User:Johnny Joe Gonzalez/Notebook/Physics 307L/Entry Base

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Owwnotebook icon.png Electron Diffraction Report.pngMain project page

Electron Diffraction


  • Check for exposed wires or loose connections as voltages as high as 5kV can be used.
  • Use caution when running higher currents through the electron gun as that can damage the graphite sheet.
  • The electron gun has several components made of glass, care should be taken not to break any of the glass components.


The following materials will be needed for the lab:

  • Electron gun
  • Tel2501 Universal Stand
  • Hewlett Packard 6216B power supply
  • Wavetek 85XT Multimeter
  • Carrera precision calipers


  • First connect the electron gun to the power supply, and multimeter. (Most of this was already connected so I simply doulbe checked the connections.
  • I plugged everything in and turned the system on. I checked to make sure that the leds came on and I immediately checked the current, the current was read at 1.1mA.
  • I checked to make sure the calipers were working (note that there is both a mm and inch setting. I made sure the calipers were set to mm.
  • I then raised the voltage to about 500V, and then centered the green dot on the eletron gun.
  • The ring was difficult to observe at this point so after speaking with Dr. Koch, he suggested that we switch the polarity on our bias.
  • After switching the positive and negative connections on the bias the rings on teh electron gun became clearer to see (not much, but it did make a difference). However, the current on the multimeter spiked up after turning down the voltage, this could be due to the way things were connected, to stay on the safe side I turned everything down while recording my data.


  • 1st measurement: voltage set at (4500), bias (16), Ring diameter: 41.9 inner ring: 29.9 multimeter current: .23mA
  • 2nd measurement: voltage set at(4400), bias(16), ring diameter(40.9), inner ring(26.0), multimeter current: .21mA
  • 3rd measurement: voltage set at(4300), bias(16), ring diameter(50.3), inner ring(30.9), multimeter current: .18mA
  • 4th measurement: voltage set at(4200), bias(16), ring diameter(49.21), inner ring(28.2), multimeter current: .18mA
  • 5th measurement: voltage set at(4100), bias(16), ring diameter(52.3), inner ring(31.2), multimeter current: .18
  • 6th measurement: voltage set at(4000), bias(16), ring diameter(52.4), inner ring(32.8), multimeter current: (23.0)
  • 7th measurement: voltage set at(3900), bias(16), outer ring(55.34), inner ring(32.3), multimeter current: .19mA
  • 8th measurement: voltage set at(3800), bias(16), outer ring(54.6), inner ring(33.6), multimeter current:(.19mA)
  • 9th measurement: voltage set at(3700), bias(16), outer ring(55.7), inner ring(33.8), multimeter current:(.18mA)
  • 10th measurement: voltage set at(3600), bias(16), outer ring(56.2), inner ring(na), multimeter current:(.14mA)
  • 11th measurement: voltage set at(4300), bias(16), outer ring(50.8), inner ring(29.2), multimeter current:(14mA)
  • 12th measurement: voltage set at(4500), bias(16), outer ring(51.3), inner ring(28.5), multimeter current:(14mA)
    • Side note:(When the voltage was set to 0, the current spiked to .30mA)

procedure continued

I marked the current over concerns for the equipment.