144Xe run Sep 2006

Target issues:

* Experiment IS411

* Target #336, UC2, MK7

* Mass markers: Ar/Xe-gas(95/5%)

* HRS separator set-up at 30.2kV

* Yield check:

Ion source efficiency measured and calculated on 132Xe=> 6.3% 

Yield of 144Xe, protons on target: ca 1.8e5/muC.

REX issues:

Isotope run: 144Xe34+

Timing: 198ms breeding time for 34+

Efficiency and energy:

On the trap inj plate 1965 pA 136Xe => HRS transmission 85-88%

System optimised for 136Xe34+, tperiod=200 ms, tbreed=198 ms, tgate=1 ms, fast extraction => 11.5 pA in trap inj plate, 6.5 pA on BTS.FC20 (some Ne) and 34 pA on RFQ.FC20(34+) => Total efficiency 8.7%.

Similar efficiency for slow extraction.

Linac transmission and energy: 70% for A/q=4.2353 at 2.7MeV/u

Currents: With 7/14 pulses/sc, 3E13 p/p

· 1.7 pA averaged after the trap but the major part is Ne and a large very broad bump around A=144. See TOF_144Xe_2006_09_12_gated and ungated1,2.csv in REXTRAP directory.

· After REXEBIS 0.3 pA (34+)

· Beam can be seen clearly on BEN.BO100, no current seen after the linac

· REX low energy part finished with 144Xe setup. After the trap we've 1.7 pA (averaged) but the major part is Ne and a large very broad bump around A=144.

Technical problems:

· Ion source in HRS target repaired twice before the run

· The pick up loop on the linac’s main IH structure is sometime jumping between two values. Need to be sorted out during the shutdown.

· BEN.FC40 was out of order (front part and insulator fell off) making linac tuning very difficult. Design of FC should be improved.

· Long proton interruption during night due to a chain of errors (power supplies and wrong archive values)

· The count rate at the Miniball target went down a factor 2-3 during the last 24 h. The reason could be:

drooping target performance
drooping line performance (broke later during the weekend)
slow detuning of the HRS ion source

Lessons learned:

· One day is not enough to tune the linac.

· Have to use standard settings for HRS separator -> reduce tuning time to REX

· 100% transmission to tape station is possible with plasma source at 30.2 kV

· Poor communication concerning chosen A/q. Fredrik – write clearly, Didier – read carefully.

· A 2-days run is very short for REX.