DRAGON Meeting Minutes
June 24 2003

-> Attendees and Previous meeting

Those present by order of appearance: ML(recorder), LB, AB, MA,
JK, HOM, DH, CG, ZL, SE, CW, AL, AO, DO, AH, and CJ.


The minutes of the previous meeting were accepted without
alterations.

-> Hardware

CW: We have brought the chiller down to -16.5 degrees which is
equivalent to -10 degrees on the DSSSD. One does not want to
reduce the temperature any lower than this.


DH: Switched polarities of sextupoles 3 and 4 both of which had
the south pole on the top which is bad. See section entitled
"Wobbler Studies" to understand how the need for this change
came about.

-> Wobbler Studies

MA: We found that sextupoles 3 and 4 were bad by studying the
steering properties of SM0X and SM0Y. This was done using a
position measurement of attenuated beam on the DSSSD. Steering in
x (positive current) moved the beam spot down (y) off the DSSSD
(as well in x) see attachments. MA also showed a plot of steering
in the y direction which seems to be better than x, in the sense
that there is a larger angular acceptance.


DH: questions the effect of steerers 3 and 4 on the BGO vs. strip
correlation. We would like to know if this correlation was the
same as before the power supply changes. The question is do we see
an alternation between left and right going BGOs?

-> CG: Status of Her Work

CG has been looking for an analytical function which would
represent the gammas from the 12C(a,g)16O reaction. She has represented
each peak by a gaussian, and compton events by a smoothly varying
function (for a single energy gamma). See attachments for her
figures, the 4+ state at 11.10 MeV was looked at, which has a
literature branching ratio of 55% +- 23% to the 6.13 MeV
state and 45% +- 11%to the 6.92 MeV state. CG uses a
method outlined in the attachments to normalize her peaks. Then
minimizing her chi^2 fit she gets Branching ratios of 54%
and 46% for the 6.13 and the 6.92 branch respectively. There
are no error bars yet. A modification on the analysis technique
was suggested by AO thus further analysis needs to be done.

-> DRAGON GEANT Simulation Status

AO for CR: CR has now finished putting in the BGO array positions
in GEANT. The first thing he looked at was the 12C(a,g)16O reaction, in which he put in
all the energies and branching ratios we are interested in. He
then looked at the ground state transition with an angular
distribution. The attachments show CR's results, shown are the x
and y final strip positions on the DSSSD, the recoil energy the
emitted photon polar angle and number of BGOs hit for each
reaction.

-> The 12C(a,g)16O Reaction

LB: DH sent out a report on June 23 entitled "Increasing the
Angular Acceptance of DRAGON". LB used the findings from the
wobbler studies to put a rotated elliptical cut on the recoils
coming out of the gas target. See the aforementioned paper by DH
for a complete description. LB finds that even with this cut the
detected recoil energy is still symmetric. DH points out that the
ellipse is merly to guide ones eye, the true cut is not likely to
be so continious.

-> Report by DH

DH: A few suggestions were made in the recent report sent out by
DH on how the DRAGON acceptance could be increased. A need to look
at the design and cost necessary for these suggestions has arised.
AO plays devils advocate and suggests that perhaps further studies
of the acceptance would be sufficient. If we could understand our
losses then one could just account for this in our cross section
data. DH and LB say that 80% losses are unacceptable for any
publication. Serious studies of the ion optics on paper (GIOS) are
needed baring any refashioning of DRAGON.

-> 21Na(p,g)22Mg Reaction Possibilities

DH: There is the possibility of 21Na beam up until next
wednesday. This depends on how much time ops. spends with the
beam. There are some hardware issues which need some attention
such as the gas target, MD1 power supply and the N2 cooler.


SE: We need 2 full shifts of beam given the omega-gamma of
Barry Davids. If SB cannot organize this beam time than SE will.