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Homework Help: Critical energy

  1. Mar 13, 2015 #1
    1. The problem statement, all variables and given/known data

    A silicon component is irradiated in an accelerator. The oxygen ion beam is pointed in the direction of the shortest dimension of the sensitive volume of the device. The energy required for producing an electron/hole pair in silicon is 3.6 eV. It is found that the highest energy for which SEU (Single-Event Upsets or “soft errors”) is observed is 10 MeV/nucleon. Assume that the shortest dimension of the sensitive volume is 2 µm and that ion energies do not change during traveling.

    2. Relevant equations

    Ec = ρSi*d*LETm,th


    3. The attempt at a solution

    ρSi = 2.33 g/cm^2
    d = 2μm

    I have trouble to read of the diagram of what LETTh is. If the energy is 10 Mev and if i draw a straight line upward i got the value of 10^0 or 1 LET (Mev * cm^2/mg). In the solution manual the LETTh value is 0.85 why ?

    Ec = 2.33*0.0002*0.9/10^-3 = 0.391 Mev
  2. jcsd
  3. Mar 13, 2015 #2


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    Staff: Mentor

    I get a smaller value, even a bit below 0.85.
  4. Mar 14, 2015 #3
  5. Mar 14, 2015 #4


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    2017 Award

    Staff: Mentor

    Using your pixel values for the positions, I get about 0.87. I put it one pixel lower which gave 0.82. It is a log scale, so 15% difference is not much.
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