title: Compounds of 6Li and natural Li for EPR dosimetry in photon/neutron mixed radiation fields.
abstract: Formates and dithionates of 6Li, enriched and 7Li in natural composition of Li offer a possibility to measure the absorbed dose from photons and thermal neutrons in a mixed radiation field for instance at a boron neutron capture therapy (BNCT) facility. Tests with formates and dithionates of enriched 6Li and lithium compounds with natural composition have been performed at the BNCT facility at Studsvik, Sweden. Irradiations have been performed at 3 cm depth in a Perspex phantom in a fluence rate of thermal neutrons 1.8 x 10(9) n cm(-2) s(-1). The compounds were also irradiated in a pure X-ray field from a 4MV linear accelerator at 5 cm depth in a phantom with accurately determined absorbed doses. The signal intensity and shape was investigated within 3 h after the irradiation. A single line spectrum attributed to the CO2- radical was observed after irradiation of lithium formate. An increase in line width occurring after neutron irradiation in comparison with photon irradiation of the 6Li sample was attributed to dipolar broadening between CO2- radicals trapped in the tracks of the alpha particles. A spectrum due to the SO3- radical anion was observed after irradiation of lithium dithionate. The signal amplitude increased using the 6Li in place of the Li with natural composition of isotopes, in studies with low energy X-ray irradiation. Due to the decreased line width, caused by the difference in g(N) and I between the isotopes, the sensitivity with 6Li dithionate may be enhanced by an order of magnitude compared to alanine dosimetry. After comprehensive examination of the different combinations of compounds with different amounts of 6Li and 7Li regarding dosimetry, radiation chemistry and EPR properties these dosimeter material might be used for dose determinations at BNCT treatments and for biomedical experiments. Interesting properties of the radical formation might be visible due to the large difference in ionization density of neutrons compared to photons.
authors.affiliation: Department of Radiation Physics, IMV, Faculty of Health Sciences, SE-58185 Linköping, Sweden. eva.lund@imv.liv.se
authors.forename: E
authors.initials: E
authors.lastname: Lund
authors.forename: H
authors.initials: H
authors.lastname: Gustafsson
authors.forename: M
authors.initials: M
authors.lastname: Danilczuk
authors.forename: M D
authors.initials: MD
authors.lastname: Sastry
authors.forename: A
authors.initials: A
authors.lastname: Lund
mesh_terms: D000409:Alanine / Q000737:chemistry; D016754:Boron Neutron Capture Therapy; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy; D005561:Formates / Q000737:chemistry; D007554:Isotopes; D008094:Lithium / Q000737:chemistry*; D009502:Neutrons; D010315:Particle Accelerators; D019047:Phantoms, Imaging; D017785:Photons; D011827:Radiation; D011829:Radiation Dosage; D013997:Time Factors; D014965:X-Rays
chemical_list: D005561:Formates; D007554:Isotopes; D008094:Lithium; D000409:Alanine