Welcome to the new and exciting....

How to do it with Leah VanNahmen

This page is here mostly because there are some fun things I'd like to tell you about that are more or less related to my project but don't have a really obvious place to go anywhere else on the site.  I could just randomly throw them somewhere, but that seems horribly unorganized.  So instead, I can randomly throw them here! 

And now it's time for round two!  Don't worry, if you missed out on building your particle accelerator, it's just a little further down the page.  This time, my friends, you are in for a real treat .....


How to Build Fancy Timing Equipment for Stuff Going Faster Than Your Average Superhero!!

So bear with me on this one, because it involves some complicated electronics I’m only pretty sure I have right.  For our NH3+ experiment, we measure the time between when the NH3+ breaks apart and when it hits our detector about a meter away.  It only takes about 1 x 10-6 seconds to travel that far, and we want to measure how long it takes accurately to about 1 x 10-13 seconds.  In other words, we want to measure a really really small amount of time really accurately – and we aren’t even sure exactly when the particle breaks.

  1. Our beam of fluorine gas is bunched – i.e.  it comes in short spurts, so we can use a timer to basically tell when the fluorine gas is in line with the NH3+ so they can collide.  That timer sends the first, really really fast signal through our electronics.
  2. That really fast timing signal sends a message to our detector to record the next four things that smash into it.  The timer also sends a signal that tells the detector to stop recording.  We delay that signal so the detector has time to record the ions that hit it.  When the second signal gets to the detector, it stops recording to help reduce the number of nasty particles like water that shouldn’t be in our experiment but sneak in anyway from interfering too much with our results.
  3. A computer records the time difference between the first signal and the subsequent particles that hit the detector.  Then, we figure out how long it took for the first signal to get to the computer, add the extra time onto the particles’ time differences, and voila!  We have the particles’ Time of Flight.

Just because it’s cool to know:  To slow down the second signal, we usually use the circuit board to send it through lots and lots (we theorize it to be about a mile’s worth) of wire all over the lab.  It’s pretty exciting!




How to Build Your Very Own Tandem VanDegraff Particle Accelerator!!

I know you’ll think this one is neat!  To get the particles flying fast enough in our NH3+ experiment, we need to use this nifty thing known in physics jargon as the LINEAC, which is our own personal Tandem VanDegraff Accelerator.  It is, on the most basic level, a big tube with a thin, massively positively charged foil (usually made of gold, I think) in the middle.  A negatively charged ion (an atom with at least one extra electron) is attracted to the positively charged foil and flies towards it.  By the time it hits the foil, it is going so fast that it flies right through the foil – but not before it looses all its electrons to the big positive charge.  So when it comes out the other side, the ion is now positively charged, and it is repelled by the positive foil.  That means that it ends up going really really fast!  Don’t forget, if you build your own, that you also need a tank of liquid nitrogen – a swimming pool rolled up like a taco might work okay – to keep the accelerator cool.  Good luck!

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