Anthony Michael Hillas

Alexander Michael Hillas (June 1932 – 26 November 2017) was an English cosmic ray physicist. He is known for the Gaisser–Hillas function, the Hillas parameters, and MOCCA, a Monte Carlo computer code used for simulation of extensive air showers (EASs) in the energy range from 1012 (tera-) eV to 1021 (zetta-) eV.

Early life and education Born in a village near Leeds, A. Michael Hillas attended school in York. In secondary school, he showed remarkable signs of talent for computation. At the University of Leeds, he graduated with a B.Sc. in physics in 1955 with First Class Honours (Cranshaw was nominated for a Nobel Prize in 1966 by Yukihisa "Yuki" Nogami, a former doctoral student of Hideki Yukawa. ) Hillas worked at Harwell on an experiment to study air showers from cosmic rays. The experiment used an array of approximately 90 Geiger counters deployed over an area of .6 km2 (about 148 acres). and persuaded Hillas to work on the interpretation of data from the project. At the University of Leeds, Hillas was promoted in 1969 from lectureship to readership and in 1990 to a professorial chair in physics. In retirement, he remained in the department of physics and astronomy as a research professor working on TeV (tera-electronvolt) gamma-ray astronomy. He did outstanding research in numerical modelling for cosmic ray physics. His Monte Carlo computer program, MOCCA, for high-energy air shower studies, was used extensively in the design of the Pierre Auger Observatory. MOCCA was written in Pascal and was widely used by the Auger Collaboration (despite their unfamiliarity of the computer language Pascal) and, notably, by the Nobel Laureate, James Cronin, during a sabbatical visit to the University Leeds in 1991. MOCCA was eventually translated into FORTRAN. In the late 1980s, Hillas published his ideas about techniques for distinguishing between gamma rays and hadrons in the cosmic rays at energies around one tera-electronvolt (1 TeV). The concept involves using large mirrors to detect the Cherenkov radiation which these low-energy cosmic-rays produce in Earth's atmosphere. The "Hillas parameters" are used world-wide in cosmic ray research and play an essential role for the Cherenkov Telescope Array, which detects gamma rays in the energy range from 10 GeV to about 300 TeV.

Awards and honours In 1998 the Institute of Physics (IOP) awarded Hillas the institute's Rutherford Medal and Prize. In 2005 the Commission on Astrophysical Particles of the International Union of Pure and Applied Physics (IUPAP) awarded him the Yodh Prize “for his significant and outstanding contributions to the field of cosmic ray astrophysics”.

Selected publications

Books (1st edition 1972)