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%)

Samples – 1 cm thick disks 1” diameter
 Coupled directly to PMT
 Excited with Bi207

1 MeV electron + photon
3000
2500
2000
.1% 3HF #1
.1% 3HF #2
1500
1000
500
0
1
101
201
301
401
501
Bulk Scintillator Light Yield
 Uniformity of sample
preparation is approximately
5% rms


Surface polish
polymerization
 From table, no real change
in light yield for 3HF
concentration > 0.1%
 Next

Scan in both pT
concentration (1-2%) and
3HF concentration (.25-1%)
3HF Concentration
(%)
Relative Light
Yield
0.1
1
0.25
1.07
0.50
1.05
0.75
1.09
1.0
1.09
Fiber Properties

Energy deposited in the fiber is first transferred to the primary
dopant, pT (para-terphenyl)


The secondary (3HF) then absorbs this light and reemits at longer
wavelength


Peak emission – 350 nm
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-ecL





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)
log(1/e)=-ecL = -1.4X104M-1cm-1 X 10-2M X L


A = Absorption
e = molar absorbtivity (for 3HF = 1.4 X 104M-1cm-1 @ 350 nm)
L = length
L= 25 mm
Therefore, a concentration > 0.25% (by wt.) 3HF should not be
needed