High-Voltage Measurement and Calibration

So far we have disregarded the excellent internal velodty calibration which is provided by the transition or the laser frequency. It can be helpful for precision spectroscopy experiments, but also used to calibrate voltages beyond a few keV with unprecedented accuracy. Voltages up to a few hundred keV are measured by compensated dividers, consisting of wire resistors, with relative uncertainties down to 3 x 10. Commercial instruments reach the 1 x 10 level. 

In this context there have been two approaches of absolute beam energy measurement, (i) by accurate measurements of the Doppler-shifted resonance frequencies (or wavelengths) with parallel and antiparallel beams, and (ii) by using two-photon interactions of a three-level system in counterpropa-gating laser fields. As atomic masses are known very precisely, we do not differentiate between velocity and kinetic energy. 

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