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ALSNews           Vol. 20           April 11, 1995

Table of Contents


    1. OPERATIONS UPDATE
    2. SUCCESSFUL TESTS OF 1.9 GeV OPERATION AND FEEDBACK SYSTEMS
    3. FIRST LIGHT TO ALS MONOCHROMATIC HARD X-RAY BEAMLINE
    4. ANNUAL MEETING PROCEEDINGS AVAILABLE
    5. HALBACH SYMPOSIUM VIDEOTAPES
    6. "SYNCHROTRON RADIATION SOURCES: A PRIMER" NOW IN PRINT

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

Beam availability last week was 90.8% overall and 86.8% during user shifts. The missing beamtime was caused by problems with storage ring rf Cavity 2 arc detector and feeder interlocks, undulator gap control software, a quadrupole power supply fuse, and a faulty relay in the power supply for booster-to-storage-ring bend magnet 3 (relay replaced).

Operations summary for April 11-30
1.9-GeV, >250-mA, 320-bunch operations for users:
    April 12, 16:00-23:15
    April 13-16, 08:00-23:15
    April 19, 16:00-23:15
    April 20-23, 08:00-23:15
1.5-GeV, 400-mA, 320-bunch operations for users:
    April 26, 16:00-23:15
    April 27-30, 08:00-23:15
Maintenance: 
    April 17 & 24, 08:00-16:00, with startup 16:00-23:15
Accelerator Physics:
    April 11, 18, & 25, 08:00-23:15
    April 12, 19 & 26, 08:00-16:00

2. SUCCESSFUL TESTS OF 1.9 GeV OPERATION AND FEEDBACK SYSTEMS
(contact: robin@lbl.gov)

April 4 saw two exciting new developments during accelerator physics shifts.

First, a beam of 260 mA was accelerated to 1.9 GeV in the storage ring in only two minutes, with a beam loss of only 0.5 mA throughout the ramp. The closed-orbit at 1.9 GeV differs by only 0.2 mm (in both horizontal and vertical planes) from the orbit at 1.5 GeV. Closing the undulator in straight 7 to its minimum gap of 14 mm produced no ill effects. Operation at 1.9 GeV/250 mA for users is scheduled to begin on April 12.

Second, a highly successful test of the prototype longitudinal and transverse multi-bunch feedback systems was carried out. With both systems operational, a current of 175 mA in 40 bunches was accumulated. The special bunch pattern required for these experiments (10 trains of 4 bunches each) is dictated by the limited number of available channels in the low-level electronics of the prototype longitudinal feedback system. The full system, with sufficient channels to handle all 328 bunches in the storage ring, is expected to arrive from Stanford Linear Accelerator Center, the system's designers, before the end of April.

3. FIRST LIGHT TO ALS MONOCHROMATIC HARD X-RAY BEAMLINE
(contact: rupert_perera@macmail.lbl.gov)

Beamline 9.3.1, designed initially for atomic and molecular spectroscopy, saw its first light in March and is now being commissioned. The initial experiments using a gas-phase photoabsorption cell and a time-of-flight mass spectrometer will be carried out with an "unfocused" beam while researchers await delivery of one of the mirrors needed to complete the beamline. Beamline 9.3.1 has the distinction of being the first monochromatic hard x-ray beamline at the ALS, and the brightness at the sample will be an order of magnitude higher than presently available anywhere in the 1 to 6 keV photon energy range. In addition, it will provide flux and resolution comparable to other beamlines now in operation. To achieve these goals, beamline designers incorporated two technical improvements relative to existing beamlines. First, they adopted a novel optical design in which identical toroidal mirrors are positioned before and after the double-crystal monochromator. This configuration allows for high resolution by passing a collimated beam through the monochromator, and for high brightness by focusing the ALS source on the sample with unit magnification. Second, they developed a new "Cowan" type double-crystal monochromator based on the NSLS beamline X-24A design. The measured mechanical precision of this new monochromator shows significant improvement over existing designs. Such precision is essential because of the high brightness of the radiation and the large focal lengths of the mirrors (12 m).

The endstation for the beamline, to be available for initial experiments in May, includes capabilities for electron, ion, and x-ray spectroscopy and is designed specifically to study interactions of gases with x rays in the 1 to 6 keV range. This energy region, in which a number of qualitatively different atomic and molecular phenomena occur, remains largely unexplored. Installation and commissioning of the beamline has been a joint effort of ALS personnel Rupert Perera, Glen Jones, Waiman Ng, and Ed Wong, and undergraduate students Keir Batson, Danny Chen, Eugene Chow, and Greg Fisher. The beamline's PRT is led by Dennis Lindle (University of Nevada, Las Vegas).

4. ANNUAL MEETING PROCEEDINGS AVAILABLE

The Proceedings of the 1994 ALS Users' Association Annual Meeting held on October 20-21 are now available. If you would like to receive a copy, please mail or fax your request to ALS Administration and include your complete mailing address.

ALS Administration
Lawrence Berkeley Laboratory, MS 80-101
1 Cyclotron Road
Berkeley, CA  94720
Fax: (510) 486-4960

5. HALBACH SYMPOSIUM VIDEOTAPES
(contact: joan_minton@macmail.lbl.gov)

A set of videotapes of the Halbach Symposium on Magnet Technology held at LBL on February 3, 1995, are now available for 2 week loan from the ALS Experimental Systems library. Please email requests for the videotapes to joan_minton@macmail.lbl.gov.

Technical presentations at the meeting included: - The First Problem and Personal Reminiscences by Ron Holsinger - The Use of Modified Sextupole Magnets in Advanced Accelerators by Max Cornacchia - Halbach Array/Motor Generators by Richard Post - Transition Undulator Radiation as Bright Infrared Sources by Kwang-Je Kim - Concept of Quasi-Periodic Undulator-Control of Radiation Spectrum by Shigemi Sasaki - Harmonic Generation with Multiple Wiggler Schemes by Rodolfo Bonifacio - Low-Field Permanent Magnet Quadrupoles in a New Relativistic-Klystron Two-Beam Accelerator Design by Simon Yu

6. "SYNCHROTRON RADIATION SOURCES: A PRIMER" NOW IN PRINT

A new reference book that describes the various technical components of synchrotron light sources includes two chapters written by LBL personnel. "Wiggler and Undulator Insertion Devices" was authored by Ross Schlueter of the ALS Insertion Devices R&D Section, and the chapter "Instabilities" was written by Michael Furman, John Byrd, and Swapan Chattopadhyay of LBL's Center for Beam Physics. The editor of the book is Herman Winick of Stanford Synchrotron Radiation Laboratory.

According to the publisher, the book is designed for those who lack a specialized technical background in synchrotron sources, but who have responsibility for some part of the design, construction, operation, or development of such a facility. The reference information is: H. Winick, Ed., Synchrotron Radiation Techniques and Applications, Vol. 1, Synchrotron Radiation Sources: A Primer, World Scientific Publishing Co. Inc., Singapore, 1994. (You can contact the World Scientific Publishing Co. USA office at 1-800-227-7562.)