USE OF OPTICAL TRANSITION RADIATION INTERFEROMETRY FOR ENERGY SPREAD AND DIVERGENCE MEASUREMENTS

OTR interferometry (OTRI) has been shown to be an excellent diagnostic for measuring the rms divergence and emittance of relativistic electron beams when the fractional 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 band pass. We have shown that: 1) 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; 2) 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 band pass must decrease with θ0 and n. Results of our calculations will be given for various beams of interest