Search Results (5 total)

Response is made to J. A. MacLachlan's preceding Comment [Phys. Rev. ST Accel. Beams 4, 017001 (2001)]. We are gratified to see that high quality simulations, as presented by MacLachlan, verify our experimental results.

By modulating the rf voltage at near twice the synchrotron frequency, the longitudinal bunch shape can be modulated. This method can be used to shorten bunches. We show experimentally that the bunch shape can be modulated while preserving the longitudinal emittance when the rf voltage modulation is turned on adiabatically. Experimental measurements will be presented along with theoretical predictions.

We have derived expressions for the longitudinal and transverse resistive wall coupling impedances for a beam pipe of arbitrary cross section in the ultrarelativistic limit. These expressions involve the integral of the square of the tangential magnetic fields along the wall, which can be obtained from the solution of the two-dimensional Poisson equations with a monopole and dipole singularity, respectively. Explicit results are given for beam pipes of elliptical and rectangular cross sections, including the limiting cases of a circle and a pair of parallel plates.

For free-electron laser (FEL) operating in the exponential regime before saturation, we present an analytic description of the effect on the gain of longitudinal velocity variations arising from wigger field errors. The average gain reduction and the width of the output power distribution are expressed in terms of the mean-square average of the ponderomotive phase shift per gain length. A scheme for correcting the electron trajectory using position monitors and dipole correctors is analyzed. Our work is directly applicable to the design of FEL amplifiers, and the results are encouraging for their feasibility.