Actually, there's no reason I can't make a mechanical connection, but I was hoping to avoid that complexity. Also, I was concerned that physical separation of the mechanical contact might occur as the whole structure was dipped into the liquid helium, and the parts shrink. If the contact was under pressure, via spring loading, the spring would have to be above the liquid helium, with beams going down into the dewar to transmit the mechanical force, as I assume a metal spring would lose its tension in liquid helium.
Your mention of being able to bond aluminum to NbTi might be the ticket. A "bonder" just uses a very large current pulse to bond two pieces of metal, and my apparatus does just that - provide a very large current pulse. In the past I've accidentally bonded a steel screwdriver to aluminum rails. It actually made a pretty good bond, requiring a lot of mechanical force to separate it. But that makes me wonder is there something special about aluminum that it can be bonded to NbTi, and other metals can't be bonded to NbTi? I see that aluminum is in a different part of the periodic table than Nb or Ti, the latter two being in the same section of the periodic table.
I read about the toxicity of niobium, and it sounded scary - liver and kidney damage if ingested, or breathed in. So I wanted to do the minimum of mechanical processing, to avoid contamination of my workplace with the shavings and dust. I thought about drilling and tapping the ends of the rod, something I've done many times before on other projects with more convention metals - steel, aluminum, but it would contaminate my drill press area.
Of course if I used a high voltage discharge for bonding to the NbTi it would probably produce a small amount of niobium vapor. But I could do that outdoors, as my system is battery powered, with a 12 volt lantern cell.
Funny, I didn't even think of using silver epoxy to bond wires to the ends of the NbTi rod. I used silver epoxy once on a YBCO, 1 inch disc, but it ruined the superconducting characteristics of the disc. However, I let it cure outdoors on a dock, near my workroom, in a humid marine environment, so moisture may have penetrated the YBCO, altering its chemical properties. I was always careful to keep my YBCO discs in a plastic container with lots of desiccant bags to soak up any moisture. But, recently, the owner of Superconductor.org, told me that he uses silver epoxy all the time to bond wires to the ceramic superconductors. He told me that he cures his samples in an oven at 200 degrees for 20 minutes. So, I may abandon efforts to work with Niobium alloys and just go back to YBCO discs, which are readily available to hobbyists.
As to what I am trying to measure, that gets into pseudoscience. A materials scientist, named Evgeny Podkletnov, claimed that he detected brief acceleration pulses (1/10,000th of a second), as large as 1000 g's, from a YBCO superconductor subjected to 2 million volt discharges. Another group, led by Martin Tajmar, at the Austrian Research Center (ARC) reported small (100 micro-g) acceleration signals when rapidly spinning up a small niobium ring inside a liquid helium cryostat. The outer part of the ring was subjected to only 7.68 g's maximum. So, I thought maybe acceleration of the condensate inside these superconductors is what leads to acceleration signals. I also wondered since niobium has 10 times the cooper-pair density as YBCO whether it might enhance such 'signals', perhaps in a direct proportional manner. Hence the desire to use niobium or its alloys. NASA checked into this a long time ago. But, when I read their report, it seemed like they just used a perfectly stationary YBCO disc, about a foot in diameter, and looked for a diminuation of gravity above it with possibly the world's most sensitive gravitometer. They found nothing. The ARC group later retracted their claim. So, admittedly, this is all on rather shaky ground. But, I thought, if the degree of acceleration of the condensate was perhaps directly proportional to the 'signal', then I could greatly improve on the ARC teams magnitude of acceleration by the high voltage method. I'm assuming the cooper pairs would undergo a brief acceleration spurt much larger than 7.68 g's when subjected to 600 volts.
