DRAGON meeting minutes, June 3rd, 2003

Present: AB,ML,SE,DG,JDA,JR,DO,DH,AL,LB,CG,AOlin,JK,MA,MPavan,
CR(scribe),AO

1. Sabine Engel, who has recently become Dr. Engel, thanked the DRAGON 
group for supporting her work during her time here. A toast was made to her
continuing success.
Well done Sabine!!

2. Last weeks minutes were accepted.

3. Facility mini status report (DH):
- The DRAGON solid target ladder has been tested. When Wobbler tests 
have been completed it is planned to make this available for operation, 
perhaps for the coming summer period. The possibility of measuring the 
current from the ladder was discussed.

- The Microchannel plate needs to be tested soon. A wire may be broken.
Dave Ottewell and Mike Lamey will remove the device to check.
- The chiller for the DSSD detector has been ordered and is expected to
arrive later this week or early next week. It will have to be plumbed in
next week.
- The ion chamber needs to be reinstalled at some point soon.

4. 12C(a,g)16O (LB and JR):
- Joel showed an analysis of part of the 12C(a,g)16O data over all the 
runs spanning the lower energy range covered in April/May's running.
An excitation function was shown with the Singles Yield (in gammas per 
12C) plotted against the nominal beam energy (corrected to timing).
Since this plot covers only the lower energy range, someone is required
to take up the same analysis for the higher energy range, as Joel will be
away for part of this month.
Energy drifts were seen over time in this data. B. Laxdal thinks this is
not due to stripper foil degradation or operator retuning after a foil 
change. The cause of this is as yet unknown. Also looked at were the 
data for backward gamma angles only, which should have better 
acceptance. There is not much evidence in the plots that there is an 
acceptance problem with the gammas, although the statistics are low. 
There is also not much evidence for the broad resonance at 810 keV/u 
in the data. This should show up strongly. More careful analysis is 
needed. Someone may be required to get involved in checking the 
numbers from Joels 12C(a,g)16O spreadsheet analysis independently. 
Joel gave instructions for use of  this analysis procedure.
- Lothar showed simulation results which illustrate potential acceptance
effects on the recoil peaks for the 2+ resonance in 12C(a,g)16O, which 
has a quadrupole-type angular distribution. The effect of an angular 
acceptance cut is symmetrical in the recoil peak. However, the data 
show a strongly asymmetrical effect which cuts more of the lower energy 
peak. This points to a possible energy cut, which needs to be understood.
DH suggests pursuing a check on the optical focus conditions in the 
separator. Another meeting will take place at 10:00 on Thursday to discuss 
acceptance issues.

Additional:

Further discussions at Thursday's acceptance meeting and Friday's 
Wobbler meeting were had. It is planned to run more Wobbler tests ASAP, 
possibly starting as early as Monday 9th June. Attention will be paid to 
the transmission in the x and y directions, and focus tests will be made.
See Joel's attached memo for gamma-array asymmetry issues.