Bruker Daltonik Gmbh

Finnigan Mat Gmbh

Horst Rache

Heinz Lerche

Reiner Wedde

In a time-of-flight mass spectrometer, the entire flight tube, which is generally manufactured of stainless steel due to the necessary vacuum characteristics and is subject to a relatively high degree of thermal expansion, together with the spectrometer electronics is enclosed in an electromagnetic shielding box. A flow control mechanism, which can consist of a fan, draws air over the electronics, heating the air. The heated air is then admixed with fresh air and drawn over the flight tube maintaining it very precisely at a constant temperature. In addition, the electronics may also be kept at a constant temperature by a separate air stream guidance and control mechanism.

Method and apparatus for thermally stabilizing flight times in time-of-flight mass spectrometers

For calibrating mass spectrometers with a plurality of ion targets (1), especially Faraday targets, to which a separate measuring channel is assigned in each case, an electric current from a highly stable electrical voltage-source (6) is supplied, as a measurement reference-value, to the individual measuring channels, in chronological succession, via a resistor (R.sub.2) having a high degree of constancy. For this purpose, a control device (7) is provided, which actuates switching devices (K.sub.1 -K.sub.n) in such a manner that the correct chronological sequence is maintained. The calibrating measurement-values, obtained with the aid of this highly stable current, are intercorrelated in order to form a correction-value, this correlating operation being performed in a calibrating-correction unit (5). Several calibrating measurements, with different currents, can be carried out for each measuring channel (V.sub.1 -V.sub.m), and these measurements can also be carried out with the aid of an external, linearly controllable voltage-source, which produces these currents via the resistor (R.sub.2) having a high degree of constancy.

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Delmenhorst, Germany

Horst Rache