arXiv subjects

K. Koehler

Publications and source records attributed to K. Koehler.

4 recordsLinked to original sources

arXiv2024

Decay Energy Spectrometry for Improved Nuclear Material Analysis at the IAEA NML

Decay energy spectrometry (DES) is a novel radiometric technique for high-precision analysis of nuclear materials. DES employs the unique thermal detection physics of cryogenic microcalorimeters with ultra-high energy resolution and 100$\%$ detection efficiency to accomplish high precision decay energy measurements. Low-activity nuclear samples of 1 Bq or less, and without chemical separation, are used to provide elemental and isotopic compositions in a single measurement. Isotopic ratio precisions of 1 ppm - 1,000 ppm (isotope dependent), which is close to that of the mass spectrometry, have been demonstrated in 12-hour DES measurements of ~5 Bq samples of certified reference materials of uranium (U) and plutonium (Pu). DES has very different systematic biases and uncertainties, as well as different sensitivities to nuclides, compared to mass-spectrometry techniques. Therefore, the accuracy and confidence of nuclear material assays can be improved by combining this new technique with existing mass-spectrometry techniques. Commercial-level DES techniques and equipment are being developed for the implementation of DES at the Nuclear Material Laboratory (NML) of International Atomic Energy Agency (IAEA) to provide complementary measurements to the existing technologies. The paper describes details of DES measurement methods, as well as DES precision and accuracy to U and Pu standard sources to discuss its capability in analysis of nuclear safeguards samples.

physics.ins-det↗

arXiv2018

The PROSPECT Reactor Antineutrino Experiment

The Precision Reactor Oscillation and Spectrum Experiment, PROSPECT, is designed to make both a precise measurement of the antineutrino spectrum from a highly-enriched uranium reactor and to probe eV-scale sterile neutrinos by searching for neutrino oscillations over meter-long baselines. PROSPECT utilizes a segmented $^6$Li-doped liquid scintillator detector for both efficient detection of reactor antineutrinos through the inverse beta decay reaction and excellent background discrimination. PROSPECT is a movable 4-ton antineutrino detector covering distances of 7m to 13m from the High Flux Isotope Reactor core. It will probe the best-fit point of the $\bar\nu_e$ disappearance experiments at 4$\sigma$ in 1 year and the favored regions of the sterile neutrino parameter space at more than 3$\sigma$ in 3 years. PROSPECT will test the origin of spectral deviations observed in recent $\theta_{13}$ experiments, search for sterile neutrinos, and address the hypothesis of sterile neutrinos as an explanation of the reactor anomaly. This paper describes the design, construction, and commissioning of PROSPECT and reports first data characterizing the performance of the PROSPECT antineutrino detector.

physics.ins-det↗

arXiv2018

First search for short-baseline neutrino oscillations at HFIR with PROSPECT

This Letter reports the first scientific results from the observation of antineutrinos emitted by fission products of $^{235}$U at the High Flux Isotope Reactor. PROSPECT, the Precision Reactor Oscillation and Spectrum Experiment, consists of a segmented 4 ton $^6$Li-doped liquid scintillator detector covering a baseline range of 7-9 m from the reactor and operating under less than 1 meter water equivalent overburden. Data collected during 33 live-days of reactor operation at a nominal power of 85 MW yields a detection of 25461 $\pm$ 283 (stat.) inverse beta decays. Observation of reactor antineutrinos can be achieved in PROSPECT at 5$\sigma$ statistical significance within two hours of on-surface reactor-on data-taking. A reactor-model independent analysis of the inverse beta decay prompt energy spectrum as a function of baseline constrains significant portions of the previously allowed sterile neutrino oscillation parameter space at 95% confidence level and disfavors the best fit of the Reactor Antineutrino Anomaly at 2.2$\sigma$ confidence level.

hep-ex↗

arXiv2008

Electric field gradient induced effects in GaAs/AlGaAs modulation-doped structures and high frequency sensing

Electric field gradient effects induced by an asymmetrically in-plane shaped GaAs/AlGaAs modulation-doped structures of various design are investigated within 4-300 K temperature range. It is demonstrated that current-voltage characteristics of such structures at low, 4-80 K, temperatures exhibit well-pronounced asymmetry arising due to a presence of two different gradients of the electric field in a two dimensional electron gas. This phenomenon is caused by both, different accumulation of two-dimensional electrons due to asymmetrical shape of the structure and nonlocality in the electron drift velocity. Experiments are illustrated by a phenomenological model and Monte Carlo simulation. Possible applications of the effect to detect electromagnetic radiation of GHz and THz frequencies are discussed as well.

cond-mat.mtrl-sci↗