Editing Dosimeter (section)

==Personal dosimeters==
[[File:CNX Chem 21 06 Exposure1.png|thumb|Example of "whole body" dosimeter positioning]]
The personal ionising radiation dosimeter is of fundamental importance in the disciplines of [[dosimetry|radiation dosimetry]] and radiation [[health physics]] and is primarily used to estimate the radiation dose deposited in an individual wearing the device.

Ionising radiation damage to the human body is cumulative and related to the [[Effective dose (radiation)|total dose]] received, for which the [[SI]] unit is the [[sievert]]. [[Radiographer]]s, [[nuclear power plant]] workers, doctors using [[radiotherapy]], [[HAZMAT]] workers, and other people in situations that involve handling radionuclides are often required to wear dosimeters so a record of occupational exposure can be made. Such devices are known as "legal dosimeters" if they have been approved for use in recording personnel doses for regulatory purposes.

Dosimeters are typically worn on the outside of clothing, a "whole body" dosimeter is worn on the chest or torso to represent dose to the whole body.  This location monitors exposure of most [[vital organ]]s and represents the bulk of body mass.  Additional dosimeters can be worn to assess dose to extremities or in radiation fields that vary considerably depending on orientation of the body to the source.

===Electronic personal dosimeters===
{{Main|Electronic personal dosimeter}} [[File:Crocus-p1020509.jpg|thumb|View of readout on an electronic personal dosimeter. The clip is used to attach it to the wearer's clothing.]]
The electronic personal dosimeter, the most commonly used type, is an electronic device that has a number of sophisticated functions, such as continual monitoring which allows alarm warnings at preset levels and live readout of dose accumulated. These are especially useful in high dose areas where residence time of the wearer is limited due to dose constraints. The dosimeter can be reset, usually after taking a reading for record purposes, and thereby re-used multiple times.

====MOSFET dosimeter====
[[MOSFET|Metal–oxide–semiconductor field-effect transistor]] dosimeters <ref>{{cite web |url=http://www.mosfet.ca/global/pdf/technotes/te_4.pdf |title=Archived copy |access-date=2015-04-04 |url-status=dead |archive-url=https://web.archive.org/web/20150410104912/http://www.mosfet.ca/global/pdf/technotes/te_4.pdf |archive-date=2015-04-10 }}</ref> are now used as clinical dosimeters for radiotherapy radiation beams. The main advantages of MOSFET devices are:

1. The MOSFET dosimeter is direct reading with a very thin active area (less than 2μm {{Clarify|2 μm|μm is a measore unit for length, not for area|date=February 2023}}).

2. The physical size of the MOSFET when packaged is less than 4&nbsp;mm.

3. The post radiation signal is permanently stored and is dose rate independent.

[[Gate oxide]] of [[MOSFET]] which is conventionally [[silicon dioxide]] is an active sensing material in MOSFET dosimeters. Radiation creates defects (acts like electron-hole pairs) in oxide, which in turn affects the [[threshold voltage]] of the MOSFET. This change in [[threshold voltage]] is proportional to radiation dose. Alternate high-k gate dielectrics like [[hafnium dioxide]]<ref>{{Cite journal | doi=10.1016/j.tsf.2011.07.010| title=Dosimetry aspects of hafnium oxide metal–oxide–semiconductor (MOS) capacitor| journal=Thin Solid Films| volume=520| issue=1| pages=574–577| year=2011| last1=Senthil Srinivasan| first1=V.S.| last2=Pandya| first2=Arun| bibcode=2011TSF...520..574S}}</ref> and aluminum oxides are also proposed as a radiation dosimeters.

==== PIN dosimeters ====
[[PIN diode|PIN diodes]] are often used by military personnel for measuring radiation dosage.

