96Kr run 12-14 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

Beam composition for various trapping times (from REX elogbook, 13/7 18:18)

“In the MINIBALL ionisation chamber we saw the following number of counts for various isotopes in 5 min collection time:

Ttrap Kr+Rb Mo Ce Hg

120ms 577 811 117 278

160ms 484 799 98 433

250ms 365 722 49 258

300ms 278 676 57 171

The Ce comes from the electron cathode.”

Experimental issues
* Beam to Miniball
* IS485

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

ISOLDE
For 86Kr cw transmission from HRS.FC490 to CA0.FC68: 60%. Ion source efficiency for Kr, 9.8%

Low energy
Stable beam

181Ta
Tperiod=100 ms, Tbeamgate=40 ms, Cyclotron frequency 251 kHz, gas 7.6 V (pressure inside trap 8.8E-6 mbar) => 51% transmission through the trap.

86Kr

Tperiod=60 ms, Tbeamgate=30 ms, Tbreeding=58 ms, Icoll=192 mA, Trap pressure=7.5 V, Cyclotron frequency 532.8 kHz

Trap inj. plate=15.5 pA, RFQ.FC20(23+)=8.5 pA => Trap+EBIS efficiency=2.4%

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

- 87.9% for A/q = 4

- 77% for A/q = 3.9 39K10+

- 54% for A/q = 4.1563 133Cs32+

Pressure one order of magnitude too high in the RFQ section:

RFQ10.VGP1 5.4e-7 (4.6e-7)

RFQ10.VGP2 1.5e-6 (1.3e-7)

RFQ12.VGF1 1.4e-6 (3.3e-7)

Total transmission (radioactive beam)
HRS.FC490_to_trap x Trap_EBIS x Linac
0.60*0.024*0.70?=1%

Delivered beams

96Kr23+

Tperiod=81 to 250 ms, Tbreeding=80 ms, Icoll=186 mA, Ugun=3900 V, Igun=109 uA, running with high EBIS cathode heating (3.00 A, 3.16 V)

NORMHRS=>ISOHRS

Prot.current: 1.5 to 2 uA 3200E10 ppp

Total cycles: mostly 16/39

No current seen anywhere.

Setting summary
For HRS we used:

* HRS_SEP_2011-07-12_30kV_181Ta.csv
* RFQ_2011-07-12_30kV_181Ta.csv

* REX_RFQ_2011_07_12_181Ta_30040V.csv

REX low energy settings saved as:

* 110712_1835_TRAP_HRS_86Kr23+_1.9%.csv

* 110712_1835_BTS_HRS_86Kr23+_1.9%.csv

* EBIS_110712_1842_HRS_86Kr23_2.4%.csv

REX separator and linac settings saved as:
* 110712_2253_SEP_Aq4.1739_96Kr23_2.82MeVu_L65_WITCH on.csv

* 110712_2253_Aq4.1739_96Kr23_2.82MeVu_L65_WITCH on.csv

Technical problems

* General power cut two days before the run. Numerous problems with vacuum controls and hardware. Difficult to recover.

* Low transmission in the linac (54% for 133Cs32+) due to poor vacuum in the RFQ section.

* Problem with HRS magnet controls, then problems with magnet workingsets and knobs (INCA installation)

* Problem with SL675 controls

* Interruption of target heating (water cooling failure)

* Failure of RFQ cryo-pump

* Several interruption of REXTRAP/BTS vacuum due to false interlocks

* Interruption of quadrupole magnet (IHS.MQ90,100,110) due to over-temperature (during the setup); 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

* Difficult to optimize low energy without a scanning feature in the controls