E. L. Brodsky

6‐m TGM implementation at the Wisconsin Synchrotron Radiation Center (SRC)

We recently commissioned the SRC/Vanderbilt University 6‐m toroidal grating monochromator beamline. The problems with mirror heating, signal normalization, monochromator control, and scattered light reduction have led to several innovations on this line, making for a better user interface and adding to the stability and reliability of the final image. We discuss these innovations, and how they affect the user. They include a built‐in laser alignment system, a sapphire windowed gate valve, entrance mirror temperature stabilization, computer automation and control, a beam‐chopper, and the capability of real‐time monitoring of the photon flux during the experiment. We have used noble gas resonance lines to carefully characterize the wavelength resolution of the beamline as a function of energy over a range of beamline parameters. The results demonstrate that by limiting the horizontal width of the image at the slits, and by masking outer portions of the gratings, the flux/bandwidth ratio can be improved at t...

Evaluation of a new VUV/soft x‐ray toroidal grating monochromator with a movable exit slit

The performance of a toroidal grating monochromator can be significantly improved by compensating for the wavelength dependent defocusing aberration by means of a movable exit slit. Model calculations of a movable exit slit design show a resolving power that varies nearly linearly with wavelength over the scan range. The energy resolution follows the slope between two optimized resolution minima of a fixed slit TGM. The overall improvement in resolution due to the movable slit depends critically on the figure error of the toroid surface. The Al(LII,III) core edges provide a means to calibrate gratings and determine the resolution at 72.8 eV. A method is described for using the shift in core edge with exit slit position to enable final alignment of the exit slit motion providing stability of energy calibration of 2 meV over the scan range. Comparison of calculations and measured resolution suggests that slope errors remain the limiting factor in performance.

Beryllium window and acoustic delay line design for x-ray lithography beam lines at the university of Wisconsin center for x-ray lithography

X‐ray lithography systems require sample chambers that can perform exposures in helium gas at atmospheric pressure. The interface between the experimental chamber and the beamline is critical for x‐ray lithography and the storage ring. It must allow a high x‐ray flux throughput while providing a vacuum barrier so that helium gas does not leak into the beam line and the storage ring. The beam line must also be designed to have protection in the case that a window does fail in order to minimize adverse effects to the ring and other systems. The details of the design for the vacuum system used on beam lines for the Center for X‐ray Lithography at the University of Wisconsin Synchrotron Radiation Center 1‐GeV electron storage ring are reported. Curved beryllium windows with a 1×5‐cm2 aperture and 13 μm thick that have a leak rate less than 10−10 Torr l/s have been successfully used at the experimental chamber beam‐line interface. This thin flat beryllium foil is mounted in a curved housing with a wire seal to...

New Synchrotron Radiation Center beamlines at Aladdin

In the past year, the Synchrotron Radiation Center (SRC) staff has installed five new beamlines at SRC. Three of these beamlines are ‘‘public’’ beamlines operated by SRC for experiments selected from peer‐reviewed proposals. Fifty to seventy‐five percent of the experimental time on the other two beamlines is managed by the SRC as a consequence of the SRC being a partner in participating research teams (PRTs). These new beamlines bring the number of VUV and soft x‐ray research beamlines installed on Aladdin to 17 as of August 1988. Including two storage ring optical diagnostic ports, there will be 20 ports in use on Aladdin by the end of 1988.

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.

