Ion mobility spectrometer drift chamber

DETAILED DESCRIPTION Therefore it is the object of the invention to improve a drift chamber of the kind mentioned above in such a way that it can be produced as a compact apparatus in a simple, reproducable and reliable manner, that the chamber is absolutely gas-tight with respect to the surrounding atmosphere and that it also functions in mobile use reliably and trouble-free with a long lifetime.
This object is achieved by a drift chamber which consists of a plurality of identical, preferably circular metal ring electrodes made in particular, from steel foil, whereby the metal ring electrodes are separated by rings made from insulating material, preferably from ceramics and exhibiting a z-shaped cross section and the insulating rings are tightly fitted into the z-profile of the metal ring electrodes so that a self-centering stack of alternate metal ring electrodes and insulating rings is formed, whereby the metal ring electrodes and the neighbouring insulating rings are glued or hard or soft soldered along the z-shaped tight fit in a gas-tight manner and whereby high voltage is supplied to the metal ring electrodes via discrete soldered or conductively glued SMD resistors or via resistor structures, which are vapor deposited onto the outer surface of the insulating rings or via a ceramic rod onto which a continuous highly resistive conducting layer is soldered, conductively glued, or contact fit, such that inside the drift chamber a nearly constant electrical field along its axis is formed if the high voltage is applied to the two outermost electrode rings.
In this manner the object is completely achieved.
The self-centering of the ring electrodes permits an assembly of the cell without problems within narrow construction tolerances.
By rigidly linking the rings via glueing or soldering, the cell is reliably gas tight without a separate inner or outer tube and without an uncontrolled change of distances during use because of elastic seals which would change the drift distance, and it is also avoided that either through or out of these elastic seals made principally from polymeric materials unwanted gas traces disturbing the ion detection reach the drift chamber