GB740374A - Radiation detector - Google Patents

Abstract

740,374. Electric measuring instruments; thermocouples. DISTILLERS CO., Ltd. Jan. 1, 1954 [Jan. 16, 1953], No. 1296/53. Classes 37 and 53. [Also in Group XL (b)] A radiation detector is made in the form of a moving-coil instrument, and comprises a frame of slightly diamagnetic material supporting a loop consisting of two wires joined at opposite ends to form two thermocouples each thermally connected to a lamina of radiation-absorbing material the frame being mounted between the poles of a magnet so as to permit axial rotation. As shown, Fig. 1, a rigid brass structure positioned between the poles 2, 3 of a magnet carries a quartz frame 4 by means of suspension fibres 6, 7 which may be of gold strip or quartz fibre. The frame should be of a diamagnetic material which, with a para-magnetic loop, forms an arrangement of zero susceptibility. The quartz frame supports a loop of wire by means of rigid quartz fibres 11, attached to opposite sides of the frame. The loop is formed of two wires 12, 13, one of a palladium/gold and the other a platinum/iridium alloy. At the junctions of the wires are discs 17 of radiation-absorbing material such as gold foil covered with gold black. The main frame 1 is provided with a torsion head 9. Inequality of temperature of the two junctions produces a current in the loop, which with its quartz frame is then deflected in the magnetic field. In the arrangement of Fig. 5 (not shown) the quartz frame carries an additional coil of wire which is fed with the amplified output of a photo-electric cell receiving light reflected by a mirror also mounted on the quartz frame. The current in this coil restores the quartz frame to its zero position and the photo-cell output is measured or recorded. The application of the invention to radiation gas analysers of known type is described. In the arrangement of Fig. 2 (not shown) in which a pair of beams, one having moved through a test cell and the other a comparison cell are compared each beam is direoted to one of the junctions. The beams are concentrated on to the junction by funnels, the interiors of which are coated with a reflecting film. In a modification (Fig. 3, not shown) two of the cells containing gas are shaped as funnels. In the arrangement of Fig. 3 (not shown) wherein two beams are " chopped " alternately, the beams are divided sequentially on to a single junction, the other junction being used for comparison purposes only. Alternatively a part of the radiation from the source may be directed on to it to eliminate errors due to changes in source intensity. Specifications 683,952 and 703,241, [both in Group XL (b)], are referred to.