Time-averaged radon daughters (WL) dosimeter and method for surveys of indoor, outdoor and underground (MINE) contamination

Claim 3

The method as claimed in claim 1, wherein said plurality of collimators comprise an upper disc with apertures therein, a spacer, and a lower disc with apertures therein, said upper disc, lower disc and spacer being removable, each collimator being defined by one of said apertures in said lower disc and one of said apertures in said upper disc.

Claim 4

An instrument as claimed in claim 1 wherein substantially the entire instrument, except for the detector, is made of plastic.

Claim 7

The method as claimed in claim 4 wherein the absorber is disposed on the inlet port of the collimator.

Claim 8

The method as claimed in claim 4 wherein the absorber is disposed on the outlet port of the collimator.

Claim 9

A method as claimed in claim 4 further comprising providing an enhancing means for enhancing the energy difference between the radium A and radium C' particles passing through the absorber.

Claim 10

The method as claimed in claim 7 wherein the enhancing means provided is the absorber.

Claim 11

The method as claimed in claim 4 wherein the means for reading the detector comprises an image analysis system adapted to differentiate alpha emitters of different energies by the different size images the respective alpha particles leave on the detector.

Claim 12

The method as claimed in claim 4 wherein the absorber provided is a polycarbonate absorber.

Claim 13

The method as claimed in claim 4 wherein the thickness of the absorber is selected such that alpha particles from uranium dust cannot be registered by the detector.

Claim 14

The method of claim 4 wherein the collimator provided is composed of a plastic material so that it is disposable.

Claim 15

The method of claim 4 further comprising: providing an inner cap retaining the detector and the absorber; providing an externally-threaded outer cap contacting and retaining the inner cap and threaded to an internally-threaded case, which is also provided; providing an inlet aperture in the case, disposed longitudinally between the filter and the detector, for enabling entry of air to be sampled into the instrument provided; providing a filter support contacting and supporting the filter; providing an exit port in the case located downstream of the filter for the exit of sampled air.

Claim 16

A method as claimed in claim 4 wherein seven collimators are provided.

Claim 17

A method as claimed in claim 14 wherein the collimators are provided such that the sum of the cross-sectional area of the bores of the collimators equals between 0.26 cm 2 to 0.30 cm 2 and wherein the length of each collimator provided equals between 0.45 cm to 0.54 cm and wherein the distance between the filter and the end of each collimator closest to the filter is between 0.18 cm and 0.22 cm.

Claim 18

The method of claim 15 wherein the total detection area provided is between 0.25 cm 2 and 0.31 cm 2 .

Claim 19

An instrument for selectively detecting alpha particles emitted simultaneously by radium A and radium C', which are derived from radon, comprising: means for sampling air through a filter which retains alpha-emitting aerosols; a detector in which the alpha particles corresponding to the respective energies of the alpha emissions of radium A and radium C' are selectively detected; at least two collimators positioned between the filter and the detector such that said collimators direct the alpha radiation from the aerosols collected by said filter to said detector, each collimator having an inlet port at the end nearest to the filter and an exit port at the end nearest to the detector, with each collimator designed to perform the same function; an absorber disposed between the detector and the exit ports of the collimators, the absorber having a uniform thickness and being adapted to enhance the energy difference between radium A and radium C' particles; and including means for reading the detector comprising a computer controlled image analysis system adapted to differentiate alpha emitters of different energies by the different size images the respective alpha particles leave on the detector; said detector and said collimators comprising a detecting head, the detecting head being composed of a plastic material and being removable so that it is disposable; said instrument further comprising an inner cap retaining the detector and the absorber, an externally-threaded outer cap containing and retaining the inner cap and threaded to an internally-threaded case, an inlet aperture in the case disposed longitudinally between said filter and the detector for enabling entry of air to be sampled into the instrument, a filter support contacting and supporting the filter, an exit port located downstream of the filter for exit of sampled air; said instrument being further adapted such that the sum of the area of the bores of the collimators equal 0.28 cm 2 plus or minus 10 percent and the length of each collimator equals 0.492 cm plus or minus 10 percent, with the distance between the filter and the end of each collimator closest to the filter being 0.2 cm, plus or minus 10 percent.

