128Cd run 29 July - 4 August 2011

 

Target issues
* Target number #454 UC-Ta surf with quartz line (to avoid Cs contamination)
* W-converter (not used during the run)
* Mass markers:  133Cs, Cd
* HRS separator
* Extraction electrode 70 mm (real distance)
* Uht(HRS, CCV)=30.24 kV, Uht(RFQ,CCV)=30.20 kV, Uht(trap, CCV)=30.00 kV, Elec05=175 V

 

Yield measurements (from HRS logbook 28/7-2011):

Preliminary yields are:

Protons on target:

   Y_(128Cd) = 3e5 1/uC

   Y_(128Cs) = 5e4 1/uC

No 128In detectable, detection limit 100 1/uC

Neutron converter:

   No 128In and no 128Cs detectable. Detection limits are 150 1/uC (128In) and 500 1/uC (128Cs)

   Y_(128Cd) = 9e4 1/uC

/AG, CS, TM

 

Experimental issues
*
Beam to Miniball
* IS477


Tuning
* Normal extraction from EBIS 
* REXTRAP timing free-running relative to protons pulses

 

ISOLDE
   For 90 pA of 133Cs transmission from HRS.FC490 to CA0.FC68: 80%.

 

Low energy
   Stable beam

114Cd
   Tperiod120 ms, Tbeamgate=10 ms, Tbreeding=118 ms, Icoll=183 mA

Trap inj. plate=6.0 pA, BTS.FC20 2.8 pA, RFQ.FC20(30+)=6.0 pA => Trap+EBIS efficiency=3.3%

 

Linac transmission and energy: 
   No stripper foils. WITCH magnets 0.1 and 3T.

   Transmission from RFQ.FC20 to XL65.FC50 at 2.82 MeV/u

   - 85.4%              for A/q = 4

   - 75%                  for A/q = 4.2666                                128Cd30+

 

Total transmission (radioactive beam)
HRS.FC490_to_trap x Trap_EBIS x Linac 
0.80*0.033*0.75=2%


Delivered beams

128Cd30+

Tperiod=120 ms, Tbreeding=118 ms, Icoll=183 mA, Ugun=3900 V, Igun=104 uA, running with high EBIS cathode heating (3.02 A, 3.11 V)

NORMHRS=>ISOHRS

Prot.current: 1.64uA 3149ppp

Total cycles: 15/41

RFQ.FC20        2 pA peak

L65.FC50        1.5 pA peak

Miniball        1.5 pA peak, assuming 0.5 pA average -> 1E5 pps

Miniball saw ~1e3 pps. From yield checks and transmission should be ~1e4 pps. -> mostly impurities?

 

126Cd30+

NORMHRS=>ISOHRS

Prot.current: 1.68uA 3086ppp

Total cycles: 15/38

RFQ.FC20        1.7 pA in the peaks

XL65.FC50        1.2 pA in the peaks, assuming 0.5 pA average -> 8E4 pps

Cannot be all Cd -> impurities?

 

Setting summary
For HRS we used:

HRS_SEP_133Cs_30.3kV_2011_07_25.csv

RFQ_133Cs_30.3kV_2011_07_25.csv

REX_RFQ_2011_07_25_133Cs_30Kv.csv


REX low energy settings saved as:

110729_1409_TRAP_HRS_114Cd30+_3.3%.csv

110729_1409_BTS_HRS_114Cd30+_3.3%.csv

EBIS_110729_1412_HRS_114Cd30+_3.3%.csv 

 

REX separator and linac settings saved as:
not saved

 

Technical problems

* Failure of HRS HT (switched HT1 and HT2)

* Poor vacuum in the target (most likely a leak), had to change vacuum interlock threshold and force section valve open to keep running

* Target heating stopped on water interlock, must adjust flow to sufficiently high value (> 200 l/h) to keep enough margin

* RFQ stopped several times on over-temperature, the problem disappeared on its own, no clear explanation (either sensor problem or faulty grid 1 supply i.e. tube not pulsing)

* Several interruptions of 9-gap amplifier

 

Comments / Lessons learned