arXiv subjects

John Harton

Publications and source records attributed to John Harton.

3 recordsLinked to original sources

arXiv2026

Single-Shot High-Energy Muon and Particle Radiography with a Multi-GeV Laser-Wakefield-Accelerator-Driven Source

We report the first demonstration of single-shot particle radiography using a 1-10 GeV laser-wakefield-generated beam of muons, pions, and neutrons. The test objects were imaged ~15 m from the beam source, through dense lead shielding followed by the walls of a building and a truck. The muon content of the beam was directly confirmed using large volume scintillator-based detectors, which recorded particle decay events with timing delays consistent with the muon lifetime. Simulations confirm that the high energy component of the beam transmitted through the test object is nearly entirely composed of muons, directly showing their highly penetrative nature, with a single-shot fluence equivalent to >8 hours of integration of cosmic ray muons near the horizon. Our work establishes single-shot high-energy particle radiography with a laser-wakefield-accelerator-driven source.

physics.plasm-ph↗

arXiv2015

Reducing DRIFT Backgrounds with a Submicron Aluminized-Mylar Cathode

Background events in the DRIFT-IId dark matter detector, mimicking potential WIMP signals, are predominantly caused by alpha decays on the central cathode in which the alpha particle is completely or partially absorbed by the cathode material. We installed a 0.9 micron thick aluminized-mylar cathode as a way to reduce the probability of producing these backgrounds. We study three generations of cathode (wire, thin-film, and radiologically clean thin-film) with a focus on the ratio of background events to alpha decays. Two independent methods of measuring the absolute alpha decay rate are used to ensure an accurate result, and agree to within $10\%$. Using alpha range spectroscopy, we measure the radiologically cleanest cathode version to have a contamination of $3.3\pm0.1$ ppt $^{234}$U and $73\pm2$ ppb $^{238}$U. This cathode reduces the probability of producing an RPR from an alpha decay by a factor of $70\pm20$ compared to the original stainless steel wire cathode. First results are presented from a texturized version of the cathode, intended to be even more transparent to alpha particles. These efforts, along with other background reduction measures, have resulted in a drop in the observed background rate from 500/day to 1/day. With the recent implementation of full-volume fiducialization, these remaining background events are identified, allowing for background-free operation.

physics.ins-det↗

arXiv2014

Background Assay and Rejection in DRIFT

The DRIFT-IId dark matter detector is a m$^3$-scale low-pressure TPC with directional sensitivity to WIMP-induced nuclear recoils. Its primary backgrounds were due to alpha decays from contamination on the central cathode. Efforts to reduce these backgrounds led to replacing the 20 μm wire central cathode with one constructed from 0.9 μm aluminized mylar, which is almost totally transparent to alpha particles. Detailed modeling of the nature and origin of the remaining backgrounds led to an in-situ, ppt-sensitive assay of alpha decay backgrounds from the central cathode. This led to further improvements in the thin-film cathode resulting in over 2 orders of magnitude reduction in backgrounds compared to the wire cathode. Finally, the addition of O$_2$ to CS$_2$ gas was found to produce multiple species of electronegative charge carriers, providing a method to determine the absolute position of nuclear recoils and reject all known remaining backgrounds while retaining a high efficiency for nuclear recoil detection.

physics.ins-det↗