"Protection begins with Detection" 

 

 

 

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Arrow-Tech Dosimeter Construction Principles

Typical Low Range Plastic Dosimeter

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to see an exploded view

Lower End Cap Electrostatic Shield Ionization Chamber Conductive Fiber Window Serialized Label Upper Barrel Eyepiece Cup w/Reticle Pocket Clip
Eyepiece Lens - 2 required Upper End Cap
Electrometer Objective Lens Ionization Chamber
Charging Pin Diaphragm Switch Lower Barrel Eyepiece Spacer
Frame

Direct Reading Dosimeters

Item Description Item Description Item Description Item Description
1 Diaphragm Switch 6 Ionization Chamber 11 Upper Barrel 16 Pocket Clip
2 Electrostatic Shield 7 Objective Lens 12 Upper End Cap 17 Frame
3 Charging Pin 8 Eyepiece Cup w/Reticle 13 Lower Barrel 19 Conductive Fiber
4 Electrometer 9 Eyepiece Spacer 14 Lower End Cap 25 Serialized Label
5 Ionization Chamber 10 Eyepiece Lens - 2 required 15 Window    

A conductive fiber dosimeter is a rugged precision instrument consisting of an ionization chamber (5) sensitive to radiation; a conductive fiber electrometer (4) to measure the charge; and a microscope to read the fiber on a reticle (8).

The electrometer embodies two electrodes, one of which is a moveable conductive fiber.  When the electrometer is charged to a predetermined voltage, the electrodes assume a calibrated separation.

As the dosimeter is exposed to radiation, ionization occurs in the surrounding chamber decreasing the charge on the electrodes in proportion to the exposure.   The deflection of the moveable conductive fiber electrode is projected, by a light source, through an objective lens (7) to the calibrated reticle and read through a microscope eyepiece (10).

Illumination for the optical system is obtained by pointing the dosimeter at any convenient light source.  Light passes through the clear plastic electrostatic shield (2) to illuminate the reticle.

The bottom is sealed by the clear plastic diaphragm switch (1) containing an insulated charge pin (3).  When charging, the pin moves up to contact the electrometer closing the circuit.  Sufficient voltage is applied to recharge the system.

The entire system is encased in a liquid crystal polymer (LCP) barrel (11 and 13) with all joints hermetically sealed with epoxy. 

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Last modified:  03/10/08