Cloud Chamber for Smithtown HS

From MariachiWiki

This page documents how this particular cloud chamber was built - for Smithtown High School - during the QuarkNet2006 workshop. Except that most of the pictures (especially the ones with people in them) are of the other cloud chambers, since I was taking the pictures.

Contents 1 June 30, 2006 2 June 29, 2006 3 June 28, 2006 4 June 27, 2006 5 June 26, 2006

June 30, 2006

This was the last day of the QuarkNet 2006 workshop, at least the summer portion. We will get together one more time in the fall, but today is the end of this segment of fun.

We cleaned up the lab, took away our cloud chambers, worked on our blog and wiki entries, and brainstormed on ways to use the cloud chamber in lesson plans.

Here we are, working on our blogs and wikis. Becky, Peggy, and Dennis; Helio watching over Jeff; Mahyar.
		Rich is concentrating; Jeff works well with his eyes closed (at least when the camera is watching).

We spent some time in discussion. At left, Rich is leading a brainstorming session, getting us to think of creative ways to use our cloud chambers in the classroom. Look at ideas that we have posted at Uses of Cloud Chambers. At right, Helio (with "Cosmic Chris" in the background) is leading a video conference with Joe, who is onscreen, somewhere else.

Bill had some last-minute wiring to do. Several of the Hall Effect sensors used in the magnetometer broke. The leads just snapped, so they were useless. A good strategy was to encase soldered sensors in a hard plastic tube, but we learned that just a little late. Here Bill is wiring a new sensor so that he will have a working magnetometer. Don't forget the protective plastic tubing!

Chris, Tom, Jeremy and Ken are enjoying break (outside the classroom door - no food or drink in the classroom!), thanks at least in part to Tania's muffins. Rich looks like he's working, but notice the stockpile of toys within reach ...

I had a great time and hope others did too.

 I talked to a superb bunch of other Physics teachers.  
   I built and ran both a magnetometer and a cloud chamber.  
     I mapped out the magnetic field above a very strong magnet.  
       And I had fun taking pictures and writing in this blog. 

 Every summer should start out like this.

June 29, 2006

Today was a great day. We set up and ran the cloud chambers. It took a little while for the cloud chambers to build up a good cloud, but when they did, particle trails were very obvious and plentiful. They kept going and going and going.

We cleaned the walls of the cloud chamber. It was important to have a clean, water-free environment, so we cleaned the walls with glass cleaner, and then were careful to not touch the walls again.

Above, Candice is industrious. Below, Tom is supervising, while Bill and Jeremy are hard at work. I'm taking pictures.

Then we filled the base with a mixture of dry ice and pure (200 proof) alcohol to make a very cold slurry. We were carful not to actually touch this cold mixture.

Dry ice and alcohol make a very cool slurry. The CO2 sublimes in the alcohol and the bubbles rise very slowly, almost as though the liquid were a gooey syrup. But of course it isn't.

The styrofoam was just taking up space, and we eventually took it out.

Then we put the cloud chambers on top, and sealed edges and gaps with duct tape. Rumor has it that red duct tape works better then grey, but maybe we started the rumor because all we had was red. Anyway, it was very sticky.

Below, Jeff, Ken, Rich, Peggy and Dennis put finishing touches on their cloud chambers. Mine is progressing very well, thank you.

Some of us had pre-soaked the felt pads with pure alcohol, but I waited until closing up to soak them. To do this, I squirted alcohol through the holes drilled in the top of the tank. The alcohol saturated the felt, evaporated, and condensed close to the bottom of the tank. We could see the particle tracks in the cloud close to the bottom.

The particle tracks were great. First you look for a rain-like condensation at the bottom of the chamber. Then you look for little white streaks in the rain. Particles whizzing by provide enough of a site for the supersaturated alcohol vapor to condense on, so a little line of condensing dropplets follows the lines of any particles that fly by. How cool is that!

	Here Becky, Candice, Helio, Bill, Ken, Jeremy and Tom are really excited about what they see. Really.

Problem areas? Were there problem areas?

The glass fish tanks were hard to drill holes through without cracking the glass. I didn't drill my holes (thanks, Jeremy!).

On a few chambers, the felt stips fell down. I think the alcohol dissolved the glue holding the tape to the velcro strips, or the velcro strips to the tank walls. Mine didn't at first, but the felt had fallen by the next morning. Maybe the trick is to not go crazy on saturating the felt with alcohol. Enough is enough.

