Ring Dosimeters - Technical Specifications

ring dosimeters

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Two ring shaped dosimeters that are adjustable. On the right is a white, small sized ring and on the left, a green, large sized ring. The green ring has a white label with the dosimeter serial number 756064 that is outlined by a black rectangular box. The acronym NDS – SND is centred at the bottom. The white ring has a white label with the dosimeter serial number 422185 that is outlined by a black rectangular box. The word CONTROL is centred at the bottom.  The Health Canada logo with the Canadian flag appears in the top left corner of the white label.

Dosimeter Overview

Ring dosimeters provide X-ray, gamma and beta radiation monitoring using thermoluminescent technology. The dosimeter is assembled by enclosing a thermoluminescence dosimeter (TLD) element of the type known as TLD-100 (LiF:Mg,Ti) in a ring shaped dosimeter holder with the dosimeter identification label pasted on top. A heat shrunk plastic covering is then added to make the dosimeter water resistant. All ring dosimeters are labelled with a unique serial number that identifies the dosimeter assignment. Ring dosimeters are available in two sizes, large (green ring band) and small (white ring band).

Dosimeter Reading Equipment

Ring dosimeters are processed using a Thermo Fisher Scientific model 5500 reader. This reader is designed to prevent ambient light from reaching the photo multiplier tubes (PMTs). The readers read out the radiation exposure recorded on the thermoluminescent element (TLD-100) by thermally stimulating the element.

Dosimeter reader

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One table top Thermo Fisher Scientific Model 5500 thermoluminescent element reader. The front panel view of the reader shows the disk tray, the disk tray eject button and operating lights. The right side panel has an on/off switch located at the bottom centre.

Dose Analysis Process

The dosimeter readings measured by the Thermo Fisher Scientific model 5500 reader are analysed thoroughly to review the classic TLD glow curves. Any anomalous glow curves, identified during the review process, undergo a deconvolution process using a glow curve analysing software that determines the glow curve contribution due to the presence of an anomaly. The anomaly contributions are subtracted from the overall readings for the associated dosimeters to obtain the true dosimetric readings. A dose calculation algorithm is then applied to the readings to determine the overall calculated doses. The background (or environmental) doses for the dosimeters are then determined by reviewing the readings for controls and the known background radiation levels for the clients' geographical locations. The occupational doses for the dosimeters are then finalised by subtracting the background dose contribution from the overall calculated doses. The occupational doses are then reported to the National Dose Registry and an Exposure Report mailed to the client.

chart

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A line graph representing data readings extracted from the thermoluminescent element found on the ring dosimeter. The X axis represents channels and is identified in multiples of 20. The Y axis represents the signal of the dosimetric curve in nano amperes.

Accreditations

Technical Specifications

Dosimeter Name
Ring Dosimeter
Dosimeter Type
Passive
Radiation Detected
X-ray, Gamma and Beta
Wear Location
Hand or Arm Extremity
Doses Reported
Hp(0.07) (Shallow Dose)
Energy Response
Photon (X-ray and Gamma): 33 keV to in excess of 1250 keV Beta (Max): 763 keV to in excess of 2274 keV
Reporting Threshold
1.00 mSv
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