DESIGNING AN AM-BE MINIATURE NEUTRON SOURCE

Neutron with different energies is required in nuclear medicine, radiotherapy and industry. For example, fast neutron is used in radiobiological research and radiotherapy, epithermal neutron in boron neutron capture therapy (BNCT), and thermal neutron in neutron activation analysis (1, 2). Neutrons can be produced from different sources such as nuclear reactors, particle accelerators and isotopic neutron sources. Due to their simplicity of installation, operation and low price, comparing to other neutron sources, isotopic neutron sources have many applications. However, these neutron sources have deficiencies such as low neutron yield and short half life (3). Isotopic neutron sources usually were fabricated in the form of capsules with equal height and diameter (about centimeters), while miniature neutron sources diameters are less than 3 mm. By decreasing the capsules, diameter, the achievement of miniature neutron source will become possible. Traditional radiation treatment in radiotherapy makes use of gamma rays or X-rays. Neutrons can be more effective than gamma and X-rays, due to the fact that they can deposit more concentrated energy at the sub-cellular level, yet, the neutron will damage surrounding normal tissue unfortunately. Miniature neutron sources enable physicians to insert miniature neutron source into the body of the patient with specific devices. At that rate neutrons are slightly emitted into region directly without any damage to the surrounding healthy tissues (4). Oak ridge national laboratory (ORNL) and Isotron, Inc., have co-developed Cf miniature neutron sources suitable for interstitial and intracavitary HDR NBT (5). One of these Cf miniature neutron sources contains 30 |μ|g of Cf in a 2.8mm diameter by 23mm long capsule (6). The interaction between particles can be simulated with Monte Carlo method. In the present study, the experimental results have been