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Homework Help: X-ray spectrum measurement

  1. May 23, 2006 #1
    Hello, I've got some questions about an experiment I did about the spectrum of a x-ray beam which I measured by looking at the diffraction off a NaCl crystal of the beam coming from a tungsten anode as a function of the scattering angle.

    The measurement I got was something like the following picture
    http://www.physics.leidenuniv.nl/edu/courses/NO/x_ray/x-ray-manual_files/image035.gif [Broken]

    Now you can easily see three large peaks in this spectrum, which repeat themselves at higher angles but only with a lower intensity. Can I interpret these peaks as the diffraction maxima? You can also see that these peaks consist of two peaks very close to each other. Also the distance between those two peaks increases with each higher order diffraction. But I can't find a reason why this is true! :frown:

    Ofcourse the x-ray beam has some penetration depth in the NaCl crystal, which is about 1 micrometer. Can I use this to correct the graph I made?

    Thanks in advance,

    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. May 23, 2006 #2
    What information are you after here? I can probably help if you can give me a bit more information about what you're trying to study here and some details about the experimental setup you were using (ie. did you use a monochromatic beam etc. etc.).

    The attenuation of the beam in the sample does not change the peak positions. The peak positions are entirely determined by the crystal structure of the NaCl crystal.
  4. May 23, 2006 #3
    What I'm trying to find is the spectrum of the x-ray beam 'generator', so I want to see which wavelengths of x-ray are emitted. I generate these x-ray beams by shooting electrons with an energy of 35 keV on a metal plate and using a current of 1 mA. To determine this spectrum I let the beam scatter of a NaCl crystal off the (001) plane and measure the intensity of the beam at various scattering angles. I also need to convert this graph for the intensity versus the angle into a graph of intensity versus the wavelength. I was wondering if I could do that by using Bragg's law. I also wonder why the three peaks are decreasing in intensity with larger angles.
  5. May 24, 2006 #4
    Ok. You can use Bragg's law because naturally Bragg's condition has to hold for you to detect any scattered x-rays. The intensity decreases because the general expression of diffracted intensity contains angle dependent factors like the polarization factor, thermal vibration factor etc. I don't remember the general form by heart but I can check it out for you once I get to work or I can recommend a couple of books that might help you.
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