Louisiana State University Physics & Astronomy

Michael L. Cherry
Professor of Physics

Ph.D., 1978 - University of Chicago

Astronomy - Particle Astrophysics

Office: 343-B Nicholson
Telephone: 8591-Office
E-mail:

Space Science/Particle Astrophysics

RESEARCH INTERESTS

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. 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. The LSU Space Science/Particle Astrophysics group has a long-standing program of research in high energy astrophysics. I am currently involved in two separate experiments: the ACCESS experiment to study the composition, spectra, and interactions of cosmic ray protons and nuclei at energies up to the "knee" in the cosmic ray spectrum at 10¹⁵ eV; and the CASTER experiment to perform high angular resolution studies of cosmic x-rays and gamma rays in the energy range 20-600 keV.

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. ACCESS, a cosmic ray detector to be flown on the Space Station, is being designed to address these issues. ACCESS will consist of a calorimeter and a transition radiation detector specifically designed to address the issue of the origin of the cosmic rays near the "knee". We are working on the design of the transition radiation detector designed to observe nuclei as heavy as iron up to energies of 10¹⁴ eV/nucleon.

CASTER is a mission being studied for the Blank Hole Finder Probe satellite mission, a part 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, and able to perform pixellated scintillator viewed by position-sensitive photomultiplier tubes. CASTER's predecessor, MARGIE, was been selected as a mission concept proposal for NASA's Ultra-Long Duration (100 day) Balloon program. We are presently involved in the detector development and instrument design for both the balloon and satellite versions of the telescope.

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).

Updated: Thu, 11-Oct-2007 3:04 PM