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. 69           January 22, 1997

Table of Contents


    1. OPERATIONS UPDATE
    2. USERS TAKE NOTE
    3. CRYSTALLOGRAPHY BEAMLINE WIGGLER SEES THE LIGHT
    4. NEW ALS ACCESS SYSTEM IN THE WORKS
    5. DRAFT POST-SHUTDOWN SCHEDULE AVAILABLE
    6. USERS' EXECUTIVE COMMITTEE ELECTION RESULTS

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

Beam reliability for the last two weeks was 92.3% overall and 90.8% for user shifts. The user-shift percentage was affected by the longer time required to refill and ramp the storage-ring energy for 1.9-GeV/2-bunch operation, and by the more frequent refills required in this mode because of the high current per bunch and the resulting shorter beam lifetime.

Operations Summary for January 22 - February 10

Jan 22, 00:00-24:00           Accelerator physics
Jan 23, 00:00-08:00           User scrubbing & special operations
                              (1.9-GeV/40-mA/2-bunch user operations)
Jan 23, 08:00- Jan 27, 07:15  1.9-GeV/40-mA/2-bunch user operations
Jan 27, 07:30-24:00           Maintenance & startup
Jan 28, 00:00-24:00           Accelerator physics
Jan 29, 00:00-08:00           User scrubbing & special operations
                              (1.5-GeV and 1.9-GeV/304-bunch operations)
Jan 29, 08:00- Feb 03, 07:15  1.9-GeV/340-mA/304-bunch user operations
Feb 03, 07:30-24:00           Maintenance & startup
Feb 04, 00:00-24:00           Accelerator physics
Feb 05, 00:00-08:00           User scrubbing & special operations
Feb 05, 08:00- Feb 10, 07:15  1.9-GeV/340-mA/304-bunch user operations

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.

2. USERS TAKE NOTE

Ray Thatcher (rkthatcher@lbl.gov) requests that users who will require ALS technical assistance for beamline work during the May-June shutdown contact him before February 14 with their requests, so the work can be integrated into the overall shutdown planning.

Bob Miller (rmmiller@lbl.gov) notes increasing demand for the special operations shift (the first shift after accelerator physics each week), and would appreciate suggestions from users about a mechanism to allocate this time when there are conflicting user requests.

A new fill pattern has been tested and run at the request of users: the so-called "camshaft" fill. (The nickname camshaft derives from the fact that the one high-current bunch in the circulating electron beam is analogous to the high point or bump on a rotating camshaft.) This fill pattern is 303 bunches with slightly more than 1 mA current in each, and one bunch with 20 mA, for an initial total of 400 mA at 1.5 GeV and 340 mA at 1.9 GeV. The single large bunch is useful for some timing studies. The 20-mA bunch decays with the usual short single-bunch lifetime, while the other bunches, and therefore the beam current, have the usual multi-bunch lifetime. Any users who have noticed an effect of this fill pattern or who anticipate that it will cause problems are invited to contact the ALS Accelerator Physics Group (ajackson@lbl.gov).

This Friday, January 24, is the deadline for users to submit their abstracts for the ALS compendium of user abstracts. Please send your abstracts to the User Office if you have not already done so. If you have questions or need a set of author guidelines, please contact the User Office at alsuser@lbl.gov. Thanks to the many users who have already sent abstracts, including those who were first to respond: Chul-Han Oh (Kyungpook National University, Korea, Beamline 9.3.2) and Harald Braeuning (Berkeley Lab, Beamline 7.0.1).

3. CRYSTALLOGRAPHY BEAMLINE WIGGLER SEES THE LIGHT
(contact: tnearnest@lbl.gov)

In the wee hours of the morning on December 17, 1996, hard x rays came through the first half of the macromolecular crystallography beamline (Beamline 5.0) for the first time. Several members of the beamline's development team intently watched a television screen for the first signs of light inside the beamline as they gradually closed the gap of its 16-cm-period wiggler. After each 1-mm gap decrease, the increasing photon flux caused further outgassing from the beamline's filter array, a beryllium window and carbon foils that absorb the wiggler's soft x rays, so the team waited for vacuum levels to come back down before moving the wiggler again. When they reached a gap of 85 mm, they finally saw a spot of light on the top half of a phosphor plate just upstream of the monochromator; this spot was created by the first hard x rays to come from an insertion device at the ALS.

The macromolecular crystallography beamline is scheduled to deliver light to its first, central endstation in April 1997, and beamline scientists hope to take their first protein diffraction patterns before the May-June shutdown. With the central branchline (5.0.2) fully funded by the Department of Energy's Office of Health and Environmental Research and the University of California at Berkeley, half the funding for a second branchline (5.0.1) has been committed by Amgen, Roche Biosciences, UC Berkeley, and Berkeley Lab matching funds.

