Minutes  DRAGON Group meeting,  30 April 2002

   Present  DO (recorder) MC AO ML JR LB DH AC SE PM DG  AL

1.   Minutes of previous meeting: adopted.

2.   Jobs to be done before 10 May.

 a.  BCM s repaired.  Some discussion of how reproducable their
    locations are when removed and replaced.  Decided that location
    is pretty good because of conflat flanges and bolts.

 b.  Dog houses to be installed at slit locations.  It was noted
    15 microSieverts was measured at mass slit location during
    radioactive beam running.

 c.  TP1/TP3 Pumping tube to be replaced by a larger aperture one.
    
    There was a discussion of custom made heavy metal shielding
    for the neck at the gamma array, but not before 10 May.


3.   Discussion of runs just completed.

    In spite of very limited beam due to Cyclotron and ISAC problems,
    it is felt that the group has brought a successful conclusion to
    the 212 KeV resonance runs.  This running has confirmed that the
    resonance kicks in  lower than the literature value.
    
    We have new data at 850, 857, 871 and 880 keV.  There may be an
    indication of the resonance at higher energy than seen before, 
    but SE cautioned that previous online results also seemed to come
    at a higher energy than the fully analyzed result.  There were 3 runs
    at 857 keV that displayed a consistency between the elastics and
    the beta monitor within ~2 percent.  This may give confidence that
    the beta monitor could be a backup for the elastics. [see attached]


   JR report on DRAGON Midas Acquision system:

 a.   JR gave the group instructions on how to change ODB variables.  
   These instructions are in the computer section of the No Panic book.
   The ODB variables need to be checked at the beginning of a running
   period.  There is a good probability that they will be wrong -- left
   over from calibration runs with beam off.    

 b.   2 culprits are prescale factors and CFD thresholds.  The prescale
   /Equipment/gTrigger/Settings/Prescale_factor  is set at 1 for stable
   beam but at 50 or larger for radioactive beams.  It is better to err
   on the side of too large as we haven't made much use of it anyway.

   /Equipment/gTrigger/Settings/CFD_Thresholds  should be ~2 MeV.  A clue
   of wrong settings is a huge peak at low energies as Spectrum 1000.
   Correct threshold settings for 2 MeV have been determined and saved
   in /data0 as 200thresh.odb; get them by the "ODBEdit" button on the
   MIDAS Netscape interface and type "load 200thresh".  (Other thresholds
   are available in files with names beginning with 100x the desired
   threshold.) 
   An indication of wrong ODB values is the disc filling too quickly.  
   A normal run uses 50 Mb of disc.  With wrong thresholds or prescale
   numbers, disc usage can go to 100 Mb in 1/2 hour.

   [see attachment for JR's "Quicky Tutorial"]