17F run
Target:
* Large S and Al contaminations
* Low yield of F+ yield for F+ 1.5E5/uC
(assuming
50% transport eff to tape station, in reality
probably higher 75%)
yield for AlF+ 3.4E6/uC
(assuming
52% transport eff to tape station, in reality probably
higher 75%?)
yield for LaF+ none
* All in the F sidebands
Excerption from the
Measured so far 17F, 27Al17F, 40Ca17F and
138Ba17F: 17F+ 1.5E5/uC (assuming 50% transmission to CA0). 27Al17F+
3.4E6/uC (with measured 52% transmission) 40Ca17F+ 8E3/uC (with measured 71%
transmission) 138Ba17F+ <<1E3/uC (with assumed 50% transmission) I.e. the
overall 17F yield looks not bad, but most of the 17F goes into the AlF sideband. Since Al is outgasing
very slowly it would take endless to get the 27Al level sufficiently down to
get more 17F as atomic ions. The other detectable sidebands don't give any
better 17F/background ratio than the atomic mass.
REX :
* 17F5+
* S doubly charged out of the trap
* Why didn't the mysterious beam at A/q=3.4 pass the RFQ?
* Difficult to run with so few particles as 1E5 out of the target
* Beam setup with Na+ to Na7+ 18% in the EBIS
* EBIS CB eff for 950 pA out of trap was 4.9%
* General efficiency numbers:
The Miniball sees 100-150 particles/s. Does that agree with
what we expect?
Target/ion source production yield =
4.6E4 ions/uC (yesterday's yield measurement) => ~
1E5 ions/s (dependent on what transmission to the tape station one assumes
it is 1-1.5E5 ions/s out of the target)
Transmission
(if we trust the
non-suppressed injection plate it is 67%, if we trust the FC it is >30%)
REXTRAP
efficiency 30-40%
EBIS
efficiency to 5+ <10% (most likely 3-5 %)
Linac transmission <70%
Stripping foil efficiency 40%
=> At the Miniball
target one would expect between 150 and absolutely maximum 1200, most
likely 250
Problems:
* BD FEC broke down -
repaired by
* Large
* The end of the Linac was vented, with concequences for the REX mass sep,
BTS and Trap. Ebis unaffected thanks to the fast
closing valve.
* The amplitude for the cyclotron cooling was suppressed for 17F
(anti-resonance for the amplifier).
* A vacuum leak was created in the
Lessons:
* One can get significant amount of 2+ ions out of the REXTRAP.
* Rethink if the yield already from the primary target is too
low for the experiment to be carried out.
* Second different target type as spare if the first doesn't perform
according to expectation, or have the exact target tested before?
* Beam transport and injection to the trap was very sensitive to the
* Oxygen, La, F and LaF are ionised at a different potential within the
the magnet calibration is
maintained
the injection energy into
the trap is correct
For low count beams transport the beam to the tape station with ordinary
separator settings. Thereafter adjust the HTtarget so
a maximum yield is obtained.
* The stripper foil worked fine
Ulli's pre-charaterisation
email below:
Since 17F has only betas it makes probably no sense to set up a gamma
detector. You could try to optimize a bit the
I would see the strategy as follows:
1. Try with 17F+ and check if the 17F+/17O+ ratio is acceptable.
2. If it is just on the edge one could hope to gain a small factor (<<5)
improvement in F/O ratio by using the
Note that for 22Mg/22Na (M/dM=4900) we could gain a
factor 15 by throwing away also a lot of the 22Mg, but here we have M/dM=5700, an MK5 with larger emittance, the
3. AlF+ will definitely not work since an MK5 has
always a huge (many nA) beam
of CO2 on mass 44!
4. Most other molecules risk to have unacceptable background:
9Be17F+/26Mg+/26Al+/26Na+, 40Ca17F+/57Fe+, 88Sr17F+/86Sr19F+,
138Ba17F+/136Ba19F+, etc. the only exception being 139La17F+ (hoping that there
is no significant 140Ce contamination which would give a 140Ce16O+
background).
5. Therefore the target
will have a mass marker with
again the REXTRAP set to a "soft" injection to prevent breakup.