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Homework Help: Accelerator Physics - Magnetic Quadrupoles Matrix problem

  1. Dec 18, 2012 #1
    Dear reader ( and potential helper)

    I appreciate the time you have taken to even just glance at this topic and for those able to shed some light in any helpful direction, your assistance is greatly appreciated...

    1. The problem statement, all variables and given/known data

    A thin magnetic quadrupole lens may be described by transfer matrices in trace space:

    http://www.khmsolutions.net/p1.jpg [Broken]

    and analogous for y and y′. Positive (negative) focal length f corresponds to focusing (defocusing) in the x-z-plane and defocusing (focusing) in the y-z-plane. Field-free drift over a length L is represented by

    http://www.khmsolutions.net/p2.jpg [Broken]

    Consider the combination of an x-focusing (y-defocusing) quadrupole (f1 > 0), a drift space (L1), an x-defocusing (y-focusing) quadrupole (f2 < 0), and another drift space (L2).

    (i) What are the respective transfer matrices for this combination in the x-x′- and y-y′-trace spaces?

    (ii)Under what conditions does this combination focus an initially parallel beam to a single point?

    2. Relevant equations
    3. The attempt at a solution
    help please...

    Attached Files:

    • p1.jpg
      File size:
      14.7 KB
    • p2.jpg
      File size:
      3.7 KB
    Last edited by a moderator: May 6, 2017
  2. jcsd
  3. Dec 18, 2012 #2


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    Staff: Mentor

    xout = M xin

    This xout is the xin for the next element in your chain. You can multiply all those matrices to get the total transfer matrix.
  4. Dec 19, 2012 #3
    Dear mfb (and anyone else)

    Thanks for taking the time to glance at this and your advisement, please consider the attempt below, been advised something's wrong though....

    http://www.khmsolutions.net/p3.jpg [Broken]

    http://www.khmsolutions.net/p4.jpg [Broken]
    Last edited by a moderator: May 6, 2017
  5. Dec 19, 2012 #4


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    2017 Award

    Staff: Mentor

    "something" is a bit unspecific.
    If it just an error in matrix multiplication: Well, computers can do that.

    As f1>0 and f2<0 are given, I think you should use "+" in both matrices for x. This just changes all signs where f2 appears in the equations.
  6. Dec 19, 2012 #5
    once again, thank you, will give the "+"'s a go...
  7. Dec 20, 2012 #6
    "+"'s were added to Y's as supposed to the X's and it worked.

    Thanks again...
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