72Kr run 16-22 August 2011

Target issues
* Target number #456 YO-CP
* Beam on target (no converter)
* Mass markers: noble gas -> He (40%), Ne (20%), Kr (20%), Xe (20%) mixture, leak rate 2.2e‐7 mbar.l/s
* HRS separator
* Extraction electrode 55 mm (real distance)
* Uht(HRS, CCV)=30.11 kV, anode 140 V, Uht(RFQ,CCV)=30.19 kV, Uht(trap, CCV)=30000 V, Elec05=170 V

Yield measurements (from logbook):

Target and line at 301A (1250C) and 386A (1980C) respectively. Anode1 at 140 V and 52 mA. Magnet at 3.2 A. Pressure: 3.5e-7 mbar.

73Kr 7e5 / uC

Heating line from 385A to 405A and anode1 current 92mA.

72Kr 2.2e4 / uC

Experimental issues
* Beam to Miniball
* IS478

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

ISOLDE
For 80Kr transmission from HRS.FC490 to CA0.FC68: 73%. Ion source efficiency for Kr, 12-15%

Low energy
Stable beam

80Kr

TRAP HT=30000 V, Trap gas=7.5 V, Cyclotron frequency 574.0 kHz

With Tperiod=36 ms and Tbreed=33.5 ms (optimised breeding time for 17+)

trap inj plate=17 pA, BTS.FC20=9 pA (53%), RFQ.FC20=17.7 pA for 17+

=> 6.1% (5.6% measured just before the run)

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

Transmission from RFQ.FC20 to XL65.FC50

- 91% for A/q = 4 at 2.25 MeV/u

- 88% for A/q = 4 at 2.85 MeV/u

- 82% for 80Kr19+ (4.2105) at 2.85 MeV/u

Total transmission (radioactive beam)
HRS.FC490_to_trap x Trap_EBIS x Linac
0.70*0.06*0.80=3.3%

Delivered beams

72Kr17+ @ 2.85 MeV/u (from Thu 18/8 night to Fri morning)

for 0.27 uA proton current (1E13 ppp, 1/4 cycles)

Miniball estimate: 200 pps

REX estimate for 2.2e4/uC: 190 pps

Setting summary
For HRS we used:

HRS_SEP_2011-08-10_30110V_80Kr.csv

RFQ_2011-08-15_30190V_80Kr.csv

110818_0937_CA0_30110V_80Kr.csv

REX low energy settings saved as:

110818_2131_TRAP_HRS_72Kr17+.csv

110818_2131_BTS_HRS_72Kr17+.csv

EBIS_110818_2127_HRS_72Kr17+_5.6%.csv

REX separator and linac settings saved as:
110818_2126_SEP_Aq4.2353_72Kr17+_2.85MeVu_MB

110818_2126_Aq4.2353_72Kr17+_2.85MeVu_MB

Technical problems

* 9-gap amplifier failed on Fri 12/8. Grid1 power supply switch failure. After investigation the tube turned out to be faulty (Monday). On Tuesday the amplifier was opened to change the tube and the RF contacts inside the amplifier’s cavity were found broken. The cavity was dismounted and brought to the workshop to repair the contacts (Wednesday). The amplifier was reassembled and restarted on Thursday with a new tube. The Grid1 supply failed again on the same fault. It was decided to replace the switch one more time. On Thursday evening the linac could be restarted at full energy and the beam was delivered to Miniball. Friday morning another Grid1 failure. Run ended. Bertronix intervention planned for the weekend.

* Power cut on Thursday 18/8. Managed to restart ISOLDE and REX within a day and deliver the beam to Miniball. Still some problems with the cryo-pumps and EBIS vacuum controls (had to be restarted manually).

* TPGs for 7-gap and L20 sections lose their memory during power cuts: interlock thresholds have to be reprogrammed.

* EBIS cathode very weak: only 150 mA with > 9 W heating power (nominal 6 W).

Comments / Lessons learned

* Molecular beams, HRS beam energy

* Wanted metallic beam in the correct mass region for the setup, wasn’t available.

* Never give up.