Temperature Controller for the Josephson Arbitrary Waveform Synthesizer

This paper presents a cryocooled Josephson arbitrary waveform synthesizer (JAWS) developed at the National Institute of Metrology (NIM), China. A 2-volt Josephson junction chip is mounted on the second stage cold head of a cryostat. We develop a temperature controller to measure the output voltage of the temperature sensor, and control the temperature of the second-stage cold head. The controller is composed of a current source of high stability, relays, a preamplifier, a low pass filter and a 24-bit analog to digital converter, and a microcontroller unit. Preliminary results show that the cooling power at 4.2 K is about 279 mW and the temperature fluctuation is within 40 mK.