44Ar run 1-10 October 2010

Target issues
* Target number #437 UC2C, VD7 cold line
* Beam on target (no converter).

* Mass markers: plasma source
* HRS separator
* Extraction electrode 50 mm (real distance)
* Uht(HRS,CCV)=30130 V, Uht(HRS, HT_target)=30151.2 V, Uht(RFQ)=30200 V, Uht(trap)=30000 V, Elec05=170 V

Yield measurements (from Logbook 30/9 12:28)

A majority of the radioactive beam is released within 1s after p-impact. We have ca 10-15x more 88Kr++ than 44Ar+ in the beam (from gamma line measurements). Yields of 44Ar (from betas, and beam composition deduced from gamma) is about 5e6/muC in the focal plane of the separator, taking 50% transmission to tape station. Even if 132Xe+++ has been reduced thanks to pumping the gas line, likely radiogenic 132Xe+++ will be produced, but we are not able to determine it with present beam diagnostics. /TS/FW/MK

Miniball saw around 1e5 44Ar ions/s in the beginning. Fell later to 3E4 pps.

Experimental issues
* Beam to Miniball
* IS499

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

ISOLDE
HRS in High Resolution mode. Differences in mass: CO2=43.990, 44Ar=43.965. No difference at Miniball with or without HRS.SL675 => no slits used during run.

For 1.6 nA of 36Ar, 40% transmission from HRS.FC490 to the trap inj plate (with HRS.SL470 in?). The high resolution mode explains part of the poor resolution.

Low energy

Stable beam 39K

Tperiod=30 ms, beam gate open, Tbreeding=19.2 ms (optimized for 10+), Icoll=153 mA
Trap inj. plate=7.5 pA, RFQ.FC20(10+)=11.3 pA => Trap+EBIS efficiency=15%

Stable beam 38Ar

38Ar10+ the efficiency is lower than for 39K10+. Reason unknown.

Tperiod=30 ms, Tbeamgate=10 ms, trap inj plate 14 pA

RFQ.FC20 Tbreed Efficiency

10+ 14 pA 21.2 ms (optimised) 10%

11+ 13.5 pA 28.2 ms (almost opt) 8.7%

Tperiod=50 ms, Tbeamgate=17 ms, trap inj plate 14 pA

With longer period time the efficiency from the trap goes down.

12+ 12 pA 43.2 ms (optimised) 7.1%

Tperiod=60 ms, Tbeamgate=20 ms, trap inj plate 14 pA

13+ 11 pA 59 ms (optimised) 6%

Linac transmission and energy: 

92% for 20Ne6+ (A/q=3.333) RFQ.FC20 to XL65.FC50, 2.16 MeV/u (9-gap off)

Total transmission (radioactive beam)
HRS.FC490_to_trap x Trap_EBIS x Linac
0.40*0.06*0.90=2%

Delivered beams

44Ar13+

* Ran on A/q=3.38 (13+) instead of A/q=3.666 (12+) to avoid some remaining 22Ne from going through (part of the run performed with isotopically enriched 20Ne buffer gas).
* Running with 3 pulses out of 39 pulses, 3E13ppp
* 78 pA on the trap inj plate. This is mainly/only CO2. HRS.SL675 open but HRS.WG470 slit in.

* On RFQ.FC20 we see peaks of 3-4E-13 epA for 3E13 ppp, on XL65.FC50 around 4E-13 pA as well.

Setting summary
For HRS we used:
* HRS_SEP_2010_09-28_30290V_high_resolution.csv

* RFQ-2010-09-28_30290V_36Ar.csv

* REX_GPS_2010-09-28_30200V_36Ar.csv

REX low energy settings saved as:
* EBIS_101001_1445_HRS_44Ar13_slowextr_6%.csv

* REX-30kV_2010-09-29_HRS_38Ar13_6%.xml

* BTS-30kV_2010-09-29_HRS_39K10_15%.xml

REX separator and linac settings saved as:
100930_1415_Aq3.3846_44Ar13+_2.16MeVu_MB.csv

100930_1415_SEP_Aq3.3846_44Ar13+_2.16MeVu_MB.csv

Technical problems

* Icoll unstable due to cathode dying, had to inject oxygen to revive/stabilize the cathode. Efficiency was probably affected by cathode fluctuations.

* RFQ cooler suffered from periodical over-current during the setup. Reason unknown.

* Missing 60He gas for the RFQ cooler for part of the experiment so instead running with 57He. Not able to establish a difference in transmission (see REX logbook entry, 6/10-2010, 10:17).

* A leaking 57He bottle for the RFQ cooler caused a radioactive beam stop for 2-3 h.

* X7GP.MQ10 fault: 'Phase Failure'. Beam off for <1/2 h.

Comments / Lessons learned

* The target tests last week showed that the 44Ar+ beam from ISOLDE contained 88Kr++ and 132Xe+++. The krypton content from ISOLDE was a factor 10-15 higher than argon. At Miniball 3400 44Ar is seen and 16 counts of 88Kr, thanks to the shift in CSD. See also Miniball elogbok entry 2/10-2010 12:42. Thus, EBIS works as an effective A/q-filter. See also J. Cederkall and L. Weissman's experiment with Ar, Kr and Xe after the Phoenix breeder.

* The REXTRAP efficiency was not affected by CO2 injection.

* Miniball running with tritium loaded target.