Claim 20

An instrument for selectively detecting alpha particles emitted simultaneously by radium A and radium C', which are derived from radon, comprising: means for sampling air through a filter which retains alpha-emitting aerosols; a detector in which the alpha particles corresponding to the respective energies of the alpha emissions of radium A and radium C' are selectively detected; at least two collimators positioned between the filter and the detector such that said collimators direct the alpha radiation from the aerosols collected by said filter to said detector, each collimator having an inlet port at the end nearest to the filter and an exit port at the end nearest to the detector, with each collimator designed to perform the same function; an absorber disposed between the detector and the exit ports of the collimators, the absorber having a uniform thickness and being adapted to enhance the energy difference between radium A and radium C' particles; and including means for reading the detector comprising a computer controlled image analysis system adapted to differentiate alpha emitters of different energies by the different size images the respective alpha particles leave on the detector; said detector and said collimators comprising a detecting head, the detecting head being composed of a plastic material and being removable so that it is disposable; said instrument further comprising an inner cap retaining the detector and the absorber, an externally-threaded outer cap containing and retaining the inner cap and threaded to an internally-threaded case, an inlet aperture in the case disposed longitudinally between said filter and the detector for enabling entry of air to be sampled into the instrument, a filter support contacting and supporting the filter, an exit port located downstream of the filter for exit of sampled air; said instrument being further adapted such that the sum of the area of the bores of the collimators equal 0.28 cm 2 plus or minus 10 percent and the length of each collimator equals 0.492 cm plus or minus 10 percent, with the distance between the filter and the end of each collimator closest to the filter being 0.2 cm, plus or minus 10 percent.

Claim 23

A method according to claim 18 further comprising the step of enhancing the energy difference between RaA and RaC' particles using an absorber and wherein the step of detecting the particles comprises detecting the particles by the different size images the respective alpha particles leave on the detector using an image analysis system wherein measurements of track diameter are automatically carried out by a standard means.

Claim 24

The method of claim 19 wherein the collimators provided comprise a plurality of spacers and discs with apertures therein, said spacers and discs being of various thicknesses and being removable such that the detecting geometry may be flexibly changed.

Claim 25

The method of claim 20 wherein the collimators provided are composed of a plastic material such that it is disposable.

Claim 26

The method of claim 21 further providing for reading said detector, performing an indirect image diameter determination using area measurement of the images on the detector.

Claim 27

The method of claim 18 further providing for reading said detector, performing an indirect image diameter measurement using area measurement of the images on the detector.

Claim 28

The method of claim 23 wherein the means provided for reading said detector comprises defining the areas of the detector screened off by the solid parts of the collimator, which areas comprise the non-exposed background area, and subtracting the track density figure for this area from the track density figure of the exposed area, resulting in greater accuracy.

Claim 29

The method as claimed in claim 18 wherein the collimator includes an absorber formed of a mylar.

Claim 30

An instrument for selectively detecting alpha particles wherein said instrument comprises in combination: a device for sampling air through a filter which retains alpha-emitting aerosols; a detector in which the alpha particles corresponding to the respective energies of the alpha emissions of radium A and radium C' are selectively detected; at least two collimators placed between the filter and the detector such that said collimators direct the alpha radiation from the aerosols collected by said filter to said detector and the area of said detector exposed at each collimator is effectively used for detecting both radium A and radium C'.

Claim 31

An instrument for selectively detecting alpha particles wherein said instrument comprises in combination: a device for sampling air through a filter which retains alpha-emitting aerosols; a detector in which the alpha particles corresponding to the respective energies of the alpha emissions of radium A and radium C' are selectively detected; at least two collimators placed between the filter and the detector such that said collimators direct the alpha radiation from the aerosols collected by said filter to said detector and the area of said detector exposed at each collimator is effectively used for detecting both radium A and radium C'.

Claim 32

An instrument as claimed in claim 26 further comprising a means for reading the detector, said means adapted to differentiate the alpha particles emitted from radium A and radium C'.

