9C 10C run 2008


Target issues
* Target number #373 CaO, Mk7,
* No mass marker; 13C16O2 gas
* Molecular beam xC+16O
* HRS separator
* RFQ cooler operated in cw mode
* Uht(HRS,CCV)=29910 V, Uht(HRS, HT_target)=29970 V, Anode1=150 V, Uht(RFQ cooler)=29970 V, RFQ extraction=20V, Uht(trap)=29895 V

Yields obtained for 10C+16O in the focal plane of the separator (before the actual run):
-> 15h30 (before tuning the ion source): 2.2e4/uC
-> 16h45 (increased line heating from 400A to 420A): 9.2e4/uC
-> 18h00 (increased target heating from 300A to 320A): 4.6e4/uC
Due to the short half-life no measurements of 9C could be carried out with the tape-station.

During the run 3.0E13 p/p were taken on the target.

Experimental issues
2nd beam line
IS445
Physics with 9C (no beam delivered at the experiment) and 10C

REX Tuning
Keeping molecule in trap, breaking inside the EBIS.
Normal extraction from EBIS
Stripper foil (25 ug/cm2) in front of bender magnet
9,10C3+ out of EBIS, stripping to 9,10C6+ before the bender magnet

Low energy
Stable beam 13C16O

ISOLDE :          HRS.FC490=516 pA, HRS.FC748=310 pA, trap inj plate=250 pA

Trap:                 Beam gate open, Tbreed=18.5 ms, Tperiod=20 ms
trap inj plate=85 pA, BTS.FC20=50 pA

EBIS:                Tbreed=3.5 ms (optimized for C3+), Icoll~160 mA
trap inj.plate: 35pA of 13C16O+, RFQ.FC: 9pA of 13C3+

Efficiencies
through RFQ cooler: 60%
RFQ to trap: 81%
REXTrap: 59%
REXTrap+REXEbis: 8.6%

Linac

Linac transmission: 80% for A/q=3, from RFQ.FC20 to XL20.FC50
Transmission XL20.FC50 to experiment ~50%
Linac energy: 2.89 MeV/u, energy spread +-0.5%

Setting summary (transmissions with 13C16O)

HRS                        (HRS_SEP_8-05-08-eve.csv)

RFQ         60%         (RFQ_8-05-08-scaled.csv)

Transport  83%         (REXHRS_8-05-08-scaled-retuned.csv)

Trap         59%         (REX-30kV-2008-05-11_13C16Obunched_d.xml)

BTS                        (BTS-30KV-2008-05-11_13C16Obunched_d.xml)

EBIS                       (see REX logbook 21:54 Sat 10 May 2007)

SEP                        (080511_1805_SEP_Aq3.333_2.89MeVu_with_stripping_foil)

Trap x BTS x EBIS x SEP 8.6%

Linac        80%         (080511_1805_Aq3.333_2.89MeVu_with_stripping_foil)

Total        3.4%

Beams to users
9C16O (9C3+), 10C16O (10C3+), after stripping A/q=9/6 and 10/6
Tbreed=3.5 ms, Tperiod=20 ms

For 10C16O 10 pA was seen on RA0.FC90 – unknown
No current measured on any other FCs for 9C(O) and 10C(O)

Technical problems
* HRS magnets kept on dropping, particularly HRS.MAG90
* The ISOLDE control system occasionally blocked the readback of various applications (magnet control, FC readback, wiregrids and scanners)
* The pulsing of the HRS HT stopped working

Comments
* The Trap & EBIS set up for continuous injection from the RFQ cooler, but gave poor efficiency.

* Target was retuned for optimum yield, with no effect on downstream tune.

* The Trap was set up for cooling of molecules, but without rescaling the HRS & RFQ beam energies (owing to time pressure). The beam energy for Trap ejection / EBIS injection was therefore non-standard.

* EBIS ejection and Linac ran with standard tunes, optimised for A/q=3. Scaling between 3 and 3.3333 worked ok, with some hand-tuning of the steering.

* No beam of 9C delivered to the experiment. The reason for this is unclear (target yield, ISOLDE or REX).

* The stable beam seen by the experiment at the 10C run was 20Ne10+ scattered on the beam tube after stripping. The experiment concluded it came from the EBIS and the post-analysis confirms that it was 20Ne.

* Apart from the difficulty to transport the beam through the collimator of the experiment (50% transmission loss) the linac was working well.