It took a while for particle tracks to be visible in the vapor clouds. We decided that it was because our base plates were not cool enough, so we took out styrofoam spacers and added more dry ice. I think another problem was that some of our chambers had water vapor in them too. I hadn't sealed the top holes that I had used to squirt in alcohol. Maybe water vapor got in and made a nice water vapor cloud instead of an alcohol cloud. Anyway, after I added more dry ice and closed up the holes I could see lots of particle tracks. Lots. Very cool.

June 28, 2006

We spent the morning mapping out the magnetic field strength at different heights above the base of the cloud chamber. This way we will be able to estimate the magnetic field strength at the very positions that we see tracks in the cloud chamber.

	Here Tania and Helio, Mahyar and Rich, Tania (again), Dennis, Bill and Candice, and Becky and Peggy measure and graph magnetic field values.

We took readings of the magnetic field using the magnetometer - at 2-cm intervals, we took readings using the magnetometer. Then we converted the voltage readings to magnetic field using yesterday's calibration.

June 27, 2006

I started the morning by calibrating my magnetometer. I get about 4.43 mV/Gauss. This is in line with the roughly 5 mV/Gauss that others were getting. That's Chris taking readings.

To convert multimeter reading (x-value, in Volts) to magnetic field (y-value, in Gauss) the conversion is: y = 225.36x - 549.79 .

The conversion from magnetic field (x-value, in Gauss) to potential (y-value, in mV) is: y = 4.4321x + 2440.8 .

Here are pictures of the Hall effect sensor used in the magnetometer. The first picture shows the actual sensor, while the second shows it protected by a plastic sheath.

The next step was getting an existing cloud chamber set up and running. We got very excited about seeing all the tracks left by particles. Most of the particles we see here, at sea level, are muons, electrons, positrons, and occational protons. Electrons and positrons are hard to distinguish except when they are created as a pair. Then one spins clockwise and the other counterclockwise. Protons are easy to identify because they leave a very thick trail about 2-3 cm long. High energy muons go straight through the cloud chamber without being deflected. Low energy electrons can wander through, changing direction several times due to collisions.

And after that we built our own cloud chambers. Here are Jeremy, Bill, Joe, and Jeff, hard at work. I'm taking pictures.

Here's my cloud chamber, in various stages of completion. This one will be going to Smithtown High School.

Breaks were good. Some of us tried a puzzle, in which you try to impale a spherical block on the end of a spike of wood. Helio tells us that the game is called Bilboquet in French, or Bilbo Catcher in English, or Biblioque in Portuguese, or... Ken-DaMa in Japanese. Here Peggy and Tom give it a shot.

We were reminded not to eat or drink (even water) in the lab - the lab that we were using was actually a multi-purpose lab. More often than not it is used for biology and icky stuff. We have been very good about not eating in the lab, but we'll have to remember not to drink in the lab too (even water!). Physics types don't usually have to remember that kind of thing.

June 26, 2006

This is the first day of the QuarkNet2006 workshop. We started the day by becoming more computer-literate. We made wiki entries and started our blogs.

Welcome to my blog

We (the workshop participants) are almost all High School Physics teachers. A notable exception is Helio Takai (User:Takai), the main organizer and also a senior physicist at Brookhaven National Laboratory. More information about me can be found at User: Gwinters.

First we built a magnetometer. It consists of an Allegro Hall Effect Sensor (A1321) powered by three AA batteries, with output to a digital multimeter.

The hardest part about building the magnetometer was that wires broke easily. When that happened we had to start soldering all over again. When it was done, I protected the Hall Effect sensor in a hard plastic tube, mostly so that the wires would not bend back and forth and break.

But why did we build this magnetometer? It was to measure the magnetic field around the strong magnet that we will be using in the cloud chamber (still to be built). Our magnetometer takes a Hall Effect Sensor (read about the Hall Effect), which outputs a voltage that can be calibrated to give the magnetic field at that point in space.

Next we have to calibrate the magnetometer so that the voltage readings on the multimeter tell us the magnetic field strength. That will be either later today or tomorrow.

Breaktimes were good, too. "How many Physics teachers does it take to turn on a projector?" School ended last week, so we mostly compared notes on strategies to get our students to pass the NY State Regents exam, or on good (interesting/fun/useful) things to do with AP-Physics students for the month after the AP exams.

It turns out that physicists, given enough time, can get excited about simple things. Check out the diet coke and menthos combination.