Personal radiation dosimeters

Abstract

A personal radiation dosemeter comprising a radiation detector means coupled to an electronic measurement circuit arranged in combination therewith to generate signals representative of an amount of radiation detected by the radiation detector. The radiation detector means is arranged to be screened from ambient light and is further provided with a light source optically coupled to the radiation detector and arranged to operate under control of a test control circuit to generate light of a wavelength which may be detected by said radiation detector. This arrangement provides, in combination with said electronic measurement circuit an integrity test for said radiation detector means.

1 . A personal radiation dosemeter comprising a radiation detector means coupled to an electronic measurement circuit arranged in combination therewith to generate signals representative of an amount of radiation detected by said radiation detector, wherein said radiation detector means is provided with a light source optically coupled to said radiation detector means and arranged to operate under control of a test control circuit to generate light of a wavelength which may be detected by said radiation detector, thereby providing in combination with said electronic measurement circuit an integrity test for said radiation detector means.  
     
     
         2 . A personal radiation dosemeter as claimed in  claim 1 , wherein the light source is a light emitting diode.  
     
     
         3 . A personal radiation dosemeter as claimed in claims  1  or  2 , wherein the optical coupling includes an optical fibre arranged to convey the light to said radiation detector means.  
     
     
         4 . A personal radiation dosemeter as claimed in claims  1  or  2 , wherein the optical coupling is effected by reflection via a surface of the shield.  
     
     
         5 . A personal radiation dosemeter as claimed in any preceding claim, further including a screen which serves to shield said radiation detector from ambient light.  
     
     
         6 . A personal radiation dosemeter comprising a radiation detector means coupled to an electronic measurement circuit and arranged in combination to generate signals representative of an amount of radiation received by said radiation detector means, wherein there is further provided a shield arranged to be electrically coupled to an earth plane and to substantially surround a volume in which said radiation detector means is disposed, said shield being fabricated from electrically conductive material so as to provide substantial electromagnetic screening, which electrically conductive material has a composition and density sufficiently high to provide substantial radiological shielding, for substantially low energy radiation particles, said shield being thereby arranged to provide both electromagnetic and radiological screening.  
     
     
         7 . A personal radiation dosemeter as claimed in  claim 6 , wherein said electrically conductive material is a metal.  
     
     
         8 . A personal radiation dosemeter as claimed in  claim 7 , wherein the metal is tin.  
     
     
         9 . A personal radiation dosemeter as claimed in  claim 7 , wherein said electrically conductive material is an alloy.  
     
     
         10 . A personal radiation dosemeter as claimed in  claim 9 , wherein the alloy is pewter.  
     
     
         11 . A personal radiation dosemeter for generating a monitor signal representative of a radiation dose rate, said radiation dosemeter comprising a radiation detector means coupled to an electronic measurement circuit and arranged in combination therewith to generate signals representative of an amount of radiation received by said radiation detector, wherein said electronic measurement circuit includes at least one data store, an accumulator means and control circuit means, which control circuit means is coupled to said radiation detector means and arranged to add a predetermined number stored in said data store to an accumulated total stored in said accumulator in response to signals from said radiation detector means, said control circuit being arranged to generate a monitor signal for each increment of said accumulated total by said predetermined numerical threshold, which monitor signal is fed to an audio signal generator so as to provide an audible signal in accordance with said increment, a repetition frequency of said audible signal being thereby representative of said radiation dose rate.  
     
     
         12 . A personal radiation dosemeter as claimed in  claim 11 , further comprising at least one other radiation detector means and at least one other data store, wherein said at least one other data store includes a further predetermined number and said control circuit operates to add said further predetermined number to said accumulator consequent upon receipt of signals from said at least one other radiation detector means.  
     
     
         13 . A personal radiation dosemeter as claimed in  claim 12 , wherein said first and said further predetermined numbers are selected in combination with the numerical threshold, so that the radiation dosemeter is arranged to generate a monitor signal at a frequency which is arranged to provide an audible indication determined by the relative harm caused by the radiation detected by the first and further radiation detector means.  
     
     
         14 . A personal radiation dosemeter as claimed in any of  claims 10  to  12 , wherein said predetermined numerical threshold is representative of a maximum count which is available to said accumulator, and said monitor signal is generated from an overflow signal generated by the accumulator.  
     
     
         15 . A method of generating a monitor signal representative of a radiation dose rate, said method comprising the steps of: 
 adding said predetermined number to an accumulated total upon receipt of a first signal from a first radiation detector,    comparing said accumulated total with a predetermined numerical threshold and    generating a monitor signal if the accumulated total has changed since a last monitor signal was generated by said predetermined numerical threshold.    
     
     
         16 . A method of generating a monitor signal as claimed in  claim 15 , further including the steps of 
 adding said further predetermined number to said accumulated total upon receipt of a further signal from a further radiation detector.    
     
     
         17 . A personal radiation dosemeter as hereinbefore described with reference to FIGS. 1, 2,  3  and  4 .