Minutes of DRAGON meeting, September 2nd 2003

Present: Dave Hutcheon (DH), Chris Ruiz (CR) - recorder, Alison Laird (AL), Alex Murphy (AM),
Zihong Li (ZL), Joel Rogers (JR), Dave Ottewell (DO), Mike Lamey (ML), Barry Davids (BD), 
Art Olin (AO), Aaron Bebington (AB), John D'Auria (JD)

1. Facility Status Mini Report:

HS and HB finished checking clearance between solid target ladder and target support.
B. Laxdal planning Sep 4th 2 weeks shutdown: no beam.
Graphite foils may be able to be put on solid target holders. These foils are what are used 
for stripper foils in ISAC line.
If these can't be mounted, our own foils can be floated off their backings and mounted.
Once solid target is deemed OK, plan to run beam: Neon will be available.
May run at same energy as previously for Mike Lamey. A large enough signal is needed for the
MCP to be tested. Low energy Neon considered best choice.

Alex Murphy has tested all but one of the Ultra Cam strip detectors. Am-Cu-Pu alpha source 
lines can be resolved with a resolution of  roughly 5%. These detectors have a protective 
deadlayer which contributes to the resolution degradation. Communication with Tom Davinson
at Edinburgh identified that these detectors are working in the breakdown pressure region. 
However, modern detectors should be able to cope with this. There is still no explanation 
as to why the elastic monitors misbehaved during the 12C(a,g) run.

AO:- Bill Roberts will provide help with the Italian dE-E Chip detectors. Specialised 
electronics are required for these detectors: 8 preamps have been ordered. These will be 
mounted outside of vacuum. Existing shaping amplifier units will be used.
A question arose as to the size of these detectors. It is thought they are around 1 cm**2, 
with 5 separate pads providing segmentation. It was asked if these could be made bigger. It 
is thought that 22x22 mm**2  is the limiting size at present. It also needs to be considered 
what kind of segmentation can be provided (i.e. more pads, horizontal or vertical 
configuration).

2. GIOS Optics calculations (JR) (attachment 1):

All Don Hunter's GIOS files have been recovered. 

Joel shows GIOS tune for 12C(a,g)16O 2.68 MeV centre-of-mass ( 800 keV/u). A comparison of 
1st order and 2nd order predicted envelopes is provided (2nd order corrections). The 
envelope squeeze points are shown. 2nd order aberration corrections are without use of 
sextupoles.
Worrying aspect is when 2nd order corrections become comparable to or larger than the 1st 
order envelope. This happens ate Q10 and MSLITS in this new tune. This is more important in 
quadrupoles as limited by beampipe aperture at these points.

AO mentions that the slits at various points could be used to test the GIOS envelope 
predictions.

A consideration of sextupole corrections to 2nd order aberrations  in the new tune optimises 
to new SX values compared to standard tune, although the trend of 2 small and 2 large field 
values is maintained. However, some of the new sextupole polarities are reversed.

Joel is gradually constraining the recoil envelope with these simulations, by identifying 
troublesome points (e.g. Q9, Q10), correcting them, and then making further corrections where 
envelope consequently becomes larger due to the adjustments: iterative process.
It has been identified that ED1 is a critical point. Also, Q9 and Q10 still have envelopes 
larger than their physical size with this new tune. Joel suggests enlargement of these 
elements.

Also, the position of the final slits could end up changing. Joel’s is not yet ready to take 
beam for this test tune: further investigation with simulation is required, especially 
sextupoles.

3. GEANT simulation of 13C(p,g)14N (AB) (attachment 2):

Aaron shows exp. 14N recoil spectrum at 558 keV/u, shape due to acceptance loss. The energy 
calibration of the spectrum was made by M. Lamey, by adding up separate anode contributions 
in the ion chamber. It is found that the 14N recoils have lost around 1 MeV through the foil 
and deadlayer at the ion chamber entrance. A GEANT  representation of the ion chamber is in 
progress in order to enable the reaction and optics simulation in order to estimate the 
acceptance loss during the experiment, and hopefully correct the yield using this.

4. Other:

The new coop student, Nicole Chorney, will arrive next week.

Brian Fulton (York) has said that the solid target experiment (12C+12C) would run October or 
later.

ECR II is working on the test stand, with reportedly slightly better efficiency than ECR I.

5. Gamma array determination of branching ratios (DH) (attachment 3):

First Dave shows gamma info from the BGO array for the 12C(a,g) Ex-11.52 MeV 2+ resonance 
where branching ratios are known. Spectrum of triggering gamma ray versus secondary gamma 
ray shown, with gammas from different decay paths indicated.

Next, 21Ne(p,g) 7.47 MeV 2,3+ data shown, which has a similar spectrum to the 12C(a,g) data, 
but more complicated decay path (3 routes). The average number of hits in the data is slightly 
more than two.

The 21Na(p,g) data is shown for the 6.25 MeV 4+ resonance, which should have 3 decay paths. The 
full energy (6.25 MeV) is never seen in one detector (g.s transition), and indeed the spectrum 
is more fractured than the other examples. In general just showing that these spectra make sense, 
and our conceptual understanding of them is correct.

Finally, the 21Na(p,g) 5.95 MeV (0+) resonance data: There are perhaps four paths here. We have 
low statistics for these runs. ~6 randoms are expected in plot shown, where we only have 14 counts 
to work with. The average number of hits again is 2.5, larger than expected for 1 or 2 decay paths.

Dave wraps up by suggesting that we will try to estimate the efficiencies relevant to using this 
data from the GEANT simulation.