DRAGON Meeting Minutes for 15-June-2004:

Present: Jonty Pearson, Christof Vockenhuber, Kathryn Oraas, Chris Ruiz,
John D'Auria, Dave Ottewell, Cybele Jewett, Peter Machule, Dario Gigliotti, 
Dave Hutcheon, Jac Caggiano (recorder)

Meeting opened with unanimous approval of last week's minutes.

26Al(p,g) experiment status:

	- Operations had trouble getting 26Mg beam out of OLIS, and are 
finally making headway this morning. ETB (estimated time of beam) is late 
afternoon...
	- JDA shows yield measurements of mass 26 beams delivered to the 8pi 
spectrometer (Figure 1.). The group implanted beam for 12 seconds, then 
measured the decay curve by counting electrons/positrons with plastic 
scintillators. The decay curve shows two distinct portions, the fast decay 
portion attributed to 26Na, and the slow portion attributed to 26mAl.  
Extrapolating these curves to T=0, JDA estimates that there were 1.5x10**7 
26Na atoms and 3.3x10**4 26mAl atoms at the end of implantation, corresponding 
to a ratio of 455:1.
	- Jonty reports that he and DH were puzzling over a mysterious peak 
in one of the elastic monitors, and were debating its origin, noise or real 
particles. At this point, Dave Ottewell informs the group that he has epoxied 
a 241Am source to the ceiling of the target chamber, visible by only one of 
the two elastic monitors.  Mystery solved.
	- A number of new detectors and spectra were successfully added by a 
multitude of people. Two NaI detectors were installed which view the positron 
catcher plate portion of the "horn", installed on the mass slit box. A HPGE 
detector was installed which views the mass slits. The purpose of these 
detectors is to monitor the fraction of isobaric contamination in the form 
of 26Na and 26mAl present in the 26gAl beam. Two 1D NaI spectra, and one 2D 
NaI0xNaI1 spectrum was added for the NaI detectors. Coincidence of the two 
detectors is used for a trigger. The germanium detector is used to monitor 
the 1.809 MeV characteristic gamma ray resulting from beta decay of the 26Na. 
One singles spectra of the HPGe was added. In addition, relevant scaler 
spectra were added, including one measure of accidental NaI coincidence rate, 
obtained by observing the coincidence rate between one NaI detector and a 
1us-delayed version of the second one.
	- Still to be done: calibration of gamma-ray spectra.

Thin foil for MCP/IC status:

	- Christof presented information on two types of foils, carbon and 
diamond-like carbon foils for use with the MCP and Si3N4 foils for use with 
the ion chamber.
	- The diamond-like carbon foils for the MCP come in a thickness of 
0.6 microgram/cm**2, supported on a wire grid. They are mounted on an aperture 
plate with 15mm diameter and have about 90% transmission. Christof presented 
SRIM calculations (Figure 2.)  which showed the much-reduced angular 
scattering of these foils compared to 20 microgram/cm**2 standard carbon 
foils. Ways of measuring this scattering was discussed, including using the 
DSSSD in combination with slits.
	- Next, Christof presented information on the Si3N4 foils (Figure 3). 
The material is basically grown on a silicon wafer, resulting in a thickness 
of ~50 nanometers, or about 17 micrograms/cm**2.  These come mounted on a 
10mmx10mm plate, and are capable of withstanding pressures in the 30-50 mbar 
range. It was not clear how the foils would be mounted in a gas-tight fashion, 
and much discussion ensued.  It was concluded that epoxying the frames to an 
adapter plate and then to the standard window mount was probably preferred, 
as long as care is taken to mask off the windows to prevent epoxy vapor from 
depositing on the foils.

Meeting adjourned at 11:12 a.m.