Originally posted by humy
Apparently there has been a significant advance in the field of spintronics just a few days ago with the “first ever direct mapping of the formation of a persistent spin helix in a semiconductor” ( see link below ) .
But what the hell IS a “spin helix”? I have never heard of this term before and I tried googling it but got nowhere. The link I have about the b lf liquid cooling system is unlikely to achieve in commercial devices.
I am surprised it works even at 40 K. I work with cryogenics all the time, my cryo pumps internally get down to 10-13 degrees Kelvin all the time, they have to to trap gasses on an activated carbon christmas tree like structure, where gasses check in but they don't check out so there is a constant flow of gas in a vacuum system hitting the cold head which means the vacuum gets better and better all the time till there is equilibrium between either physical leaks or virtual leaks, the latter being places say, inside surface roughness of metals, atmospheric gasses or humidity hides out and slowly escapes. That latter can be dealt with by zapping the inside surfaces with UV but we don't go to that extant, just happy getting a pressure close to 1E-8 torr range.
So there are ways of getting down to that temperature but it takes a cryo-compressor and the mechanism of the cold head which includes a piston moving up and down slowly, compared to a motor, one cycle roughly every second.
The cryo compressor itself consumes a couple thousand watts so the resulting system had better be extremely powerful as a computer to justify that much power expenditure at least at this stage of development of such systems.
The actual cooling power of the cold head is only about 1 percent efficient, I don't know why, well it has to due with the amount of energy it takes to pump helium into the cold head, the flow it takes, but the actual wattage rating of the cold head is only a few watts, maybe ten watts max but the equipment to cool it down to low kelvin numbers consumes thousands of watts, not a great percentage. If they can get that down to the level of efficiency of a modern household refrigerator they might have something commercial but till then, they better have an extremely powerful computer as the result of spintronics before it comes out of the labs.
The cooling gas, btw, for such cyro pumps is helium. We have to go to great engineering lengths just to keep the stuff from leaking away and we do a great job of that in the cryo pump compressor.