Results on Wrapping Test
               Jingtang HE
             (September 2002) 
                         
  We made a wrapping test by using Tyvec, Al-Mylar, Milipore, Milipore plus 
  one layer of Al-Mylar, two layers of Milipore, two layers of Teflon and two
  layers of Teflon plus one layer of Al-Mylar as reflector and Cosmic Ray as
  radiation source. The white copy paper was used as reference. We took 5 
  days cosmic ray data by using copy paper as reflector to test the stabiliy
  of the set up. All of data was taken by the same crystal and PMT, coupled by
  optical grease. About 24 hour data taking is used as a period of a run.
   
  1) Set Up.(see Fig.1.)
   
  2) Results.(see Fig.2.)
  The mean value and sigma for pedestal and cosmic ray peak are obtained from
  the fitting by a Gaussian function.
  --------------------------------------------------------------------------
  File Name     Pedestal     Cosmic Ray peak
    reference   mean  sigma  mean   sigma  C-Ped     Change       Comment
  crystal_5513  512.61 2.94  848.78 76.36 336.17  -6.01 -1.8%   Copy Paper
  crystal_5514  512.22 2.60  847.22 77.04 335.00  -7.18  -2%
  crystal_5515  511.88 2.61  853.12 78.37 341.24  -0.94 -0.3%
  crystal_5516  511.72 2.65  854.24 77.47 342.52  +0.34 +0.01%
  crystal_5517  511.54 2.56  867.53 76.33 355.99  13.81  +4%
  -----------------------------------------------------------------------------
  Average       511.99 2.67  854.19 77.11 342.18                Copy Paper
  -----------------------------------------------------------------------------
  tyvec_5519    511.18 2.41  918.08 83.85 406.90  64.72 +18.9%  Tyvec
  mylar_5521    510.83 2.33  909.66 86.92 398.83  56.65 +16.6%  Al-Mylar
  millipo_5524  511.03 2.33  956.34 98.96 445.31 103.13 +30.1% Milipore,no gap
  Onemilli5529  512.20 3.01  944.98 84.17 432.78  90.60 +26.5% 1-layer Milipore
  -----------------------------------------------------------------------------
  crystal_5531  509.29 1.74  975.75 91.74 466.46 124.23 +36.3% Milipore + Mylar
  crystal_5533  509.43 1.84  973.63 96.26 464.42 122.02 +35.7%
  crystal_5534  513.13 2.32  977.90 89.94 464.78 122.60 +35.8%
  crystal_5535  513.00 2.33  987.58 82.82 474.58 132.40 +38.7%
  -----------------------------------------------------------------------------
  crystal_5539  679.94 3.63  1175.6 95.41 495.66 153.48 +44.9% 2-layer Milipore
  -----------------------------------------------------------------------------
  crystal_5541  677.48 3.16  1084.4 88.79 406.92  64.74 +18.9% 2-layer Teflon
  crystal_5551  680.85 3.14  1097.7 107.2 416.85  74.67 +21.8% 2-Teflon + Mylar

  3) Mechanical Properties and Handling Difficulties
  -----------------------------------------------------------------------------
                 Tyvec       Al-Mylar      Millipore            Teflon
  -----------------------------------------------------------------------------
  Mechanical     Very        Very        Easy to split            
  Properties     Good        Good          open
  -----------------------------------------------------------------------------
  Handling       Easy       Difficult   Difficult to shape      Difficut to
  Difficulties   to shape   to shape    and easy to split open  shape
  -----------------------------------------------------------------------------
   
  4) Suggestion 
  Summing up all information above, I would like to suggest to use one layer 
  of Milipore plus one layer of Al-Mylar or two layers of Milipore as reflector 
  in PrimEx experiment, since it can give more light, that will improve the 
  energy resolution, but it is difficult to handle, because Milipore is easy to
  split open.