Monitor Spectrometer

Huge precision "voltmeter" using the former Mainz spectrometer setup.
KATRIN monitor spectrometer

The monitor spectrometer is used to monitor the stability of the high voltage of the main spectrometer. Like the main spectrometer, it is operated as a MAC-E-Filter. It measures the energy of conversion electrons from the Krypton-83m decay, which have always the same energy. Basically it is an almost 10m long, very accurate voltmeter, using a nuclear standard as a reference. 

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