DRAGON meeting - March 26, 2002

Present: LB, AO, DH, AC*, JR, SB, MC, DO
* recorder

1) Minutes from last week: minor corrections implemented

2) Business arising

- TUDA 21Na+p 822 keV data

LB showed thick target scans of the 822 keV 21Na+p resonance in elastic
scattering data at several angles from TUDA. Fits were performed with
R-matrix, including a gaussian function for the beam energy spread. The best
fit
for the resonance gives a proton width of 5 keV. With this width, an
R-matrix fit of the DRAGON 822 keV data gives a target thickness of 19 keV. It
was noticed that the error bars on the lowest energy data points for the
DRAGON data were too large. Fits to the TUDA data assuming a width of 15 keV
gave fits with chi^squared 4 times worse than that for 5 keV width. With a
15 keV width, a fit to the DRAGON data resulted in a target thickness of
14-15 keV. Fits to the DRAGON data including interference with a tail from a
high energy resonance were also performed.

- Next beam period

West side target station should deliver stable beam on the 10th of April,
but with no contingency for unexpected problems.
Schedule: RIB's on the 12th; stable beams on the evening of the 7th

- Updates on the joblist (DH)

Locks for fence have arrived
No progress on lead shielding
Peter Machule is working on the gas target thermocouple connector
Rolf Keitel is working on EPICS for gas target and vacuum
New EPICS on/off switch for ED power supplies
NMR scope is back

- Gas target studies (DH, DO)

With 1.5 mm apertures on the gas target cell, a reduction in the compression
ratio by a factor of 21 was observed, close to the expected value.  A clean
measurement of dE/dx with the small apertures seems feasible.

- MCP tests (AC, MC)

AC showed a spectrum of TOF between MCP and DSSSD for 148Gd alpha's. The
timing resolution was determined to be 4.6 nsec. JR mentioned
that this number includes effects from timing smearing due to differences
among DSSSD strips. AC also showed position spectra, where changes in
position were measured for different source positions.

3) Beam time plan (DH)

- Stable beams:

21Ne, 260 keV, for tune-up, MCP tests, and pin-hole gas target tests

24Mg, 416 keV, for omega-gamma measurement, and acceptance study with
Rutherford

- 21Na radioactive beam:

822 keV/u revisited: measure dE of target, yield at three energies, possibly
four. In the course of this discussion, it became apparent that AC had
included
systematic errors (charge state distribution error) in the error bars of the
822 keV yield data, instead of fitting only with the statistical errors.
This will be corrected. JR raised concerns regarding the discarding of
certain runs that were
left out due to problems with the beam current normalization. DAH will
examine these runs to provide an independent check. JR also suggested that
one measurement should be taken well off-resonance (this would be the fourth
point).

212 keV resonance revisited: at 215 keV/u gas in vs. gas out measurement;
   at 212.5 keV/u as discussed last time

Measurements on the resonances at ~330, ~460 and ~540 keV, possibly in
this order. Discussion ensued on how much time to spend on the 330 keV
resonance. For this resonance, DAH suggested 4 different energies over 2
days of running, and moving on if no signal is seen. Also for this
resonance, JR suggested running at a higher gas pressure to increase the
target thickness. Discussion followed on whether or not this was feasible,
given our present knowledge of the conditions under which our pumps might
fail.

- Shift schedule

Participants in the run should email DAH stating when they are NOT available
for shifts.





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