A DISTINGUISHED SCIENTIST

Press, Volume LXXXIII, Issue 25270, 23 August 1947, Page 7

A DISTINGUISHED SCIENTIST

DR. J. W. MITCHELL RETURNS

HIGH-SPEED PHOTOGRAPHY INVENTION

A distinguished New Zealand scientist, Dr. J. W. Mitchell, has returned to Christchurch and is giving a course of 12 lectures to advanced chemistry, physics, and engineering students at Canterbury University College. Dr. Mitchell is noted for the invention of the arditron tube which made revolutionary improvements in high-speed photography. A son of Mr and Mrs J. W. Mitchell, 17 Regent street, Dr. Mitchell had an outstanding career as a schoolboy at the Sydenham and Christchurch Boys’ High Schools. He was University National scholar in 1930 and entered Canterbury College in 1931, where he was senior scholar in chemistry and graduated with a master of science degree. He was awarded an 1851 science scholarship in 1935 and went to Oxford University, where he studied chemical physics under Professor C. N. Hinshelwood at Trinity College. He became a doctor of philosophy in 1937 and spent another year at Oxford on research work. He then went to Repton School as physics master. Called up on the outbreak of war, Dr. Mitchell was assigned to the Ministry of Supply Armaments Research Department at Woolwich and became scientist in charge of the department’s Grantham out-station. He worked on the development of 20 and 30 mm. Hispano guns and parallel development of new methods for high-speed photography of shells in flight and on im- | pact with armour-plate targets. i It was at this stage that Dr. Mitchell invented the discharge tube called the arditron, which was later widely used in Great Britain and the United States in all armaments research establishments. The tube gives a flash with an effective photographic duration of half a millionth of a second and with a peak intensity of 120,000,000 candlepower. It is used extensively in research on ballistics, shells, shell and target interaction, under-water ballistic trajectories, and explosive phenomena. In January, 1944, Dr. Mitchell was transferred to the headquarters of the Armaments Research Department to take charge of high-speed photography. He was released in September, 1945, and was appointed lecturer in physics at the University of Bristol under Professor A. M. Tyndall, specialising in physical. optics, instrumental optics, and spectroscopy. He also did research work with Ph.D. students in close collaboration with theoretical research groups under Professor N. F. Mott. In Christchurch, Dr. Mitchell is lecturing on chemical physics of the solid state, and next month he will address the Canterbury branch of the Royal Society of New Zealand. In October, he will go to Australia and spend five weeks lecturing to the Commonwealth Scientific ana Industrial Research divisions at Sydney and Melbourne, and he will fly back to Bristol in November.