arXiv subjects

Kai Vetter

Publications and source records attributed to Kai Vetter.

10 recordsLinked to original sources

arXiv2023

In-situ quantification of gamma-ray and beta-only emitting radionuclides

The prompt and in-situ assessment of non-gamma ray emitting radionuclides such as Sr-90 remains an outstanding challenge, particularly in radiological emergency response and consequence management situations. We have developed a new concept to quantitatively assess a wide range of radionuclides, including beta-only emitters, using coplanar-grid CdZnTe detectors that provide depth-of-interaction sensing. By combining measurements with and without an electron absorber, we demonstrate the feasibility of detecting and identifying Sr-90 and other radionuclides with a sensitivity of about 1 $μ$Ci/m$^2$ or 3.7x10$^4$ Bq/m$^2$, which is 10\% of the Derived Response Level, in less than 60 minutes. The new compact instrument can be used in the field or mobile laboratories to quickly assess a wide range of samples with sufficient sensitivity and specificity to provide critical guidance in the response after radiological incidents.

physics.ins-det↗

arXiv2023

Coded Aperture and Compton Imaging for the Development of $^{225}$Ac-based Radiopharmaceuticals

Targeted alpha-particle therapy (TAT) has great promise as a cancer treatment. Arguably the most promising TAT radionuclide that has been proposed is $^{225}$Ac. The development of $^{225}$Ac-based radiopharmaceuticals has been hampered due to the lack of effective means to study the daughter redistribution of these agents in small animals at the preclinical stage. The ability to directly image the daughters, namely $^{221}$Fr and $^{213}$Bi, via their gamma-ray emissions would be a boon for preclinical studies. That said, conventional medical imaging modalities, including single photon emission computed tomography (SPECT) based on pinhole collimation, cannot be employed due to sensitivity limitations. As an alternative, we propose the use of both coded aperture and Compton imaging with the former modality suited to the 218-keV gamma-ray emission of $^{221}$Fr and the latter suited to the 440-keV gamma-ray emission of $^{213}$Bi. This work includes coded aperture images of $^{221}$Fr and Compton images of $^{213}$Bi in tumor-bearing mice injected with $^{225}$Ac-based radiopharmaceuticals. These results are the first demonstration of visualizing and quantifying the $^{225}$Ac daughters in small animals via coded aperture and Compton imaging and serve as a stepping stone for future radiopharmaceutical studies.

physics.med-ph↗

arXiv2021

Free-moving Quantitative Gamma-ray Imaging

The ability to map and estimate the activity of radiological source distributions in unknown three-dimensional environments has applications in the prevention and response to radiological accidents or threats as well as the enforcement and verification of international nuclear non-proliferation agreements. Such a capability requires well-characterized detector response functions, accurate time-dependent detector position and orientation data, a digitized representation of the surrounding 3D environment, and appropriate image reconstruction and uncertainty quantification methods. We have previously demonstrated 3D mapping of gamma-ray emitters with free-moving detector systems on a relative intensity scale using a technique called Scene Data Fusion (SDF). Here we characterize the detector response of a multi-element gamma-ray imaging system using experimentally benchmarked Monte Carlo simulations and perform 3D mapping on an absolute intensity scale. We present experimental reconstruction results from hand-carried and airborne measurements with point-like and distributed sources in known configurations, demonstrating quantitative SDF in complex 3D environments.

physics.ins-det↗

arXiv2021

Using Gamma-Ray Imaging to Measure Nuclear Lifetimes in the GRETINA Detector

GRETA, the Gamma-Ray Energy Tracking Array, is an array of highly-segmented HPGe detectors designed to track gamma-rays emitted in beam-physics experiments. Its high detection efficiency and state-of-the-art position resolution make it well-suited for imaging applications. In this paper, we use simulated imaging data to illustrate how imaging can be applied to nuclear lifetime measurments. This approach can offer multiple benefits over traditional lifetime techniques such as RDM.

physics.ins-det↗

arXiv2021

Simulations of Compton Sequencing with the GRETINA Detector

GRETA, the Gamma-Ray Energy Tracking Array, is an array of highly-segmented HPGe detectors designed to track gamma-rays emitted in beam-physics experiments. Its high detection efficiency and state-of-the-art position resolution enable it to reject Compton background and also sequence detected interactions via Compton kinematics. In this paper, we use simulated photon tracks to estimate how well interactions can be sequenced in the GRETA detector. This lays the groundwork for subsequent gamma-ray imaging applications such as nuclear lifetime measurements.

physics.ins-det↗

arXiv2021

Using Compton Imaging to Locate Moving Gamma-Ray Sources in the GRETINA Detector

GRETA, the Gamma-Ray Energy Tracking Array, is an array of highly-segmented HPGe detectors designed to track γ-rays emitted in beam-physics experiments. Its high detection efficiency and state-of-the-art position resolution make it well-suited for Compton imaging applications. In this paper, we use simulated imaging data to illustrate how GRETA can be used to locate the emission points of photons produced during beam experiments. This lays the groundwork for nuclear lifetime measurements using Compton imaging.

