The Advanced Photon Source will be a third-generation synchrotron radiation user facility in the hard x-ray regime (10 - 100 keV). The design objectives for the 7 GeV storage ring include a positron beam natural emittance of 8 X 10^-9 m-rad at an average current of 100 mA. Proposed methods for measuring the transverse and longitudinal profiles will be described. Additionally, a research and development effort using an rf gun as a low- emittance source of electrons for injection into the 200- to 650-MeV linac subsystem is underway. This latter system is projected to produce electron beams with a normalized, rms emittance of approximately 2 (pi) mm-mrad at peak currents of near one hundred amps. This interesting characterization problem will also be briefly discussed. The combination of both source types within one laboratory facility will stimulate the development of diagnostic techniques in these parameter spaces.

Tests of the Boeing Average Power Laser Experiment injector have demonstrated first-time operation of a photocathode RF gun electron accelerator at 25% duty factor. The multi-alkali photocathode was illuminated by a frequency-doubled, mode-locked Nd:YLF laser. The cathode was placed in the first cell of four single-cell cavities resonant at 433 MHz. The 4 cavities accelerated the beam to 5 MeV. The pulse duration was 8.3 ms and the repetition rate was 30 Hz. True average beam currents of up to 35 mA have been accelerated to 5 MeV for an average beam power of 170 kilowatts. The 35 mA beam current exceeded previous photocathode performance by a factor of 1000.

Free-electron lasers and high-energy physics accelerators have increased the demand for very high-brightness beam sources. This paper describes the design of an accelerator which has produced beams of 2.1 (pi) mm-mrad at 1 nC and emittances of 3.7 and 6.5 (pi) mm-mrad for 2 and 3 nC, respectively. The accelerator has been operated between 10 and 18 MeV. The beam emittance growth in the accelerator is minimized by using a photoinjector electron source integrated into the design of the linac, a focusing solenoid to correct the emittance growth caused by space charge, and a special design of the coupling slots between accelerator cavities to minimize quadrupole effects. The FEL has recently operated at 5 microns.

The performance of Free-Electron Lasers depends critically on the quality of the alignment of the electron beam to the wiggler's magnetic axis and the deviation of this axis from a straight line. The measurement of the electron beam position requires numerous beam position monitors in the wiggler, where space is at premium. The beam position measurement is used to set beam steerers for an orbit correction in the wiggler. We propose an alternative high precision alignment method in which one or two external Beam Position Monitors (BPM) are used. In this technique, the field in the elector-wiggler is modulated section by section and the beam position movement at the external BPM is detected in synchronism with the modulation. A beam offset at the modulated beam section will produce a modulation of the beam position at the detector that is a function of the beam offset and the absolute value of the modulation current. The wiggler errors produce a modulation that is a function of the modulation current. It will be shown that this method allows the detection and correction of the beam position at each section in the presence of wiggler errors with a good resolution.

We present here the design description of a new type of planar helical undulator, which we are constructing for the SPEAR storage ring at the Stanford Synchrotron Radiation Laboratory. It comprises four rows of pure permanent magnet blocks, one row in each quadrant about the axis defined by the electron beam. Rows may be translated longitudinally with respect to each other to change the helicity of the magnetic field they create at the position of the beam. They may also be translated longitudinally to vary the energy of the x-rays emitted, unlike designs where this function is performed by varying the gap between the rows. This work includes numerical calculations of the fields, electron trajectories, and x-ray spectra, including off-axis effects.

A three stage superconducting undulator (modulator, dispersive section, and radiator) is under construction at the National Synchrotron Light Source--Accelerator Test Facility at Brookhaven National Laboratory in collaboration with Grumman Corporation. A novel undulator technology suitable for short period undulators (6 - 40 mm) is employed that offers (1) high magnetic fields on axis at short periods, (2) as easily varied field, (3) a variable dispersion, (4) a variable magnetic field taper to ensure optimum resonance between the electrons and the radiation field, (5) transverse focusing to prevent electron beam emittance growth, and (6) low random field errors (below 0.3% rms) as machined and assembled, without shimming or trimming.

At HASYLAB the DORIS III project is almost finished. Recently a decision has been made to use DORIS III as a dedicated synchrotron radiation source in the future. So many conflicts between the operational requirements between synchrotron radiation and high energy physics no longer exist. In the moment nine insertion devices with a total length of 28.3 m are routinely operated in DORIS III. Two new insertion device developments for DORIS III are underway. An asymmetric hybrid structure (ASYH) which can be operated in exchange with anyone of the X-ray wigglers will be available by the end of 1993. For place #5, a 4 m long straight section which is presently still free, a hard X-ray wiggler using a 2 T hybrid structure is in the design phase. It is planned to install this device in the second half of 1994. An exciting new opportunity in the decision to use PETRA, a 12 GeV electron storage ring for synchrotron radiation experiments. An undulator beamline is under construction now.

