72Kr
run July 2010
Target
issues
* Target number #429 Y2O3 VD7 + coldline
(Cu)
* Beam on target (no converter)
* Mass markers: 40%He, 20%Ne, 20%Kr, 20%Xe
* HRS separator
* Extraction electrode 63 mm (real distance)
* Uht(HRS,CCV)=30.13 kV, Uht(HRS,HT_target)=30.1525 kV, Uanode=130
V, RFQ=30.20 kV, Uht(trap)=30.00kV, Elec05=180 V
Yield measurements
From the logbook:
Thur 8/7 20000 72Kr/uC, w/o
slits, in the focal plane of the separator.
Mon 12/7 2000 72Kr/uC
Wed 14/7 ???
The experiment suffered from beam contamination, definitely
72Ge from the target (radiogenic or impurity unknown), probably also 72As and
possibly 72Ga. Tried to suppress the Ge contamination
by positioning the HRS.SL675 using the tape station, and to use the HRS user
beam gate. Afterwards isobaric suppression was briefly tried in REXTRAP but the
resonance for Kr maintained unclear.
Experimental
issues
* Beam to Miniball
* IS478
Tuning
* Kr beam, 35% VADIS ion efficiency for Kr
* REXTRAP timing free-running relative to protons pulses
* Lowest possible breeding time to minimize charge exchange
inside REXTRAP
ISOLDE
Transmission
80Kr: HRS.FC490=1.87 nA, Trap
inj plate 1.16 nA => 62%
The
transmission varied between 55% and 70% depending on tuning conditions.
Low energy
Tperiod=26 ms (readback 26.5 ms), Tbreed=24.4 ms, no beam gate
In TOF_78Kr_GasNe76V.dat we see that 35% of the beam is Ne, the rest 78Kr
Trap inj plate=25.5 pA, RFQ.FC20(17+)=26.3 epA => 6.1% efficiency
Trap efficiency alone (Kr) = 25%
Linac
transmission and energy:
87% RFQ.FC20
to XL65.FC50 for A/q 4, 2.82 MeV/u
79%
RFQ.FC20 to XL65.FC50 for 80Kr19+ A/q 4.21, 2.82 MeV/u
Total estimated
transmission (radioactive beam)
HRS/RFQ x Trap_EBIS x Linac
0.65
* 0.06 * 0.8 = 3.1%
Delivered
beams
* 72Kr and 76Kr – no physics due to low count rate, beam
contamination etc
2 pulses out of 39, 3E13 ppp
RFQ.FC20 3 epA
for 76Kr18+ in the pulse, at Miniball FC 2 epA.
No measureable current for 72Kr
Setting
summary
ISOLDE settings saved as:
HRS_SEP_2010-07-13_30280V_80Kr_high_resolution.csv
RFQ-2010-07-13_30280V_80Kr_high_resolution.csv
REX-RFQ-2010-07-06.csv
REX settings saved as:
Trap REX-30kV-2010-07-09-HRS-72Kr.xml
BTS-30kV-2010-07-09-HRS-72Kr.xml
Ebis EBIS_100709_1434-72Kr.csv
Linac 100709_1437_SEP_72Kr17+_2.83MeVu_mb
100709_1437_72Kr17+_2.83MeVu_mb.csv
Technical
problems
* ISOLDE/Booster:
1. Power supplies in CA0 line periodically malfunctioning.
2. The positioning of the electrode was wrong during the initial
setup (CCV given from base plan).
3. Slits HRS.SL675 were left in from Thursday until Saturday
evening => reduced the beam
significantly.
4. Slits HRS.SL240 couldn’t be operated. Prevented
an easy setup of HRS in high resolving mode.
5. Proton beam position on target changed during the run
=> mid-run proton scan required.
6. The Booster had a magnet problem stopping the beam for
>24 h.
* REX low energy:
1. PLC slave on REXTRAP HT platform switched off on
Saturday. Stopped the beam for 2 hours.
* REX linac
1. IHS and 7gap2 amplifiers stopped several time.
2. The power reference value for 7gap1 amplifier was occasionally
stable so the amplifier had to be run in Local mode.
3. Water dripping from the 9-gap heat exchanger.
* Miniball
1. The Miniball target was not
aligned. This was found out after the run when the Miniball
and Sec. 8 were opened. The difficulties steering the beam onto the target
without hitting the CD could possibly be explained by this, as well as the low Coulex rate for 72Kr.
Comments
/ Lessons learned
* Used this target for 78Kr and 129Xe implantations in PET
for Kolkata institute, India (see separate report by J. Pakarinen).
* Miniball is only collecting data
during the EBIS gate and for an equal amount of time off-beam.
* Could operate the EBIS electron beam very stably with an
oxygen leak of 3E-10 mbar.
* The Linac transmission for A/q=4
was as high as 88%, while the 80Kr19+ only reached 79% at best.
* Also changes of the target and line heating affected the beam
transmission through the separator and RFQ so the line had to be retuned.
* REX was running correctly throughout most of the run.