I just learned about the assassination of Benazir Bhutto.. I didn’t hear until late this evening because we don’t have TV or cable and I no longer listen to news on the radio. I was really shocked and saddened when I heard. Bhutto was a brave and powerful leader in a part of the world that needed such leaders. I only hope that the outrage from her murder galvanizes people in the region to work for peace. I know that’s not the way it usually works out… but I have faith that were evolving as a species.

The news about the Bhutto tragedy was an abrupt change from the rest of my day, which was very peaceful. My folks are still up visiting, so they hung out with me for the day. We didn’t have much planned. I got an invitation to go visit my friend Scott and his friend Russ to see some cool science geekiness. Around 11, my mom, my dad and I piled in the car and we drove down to Charlotte to Russ’s house. Rus and Scott work together at B.F. Goodrich in Vergennes. Both of these guys are into high energy physics demonstrations on a large scale.

First thing I saw when I got to Russ’s was this huge bank of 4 high energy pulse capacitors.. They were each 230 microfarads at 7000 volts.. that makes each one fully charge capable of discharging (1/2CV**2 = 0.5 2.30×10**-4 x (7×10**3)**2 = 5635 joules… so with four of them charged, that’s 4 x 5635 = 22,540 joules. =~ 22kJ For reference, a 20 joule discharge into your body has a 50 percent chance of killing you.. so this is serious (and very dangerous) power.
Russ and Scott had built them int0 a system they could use to explore high energy pulse phenomenon.

Here’s the rating panel on the capacitors. They came out of an old pulsed laser system from the University of Rochester.

They guys had built as simple 10 kV power supply out of an old neon sign transformer.. It even had a voltage gauge..

The first experiment was exploding wire.. They attached various lengths of MIG wire to a simple jig that was connected to the capacitors by a triggered spark gap. When the chunk of wood was pulled out, the spark gap closed and all the energy in the capacitors was put through the thin piece of wire.

We had to wear protection for both our eyes and our ears.. even if it just meant sticking our fingeres in our ears.. here’s mom and dad preparing for the blast.

The next experiment was ‘coin crushing’ . The idea here is that you discharge the capacitors through a small coil of heavy wire that’s wrapped around a coin such as a quarter or dime. The coin is held between two dowels to hold it steady.

The discharge is so powerful that it blows the coil to bits each time you try it. It explodes with such force that the fragments can travel through a piece of plywood as they did here.

The guys had to switch to using sand as a blast shield to keep from getting covered with shrapnel.

As the coil blows out, the intense magnetic field generated by the high current through the coil creates a tremendously strong radial crushing force that squishes the coin from the edges.. it actually makes the coin smaller in diameter and thicker.. You can imagine doing this with something like playdoh.. but it’s amazing to think of the force needed to do that to a chunk of metal such as a quarter.

We were all hooked up with a quarter and ready to go. Russ hooked the coil with the coin inside to the device and set up the spark gap.. he charged the caps up to 7000 volts

Inside you see our quarter looking a bit squished.

Here’s just how squished it is.. it’s about 30 % smaller and about 30 % thicker, very cool.. Here it is next to an uncrunched quarter.

You can still see the features… but they are distored byt the strength of the blast.

We repeated the experiment with a dime

Here’s a comparison with an un-shrunk dime.

The last experiment was to crush a soda can. In this set up they use a larger, reusable coil of wire. The soda can is put in the middle. If you choose your energy level correctly, it just squishes down the middle of the can like an hourglass. Too much power and the can shreds into two pieces that are shot out like bullets.

It was fun having my folks there, they enjoyed meeting Scott and Russ.. and my buddy Homer who showed up as well. >We then had a great lunch at Good Times Cafe in Hinesburg then came back home. We all took naps.. and I managed to sneak in a few hors to finish up the welding on Gabe’s rail. It should be ready to go tomorrow.

This evening we all went up to Deb’s house for a wonderful dinner party.. Again.. their house was full of our friends.. it feels like home up there. My folks knew many of our friends.. so they had a really good time, too !

Oh wow. it’s late.. I gotta get some sleep.. thar’s all for now. Gnite all, gnite Sam… Love
-me