ALSNews is a biweekly electronic newsletter to keep users and other interested parties informed about developments at the Advanced Light Source, a national user facility located at Lawrence Berkeley National Laboratory, University of California. To be placed on the mailing list, send your name and complete internet address to ALSNews@lbl.gov. We welcome suggestions for topics and content.

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ALSNews           Vol. 96           February 18, 1998

Table of Contents


    1. NEW MEASUREMENTS OF SCATTERING FROM MULTILAYER MIRRORS
    2. MESSAGE FROM THE USERS' EXECUTIVE COMMITTEE CHAIR
    3. NEWS FOR USERS: INTERNET ACCESS TO MORE INFORMATION, FORMS
    4. WHO'S IN TOWN: A SAMPLING OF ALS USERS
    5. OPERATIONS UPDATE

1. NEW MEASUREMENTS OF SCATTERING FROM MULTILAYER MIRRORS
(contact: emgullikson@lbl.gov)

Experimenters using the Calibration and Standards Beamline (Beamline 6.3.2) have made the first direct measurements of nonspecular scattering from multilayer mirrors at normal incidence. (A Web page with QuickTime video and images of nonspecular scattering appears at http://www-als.lbl.gov/als/science/sci_archive/EUVmirrors.html.) This advancement in characterizing extreme ultraviolet (EUV) optics will aid the development of mirrors for use in fields such as astronomy and EUV lithography, an emerging technique for manufacturing the next generation of computer chips. (See ALSNews Vol. 83 for more about EUV lithography.) The researchers have also successfully measured nonspecular scattering in grazing-incidence optics, such as those used in synchrotron research.

The characterization of advanced optics is key to new developments in fields where those optics are used, since the quality of an optic can severely limit the performance of a system. In EUV lithography, for example, high contrast is needed to produce a sharply defined line on a microchip. Nonspecular scattering washes out contrast, limiting how narrow a line can be produced. This, in turn, limits how much circuitry can be placed on a given size chip. Until now, mirror makers have had to estimate the amount of nonspecular scattering that occurs in a mirror from measurements of the mirror's surface profile (made either optically or with atomic force microscopy). Direct measurement of scattering permits verification of the accuracy of this technique and provides a new, more reliable evaluative tool. Also, since predictions of nonspecular scattering do not account for scattering by all possible causes, comparing predictions with measurements can help pinpoint the source of unwanted scatter.

Experimenters from Berkeley Lab's Center for X-Ray Optics and Lawrence Livermore National Laboratory used a reflectometer to measure the angular distribution of scattering for Mo/Si-coated multilayer mirrors at several wavelengths in the range of 12-14 nm (90-100 eV). The measurements were made in the vertical plane with horizontally polarized light. A set of apertures just upstream of the reflectometer suppressed scattering from the beamline optics. Inside the reflectometer, light from the ALS struck the mirror under test near normal incidence. Specularly reflected light returned near the normal line. Nonspecularly scattered light given off at angles up to 40 degrees was collected by a channel electron multiplier, and the signal was amplified before being recorded by a computer. The brightness of ALS light made it possible to measure the scattering down to angles as small as 0.01 degree. Resulting intensities were great enough to allow measurement of 10^-9 to 10^-10 of the incident beam, a sensitivity required for meaningful nonspecular scattering measurements.

In another set of experiments, the researchers used an annular microchannel plate to collect scattered light over a broad range of angles at once (to measure total integrated scatter). A phosphor screen behind the plate allowed them to see the signal and record it with a CCD camera. By scanning through a range of wavelengths, they created a digital movie showing how the scattering pattern changes with the wavelength of reflected light. This visualization reveals asymmetries in the finish of a mirror in a new and highly intuitive way.

This work was done in support of a cooperative research and development agreement between the EUV Limited Liability Corporation and Lawrence Livermore National Laboratory, Sandia National Laboratory, and Berkeley Lab (collectively known as the "Virtual National Laboratory") for the development of EUV lithography.

Research conducted by E.M. Gullikson (principal investigator, Berkeley Lab), D.G. Stearns and D.P. Gaines (Lawrence Livermore National Laboratory), and J.H. Underwood (Berkeley Lab) using the reflectometry endstation at Beamline 6.3.2. Funding: EUV Limited Liability Corporation, Office of Basic Energy Sciences of the U.S. Department of Energy.