Claim 33

An instrument as claimed in claim 27 wherein the means for reading the detector comprises an image analysis system adapted to differentiate alpha emitters of different energies by the different size images the respective alpha particles leave on the detector.

Claim 34

An instrument as claimed in claim 28 wherein the means provided for reading the detector further comprises means for performing an indirect image diameter determination using area measurement of the images on the detector.

Claim 35

An instrument as claimed in claim 28 wherein the means provided for reading said detector further comprises defining the areas of the detector screened off by solid parts of the collimator, which areas comprise the non-exposed background area, and subtracting the track density figure for this area from the track density figure of the exposed area, resulting in greater accuracy.

Claim 36

An instrument as claimed in claim 26 further comprising an absorber disposed on one of the parts of the collimators, said absorber having a uniform thickness.

Claim 37

An instrument as claimed in claim 31 wherein said absorber possesses such physical properties that it enhances the energy difference between the radium A and radium C' particles passing through the absorber.

Claim 38

An instrument for selectively detecting alpha particles emitted simultaneously by radium A and radium C' which are derived from radon, wherein said instrument comprises in combination: a device for sampling air through a filter which retains alpha-emitting aerosols; a detector in which the alpha particles corresponding to the respective energies of the alpha emission of radium A and of radium C' are selectively detected; at least one collimator placed between the filter and the detector such that said collimators direct the alpha radiation from the aerosols collected by said filter to said detector; an absorber disposed between the detector and exit ports of the collimator, the absorber having a uniform thickness and being adapted to enhance the energy difference between RaA and RaC' particles; wherein the collimators are each designed to perform the same function so that the length of each collimator is decreased while efficiency of the instrument is increased; further comprising means for reading the detector, said means adapted to differentiate the alpha particles emitted from radium A and radium C'; and wherein the means for reading the detector comprises an image analysis system adapted to differentiate alpha emitters of different energies by the different size images the respective alpha particles leave on the detector; and wherein the thickness of the absorber is selected so that alphas from uranium dust cannot be registered by the detector; and wherein the detector and the collimators comprise a detecting head, the detecting head being composed of a plastic material so that it is disposable; wherein the collimators provided comprise a plurality of spacers and discs with apertures therein, said spacers and discs being of various thicknesses and being removable such that the detecting geometry may be flexibly changed.

Claim 39

An instrument for selectively detecting alpha particles emitted simultaneously by radium A and radium C' which are derived from radon, wherein said instrument comprises in combination: a device for sampling air through a filter which retains alpha-emitting aerosols; a detector in which the alpha particles corresponding to the respective energies of the alpha emission of radium A and of radium C' are selectively detected; at least one collimator placed between the filter and the detector such that said collimators direct the alpha radiation from the aerosols collected by said filter to said detector; an absorber disposed between the detector and exit ports of the collimator, the absorber having a uniform thickness and being adapted to enhance the energy difference between RaA and RaC' particles; wherein the collimators are each designed to perform the same function so that the length of each collimator is decreased while efficiency of the instrument is increased; further comprising means for reading the detector, said means adapted to differentiate the alpha particles emitted from radium A and radium C'; and wherein the means for reading the detector comprises an image analysis system adapted to differentiate alpha emitters of different energies by the different size images the respective alpha particles leave on the detector; and wherein the thickness of the absorber is selected so that alphas from uranium dust cannot be registered by the detector; and wherein the detector and the collimators comprise a detecting head, the detecting head being composed of a plastic material so that it is disposable; wherein the collimators provided comprise a plurality of spacers and discs with apertures therein, said spacers and discs being of various thicknesses and being removable such that the detecting geometry may be flexibly changed.

Claim 40

An instrument for selectively detecting alpha emissions of radiums A and radium C' comprising: means for sampling air through a filter which retains alpha-emitting aerosols; a plurality of collimators each having an inlet port an an outlet port, with the inlet ports of said collimator being located adjacent to said filter such that alpha particles emitted by aerosols retained by said filter are directed to a common detector positioned adjacent the outlet ports of said collimators; an absorber associated with said collimators, said absorber being located intermediate said filter and said detector such that alpha particles emitted by aerosols and directed at said detector pass through said absorber; said absorber differentially reducing the kinetic energy of radium A and radium C' particles in a manner to increase the energy difference between RaA and RaC' particles; said detector being selected such that RaA and RaC' particles which passthrough said absorber are selectively distinguishable by means of area mode image track analysis whereby the net area of said detector exposed at the outlet ports of said collimators is effective for sampling both RaA and RaC'.

