S. Krinsky

Design of a harmonic generation FEL experiment at BNL

We present design parameters of a harmonic generation FEL experiment to be carried out at the Accelerator Test Facility (ATF) at BNL. This experiment out as a proof-of-principle for the proposed UV-FEL Users Facility at BNL. In the experiment we plan to triple the frequency of a CO{sub 2} seed laser by utilizing two superconducting wigglers and a dispersive section. The first wiggler will be used in conjunction with the CO{sub 2} seed laser to generate a ponderomotive force that will bunch the electron beam. The bunching will then be enhanced by the dispersion section. The second wiggler, tuned to the third harmonic of the seed laser will follow. In the beginning of the second wiggler the bunched beam will produce super-radiant emission (characterized by a quadratic growth of the radiated power), then the radiation will be amplified exponentially. The last part of the wiggler will be tapered. We plan to study the evolution of the various radiation growth mechanisms as well as the coherence of the tripled and exponentially amplified radiation. 12 refs.

Renormalization group structure for translationally invariant ferromagnets

We introduce a correlation function description of the renormalization group approach to critical phenomena. Our work is based on treating the renormalization group operator as a linear mapping on the set of Ursell functions, rather than as a nonlinear mapping on the space of Hamiltonians. We mainly consider the ’’mean‐spin’’ renormalization group, but the closely related ’’decimation’’ transformation is also considered. Using this approach, we demonstrate for a suitable class of system that the spectrum of the renormalization group operator is bounded and countably infinitely degenerate. We give counterexamples to the notion that there must be convergence to a renormalization group fixed point. Our formulation of the renormalization group is sufficiently general so that convergence to a fixed point does not necessarily imply hyperscaling, i.e., the vanishing of the anomalous dimension of the vacuum, ω*. In the case of convergence to a fixed point we find δ= (d+σ−ω*)/(d−σ−ω*), with ω*?0 necessarily. Above...

An undulator for the 700 MeV VUV-ring of the National Synchrotron Light Source

The magnet parameters and the spectrum of the emitted radiation are considered for an undulator to be used in the VUV-Ring of the NSLS.

Undulators as Sources of Synchrotron Radiation

At the present time the first generation of facilities having electron storage rings designed for and dedicated to synchrotron radiation research are beginning operations in the US, Europe and Japan. The use of wigglers and undulators as enhanced sources of synchrotron radiation plays an important role at all these facilities. Moreover, recently there has been much activity in the design of the next generation machines, which will place even greater, and perhaps exclusive, emphasis on the use of wigglers and undulators. The operation of these insertion devices has been made even more attractive by advances in the design and construction of permanent magnet wigglers and undulators. This reliable and economical technology eliminates the need for more complex superconducting magnets, except to achieve very high magnetic fields for the production of hard photons from relatively low energy rings. We review the spectral properties of the radiation, emphasizing the complementary aspects of time- and frequency-domain analyses. We next study the brightness of the undulator source. Finally, we consider some limitations associated with operating an undulator in a storage ring.

Amplified spontaneous emission in a single pass free electron laser

Abstract We discuss the relationship of the effective start-up noise in a single pass free electron laser to the spontaneous radiation emitted in the initial gain length of the wiggler magnet. Also, it is noted that the number of modes in the output is related to the phase space volume occupied by the spontaneous radiation emitted in the first gain length.

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.

National Synchrotron Light Source VUV Storage Ring

A 700 MeV electron storage ring designed for synchrotron radiation applications is described. Lattice and stability calculations are presented and the vacuum, correction and injection systems are discussed.

Coherent radiation for x-ray imaging—The soft x-ray undulator and the X1A beamline at the NSLS

An undulator-based beamline was built and commissioned at the National Synchrotron Light Source to provide tunable coherent radiation in the 200-800 eV range. The low emittance of the storage ring means that the undulator source has high brightness so that a large flux of coherent x rays is delivered to experimental stations. The beamline uses a horizontally dispersing bichromator that allows two experiments to run simultaneously, making use of the first and second harmonics of the undulator output. In addition, the use of horizontally deflecting optics enables the beamline alignment to be insensitive to electron beam motion since the horizontal electron beam size is quite large. The beamline and its performance are discussed with emphasis on the optics and on stability, radiation, and vacuum considerations.

Development of an in-vacuum minipole undulator array for National Synchrotron Light Source In-Vacuum UNdulator

An in-vacuum minipole (short period) insertion device has been developed in a collaboration between SPring-8 and the National Synchrotron Light Source (NSLS). The magnetic arrays were assembled, field measured, corrected, and vacuum tested by SPring-8 and were installed in an NSLS-developed chamber with mechanical parts in the NSLS X-Ray Ring (E=2.584 GeV) in May 1997 and a successful commissioning of the device was carried out in June 1997. The device is made of permanent magnets with 30.5 periods and a period length of 11 mm. It is designed to produce fundamental radiation at 4.6 keV, and with a modest value of deflection parameter (K=0.7 at 3.3& mm gap) enables higher harmonics to be used as well, for a variety of experiments. A detailed description of the mechanical support and vacuum chamber will be reported elsewhere. We describe technical challenges encountered in constructing this type of device, and present an outline of our collaboration.

Storage ring development at the National Synchrotron Light Source

Beam monitoring systems and other electronic systems at the NSLS storage rings are described in detail. Both the VUV and X‐ray rings are discussed and applications, such as lithography, are proposed. (AIP)