AC Operation Research Articles

Transistorized Ratemeter Design

Extensively increasing adaptation and use of radioactive isotopes for in vivo studies of the circulatory system has dictated improvement in the electronic instrumentation necessary to detect and measure progress of the isotope through the system. Inasmuch as the time intervals of circulatory studies are rather short (not over 30 sec), speaking on a gross scale, measurements at several different checkpoints must be accomplished with duplicate immobilized detectors rather than a single movable unit. A transistorized ratemeter featuring lower power requirements, smaller space consumption, superior reliability and durability together with the stability of vacuum tube circuits in ac operation has been developed to make practicable multiple channel in vivo counting systems for use in the modern x-ray or operating room.

A hysteresis effect in photoconductive cadmium selenide and its use in a solid-state image storage device

A brief description of a new hysteresis effect in cadmium selenide photoconductive powder will be given. Photocurrent plotted as a function of voltage has the form of a hysteresis loop, with triggering from low to high currents occurring at a voltage depending on the incident light level. At a suitably chosen voltage, triggering from low to high currents occurs with light pulse excitation. Return to the condition of low current flow is brought about by brief interruption of the supply voltage. Since the triggering is present with ac or dc operation, it is possible to use the effect in a series circuit of photoconductor and ac operated electroluminescent panel. If this is done on an area basis with due attention paid to the impedance match of the photoconductor and electroluminescent layer, it is possible to make an image storage device having no optical feedback. The construction and operation of such a device is described, and a photograph of a stored image on a 3-inch panel is shown.

Technical Data Concerning the Geiger Counter

As no description of a “Geiger Counter” can be found in medical literature, an investigator wishing to build this instrument has to waste much time in testing various circuits. For that reason this paper seems warranted. The photograph and complete wiring diagram show a successful, self-contained instrument. The author has made certain modifications in the usual circuits, has arranged for complete AC operation with elimination of all batteries, and, with the exception of the tube and recording counter, has used only standard radio receiving parts which are inexpensive and easily obtained in any city. Otherwise, no originality is claimed. The success of this instrument depends on the “Stratosphere Tube” developed by Dr. Gordon L. Locher, of Philadelphia, for cosmic ray determinations, consisting of a small glass tube filled with gases and partially exhausted. When arranged with proper voltage supply, amplifying system, and recorder, it is an extremely sensitive device for the determination of radiation. Th...