DRAGON Meeting Minutes: July 23rd, 2002

Present (in reverse alphabetical order) : CW, AO, ML, CJ, AH, DG, JF, SE, JD, AC, MC, SB
Scribe: CW

Minutes of Previous Meeting: not yet circulated; JD declared with a glance, "they look ok"


JF: MCP Commissioning Results from Friday, July 19th, 2002:

A 360 keV/u pepper-potted 20Ne beam was used.  To acheive a sufficient yet safe beam intensity, attenuators 2, 3, 4 were used in conjunction with Q1 off.   

Several figures were shown and these are attached.

Fig. 1.  YslitF position had little effect on timing peaks.

Fig. 2. Unexpected result:  XslitF  position agreed well with DSSSD horizontal position until XslitF reached  -12mm at which point position on the DSSSD moved to the wrong side of the detector.  This may be explained by beam optics since Q1 was on for the -12mm measurement only.

Figs. 3 & 4. XslitF position displayed double peaking for XslitF=pos; the peaks came together for XslitF=neg.  Width of the total peak, however, remained similar.

Fig. 5. MCP X-position comparing Friday's tests to previous tests with leakies.  Leakies have broader distibution.

Fig. 6. MCP Y-position comparing Friday's tests to previous tests with leakies.  Leakies have broader distibution.

Double peaks in MCP vs. DSSSD timing remain a mystery.  Comments and further tests suggested by group members:

Dirty or inhomogeneous/worn foil?
      -test RF vs. MCP time
      -ML will calculate equivalent thickness of material required to cause delta(t) of ~5ns
      -look at RF vs DSSSD time with MCP out to see timing independent of MCP

Use MCP mask to see position

 
CW: What is happening in the Detector Lab?:

Peltier thermoelectric cooling was introduced (see attachment).  A schematic of the new DSSSD holder that incorporates Peltier cooling was shown (see attachment).  The system uses water to cool the heat sink.  

With the Peltier on and with water running, the cold plate quickly accumulates frost in air which is encouraging.   Proper function of the cooling system required thermal goop to acheive good thermal contact between the Peltier and the cold plate and between the Peltier and the heat sink.    Goop may be dangerous under vacuum.  The use of Indium (a soft, good thermal conductor) in place of goop was suggested by AH and PM.  The possibility of sealing the Peltier to prevent goop from escaping was also suggested.

Concern was raised about the quality of the vacuum at the end of DRAGON and the possibility of condensation on the surface of a cooled DSSSD.  AH suggested using a cold finger.

New electronics have arrived to do tests with 16 strips of the DSSSD (8 front and 8 back) in the Detector Lab, these will also serve as backup electronics for DRAGON.  Proposed tests were touched upon (see attachment).  Suggestions for other tests are welcome as are visitors to the Detector Lab.


AC: Report on Big DRAGON Workshop:

(see attachment)


Beam Requests:

Beam requests for the period Sept2002-Dec2002 must be in by Aug. 2nd. Uwe has submitted a request for 19Ne beam time.  

JD suggested a request for 2 weeks of 21Na beam in Oct. to close the book on 21Na.  

Stable beam will be requested to study a known broad resonance to help understand the
discrepancy between the width measured by TUDA vs. DRAGON for
the 822 keV/u resonance in 21Na(p,g).  Candidate resonances with 21Ne beam on hydrogen are E_cm=733keV/u,  width=4keV/u and  E_cm=1.5 MeV/u,  width=11 keV/u. 

 CJ indicated that she and Uwe are interested in obtaining beam time to investigate charge state distributions.  It was suggested that Wenjie's thesis may contain sufficient data.         


MC: Introduction to 12C + 12C:

Alan Shotter is excited about the idea of using DRAGON to study 12C + 12C following new results from Brian Fulton (who visits TRIUMF Aug. 5th) et. al. on Bromlie resonances.   SB raised concerns about the focus of DRAGON's program.  JD suggested that doing this experiment may have the advantage of getting ISAC a gas stripper in place of a solid stripper.  


Miscellaneous:

Only 5 or 6 IC windows left.  This is not many considering that some of us have not yet broken our quota of windows.  Cary Davids at Argonne has plenty of material for IC windows.  SE will contact him.

These minutes are dedicated to Alan Chen: a fine physicist, a fine volleyball player, and a captious reader of the DRAGON minutes.  We wish you well at McMaster, Alan.