The U5.0 and U8.0 undulators for the Advanced Light Source incorporate 4.6-m-long, hybrid- configuration magnetic structures. The structures consist of modules with half-period pole assemblies mounted on 0.8-m-long aluminum mounts, which are in turn attached to continuous steel backing beams. The vertical and longitudinal alignment tolerances for the poles of these structures are 25 microns and 50 microns, respectively, over the entire 4.6-m length of the devices. To meet these tolerances, the modules were first aligned individually using an automated coordinate measurement machine and shimming techniques. Several adjustment iterations were required for each module. Averaging and 3D linear least-squares fitting techniques were employed to establish statistically based error reference planes. Graphical spread sheets were used to create representations of vertical and longitudinal pole position errors for alignment.

A self-consistent analysis of weight field errors in free-electron lasers is described using the 3D simulation code WIGGLIN. The 3D wiggler field model chosen is able to treat gradients in the wiggler amplitude since both the divergence of the field as well as the axial component of the curl vanish identically while the transverse components of the curl are small. Hence, the field model is well-suited to the treatment of small imperfections in the wiggler amplitude. In order to describe the wiggler imperfections, a random variation is chosen to determine the pole-to-pole variations in the wiggler amplitude and a continuous map is used between the pole faces. The specific parameters chosen for study correspond to the high-power 35-GHz free- electron laser experiment conducted at Lawrence Livermore National Laboratory; however, the fundamental physics issues are relevant to the entire range of free-electron laser experiments.

The useful flux received in an experiment will depend both on the characteristics of the source and on the characteristics of the experiment. It is therefore necessary when optimizing the design of a synchrotron radiation source to take full account of the experimental requirements and not simply to optimize the integrated flux or brilliance. A method of optimization used for multipole wigglers and bending magnets is described, and applied to a proposed 3 GeV source at Daresbury, DIAMOND, and the proposed 2.1 GeV Swiss Light Source, SLS.

We describe the possible use of the SLAC linac to drive a unique, powerful, short wavelength Linac Coherent Light Source. Using the FEL principle, lasing is achieved in a single pass of a high peak current electron beam through a long undulator by self-amplified-spontaneous- emission (SASE). The main components are a high-brightness electron RF gun with a photocathode, two electron bunch length compressors, the existing SLAC linac, beam diagnostics, and a long undulator combined with a FODO quadrupole focusing system. The RF gun, to be installed about 1 km from the end of the SLAC linac, would produce a single bunch of 6 X 10⁹ electrons with an invariant emittance of about 3 mm-mrad and a bunch length of about 500 micrometers . That bunch is then accelerated to 100 MeV and compressed to a length of about 200 micrometers . The main SLAC linac accelerates the bunch to 2 GeV where a second bunch compressor reduces the length to 30 - 40 micrometers and produces a peak current of 2 - 3 kA. The bunch is then accelerated to 7 - 8 GeV and transported to a 50 - 70 m long undulator. Using electrons below 8 GeV, the undulator could operate at wavelengths down to 2 nm, producing about 10 GW peak power in sub-ps light pulses.

The phase space distribution and time structure of an electron beam have fundamental influences on synchrotron radiation properties. These influences are due to the superposition of radiation from all electrons, each following a different trajectory. When the radiation wavelength is longer than the electron bunch length, coherent superposition occurs and results in the observed coherent synchrotron radiation. Usually the wavelength we use is much shorter, so incoherent superposition occurs and the emittance effect is the dominant multi- electron effect. The Monte Carlo simulation is a straightforward and generally valid approach to compute the multi-electron effects on synchrotron radiation. In this paper, we show how the Monte Carlo method can model these multi-electron effects systematically and discuss the statistical principles governing such simulation and their implication on the computing power requirement. We also describe the implementation of an efficient algorithm to calculate a single electron radiation spectrum, which is important to make the Monte Carlo simulation practical.

For a number of years Los Alamos National Laboratory has been developing photocathode sources of high-brightness electron beams for FEL applications. The APEX FEL, which has been operational for over two years, was the first FEL to use a custom designed rf photoinjector as its electron source. The system consists of a 1.3 GHz, 6 MeV photoinjector with a multi-alkali photocathode illuminated by a frequency doubled Nd:YLF drive-laser, followed by three separately powered accelerating structures that give a final electron energy of 40-MeV. The FEL has operated as an oscillator with either a permanent magnet or pulsed electromagnetic wigglers. Originally the FEL was designed to operate at a wavelength near 3 micrometers , however the electron beam emittance and brightness are sufficient for harmonic lasing at much shorter wavelengths. We have demonstrated the tunability of the device from 0.37 to 11 micrometers .