==== Scintillation counter ====
{{Main|Scintillation counter}}
A scintillation counter detects ionizing radiation by measuring the light emitted from a [[scintillator]], giving a measurement of radiation levels almost instantly. Like thermoluminescent crystals, scintillation materials begin to glow when exposed to radiation. Unlike thermoluminescent crystals, which store absorbed radiation to measure accumulated doses over a period of time, scintillation materials release light immediately, and do not need to be heated.<ref>Archambault, Louis et al. “Toward a real-time in vivo dosimetry system using plastic scintillation detectors.” ''International journal of radiation oncology, biology, physics'' vol. 78,1 (2010): 280-7. doi:10.1016/j.ijrobp.2009.11.025. (https://pmc.ncbi.nlm.nih.gov/articles/PMC2889037/)</ref>

====Thermoluminescent dosimeter====
{{main|Thermoluminescent dosimeter}}
A thermoluminescent dosimeter measures ionizing radiation exposure by measuring the intensity of light emitted from a Dy or B doped crystal in the detector when heated. The intensity of light emitted is dependent upon the radiation exposure. These were once sold surplus and one format once used by submariners and nuclear workers resembled a dark green wristwatch containing the active components and a highly sensitive IR wire ended diode mounted to the doped LiF2 glass chip that when the assembly is precisely heated (hence thermoluminescent) emits the stored radiation as narrow band infrared light until it is depleted <ref>{{Cite journal|url=https://pubs.rsna.org/doi/10.1148/87.5.938|doi = 10.1148/87.5.938|title = Lithium Fluoride Thermoluminescence Dosimetry|year = 1966|last1 = Worton|first1 = R. G.|last2 = Holloway|first2 = A. F.|journal = Radiology|volume = 87|issue = 5|pages = 938–943|pmid = 5924913}}</ref> The main advantage is that the chip records dosage passively until exposed to light or heat so even a used sample kept in darkness can provide valuable scientific data.<ref>{{Cite web|url=https://patents.google.com/patent/US4173660A/en|title = Method of preparing a thermoluminescent phosphor}}</ref>

===Legacy types of dosimeters===
====Film badge dosimeter====
{{main|Film badge dosimeter}}
Film badge dosimeters are for one-time use only. The level of radiation absorption is indicated by a change to the film emulsion, which is shown when the film is developed. They are now mostly superseded by electronic personal dosimeters and thermoluminescent dosimeters.

====Quartz fiber dosimeter====
 {{Main|Quartz fiber dosimeter}}
These use the property of a quartz fiber to measure the static electricity held on the fiber. Before use by the wearer a dosimeter is charged to a high voltage, causing the fiber to deflect due to electrostatic repulsion. As the gas in the dosimeter chamber becomes [[Ionization|ionized]] by radiation the charge leaks away, causing the fiber to straighten and thereby indicate the amount of dose received against a graduated scale, which is viewed by a small in-built microscope.<ref name="Frame">{{cite web
  | last = Frame
  | first = Paul
  | title = Pocket Chambers and Pocket Dosimeters
  | work = ORAU Museum of Radiation and Radioactivity
  | publisher = Oak Ridge Associated Universities
  | date = 2007-07-25
  | url = https://www.orau.org/health-physics-museum/collection/dosimeters/index.html
  | access-date = 2021-10-07}}</ref>
They are only used for short durations, such as a day or a shift, as they can suffer from charge leakage, which gives a false high reading.
However they are immune to EMP so were used during the Cold War as a failsafe method of determining radiation exposure.

They are now largely superseded by electronic personal dosimeters for short term monitoring.

====Geiger tube dosimeter====
These use a conventional [[Geiger–Müller tube]], typically a ZP1301 or similar energy-compensated tube, requiring between 600 and 700V and pulse detection components. The display on most is a bubble or miniature LCD type with 4 digits and a discrete counter [[integrated chip]] such as 74C925/6.{{Citation needed|date=July 2023}} LED units usually have a button to turn the display on and off for longer battery life, and an infrared emitter for count verification and calibration.
The voltage is derived from a separate pinned or wire-ended module that often uses a unijunction transistor driving a small step-up coil and multiplier stage. While expensive, it is reliable over time and especially in high-radiation environments, sharing this trait with tunnel diodes, though the encapsulants, inductors and capacitors have been known to break down internally over time.{{Citation needed|date=July 2023}}
These have the disadvantage that the stored dose in [[becquerels]] or [[microsieverts]] is volatile and vanishes if the power supply is disconnected, though there can be a low-leakage capacitor to preserve the memory for short periods without a battery. Because of this, most units use long-life batteries and high-quality contacts. Recently-designed units log dose over time to non-volatile memory, such as a 24C256 chip so it may be read out via a serial port.