R. Schlueter

Superconducting Undulators With Variable Polarization and Enhanced Spectral Range

A concept utilizing superconducting magnets for variable polarization insertion devices is presented. The iron-free design enables full variable linear and elliptical polarization over a broad spectral range. With appropriate electrical switching the same device can access higher energies through period-halving, while continuing to provide variable-linear polarization; furthermore, separate switching will allow for period-doubling with full linear and elliptical polarization control. The performance, both in terms of field/spectral performance and in terms of polarization control, is compared to existing permanent magnet EPU devices. Engineering issues associated with the fabrication and implementation of the device are discussed

Multiple trim magnets, or ‘‘magic fingers,’’ for insertion device field integral correction

Multiple trim magnets (MTMs), also known as ‘‘magic fingers,’’ are an arrangement of magnets for reducing integrated magnetic‐field errors in insertion devices. The idea is to use transverse arrays of permanent magnets, hence the name ‘‘multiple trim magnets,’’ above and below the midplane, to correct both normal and skew longitudinal magnetic‐field integral errors in a device. MTMs are typically installed at the ends of an ID. Adjustments are made by changing either the size, position, or orientation of each trim magnet. Application of the MTMs to the ALS undulators reduced both the normal and skew longitudinal field integral errors, over the entire 20 mm×60 mm ‘‘good field region,’’ of the beam aperture by as much as an order of magnitude. The requirements included corrections of field and gradients outside the multipole convergence radius. Additionally, these trim magnet arrays provided correction of the linear component of the integrated field gradients for particles with trajectories not parallel to ...

The Next Linear Collider damping ring complex

We report progress on the design of the Next Linear Collider (NLC) damping rings complex (DRC). The purpose of the DRC is to provide 120 Hz, low emittance electron and positron bunch trains to the NLC linacs. It consists of two 1.98 GeV main damping rings, one positron pre-damping ring, two pairs of bunch length and energy compressor systems and interconnecting transport lines. The 2 main damping rings store up to 0.8 amp in 3 trains of 95 bunches each and have normalized extracted beam emittances /spl gamma//spl isin//sub x/=3 /spl mu/m-rad and /spl gamma//spl isin//sub y/=0.03 /spl mu/m-rad. The preliminary optical design, performance specifications and tolerances are given. Key subsystems include: 1) the 714 MHz RF system, 2) the 60 ns risetime injection/extraction pulsed kicker magnets, 3) the 44 m wiggler magnet system, 4) the arc and wiggler vacuum system, 5) the radiation management system, 6) the beam diagnostic instrumentation, 7) special systems used for downstream machine protection and 8) feedback-based stabilization systems.

A low emittance Lattice for the advanced ligght source

The possibility exists of achieving significantly lower emittances in an electron storage ring by increasing the horizontal betatron tune. However, existing magnet locations and strengths in a given ring may be inadequate to implement such an operational mode. For example, the ALS storage ring[1] could lower its emittance to one third of the current value by increasing the horizontal tune from 14.25 to 16.25. Nevertheless, this would come with the cost of large chromaticities that could not be corrected with our existing sextupole magnets. We discuss such operational issues and possible solutions in this paper.

Optimization of circularly-polarized radiation from an elliptical wiggler, asymmetric wiggler, or bending magnet

Abstract To collect circularly-polarized radiation from a bending magnet, elliptical wiggler, or asymmetric wiggler source, one must choose operating parameters to optimize their output according to user requirements. The trade-off between flux and degree of circular polarization is a basic feature of such dipole-type sources. In this paper, we discuss how to optimize the outpuy based on two different criteria. The first is to maximize the intensity times the square of circular polarization degree ( IP 2 ), a widely used figure of merit in circular-dichroism experiments. The second is to maximize the intesity for a given degree of circular polarization, which is desirable in some cases. The results presented here provide guidelines for the design and operation of dipole-type sources to generate circularly-polarized radiation.

Design of the advanced light source elliptical wiggler

Abstract The elliptical wiggler is a circularly polarized light source capable of providing very broad spectral coverage and a high degree of circular polarization. The main features of an elliptical wiggler can be understood through analogy to bending magnet radiation. However, some aspects, such as the end structures influence on the degree of circular polarization, require more elaborate methods to characterize. We present an algorithm based on the stationary-phase method, which allows calculation of radiation properties from an arbitrary electron trajectory, so a non-sinusoidal magnetic fields influence on the radiation performance can be taken into account. We show general radiation properties of an elliptical wiggler and discuss factors affecting the radiation produced. Practical issues encountered during the conceptual design of an elliptical wiggler at the Advanced Light Source are addressed.

Magnet sorting algorithms for insertion devices for the Advanced Light Source

Insertion devices for the Advanced Light Source (ALS) incorporate up to 3000 magnet blocks each for pole energization. In order to minimize field errors, these magnets must be measured, sorted and assigned appropriate locations and orientations in the magnetic structures. Sorting must address multiple objectives, including pole excitation and minimization of integrated multipole fields from minor field components in the magnets. This is equivalent to a combinatorial minimization problem with a large configuration space. Multi-stage sorting algorithms use ordering and pairing schemes in conjunction with other combinatorial methods to solve the minimization problem. This paper discusses objective functions, solution algorithms and results of application to magnet block measurement data. >

New developments in light source magnet design

The rapid growth in the light source community throughout the world has served to motivate innovation in the magnet technologies that serve as the foundations for both the storage ring lattice magnet systems and the primary radiation sources, the insertion devices. Here a sampling of magnet system developments being pursued at diverse facilities are discussed, including combined- function magnets that minimize space requirements and improve accelerator performance, high performance bend magnets that provide enhanced radiation characteristics, and novel and untested concepts for future lattice magnets. Finally, we review developments in insertion devices that promise new performance characteristics to better serve the light source community.

A multiple objective magnet sorting algorithm for the Advanced Light Source insertion devices

Insertion devices for the Advanced Light Source (ALS) incorporate large numbers of permanent magnets which have a variety of magnetization orientation errors. These orientation errors can produce field errors which affect both the spectral brightness of the insertion devices and the storage ring electron beam dynamics. A perturbation study was carried out to quantify the effects of orientation errors acting in a hybrid magnetic structure. The results of this study were used to develop a multiple stage sorting algorithm which minimizes undesirable integrated field errors and essentially eliminates pole excitation errors. When applied to a measured magnet population for an existing insertion device, an order of magnitude reduction in integrated field errors was achieved while maintaining near zero pole excitation errors.

Advanced Light Source elliptical wiggler

A 3.5‐m‐long elliptical wiggler, optimized to produce elliptically polarized light in the 50 eV to 10 keV range, is currently under design and construction at the Advanced Light Source at Lawrence Berkeley Laboratory. Calculations of spectral performance show that the flux of circularly polarized photons exceeds 1013 photons/s over the 50 eV to 10 keV operating range for current of 0.4 A and 1.5 GeV electron energy. This device features vertical and horizontal magnetic structures of 14 and 141/2 periods, respectively. The period length is 20.0 cm. The vertical structure is a hybrid permanent magnet design with tapered pole tips that produce a peak field of 2.0 T. The horizontal structure is an iron core electromagnetic design, shifted longitudinally 1/4 period, that is tucked between the upper and lower vertical magnetic structure sections. A maximum peak oscillating field of 0.095 T at a frequency up to 1 Hz will be achieved by excitation of the horizontal poles with a trapezoidal current waveform. The v...