LEAD LOADED
EJ-256
EJ-256 is a homogeneous, clear plastic scintillator in which lead has been incorporated by means of organometallic chemistry. Typical lead loading ranges from 1% to 5% by weight. Loadings up to 10% have been made but are not recommended. With increasing lead loading, there are corresponding losses in scintillation efficiency and optical clarity of the final plastic.
EJ-256 is best used for gamma detection at energies below 100 keV where there is a significant impact of the lead on attenuation coefficients. This is most strongly evident at 60 keV and lower where the photoelectric cross section is notably enhanced. At these energies, signal amplitudes from EJ-256 are commonly greater than those from an intrinsically brighter plastic scintillator that has no loading with heavy atoms as a result of the photoelectric contribution in the detection process. Detection efficiencies are also notably increased.
EJ-256 is also excellent for dosimetric detection applications. Lead concentrations in the 1-2% range impart a flatness in response down to at least 20 keV.
| PROPERTIES | EJ-256-5% |
EJ-254-1.5% |
| Light Output (% Anthracene) | 34 | 50 |
| Scintillation Efficiency (photons/1 MeV e-) |
5,200 | 7,700 |
| Wavelength of Maximum Emission (nm) | 425 | 425 |
| Decay Time (ns) | 2.1 | 2.1 |
| No. of H Atoms per cm3 (x1022) | 5.20 | 5.21 |
| No. of C Atoms per cm3 (x1022) | 4.62 | 4.68 |
| No. of Electrons per cm3 (x1023) | 3.48 | 3.39 |
| Density (g/cm3) | 1.081 | 1.037 |
| Polymer Base | Polyvinyltoluene | |
| Refractive Index | 1.58 | |
| Softening Point | 75°C | |
| Vapor Pressure | Vacuum-compatible | |
| Coefficient of Linear Expansion | 7.8 x 10-5 below 67°C | |
| Temperature Range | -60°C to 60°C | |
| Light Output vs. Temperature |
At 60°C, L.O. = 95% of that at 20°C
No change from -60°C to 20°C
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Chemical Compatibility
Attacked by: Aromatic solvents, Chlorinated solvents, Ketones, Solvent bonding cements, etc.
Stable in: Water, Dilute acids and alkalis, Lower alcohols, and Silicone greases.
It is safe to use most epoxies with this scintillator.
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