Implementation of an undulator beamline on Aladdin

Abstract The first undulator monochromator on the Aladdin storage ring has been installed and recently tested. The design and alignment of an undulator beamline presented several unique problems not normally encountered in the design of bending magnet beamlines. The primary problem is the lack of visible radiation from the undulator source when it is operated under normal conditions. In this case a temporary beamline was installed to measure the intensity of undulator light transmitted through a pinhole which could be horizontally and vertically scanned through the undulator beam. This was used to adjust the steering of the beam to be centered in the port and to do some nondispersive characterization of the undulator. This temporary line was designed to permit precision alignment of the components of the beamline according to the measured position of the full energy beam. The monochromator used on this beamline is a 6 m toroidal grating monochromator (TGM). It allows further dispersive testing of the undulator and provides dispersed undulator flux for user experiments. The beamline is identical in terms of expected reflectivity losses and grating efficiencies to two similar beamlines implemented on bending magnets. This allows direct comparison of the flux available to experimenters from undulator sources to flux from bending magnets. Initial measurements indicate that with the undulator gap set for 50 eV, at the peak of the first harmonic, the undulator beamline produces 40 times more flux than a similar beamline using a bending magnet source.

Vibration isolation and damping for long focal length synchrotron radiation instruments

Abstract Vibrations of the optical elements in long focal length, high resolution monochromators and other long focal length optical systems used at synchrotron radiation facilities can lead to serious degradation of the performance of these systems. As higher resolution instruments with state-of-the-art spherical and plane elements come on line, vibration will become an increasingly serious problem. The vibrations excited in beamline elements can be at least as serious as position variations of the synchrotron radiation source. Vibrations of beamline and monochromator components may be driven by acoustic waves, ground motion, scanning system vibrations, or vibrations coupled in from experimental equipment such as pumps, fans, motors, etc. This paper will include a discussion of isolation and damping of vibrations in monochromators and beamlines. Various diagnostic methods are described, and a case study of vibration-caused loss of resolution in a 4 m normal incidence monochromator will be presented.

User operation of the first undulator on Aladdin

The first undulator on Aladdin recently began operating as a user facility. The device is equipped with a 6-meter toroidal grating monochromator beamline. The undulator and its beamline have several unique characteristics. Furthermore, the adjacent bending magnet beamline is almost a twin of the undulator beamline, with similar grating efficiencies and reflection losses. This makes it easy to directly compare undulator and bending magnet source beamlines in a realistic environment. The results indicate that the undulator beamline produces between 20 and 100 times more flux in the first harmonic than a similar beamline on a bending magnet. The excellent polarization of 99.5% for the first harmonic makes this beamline extremely useful for polarization studies. User programs based on the undulator radiation included angle-resolved photoemission in gas phase and tests of optical components. The beamline is now entirely dedicated to soft X-ray spectromicroscopy (project MAXIMUM).

The center for X-ray lithography facility status and beamlines development

Abstract The University of Wisconsin-Madison Center for X-ray Lithography (CXrL) is a national facility for basic and applied research in the field of X-ray lithography operating five beamlines dedicated to X-ray lithography at the University of Wisconsin-Madison Aladdin storage ring. In addition to the beamlines, support facilities for lithographic processing are available. A recent development program with ARPA and Motorola has led to a large increase in the processing and methological facilities available at CXrL. CXrL is in the process of upgrading several key aspects of the facility to accommodate the new equipment and research initiatives. A description of the facility upgrades and a summary of beamlines capabilities, research activities and support facilities is provided.

Installation and initial operation of the Suss Advanced Lithography Model 4 X‐ray Stepper (abstract)

A Suss Advanced Lithography X‐ray Stepper designed as a production tool for high throughput in the sub‐quarter‐micron device range has been installed and is being commissioned at the University of Wisconsin’s Center for X‐ray Lithography (CXrL). Illumination for the stepper is provided by a scanning beamline designed and constructed at CXrL. The beamline optical components are a gold‐coated plane mirror, a 1‐micron‐thick silicon carbide window, and a 25‐micron‐thick beryllium exit window. Beamline features include synchronized scanning of the mirror and exit window, variable scan velocity to compensate for reflectivity changes as a function of incident angle, and a horizontal oscillation of the beryllium window during vertical scanning to average the effects of nonuniform beryllium window transmission. A helium purged snout transports the x‐rays from the beamline exit window, to the exposure plane in the stepper. This snout is retractable to allow for the loading and unloading of masks into the stepper. T...