A high‐speed two‐bladed shutter was built to deliver square‐wave pulses of energy from a converging light beam with an average intensity of about 5 cal/cm2/sec, and a diameter of 3 in., in the plane of the shutter. The blades open or close in less than 0.01 sec. They move in the same direction, so that all parts of the target are exposed for very nearly the same length of time. The shutter makes use of a new type of air cylinder which is suitable for driving high‐speed mechanisms, and has a dynamic shock absorbing system to stop the moving parts in a short distance with little rebound. It is electrically controlled and fully automatic. Exposure times may be varied from 0.07 to 5 sec by setting an electronic interval timer. Longer exposures are controlled manually. To date it has been used more than 15 000 times and has required only two overhauls.

Topics
Thermodynamic states and processes, Wave forms
1.
The two curves for the sweep technique are not exact experimental curves since the beginning and end portions of the curves, where the intensity is changing at a slow rate, have been neglected owing to difficulty in selecting an absolute zero time. The neglected portions of the curves contribute approximately 6 percent more energy to the pulses.
2.
Made by the Rubatex Division of Great American Industries, Inc., Bedford, Virginia.
3.
Type 5201‐B, manufactured by the Automatic Temperature Control Company, Inc.
4.
Model S‐1 with ac clutch made by the Standard Electric Time Company.
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© 1954 American Institute of Physics.
1954
American Institute of Physics
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