Abstrak -Abstract -Analysis of chemical compounds and test the magnetic properties of iron sand has been done. The research objective was to determine the content of magnetic minerals and magnetic properties of iron sand found on beaches Ambal. Iron sand samples taken from the beach Ambal. Sand extracted by using a permanent magnet to saparate magnetic and non magnetic sand. Magnetic sand that has been separated mineral content of the type of testing performed by XRD (X-Ray Diffraction) and magnetic properties of the test performed using a VSM (Vibrating Sample Magnetometer). Base on the results of study that magnetic mineral sands of Ambal District Mirit Kebumen contain Magnetite (Fe 3 O 4 ) and Hematite (Fe 2 O 3 ). The calculation of magnetic susceptibility values is 31.88 x10 -6 m3/kg. Based on the calculated value of the relative permeability, magnetic mineral sands Ambal Mirit Kebumen district ferromagnetic category.

Design and optimization of double layer Beam Shaping Assembly (DLBSA) has been conducted using the MCNPX code. The BSA is configured to comply with such a construction having typically a double moderator, a reflector, a collimator, and a filter. The optimization of various combinations of materials that compose the moderator, reflector, and filter yields such quality and intensity of radiation beams that conform to the requirements for Boron Neutron Capture Therapy. The composing materials are aluminum and BiF 3 for moderator, lead and graphite for the reflector, nickel and polyethylene borate for the collimator, and iron and cadmium for the filter. Typical beam parameters measured at the exit of the collimator are epithermal neutron flux of 1.110 9 n/(cm 2 s), the ratio of epithermal neutron flux to thermal neutron and fast neutron flux 344 and 85, respectively, and the values of fast neutron and gamma dose to epithermal neutron flux 1.0910-13 Gycm 2 and 1.8210-13 Gycm 2 , respectively. Analysis of epithermal neutron flux and neutron beam spectrum using the PHITS code reveals that the distribution of epithermal neutron spreads out in the DLBSA. The highest intensity is found in the moderator and decline downstream of the collimator and filter. The spectrum of neutron beams displays a narrow spike with that peaks at 10 keV.

The genetic algorithm method is a new method used to obtain radiation beams that meet the IAEA requirements. This method is used in optimization of configurations and compositions of materials that compose double layered Beam Shaping Assembly (BSA). The double layered BSA is modeled as having two layers of material for each of the components, which are the moderator, reflector, collimator, and filter. Up to 21st generation, the optimization results in four (4) individuals having the capacity to generate the most optimum radiation beams. The best configuration, producing the most optimum radiation beams, is attained by using combinations of materials, that is by combining Al with either one of CaF2 and PbF2for moderator; combining Pb material with either Ni or Pb for reflector; combining Ni and either FeC or C for collimator, and FeC+LiF and Cd for fast and thermal neutron filter. The parameters of radiation resulted from the four configurations of double layer BSA adequately satisfy the standard of the IAEA.