Zn run July 2006

 

Target issues

 

* UC2-C #329, W surface, laser ionization

* mass markers Zn and Rb

* separator setup at 30.2 kV

 

* Yield check

Yield estimation on 80Zn with direct protons on target: 3.10^4/muC

Some contamination of 80Ga (ca 10%)

At the MB is ~3e3 Zn/s, Zn >60% of beam, rest Ga

* Heating of quartz line broken at start, open circuit.

* Experienced radiation alarm when the beam was shot on the converter. Beam only taken directly on target. Large fraction of Rb for the first shift, then it disappeared and only Zn and Ga left.

 

 

REX issues

 

Isotopes accelerated:    stable 22Ne6+ for MB calibration

radioactive 80Zn21+

                                   breeding time 78 ms, peak charge close to 21+ (?)

 

Currents:                      No currents measured on any FC

                                   Beam seen on MCP RFQ.BO30 (stable and radioactive)

                                   Beam seen on MCP BEN.BO40 and 100 (only radioactive)

                                  

Efficiencies:

GPS.FC490 to REXTRAP inj plate: 60% (or up to 100%). Seems to lose 30% in the merging switchyard. The reading of GPS.FC490 was not reliable for currents <150 pA.

 

TRAP efficiency 50% (inj plate = 13pA, BTS.FC20 = 6.4pA)
EBIS efficiency 18.6% (RFQ.FC20 = 25pA for 21+)
Trap+EBIS+sep eff = 9.1%
This is with 68Zn, no beam gate, 80ms period, and 78ms breeding time.

Higher efficiency (12.4% overall) with beam gate on TRAP.

 

            LINAC:             Transmission for A/q=3.666 82%

                                   Energy for A/q=3.666  2.79 MeV/u

 

technical problems:

* GPS magnet had to be recalibrated

* Low transport efficiency from GPS to trap        

            * GPS.FC490 reads unreliable values below 100 pA (a factor 2 too small)

            * Cavities tripped occasionally due to interlock faults

            * Could not restart normally the main IH structure (pb with feedback control / simatic)

            * Mechanical problem on 7-gap1 tuner

            * A QP in the proton beam line stopped -> low target yield

* LA2 was vented by experiment => affected vacuum in source and trap sections => trap control system vent down and was difficult to restart

            * GPIB for Picoamp2 in the REXTRAP stopped working

 

comments:      

* smooth run, no major failures except for LA2 venting incident

* the Ga content is much stronger in the laser on than the laser off spectra. We therefore believe that at least a component of the Ga contamination at the Miniball position arises from beta decay of Zn in the trap & ebis