The beamline incorporates several innovative design features. Its compact front end allows more optics to be placed inside the shielding wall, near the beamline's wiggler source, and costs less to produce than previous front ends for other ALS insertion-device beamlines. Beamline 5.0 is the first to use a beryllium window to isolate the beamline vacuum from the storage ring vacuum, eliminating the need for a fast valve to guard against storage-ring contamination.

At the other end of the beamline, a conventional CCD (charge-coupled device) detector will be used at first, but a new pixel detector is in development to allow rapid readout of diffraction patterns without interruptions in data collection. (See ALSNews Vol. 54, June 12, 1996, for more on the pixel detector's design.) A prototype pixel detector array has recently been characterized as to its point spread function (the extent to which photons incident on one pixel register in error on adjacent pixels). The tests show that this spreading, which degrades spatial resolution, is at least 10 times smaller for the pixel detector than it is for a CCD detector with similar-size pixels or for a imaging plate.

Participating research team spokesperson for Beamline 5.0: Thomas Earnest, Berkeley Lab Structural Biology Division, tnearnest@lbl.gov

4. NEW ALS ACCESS SYSTEM IN THE WORKS

The ALS has installed a new electronic key-card access system for Buildings 6 (the ALS building), 4, 7, 80, and the user machine shop and clean room in Building 10. (The new system is termed key-card to distinguish it from the card-key which is the proprietary name of a different electronic card system). As a replacement for the metal keys now used, new picture identification key-cards will be issued over the next few months to ALS staff and users. Building 6 will remain a restricted access area (i.e., a key-card is necessary for entrance to the building); Buildings 4, 7, 80, and the Building 10 shop and clean room will be unlocked during normal business hours as is presently the case and the key-card will be required for access outside of normal business hours. A card holder will be provided so that the cards are visible and easily accessible for entrance into the buildings.

During the transition period, both metal keys and the new key-cards will provide access to the affected buildings and areas. To make the transition as smooth as possible, the ALS plans to have the equipment necessary to make the key-cards at the ALS complex for a few weeks to issue cards to staff and on-site users. Eventually new users or returning users will be issued cards at the Reception Center. All staff and users will receive advance notice of when the key-cards will be issued, where to go, etc. Note that staff and users will be asked to turn in their Building 6 keys when they receive their new card.

The introduction of these cards provides us with an opportunity to simplify our visitor access procedure for Building 6 as well. All staff, users, and people escorting visitors will receive the training when they are issued their key-cards.

5. DRAFT POST-SHUTDOWN SCHEDULE AVAILABLE
(contact: fred_schlachter@lbl.gov)

A draft of the long-term schedule for operations for June 10 to November 26 is now available from the ALS for comment.

The draft schedule is similar to previous schedules with the following exceptions: More time is proposed at 1.9 GeV than at 1.5 GeV because most users prefer 1.9 GeV. Although current at 1.9 GeV has been held to less than 400 mA, every effort will be made to reach 400 mA at 1.9 GeV as quickly as possible in the next scheduling period.

No operation is proposed at energies below 1.5 GeV.

Users who have specific comments on the proposed schedule should send them to Fred Schlachter (email: fred_schlachter@lbl.gov; fax: 510-486-6499) by February 14. If you would like a copy of the proposed schedule, send a message to alsuser@lbl.gov with "please send long-term operation schedule" in the subject line and either your full postal mailing address or your fax number in the body of the message. As previously announced, the ALS will be shut down on April 28 for installation and maintenance work. Resumption of user operations is planned for June 10.

6. USERS' EXECUTIVE COMMITTEE ELECTION RESULTS
(contact: terminello1@llnl.gov)

The ballots for incoming members of the Users' Executive Committee (UEC) have been tallied. The new members are: Thomas Earnest (Structural Biology Division, Berkeley Lab), Adam Hitchcock, (McMaster U.), Duane Jaecks, (U. of Nebraska), Stephen Kevan, (U. of Oregon), and student/postdoc electee Jorgen Larsson, (U. of California, Berkeley). With the resignation of Richard Brundle (C. R. Brundle and Associates) and Marjorie Olmstead (U. of Washington), five rather than three were elected.

The continuing members are past chair Jeffrey Bokor (U. of California, Berkeley), Werner Meyer-Ilse (Center for X-Ray Optics, Berkeley Lab), Eli Rotenberg (Accelerator and Fusion Research Division, Berkeley Lab), Mahesh G. Samant (IBM Almaden Research Center), Arthur Suits (Chemical Science Division, Berkeley Lab) and incoming chair Louis J. Terminello (Lawrence Livermore National Laboratory).