physics.ins-det↗

arXiv2018

3-D Radiation Mapping in Real-Time with the Localization and Mapping Platform LAMP from Unmanned Aerial Systems and Man-Portable Configurations

Real-time, meter-resolution gamma-ray mapping is relevant in the detection and mapping of radiological materials, and for applications ranging from nuclear decommissioning, waste management, and environmental remediation to homeland security, emergency response, and international safeguards. We present the Localization and Mapping Platform (LAMP) as a modular, contextual and radiation detector sensor suite, which performs gamma-ray mapping in three dimensions (3-D) and in real time, onboard an unmanned aerial vehicle (UAV) or in a man-portable configuration. The deployment of an unmanned aerial system (UAS) for gamma-ray mapping can be advantageous, as the UAS provides a means of measuring large areas efficiently and improving accessibility to some environments, such as multi-story structures. In addition, it is possible to increase measurement robustness through autonomous navigation, and to reduce radiation exposure to users as a result of the remote measurement. LAMP enables meter-resolution gamma-ray mapping through Scene Data Fusion (SDF) [1], a capability that fuses radiation and scene data via voxelized 3-D Maximum Likelihood Expectation Maximization (MLEM) to produce 3-D maps of radioactive source distributions in real-time. Results are computed onboard LAMP while it is flying on the UAV and streamed from the system to the user, who can view the 3-D map on a tablet in real-time. We present results that demonstrate the SDF concept, including a set of UAS flights where a 133Ba source is localized at a test site in Berkeley, CA and a handheld measurement in Fukushima Prefecture, Japan where the distribution of radiocesium(137,134Cs) released from the accident of the Fukushima Daiichi Nuclear Power Plant is mapped. The reconstruction parameters used for each measurement were identical, indicating that the same algorithm can be used for both point or distributed sources.

physics.app-ph↗

arXiv2016

Fast neutron background characterization with the Radiological Multi-sensor Analysis Platform (RadMAP)

In an effort to characterize the fast neutron radiation background, 16 EJ-309 liquid scintillator cells were installed in the Radiological Multi-sensor Analysis Platform (RadMAP) to collect data in the San Francisco Bay Area. Each fast neutron event was associated with specific weather metrics (pressure, temperature, absolute humidity) and GPS coordinates. The expected exponential dependence of the fast neutron count rate on atmospheric pressure was demonstrated and event rates were subsequently adjusted given the measured pressure at the time of detection. Pressure adjusted data was also used to investigate the influence of other environmental conditions on the neutron background rate. Using National Oceanic and Atmospheric Administration (NOAA) coastal area lidar data, an algorithm was implemented to approximate sky-view factors (the total fraction of visible sky) for points along RadMAPs route. Three areas analyzed in San Francisco, Downtown Oakland, and Berkeley all demonstrated a suppression in the background rate of over 50% for the range of sky-view factors measured. This effect, which is due to the shielding of cosmic-ray produced neutrons by surrounding buildings, was comparable to the pressure influence which yielded a 32% suppression in the count rate over the range of pressures measured.

physics.ins-det↗

arXiv2015

Ultra-Low Noise Mechanically Cooled Germanium Detector

Low capacitance, large volume, high purity germanium (HPGe) radiation detectors have been successfully employed in low-background physics experiments. However, some physical processes may not be detectable with existing detectors whose energy thresholds are limited by electronic noise. In this paper, methods are presented which can lower the electronic noise of these detectors. Through ultra-low vibration mechanical cooling and wire bonding of a CMOS charge sensitive preamplifier to a sub-pF p-type point contact HPGe detector, we demonstrate electronic noise levels below 40 eV-FWHM.

physics.ins-det↗

arXiv2015

Status Update of the MAJORANA DEMONSTRATOR Neutrinoless Double Beta Decay Experiment

Neutrinoless double beta decay searches play a major role in determining neutrino properties, in particular the Majorana or Dirac nature of the neutrino and the absolute scale of the neutrino mass. The consequences of these searches go beyond neutrino physics, with implications for Grand Unification and leptogenesis. The \textsc{Majorana} Collaboration is assembling a low-background array of high purity Germanium (HPGe) detectors to search for neutrinoless double-beta decay in $^{76}$Ge. The \textsc{Majorana Demonstrator}, which is currently being constructed and commissioned at the Sanford Underground Research Facility in Lead, South Dakota, will contain 44 kg (30 kg enriched in $^{76}$Ge) of HPGe detectors. Its primary goal is to demonstrate the scalability and background required for a tonne-scale Ge experiment. This is accomplished via a modular design and projected background of less than 3 cnts/tonne-yr in the region of interest. The experiment is currently taking data with the first of its enriched detectors.

physics.ins-det↗