Precision measurement of an electron pump at 2 GHz; the frontier of small DC current metrology
S. P. Giblin, Gento Yamahata, Akira Fujiwara, M. Kataoka
Abstract
Abstract A well-characterised sample of silicon tunable-barrier electron pump has been operated at a frequency of 2 GHz using a custom drive waveform, generating a pump current of 320 pA. Precision measurements of the current were made as a function of pump control parameters, using a blind protocol, over a 7 week campaign. The combined standard uncertainty for each <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mo>∼</mml:mo> </mml:mrow> <mml:mn>10</mml:mn> </mml:math> h measurement was in the range <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>0.16</mml:mn> <mml:mo>−</mml:mo> <mml:mn>0.18</mml:mn> </mml:math> parts per million (ppm). The pump current exhibits a plateau along the exit gate voltage flat to approximately 0.15 ppm, but offset from ef by 0.2 ppm. This offset may be a sign of errors in the current traceability chain, indicating a limit to the accuracy of small current scaling using existing methods based on cryogenic current comparators.