Metal-loaded plastic scintillators for gamma-ray spectroscopy
Exemplary embodiments of several new metal-loaded plastic scintillators are reported herein, comprising sterically and electronically isolated organotin additive complexes. Distance-dependent quenching relationships have been used as design criteria for the selection and synthesis of these organometallic additives, resulting in increased light yields and improved gamma-ray energy resolution values relative to previously reported PS/PVT examples. Fast scintillation decay properties have also been characterized in the prepared scintillators, rivaling the kinetics of stilbene-doped bibenzyl and BC-422Q-1% while providing higher light yields than these reference materials.
1. A metal-loaded, liquid or plastic scintillator comprising:
a matrix including a polymer or an aromatic liquid;
an organometallic complex including a heavy metal with an atomic weight between 69 g/mol and 206 g/mol, the heavy metal complexed with an organic ligand having a number average molecular weight of at least 15 g/mol, optionally, the organic ligand is bonded to the polymer; and
a primary and secondary fluorophore;
wherein the organic ligand is exclusive of a carboxylate group.
2. The metal-loaded, liquid or plastic scintillator of claim 1 , wherein the heavy metal is one or more of Tin, Antimony, Germanium, or Iridium.
3. The metal-loaded, liquid or plastic scintillator of claim 1 , wherein the matrix is a plastic polymer comprising polymerized vinyl monomer units and has a weight average molecular (Mw) weight ranging from 40,000 to 1,000,000.
4. The metal-loaded, liquid or plastic scintillator of claim 1 , wherein the matrix is an aromatic material with an aromaticity of 50% to 100% by weight of the total liquid.
5. The metal-loaded, liquid or plastic scintillator of claim 1 , wherein the scintillator is capable of resolving gamma-ray photoelectric absorption peaks in the scintillation pulse-height spectra for energies between 32 keV to 1274 keV, and is capable of discriminating fast neutrons from gamma-rays according to the method of pulse-shape discrimination (PSD), while maintaining a scintillation light yield of at least 6,000 photons/MeVee.
6. The metal-loaded, liquid or plastic scintillator of claim 1 , wherein the scintillator is capable of producing a scintillation light yield of at least 10,000 photons/MeVee light yield and at least 10% energy resolution at 662 keV.
7. The metal-loaded, liquid or plastic scintillator of claim 1 , wherein the scintillator comprises 1.5% to 40% by weight of the heavy metal based on the total weight of the scintillator.
8. The metal-loaded, liquid or plastic scintillator of claim 1 , further comprising a cross-linking additives in concentrations ranging from 0.5% to 15% by weight of the total composition.
9. A metal-loaded, liquid or plastic scintillator comprising:
a matrix including a polymer or an aromatic liquid;
an organometallic complex including a heavy metal with an atomic weight between 69 g/mol and 206 g/mol complexed with an organic ligand; optionally, the organic ligand is bonded to the polymer, the heavy metal and the organic ligand selected to provide the scintillator with the capability of resolving gamma-ray photoelectric absorption peaks in the scintillation pulse-height spectra for energies between 32 keV to 1274 keV, and being capable of discriminating fast neutrons from gamma-rays according to the method of pulse-shape discrimination (PSD) while maintaining a scintillation light yield of at least 6,000 photons/MeVee; and
a primary and secondary fluorophore;
wherein the organic ligand is exclusive of a carboxylate group.
10. The metal-loaded, liquid or plastic scintillator of claim 9 , wherein the heavy metal is one or more of tin, antimony, germanium, or indium.
11. The metal-loaded, liquid or plastic scintillator of claim 9 , wherein the organic ligand includes an aromatic group.
12. The metal-loaded liquid or plastic scintillator of claim 9 , wherein the organometallic complex has the formula (R 1 ) x (R 2 ) 4-x M, where M is tin, antimony, germanium, or indium, and R 1 and R 2 are independently selected from the group consisting of methyl, ethyl, propyl, butyl, isopropyl, tert-butyl, alcohol, phenyl, benzyl, phenylethyl, phenylpropyl, naphthyl, methylnaphthyl, styrl, or methylstyrl, and R 2 may also be selected from a polymerizable group such as styrl, methylstyrl, acrylate, methacrylate, vinyl methacrylate, or furfuryl methacrylate; and x is an integer between 0 and 4.
13. The metal-loaded liquid or plastic scintillator of claim 9 , wherein the scintillator is a plastic scintillator, the plastic scintillator has a light transmittance of 85% to 100% as determined by ASTM D1003-13, and the heavy metal is present in an amount of 1.5 to 40% by weight of the total scintillator.
14. A method of making a metal-loaded liquid or plastic scintillator, the method comprising the steps of:
dissolving an organometallic complex in an aromatic liquid or a monomer;
dissolving a primary fluorophore in the aromatic liquid or monomer;
dissolving a secondary fluorophore in the aromatic liquid or monomer;
if the monomer is present, initiating polymerization of the monomer; and
controlling heating and cooling rates to avoid cracking of the polymerized material;
wherein the organometallic complex includes a heavy metal with an atomic weight between 69 g/mol and 206 g/mol, the heavy metal complexed with an organic ligand having a number average molecular weight of at least 15 g/mol, optionally, the organic ligand being bonded to a polymer formed from the monomer;
wherein the organic ligand is exclusive of a carboxylate group.
15. The method of claim 14 , further comprising adding a radical initiator.
16. The method of claim 14 , further comprising adding a cross-linking agent and controlling the heating to a maximum temperature that is less than the boiling point of the organometallic complex.
17. The method of claim 16 , wherein the cross-linking agent is ethyleneglycol dimethacrylate (EGDMA) and/or 1,4-divinylbenzene in concentrations of 0.5% to 15% by weight of the total solution.
18. The method of claim 14 , wherein the scintillator is capable of resolving gamma-ray photoelectric absorption peaks in the scintillation pulse-height spectra for energies between 32 keV to 1274 keV, while maintaining a scintillation light yield of at least 6,000 photons/MeVee.
19. The method of claim 14 , wherein the scintillator is capable of producing a scintillation light yield of at least 10,000 photons/MeVee light yield and at least 10% energy resolution at 662 keV.
20. The metal-loaded, liquid or plastic scintillator of claim 1 , wherein the metal loaded, liquid or plastic scintillator is mechanically rigid at room temperature with a Shore D hardness of 15 or greater according to ASTM D2240 00.