GB689857A - Improvements in apparatus for measuring thickness or weight per unit area by means of ionizing radiations - Google Patents

Abstract

689,857. Radioactive thickness gauges. BALDWIN INSTRUMENT CO., Ltd., and SYKES, G. Jan. 2, 1952 [Dec. 4, 1950], No. 29669/50, Class 40 (iii). In a thickness or density gauge of the type in which radiation from a radioactive source passes through the material under test to an ionization chamber or other detector, both the emitter and detector have associated with them a radiation absorbing device which transmits the radiation with much greater facility in the direction of the detector. Thus, the rays are " collimated " on leaving the source and pass through the test material where some are absorbed and others dispersed. The second absorbing device eliminates all the dispersed rays and the reduction in the radiation reaching the detector is muchincreased. As shown, a source of Alpha, Beta or Gamma rays is deposited in a recess 12 behind a window 15. A wire gauze guard protects the window. The radiation absorbers consist of a number of parallel strips 17 separated by spacers 19 on bolts 18. The rays, after passing through both absorbers and the test material 10, enter a sealed ionization chamber 33 in which is an electrode 23. The connections are made to the electrode and the chamber 33 through pressuretight insulator bushes. The absorbers may consist of bundles of parallel strips, corrugated strips soldered, cemented or clamped together, or parallel tubular channels of rectangular or circular cross-section. Alternatively, a number of parallel strips may be slotted at equal intervals and engaged with a series of strips similarly slotted at right angles. In a modification described with reference to Fig. 8 (not shown), the thickness of a deposit on a strip is determined by means of two gauges of the type described above, one situated before and the other beyond the depositing position. The output of these two gauges are then compared.