Martin Jacob Berger

Abstract

Known as the father of electron and proton Monte Carlo methods, Martin Jacob Berger, chief of the radiation theory section of the National Bureau of Standards (now NIST) for more than 20 years, died in Bethesda, Maryland, on 6 November 2004 from the effects of a hematoma after a fall in which he struck his head.Born in Vienna in 1922, Martin left Austria in 1938 just before its annexation by Nazi Germany. After 18 months in England, he immigrated to the US in 1940 and earned a BS in physics from the University of Chicago three years later. He became a US citizen in 1944, joined the Army, and served in the Aleutian Islands until 1946. Shortly after his discharge, he began his graduate work at the University of Chicago and earned an MS (1948) and a PhD (1951), both in physics. He prepared his doctoral thesis under Marcel Schein on “Multiple Scattering of Fast Protons in Photographic Emulsions” and stayed on for a one-year postdoctoral fellow-ship in mathematical statistics.Martin had heard that Ugo Fano and Lew Spencer of NBS had been doing work on ionizing radiation, so he wrote to them, was invited for an interview, and was hired. In September 1952 he joined the radiation theory section, headed by Fano, within the atomic and radiation physics division, led by Lauriston Taylor. Twelve years later Martin became chief of the radiation theory section and was in charge of as many as 12 physicists; he held that position—through various reorganizations and a renaming—until his retirement in 1988.At NBS in the 1950s, Martin concentrated first on the transport of gamma rays and the development of photon Monte Carlo methods. He pioneered Monte Carlo calculations in complex media and extended them to realistic configurations involving boundaries and inhomogeneities. For the work on photon transport, Martin collaborated with colleagues in the radiation theory section to survey and compile cross-section information. One such colleague was Rosemary McGinnies, who wrote several important early evaluations. In 1960 Martin married Rosemary; they later had three children and six grandchildren. Over the years, Martin retained his interest in photon-interaction cross sections and collaborated on critically evaluated databases that have become a standard for radiation-transport calculations.Martin shifted his focus to charged-particle transport, with an emphasis on electrons and protons. His 1963 article “Monte Carlo Calculation of the Penetration and Diffusion of Fast Charged Particles,” which appeared in Methods in Computational Physics, thoroughly delineated the taxonomy, methods, underlying single- and multiple-scattering distributions, and algorithms used in charged-particle Monte Carlo codes. That work was a departure from the few earlier papers done by other authors mostly for calculations of showers in high-energy approximations. In his study, Martin developed a comprehensive approach in which he used the most accurate distributions available to describe the transport of radiation at energies of interest in medical and radiation-protection physics.With his 1963 paper, Martin literally established the modern Monte Carlo calculation of charged-particle transport. The methods he developed and the cross-section data for which he was largely responsible are imbedded in nearly all of today’s coupled photon–charged-particle Monte Carlo codes. The use of electron–photon Monte Carlo calculations are now widespread, and the field has matured so much that scientists in many disciplines now rely heavily on the results of the better-known Monte Carlo codes rather than much more difficult measurements. Perhaps the most telling compliment is that his early pioneering work is still remarkably relevant today, more than 40 years later.Martin was also responsible for an extensive body of critically evaluated radiation-interaction data. These data were not only necessary for his transport calculations but have become standard reference data for the radiological sciences. They include stopping powers and ranges for electrons, positrons, and heavy charged particles, and cross sections for the bremsstrahlung production by electrons and for the elastic scattering of electrons and positrons. During his Monte Carlo development work, Martin was also busily applying his methods to important problems in radiological physics. He calculated detector-response functions for radiation spectroscopy; performed microdosimetric calculations; and conducted numerous studies of the absorbed dose and the penetration of photons, electrons, bremsstrahlung, and protons in materials of interest in dosimetry, radiation protection, radiation shielding, auroral physics, and radioactivity standardization. After his retirement, he continued that work as a consultant for NBS and other agencies.Martin’s work was scientifically impeccable. He attacked each problem in his own way, which usually became the standard way. He frequently selected problems that others had not worked on and gave correct, straightforward, and useful solutions. In recognition of his enduring contributions, the International Commission on Radiation Units and Measurements awarded Martin its L. H. Gray Medal in 2003.The radiological community has lost an important scientist. Martin Jacob Berger PPT|High resolution© 2005 American Institute of Physics.