70Cu run 2008
Target
issues
*
Target number #383 UCx, Ta surface ionizer
* Beam ion
target (not converter)
* Mass markers: Rb and Cu
* Cu laser ionised
*
* RFQ cooler operated in cw mode
* Uht(
No target yields
measurements carried on 70Cu
During the
run mostly 2.0-2.8E13 p/p were taken on the target. Mostly 40-45% of the
supercycle pulses.
Experimental
issues
* Beam to Miniball
* IS435
* Isomeric selection of 3- using RILIS
REX Tuning
* Normal extraction from EBIS
* REXTRAP timing free-running relative to protons pulses
Low
energy
Stable beam 87Rb
ISOLDE :
eff= >70% (up to 80% recorded for a higher intensity)
Trap:
Tperiod=30
ms, Tbeam gate=10 ms
Trap inj plate=25 pA, BTS.FC20=18 pA, 72%
EBIS: Tbreed=22 ms (optimised for 17+), Icoll~205
mA
RFQ.FC20(17+)=50 pA, trap+EBIS eff
11.7%
Stable beam 65Cu
Tperiod=100 ms, Tbeam
gate=10 ms, Tbreed=65 ms (optimized for 19+)
Trap
inj plate=8 pA, RFQ.FC20(19+)=30 pA
Trap+EBIS
efficiency=19.7%
Radioactive 70Cu (single isomer, 3E13 ppp,
18 out of 40 pulses)
Tperiod=70 ms, beam gate
open, Tbreed=65 ms (optimized for 19+)
Trap inj plate=18 pA (average),
BTS.FC20=7 pA (average)
RFQ.FC20(19+)= 35 pA (average)
XL65.FC20=22 pA (average, without collimator)
Linac
Linac transmission: 80% for
A/q=3.666, from RFQ.FC20 to XL65.FC50
Linac energy: 2.92 MeV/u
Transmission apparently lower with
radioactive beam 50-60%
A 3mm collimator was inserted in DB7 in
front of Miniball during the run to avoid direct beam on the CD (50%
attenuation?).
Total
transmission (radioactive beam)
0.70 x 0.11 x 0.60? x 0.50? = 2.3%
Setting
summary
For
*
RFQ_Fred_2008_07_25.csv
* RFQ_to_REX_Fred_2008-07-25.csv
REX low energy settings saved as:
* REX-30kV-2008-07-25_65Cu.xml
* BTS-30kV-2008-07-25_65Cu.xml
* EBIS settings attached
REX separator and linac settings saved as:
* 080723_1601_SEP_Aq3.666_22Ne6+_73.41mT.csv
*
080724_1740_Aq3.666_22Ne6+_80%_2.919MeVu_946mT_L65.csv
Beams to
users
70Cu19+,
isomers 3-
Some
contamination of stable 22Ne6+ (A/q=3.6666) from the REXEBIS
70Ga
contamination from ISOLDE, between 30% and 50%
Technical
problems
* Loose
cable at the trap injection plate
*
Occasional problems with BTS.KI140
* Linac
scaling problems and ‘charging up’ behaviour of the beam transmission
* The
amount of shift of delivered beam to the users was reduced due to:
Laser wavelength meter failed
Water leak in booster
Fire in booster
RFQ cooler running out of He gas
Late startup due to parallel experiement
(REX running stable for the complete run)
Comments
* After the
target has taken protons one should tune with 87Rb and not 85Rb
* Linac
problems… scalability, stability of the beam after the 9-gap
* 3 mm
circular collimator at XL65.FC50: need to improve the beam injection in MB
*
Suppression of secondary electrons from the 9-gap cavity using an
electromagnetic deflector was tried with some success
* A very
good REXTRAP transmission could be seen. Possibly due to the cooled beam from
the RFQ cooler. A record overall efficiency of 19.7% for trap+EBIS.
* Trap
efficiency goes down for radioactive beam. Due to ionization of the neon buffer
gas?