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BORON LOADED

EJ-339, EJ-339A, EJ-339A2

 

EJ-339

 

Two standard versions of this boron-loaded liquid are offered. EJ-339 contains 5% by weight of natural boron and contains approximately 1% 10B. In EJ-339A the same boron loading compound is enriched to 90 atom percent in 10B and therefore contains 4.6% 10B by weight. Other boron loadings are also available, such as EJ-339A2 with 2.5% 10B by weight.

These scintillators are used for total absorption neutron spectrometry in which the prompt recoil proton pulse from an incoming fast neutron is gated by the boron capture pulse of the same neutron having been thermalized within the scintillator. The 10B(n,a)7Li dominant capture reaction has a 2.31 MeV Q-value which produces a scintillation pulse of amplitude equivalent to that of an electron of about 90 keV. A combination of pulse height, pulse shape discrimination, and delayed time gating techniques may be employed to identify the prompt and delayed neutron pulses from among the gamma background. For neutron energies below 200 keV, the capture time constant is solely determined by the 10B concentration and is inversely proportional to it. The average capture time is about 1.4 µs for EJ-339 and 0.3 µs for EJ-339A. The average time to thermalize and capture a 1 MeV neutron is 2.7 µs for EJ-339 and would be proportionally smaller for EJ-339A.

When these scintillators are supplied in metal or glass cells, very small cells or thin cells should be avoided in order to achieve good neutron capture efficiencies. When supplied in bulk, be aware that the liquids are moisture sensitive and must be carefully handled to avoid even the moisture found in air. Also, to assure good pulse shape discrimination properties, the liquids must be encapsulated under appropriate inert gas conditions.

 

PROPERTIES EJ-339
EJ-339A
EJ-339A2
10B Content (% w/w) 0.95 4.6 2.5
Light Output (% Anthracene) 65 65 70
Wavelength of Maximum Emission (nm)
425 425 425
Specific Gravity 0.92 0.92 0.92
Refractive Index 1.415 1.415 1.415
Flash Point (°C) -8 -8 -8
No. of H Atoms per cm3 (x1022) 5.03 4.98 5.10
No. of C Atoms per cm3 (x1022) 2.90 2.87 3.43
No. of O Atoms per cm3 (x1022) 0.814 0.802 0.432
No. of 10B Atoms per cm3 (x1022) 0.053 0.254 0.137

 

EJ-339 Emission Spectrum