Dragon Meeting Minutes - 1st May 2007

Present: CR (Rec), PM, LB, CD, DAH, DO, GR, CV, MJ, AG

-1. New summer students introduced - Aaron Gallant (AG) and Michael Jansz (MJ)
0. Minutes accepted without modifications
1. Hardware
- Roots Blower interlock. Problem observed in last run: RB1B trip after 1 minute 
for no apparent reason. Probable logic error in EPICS caused by drift of GC manometer 
baseline. This could indicate failure of the manometer, which is expensive to replace, 
however temporarily solved by adjusting fine screw on gauge to raise baseline. 
- Linear Drive. No progress in recent weeks, but aim to have completed within the next 
two weeks. 

2. Postmortem (in true sense of the word) of "Tudragon" run.
- gas target performance. Initially chamber was checked for vacuum integrity and found 
eventually to be leak-tight. With the addition of gas, got up to 5-6Torr when pressure 
in pumping tubes gets worse (10**-5Torr), then with more gas suddenly reach a 'sweet spot' 
and can reach up to 10Torr. This was done without the detector frame present. The addition 
of the frame and detectors made the 'sweet spot' disappear, meaning that 10Torr could 
not be reached. Subsequent testing found that it was actually the presence of the cables 
that was causing this problem. Eventually, using Dragon strip detectors and a dummy S2 a 
configuration was found, including cables, where 10 Torr could be reached. This is still 
a concern for the next time.
- detector performance. With the gas present in the cell, and the addition of beam, the 
detector leakage rose rapidly (1.3 uA / min at one point) up to the trip level of 20 uA. 
The s2 detector was the worst affected by this. After beam was switched off the leakage 
current took ~1hr to dissipate. A 200V bias ring was added to attempt some electron 
suppression without success. A light-tight foil was also added so that only alphas would 
get through to the detector, but beam-induced light would not, also without success. There 
was confusion about where the charge is actually coming from. There are several theories, 
and the Edinburgh and York groups are meeting on the 8th May to discuss this. It is thought 
best that we wait until the next available opportunity in August before attempting a second 
run. On Thursday the Dragon Gas Cell will be reinstalled. 

3. Report on Dresden conference "Nuclear Physics in Astrophysics" (CV,GR)
- nothing really new was presented at this conference. There was an interesting talk by 
R. Diehl regarding the status and future of INTEGRAL, which now needs to be refunded ($1m) 
every year. Presently they are just gathering more statistics.    
- A discussion of 3He(a,g) at ERNA was presented, with significantly higher cross-sections 
cf. previous measurement
- 25Mg(p,g) done in Bochum, found same as previous measurement, so AMS has a discrepancy. 
LUNA will attempt 92keV resonance in parallel with AMS. 
- Possible underground lab at Boulby in UK (this is where they do WIMP searches).
- M. Heil talked about s-process and the new French neutron source. 
- Talk on extracting long-lived isotopes from beam dumps, may be of interest for us with 
60Fe for example. 
- New Berlin screening measurements which showed much larger screening effects than seen 
previously. 
- Goetz' talk received good response - it was suggested that he publish for two materials 
at the same time.

4. AOB
- isdaq03 diplay is down.
- isdaq04 will be upgraded at some point in the near future (Scientific Linux).