Mining for Physics

From the beginning of my graduate student career in my group, I was told we would take my experiment underground within the next semester. After 3.5 years, it finally happened! Over the summer, I completed the 20 hours of miner certification training, as well as 4 hours of first aid training, and now, barring the 8 or so hours more of on-site training I have to complete, I am a certified miner! Good thing, too. If this grad school thing gets tired I’ll just don my hard hat, flick on my MSHA-approved light and start my career in mining. Surely there’s at least some good health insurance included or something.

I’m sure you’re wondering what the benefits of taking half a million dollars worth of equipment underground are. That’s an excellent question! We are looking for double-beta decay, a rare decay with a half-life on the order of 10^20 years. Normally, aboveground with a kilogram of source material, we see about 12 events per year. Any background is therefore dangerous to our signal. One way to rid ourselves of natural background (nuclear decays which occur all the time around us from cosmic rays to Thorium chains found in concrete) is to provide shielding. Shielding can be active (as in other detectors which veto events that come from the outside) or passive (massive amounts of lead bricks which just sit there absorbing stuff). Aboveground, we had both of these. Underground, we have the added benefit of an entire mountain providing shielding from the cosmic rays. Because the sodium iodides can actually provide background from their natural contaminants, we are hoping that we can get along without them in the mine. We brought the lead bricks, though. (The bane of my existence…)

Our underground lab is located some 1700 ft below Butt Mountain (Insert obvious joke here.) in the Kimballton Mine in southwest Virginia. (Oddly enough, at the actual level of our lab, we are nearly the same elevation as Durham…) Though I have not seen any myself yet, the locals claim there is a herd of wild goats which live near the entrance to the mine. Apparently, they go in the mine because it’s warmer there in the winter. The mine remains a balmy 55 degrees F year-round, and nearly 100% humidity. I’ll report back if they are seen!

I also feel compelled to include this link ( to a conspiracy theory about Kimballton. Nothing like conspiracy to add an extra edge to your thesis!

We rented a Penske truck to haul all our equipment underground. You can only drive diesel trucks in the mine. We didn’t tell Penske where their truck was going!

Here’s Werner and me all decked out in our gear. (Not the best use of the flash, hm?)

This is the entrance as seen from the inside of the mine. You just drive on in there and the road corkscrews downward.

This is our “hangar”-type structure, inside which we have our little trailer which houses the experiment. Other experiments will eventually be housed here as well. There’s already another trailer there from NRL.

And here we are, the TUNL crew standing in front of our trailer. I look weird because I was sort of leaning and crouching so I wouldn’t block the TUNL logo, but it just looks like my legs are really short.

That’s all for now. I hope you’ve enjoyed my adventures in mining!


4 Responses to Mining for Physics

  1. jwambaugh says:

    Very cool Mary! What is the typical background rate for events?

    Also, I was a little surprised to here the wild claim that Va Tech was good for “engineering and mind control.” I’m sure the shootings last year added fuel to that conspiracy’s fire.

  2. bpt2 says:

    Cool Mary! Does this mean you can swear like a miner?

    And please, can someone explain to me what the hell the conspiracy guy was getting worked up over? I read through the whole thing, but he never go to a point. My favorite quote: “There is only one problem with her claims– Butt Mountain is not in Blacksburg.” Yeah… that’s the only problem…

  3. mfkidd says:

    Good question…depends on a few things: the energy at which you are looking for a signal (the lower the energy, the more background you get from Compton scattering from higher energy decays), and the purity of your source being the two that I can think of offhand. For our Molybdenum-100 measurement, we had about 4 background counts under our signal (of 16 net events) in 450 days of measurement. We measured Neodymium-150 for about 90 days and any signal we might have had was completely blocked by background. In that case, our source had been contaminated with a natural decay chain (Thorium-232) which has decays right in our region of interest. Ironically, these decays were introduced in the isotopic purification process at Oak Ridge. I guess the separator there was also used to separate something that contained Th-232 and thus it gets into everything. The third isotope we’ve looked at, Tin-112, is extremely pure and after about 65 days we had zero background counts in our region of interest. But, we only have 4 grams of that isotope. The thing is, we don’t have a good idea of how much of our background is from cosmic rays. Hopefully, being underground will result in a drastic reduction of the background!

    I think the goats are under mind control.

  4. mfkidd says:

    Only when wearing the hard hat, bpt!

    Yeah I’m not entirely sure about what the guy was worked up about. I think poor google had probably just put the flag for DUSEL at the physics department because until recently (the last 6 mo or so), there WAS no underground physics lab at Kimballton. And now, the Kimballton mine is assuredly NOT the DUSEL (Deep Underground something something Laboratory) site, it was just a proposed site for DUSEL. DUSEL is going to be at Homestake in SD and Kimballton will be called KURF (Kimballton Underground Research Facility). The “researcher” could have found this if he’d looked somewhere besides google earth and a suspicious guy at an arsenal, or whatever.

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