Search Results (5 total)

This paper explains an analytical formula for longitudinal coherent oscillations in an electron storage ring, including path-length oscillations. A path-length oscillation produced by closed orbit distortion was experimentally identified in the NewSUBARU electron storage ring and found to be harmful to normal operations. Such oscillations are also a potential problem in other advanced light sources especially in a quasi-isochronous operation.

This paper reports a new method of measuring the bunch-by-bunch energy profile of a linear accelerator (linac) electron beam, using a dual-sweep streak camera in the storage ring. This method records the evolution of the time profile in the storage ring following injection. A high-resolution linac beam energy profile is reconstructed from the time profile measured at one-quarter of a synchrotron oscillation period following injection. Conversion between the time profile and energy profile is based on results from a longitudinal phase space tracking simulation. By separating the streak camera images of the different bunches, a bunch-by-bunch energy profile can also be measured.

The dependence of path length on betatron motion in a storage ring is analytically calculated from equations of motion using curvilinear coordinates. It is demonstrated that the change of average path length for one revolution is expressed by a sum of the products of invariant of betatron motion and chromaticity in both the horizontal and vertical directions. Because of this effect, a quasi-isochronous electron storage ring should have a considerable momentum spread when the chromaticities are large.

A simple analytical formula is described for bunch lengthening by a linear horizontal betatron motion in an electron storage ring. An example of calculation shows that this lengthening is larger than the intrinsic bunch shortening limit for most dispersive sections, which strongly limits the wavelength region of coherent radiation.

In an electron storage ring, even if electrons lose the same amount of energy by photoemissions in one turn, their path lengths vary according to where the photoemissions take place. Usually this fluctuation of the path length hides behind the well-known radiation excitation of energy spread. In a quasi-isochronous ring, however, the fluctuation of path length dominates over the bunch stretch owing to the radiation excitation of energy spread. We give an analytical expression for the equilibrium state within linear optics including the fluctuation of the path length. This formula gives an intrinsic lower limit of the equilibrium bunch length in a quasi-isochronous storage ring.