Overview
Professor Howell’s research is in the area of experimental nuclear physics with emphasis on the quantum chromodynamics (QCD) description of low-energy nuclear phenomena, including structure properties of nucleons and nuclei and reaction dynamics in few-nucleon systems. The macroscopic properties of nucleon structure and the residual strong nuclear force between neutrons and protons in nuclei emerge from QCD at distances where the color interactions between quarks and gluons are strong. However, the details of the mechanisms that generate the strong nuclear force are not well understood. Effective field theories (EFT) and Lattice QCD calculations provide theoretical frames that connect low-energy nuclear phenomena to QCD. Professor Howell and collaborators are conducting experiments on few-nucleon systems that test predictions of ab-initio theory calculations for the purpose of providing insight about the QCD descriptions of low-energy nucleon interactions and structure. His current projects include measurements of the electromagnetic and spin-dependent structure properties of nucleons via Compton scattering on the proton and few-nucleon systems and studies of two- and three-nucleon interactions using few-nucleon reactions induced by photons and neutrons. In the coming years, a focus will be on investigating the neutron-neutron interaction in reactions and inside nuclei. In addition, his work includes applications of nuclear physics to national nuclear security, medical isotope production, and plant biology. Most of his research is carried out at the High Intensity Gamma-ray Source and the tandem laboratory at TUNL.
Current Appointments & Affiliations
Recent Publications
Photonuclear cross sections for Au 197: An update on the gold standard
Journal Article Physical Review C · December 1, 2024 Cross sections for the Au197(γ,n) reaction are broadly used in nuclear physics as a standard for normalizing photonuclear reaction cross-section data at photon beam energies above approximately 8 MeV. In this paper, we report cross-section measurements for ... Full text CiteUse of the HIFROST Dilution Refrigerator for the T20 Experiment
Conference
Proceedings of Science
·
July 30, 2024
I discussed the importance of the T20 quantity, a tensor analyzing power, and the basic experimental setup for a measurement of ↔ d (γ→, n)p, the deuteron photodisintegration. Multiple measurements have suggested the existence of a channel around 9 MeV abo ...
Cite
Characterization of 235U, 238U and 239Pu fission ionization chamber foils by α and γ-ray spectrometry
Journal Article Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment · June 1, 2024 The masses of thin, electroplated deposits of 235U, 238U and 239Pu on titanium backings have been determined to better than 1.3% precision by employing three complementary measurement techniques: α spectrometry, 2π gas counting, and γ-ray spectrometry. A d ... Full text CiteRecent Grants
Alfred P. Sloan Foundation Graduate School Award
Inst. Training Prgm or CMECo-Principal Investigator · Awarded by Alfred P. Sloan Foundation · 2017 - 2027Studies of Nuclear Structure Using Neutrons and Charged Particles
ResearchCo Investigator · Awarded by Department of Energy · 1997 - 2027REU Site: Undergraduate Research in Nuclear Particle Physics at TUNL and Duke
ResearchSenior Investigator · Awarded by National Science Foundation · 2022 - 2027View All Grants