Quartz fiber dosimeter

A quartz fiber dosimeter, sometimes called a self indicating pocket dosimeter (SIPD) or self reading pocket dosimeter (SRPD) or quartz fibre electrometer (QFE), is a type of radiation dosimeter, a pen-like device that measures the cumulative dose of ionizing radiation received by the device, usually over one work period. It is clipped to a person's clothing, normally a breast pocket for whole body exposure, to measure the user's exposure to radiation. It is now being superseded by more modern dosimeter types such as the electronic personal dosimeter (EPD). As with other types of personal radiation dosimeter, it is worn by workers who are occupationally exposed to radiation, so their employers can keep a record of their exposure, to verify that it is below legally prescribed limits. It works by measuring the decrease in electrostatic charge on a metal conductor in an ionization chamber, due to ionization of the air in the chamber by radiation. It was invented in 1937 by Charles Lauritsen. The dosimeter must be periodically recharged to restore it to a zero dose reading after being exposed to radiation. It is normally read immediately after use, and the dose is logged to record the user's exposure. In some organizations, possession of the recharging device is limited to health physicists to ensure accurate recording of exposures. It contains a low-power microscope and an illumination lens which allow direct reading of exposure at any time by aiming the illumination lens at a light source and looking into the microscope. The device is mainly sensitive to gamma and x-rays, but it also detects beta radiation above 1 MeV. Neutron sensitive versions have been made. Quartz fiber dosimeters are made in different ranges. Peace-time occupational exposure ranges usually measure up to 500 mrem (5 mSv), which exceeds the normal US yearly dose of 360 mrem (3.6 mSv). War-time fallout meters measure up to 500 rem (5 Sv), roughly the lethal dose. The quartz fiber device is an older dosimeter design.