2. MESSAGE FROM THE USERS' EXECUTIVE COMMITTEE CHAIR
(contacts: w_meyer-ilse@lbl.gov, pjoddone@lbl.gov)

The director of Berkeley Lab, Charles Shank, has charged Pier Oddone, deputy director of the Lab, with leading the planning effort for a "World Class User Program for the ALS." This effort will include ALS management, the ALS User Executive Committee (UEC), the ALS Scientific Advisory Committee, and interested users. The planning process, due to be completed by July 1, 1998, will include

   - An analysis of the current situation to identify areas in need of
change;
   - Bench marking of the ALS program with those of other national
facilities;
   - Creation of a program for change with user involvement and support;
   - Determination of the most effective use of ALS staff for user support;
   - Identification of resources necessary to implement the program; and
   - Identification of organizational changes required.

Any input from the user community will be greatly appreciated. Please direct input, including nominations for people to serve on the task force, to UEC Chair Werner Meyer-Ilse (w_meyer-ilse@lbl.gov) or to Pier Oddone (pjoddone@lbl.gov).

3. NEWS FOR USERS: INTERNET ACCESS TO MORE INFORMATION, FORMS
(contact: alsuser@lbl.gov)

Applying for beam time and becoming a user at the ALS have just become easier for anyone with access to the Internet. "Information for New Users," a new section in our Quick Guide for Users, brings the key information together in one place. "Coming to the ALS" provides a step-by-step guide for registering as a new user, setting up user agreements and accounts, tracking expenses, and more. "Visitors from Outside the United States" gives up-to-date information about visas, insurance, and documentation requirements for international researchers and scholars. The "New User Checklist" provides a quick reference to all required paperwork for users preparing to travel to the ALS.

The Independent Investigator Proposal Form, Experiment Form, and Experiment Modification Form in the "Experiment Information" section of the Quick Guide are now available in RTF (rich text format), which users can fill out with their own word-processing software. Users wishing to fill out forms by hand can still download, view, and print the PDF (portable document format) version of each form using Acrobat Reader. Forms filled out by either method can be sent by mail or fax to the ALS User Office.

4. WHO'S IN TOWN: A SAMPLING OF ALS USERS

To highlight the richness of our user community and help introduce recent arrivals, we offer this listing of some of the experimenters who will be collecting data during the next two weeks at the ALS.

Beamline 7.0.1: Jonathan Denlinger (U. Michigan) will conduct resonant photoemission and spectromicroscopy studies of f-electron systems.

Beamline 8.0.1: Dennis Lindle (U. Nevada, Las Vegas) will study the limits of fundamental approximations in x-ray photoelectron spectroscopy.

Beamline 9.0.1: Nora Berrah (Western Michigan U.) will continue her electron time-of-flight measurements of atoms and simple molecules.

Beamline 9.0.2.2: Cheuk-Yiu Ng, Matt Evans, and Stephanie Stimson (all of Iowa State University) and Gary Jarvis (Berkeley Lab) will do gas-phase pulsed-field ionization photoelectron spectroscopy of the ionic states of molecular oxygen (O2), nitric oxide (NO), carbonyl sulfide (OCS), and acetylene (C2H2).

Beamline 9.3.1: Dennis Lindle (U. Nevada, Las Vegas) will do gas-phase electron-ion and ion-ion coincidence experiments.

Beamline 9.3.2: Harald Braeuning (Berkeley Lab) will study double photoionization of many-electron systems using cold target recoil and electron momentum spectroscopy.

5. OPERATIONS UPDATE
(contact: rmmiller@lbl.gov)

Beam reliability for the last two weeks was 79.1% overall and 87% for user shifts. The unusually low beam reliability resulted from venting of the storage ring through the cracked high-voltage feedthrough of an ion pump. The leak was located quickly, and the feedthrough was replaced with a spare. After two shifts of pumping and several sublimations of the titanium sublimation pumps, scrubbing with beam began. The accelerator physics program for Tuesday, February 3, and the user scrubbing shift for Wednesday, February 4, were devoted to these activities. User operations resumed Wednesday at 0815. The time between refills had increased from 2 hours to 3 hours by Sunday, February 8. Normal operations with 4 hours between refills resumed on Tuesday, February 10.

Long-term and weekly operations schedules are available on the Web (http://www-als.lbl.gov/als/als_ops/ops_home.html). Weekly operations scheduling meetings are held on Fridays at 3:30 p.m. in the Building 6 conference room. The Accelerator Status Hotline at (510) 486-6766 (ext. 6766 from Lab phones) features a recorded message giving up-to-date information on the operational status of the accelerator.