%.csv

110714_1830_Aq4.23_220Rn52+_2.82MeVu_L65_WITCH on_57%.csv

Technical problems

* Low transmission in the linac due to high charge state.

* The pressure in the RFQ section is 5.1E-7 and 5.7E-7 mbar; cryopump not working.

* Problem with HRS magnet controls. Lost the regulation.

* Several power supply interruptions in the BTS line (at least 3) due to false interlock. Total beam interruption around 2 ½ hour.

* Sector valves between trap, EBIS and separator closed without reason (false interlock). Beam stopped to users for ~1 h.

* Interruption on quadrupole magnets X9GP.MQ10,20,30 and IHS.MQ40 due to over-temperature. Reduced the current in the magnets. The cooling station is saturated and the pressure starts to drop. The total flow should be reduced by limiting some less demanding circuit.

Comments / Lessons learned

* Users did an isotope change from 220Rn to 208Rn themselves over the weekend.