Monitoring of the atmosphere for fission products (131mXe, 133mXe, 133Xe, and 135Xe) is performed by various laboratories to detect nuclear explosions. Quantification of 127Xe is not routinely performed by laboratories measuring atmospheric radioxenon because it is not a fission product. 127Xe was recently detected by a ground-based beta-gamma air monitoring system. When measured using beta-gamma coincidence detector systems, such as those in use on the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), 127Xe can interfere with the quantification of fission product radioxenon due to overlap of the 127Xe beta-gamma coincidence signatures with those of fission product radioxenon. This work demonstrates quantification of 127Xe at different laboratories with different measurement techniques. Production and purification of 127Xe was performed by neutron activation of enriched 126Xe. The purified 127Xe was then split between laboratories, and detection and quantification methods were developed. At Idaho National Laboratory, a quantification method involving high purity germanium detectors was devised that included self-attenuation correction. At AWE, a beta-gamma coincidence counting method, as used in support of the IMS, was modified to enable the measurement and analysis of the 127Xe samples. Corrections were made for self-attenuation, which showed a strong xenon volume dependency, for some coincidence signatures. The gas sample activity concentration was used as the comparison metric and it showed excellent agreement between the methods.

The International Monitoring System includes a network of radionuclide detector stations and laboratories operated around the world monitoring for nuclear explosions. The United States Radionuclide Laboratory for radioxenon detection (USL16-NGL) was certified by the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization in 2016. Since the certification of the laboratory, an additional set of four radioxenon detectors have been added to the laboratory. These supplementary radioxenon detectors allow for improved throughput for the laboratory and improving the ability to measure short lived radioxenon isotopes. In this paper, we describe the implementation of the additional radioxenon detectors and how they compare to current capabilities. Additionally, we detail implementation procedures to leverage the increased throughput.

Station RN33 on Mount Schauinsland near Freiburg, Germany, is part of the International Monitoring System monitoring radioxenon in air (131mXe, 133Xe, 133mXe, and 135Xe) for verification of the Comprehensive Nuclear Test Ban Treaty. Here, we present data from phase II testing of a new system, Xenon International at RN33, July 14th, 2021 to Jan 22nd, 2022, together with SPALAX data from the same time period. Radioxenon could be detected in 473 of 719 samples, among them many multiple isotope detections. Activity concentrations of spiked and selected environmental samples were verified by laboratory reanalysis. The sensitivity of Xenon International for radioxenons is up to one order of magnitude better for the metastable isotopes than that of the SPALAX, with a shorter sampling duration of 6 h.

The International Monitoring System includes a network of radionuclide detectors operated around the world monitoring for nuclear explosions. A key aspect of the International Monitoring System is the detection of radioxenon with a network of stations and laboratories. Beta-gamma detectors are utilized extensively for the detection of radioxenon, and the beta detection is primarily performed with a plastic scintillator cell. Two areas of improvement for plastic scintillator are the sample carry-over (“memory effect”) and energy resolution. While the scintillator can be coated to remove the memory effect, the energy resolution must be improved with a different detector material. Silicon is the current leading candidate for the future beta cell material due to the much-improved energy resolution compared to plastic scintillators (factor of ~ 3x). PNNL is developing a silicon beta cell for use as a potential modular replacement within Xenon International (a next generation radioxenon detection system currently undergoing acceptance testing for potential inclusion in the International Monitoring System). The beta cell utilizes four different silicon detectors to create an active volume for the radioxenon within an outer gas cell. Since there are four separate beta signals (compared to one for plastic scintillators), data acquisition modifications are required. In this paper, we detail the design, efficiency measurements, and long-term testing of the silicon beta cell and potential improvements in isotopic discrimination.

Three unusual radioactive isotopes of xenon-Xe-125, Xe-127, and (129)mXe-have been observed during testing of a new generation radioxenon measurement system at the manufacturing facility in Knoxville, Tennessee. These are possibly the first detections of these isotopes in environmental samples collected by automated radioxenon systems. Unfortunately, the new isotopes detected by the Xenon International sampler can interfere with quantification of the radioactive xenon isotopes used to monitor for nuclear explosions.Xenon International sampling data collected during February through September 2020 were combined with an atmospheric transport model to identify the possible release location. A source-location analyses using sample counts dominated by Xe-125 strongly supports the conclusion that the release point is near (within 20 km) the sampler location. Wind patterns are not consistent with releases coming from more distant nuclear power plants. The High Flux Isotope Reactor (HFIR) and the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory are located in the region of most likely source locations.The source-location analysis cannot rule out either facility as a release location, and some of the samples may contain a combination of releases from both facilities. The source-location results using Xe-125 are not unexpected because Klingberg et al. (2013) previously published the production rate of radioactive xenon isotopes from neutron activation of stable xenon in the air at the HFIR. Up to 10(12) Bq of Xe-125 could be produced per operational day and other xenon isotopes would be produced in lesser quantities.

We present an overview of a small-scale tracer migration experiment that was carried out in July 2018 at the Nevada National Security Site. This experiment involved the injection of 133Xe into the bottom of a shallow borehole with multiple sampling intervals. Sampling was then conducted in the injection borehole and in a second borehole located 17 m from the injection site. A simple system for measurement of the 133Xe activity in whole air was utilized onsite. Though many samples were well below MDC, cross-hole tracer transport was observed. Along with experimental results, additional insights gained from numerical modeling are presented.

