Advanced Physics Lab


121W Upper division physics lab at UCI

It's my last quarter at UCI and I am excited to do some capstone physics experiments.  In Physics 121W (Advanced Lab and Writing), we get to select experiments from 8 different 20th century physics experiments that shaped physics with groundbreaking results.   

Mass Spectroscopy

The first experiment is mass spectroscopy.  The goal is to accelerate ions evaporated from a sample through a magnetic field to control the path such that we can see what ions our sample contains.


We vacuum a sample down to 5x10^-5 torr, and evaporate it in a filament with a ~9 amp current.  The sample accelerates through a voltage difference and by sweeping the magnetic field we will see different peaks of voltage output.

Week 3 Update

My lab partner and I have been relentlessly working to get data, going in the lab trying to find our Sodium ion measurement, taking extra time to do so.  I am glad to report that Wednesday April 13, by decreasing the accelerating Voltage to 250V, we captured the sodium Peak at around 3100 kGauss magnetic field.  This was thanks to the professor recommending we consider the theory; what lorentz force are we considering, and what kinetic energy the particles have.

Using the accelerating voltage and the fact that the distance it is applied over cancels out, I can use the kinetic energy and circular trajectory acceleration relation to determine the relation between the kinetic energy and necessary B field.  Since Kinetic energy depends only on the mass of the ion and the accelerating voltage, I get an expression for the mass of the ion.

m_{ion} = q B^2 R^2 / 2V

I turned in my lab report for this Wednesday night of week 5 (April 27th), I learned a lot and hope the reader enjoyed my article!
One more image I wanted to share was the graphs I made while bored and waiting for the vacuum to pump down (it took 20 minutes to get down to 10^-4 torr) and then more than 40 minutes to continue pumping down to our desired pressure.



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