Xe run

Target:

UC2-297

For 12/12 pulses, 3.5E12 p/p, ~100 pA on GPS.FC490

isotopes run: radioactive 138Xe34+, stable 134Xe33+ on top of A/q=4 breeding time: 330 ms, CSD peak at 31+

efficiencies:

GPS to REXTRAP inj plate: 65% or up to 100%. The reading of GPS.FC490 was not reliable.

TRAP: for 128Xe 140 pA on inj plate 85 pA on BTS.FC20, no Ne, tof_2005_05_20.txt => 60%

EBIS: 2.2% eff for 128Xe34+ and 4% for 128Xe32+

Only total TRAP + EBIS efficiency possible for radioactive beam 138Xe34+ (100 pA on GPS.FC490, 85 pA on the inj plate, 45 pA in the peak after the EBIS): 1.6% (up to 2.4% reported)

Also tested with 134Xe: 150 pA on inj plate, 75-80 pA 133Xe33+ out of EBIS => 1.5-1.6% eff.

LINAC: Transmission acceptable at 85%.

energy at 90 kW in 9-gap: 2.85 MeV/u at A/q=4.06.

technical problems:

startup phase

100 times higher noise level on outer drift tube made dry injection difficult

GPS.FC490 strange values

2 transformers to the Linac burned

target had a shortcut from anode to target ground

jittering in the GFAS timing to the Linac

trap control system needs improvements on stability and user interface

CS for the REXEBIS stopped

Linac:

* Good operation of 100 MHz systems after repairs of HV transformers. Problems with 200 MHz remaining, has to be restarted each 2-3 hours. Low level system o.k.

* 200 MHz amplifier had to be repaired and modified before the run. HV transformers for 7Gap1 and 7Gap two broken the week before the run. Therefore setup time of only two days for the whole machine.

* Installation of MCP at target position was impossible due to installation and test of Speidel target chamber.

* Beam optics (spot at target) also o.k. for the moment but has to be improved after the run. Takes at least 2 days with MCP at target position installed. Controls for lenses etc. work much better/faster than last year.

* Problem with large required delays and instable LINAC trigger pulse from EBIS (solved for the moment). Minor problems with 2 magnet power supplies (give wrong status, switch off from time to time), Nicolas will check.

* 2 malfunctioning valves in target area, not yet repaired.

comments:

had to reduce the number of protons to stay within the radiation limits

the relatively high rest gas pressure in the EBIS did not hamper the run (contamination free A/q region)

lesson:

the complete machine must have been working before the first beam time

do not debug new control systems during startup

REX timing has to be improved