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- R.B. Fiorito, A.G. Shkvarunets
IREAP, Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD, USA
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OTR interferometry (OTRI) has been shown to be an excellent diagnostic
for measuring the rms divergence and emittance of relativistic electron
beams when the energy spread ∆γ/γ is less than the normalized rms
divergence σ = γΘrms. This is the case for most beams previously
diagnosed with OTRI. To extend this diagnostic capability to beams with
larger energy spreads, we have calculated the effects of all the
parameters effecting the visibility of OTR interferences, V; i.e. energy
spread, angular divergence, the ratio of foil separation to wavelength
ratio, d/λ and filter bandpass.
We have shown that:
- for a given ∆γ/γ, the sensitivity of V to σ
is proportional to the observation angle Θ0, the fringe
order n and the ratio d/λ;
- the sensitivity of V to ∆γ/γ is independent of Θ0
and n but is proportional to d/λ.
Thus, by adjusting d/λ, and choosing the appropriate fringe order,
one can separate out and measure both the energy spread and divergence.
However, the filter bandpass must decrease with Θ0 and n.
Results of our calculations will be given for various beams of interest.
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