Advanced methods of boron neutron capture therapy (BNCT) use an epithermal neutron beam in conjunction with tumor-targeting boron compounds for irradiation of glioblastomas and metastatic melanomas. A common neutron-producing reaction considered for accelerator-based BNCT is 7Li(p,n)7Be, whose cross section increases very rapidly within several tens of keV of the reaction threshold at 1.88 MeV. Operation in the proton energy region near threshold will have an appreciable thick target neutron yield, but the neutrons produced will have relatively low energies that require little moderation to reach the epithermal range desirable for BNCT. Because of its relatively low projected accelerator cost and the portability of the neutron source/target assembly, BNCT based on the near-threshold technique is considered an attractive candidate for widespread hospital use. A systematic Monte Carlo N-Particle (MCNP) investigation of the dosimetric properties of near-threshold neutron beams has been performed. Results of these studies indicate that accelerator proton energies between 1.93 and 1.99 MeV, using 5 cm of H2O moderator followed by thin 6Li and Pb shields, can provide therapeutically useful beams with treatment times less than one hour and accelerator currents less than 5 mA.

In this work we have studied the feasibility of photonuclear production of (47)Sc from (48)Ti via (48)Ti(γ,p)(47)Sc reaction. Photon flux distribution for electron beams of different energies incident on tungsten converter was calculated using MCNPX radiation transport code. (47)Sc production rate dependence on electron beam energy was found and (47)Sc yields were estimated. It was shown that irradiating a natural Ti target results in numerous scandium isotopes which can reduce the specific activity of (47)Sc. Irradiating enriched (48)Ti targets with a 22MeV 1mA beam will result in hundreds of MBq/g activity of (47)Sc and no other isotopes of scandium. Decreasing the size of the target will result in much higher average photon flux through the target and tens of GBq/g levels of specific activity of (47)Sc. Increasing the beam energy will also result in higher yields, but as soon as the electron energy exceeds the (48)Ti(γ,np)(46)Sc reaction threshold, (46)Sc starts being produced and its fraction in total scandium atoms grows as beam energy increases. The results of the simulations were benchmarked by irradiating natural titanium foil with 22MeV electron beam incident on the tungsten converter. Measured (47)Sc activities were found to be in very good agreement with the predictions.

The technique of charged particle radiography has been developed and proved with 800 MeV protons at LANSCE and 24 GeV protons at the AGS. Recent work at Los Alamos National Laboratory in collaboration with the Idaho Accelerator Center has extended this diagnostic technique to electron radiography through the development of an inexpensive and portable electron radiography system. This system has been designed to use 30 MeV electrons to radiograph thin static and dynamic objects. The system consists of a 30 MeV electron linear accelerator coupled to a quadrupole lens magnifier constructed from permanent magnet quadrupoles. The design features and commissioning results of this radiography system are presented. Charged particle radiographyThe technique of charged particle radiography (CPR) has been developed at LANL to utilize 800 MeV protons as a radiographic probe for the diagnosis of explosivelydriven dynamic-events in support of the LANL stockpile stewardship program [1]. The beam optics requirements for CPR lens systems are well understood [2] and schematically shown in Fig. 1.There are two primary requirements of any CPR lens system. First, the lens must provide a point-to-point focus from object to image. Second, it must form a Fourier plane, where particles are radially sorted by the magnitude of the scattering within the object. With this correlation, particles that were scattered to large angles through multiple Coulomb scattering can be removed through collimation at the Fourier plane. The remaining parameters of a CPR lens system design are then determined by the requirements of the radiographic applications. The beam energy must be chosen to penetrate the areal density of the object to be radiographed, and the aperture of the lens system must be chosen to provide sufficient angular acceptance throughout the required field of view.An additional requirement, which is usually the strongest design driver for a CPR lens, is the resolution of the radiography system. This resolution is typically dominated by chromatic aberrations due to energy spread in the injected beam in combination with the spread of energy loss through the object due to areal density variations of the object. Improved spatial resolution is achieved by reducing second order chromatic aberrations [3], T 126 in TRANSPORT notation. In order to compare the relative resolution of magnifying lens designs it is convenient to define the normalized chromatic aberration coefficient, C = T 126 /m, where m is the magnification factor of the lens. The normalized chromatic aberration coefficient is then proportional to the resolution limitations of the lens system due to second order chromatic aberrations.0168-583X/$ -see front matter Ó

Laser-Compton scattering (LCS) experiments were carried out at the Idaho Accelerator Center using the 5 ns (FWHM) and 22 MeV electron beam. The electron beam was brought to an approximate head-on collision with a 29 MW, 7 ns (FWHM), 10 Hz Nd:YAG laser. Clear and narrow x-ray peaks resulting from the interaction of relativistic electrons with the Nd:YAG laser second harmonic line at 532 nm were observed. We have developed a relatively new method of using LCS as a nonintercepting electron beam monitor. Our method focused on the variation of the shape of the LCS spectrum rather than the LCS intensity as a function of the observation angle in order to extract the electron beam parameters at the interaction region. The electron beam parameters were determined by making simultaneous fits to spectra taken across the LCS x-ray cone. This scan method allowed us also to determine the variation of LCS xray peak energies and spectral widths as a function of the detector angles. Experimental data show that in addition to being viewed as a potential bright, tunable, and quasimonochromatic x-ray source, LCS can provide important information on the electron beam pulse length, direction, energy, angular and energy spread. Since the quality of LCS x-ray peaks, such as degree of monochromaticity, peak energy and flux, depends strongly on the electron beam parameters, LCS can therefore be viewed as an important nondestructive tool for electron beam diagnostics.

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