DRAGON meeting minutes: April 15, 2003

Present: DFOT, JR, PM, DH, H.O.Meyer, SE, ZL, AO, W.Liu, CR(scribe), AL, DG, 
LB, CN, JDA, CW

Minutes of previous meeting accepted

Facility Update:
According to ISAC Operations, the replacement of the RFQ tube is on track and 
beam is expected tomorrow (Wednesday 16th) evening.

Current Run Status 12C(a,g)16O 
LB:- Preliminary excitation functions were shown for both cascade & ground 
state. In general OK. More information on efficiency is required. Ratio of 
Coinc./Recoil singles drops with increasing E; not understood. Could be beam 
contamination (16O)?
DH:- Showed plots of recoil singles vs. beam energy. Shows strange behaviour 
(see figs.) Singles seem to have higher E centroid than coincidents. Could be 
backward gammas? Also, singles not centered in DSSSD, but coincident recoils 
are. Possibility of contamination from O again. A possible route for 
contamination through the separator was speculated. Could slits be too wide? 
The possibility of using the MCP to reduce this problem was mentioned.
LB:- Run plan is to continue up to higher energies. The 4+resonance should be 
reached by weekend. Next week should be well into 2+ resonance. When hit 2+ 
resonance, could do some diagnostical exercises.

Harware/Software Issues 
JR:- The elastic monitor spectrum is still not fully understood. The two 
higher energy peaks seem to shift amplitude with beam current. No explanation 
for two peaks known. Rate of peaks doesn't scale with flux, only the pulse 
height scales with flux. Could be induced charge on detector. JR will insert 
a grid in front of detector before Tomorrow night. AO suggested looking on 
oscilliscope at elastic signals. H.O.M suggested problem could be light. JR 
responded detector is supposed to be light tight. If peaks persist after 
addition of grid, some tests could be done with light.

21Na(p,g)22Mg data analysis 
CN:- Looked at new cuts on gamma energy vs. recoil TOF for 775 keV/u run. New 
cut extended down in gamma energy. Target distribution looks better, and two 
peaks are seen in resulting gamma energy spectrum; possible cascades ie, 
branching ratio info there. New cuts on 583 keV/u not as promising. New cut 
on gamma energy and cut on recoil energy. Mean z position still not good; 
resonance at back of target. 
SE will do an independent check on 583 keV/u data.

Other business 
The prospect of Monte-Carlo simulations taking into account gamma angular 
distributions and target effects was discussed. 
It was noted that XSLITC should be kept open at 30mm not 25mm.