A Skeptical Scrutiny of the Works and Theories of WILHELM REICH

As related to

The problems with Reich's use of the Geiger-Müller counter

By Roger M. Wilcox

Last modified 30-July-2003

A Geiger-Müller counter, sometimes simply called a Geiger counter or a GM counter, was invented in its modern form by Johannes Wilhelm "Hans" Geiger and Walther Müller in 1925.  It consists primarily of a gas-filled glass tube containing two electrodes.  The positive electrode is a narrow wire running down the center.  The negative electrode is a hollow metal cylinder placed just inside the glass, arranged coaxially with the center-wire electrode in a manner similar to a coaxial TV cable.  (This tube is similar to Reich's VACOR tubes, and is in fact where Reich got his idea for VACOR tubes.)  The two electrodes are wired to an adjustable high voltage source called the Geiger-Müller amplifier.

The amplifier provides several hundred Volts of electric potential.  It is up to the operator to adjust the amplifier voltage so that it is just below the threshold voltage where electrical current will leap across the electrodes inside the tube.  Then, when a quantum of ionizing radiation (a charged particle or an X-ray or gamma-ray photon) passes through the tube, it knocks a few electrons loose from the gas molecules in the tube, lowering the gas's breakdown voltage.  This results in a short, intense pulse of current jumping from the negative electrode to the positive electrode, much like a very very low-power lightning bolt.  This current pulse is measured or counted by other parts of the apparatus; the number of current pulses per second tells you how "intense" the ionizing radiation field across the tube is in terms of how many high-energy particles or photons are crossing the tube per second.  Note that the number of particles per second does not directly indicate how strong the radiation is.  A radioactivity source emitting 5000 fast alpha particles (a heavy charged particle) per second is a much stronger radiation source than one that emits 5000 slow electrons (a lightweight charged particle) per second, but these two sources would give identical readings on the same G-M counter with the same calibration settings held the same distance away.

Modern Geiger-Müller counters use digital pulse counters, but those in Reich's time probably used some kind of rotary dial that advanced, a tiny amount, each time a count was recorded.  Note that the energy of the radiation incident on a Geiger-Müller tube is not what causes the counter to turn.  To make a complete Geiger-Müller counter, the tube must be connected to an external voltage source.  It is this external source that provides the current pulse through the tube when ionizing radiation hits it.  The energy to turn the rotary pulse counter comes from these current pulses.

The setting of the voltage level on a Geiger-Müller tube is crucial.  Below a certain minimum voltage, no amount of ionizing radiation will trigger a current pulse and the counter will not register anything.  Above a certain maximum voltage, which occurs well below the breakdown voltage of the gas in the tube, the tube will discharge spontaneously and register counts in the absense of radiation.  (Above the breakdown voltage, of course, the tube will conduct continuously and no individual impulses will be recorded at all.)  The range between this minimum and maximum voltage, over which the G-M tube will operate properly, is called the Geiger plateau.  But even within the Geiger plateau, the higher the voltage across the electrodes, the more sensitive the tube will be to lower levels of ionizing radiation, and the higher the impulse count will be for the same amount of radiation.  Furthermore, the voltage levels wherein the Geiger plateau actually resides will vary widely from one Geiger-Müller counter to the next.  The type of gas used in the tube, the length of the tube, the gas pressure in the tube, and even the temperature can affect the count rate at a particular voltage setting.

Standard operating procedure is to calibrate your G-M counter by exposing it to a radiation source whose intensity is already known, and adjusting the voltage level so that you get a useful number of counts per minute, and then write this baseline number down somewhere before you begin your experimental work with radiation sources whose levels are not known.  This must be done with every different G-M counter, and every different combination of the same G-M counter components (tube, amp, counter, etc.), every time it is used.  Without doing so, there is simply nothing you can conclude from a high count rate.

Here, then, in a nutshell, are the things that lead me to question Reich's observations with the Geiger-Müller counter:

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