GB699845A - Beam therapy apparatus - Google Patents

Abstract

699,845. Therapeutic radiation apparatus. ELDORADO MINING & REFINING (1944), Ltd. March 10, 1952 [March 8, 1951], No. 6180/52. Class 98 (i). [Also in Group VI] The apparatus includes a radio-active source of high energy γ-rays enclosed by a container impervious to γ-rays having an outlet for the emission of a beam, wherein the beam is controlled by apparatus comprising gravity operated means for supplying mercury to close the outlet, means for removing the mercury from the outlet by displacing it to a higher level by means of a compressed gas, means comprising said compressed gas for keeping the mercury out of the outlet, means for releasing the compressed gas from the outlet whereby the mercury will pass into the outlet, and means pervious to γ-rays to prevent the mercury from escaping through the open end of the outlet. As shown, a γ-ray source 10, such as Co<SP>60</SP>, is enclosed by a container 11 of dense material such as lead, and has a conical outlet 14. A sloping window 16 closes the outlet, which can be filled with mercury. A safety window 17 may also be fitted, both windows being of material pervious to γ-rays, such as stainless steel. The mercury may be removed by compressed air, which is blown in by a pipe 28 branching at 29, 30 and so forcing the mercury up pipes 19 (only one of which is shown) into a reservoir 21. A sump 23 is provided, from which pipes 19 branch on either side, the arrangement being such that a mercury seal prevents air from entering pipes 19. Reservoir 21 is crescent shaped, and is of such a size that when the mercury is forced into it, the air therein is compressed and helps to return the mercury when pressure is released. The floor 24 of reservoir 21 is parallel to window 16, and the pipes 19, 28, 29, 30 make angles with the base of the container lying between the angles made with the base by window 16 and the side 18 of outlet 14. By this means, the container can be tilted between a position in which window 16 is horizontal and a position in which the side 18 is horizontal without impairing the working of the device. To open the radiation path, a switch is closed in an electric circuit which starts a compressor, which blows air down pipes 28, 29, 30 and closes a solenoid valve. A pressure-sensitive switch connected to reservoir 21 breaks the circuit to the compressor when all the mercury has been forced out of the outlet 14. Should pressure fall due to leakage, allowing mercury to return, the pressure switch re-starts the compressor until the mercury has been forced out again. When the operating switch is opened, the solenoid valve opens to let out the air in outlet 14 and the mercury returns. A hand-operated valve may be connected to release the pressure if the solenoid-operated valve should stick. The failure of any other part of the system results in an immediate return of the mercury to outlet 14, thus cutting off the radiation.