W. Fong^*, J. L. Matthews, M. L. Dowell^†, E. R. Kinney^‡, T. Soos^§, M. Y. Wang^∥, and S. A. Wood^¶

• Department of Physics and Laboratory for Nuclear Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

P. A. M. Gram^**

• Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA

G. A. Rebka Jr. and D. A. Roberts^††

• Department of Physics, University of Wyoming, Laramie, Wyoming 82071, USA

• ^*Varian Medical Systems, Palo Alto, CA 94304 USA.
• ^†Optoelectronics Division, National Institute of Standards and Technology, Boulder, CO 80305.
• ^‡Department of Physics, University of Colorado, Boulder, CO 80309.
• ^§1255 Marina Point, Casselberry, Florida 32707, USA.
• ^∥The RAND Corporation, Santa Monica, CA 90406, USA.
• ^¶Thomas Jefferson National Accelerator Facility, Newport News, VA 23606, USA.
• ^**82-1021 Kaimalu Place, Captain Cook, HI 96704, USA.
• ^††Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor, MI 48109, USA.