Design considerations for passive gamma-ray spectrometers

Passive gamma-ray spectrometers composed of attenuation filters and integrating detection materials provide important advantages for measurements in high-radiation environments and for long-term monitoring. Each of these applications has requirements that constrain the design of the instrument, such as incident energy range of interest, sensor size and weight, readout method, and cost. The multitude of parameters in passive spectrometer design (e.g., attenuation filter material and thickness, integrating sensor type, number of pixels, reconstructed energy bin structure) results in a large design space to examine. The development of generalized design optimization tools to interrogate this space and to identify promising spectrometer designs is discussed, particularly the methods used to rapidly calculate system transfer functions and the use of genetic algorithms for design optimization. Preliminary measurements to validate the design tools are described, and example results from early design optimization efforts are provided.