Louis Harold Gray

Louis Harold Gray (10 November 1905 - 9 July 1965) was a British physicist who worked mainly on the effects of radiation on biological systems, inventing the field of radiobiology as he went. A summary of his work is given below. Amongst many other achievements, he defined a unit of radiation dosage which was later named after him as an SI unit, the Gray.

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Summary of Career

• 1933 Hospital physicist at Mount Vernon Hospital, London
• 1936 Developed the Bragg-Gray equation, the basis for the cavity ionization method of measuring gamma-ray energy absorption by materials
• 1937 Built an early neutron generator at Mount Vernon
• 1938 Studied biological effects of neutrons using the generator
• 1940 Developed concept of RBE (Relative Biological Effectiveness) of doses of neutrons
• 1952 Initiated research into cells in hypoxic tumors and hyperbaric oxygen
• 1953 Set up Gray Laboratory at Mount Vernon Hospital
• 1953 - 1960 Under Gray’s direction, Jack W. Boag developed pulse radiolysis
• 1962 Ed Hart (ANL) and Boag discovered the hydrated electron using pulse radiolysis at Gray Lab

This discovery initiated a new direction for chemistry research that is still very active today and is vital for understanding of the effects of radiation on biological tissue, for instance in cancer treatment.

• Definition of RBE.
• The LH Gray Memorial Trust founded in 1967
• A biography