K.J. Kleman

Throughput and noise of the Aladdin infrared beamline

The infrared beamline at the Aladdin electron storage ring utilizes edge radiation for spectromicroscopy. For wavelengths of 0.8-16 /spl mu/m, computations indicate that /spl sim/20% of the collected radiation is transported through the microscope. Transverse oscillations of the electron beam cause oscillations in microscope throughput that account for about one-third of the beamlines zero-burst noise.

Commissioning low emittance beam at Aladdin

The Aladdin storage ring is now routinely run in a low emittance configuration at 800 MeV. Vertical beam sizes and lifetime are comparable to the original lattice, while the horizontal beam size is reduced by a factor of three. Tools used to commission the new lattice include model based correction to obtain the design machine functions, and model independent correction to set the desired transverse coupling. Newly installed optical profile and position monitors, shunts to trim individual magnets, as well as implementation of a new control system scripting language, were important in achieving the desired results. Special attention was given to operation of the fourth harmonic bunch lengthening cavity used to improve the beam lifetime, and noise reduction in the RF system to improve photon beam quality on the infrared beamlines. In addition, compensation of undulators allows their strengths to be varied with minimum perturbation to the beam outside the regions of the undulators. Details of bringing the low emittance lattice to operational readiness are presented.

Operation of Aladdin at lowered emittance

To increase the available photon flux density for users, alternate lattice tunings of the Aladdin synchrotron light source have been developed with horizontal emittances significantly lower than the present value of 127 /spl pi/ nm-rad. Reduction of the horizontal emittance by a factor of three has been obtained experimentally. When the fourth harmonic Landau cavity is used to lengthen the bunch, the observed beam lifetime with the new lattice is not significantly changed from that of the existing lattice. The present goal is to achieve a factor of four horizontal and a factor of two vertical emittance reduction routinely. Progress in making this new configuration fully operational is discussed, including the use of quadrupole shunts with correction software for beta function and dispersion correction, understanding of a mode coupling instability in higher-harmonic RF systems, RF clearing of ions, and fabrication of new optical monitoring stations.

Implementation and test of a synchrotron radiation position monitor at a user beam line

A slotted plate photodiode beam position monitor was built and installed on a user beam line. The detector is positioned in front of the first optical component of the beam line intercepting ∼3 mrad of synchrotron radiation. A 25‐μm‐thick Be foil strongly attenuates photons with hν<800 eV and improves the position sensitivity by reducing the vertical angular divergence of the effective photon beam by more than a factor of 10. With a 125‐μm gap at 45° angle between the diode plates, the detector has a linear working range of ∼±800 μm. The vertical position sensitivity of the beam position monitor is ∼5 μm.

Robinson modes at Aladdin

A fourth harmonic radiofrequency (RF) cavity improves the beam lifetime of the Aladdin electron storage ring. When the harmonic cavity is operated with a low-emittance lattice, coupling between the dipole and quadrupole Robinson modes may cause instability. During stable operation, damped Robinson modes are observed in the spectrum of phase noise upon the beam

A new real-time operating system and Python scripting on Aladdin

We are in the process of upgrading the VME processors on the Aladdin electron-storage-ring control system. The last major redesign of the control system occurred in the mid 1980s. At that time we converted to VME microcomputers and VAX/VMS workstations communicating via Ethernet. This is the second upgrade since then of the VME processor. As upgrades of the Motorola 680/spl times/0 processor are no longer available we have decided to switch to the Intel Pentium III. This change allowed us to reconsider our use of the rather primitive /spl mu/C/OS kernel and implement a commercial realtime OS. We decided to use QNX primarily as it was a good match to our existing software and was zero cost. In addition to upgrading the CPUs we have also added a new scripting language to our main control application. We used SWIG (Simplified Wrapper and Interface Generator) to create wrapper code for the scripting software. SWIG can create wrapper code for many scripting languages so our initial choice of a scripting language was not critical. We decided to start by using Python due to the many available add-on libraries and the apparent ability to support larger projects. We will discuss our evaluation process and the challenges we encountered.

Current status of the Synchrotron Radiation Center

The Synchrotron Radiation Center operates the Aladdin electron storage ring at energies of 800 meV or 1 GeV in support of a broad range of national and international research programs with a major focus on the study of valence electrons, spectromicroscopy, and nanolithography. Upgrades to the storage ring have improved the stability of the source, and experiments with low emittance lattice configurations show the feasibility of increased brightness for new or enhanced research. Three recently installed undulators, two pure permanent magnet devices and an electromagnetic device, and the associated instrumentation offer experimentalists high flux combined with high resolution. The status of the existing instrumentation, recent scientific results, and an overview of plans for new undulator-based instruments to cover the photon energy range from 7.8 to 400+ eV will be presented.

The Wisconsin VUV/soft xray free election laser

The University of Wisconsin-Madison and its partners are developing a design for a free electron laser (FEL) facility operating in the VUV to soft X-ray range that will be proposed as a new multidisciplinary user facility. Key features of this facility include seeded, fully coherent output with tunable photon energy and polarization over the range 5-900 eV, and simultaneous, independent operation of multiple beamlines. The different beamlines will support a wide range of science from femto-chemistry requiring ultrashort pulses with kHz repetition rates to photoemission spectroscopy requiring high average flux and narrow bandwidth at MHz rates. The facility will take advantage of the flexibility, stability, and high average pulse rates available from a CW superconducting linac fed by a photoinjector. This unique facility is expected to enable new science through ultrahigh resolution in the time and frequency domains, as well as coherent imaging and nano-fabrication. This project is being developed through collaboration between the UW Synchrotron Radiation Center and MIT. We present an overview of the facility, including the motivating science, and its laser, accelerator, and experimental systems.

Improvements to the Aladdin synchrotron light source

Aladdin is an IR to soft x-ray synchrotron light source operated by the University of Wisconsin at Madison. As part of the ongoing program of upgrades and improvements, several changes have recently been made to the ring. It had previously been determined that physical apertures (BPMs) at the QF quadrupoles were limiting beam lifetime when the ring was operated in its low emittance configuration. Increasing the size of these apertures has resulted in a significant increase in lifetime. Also as part of the aperture opening process, a number of ring components were redesigned and replaced, lowering the ring impedance. This has led to an increase in the threshold beam current for microwave instability. An insertion device for EUV lithography has been incorporated into one of the Aladdin short straight sections, and an elliptically polarizing undulator will be installed in another short straight section for a new VLS- PGM beamline. An innovative infrared beamline is under construction, which will extract 320 (H) times 25 (V) mrad2 from a bending magnet by as 12 beamlets, which are combined in an IR microscope. Another modification to Aladdin was the design and installation of discrete trim coils on the quadrupole pole-tips to facilitate using the quads as steering correctors. Details of these improvements are presented.