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<div>Hi.</div>
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<div>I've been looking for information on the contribution of a self charging phase plate (hole free or Volta)<br>
to the argument of the CTF in weak amplitude and phase approximation for homogenous specimens.</div>
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What function is used to describe the phase shift as a function of spatial frequency?</div>
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<div>Also, is the charge produced by the TEM-beam positive or negative (or both)?</div>
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<div>All the best,</div>
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<div>Philip</div>
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