Development of a high-accuracy quantized-current source with a Skipper-CCD for the recent redefinition of ampere

The Racetrack (WH7X) (Fermilab)

The Racetrack (WH7X)



Discretized current devices has gained extreme importance by the redefinition of the ampere in terms of the elementary charge. Direct ampere metrology became a matter of counting the transit of individual electrons over time. To provide a practical application of the new standard should reach current levels of 1 micro-ampere. This kind of devices do not exist at the moment.
Current approaches are based on single electron sources (SES) that handles single electrons sequentially at approximately 1GHz providing a maximum current of 100 pico ampere. SES does not provide self single electron calibration and they rely on the average DC current or the low frequency current noise while repeating the experiment billions of times. On this talk we present a new device based on Skipper CCD that provides the means for single-counting while pumping increasing the efficiency and accuracy of the process. The magnitude of the output current can be controlled by adjusting the number of charge carriers in the packets, and the timing of the charge transfer operations.  Skipper-CCDs can transport large charge packets (can easily handle 10000 e- per channel) at a rate of 1MHz for a total pumping rate of ~1 nano-ampere per channel with improved accuracy. Moreover, the Skipper CCD runs at 140K (compared to mK regime of SES devices) facilitating the scalability to get to the current levels for the new standard. The talk covers the conceptual design of the device and the first measurements obtained at Fermilab.