Investigating Characteristics of Neutron Source Based on Reaction 9Be(d,n) for Fast Neutron Therapy: 1 - Tapa blanda

Sinopsis

Experimental works were conducted beside simulations with MCNP and PACE 4 codes to evaluate the neutron spectra, fluxes and dose rates for different collimation irradiation sizes. The results of neutron flux from Be source and the dose rate were in good agreement with literature. The neutron fluxes and absorbed dose rates differ according to the collimation irradiation field. The experimental and MCNP values are very close to each other for big collimator size, and a little differ for smaller ones. There is a drop of absorbed dose rate value by 10 % between collimators 8.5 x 8.5 cm2 and 4.5 x 4.5 cm2 as results from experiments and 25 % as calculated by MCNP code. That because of the neutron fluxes calculated by MCNP is less than 65measured values in the energy region between 1 MeV and 6 MeV. As a result, that leads us to the better collimation irradiation field to be used for the maximum capability of the neutron beam delivered to the patient.As shown in the results, we can increase the dose rate of neutrons by changing the geometry of inner layer of the collimator, and also we can improve it more by adding a layer of Lead metal (Pb) with certain thicknesses. That leads us to decrease the deuteron beam flux by about 67 %. Or we can decrease the energy of accelerated deuteron ions and save the spending energy on it. In another hand, we can decrease the time of waiting for the patient up to 67 %.We think we can use the same idea for other neutron sources like nuclear reactors, where there are many irradiation canals used to irradiate materials for researching or industrial purposes. If that applies, it will be very useful.

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