I recently got e-mail from Sweden asking for a copy of my 1996 millidegree thermostat paper (which he got).
The guy was thinking about setting up a well-thermostatted voltage reference, which got me thinking about national standards lab approach, which depends on long string of Josephson junctions immersed in liquid helium and an RF field of precisely the right frequency.
Since high-temperature super-conductors showed up, I've been wondering whether Josephson junctions between higher high temperature super-conducting elements would work as well.
Google picked up a 2016 Russian paper reporting results on 80 and 81 elements strings, which did the right thing when immersed in liquid nitrogen but not all that well.
It also picked up a 2019 paper that suggested that they'd raised their game and had started selling a commercial package which was stable to one part in 10^8.
Anybody know anything about it?
Bill Sloman, Sydney