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Kiff, Scott

Publications and source records attributed to Kiff, Scott.

Open Radiation Monitoring: Conceptual System Design

The Open Radiation Monitoring (ORM) Project seeks to develop and demonstrate a modular radiation detection architecture designed specifically for use in arms control treaty verification (ACTV) applications that will facilitate rapid development of trusted systems to meet the needs of potential future treaties. Development of trusted systems to support potential future treaties is a complex and costly endeavor that typically results in a purpose-built system designed to perform one specific task. The majority of prior trusted system development efforts have relied on the use of commercial embedded computers or microprocessors to control the system and process the acquired data. These processors are complex, making authentication and certification of measurement systems and collected data challenging and time consuming. We believe that a modular architecture can be used to reduce more complex systems to a series of single-purpose building blocks that could be used to implement a variety of detection modalities with shared functionalities. With proper design, the functionality of individual modules can be confirmed through simple input/output testing, thereby facilitating equipment inspection and in turn building trust in the equipment by all treaty parties. Furthermore, a modular architecture can be used to control data flow within the measurement system, reducing the risk of "hidden switches" and constraining the amount of sensitive information that could potentially be inadvertently leaked. This report documents a conceptual modular system architecture that is designed to facilitate inspection in an effort to reduce overall authentication and certification burden. As of publication, this architecture remains in a conceptual phase and additional funding is required to prove out the utility of a modular architecture and test the assumptions used to rationalize the design.

61 RADIATION PROTECTION AND DOSIMETRY↗

Neutron multiplicity detector control circuitry and firmware

Neutron multiplicity detector control logic and firmware may control a neutron multiplicity detector such that higher count rates can be achieved by an order of magnitude of more over conventional control logic and firmware. Count rates of over 1,000,000 cps, and even over 1,500,000 cps, have been realized in some implementations.

Nelson, Mark↗

Fast Neutron Detection using Pixelated CdZnTe Spectrometers

One important important signature of special nuclear materials (SNM) are fast neutrons. Fast neutrons have a low natural background rate and readily penetrate high atomic number materials which easily shield gamma-ray signatures. Thus, fast neutrons provide a complementary signal to gamma rays for detecting shielded SNM. Scattering kinematics dictate that a large nucleus (such as Cd or Te) will recoil with small kinetic energy after an elastic collision with a fast neutron. Charge carrier recombination and quenching further reduce the recorded energy deposited. Thus, the energy threshold of CdZnTe detectors must be very low in order to sense the small signals from these recoils. Here, the threshold was reduced to less than 5 keVee to demonstrate that the 5.9 keV x-ray line from 55 Fe could be separated from electronic noise. Elastic scattering neutron interactions were observed as small energy depositions (less than 20 keVee) using digitally-sampled pulse waveforms from pixelated CdZnTe detectors. Characteristic gamma-ray lines from inelastic neutron scattering were also observed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Improved fission neutron energy discrimination with 4 He detectors through pulse filtering

Our paper presents experimental and computational techniques implemented for 4 He gas scintillation detectorsfor inducedfission neutron detection. Fission neutrons are produced when natural uranium samples are activelyinterrogated by 2.45 MeV deuterium-deuterium fusion reaction neutrons. Fission neutrons of energies greaterthan 2.45 MeV can be distinguished by their different scintillation pulse height spectra since 4 He detectorsretain incident fast neutron energy information. To enable the preferential detection of fast neutrons up to10 MeV and suppress low-energy event counts, the detector photomultiplier gain is lowered and triggerthreshold is increased. Pile-up and other unreliable events due to the interrogating neutronflux and backgroundradiation arefiltered out prior to the evaluation of pulse height spectra. With these problem-specific calibrationsand data processing, the 4 He detector's accuracy at discriminatingfission neutrons up to 10 MeV is improvedand verified with 252 Cf spontaneousfission neutrons. Given the 4 He detector's ability to differentiate fastneutron sources, this proof-of-concept active-interrogation measurement demonstrates the potential of specialnuclear materials detection using a 4 He fast neutron detection system.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Time encoded radiation imaging

The various technologies presented herein relate to detecting nuclear material at a large stand-off distance. An imaging system is presented which can detect nuclear material by utilizing time encoded imaging relating to maximum and minimum radiation particle counts rates. The imaging system is integrated with a data acquisition system that can utilize variations in photon pulse shape to discriminate between neutron and gamma-ray interactions. Modulation in the detected neutron count rates as a function of the angular orientation of the detector due to attenuation of neighboring detectors is utilized to reconstruct the neutron source distribution over 360 degrees around the imaging system. Neutrons (e.g., fast neutrons) and/or gamma-rays are incident upon scintillation material in the imager, the photons generated by the scintillation material are converted to electrical energy from which the respective neutrons/gamma rays can be determined and, accordingly, a direction to, and the location of, a radiation source identified.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