Physics:Time expansion chamber

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First proposed by Walenta(Walenta79b, Walenta82), the time expansion chamber is a special type of time projection chamber ( Hepb img54.gif Drift Chamber), with its drift volume arranged to achieve higher precision: the drift volume is separated into two distinct parts, a drift region of relatively low electric field, with consequently reduced drift velocity, and a higher-field amplification region close to the wire, which is necessary to obtain a high enough signal. In practice, this separation is achieved by inserting a grid of defined potential between the drift region and the sense wires; the sketch of principle ( Hepb img54.gif Drift Chamber) is the same for a time expansion chamber, but the function of the grid is different.

Drift velocities in the time expansion chamber are reduced typically by one order of magnitude, and resolutions of Hepb img612.gif   Hepb img204.gif have been reported (Anderhub88).