Introduction to the R5 Baseline Test [UPDATE #1 - R5 Now Vacuuming]

You may have noticed  the addition of the R5 Baseline Test; it’s been around for a while now and probably time I explain its purpose.

R5 is a general 40nm Ni cell with no bells or whistles; it lingers partially loaded with a working passthrough core and a high-capacity pressure transducer. This workhorse reactor belongs to a time when we did many powder tests in tandem, none with triggering mechanisms. That was just before the Celani replication effort. We're now lending this reactor for study with the same principle: no triggering mechanism, just hydrogen loading. We’ll even live on the wild side and turn off the passive heating band every once in awhile, just to watch for anything of interest.

The real purpose here is to observe H loading/unloading and its effect on a nearly-fluidized bed of Ni powder. We’ll give meticulous attention to subtle differences in thermal coupling with pressure, rates of pressure change due to loading at different temperatures, and of course reduction in resistance from loaded powder, among other things outlined in the info doc.

With the addition of this experiment comes yet another “test.” The Vacuum Tower test is where we’ll monitor all the cell’s usual parameters when baking off with the turbomolecular drag pump. Though this is an integral part of the R5 baseline, the test URL  will also sit dormant until baking off is needed in another protocol. Thus, this data collection will  remain an existing element on the powder computer, though it will go unused from time to time. We didn’t find need for it with the R3 examination because there was no bakeout in the protocol. Otherwise in other powder protocols, inclusion of this step is just business as usual. You’ll notice that this setup has all the usual parameters of powder tests to date with the exception of T_Int. The vacuum tower sense array was limited (for simplicity’s sake) to 1 HUGnet endpoint, meaning we had to pack all the sensors onto one board - including the band heater power parameters. With the current sense wire consuming low voltage space on the board, it left no room for the interior thermocouple - the least important of the 3 cell temps - as it essentially senses gas temperatures in an environment that removes as much gas as possible.

Now for the Protocol. . .

Posted on the R5 Info Doc is this general protocol and brief rationale of the experiment. We’re taking advantage of the lacking variables in the powder media and triggering mechanism to dig deep with analysis.

1. “Check its vitals.” Get the reactor online with HUGnet to establish a starting point for how it’s held up since it was last tended to over 9 months ago. This data will not be used for the analyses planned later in the protocol but simply as a check that it’s in good condition and ready to begin testing.

2. Thorough offgassing of the powder using a 48V power supply and our turbomolecular drag pump (TMD). This step involves increasing the vacuum from the roughing pump, to the TMD, and finally adding 48V to the heating band to bake out hydrogen in the stainless steel cell as well as the powder. This is a lengthy step (1-2 weeks) as we often reach pressures of 1x10^-8 Torr. In that range, gas molecules have quite a large mean free path, and don’t really get sucked out of the cell as much as they just “find” their way out. With a ¼” tube connecting to the vacuum, a molecule finding that gap may take awhile. Good offgassing makes for better loading.

3. Reinstallation onto the reef and H₂ charging at 200 psig. There is no definitive loading temperature at this time as it might be one of the parameters of study. We will, however, keep the cell temperature on the lower side (250-350°C) to reduce stress on the passthrough epoxy seal. When coupled with widely and frequently fluctuating temperatures over a long period of time, the chances of it failing are very real. We will escape that havoc as best as we can. Loading calculations are done roughly using ∆P in the ideal gas law. The volume of the reactor used in this equation takes the rough volume of the powder into consideration to calculate ∆n, the presumed amount of moles adsorbed. These calculations will be made just before the next 200 psig H₂ charge for completeness. Loading/charging will continue until the change in pressure stagnates over long periods of time. We will also calculate the molar ratio of H atoms to Ni powder when we figure the moles hydrogen adsorbed.

4. In-depth analysis of the various parameters discussed. If we’re going to take the time to run a no-trigger test in a research program that is designed to sniff out good triggering mechanisms, we had better make it worth our while! Though we have no SEM images to lend a better visual aid, the roller coaster of loading cycles will still provide an excellent case study to reference current and future experiments with meaningful comparisons.

5. Return to step 2 and repeat! No number of cycles or duration of loading times specified, we’ll play this one by ear and keep the cell trotting along day by day.

Any thoughts, criticisms, adjustments of the protocol (or anything else) are entirely welcomed; actually they're invited. We really want to get this right and find the most vicious criticisms of huge importance to the process. 

Powder Status: I’ve got R5 on the vacuum, though I haven’t started rough pumping. I’ll be drafting the info doc for for the vacuum test and posting that soon along with the update announcing the beginning of our vacuuming.

As always, thanks for reading!

UPDATE #1 - R5 Now Vacuuming

We've had R5 pumped down on the roughing pump since last night and today we'll turn on the TMD and start bakeout to let that sit over a very long weekend.