Detectron president J L Cassingham holding a model DG-2 Geiger counter, in a 1955 publicity photo
In the late 1940s, Larry Cassingham worked in the sales department for the Goldak company in Glendale, California. The company made products designed to detect underground objects such as cables, pipes, leaks, and such. Cassingham began to notice a growing number of inquires about whether Goldak also carried Geiger counters and similar radiation devices. After all, the Nuclear Age was then only a few years old, and the US Government was offering substantial royalties to uranium ore prospectors. Seeing a tremendous business opportunity, Cassingham suggested to Goldak manager Fred Greenhalgh they expand their line to include Geiger counters. However, Greenhalgh wasn't interested.
Undaunted, Cassingham raised some capital and left Goldak. He, and electronics engineer and friend Jack Rondou, founded Detectron in 1949 in North Hollywood, California. Recalls Cassingham, "Jack coined the name Detectronics for our company name. I suggested we shorten it to Detectron, and that's the name that stuck." Detectron's product line would include Geiger counters and metal detectors of various kinds.
While Cassingham concentrated on a network of sales dealers and promotion, Rondou concentrated on designing the company's core product: the DG2 Geiger counter. One obstacle was to design a circuit that would develop the nearly 1000 volt potential to operate the heart of the device: the Geiger-Mueller tube. Put simply, the G-M is a small tube, which contains a suitable gas such as argon, and a thin wire anode. The thin metal casing is its cathode. To operate it, the high voltage supply is applied. When the tube is placed in close proximity to a "hot" source such as uranium, the radiation causes brief, minute sparks between the casing and wire. Circuits in the Geiger counter amplify the sparks' pulses into audible clicks in headphones, and deflections on the needle of a meter, showing the "count", or number of pulses per second. The "hotter" the sample being read, the higher the count reading, and more rapid the clicks. (Here is a 56 kb .wav file of clicks produced by a thorium sample.)
When Detectron came into being, a portable Geiger counter was already available from Omaha Scientific, using three 300 volt batteries. The battery combination provided a stable source of the high voltage, but at the expense of making the instrument heavy and bulky - not necessarily what the amateur uranium prospector wanted to lug around in the desert! Rondou solved the design problem, and based his voltage-doubler circuit on the much-lighter 45 volt battery. (Remember, this was long before the availability of the three-pin voltage regulator chip!)
Their premier product was born. The DG-2 contained the G-M tube, battery and electronics contained in a compact unit. Later, the DG-7 was developed, which featured a belt clip, and a detachable "probe" that contained the G-M tube. At $98.50, Detectron sold over 20,000 Geiger counters, through dealers and direct sales, in three years' time. At its peak, Detectron had 125 employees.
To keep his radiation detection instruments accurately calibrated, Cassingham relied on the high standards kept at Los Angeles' Western Radiation Laboratory, operated by Dr Gordon Locher. Dr Locher is also known for pioneering the use of radiation therapy to battle cancer.
During this time, Detectron invented a new product, and Cassingham coined its name -- the nucliometer. A bigger but still portable device, it could detect radiation from large sources from farther away. One could search from the shelter of the car, or even from low-flying survey aircraft. In the 1950s, it was a long time before today's GPS and other surveying satellites. How could someone detect ground-based radiation from a plane and then go back and find that spot once the plane lands? "Easy," smiles Cassingham. "You'd fly in a systematic pattern over the area you're interested in. When you got a positive reading on the nucliometer, you'd drop a sack of flour out the plane window. Later, you'd drive back to the area and look for the big white flour spot!"
Cassingham recalls "back then, everyone was interested in our instruments. Once, we were docked in a friend's sailboat, and I had brought along a nucliometer. A man came over from another boat in an adjacent slip, and asked us a lot of questions about it, what it did, how it worked, and so forth. The man was Humphrey Bogart.
"Speaking of actors, another time, I was in my office when someone knocked at the door. I looked up and it was Clint Eastwood. Boy, his presence sure excited some of the young ladies in the office!"
Copyright © 2000-2011 Curt Cassingham. All Rights Reserved.
Last updated June 19, 2005