Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J47/00—Tubes for determining the presence, intensity, density or energy of radiation or particles
  • H01J47/02—Ionisation chambers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J47/00—Tubes for determining the presence, intensity, density or energy of radiation or particles
  • H01J47/02—Ionisation chambers
  • H01J47/04—Capacitive ionisation chambers, e.g. the electrodes of which are used as electrometers

Definitions

• This invention relates to ionization chambers and especially to ionization instruments of the class of pocket dosimeters, namely pen-type dosimeters, condensermeters and all similar pocket-size monitoring devices which are worn by radiation workers and serve to determine radiation dosages received by such persons.
• the object of the invention is to provide an ionization chamber in which the absorption of 5, 'y and X radiations is in close and well-defined relation to the absorption of said radiations by body tissues so that the biological effect of radiation on the wearer of the instrument may thus be determined, said ionization chamber being insensitive to neutrons.
• the atmosphere of the chamber is constituted by elements having a low thermal-neutron and fast-neutron capture cross-section and excluding hydrogen.
• the easiest solution evidently consists in utilizing air in which the coefficient R of response to ,8, 'y and X radiations with respect to human body tissues (said coeflicient being defined as the ratio of energy absorbed per unit volume in the atmosphere of the ion chamber to the energy absorbed in the body tissues) is 0.92i0.02 (and varies slightly as a function of the energy of the photons).
• the object of this invention is to provide an inonization chamber which meets the above requirements. Accordingly, the invention proposes an inonization chamber in which the gaseous atmosphere employed is air and in which the chamber wall is formed of an alloy of beryllium with at least one of the elements of the group constituted by aluminum, magnesium and silicon, said alloy being of nuclear purity in the elements which have a high atomic number and the proportion of beryllium being such that the coeflicient of response of the wall to 5 radiation and to 'y and X photons is substantially identical with the coefiicient of response of the air.
• Be-Al containing between 1 and 89% by weight of Be
• Be-Mg containing between 77 and by weight of Be
• Be-Si containing between 84 and 92% by weight of Be
• Be-Alpax containing between 81 and 89% by weight of Be.
• the etfect of the addition element or elements is to increase the coefficient of response to photons which, in the case of high-purity beryllium, increases from 0.01 to 0.82 when the energy of the photons received increases, and to stabilize said coeflicient at a mean value in the range of energy which corresponds to hard X-radiations and 'y radiations.
• Alpax is a casting alloy which contains 88.3% aluminum and 11.7% silicon. This alloy has the advantage of being readily melted and therefore facilitates production of beryllium-base alloy.
• the composition of said alloy will be:
• the response coefficient of this alloy is 0.90:0.05.
• Example 4 It is of course possible to mix the alloys hereinabove defined in practicaly all proportions. Among these alloys, the composition given in Example 4 appears to be the most advantageous whilst the alloy of Example 3 appears on the contrary to be the least satisfactory.
• compositions given above only ensure the response coefficient which is indicated on condition that the constituents are of nuclear purity.
• impurities such as, for example, iron, beryllium oxide and the like
• the alloys which have been defined above can be employed for the purpose of forming, for example, the walls of pen-type dosimeters of the type described in section 3.1 of Chapter C VII, vol. 1 of the Cours de Genie Atomique (Nuclear Engineering Course published by the I.N.S.T.N., Saclay, France, 1960;) in this case, the alloys must be fabricated in the form of tubes having an internal diameter of approxmiately one centimeter and a thickness of approximately one millimeter. This fabrication process can be carried out especially by powder metallurgy, recourse being had to conventional methods.
• An ionization chamber in which the gaseous atmosphere employed is air and in which the outer chamber wall is formed of an electrically conductive alloy of beryllium with at least one of the elements selected from the group consisting of aluminum, magnesium and silicon, said alloy being of nuclear purity in elements having a high atomic number and the proportion of beryllium being such that the coeflicient of response per mass unit of the wall alloy to beta radiation and to gamma and X photons is substantially constant and identical with the coefiicient of response of the air and the thickness of said wall being such that its absorption is substantially equal to that of the tissues which protect the crystalline lens of the human eye.
• An ionization chamber in which the gas atmosphere is air and in which the outer chamber wall is formed of an electrically conductive alloy selected from the group consisting of an alloy of beryllium and aluminum containing between 81 and 89% by weight of beryllium, an alloy of beryllium and magensium containing between 77 and 84% by weight of beryllium and an alloy of beryllium and silicon containing between 84 and 92% by weight of beryllium, the thickness of said wall being such that its absorption of beta radiation and of gamma and X-ray photons is substantially equal to that of the tissues which protect the crystalline lens of the human eye.

Landscapes

• Measurement Of Radiation (AREA)
• Medicines Containing Antibodies Or Antigens For Use As Internal Diagnostic Agents (AREA)
• Silicon Compounds (AREA)

Applications Claiming Priority (1)

Publications (1)

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ID=8592649

Family Applications (1)

Country Status (11)

Cited By (1)

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Citations (5)

• 1965
  • 1965-11-16 FR FR38657A patent/FR1481941A/fr not_active Expired
• 1966
  • 1966-10-26 BE BE688875D patent/BE688875A/xx unknown
  • 1966-10-28 GB GB48505/66A patent/GB1123267A/en not_active Expired
  • 1966-11-01 IL IL26783A patent/IL26783A/xx unknown
  • 1966-11-10 LU LU52333D patent/LU52333A1/xx unknown
  • 1966-11-11 CH CH1625366A patent/CH465073A/fr unknown
  • 1966-11-11 DE DE19661539828 patent/DE1539828A1/de active Pending
  • 1966-11-15 SE SE15612/66A patent/SE324411B/xx unknown
  • 1966-11-15 NL NL6616050A patent/NL6616050A/xx unknown
  • 1966-11-16 ES ES333426A patent/ES333426A1/es not_active Expired
• 1969
  • 1969-05-05 US US822060A patent/US3538369A/en not_active Expired - Lifetime

Patent Citations (5)

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