108,106Sn run autumn 2006

 

Target issues:

* Used LaC #286, W surface ioniser mk8

* To improve the Sn/In ratio run with consecutive pulses with the beam gate closed, thereafter empty pulses with beam gate open.

 

Yield values from logbook

The 108Sn/108In ratio would increase to 3:1 if gating of 10 s and more would be used. Target temperature could be further increased with great caution.
On mass 106, little Sn is coming on top of large In beam. Maybe a few % seen after 5-10s. There target/line temperature is the only variable for this run. Other strategies could be developped (Quartz, low work function cavity as Ta, and even more exploratory materials) /TS

 

108Sn

MINIBALL taking pulses 6,7,8 and 10 at 1.4E13. Beam gate open 1.5 s after supercycle pulse with 6 s duration. 10 pulses in supercycle. Estimated 60% 108Sn, 40% 108In in the beam./JC

 

106Sn

Short test with pulses 6,7,8 at 3E13 pp gives 44% 106Sn in the beam from miniball laser on/off measurement. Total current approx 1-2 pA after the EBIS. Gate opens 2.5 s after last pulse. Duration 5 s. /JC

 

 

REX issues

isotopes run: 108Sn26+ and 106Sn26+ with lasers

 

breeding time and extraction:      67 ms, peak charge at 26+

                                                slow extraction, 500 us ramping time, FWHM Text=200 us

 

efficiency and currents:

* GPS transmission 100% for stable 115In

 

* With 30 ms beam gate, 70 ms period time and 12 pA 115In+ on the injection plate we have a total (trap+EBIS) efficiency of 9% for In26+. For slow extraction total efficiency 8.5%.

 

* With 6/12 pulses, 3E13 p/p we have for 108Sn:
Trap inj plate: 36-80 pA, BTS.FC20=19-38 pA, RFQ.FC20(26+)=70-145 pA
=> Total efficiency 7-7.5%
No beam gate, slow extraction, 67 ms breeding time, 70 ms period time.

* With 2 pulses/sc, 3.2E13 p/p we have for 106Sn:
4 (+-1) pA in peak on trap inj plate, 2.5 pA in peak on BTS.FC20

7.8 pA (26+) in peak on RFQ.FC20
=> Trap eff <62%, EBIS eff >12%

No beam gate, slow extraction, 67 ms breeding time, 70 ms period time.

 

Linac currents:

With 3/10 pulses/sc, 3.2E13 p/p we have for 108Sn26+ :

RFQ.FC20=       25 – 41 pA

             IHS.FC40=        21 – 37 pA

             BEN.FC40=       16 – 32 pA

             BEN.FC100=     13 – 25 pA

 

With 2 pulses/sc, 3.2E13 p/p for 106Sn26+ :

RFQ.FC20=       0.7 – 9 pA

             IHS.FC40=        1.4 – 8.6 pA

             BEN.FC40=       0.7 – 7 pA

             BEN.FC100=     0.5 – 7 pA

 

Linac transmission and energy: 

                        60% for 108Sn at 2.82MeV/u (not optimised for best transmission)

                        77% for 106Sn at 2.83 MeV/u

 

Comments

* No major problems with REX

* No protons during day time for during the period of setup

* Reference settings for GPS with a surface ioniser

GPS_SEP_6-09-18_30200.csv

REX_2006-09-18.csv

            * Miniball is now using two colimators: more difficult to get the beam through but no            beam on the CD quadrants with empty frame.

 

Technical problems

* A couple of reboots of BD FEC

* The air conditioning for the RF room switched off and caused interlock stops for a couple of amplifiers (9-gap and 7-gap 2)

* The Simatics PLC for the GPS transformer stopped causing an abrupt cool down of target and line

* A stop of a Penning gauge in the REX separator section caused the vacuum interlock for the electrostatic elements in the separator line to switch off. At the same time acqusition for all elements in the linac showed zero. Had to reboot the Linux consolde machine.

 

Lessons learned

* Always set up linac without 9gap at first.