Minutes of DRAGON meeting May 13, 2008
--------------------------------------

Present: CV, CR (chair), UH, PM, LE, SF, CD, DH (recorder), DO, LB

1. Hardware
- the BGO array East half can't be moved into the closed position, 
due to a clash of the support plate with clamps on the gas target.  This 
wasn't a problem in the past, perhaps because added support bars limit 
where the clamps can be located.  Clamps will be modified (cut down) so 
the BGO cart will clear them.  The West BGO cart hits a KF clamp, an easy 
fix.
- last week's problem of excessive deadtime at low trigger rates 
was finally tracked down to a ~1 volt AC component on the 6-volt DC of the 
camac crate.  After the power supply was replace this problem went away.
- the beam now comes to a focus at about -4mm at YSLITC; it used 
to be at +3 mm and the Q1/Q2 height adjustments were expected to put it at 
Y=0 mm.  [expletive, deleted, due to spill of hot liquid]  When the 
theodolite was set up for alignment of the DRAGON beam Attenuator, the 
target cell was off in the vertical but this was blamed on hasty setup of 
the instrument.  This should be re-checked in case the YSLITC situation is 
due to a wrong height at the gas target.
- the Iris cuts slightly asymmetrically with respect to the 
apertures of the gas target.  This should be checked with the CCD after 
the confirmation of target position.
- we need stronger steering on SM1X than before; the adjustments 
of Q1/Q2 were solely in the vertical and should not have affected the X 
direction.  We can check the TOTAL station surveys for signs of x 
movement.
- Gas target turbo TP1 failed during the 27Al run.  Problem turned 
out to be its controller fan, which was replaced.
- the capacitive manometer head on the gas cell (CMGC) was replace 
by a (non-temperature-stabilized) spare.  The zero-offset pot of the old 
one has a broken lead.
- the DRAGON beam Attenuator, located in an upstream box of the 
gas target, attenuated beam by a factor ~20,000, in contrast to a 
measurement with laser transmission which gave attenuation 100,000.  
Another mesh will be added to make it a more useful attenuation factor.

2. The commissioning run with 27Al beam
- primary goal was to collect charge state distribution date for 
use in E810, 23Mg(p,g)24Al.  We got data at 27Al beam velocities chosen to 
match those of the 24Al ions on the resonances of interest.  LE's 
automatic Cup reading software worked and was left 'in charge' during a 
final night of unattended running.  
- second goal was to check out performance of the 2 MCPs and Ion 
Chamber detectors.  This was done with attenuated beam.  The last 12 hours 
were run with 214 keV/u beam to see if the wg=20ueV resonance could be 
distinguished from leaky beam.  The IC ADC spectra show signs of either a 
discriminator threshold or a pedestal; find out which by using a pulser.

3.  Upcoming run with 24Mg beam
- again getting charge state distributions so we will be able to 
use the positron detectors for normalization of the 23Mg beam.  We need 
them only at the beam velocities of the resonances of interest in 
23Mg(p,g)24Al.  We can also check out system at the 24Mg(p,g) resonances 
(Ecm = 214 or 402 keV).

4. 22Na(p,g)23Mg: results from CR's visit last week
- 19F(p,ag) resonances seen in excitation curves taken on a 22Na 
target implanted at TRIUMF.  22Na(p,g) is seen at about the expected yield 
for the resonance at 456 keV, but there is a strong, narrow resonance at 
about 615 keV of unknown origin which masks the 22Na(p,g) resonance.
- the pattern of rastered proton beam on Cu target is square but 
the beam apertures are circular; this is not yet understood
- the 22Na implantation was about 1 mm off-centre; its size is OK.
- next: measure excitation curve for a blank Cu target and also a 
target with Ni flashed over the Cu and implantation at 10 keV.  If this is 
an improvement, UW will send Ni-flashed target chips to TRIUMF for the 
upcoming implantation.
- discussion about the X resonance at ~615 keV: can it not be 
identified from sharp lines in the Ge spectrum => Q-value ?
- UW are using Ortec 672 amplifiers.  They would like to use 673s 
which have better resolution at high counting rates.  Can we provide 3 
673s?
- CR/DO to access ISAC Separator room in prep. for 22Na 
implanation run.

5. AOB
- CR asks for expressions of willingness or non-willingness to be 
on the proposal of Anuj Parikh (26Al target implantation).

6. Action items
* remove obstacles to complete closure of the BGO array (PM,DO)
* check gas target and Iris position with theodolite (DO)
* look up history of gas target height settings (DH)
* check TOTAL data for Q1/Q2 (DH)
* add mesh to Attenuator  (CR,DO)
* check Silena ADCs for pedestal-vs-threshold (CV,LE)
* check and possibly revise 24Mg beam energies requested (CV)
* visit the Mass Sep room (CR,DO)