Claim 41

An instrument for selectively detecting alpha emissions of radiums A and radium C' comprising: means for sampling air through a filter which retains alpha-emitting aerosols; a plurality of collimators each having an inlet port an an outlet port, with the inlet ports of said collimator being located adjacent to said filter such that alpha particles emitted by aerosols retained by said filter are directed to a common detector positioned adjacent the outlet ports of said collimators; an absorber associated with said collimators, said absorber being located intermediate said filter and said detector such that alpha particles emitted by aerosols and directed at said detector pass through said absorber; said absorber differentially reducing the kinetic energy of radium A and radium C' particles in a manner to increase the energy difference between RaA and RaC' particles; said detector being selected such that RaA and RaC' particles which passthrough said absorber are selectively distinguishable by means of area mode image track analysis whereby the net area of said detector exposed at the outlet ports of said collimators is effective for sampling both RaA and RaC'.

Claim 42

An instrument as claimed in claim 34, wherein said absorber is positioned across the inlet ports of said collimators.

Claim 43

An instrument as claimed in claim 34, wherein said detector is made of CR-39 polycarbonate.

Claim 44

An instrument as claimed in claim 36, wherein said absorber is positioned across the inlet ports of said collimators.

Claim 45

An instrument as claimed in claim 36, wherein said absorber is a polycarbonate film.

Claim 46

An instrument for use in selectively detecting alpha particles comprising: means for sampling air through a filter which retains alpha emitting aerosols; a plurality of collimators each having an inlet port and an outlet port, with the inlet ports located adjacent said filter; a detecting means for sensing and by means of image, analysis distinguishing between radium A and radium C', said detecting means being exposed to radiation leaving through said outlet ports; said plurality of collimators being defined by an upper disc with apertures therein defining said outlet ports, a spacer and a lower disc with apertures therein defining said inlet ports and aligned with the apertures of said upper disc.

Claim 47

An instrument for use in selectively detecting alpha particles comprising: means for sampling air through a filter which retains alpha emitting aerosols; a plurality of collimators each having an inlet port and an outlet port, with the inlet ports located adjacent said filter; a detecting means for sensing and by means of image, analysis distinguishing between radium A and radium C', said detecting means being exposed to radiation leaving through said outlet ports; said plurality of collimators being defined by an upper disc with apertures therein defining said outlet ports, a spacer and a lower disc with apertures therein defining said inlet ports and aligned with the apertures of said upper disc.

Claim 48

A dosimeter assembly for detecting alpha particles comprising: a plurality of collimators each having an inlet port and an outlet port; a filter disposed adjacent said inlet ports through which air is passed and which retains alpha emitting particles contained in the air, said plurality of collimators being positioned to receive radiation emitted from the particles; absorbing means for reducing the kinetic energy of alpha emitting particles which pass through said collimators; and a detecting means associated with said outlet ports for receiving said alpha emitting particles; said plurality of collimators being defined an upper disc having a plurality of apertures therein defining said outlet ports, and a lower disc having a plurality of apertures therein aligned with said apertures of said upper disc and forming said inlet ports.

Claim 49

A dosimeter assembly for detecting alpha particles comprising: a plurality of collimators each having an inlet port and an outlet port; a filter disposed adjacent said inlet ports through which air is passed and which retains alpha emitting particles contained in the air, said plurality of collimators being positioned to receive radiation emitted from the particles; absorbing means for reducing the kinetic energy of alpha emitting particles which pass through said collimators; and a detecting means associated with said outlet ports for receiving said alpha emitting particles; said plurality of collimators being defined an upper disc having a plurality of apertures therein defining said outlet ports, and a lower disc having a plurality of apertures therein aligned with said apertures of said upper disc and forming said inlet ports.