Michael L. Cherry, Ph.D.

Michael L. Cherry, PhD
Professor of Physics

Ph.D., 1978 - University of Chicago

Louisiana State University
Department of Physics & Astronomy
202 Nicholson Hall, Tower Dr.
Baton Rouge, LA 70803-4001
(225) 578-2262-Office

Research Interests

Space Science/High Energy Astrophysics

High energy astrophysics deals with the radiation produced by energetic particles in space, their astrophysical sources, and the acceleration mechanisms that produce the very high energy particles. We observe cosmic ray electrons, protons, and nuclei at earth with energies orders of magnitude higher than the proton rest mass. These cosmic ray particles are a direct sample of matter from beyond the solar system, and give us information about both their sources and their propagation through the galaxy. Current models of cosmic ray acceleration suggest that the high energy cosmic ray particles are accelerated by the expanding shock waves from supernova remnants in the Galaxy. If this is true, then the shock wave accelerators should lose efficiency near 10¹⁴ eV, and measurements should show a drop-off in intensity. Our previous JACEE results show no evidence for the expected drop-off. It should also be possible to detect the TeV gamma rays from supernova remnants that are accelerating cosmic rays. However, when ground-based gamma ray detectors look at sources which are observed to produce x-rays as the expanding shock waves plow into the surrounding interstellar medium, they do not see the predicted gamma ray signal. In order to study the crucial energy range near the “knee” in the cosmic ray spectrum (the region around 10¹⁵ eV), we have developed transition radiation detectors designed to observe nuclei as heavy as iron up to energies of 10¹⁴ eV/nucleon with the proposed ACCESS detector and are currently developing the designs for a balloon instrument (ECAL) and a space detector (CALET) to measure the spectrum of high energy electrons.

Since charged cosmic ray particles are randomized in direction by the galaxy's magnetic field, however, they do not come in straight lines from their sources. If we want to observe the sources directly, we need to detect electromagnetic photons or neutrinos in high-resolution imaging telescopes. CASTER is a mission being studied for the Black Hole Finder Probe satellite mission, a component of NASA's Beyond Einstein program. CASTER will be a coded aperture telescope capable of detecting steady and transient hard x-ray and gamma ray sources with 2-6' angular resolution. The central detector is based on lanthanum bromide, a newly developed inorganic scintillator with significantly higher light yield and correspondingly better energy resolution than any other scintillator materials. We are developing lanthanum bromide detectors both for CASTER and for a long range imager suitable for national security applications – i.e. suitable for detecting weak fluxes of shielded contraband radioactive material.

Current and Selected Publications

• M.L. Cherry, "Approaching the Knee - Balloon-Borne Observations of Cosmic Ray Composition", J. Phys. Conf. Ser. 47, 31 (2006); astro-ph/0512329.

• G.L. Case, M.L. Cherry, and J.G. Stacy, "Waveshifting Fiber Readout of Lanthanum Halide Scintillators", Nuclear Instrum. and Meth. in Phys. Res. A 563, 355 (2006).

• M.L. McConnell et al., "CASTER: Concept for a Black Hole Finder Probe Based on the Use of New Scintillator Technologies", Proc. SPIE Conf. 5898, paper 5898-01 (2006).

• G.L. Case et al., "Observations of Gamma-Ray Outbursts from Galactic Microquasars", Chinese J. of Astronomy and Astrophys. 5, Suppl., 341 (2005); astro-ph/0409306.

• G.L. Case et al., "Measurements of Compton Scattered Transition Radiation at High Lorentz Factors", Nuclear Instrum. and Meth. in Phys. Res. A 524, 257 (2004).

• M.L. Cherry and G.L. Case, "Scintillator-Based Transition Radiation Detectors for Very High Energy Particles", Nuclear Instrum. and Meth. in Phys. Res. A 522, 73 (2004).

• S.P. Swordy et al., "The Composition of Cosmic Rays at the Knee", Astroparticle Phys. 18, 129 (2002).

• P. Deines-Jones et al., "Charged Particle Production in the Pb+Pb System at 158 GeV/c per Nucleon", Phys. Rev. C 62, 014903 (2000).

• J.N. Abdurashitov et al., "Measurement of the Solar Neutrino Capture Rate by SAGE and Implications for Neutrino Oscillations in Vacuum", Phys. Rev. Lett. 83, 4686 (1999).

• K. Asakimori et al., "Cosmic Ray Proton and Helium Spectra - Results from the JACEE Experiment", Astrophysical J. 502, 278 (1998).