Sensors (Jan 2020)
Monitoring Neutron Radiation in Extreme Gamma/X-Ray Radiation Fields
Abstract
The monitoring of neutron radiation in extreme high ≈1014 (#/cm2-s) neutron/photon fields and at extremely-low (≈10−3 #/cm2-s) levels poses daunting challenges—important in fields spanning nuclear energy, special nuclear material processing/security, nuclear medicine (e.g., photon-based cancer therapy), and high energy (e.g., dark-matter) research. Variably proportioned (neutron, gammas, X-ray) radiation, spanning 10−2−109 eV in energy, is omnipresent from ultra-low (Bq) activity levels (e.g., cosmic rays/ bananas), to extreme high (>1020 Bq) levels. E.g., in nuclear reactor cores; in spent nuclear fuel bearing nuclear-explosive-relevant safeguard-sensitive isotopes, such as Pu-239; and in cancer therapy accelerators. The corresponding high to low radiation dose range spans a daunting 1016:1 spread—alongside ancillary challenges such as high temperatures, pressure, and humidity. Commonly used neutron sensors get readily saturated even in modest (<1 R/h) photon fields; importantly, they are unable to decipher trace neutron radiation relative to 1014 times greater gamma radiation. This paper focuses on sensing ultra-low to high neutron radiation in extremely high photon (gamma-X ray) backgrounds. It summarizes the state-of-art compared to the novel tensioned metastable fluid detector (TMFD) sensor technology, which offers physics-based 100% gamma-blind, high (60−95%) intrinsic efficiency for neutron-alpha-fission detection, even under extreme (≈103 R/h) gamma radiation.
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