RCL Gas Flow Counter (ca. 1953 - 1960)


This is a windowless gas flow counter designed to operate in either the proportional or geiger mode. Although it carries no model number or other type of identification, it is clear that it was manufactured by Radiation Counter Laboratories, Inc, of Skokie Illinois.  Prior to 1955 or so, it was known as the Mark 12 Model 2. Later, it became known as the Model 10200. 


The upper part of the unit contains a cylindrical counting chamber. The lower rotating section contains three sample wells. One well, containing the sample being counted, is positioned under the chamber. While the counting is in progress, the second well, also containing a sample, is being purged (pre-flushed) this takes 1 2 minutes.  The third well is positioned at the front to accept the next sample. The glass chamber on the side of the counter (upper right in photo) is used to monitor the gas flow. This is done by observing the rate at which the gas bubbles through the oil in the glass chamber. Typical flow rates are on the order of 1 3 bubbles per second.

Counting Gas:      GM:                 helium, isobutene (quench mix flow gas)

                              Proportional:    pure methane

Operating voltage:         GM  1300 volts

                                        Proportional:     alpha  2700 volts

                                                                 beta    3900 volts

Sample well  diameter: 1 1/32

Size: 4.5 in diameter x 2.5 high

Weight: 6.5 pounds

Material: chrome plated brass



RCL Radiation Detectors Catalog, no date;

Atomic Energy Commission Radiation Measuring Instruments RIB (Part 2) Supplement, page BG-5Q, July 1, 1954.

Donated by Ron Kathren

Proportional Counters                   Museum Directory

Last updated: 05/10/11
Copyright 1999, Oak Ridge Associated Universities