Ni run

Target issues:

* Graphite transfer line to speed up the release of short lived isotopes

* To reduce the fraction of Ga, 5 consecutive proton pulses were taken on the target with the beam gate closed, thereafter beam gate open for the remaining part of the super cycle.

* At A=70, the Ga to Ni ratio was too high, Miniball therefore went to 68Ni.

*Ulli Koester in Logbook:

Rough yield analysis gives: 68Ni 1.5E6/uC, 68Ga 1.8E7/uC (typo before!), 69Ni 3E5/uC, 70Ni 5E4/uC, 70Ga 4E7/uC. Thus 68Ni is about 20% lower than last time (RILIS efficiency?), while 69Ni is 3 times higher and 70Ni 5 times higher than last time due to faster release.

Ga background might be the worse problem than low Ni yields, but since Ga is much faster released a good suppression factor (>>10) could be obtained by opening the beam gate only few seconds after the proton impact. This requires however to run with only e.g. every 3rd proton pulse or with e.g. 4 consecutive proton pulses, then 3 seconds delay and then 7.8 seconds of beamgate opening.

REX issues

isotope run: 68Ni19+

breeding time: 98 ms, peak charge at 19+

currents:

* For 70Ni19+ we have 7 pA on BTS.FC20 and 9 pA on RFQ.FC20 (all pulses 1E13 p/p)

* For 68Ni we have 8 pA on trap inj plate, 3.5 pA on BTS.FC20 and 4.6 pA on RFQ.FC20(19+) (all pulses 1E13 p/p)

efficiency:

* GPS.FC490 to REXTRAP:~100%

* Trap 62% for 39K+ from GPS; >50% for 62Ni at 10 Hz; ~50% for 68Ni

* EBIS 20% for 39K10+ from GPS (short cycle); 85Rb22+ gave 9.7% and 85Rb19+ gave 11.5% for 95 ms breeding time; >7% for 68Ni

* Linac 75%

comments:

* The low repetition rate (10 Hz) was imposed by duty cycle limitations in the Linac.

technical problems:

* TRAP running stable the whole run but TRAP CS computer stopped, the hardware kept on running

* EBIS running stable the whole run, small problem with inner steerer

* 200 MHZ amplifier had serious problems with the anode capacitor, could be repaired once more by putting new capton layers, operation afterwards very unstable

* Rest of the Linac and magnet power supplies as well as the control system was running without one single interruption

lessons learned:

* With a good injection into the EBIS for K, high charge states could be reached for Ni.

* For the next 70Ni run it could be beneficial with a stripper foil after the linac to move the Ga charge state distribution away from the one of Ni.

* We have to discuss seriously if we continue operation with the 200 MHz amplifier, rf-group will make long term decision concerning repair.

* The new rf-control is much more than only a quick, temporary solution. It is actually better than what the rf-group has for Linac 2 and 3.