arXiv subjects

Christopher Kenney

Publications and source records attributed to Christopher Kenney.

4 recordsLinked to original sources

arXiv2026

Active Edge Silicon Sensors Fabricated With Edge Ion Implantation and Microwave Annealing for Dopant Activation

Silicon detectors typically require an insensitive area around their periphery to accommodate guard rings, which help maintain the electric field uniformity around edge pixels and isolate the high leakage current from the physical edges of the detector. Minimization of this insensitive region is desirable for applications in high-energy physics, X-ray experiments, and medical imaging. Existing active edge technology offers a solution for reduction or total elimination of the insensitive region, via a continuation of the highly doped backside up the sidewalls of the device. However, current methods for realizing this technology are complex and expensive. We propose a new technique that simplifies the fabrication of highly doped edges using side ion implantation and microwave annealing. Tests demonstrating the feasibility of this proposed process were performed on a set of sensors, and current versus bias voltage measurements probing the edge effects were performed before and after the edge implantation and annealing. To aid in interpretation of the results, TCAD simulations of the test devices were performed. Significant improvement in the edge leakage current is observed, indicating the promise of this simplified process for fabrication of active edge sensors.

physics.ins-det↗

arXiv2025

Characterization of a TES-based Anti-Coincidence Detector for Future Large Field-of-View X-ray Calorimetry Missions

Microcalorimeter instruments aboard future X-ray observatories will require an anti-coincidence (anti-co) detector to veto charged particle events and reduce the non-X-ray background. We have developed a large-format, TES-based prototype anti-coincidence detector that is particularly suitable for use with spatially-extended (~ 10 cm^2}) TES microcalorimeter arrays, as would be used for a future large field-of-view X-ray missions. This prototype was developed in the context of the Line Emission Mapper (LEM) probe concept, which required a ~ 14 cm^2 anti-co detector with > 95% live time and a low-energy threshold below 20 keV. Our anti-co design employs parallel networks of quasiparticle-trap-assisted electrothermal feedback TESs (QETs) to detect the athermal phonon signal produced in the detector substrate by incident charged particles. We developed multiple prototype anti-co designs featuring 12 channels and up to 6300 QETs. Here we focus on a design utilizing tungsten TESs and present characterization results. Broad energy range measurements have been performed (4.1 keV -- 5.5 MeV). Based on noise and responsivity measurements, the implied low-energy threshold is < 1 keV and a live time fraction of > 96% can be achieved up to 5.5 MeV. We also find evidence of mm-scale-or-better spatial resolution and discuss the potential utility of this for future missions. Finally, we discuss the early development of a soild-state physics model of the anti-co towards understanding phonon propagation and quasiparticle production in the detector.

astro-ph.IM↗

arXiv2022

Measuring the electron neutrino mass using the electron capture decay of 163Ho

While the mass differences between neutrino mass states are known, their absolute masses and mass hierarchy have not yet been determined. Determining the mass of neutrinos provides access to physics beyond the Standard Model and the resulting value has implications for the growth of large-scale structure in the universe over cosmic history. Because of the importance of the topic, a number of efforts are already underway to determine the mass of neutrinos including direct kinematic measurements and indirect measurements of astrophysical phenomena that constrain the sum of the mass eigenstates through models of cosmic evolution. Here, we advocate for a collaborative international effort to perform a kinematic determination of the effective electron neutrino mass using calorimetric measurements of the decay of 163Ho. This effort is justified by the success of current experiments using the technique, its high benefit-to-cost ratio, the value of approaches with different systematic errors, and the value of measuring the electron neutrino mass rather than the electron anti-neutrino mass.

nucl-ex↗

arXiv2015

Nonlinear X-ray Compton Scattering

X-ray scattering is a weak linear probe of matter. It is primarily sensitive to the position of electrons and their momentum distribution. Elastic X-ray scattering forms the basis of atomic structural determination while inelastic Compton scattering is often used as a spectroscopic probe of both single-particle excitations and collective modes. X-ray free-electron lasers (XFELs) are unique tools for studying matter on its natural time and length scales due to their bright and coherent ultrashort pulses. However, in the focus of an XFEL the assumption of a weak linear probe breaks down, and nonlinear light-matter interactions can become ubiquitous. The field can be sufficiently high that even non-resonant multiphoton interactions at hard X-rays wavelengths become relevant. Here we report the observation of one of the most fundamental nonlinear X-ray-matter interactions, the simultaneous Compton scattering of two identical photons producing a single photon at nearly twice the photon energy. We measure scattered photons with an energy near 18 keV generated from solid beryllium irradiated by 8.8-9.75 keV XFEL pulses. The intensity in the X-ray focus reaches up to 4x20 W/cm2, which corresponds to a peak electric field two orders of magnitude higher than the atomic unit of field-strength and within four orders of magnitude of the quantum electrodynamic critical field. The observed signal scales quadratically in intensity and is emitted into a non-dipolar pattern, consistent with the simultaneous two-photon scattering from free electrons. However, the energy of the generated photons shows an anomalously large redshift only present at high intensities. This indicates that the instantaneous high-intensity scattering effectively interacts with a different electron momentum distribution than linear Compton scattering, with implications for the study of atomic-scale structure and dynamics of matter

physics.optics↗