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Gilbert's versorium

The first electroscope was Gilbert's Versorium and was discovered in 1600's. It is a conductive needle which when in the vicinity of electrified body charge-up and than interact with the anything electrified around. If you ask me, a bit of magnetization will make the life of the observer a bit easier by providing a counter-tork. To be used as a radiation detector, one just have to asses how fast the needle discharge, when radiation produce ionization


Mica detector

It is a passive alpha particle detector, used as passive radon detector, ideal e.g. for long-term radon test.

How it works? The alpha radiation, which comes from radon and its progeny does microscopic damage to the surface of mica detector. After chemical etching the damaged area is enlarged and seen as tracks. The tracks can be counted and related to the radon concentration in the air in which the detector was exposed.

Mica detector


The Henson Electroscope is a pioneers instrument dedicated to the measurement of radiation. Designed by Charlie Lauritsen around ~1937 and produced by Fred Henson Company of Pasadena, it became immensely popular. It had both the sensitivity required for use in the laboratory and the portability that allowed it to serve as a type of survey instrument, at a time no true survey instruments were commercially available.

The incident radiation produces ionize atoms in the chamber volume, which creates a current flow. Consequently the charge on the electrode decreases. Due to this decrease, the quartz fiber moves and its deflection can be projected by a light source to a calibrated scale through an objective lens. Since the deflection of the quartz fiber is proportional to the current flowing through the chamber, therefore it is a measure of the dose delivered by the radiation. Upon full discharge, the electroscope charged again, applying a voltage through a charging pin.

The drawing abouve is reproduced from ORAU Museum Library

Chak River Detectors

Such instruments were built at Chalk River Laboratory sometime around 1945. Originally designed for gamma-emitting samples, but this device was used to measure beta-emitting samples being inserted into a hemispherical chamber via a sliding drawer.

Spy story from the 1940's:


The spy story was originaly presented in ORAU Museum Library



"Argentinian Invention": a "selfsuficient" apparatus that can be used as electroforus, radiation monitor and, of cause, electrometer.



Am I right? Can you figure-out those three functions?


Lindemann Electrometer, 1936. It is a quadrant Electrometer originally designed by Lindemann to measure the


light of stars but ended to be an important instrument for radiation levels measurements and nuclear safety,

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