Myself and two other students from the Northwest Nuclear Consortium (now incorporated as a 501 (c) (3) called Northwest Nuclear Laboratories) did research on the topic of palladium and fusion during this past school year. As of yet, we haven’t made any solid conclusions of efficacy, but I thought I’d share what we’ve done and found so far.
As has been mentioned in other posts, beam-target reactions make up a large portion of total number of fusion, and as more deuterium is embedded in chamber walls, the amount of fusion events goes up. Due to cost, our first research done in to metals that can absorb hydrogen tested titanium, which can absorb roughly 20x it’s volume in deuterium. It was shown that there was a 30% increase in neutron output when titanium was added to the chamber. Research done at the University of Wisconsin-Madison corroborates this (http://iec.neep.wisc.edu/usjapan/9th-US ... /Rusch.pdf
). The material best able to absorb deuterium is palladium, which is capable of absorbing 900x it’s volume in deuterium.
In order to create a palladium target while keeping a reasonable budget, we widened two 5 gram ingots on an anvil to a surface area of roughly 1.5 square inches. A property of palladium that we found in background research is that once a temperature of 80 celsius is reached, it’s deuterium absorption ability increases markedly. Our reactor has a water cooling system which makes it impossible to reach the temperature at which absorption starts in earnest, so that the shield’s main component, borated paraffin, doesn’t melt. Melting the shield is frowned upon. To get around this, we designed and implemented a device into our fusor that acted to thermally isolate the palladium sample from the cooling system.
On the conflats that are inline with plasma, there were existing holes used to mount titanium for experimentation, which we took advantage of these holes when constructing the isolator. In these holes, we inserted threaded rods which were used to mount ceramic standoffs. To these standoffs, we mounted a stainless steel disc, and to the disc we mounted the palladium. The palladium was moderately convex and was attached in such a way that there was maximum contact. Palladium has similar thermal expansion to steel, so we expected relatively good thermal coupling. We intended for the palladium to be heated by the plasma’s thermal load.
In actuality, there was an issue with the thermal coupling of the palladium. While there was little thermal expansion, deuterium absorption caused enough expansion for the sample to bow away from the steel plate and only be coupled by the two mounting screws. This caused a runaway effect, where the palladium heated much more rapidly than the rest of the device. We came to the conclusion that the palladium was getting so hot that it was evaporating and being ionized by the beam. Heavy ions in the plasma cause elevated current draw, which could result in premature breakdown of diodes in the Cockcroft Walton. That’s bad.
As shown in the attached data, there was a drop of nearly 50% in neutrons. These numbers don’t represent isotropic emission, just what the detector saw. We are at the moment attributing the stark decrease in neutrons to the presence of palladium ions in the plasma, draining much of the energy that would be going to fusion. We don’t think that these figures show that palladium won’t work, and when we do more research with different conditions that we may very well get an increase in neutron flux. We’re looking into using vapor deposition to get near perfect thermal coupling as an alternative method of introducing palladium.
I’m happy to address any questions or concerns,