Minutes of DRAGON meeting, 29 August 2006.

Present:  Ahmed Hussein (AH), Christof Vockenhuber (CV), Dave Hutcheon (DH), 
Dave Ottewell (DFOT), Evan O'Conner (EOC), Goetz Ruprecht (GR), Peter Machule (PM), 
Mike Trinczek (MT) - recorder.


1. Previous minutes:

To be distributed.


2. Hardware and business arising:

DH - Clean-up after alpha studies...  Install the new ceramic tubes.  Check heights of
DRAGON beamline elements (especially MD1 and MD2).  This perhaps can be made easier by
removing a section of TUDA beamline for line of sight to the north wall.  We have conflicting
indications about our target height.
DFOT will coordinate with an alignment person (Bruno?, Bruce?).

DH - Tracking down the parts for the NaI detectors.  Have crystals and PMTs but no bases.
Will need PM to fabricate a mounting system that will preserve location/alignment should
detectors need to be removed and replaced.

CV and GR - The 22Na setup (under the TISOL platform) has borrowed an oscilloscope, pulser,
and dual-spec amp.  Could still use a good, second Ge detector.  Progress has been steady but
slow, hampered by cryopump compressor problems and PM's absence.
Big question:  Does anyone know if we can cool the 60Co source??


3. Ultimate report on alpha-acceptance studies:

EOC has almost completed his workterm report on the alpha-acceptance studies.  Once done,
it will be placed on the DRAGON website.

His five conclusions (clipped from report preview) are:

"

1. DRAGON's gas target needs to be re-aligned to insure that the gas target's axis is on 
axis with the beam coming from ISAC as well as, and possibly more important, the spectrometer 
axis. This ensures that the best part of the incoming beam interacts with the gas but also 
ensures that the EMS will receive particles on axis. 

2. If possible a system wide survey of the present location of every element in DRAGON would 
be useful for future referencing if misalignment issue arise. A survey with a theodo-lite 
concluded that the gas target was high with respect to the beam axis. This is in addition 
to a report which concludes the gas target is lower then the beam line, [4].

3. The  first three elements in DRAGON need to be studied in more detail and corrected in order 
to achieve focus at the mass slits. For excellent beam suppression the slits need to be closed 
as much as possible without clipping any recoils, this can only be done is the recoils are 
actually at a focus at the slit locations. 

4. Further simulations and experiments must be carried out to pinpoint the cause of the 
asymmetry in the  final hit pattern. There are a lot of elements between the mass slits and 
the  final slits so this may require additional detector locations or some alternative means of 
observing the hit patterns. Due to the nature of the asymmetry, a possible cause of this and 
a suggestion for simulations would be to test the effect on the hit pattern due to a rotated 
quadrupole. 

5. Although not included as results in this report, it was found that small changes in the 
ED's voltage can change the hit rate observed at the  final slits. The current method of 
tuning DRAGON's  first ED calls for the centering of the beam on the mass slits, the tuning of 
the  final ED center's the hit pattern on the  final slits. This method does not agree with the 
theoretical settings for the electric dipoles. As a example of this, the ray tracing diagrams 
shown in Figure 3.2 is not centered at the  final slits but rather shifted to negative values 
of x. Since the detector is located 66cm after the focus, this would give a hit pattern 
shifted to high x values (as in Figure 4.7), not centered as the tuning description calls 
for. Figure 5.1 shows the transmission at the  final slits for varying ED2 voltages, the 
theoretical value, based on 80% of the ED1 voltage (81.5kV, which was choosen to center the 
beam at the mass slits), is 65.2 kV. There was no collimator used in these measurements.

"

EOC will CVS his GEANT changes and we will back up any necessary files to the DRAGON ibm00
account.

CV - He and CR will try placing photographic film into the DRAGON beamline to trace
trajectories.  They will start with seeing how the film responds to a collimated alpha source.


4. 22Na update:

DH - Has looked at old photos to try and figure out the spacing of the target mounting 
screws.  Looks like 3/8 x 7/16".  DFOT will search for ladder drawings which should show
the mounting holes.

Seattle has doubts about our plan to have a water-cooled coil mounted on a plate as the
cooling for the target holder.  We think for 10W this should be okay but plan to test this
concept here with a couple of thermocouples and a resistor for heating.  PM to source.
Seattle also doesn't like the idea of In foil as a heat conductor...


5. Other business:

CR's prelim review of possible candidates for future DRAGON studies has been released.

Anuj has circulated his 33S(p,g) proposal.  Please send comments and commitments.