Bulk Scintillator Light Yield  We have prepared samples of bulk scintillator in order to study optimization for the MICE Fiber Tracker  pT(1.25%) + 3HF(.1-1%) u Samples – 1 cm thick disks 1” diameter  Coupled directly to PMT  Excited with Bi 207 u 1 MeV electron + photon

Bulk Scintillator Light Yield  Uniformity of sample preparation is approximately 5% rms u Surface polish u polymerization  From table, no real change in light yield for 3HF concentration > 0.1%  Next u Scan in both pT concentration (1-2%) and 3HF concentration (.25-1%) 3HF Concentration (%) Relative Light Yield

Fiber Properties  Energy deposited in the fiber is first transferred to the primary dopant, pT (para-terphenyl) u Peak emission – 350 nm  The secondary (3HF) then absorbs this light and reemits at longer wavelength  350 nm  525 nm  Light can be lost in the fiber if this absorption length (350 nm  525 nm) is large compared to the fiber diameter  A = 10 -  cL s A = Absorption   = molar absorbtivity (for 3HF = 1.4 X 10 4 M -1 cm 350 nm) s L = length u From these numbers we can determine the 1/e absorption length for a concentration of 0.25% by weight (10 -2 M/liter, MW=240 with 2.5g/l) u log(1/e)=-ecL = -1.4X10 4 M -1 cm -1 X M X L  L= 25  m  Therefore, a concentration > 0.25% (by wt.) 3HF should not be needed