GB718408A - Improvements in or relating to measuring chambers for x-rays - Google Patents

Abstract

718,408. Discharge apparatus. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Aug. 6, 1952 [Aug. 9, 1951], No. 19793/52. Class 39(1) A measuring chamber for X-ray radiation comprising a gas filled ionization space provided between two parallel walls of insulating material. which walls, on their opposing surfaces, are each coated with a conductive layer constituting an electrode, and an entrance window through which the X-ray radiation may enter the ionization space, which window is constituted by part of one of said walls, the effective atomic number of the conductive layers being lower than that of the gas filling, is characterized in that the electrodes are spaced apart by about 1 mm. and the entrance window has such thickness that the sensitivity of the measuring chamber is substantially independent of the wavelength of the X-rays at least throughout a range of wavelengths having a halving thickness between 0.04 mm. and 1.5 mm. Al. The so-called " flat " measuring chamber shown comprises an inner case 1 and an outer case 2 separated by a narrow intermediate space 3 filled with a conductive layer 4 of carbon, for example graphite, enclosing a conductor 5. A central bore 6 of the inner case 1 is also coated with a conducting carbon layer 7 which encloses a conductor 8. A recess 9 formed in the end of the inner case 1 has a depth of about 1 mm. and a diameter of about 10 mm. and is coated at the bottom with a carbon layer 10 which is in contact with the carbon layer 7 and hence with the conductor 8. The recess 9 is filled with air and is covered with a wall 11 having a thickness of from 0.2 to 0.5 mm. and is coated with a carbon layer 12 which is in contact with the carbon laver 4 and hence with the conductor 5. The wall 11 and the inner and outer cases 1 and 2 are made of insulating material preferably having about the same absorption coefficient for X-rays as the conductive coating, polystyrol being suitable.