We use Josephson arrays that are driven by very short current pulses to generate ac voltage. These arrays are produced by Work Group 2.43 inside the clean room facility at PTB. A detailed explanation of the Josephson Arbitrary Waveform Synthesizer (JAWS) can be found here.
The experimental JAWS system is based on a pulse generator, which send ternary pulses (-1 / 0 / +1) with a pulse repetition frequency of 15 GHz to the arrays. The chips are located in liquid Helium at a Temperature of 4.2 K (about -269 °C). The JAWS allows us to create arbitrary waveforms in the time and frequency domain, which is of high interest for a wide number of applications.
In August 2014, we achieved an RMS voltage of 1 V (peak-to-peak voltage: 2.845 V), together with Work Group 2.43, by connecting eight arrays with a total of 63,000 junctions in series.
Schematic diagram of a 1 V JAWS system. 4 Josephson-chips with 8 Josephson-arrays are connected in series, but driven in parallel by the pulse generator. A Spectrum-Analyser shows the purity of the output waveform.
Lower end of the Cryoprobe with screen removed. The electrical connections and two boards with Josephson chips are clearly visible.
A 1 V JAWS system and setup. The Cryoprobe is immersed in the Cryostat, control electronics including the pulse generator are to the right.