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. 94           January 21, 1998

Table of Contents


    1. RF WINDOW SUCCESSFULLY CONDITIONED FOR HIGHER VOLTAGE
    2. EUV OPTICS TESTING SURPASSES LAMBDA/100 MILESTONE
    3. AFTER-HOURS ACCESS MADE EASY
    4. WHO'S IN TOWN: A SAMPLING OF ALS USERS
    5. OPERATIONS UPDATE

1. RF WINDOW SUCCESSFULLY CONDITIONED FOR HIGHER VOLTAGE
(contact: cclo@lbl.gov)

The RF (radio frequency) Section of the ALS Electrical Engineering Group fulfilled a longtime goal in December when it conditioned a vacuum window for an ALS storage-ring rf cavity up to 60 kilowatts. The two storage-ring rf cavities accelerate electrons on each turn around the storage ring, restoring energy lost to synchrotron radiation. Raising the rf power and voltage should increase electron-beam lifetime at 1.9 GeV by reducing electron losses due to Touschek scattering (in which electron-electron collisions force some electrons out of the potential wells, or "buckets," created by the rf system).

The newly conditioned window is one of the original ones manufactured by Interatom during ALS construction. Some of these windows did not meet the required power specification. The RF Section removed the coating from one such window and recoated the window with 10 to 15 angstroms of titanium nitride, a recipe developed with help from K.M. Yu (Materials Sciences Division, Berkeley Lab). The recoated window will be installed in the ALS storage ring in the April-May shutdown, replacing a lower-power-rating window now in use. This should raise the storage ring's maximum rf voltage from 1.1 MV to 1.4 MV. Other windows will be coated or recoated and conditioned for use as spares.

2. EUV OPTICS TESTING SURPASSES LAMBDA/100 MILESTONE
(contact: kagoldberg@lbl.gov)

In December, researchers from the Center for X-Ray Optics (CXRO, Berkeley Lab) demonstrated accuracy of 1/150 of a wavelength in their measurement system for extreme ultraviolet (EUV) optics, surpassing their goal for early 1998 of 1/100 wavelength. This goal is a milestone in the program to develop projection-lithography systems that will use light with wavelengths near 13 nm to manufacture the next generation of microcircuits.

In CXRO's interferometric measurement system (described further in ALSNews Vol. 83, August 6, 1997), a diffraction grating splits coherent undulator light into two partially overlapping beams, both of which pass through the optic under test. In the image plane, one of the beams passes through a 5-micron-wide window, thus retaining information about the quality of the optic. The other beam impinges on an adjacent sub-100-nm pinhole, producing a nearly spherical reference wavefront. The two beams interfere, producing a fringe pattern that can be converted to a map of the wavefront produced by the optic. In the December experiments--"null tests" of the interferometer--researchers replaced the window/pinhole mask with a two-pinhole mask. In this arrangement the two reference wavefronts emerging from the pinholes carry very little information about the test optic (only infinitely small pinholes could carry none at all), and the systematic effects are measurable. These systematic effects can then be subtracted from all future test measurements, bringing the absolute accuracy of the system well below 1/100 of the 13.4-nm test wavelength.

The researchers are using these null tests to find the optimum pinhole size (~50-100 nm) for the interferometer. Further tests will determine optimum specifications for the window/pinhole mask.

3. AFTER-HOURS ACCESS MADE EASY

New ALS users may now obtain temporary access to the ALS experiment floor when they arrive after normal business hours. All new users are required to register and take safety training before they receive a key card/identification badge and official ALS access from the User Office, which is open Monday to Friday between 8:00 a.m. and 5:00 p.m. When users arrive at the ALS outside these hours, they will be given safety training and *temporary* access by the Operations Coordinator or Control Room Operator on duty. Users or their local hosts should contact the Control Room in Building 80 (ext. 4969 from Lab phones) or an Operations Coordinator (ext. 7464) to arrange for training and access to the ALS experiment floor. New users will have to go to the User Office the next working day to complete the registration process and to receive a permanent ALS key card/identification badge. For more information about new user registration, safety training, key card/identification badges, and ALS access, contact the User Office (ext. 7745; email alsuser@lbl.gov).

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

As a national user facility, the ALS attracts users from a wide variety of institutions and disciplines. To highlight the richness of our user community and help introduce recent arrivals, we offer this new feature of ALSNews: a listing of some of the experimenters who will be collecting data during the next two weeks.

Beamline 6.3.2: Dale Grassle and Dick Blake (Harvard-Smithsonian Center for Astrophysics) will be measuring the reflectivity of x-ray mirrors for the x-ray telescope on the Advanced X-Ray Astronomical Facility (AXAF) spacecraft.

Beamline 7.0.1: Wolfgang Eberhardt (Institute of Solid State Research, Forschungszentrum Julich) will be performing soft x-ray emission spectroscopy of semiconductors and semiconductor clusters. Jeff Kortright (Berkeley Lab) will investigate scanning magnetic microscopy using transmission and photoemission modes. Jim Allen (University of Michigan) will conduct spectromicroscopy studies of phase separation in superconducting cuprates.

Beamline 7.3.1.2: Baylor Triplett, Fabia Gozzo, and Ramon Ynzunza (all of Intel) will continue their work for Intel.

Beamline 9.0.1: T. Darrah Thomas (Oregon State University), Thomas Carroll (Keuka College), Jeffrey Hahne (Oregon State University), Edwin Kukk (Western Michigan University), and John Bozek (Berkeley Lab) will be working on high-resolution electron spectroscopy of simple molecules.

Beamline 10.3.1: Nancy Buening (UC Davis) will conduct x-ray microprobe analyses of fossilized and modern seashells. Beamline 12.0.1: Cyndy Bresloff, Ken Goldberg, Patrick Naulleau, Sang Hun Lee, and Chang Chang (all of the Berkeley Lab EUV Interferometry group) will be working on absolute accuracy testing of the EUV interferometer. Gian Franco Lorusso (University of Wisconsin) will use the MAXIMUM x-ray microscope. Steven Kevan (University of Oregon) will be doing a study of molecular interactions on surfaces.

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

Beam reliability for the last two weeks was 96.7% overall and 97.3% for user shifts. All outages were of short duration. Beam quality for user shifts between 00:00 on January 13 and 16:00 on January 16 was affected by problems with the transverse feedback system. These caused the beam spot to be larger and less stable and to have a longer lifetime than normal. Phase adjustments to the local oscillator at each beam position monitor's receiver restored system operation. The cause of the phase shift is not known.

Operations Summary for January 21 - February 8

Jan 21, 00:00- Jan 26, 07:15  1.5-GeV/400-mA/287-bunch user operations
Jan 26, 08:00-24:00           Maintenance & startup
Jan 27, 00:00-24:00           Accelerator physics & machine setup
Jan 28, 00:00-08:00           User scrubbing & special operations
Jan 28, 08:00- Feb 02, 07:15  1.9-GeV/400-mA/287-bunch user operations
Feb 02, 08:00-24:00           Maintenance & startup
Feb 03, 00:00-24:00           Accelerator physics
Feb 04, 00:00-08:00           User scrubbing & special operations
Feb 04, 08:00- Feb 08, 16:00  1.9-GeV/400-mA/287-bunch user operations