An electro-optical technique is being developed at the Brookhaven National Laboratory, Accelerator Test Facility (ATF) to monitor and control the phase of the photocathode laser beam with respect to the RF drive field for the RF photocathode gun. This technique utilizes the RF field induced birefringence which is probed by the photocathode laser beam. A proof- of-principle experiment has been performed using the ATF RF photocathode gun injection system for the linac.

A synchrotron light source, from the Brobeck Division of Maxwell Laboratories, designed to operate at 1.2 GeV with a beam current of 400 mA was delivered to Louisiana State University (LSU) and commissioned in August 1992. This was the first commercially supplied light source in the United STAtes and its performance is described along with a discussion of its design and major subsystem operations. The bright radiation produced by the ring is currently used for thin layer resist lithography research, but future application plans include production operations. The experience gained and lessons learned during the LSU project have been applied to the design of a synchrotron in which a 100 mA beam will be accelerated to 2.5 GeV in a ring designed for lithography as applied to micromachining processes and the construction of nanodevices with extreme structural heights. Details of this larger ring design are discussed.

A magnetic wiggler design has been developed for applications in free-electron lasers which is scalable to small periods with high field amplitude, high beam current acceptance, and excellent transverse focusing and beam propagation properties. The Coaxial Hybrid Iron (CHI) wiggler design consists of a coaxial arrangement of alternating ferromagnetic and non- ferromagnetic rings with the central portion of the coax shifted by one half period. The entire arrangement is immersed in a solenoidal field which results in a cylindrically symmetric periodic field. A key advantage of this wiggler configuration is its capacity to handle very high beam currents with excellent focusing and transport properties. FEL configuration using the CHI wiggler design have the potential for high power, high frequency coherent generation in relatively compact systems. Analytic and simulated characteristics of the CHI wiggler are presented.

The Advanced Light Source (ALS), which is currently being commissioned at Lawrence Berkeley Laboratory, is a third generation light source designed to produce XUV radiation of unprecedented brightness. To meet the high brightness goal the storage ring has been designed for very small electron beam emittance and the undulators installed in the ALS are built to a high degree of precision. The allowable magnetic field errors are driven by electron beam and radiation requirements. Detailed magnetic measurements and adjustments are performed on each undulator to qualify it for installation in the ALS. The first two ALS undulators, IDA and IDB, have been installed. This paper describes the program of measurements, data analysis, and adjustments carried out for these two devices. Calculations of the radiation spectrum, based upon magnetic measurements, are included. Final field integral distributions are also shown. Good field integral uniformity has been achieved using a novel correction scheme, which is also described.

With the objective of performing an inverse free-electron laser accelerator experiment, an iron dominated (Vanadium Permendur), fast excitation, high K planar wiggler has been built and measured. We present in this report an analysis of a constant period wiggler and several tapering configurations (gap equals 4 mm; 3.0 cm < (lambda) _w < 5.0 cm) when we drive it to a peak field of B_max approximately equals 1.4 T.

Electron beam storage rings and linear accelerations are rapidly gaining worldwide popularity as scientific devices for the production of high-brightness synchrotron radiation. Today, everybody agrees that there is a premium on calibrating the storage ring model and determining errors in the machine as soon as possible after the beam is injected. In addition, the accurate optics model enables machine operators to predictably adjust key performance parameters, and allows reliable identification of new errors that occur during operation of the machine. Since the need for model calibration and beam control systems is common to all storage rings, software packages should be made that are portable between different machines. In this paper, we report on work directed toward achieving in-situ calibration of the optics model, detection of alignment errors, and orbit control techniques, with an emphasis on developing a portable system incorporating these tools.

A modified multiple bend achromat (MBA) optics as a lattice for low emittance storage rings is presented. The novel feature of this lattice is the use of horizontally defocussing bending magnets with different bending angles to keep the radiation integrals low. It is shown that a storage ring with such a lattice can have a low emittance at a relatively compact size. An application of the MBA structure for a 3 GeV diffraction limited storage ring is presented and discussed.

A theoretical and numerical investigation of the effects of azimuthal and radial angular spread on an electron beam focused by a magnetic lens in the presence of space-charge forces is presented. The particles are inserted with an initial Gaussian distribution in the transverse space and in the momentum coordinates or with a uniform initial current distribution. The particle trajectory equation is derived for parameters of any stationary applied fields configuration with cylindrical symmetry, permitting the non-vanishing initial canonical angular momentum. In the absence of an initial momentum spread particles launched above a critical radial distance from the axis exhibit a `phase-space tearing' effect in the electron distribution. The inclusion of initial angular momentum spread in the model allows for skewed trajectories with strong centrifugal force which prevents the appearance and overshadows the effect of strong space charge forces near the axis which are responsible for the phase space tearing effect.