I do. I’m not sure why, but I get an odd amount of enjoyment of plotting data out and seeing different relationships displayed graphically. I know, I know, there’s no hope for me. I’m reminded of the Simpson’s episode where Homer has suddenly become smart (I believe from having a crayon removed from his brain) and is finding himself rather sad. Lisa mentions that happiness and intelligence are often inversely correlated and says, “sigh... look, I made a graph of it.”

Anyhow, here’s one of my latest little ones :

During our experiments it’s often necessary to keep track of the temperature accurately. However, it’s often quite difficult to get the conventional temperature measurement device, the ubiquitous thermocouple, to function in our system (usually it’s just impossible to use due to my heavy reliance on RF induction heating). However, we still need an accurate way to determine the temperature both for our results and also so that we don’t melt the crystals.

One of our standard tricks is to us the common piece of knowledge that (most) things expand when heated. Now, we can’t put calipers inside our chamber or do anything like actually measuring the size difference of these little crystals in the normal sense. However, because we’re so often doing x-ray scattering experiments, we are able to clearly determine the average distance between the individual atoms in the crystals. As the temperature increases we are capable of seeing the distance between the atoms change by a very tiny amount. The relation between that expansion and temperature is well known.

So we just measure those distances periodically and convert them to temperature. Now, it takes a little time to do that and time is a precious quantity at a light source. So we do it only when needed/reasonably possible and then interpolate for places in between. Above is that interpolation. The blue points are the measured vales along with the accompanying experimental uncertainty in each point. A red line is then fit to those data points (I excluded the room temperature-0 power data point as it looks like a non-linear jump in temperature from the heater just being turned on at its lowest power setting). So now you can get the temperature for any power seeing to within a very reasonable accuracy. We have to do that each time we change samples or even whenever there’s a large change in the sample position relative to the heating coils, but that’s the price we pay. The accuracy is much, much higher than the other temperature measurement device easily available, a pyrometer (which determines the temperature from the light being emitted by the glowing crystal).

For my recent experiments I had to put together the little x-ray scattering vacuum chamber again. The last time we used it there didn’t seem to be anything special about its appearance. However, this time there seemed something quite peculiar as I put things together. It looked very similar to an elephant or an insect.

Here I’ve removed the long hose from the front “snout,” but the effect is still there. The two largest ports where the x-rays come in and go out (which above are glass, but replaced by Beryllium windows) make the eyes. It’s got ears and a nose, along with a couple of dangling arms/appendages. In truth it really was not intended to look like something else. It’s a surface scattering chamber complete with vacuum hardware and measurement pieces, an RF induction heating system, rotating sample stage feedthrough, fine-adjust gas flow leak-valves, burst-disk, and enough windows that I can see the sample positions during the experiment.

One of my friends took one look at it and said, “Ganesh!” The name stuck. So we have a vacuum chamber named after a Hindu deity. Stranger things have happened (I recall the himalayan pray flags that routinely went up during experiments at one beamline at the ALS), but it is a little odd to have my surface scattering experiment refereed to with the proper name of a god. “How is Ganesha today? Is Ganesha’s pressure ok? Is Ganesha’s thermocouple measuring the temperature accurately?”

It turns out that Ganesha the deity is often seen as a patron of science (among many other things). So perhaps the little vacuum chamber Ganesha is not without some obtuse justification beyond mere appearance. For better or worse, the name has stuck and I surely hope that it’s not seen as offensive.

One further thought... Most of our samples involve at least some (if not large) parts made from precious metals such as gold and platinum. So there have ben several occasions where such precious metals have been “offered” to Ganesha. Thankfully he’s always returned them to us intact.