JOURNAL OF CHEMICAL EDUCATION
LABORATORY EXERCISES IN NUCLEAR CHEMISTRY
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IV. A Basic Student Counting Circuit WILLIAM H. HAMILL, RUSSEL R. WILLIAMS, JR., and COLIN F. MACKAY University of Notre Dame, Notre Dame, Indiana
INPREVIOUS articles of this series (1, 2, 5) we have described simple experiments in nuclear chemistry designed for use in undergraduate laboratory instruction and have listed (9) the essential equipment for this type of work together with approximate costs. Excepting the 5-mg. Ra-Be neutron source, the most essential and expensive item is the electronic circuit for operation of a Geiger tube. Those available commercially fall into two classes: (1) rate meters, which give an indice tion of the average count rate over a fixed period of time, and (2) scaling circuits, which total the number of counts in any period of time. Items of type (1) may be purPv / s e
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chased for as little as $100 but are only semiquantitative in operation and are intended chiefly for demonstration purposes. Type (2), the scaling circuits, are excellent for quantitative work but cost $300 or more. For an institution with a research program in nuclear chemistry, or able to purchase a scaling circuit for instruction, the choice is clear. However, when funds are limited or when multiple instructional units are desired, the rate meter type is much less expensive but also less satisfactory. Aside from the inherently qualitative nature of the inexpensive rate meter, we find that it lacks certain desirable pedagogical advantages of the scaler, namely, direct $4.25 dLLe indication of the counts received and quantitative Scale Fbwer response at low counting - ArnpliF;er rates. , of Two 6 6odepm With these considerations I L O O ~ ~6bHb,6SN7 6wym in mind we have set out t o explore the possibility of constructing an adequate ~ I inexuensive student counter circuit. This work has rein the completion of ~ t ~ sulted l Hi -Volts one such circuit a t a cost in parts of approximately $110, described below, and the realization that further ~ i g u r a1. B-~O student counting circuit simple modification can re-
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FEBRUARY. 1951 Pulse
High
Amplifier
V o l t a g e Supply
Scale of Two
2x2
Power Amplifier
5Y3
Plate
Supply
Pigum 2. Student Counter Chcvit
Tahle of Parts 191
lK, 5w 1 meg., I / m 250K, L/lw....$7.50
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6 . 8 2w ~ ~ 1001
