P&A Brochure - Atomic, Nuclear, Plasma

    Atomic physics has had a long history at Johns Hopkins, stretching back to Henry A. Rowland, the first professor of physics here, and to his successor, R.W. Wood.

    Professor Judd is using group theory to analyze how the energy levels of complex atoms can be treated in terms of a detailed theory of atomic structure. The basic Coulomb interaction between the electrons and the atomic nuclei is broken down into component parts, the mathematical properties of which are more easily manageable than those of the whole. A quarklike model of the f shell, applicable to rare earths, has proved to be particularly useful.

    QED calculations of corrections to the energy levels of many-electron atoms (Professor G. Feldman) are of recent and current interest because of very accurate measurements arising from new experimental techniques: beam foil spectroscopy, using heavy ion accelerators, and the employment of lasers in the study of atomic transitions. These techniques have resulted in the measurement of states of highly ionized atoms with large nuclear charge. Standard approaches, such as the Hartree-Fock approximation, have to be reconsidered, so that relativistic effects, radiative corrections and renormalization can be studied in a systematic way. Analytical work, leading to numerical computations, is being carried out in this area.

    Plasma spectroscopy represents a marriage between plasma physics and atomic physics. The spectroscopic emissions from ions provide one of the best means for plasma diagnosis.

The National Spherical Torus Experiment (NSTX) at PPPL

Plasma spectroscopy has applications in a number of areas, ranging from the study of planetary magnetospheres to controlled nuclear fusion as a source of energy. The Hopkins plasma spectroscopy program (Professor Warren Moos and Visiting Professor Michael Finkenthal) has grown out of astrophysics research. Students and research staff use ultraviolet and soft X-ray spectroscopic instrumentation to study magnetically confined very high temperature plasmas of the type playing a role in controlled thermonuclear research at various U.S. and European laboratories. Conventional spectroscopy is not sufficient to study these plasmas. New kinds of detectors, spectrographs and computer-controlled electronics are necessary. Both the plasma properties and the atomic physics of the highly ionized species that appear at high plasma temperatures are studied in the research. They have led to the recognition of the importance that radiative losses, impurity concentrations and transport processes play in plasmas near the edge of Tokamaks.

Physical phenomena of dense nuclear matter form the central focus of the Hopkins nuclear physics program.

The Relativistic Heavy Ion Collider (RHIC) accelerator at Brookhaven National Laboratory, which achieved its design energy of 100 GeV in 2001, provides a unique environment for the search of such new quantum state. Professor Yung Lee is involved in the BRAHMS experiment at RHIC. Collisions of heavy ion beams at RHIC will create temperature and density conditions that are comparable to those at the time of the origin of the universe. The BRAHMS detector is designed to gather basic information in heavy ion reactions on momentum spectra and yields for various emitted particles with a sensitivity to detect new phenomena under such conditions.

Faculty: G. Feldman (emeritus), Finkenthal, Judd (emeritus), Lee, Moos.