G. Vignola

Real time harmonic closed orbit correction

Abstract We discuss several schemes for improving the stability of the closed orbit, by implementing a feedback system based upon harmonic analysis of both the orbit movements and the correction magnetic fields. The harmonic feedback system corrects the Fourier components of the orbit nearest to the betatron tune. Such a system may provide a significant improvement in orbit stability for all beamlines, using simpler electronics than required for an array of local bump feedback systems. Experiments based upon these schemes are in progress at the NSLS.

Real time closed orbit correction system

A global closed-orbit feedback experiment based upon a real-time harmonic analysis of both the orbit movement and the correction magnetic fields is described. The harmonic feedback system was constructed and tested on the 750 MeV vacuum ultraviolet ring of the NSLS (National Synchrotron Light Source) and implemented on a real-time basis using relatively simple electronics. The feedback forces the coefficients of a few harmonics near the betatron tune to vanish and significantly improves the global orbit stability. The result of the experiment in the ring using four detectors and four trims, in which maximum observed displacement was reduced by a factor of between three and four, is presented.<<ETX>>

Design concepts of a storage ring for a high power XUV free electron laser

Abstract We report on the study of a storage ring capable of sustaining an electron beam of the quality required for a high-gain free electron laser in the vacuum ultraviolet and X-ray region. We describe a method for the optimization of the design of the storage ring where several competing and often conflicting requirements come into play. We present an example design of a ring that satisfies the required conditions of beam quality and is able to produce coherent radiation at 400 A with tens of megawatts of peak power.

Bunch lengthening control using the fourth harmonic cavity in the VUV ring

It is suggested that a harmonic cavity in a synchrotron storage ring can be used to change the shape of the bucket potential. Adjustment of the amplitude and phase of the harmonic component to flatten the slope of the waveform of the synchronous voltage will lengthen a stored bunch, thus extending the Touschek lifetime that is limiting the performance of the VUV ring. Beam-induced 211-MHz power in a fourth-harmonic cavity was used to check the feasibility of this concept. The data obtained during UV studies at the NSLS (National Synchrotron Light Source) are summarized.<<ETX>>

A new method for pumping an optical klystron

A novel method of operation for a transverse optical klystron (TOK) is proposed. The TOK is a device in which a relativistic electron beam produces tunable coherent radiation at short wavelengths by interacting with a powerful external laser and an undulator field. Here we show that, by selecting the external laser wavelength to be one of the harmonics in the undulator radiation spectrum, excellent output at short wavelengths can be realized with significantly reduced performance requirements for the undulator magnet and the storage ring providing the electron beam.

Preliminary design of a dedicated 6 GeV synchrotron radiation storage ring

Abstract A new magnetic lattice is proposed for a 6 GeV electron storage ring specifically designed for utilization of high brightness undulator and wiggler radiation sources. The basic cell is an achromatic arc with three combined function dipoles, having a vertical focusing gradient. With this arrangement it is possible to achieve an electron beam emittance of ∼ 6 × 10 −9 m·rad at 6 GeV, moderately low chromaticity and good dynamic aperture.

The use of gradient magnets in low emittance electron storage rings

Abstract The use of gradient magnets for a low emittance electron storage ring is discussed and a magnetic lattice for a 6 GeV electron energy synchrotron radiation source adopting this feature is presented.

A Lattice and Bypass Design for a Coherent XUV Facility

The design of a magnet lattice and bypass for a coherent radiation facility is discussed. The lattice is the missing magnet FODO structure first proposed by Vignola [3] for a 6 GeV light source. This has been adapted for a 750-1300 MeV electron storage ring for use with both conventional insertion devices and a high gain FEL optimized for output at 400 Å. The latter device requires that the electron bunch be deflected into a small aperture bypass, then reinjected into the ring where the perturbing effects of the FEL are damped out.

A Study for a 6 GeV Undulator Based Synchrotron Radiation Source

A partial study for a 6 GeV undulator based synchrotron radiation source for production of high brightness undulator radiation, in the Å, is presented. The basic lattice adopted for the storage ring is a hybrid FODO Chasman-Green lattice, making use of gradient in the dipoles. We discuss also the e beam current limits and the injection parameters.

Optimization of the Parameters of a Storage Ring for a High Power XUV Free Electron Laser

In this paper we describe the operation of an XUV high gain FEL operating within a bypass of an electron storage ring, and discuss the implications on storage ring optimization imposed by FEL requirements. It transpires that, in the parameter regime of interest, collective effects within the beam play an important role. For example, intrabeam scattering dilutes the transverse emittance of the beam and the microwave instability increases the momentum spread. Both phenomena reduce the effectiveness of the FEL. A computer code, ZAP, has been written which, for a given lattice design, takes all such effects into consideration and produces a figure of merit for FEL operation for that machine. We show the results of ZAP for several storage ring designs, all optimized for FEL operation, and present a design example of a facility capable of producing coherent radiation at 400 Å with tens of megawatts of peak power.