July 15th, 2003 DRAGON Minutes

Present: Art Olin (AO), Dave Hutcheon (DAH), Mike Lamey (ML), Aaron Bebington 
(AB), Mike Anderson (MA), Dave Ottewell (DFOT), Uwe Greife (UG), Chris Ruiz (CR),
Zhihong Li (ZL), Cassi Galt (CG), Alison Laird (AL), Lothar Buchmann (LB), 
Anthony Olivieri (ATO, recorder), Dario Gigliotti (DG), Cybele Jewett (CJ), 
Joel Rogers (JR)


Corrections to Previous Minutes:

in the section on 21Na Analysis, should say 21Na resonance delivered with 5*10E13 
ions.

near the end of same section, should read "it was mentioned that an?" and "decay 
modes are unknown so it is not possible?"

in the Simulation Calculations, should read, "as shown in Fig 9 and Fig 10 an?" 
and "different colors (if they can be seen)?"



Hardware Status (Solid Target Drive)

- new solid target ladder assembly won't pump down.

- target box not sealing properly with o-ring.  Pumps down to 1 Torr and no 
further.



MCP & Mirror

- timing measurements attempted and 1.5-1.5 ns FWHM for DSSSD vs r.f. Was 
achieved with 1.45 MeV/u 12C.   MCP timing couldn't be done because some negative 
mirror wires broke; they were OK when bias voltages were applied.
possible reason wires broke is consquence of excess tension on frame during 
mounting.
- we can try testing vs some other detector with nanosecond timing.

dE/dx Measurements with Beam

we will use a helium beam with small aperture config.  Stopping power is small 
with helium beam, thus use smaller aperture.

want to measure the effective length for He gas when the large apertures are in 
use.



Acceptance Studies (MA)

a test of the 12C(a,g) yields at different separation tunes showed better
recoil transmitted energy when tuned 1% 'low' than at the nominal tune.

test shows beam not 'getting lost', falling off the DSSSD detector, when 
sextupoles 3 and 4 had the right polarity.

discussion was raised regarding causes for the falling beam.

(for the 12C(a,g) reaction) acceptance issues were raised and possible
solutions to the problem.

       1) add new, smaller quads to the DRAGON beam line.
             2) rearrange and change power settings on current quads.

radical possibility is to move the pumping system 1m or so downstream.

to get the 1?A current we need for tuning and checking acceptance, a lot of 
stripper foils are required.  This will prove difficult for operations.

greater acceptance and a current greater than the 100nA current already being 
used for the 12C(a,g)reaction will be needed for future running.



21Na(p,g)Reaction (DAH)

additional RF cut to clear away the accidental coincidences, leading to 24 events, 
20 were 'golden.'

If the 5.96 MeV resonance is a 0+ analog of 6.24 MeV in 22Ne, an expected cascade 
transition is not seen in the data.

having trouble trying to discriminate between coincidences with gammas and 
randoms, based on TDC data for the BGOs.

detailed analysis for array behavior required.



16O(a,g)20Ne Reaction

-ionization chamber data were shown in the form of fraction of Total Charge 
Collected vs. Anode #.

-other graphs with varying pressure in ionization chamber, beam energy loss, and 
gas target pressure were presented also.
- distributions chang little when changing window thickness and ionization 
chamber pressure.

(UG) 'Do we need to do more work to understand elemental effects on the 
ionization chamber (i.e. energy loss per ion pair depending on Z of beam), or 
are we happy with what we have?'