Patent GB-876481-A (GB)
Title: Improvements in combined precipitation chamber and counter units
Inventor: HARLEN FRANK
IPC: G21C17/04
Filed: 1956-08-22
Abstract: 876,481. Scintillation counters. DOWTY NUCLEONICS Ltd. Nov. 22, 1957 [Aug. 22, 1956; July 18, 1957], Nos. 36489/57 and 22751/57. Divided out of 25601/56. Class 40(3) [Also in Group XL(a) ] In a precipitator and counter apparatus comprising an electrostatic precipitation chamber arranged adjacent to a scintillation or other counter and a long wire or other elongated conductor mounted on drums or pulleys for intermittent passage through the precipitator and counter, a component which in use substantially completely encloses a length of the wire or other elongated conductor is adapted for transverse insertion therein of the wire or other elongated conductor, thus reducing the time during which the apparatus is out of action owing to a broken wire or conductor. The apparatus shown comprises a precipitation chamber 7 and a scintillation counter enclosed in a pressure casing having flanged lower and upper portions 1 and 2 secured together by nuts screwed on to studs 5, and sealed by a pair of rubber rings 6. The scintillation counter comprises a slotted phosphor 9 located within a block 12 of transparent synthetic resin forming a light guide which directs light emitted by the phosphor to a combined photo-cell and electron multiplier 13 mounted in a cylindrical container 14 located in a bore 11 in an iron shielding block 8. The light guide 12 is slotted at 10, and seals 15 prevent leakage of pressurized, gas from the casing into the cylinder 14. A lead plug 16 forms an additional shield for the phosphor 9. A slot in the chamber 7 is closed by removable inserts 17, and a slot in the shielding 8 is closed by plates 19 and 21 bolted to the upper portion 2 of the casing, to which is also bolted a cylindrical plug 22 closing the bore 11. A wire 28 is wound in the form of an endless loop around four drums, two of which (24 and 27) are shown, and has a central run which passes through the centre of the chamber 7, the shielding 8 and the phosphor 9. Drum 24 is fixed to a shaft 32 which passes through the casing to an intermittent drive mechanism, a sealing device 33 preventing the escape of gas. The spindle of drum 27 is carried on a pivoted arm 38 which is acted on by a compression spring 41 to tension the wire. A contact 42 operates an alarm if the wire breaks. To replace a broken wire the upper portion 2 of the casing is removed by means of lifting eyes 23, carrying with it the plates 19 and 21 the the plug 22. The inserts 17 in the slot in the chamber 7 are then removed, and the four drums removed by undoing a lock-nut at the top of each spindle. A jig carrying four replacement drums wound with wire is then lowered on to the apparatus, one run of the wire passing through the slots in the chamber 7, shielding 8 and phosphor 9 to the operating position. An alternative arrangement is described (Figs. 7-10, not shown) in which the drums on which the wire is wound form part of a sub-assembly removable and replaceable as a whole in the unit. An intermittent pneumatic drive is employed in this arrangement.