Beam-recoil transferred polarizations for the exclusive electroproduction of $K^+\Lambda$ and $K^+\Sigma^0$ final states from an unpolarized proton target have been measured using the CLAS12 spectrometer at Jefferson Laboratory. The measurements at beam energies of 6.535~GeV and 7.546~GeV span the range of four-momentum transfer $Q^2$ from 0.3 to 4.5~GeV$^2$ and invariant energy $W$ from 1.6 to 2.4~GeV, while covering the full center-of-mass angular range of the $K^+$. These new data extend the existing hyperon polarization data from CLAS in a similar kinematic range but from a significantly larger dataset. They represent an important addition to the world data, allowing for better exploration of the reaction mechanism in strangeness production processes, for further understanding of the spectrum and structure of excited nucleon states, and for improved insight into the strong interaction in the regime of non-perturbative dynamics.

Radon interferes with concentration measurements used by atmospheric radioxenon systems. We demonstrate a method to quantify the amount of radon that is present in the detectors, the impact of radon activity on the minimum-detectable-concentrations, and how to determine the needed radon rejection levels. An example calculation shows a radon rejection level of 105 is sufficient to limit impact on the detector sensitivity. We anticipate this method will give analysist a better understanding of radon present in their measurements and allow system designers to tailor their systems’ radon rejection better for its location.

We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off ^4He using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized ^4He gaseous target. We detail the method used to ensure the exclusivity of the measured reactions, in particular the upgrade of CLAS with a radial time projection chamber to detect the low-energy recoiling ^4He nuclei and an inner calorimeter to extend the photon detection acceptance at forward angles. Our results confirm the theoretically predicted enhancement of the coherent (e^4He→ e'^4He'γ') beam spin asymmetries compared to those observed on the free proton, while the incoherent (e^4He→ e'p'γ'X') asymmetries exhibit a 30% suppression. From the coherent data, we were able to extract, in a model-independent way, the real and imaginary parts of the only ^4He Compton form factor, H_A, leading the way toward 3D imaging of the partonic structure of nuclei.

We report on the measurement of the beam spin asymmetry in the deeply virtual Compton scattering off He-4 using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab using a 6 GeV longitudinally polarized electron beam incident on a pressurized He-4 gaseous target. We detail the method used to ensure the exclusivity of the measured reactions, in particular the upgrade of CLAS with a radial time projection chamber to detect the low-energy recoiling He-4 nuclei and an inner calorimeter to extend the photon detection acceptance at forward angles. Our results confirm the theoretically predicted enhancement of the coherent (e(4)He -> e'4He'gamma') beam spin asymmetries compared to those observed on the free proton, while the incoherent (e(4)He -> e'p'gamma'X') asymmetries exhibit a 30% suppression. From the coherent data, we were able to extract, in a model-independent way, the real and imaginary parts of the only He-4 Compton form factor, H-A, leading the way toward 3D imaging of the partonic structure of nuclei.

Measurement of radioactive gas seepage from an underground nuclear explosion is one of the primary methods to confirm whether an event was nuclear in nature. Radioactive noble gas indicators that are commonly targeted by such measurements (e.g. 133Xe, 37Ar) have half-lives of 35 days or less. Argon-39, an activation product similar to 37Ar, is produced by the interaction between neutrons and potassium in the surrounding geology and has a half-life of 269 years. Measurements taken at three sites near three historic underground nuclear test locations at the Nevada National Security Site have all shown highly elevated levels of 39Ar in soil gas decades after the test events. Elevated levels of 39Ar were also detected in atmospheric air collected near two of these sites, and outside the entrance of the one tunnel site. These measurements demonstrate that 39Ar has the potential to be a long-term signature of an underground nuclear event which can be reliably detected at the surface or in the shallow subsurface. This radionuclide detection of an underground nuclear event decades after the event takes place is in contrast to the commonly held assumption that detecting underground nuclear events via radionuclides at the surface needs to be done in a matter of months. Depending upon what further studies show about the robustness of this signature in a variety of geological settings, it may in fact be easy to detect underground nuclear events at the surface for a very long time post-detonation.

Der Workshop beschreibt das entwickelte Gesamtkonzept des Moduls „Fit fur Studium und Beruf“ (B.Sc. Ingenieurstudium, Studieneingangsphase, 3 LP). Es werden ausgewahlte Instrumente vorgestellt, die zur Unterstutzung von individueller Kompetenzentwicklung (z.B. Reflexionskompetenz), zur Sozialisierung im Studiengang und zur fruhen Berufsfeldorientierung der Studienanfanger*innen (z.B. Berufsbildvortrage, Berufskompetenz-Steckbriefe) angeboten werden. Erganzend werden die Studierenden in unterschiedlichen Feedbacksettings aktiv an der Ausgestaltung des Moduls beteiligt. Das Modul ist daruber hinaus hinsichtlich schriftlichem und mundlichem Prasentationstraining eng mit Praxistraining in Pflichtveranstaltungen verzahnt, wodurch forschungsorientierte Lehre in hoheren Semestern vorbereitet wird.

We report a measurement of a beam–target double-polarisation observable (E) for the γ→n→(p)→K+Σ−(p) reaction. The data were obtained impinging the circularly-polarised energy-tagged photon beam of Hall B at Jefferson Lab on a longitudinally-polarised frozen-spin hydrogen deuteride (HD) nuclear target. The E observable for an effective neutron target was determined for centre-of-mass energies 1.70≤W≤2.30 GeV, with reaction products detected over a wide angular acceptance by the CLAS spectrometer. These new double-polarisation data give unique constraints on the strange decays of excited neutron states. Inclusion of the new data within the Bonn-Gatchina theoretical model results in significant changes for the extracted photocouplings of a number of established nucleon resonances. Possible improvements in the PWA description of the experimental data with additional "missing" resonance states, including the N(2120)3/2− resonance, are also quantified.