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planchet|ˈplɑːnʃɛt, -æ-|
[dim. of planch n.: see -et1 and cf. next.]
1. The plain disk of metal of which a coin is made; a coin-blank.
1611Cotgr., Flanc,..a coping, planchet, or plate of mettall readie to be stamped on, or coyned. 1794P. Wakefield Mental Improv. (1801) I. 136 To cut out as many planchets or circular pieces of metal. 1879H. Phillips Notes on Coins 8 In many instances the coin contained only a portion of the device, the rest having failed to reach the planchet.
2. A small board used in brick-making: = pallet n.3 3 b.
1764Croker, etc. Dict. Arts s.v. Brick-making, A planchet, or small board, used by the person who carries the bricks or tiles from the moulder to the drying beds.
3. |ˈplæntʃɪt|. Physics. Also planchette. A small, shallow dish used to contain a specimen when its radioactivity is measured.
1951Jrnl. Inst. Electr. Engineers XCVIII. ii. 236/1 With end-window counters it is usual to carry the specimen as a powder, or liquid evaporated to dryness, on a suitable holder. J. L. Putman investigated the form of surface necessary to give a uniform response when using the G.M.2 counter-tube wherever the material was deposited on that surface. It was found that these surfaces were of approximately spherical shape, in a position concave towards the window. As a result of this work, a standard planchette, made of pressed nickel sheet, was designed to be used at a distance of 3 mm from the window. 1960Nature 14 May 563/2 Synthesis of deoxyribonucleic acid was measured by counting the total radioactivity of washed cells on planchettes. 1961G. R. Choppin Exper. Nucl. Chem. iv. 51 In case of reuse, each planchet should be carefully checked for residual activity. 1975Nature 3 July 35/2 Radioactivity on the filter and in the frozen water vapour in the cold finger trap (after drying down on planchets) was assayed using a Nuclear Chicago gas flow counter. |