Page "government" Paragraph 265

A high-speed shutter has been developed in order to permit photographic observation of any portion of the electrical wire explosion.

The shutter consists of two parts: a fast-opening part and a fast-closing part.

Using Edgerton's method, the fast-closing action is obtained from the blackening of a window by exploding a series of parallel lead wires.

The fast-opening of the shutter consists of a piece of aluminum foil ( approximately Af ) placed directly in front of the camera lens so that no light may pass into the camera.

The opening action is obtained when a capacitor, charged to high voltage, is suddenly discharged through the foil.

During the discharge the magnetic forces set up by the passage of current cause the edges of the foil to roll inward toward its center line, thus allowing light to pass into the camera.

Experiments have shown that the shutter is 75 percent open in about 60-80 microseconds.

The shutter aperture may be made larger or smaller by changing the foil area and adjusting the electrical energy input to the foil.

Laboratory measurements of interstellar radio spectra.