A standard voltmeter designed for measuring up to ± 2 MV in vacuum was modified to operate at -4 to -6 MV, appropriate levels for measuring the convolute voltage during z-pinch experiments on Z. Field shaping structures are used to eliminate electron emission from the voltmeter grading rings. The voltmeter operated as expected during tests at -4 MV on the Mercury generator, indicating this voltmeter could work for the lower voltage range expected on Z. At -6 MV on Mercury, the voltmeter did not operate correctly, probably because of electron emission. Particle-in-cell modeling is consistent with the observed voltmeter response. An improved field shaper could extend the voltmeter operation to -6 MV.
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