188,186,184,182Hg run 2008

 

Target issues

* Target number #388 (Mk3 molten lead with STAGISO low intensity beam)

* Beam on target (no converter)

* Mass markers: none

* GPS separator

* Uht(GPS,CCV)=30.06 kV, Uht(GPS,HT_source)=30.08 kV, Uht(GPS,HT_target)=30.0805 kV, Uht(trap)=30.00kV, Elec05=170 V

 

Yield estimations

Estimated yield on 184Hg=2.7e6/uC (Slits In). Measured before the run. Underestimated.

 

Experimental issues

* Beam to Miniball

* IS452

* Delivered beams: 184Hg44+, 186Hg44+, 188Hg45+, 182Hg44+

 

REX Tuning

* Slow extraction from EBIS was used with 186Hg and 188Hg

* REXTRAP timing free-running relative to protons pulses

Low energy

Stable 205Tl from ISOLDE

Tperiod=200 ms, Tbeamgate=50 ms, Tbreed=160 ms (optimised for 42+)

Trap inj plate 8 pA (with beam gate) RFQ.FC20=15 pA (42+)

Trap+EBIS eff = 4.5%

 

Stable 132Xe32+ from ISOLDE

Tperiod=200 ms, Tbeamgate=50 ms, Tbreed=160 ms (not optimised)

GPSFC490 1890pA inj plate 1680pA 88%

Trap inj plate 30 pA (with 2% beam gate) RFQ.FC20=38 pA XL65.FC50 =23pA

Trap+EBIS eff = 3.9%

 

Radioactive 184Hg44+ (16 of 40 proton pulses, 5E12 ppp)

Tperiod=204 ms, Tbreed=200 ms (more or less optimised for 44+)

Trap cyclotron freq optimised 245288 Hz

0.1-0.2  pA on trap inj plate, ~2 pA on RFQ.FC20, ~1.3 pA on XL65.FC50 (1.8E5 part/s)

6.8E4 part/s at Miniball

 

Radioactive 186Hg44+ (10 of 40 proton pulses, 5E12 ppp)

Tperiod=204 ms, Tbreed=200 ms

Trap cyclotron freq optimised 244517 Hz

3.5 pA on trap inj plate, 11 pA on RFQ.FC20, 6.5 pA on XL65.FC50 (9.2E5 part/s)

Trap+EBIS eff = 7%

2.0E5 part/s  at Miniball

 

Radioactive 188Hg45+ (10 of 28 proton pulses, 4.5E12 ppp)

Tperiod=204 ms, Tbreed=200 ms (not optimum for 45+ but better rep rate)

8 pA on trap inj plate, 18 pA on RFQ.FC20, 10 pA on XL65.FC50 (1.4E6 part/s)

Trap+EBIS eff = 5%

3.5E5 part/s  at Miniball

 

Radioactive 182Hg44+ (16 of 40 proton pulses, 5E12 ppp)

Tperiod=204 ms, Tbreed=200 ms

No beam seen on any FC, 2.6E3 part/s  at Miniball

 

 

Linac transmission and energy:

            ~50-60% RFQ.FC20 to XL65.FC50 at 2.85 MeV/u

 

Total transmission (radioactive beam)

GPS.FC490_to_trap x Trap_EBIS x Linac       0.88*0.04-0.07*0.5-0.6=2-3%

 

Setting summary

For GPS we used:

* REX_ GPS_08_09_30.csv

REX low energy settings saved as:

* REX-30kV-2008-09-30_GPS205Tl.xml

* BTS-30kV-2008-09-30_GPS025Tl.xml

 

REX separator and linac settings saved as:

* 081001_1001_186Hg44_Aq4.2272_2.85MeVu_60%_MB.csv

* 081001_1001_SEP_186Hg44_Aq4.2272_2.85MeVu_60%_MB.csv

similar settings (scaled) were used for other A/q

 

Technical problems

* Water interlock of BEN.MQ10-30 quadrupoles failed

* Failure of 9GP grid2 supply at the start of the run

* Low transmission in the linac

* Target broke down in the end of the run. Suspected no lead left in the target container.

 

Comments / Lessons learned

* Need to improve the stability and transmission of the linac (need a lot of steering in the bender section, had to change the 9GP and buncher phase, charging-up effect…)

-> Find the source of instabilities

-> Improve beam transport after the 9GP

* Linac RF was running very stably. No interruption during the run.

* Used Xe beams from ISOLDE with A/q very close to the A/q of the radioactive beams to tune the linac. Only very limited scaling necessary.