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 Exradin Products
Exradin Ion Chambers 1
Exradin Ion Chambers 2
Exradin Ion Chambers 3
Stem Configurations
Conducting Plastics
Exradin Products









About Exradin

Before its products were acquired Exradin was a small, sharply focused company founded in 1975 as a vehicle for making available to all manner of radiation scientists a number of quality ionization chambers that had been developed in the Physical Sciences Laboratory (PSL) at Benedictine University, Lisle, Illinois. The company was created by John Spokas, successor to Francis Shonka, Ph.D. as director of PSL, and two of Dr. Shonka’s former scientific assistants. Prior to coming to Benedictine University in 1954, Francis Shonka had worked on the Manhattan Project at the University of Chicago and later served as Director of the Instruments Division at Argonne National Laboratory. He established the Physical Sciences Laboratory and directed it until his demise in October of 1970. Between 1978 and now, Exradin was controlled by Ralph Meeker, and John Spokas. Both earned their doctorates in physics, had graduated as physics majors from Benedictine University (formerly known as St. Procopius College, later as Illinois Benedictine College), and currently are faculty members at Benedictine University.

The guiding philosophy of Exradin has always been to offer quality products of uncompromising scientific integrity at reasonable cost. Exradin ion chambers are characterized by sound and careful design and sturdy construction. In order to obtain accurate and clearly interpretable measurements free of spurious effects, Exradin chambers use homogenous construction, are fully guarded, and do not employ troublesome conductive coatings.

Originally, Exradin offered Shonka-Wyckoff chambers which were designed to measure exposure and air kerma and which are suitable as transfer standards, large spherical low-level chambers with which background radiation may be measured, and the Spokas and Miniature Shonka thimble chambers for critically evaluating therapy beams. The most recent chamber developments include the Farmer Type chamber, the Exradin Microchamber, and a versatile thin-window parallel-plate chamber. The Exradin Farmer Type unit uses an air-equivalent conducting plastic throughout in its construction, including the collector which is only 1 mm in diameter. The original Farmer chamber as well as those of this type made by all other manufacturers employ metallic collectors which compromise the integrity of the chamber in order to achieve a flatter low energy response in uniform fields. The microchamber, which is finding increased use in evaluating stereotactic radiation fields, can be viewed as a small thimble chamber with a collector of zero length. The design of the collector and guard in the microchamber confines the collecting volume to the very tip of the chamber. The thin-window chambers were introduced in the summer of 1994. These use a stretched conductive Kapton film of thickness 3.9 mg/cm2 . A protective cover is available which when set over the window allows the chamber to be operated while fully submerged. Thus, the same chamber may be used for dose measurements in mammography, the evaluation of superficial x-ray beams and electron beams of all energies, and the calibration of various treatment beams using liquid phantoms.

Please feel free to contact us with any questions that you may have.

For an Electrometer for use with your Exradin Ion Chamber please click here

If you are interested in any of the products mentioned here, please fill out an Enquiry Form or Go To the Ion Chamber Product List / Quotation Request Form, so that we may promptly respond to your request.



Please contact Colin Walters at cwalters@seedos.com if you would like further  information or you have questions

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SeeDOS Ltd, 26, The Maltings, Leighton Buzzard, Bedfordshire LU7 4BS, United Kingdom
Tel: +44 1525 850 670  • Fax: +44 1525 850 685