[en] The objectives of this proposal are twofold. One objective is to design and test (using the OSU Van de Graaff accelerator) a moderator assembly for a thermal neutron source for the treatment of superficial tumors by Boron Neutron Capture Therapy (BNCT). We will identify the current of 2.5 MeV protons which is necessary to treat a patient in less than one hour. Our second objective is to design and thermally test a target for our thermal and epithermal source of neutrons for BNCT. Our work to date in fulfilling these project goals is described in this document. 11 refs., 4 figs., 1 tab

[en] By identifying some of the approximations inherent in the commonly used Boltzmann--Vlasov--Maxwell model for the description of the interaction of radiation with plasmas, the development of alternate models of laser-plasma systems is motivated. A photon kinetic theory model is presented as an alternate description of laser-plasma systems, and its implication regarding laser light absorption and electron transport coefficients (most notably, the electron thermal conductivity) are examined. This photon kinetic theory model includes an equation for the spatial attenuation of the laser light intensity and an equation for the electron distribution function. These equations are coupled by electron--photon interactions; i.e., net electronic and ionic bremsstrahlung and Thomson scattering. This coupling describes the interaction of the fast portion of the system transverse electric and magnetic fields with the electron distribution. The interaction rates for the above processes are calculated according to the Wyld--Pines approach

[en] Measurements of the concentration of radon in the environment using charcoal canisters were first described by George, and these canisters have become the Environmental Protection Agency standard. A calibration factor (CF), relating the detected activity A of the radon daughter ²¹⁴Bi within the canister to the radon concentration in air C_R, has been defined by Watson et al. The purpose of this paper is to examine a kinetic model for the adsorption of radon on a charcoal canister in humid air and to compare its predictions for the dependence of the CF on water mass gain and exposure time with the dependence measured by Watson

[en] The first phase of our research project has as its main goal the development of an image analysis system for Solid State Nuclear Track Detectors (SSNTD) readout. Section I, of this report is an introduction to SSNTDs and image analysis systems for automatic track counting. The development of the image analysis system is described in Section II. The development of our foil holder system is described in Section III. The performance of an image analysis system can only be judged with respect to a particular type of image which is to be analyzed. In order to insure the workability of our image analysis system in analyzing CR-39 SSNTDs, we have made an effort to improve our etching system and our etch procedure. The development of our etching system and our etch procedure is outlined in Section IV. Also included in Section IV are images of protons and alpha particle tracks for our etch procedure. The performance of our image analysis system is reported in Section V for the proton and alpha particle tracks which are reported in Section IV. Also, the performance of the image analysis system is reported for some test images

[en] In boron neutron capture therapy (BNCT), it is the consensus that epithermal neutron beams have advantages over thermal beams in treating deep-seated brain tumors, and large neutron fields have advantages over narrow beams, since whole-brain irradiations are thought to be necessary in many cases. Epithermal neutron sources for BNCT, which include filtered reactor neutron beams and moderated reactor neutron fields, are currently being developed at many institutions around the world. Neutrons with energies between 1 eV and 10 keV are most suitable for treating brain tumors. However, techniques for measuring neutron spectra in a vacuum in this energy range are not well developed. This paper describes a new type of neutron spectrometer that has a set of response functions that peak at equally spaced intervals on a logarithmic energy scale ranging from 1 eV to 10 keV; therefore, neutron spectra (or histograms) in this energy range can be obtained by properly applying spectrum unfolding techniques to the measured data. The spectrometer is applicable for measurements in a vacuum for both narrow neutron beams and wide neutron fields

[en] A stochastic model, based on consensus principles from radiation biology, is used to estimate bone-marrow stem cell pool survival (CFU-S and stroma cells) after irradiation. The dose response model consists of three coupled first order linear differential equations which quantitatively describe time dependent cellular damage, repair, and killing of red bone marrow cells. This system of differential equations is solved analytically through the use of a matrix approach for continuous and fractionated irradiations. The analytic solutions are confirmed through the dynamical solution of the model equations using SIMULINK. Rate coefficients describing the cellular processes of radiation damage and repair, extrapolated to humans from animal data sets and adjusted for neutron-gamma mixed fields, are employed in a SIMULINK analysis of criticality accidents. The results show that, for the time structures which may occur in criticality accidents, cell survival is established mainly by the average dose and dose rate

[en] This is the progress report for the project entitled, ''An Accelerator Neutron Source for BNCT.'' The progress report is for the period from July 1, 1993 to date. The overall objective of our research project is to develop an Accelerator Epithermal Neutron Irradiation Facility (AENIF) for Boron Neutron Capture Therapy (BNCT). The AENIF consists of a 2.5 MeV high current proton accelerator, a lithium target to produce source neutrons, and a moderator/reflector assembly to obtain from the energetic source neutrons an epithermal neutron field suitable for BNCT treatments. Our project goals are to develop the non-accelerator components of the AENIF, and to specifically include in our development: (1) design, numerical simulation, and experimental verification of a target assembly which is capable of removing 75 kW of beam power; (2) re-optimization of the moderator assembly design based on in-phantom dose assessments using neutron spectra calculated in phantom and an energy-dependent neutron Relative Biological Effectiveness (RBE); (3) construction of a prototype moderator assembly and confirmation of its design by measurements; (4) design of the shielding of the accelerator and treatment rooms for an AENIF; and (5) design of a high energy beam transport system which is compatible with the shielding design and the thermal-hydraulic design

[en] It has been observed that the radon concentration in homes does not depend solely on the steady-state ²²²Rn concentration in the soil. An explanation for the lack of correlation between radon concentrations in the soil and in adjacent homes includes factors such as the construction of the homes, their heating systems, and the habits of their occupants. Another explanation, which is proposed in this paper, is that the steady-state concentration of radon in the pore gas does not fully characterize the soil as a radon hazard. Other soil properties, such as its diffusion length for radon and its porosity, may be important. In this paper, the authors have identified the soil properties important in radon transport into the basement of a home by mathematically modeling ventilated basement air enclosed in basement walls and surrounded by soil and by solving the model equations to determine an expression for the basement air radon concentration as a function of the properties of the soil and basement wall

[en] We describe measurements of the gamma-ray and neutron absorbed doses per coulomb of charge on target using a paired ion chamber technique, in mixed radiation fields, for the Ohio State University accelerator-based neutron source. Measurements are made downstream of the target and moderator assemblies. These measurements are compared to Monte Carlo N-particle (MCNP) transport code calculations of the same quantities to verify the calculations of the in-air neutron and gamma-ray absorbed dose components

[en] To assess the potential radon hazard of a new home construction site and the steps (if any) that should be taken to mitigate that hazard, the soil pore gas radon source strength S (i.e., the number of radon atoms emitted into a unit volume of pore gas per unit time), the pore gas radon diffusion length L, and the soil porosity p must be known. Methods exist for measuring the steady-state soil pore gas radon concentration. The purposes of this paper are to analyze the kinetics of the radon concentration in a cavity in the soil, to determine the parameters that affect the kinetics, and to establish and analyze an in situ method for measuring S, L, and p