Optimization of filtered neutron beams for the calibration of superheated droplet detectors at the RPI

Superheated droplet detectors (SDDs) have been investigated for applications in neutron dosimetry and spectrometry. Varying the detector temperature, it is possible to change the neutron energy detection threshold of SDDs, thus allowing the use of a single detector to measure neutrons of different energy, without any change of the experimental setup. However, the neutron threshold energy versus temperature curves have to be experimentally determined. The determination of the calibration curves requires the use of monochromatic neutron beams. utron spectrum from a nuclear reactor covers a wide energy range, from meV to several MeV. Beams of quasi-monochromatic neutrons can be generated by filtering neutrons emerging from the core with suitable materials, such as Fe (for 24 keV neutrons) and Si (144 and 54 keV). These materials have windows in their neutron cross-sections, so that neutrons corresponding to these windows are transmitted, whereas neutrons with other energies are attenuated. ort on the MCNP simulation study of passive monochromators of Si + S and Si + Ti for the production of quasi-monochromatic neutron beams of 54 keV ( Si + S ) and 144 keV ( Si + Ti ) . The simulations allowed the purity versus intensity of the neutron beams to be optimized, within the geometrical constraints of the beam port.