Minutes of DRAGON meeting August 22, 2006
Present: JZ, DH (recorder), DO, EOC, CR, CV, MT

1. Minutes of previous meeting
        - no changes noted

2. Hardware  DH
        The third ceramic tube passed its vacuum test last week.  The 
entire set have tested successfully and payment approved.  We should 
install them at the next opportunity (after alpha source work is done and 
key people back from vacation).  This should leave time to test up to 
200kV well before any use of DRAGON in the (yet to be circulated) Fall 
beam schedule.  
        After alpha acceptance work stops, the Final slit box region 
should be checked for leaks because vacuum when section is isolated and 
pumped by its turbo seems higher than in the past.

3. Alpha acceptance measurements  EOC
        Measurments of transmission from Charge focus to Final detector 
position with the "standard" tune and selecting rays (roughly 15-21 mrad) 
are compared with GEANT simulation:
                Up        Down        Left        Right        All
Measured        98        89        53        39        70
Simulation        84        97        94        53        83

(Note: Left,Right are looking _upstream_ towards the source; simulation is 
with the source height adjusted to best match the heights observed on the 
DSSSD 4cm behind the Charge focus.)

        Present measurements are with the source moved 2mm up, which 
centres the (average) height at the Charge slits.  On average, the height 
at the Final focus is now centred but the vertical position still is seen 
to vary with the initial horizontal angle.  
When Q1 is reduced 5% from the "standard" value, the focus in 
both x and y shifts downstream to the design position at the Ch slits.
In the very beginning of DRAGON commissioning it was found that the Q1 
strength had to be increased 10% from the nominal (EPICS readback?) value, 
but the connection with the "standard" Q1 setting now seems questionable.
        Suggested future measurement (Evan leaves us at the end of August) 
is to see if the new source height results in distributions at the Mass 
slits which can be explained in GEANT.

Action items arising from the alpha study:
        - survey; height of MD1 vs mark on S-wall column
        - add markers to magnets for future comparisons using TOTAL system
        - look into photographic film for alpha study where envelope 
becomes large in the second stage of the separator

4. 22Na(p,g)
        - DH produced a RAD (ruler-assisted design) sketch of 'innards' 
for comment by UW collaborators
        - JZ estimated heat load on items at LN2 temperature.  With 
black-body emissivity the radiative heating would be about 60W and the 
2-litre LN2 tank would last only 1.5 hours -> tank,tube surfaces need to 
be low-emissivity.
        - CR has made a CAD figure of the target holder and a cooling 
plate.  He will consult with DO on best size of threaded holes for 
attaching the cooling plate or rods for carrying the 22Na target.
        - DO has talked to Clive Mark (remote handling) about indium for 
improved thermal contact.  CM has no coil, not foil, material but thinks 
coil could be pressed flat into a foil.  
        Action: look into commercial availability/price of In foil

5. Improved pumping at the gas target 
        JZ presented calculations for a compact pumping geometry aimed at 
accepting recoils in a 30-mrad half-angle, with space made free for quads 
closer to the target or for a gas post-stripper.  Three designs were 
shown, with central target lengths of 6 or 10 cm and requiring no new 
pumps or requiring 1-2 additional turbopumps.  The compact design requires 
that 4 turbos be attached left/right/top/bottom on a common support box to 
match their large flange diameters to the short distances between pumping 
tubes.
        Although many design details would have to be worked out (clash 
with BGOs? use of SiN CSbooster?) there at least is a solution in 
principle to the pumping issues.  Ion optics studies are the next thing to 
examine, in order to decide if an upgrade to larger acceptance is 
worthwhile.

6. A possible 25Mg(p,g)26gAl experiment  CV        
        89 resonances were considered in the NACRE compilation, with 
direct measurements having been made down to a resonance at 189 keV.  
Recent AMS studies agree with the gamma work for several resonances, but 
not for the 189-keV one (factor 5 disagreement), which is in the Gamow 
window for novae.  A lower rate for this reaction means lower production 
of 26gAl.
        The NACRE strength corresponds to a yield of 2.5E-15, for a DRAGON 
detection rate of 1 per hour at beam intensity 100 (p)nA.  This would 
present DRAGON with new challenges in beam suppression, particle ID but is 
comparable to the yield suggested for the 15O(a,g)19Ne proposal, for 
example.  The AMS experiment may be repeated? LUNA may try a non-inverse 
measurement?
        The ECR on OLIS would definitely be needed.  We need to lobby to 
get the ECR installation project off 'hold', for experiments such as 
O-17(p,g) and new reactions such as this one or 33S(p,g).

7. Other business, future agendas
        - CR will try to distribute a report on his study of candidate 
reactions before he takes a few days off, with a view to making a 
presentation for the meeting of September 5th.