Wiggler Design Research Articles

Helical wiggler design with an array of uniform, small, permanent magnets

An ideal helical wiggler field can be generated inside a cylindrical waveguide by an array of permanent magnets properly distributed and oriented within a cylindrical shell surrounding the waveguide. An approach to the design of the array of magnets and means for assessing the quality of the resultant wiggler field are discussed. The design is optimized in the sense of maximized coupling from the magnets to the field region, subject to practical constraints of uniformity of strength of each magnet in the array. For any array of magnets, the quality of the generated field is expressed in terms of the relative levels of undesired harmonics of the pure wiggler. A “bandolier” design is suggested and evaluated quantitatively, demonstrating that useful wigglers can be generated with a reasonable number of small, uniform permanent magnets.

Design of a large-useful-bore permanent-magnet helical wiggler

A permanent-magnet helical wiggler is being developed at KMS Fusion, Inc., for a two-stage FEL experiment. The theoretical analysis of an analytical model describing a Halbach helical wiggler design is presented. The results of this analysis suggest high field quality can be achieved out to approximately 1 cm radius for moderate segmentation of the magnetization distribution.

Storage-ring free-electron laser operates in the visible

The successful generation of a 6500-Å free-electron laser beam this summer at the French electron storage ring ACO represents a number of firsts. This culmination of a three-year effort by an Orsay–Stanford collaboration at Orsay's LURE (Laboratoire pour l'Utilisation du Rayonnement Electromagnetique) synchrotron-light laboratory is the first operation of a free-electron laser oscillator at a visible-light wavelength. It is, furthermore, the first operation of a free-electron laser oscillator at any wavelength using the circulating electron beam of a storage ring. The Orsay–Stanford FEL is also the first device to achieve laser oscillation with an “optical klystron”—a modified wiggler design suggested by N. A. Vinokurov and Alexander Skrinsky at Novosibirsk (in 1977) for enhancing the gain of free-electron lasers.

A new wiggler beam line for SSRL

A new high intensity beam line with a wiggler magnet source is described. This project, in final stages of design, is a joint effort between Lawrence Berkeley Laboratory (LBL), the Exxon Research and Engineering Company (EXXON), and the Stanford Synchrotron Radiation Laboratory (SSRL). Installation at SSRL will begin in the summer of 1982. The goal of this project is to provide extremely high-brightness synchrotron radiation beams over a broad spectral range from 50 eV to 40 keV. The radiation source is a 27 period (i.e., 55 pole) permanent magnet wiggler of a new design. The wiggler utilizes rare-earth cobalt (REC) material in the steel hybrid configuration to achieve high magnetic fields with short periods. An analysis has been made of the polarization, angular distribution and power density of the radiation produced by the wiggler. Details of the wiggler design are presented. The magnet is outside a thin walled (1 mm) variable gap stainless steel vacuum chamber. The chamber gap will be opened to 1.8 cm for beam injection into SPEAR and then closed to 1.0 cm (or less) for operation. Five remotely controlled drives are provided; to change the wiggler gap, to change the vacuum chamber aperture and to position the wiggler. Details of the beam line optics and end stations are presented. Thermal loading on beam line components is severe. The peak power density at 7.5 m is 5 kW/cm 2 for the nominal wiggler field and present SPEAR beam currents and will approach 20 kW/cm 2 with the maximum wiggler field and projected SPEAR beam currents.

A proposal to install a superconducting wiggler magnet on the storage ring VEPP-3 for generation of the synchrotron radiation

A proposal is discussed to install a superconducting wiggler magnet on the storage ring VEPP-3 in order to shift the spectrum of the synchrotron radiation generated to a shortr wavelength range and to enhance the SR intensity. The basic considerations are presented for optioned wiggler [arameters aimed at the maximum brightness of the source in the range of λ ≈ 1 A ̊ . The characteristics of the SR beam generated by the wiggler have been calculated (i.e. total power radiated, spectral and angular distribution). A 20-pole wiggler design is presented with the length of 1 m, maximum magnetic field strength of 40 kGs, poles spaced by 16 mm and vertical aperture accessible for the electron beam of about 8 mm. The intended wiggler installation scheme in a storage ring straight section envisages the storage of electrons apart from the wiggler aperture using the complete admittance of the storage ring with the subsequent shift of the stored beam into the wiggler by means of the localized closed orbit distortion. The influence of the wiggler field on particles motion in the storage ring has been considered (e.g. closed orbit distortion, betatron oscillations frequency shift, contribution to the cubic nonlinearity etc.).

A short-period helical wiggler as an improved source of synchrotron radiation

A new kind of wiggler is proposed as an improved source of synchrotron radiation from high-energy electron storage rings. The electrons are made to travel in a short-period helix by a transverse helical magnetic field. The radiation spectrum produced is calculated and it is shown that the helical wiggler design could produce a total intensity (photons sec−1 per unit bandwidth) improvement of several hundred and a brightness (photons sec−1 per solid angle per unit bandwidth) improvement of 4×104 over the present state of the art in synchrotron radiation sources.