Abstract
A new approach to neutron detection capable of gathering spectroscopic information has been demonstrated. The approach relies on an asymmetrical arrangement of materials, geometry, and an ability to change the orientation of the detector with respect to the neutron field. Measurements are used to unfold the energy characteristics of the neutron field using a new theoretical framework of compressed sensing. Recent theoretical results show that the number of multiplexed samples can be lower than the full number of traditional samples while providing the ability to have some super-resolution. Furthermore, the solution approach does not require a priori information or inclusion of physics models. Utilizing the MCNP code, a number of candidate detector geometries and materials were modeled. Simulations were carried out for a number of neutron energies and distributions with preselected orientations for the detector. The resulting matrix (A ) consists of n rows associated with orientation and m columns associated with energy and distribution where n . The library of known responses is used for new measurements Y (n × 1) and the solver is able to determine the system, Y = A x where x is a sparse vector. Therefore, energy spectrum measurements are a combination of the energy distribution information of the identified elements of A . This approach allows for determination of neutron spectroscopic information using a single detector system with analog multiplexing. The analog multiplexing allows the use of a compressed sensing solution similar to approaches used in other areas of imaging. A single detector assembly provides improved flexibility and is expected to reduce uncertainty associated with current neutron spectroscopy measurement.
Highlights
Neutron spectroscopy is an important topic of study and is essential to the characterization of neutron radiation fields
The analog multiplexing allows the use of a compressed sensing solution similar to approaches used in other areas of imaging
A single detector assembly provides improved flexibility and is expected to reduce uncertainty associated with current neutron spectroscopy measurement
Summary
Neutron spectroscopy is an important topic of study and is essential to the characterization of neutron radiation fields. Incident neutron field measurements are taken individually for each different diameter sphere and the neutron energy spectrum is obtained using an unfolding technique on the set of detector responses. Unfolding techniques or algorithms such as MAXED [1], GRAVEL [2], or FRUIT [3] unfolding codes have been developed and each has a unique set of characteristics regarding accuracy and applicability. Results from the MAXED algorithm are sensitive to an initial guess [4]. The aforementioned techniques for unfolding are still widely used, new approaches are being developed to provide better accuracy, which are less sensitive to initial conditions, and are less susceptible to error introduced in both the measurement and in the reconstruction. Examples of uncertainty sources include the inability to simultaneously collect detector responses, use of multiple detectors in each sphere, and cross section uncertainty used in the unfolding process
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