A SIMPLE GEIGER COUNTER 439

the countless number of his physics students, and a textbook writerwithout peer, continues with us.

MILTON D. OESTREICHERRAY C. SOLIDAYGLEN W. WARNER

A SIMPLE GEIGER COUNTER PROJECTGEORGE EDGAR BRADLEY

Western Michigan College, Kalamazoo, Mich.

The appearance on the market of low voltage Geiger tubes such asthe Victoreen 1B86 provides the means for a simple project in theconstruction of a portable Geiger survey meter. The instrument em-ploys a 1B86 Geiger tube, a CK722 transistor or equivalent, a oneampere 6.3 volt filament transformer and six NE-2 neon bulbs. Theinstrument may be powered by two or four penlight dry cells.

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Since the transistor is used to amplify the Geiger pulse, crystalphones are not needed, but quite audible "clicks" may be heard withordinary 2000 ohm headphones. The transistor used in this way con-stitutes the conventional grounded emitter amplifier.The 300 volts for the Geiger tube is supplied by interrupting by

means of a push button switch the current in the primary of the trans-former. Actually the filament transformer is used in reverse with the

440SCHOOL SCIENCE AND MATHEMATICS

6.3 volt winding acting as the primary. Upon the breaking of the cir-cuit, the six neon tubes conduct,�charging a capacitor. Overchargeis not possible since the neon tubes act as regulators as well as recti-fiers. Preliminary polarity tests will indicate proper connections ofthe transformer for charging the capacitor positive with respect toground. Several interruptions will charge the capacitor sufficientlyfor several minutes operation.

Figure I shows a diagram of the counter and Figure II a photographof the author’s model built on a 3//X4/’X5’/ chassis with a cupboarddoor handle for carrying.

Although simple in construction and made from standard partsavailable from any large radio store for less than $12.00, this piecemakes a serviceable unit. The experience of construction makes it anideal project for senior high school physics.

DEPARTMENT OF BIOLOGICAL SCIENCESThe Department of Science at Margaret Morrison Carnegie College has been

renamed the Department of Biological Sciences, and part of the science instruc-tion given by the Department has been transferred to the Carnegie Tech Collegeof Engineering and Science, President J. C. Warner announced.

Instruction in the biological sciences will continue at the women^s college, butchemistry, mathematics and physics courses will be transferred to the appropri-

ate departments in the College of Engineering and Science beginning July 1,1956.

Dr. Warner explained that the advantages in the move are two-fold: "Mar-garet Morrison faculty members concerned will become members of a largescience department where daily association with colleagues in the same field willprovide greater stimulation and exchange of ideas." The second advantage isadministrative. "Instruction and the degree in each of these three sciences cannow be offered by one college instead of two."Women students seeking a degree in chemistry, mathematics, or physics will

be enrolled as regular students in the College of Engineering and Science.