ALSNews Vol. 280

X-ray imaging current-driven magnetic domain-wall motion in nanowires

Contact: Peter Fischer, pjfischer@lbl.gov

The quest to increase both computer data-storage density and the speed at which one can read and write the information remains unconsummated. One novel concept is based on the use of a local electric current to push magnetic domain walls along a thin nanowire. A German, Korean, Berkeley Lab team has used the x-ray microscope XM-1 at the ALS to demonstrate that magnetic domain walls in curved permalloy nanowires can be moved at high speed by injecting nanosecond pulses of spin-polarized currents into the wires, but the motion is largely stochastic. This result will have an impact on the current development of magnetic storage devices in which data is moved electronically rather than mechanically as in computer disk drives. Read more…

Publication about this research: G. Meier, M. Bolte, R. Eiselt, B. Krüger, D.-H. Kim, and P. Fischer, “Direct imaging of stochastic domain-wall motion driven by nanosecond current pulses,” Phys. Rev. Lett. 98, 187202 (2007).

Extracellular proteins promote zinc sulfide aggregation

Contact: John Moreau, jwmoreau@usgs.gov

Researchers from the ALS, Berkeley Lab’s National Center for Electron Microscopy (NCEM), and Lawrence Livermore National Laboratory analyzed biofilm samples rich in zinc sulfide and dominated by sulfate-reducing bacteria, which were collected from lead–zinc mine waters. The researchers were curious about the relationship of the organic material and metals, particularly how organics affect mobility, and its potential for bioremediation. It is known that some organics promote aggregation. Amine-bearing molecules, for example, can organize sulfide nanoparticles into semiconductor nanowires. The research team used a series of imaging techniques and detectors to analyze aggregates of biogenic zinc sulfide nanocrystals in the biofilms. Their examination yielded excellent results and some surprises. They were able to prove that natural organic matter promotes dense aggregation of the zinc sulfide nanocrystals into much larger spheroids and that the organic matter is preserved in nanometer-scale pores in the spheroids. What was not expected was the presence of proteins in the spheroids, making them a key component in aggregation and an example of extracellular biomineralization. Read more…

Publication about this research: J.W. Moreau, P.K. Weber, M.C. Martin, B. Gilbert, I.D. Hutcheon, and J.F. Banfield, “Extracellular proteins limit the dispersal of biogenic nanoparticles,” Science 316, 1600 (2007).

Upgrades to Beamlines 8.2.1 and 8.2.2

Contact: Paul Adams, pdadams@lbl.gov

The ALS is midway through a two-year upgrade to Beamlines 8.2.1 and 8.2.2, the two superbend macromolecular crystallography beamlines operated by the Berkeley Center for Structural Biology (BCSB). The improvements are designed to allow screening of, and data collection from, small crystals and will help resolve structures of large complexes.

Two major parts of the upgrade have been completed. In December 2006, an upgraded large-format CCD detector was installed on Beamline 8.2.1 to facilitate high-resolution data collection and the study of crystals with large unit cells. After extensive offline testing, a Rigaku ACTOR robot was installed in the endstation hutch at Beamline 8.2.2 during the recent shutdown. It is compatible with other automounters at the ALS and has a Java control system that has been integrated into the BCSB BOS beamline control software. An identical robot will be installed at Beamline 8.2.1 and is presently undergoing offline testing. Remote-viewing and data-collection software are also under development.

The Rigaku ACTOR robot was extensively tested offline to assure safety to users (large envelope of motion, key-activated dead man’s switch), safety to equipment (detector, shutter, etc.), hardware interlocks (doors, dewar lid), software interlocks (beamstopp, detector cover), and exclusion zones.

Later this year, a new MD2 microdiffractometer from Accel will be installed on Beamline 8.2.1. The MD2 is designed for working with small crystals; it is capable of high-resolution crystal imaging, and the integrated beam collimation devices will define the beam of a desired size with minimized air scatter.

Next year will be devoted to upgrading the optics on Beamline 8.2.1, which will extend its capacity to the limits of the technology, with the goal of decreasing the spot size from 100 to 30 microns and increasing the beam brightness by a factor of 5. An internally cooled Si design was chosen for the front-end parabolic mirror as it gives the best thermal performance of the options available. The second mirror will be replaced with one of the same design as is currently used, but with a lower slope error. The monochromator upgrade will include the addition of multilayer crystals, which will give the option of higher flux at lower resolution (similar to the existing monochromator on 12.3.1), and direct liquid-nitrogen cooling of crystals, which will reduce thermal distortions by more than a factor of ten.

These beamlines have grown tremendously since their commissioning in 2003, becoming two of the most productive crystallography beamlines at national synchrotron light sources. This upgrade, which is funded by the Howard Hughes Medical Institute, will ensure that they continue at their high level of operation.

Groundbreaking ceremonies for User Support Building and Guest House

Contact: Jeff Troutman, jptroutman@lbl.gov

This year’s ALS Users’ Meeting will feature two official Laboratory groundbreaking ceremonies in two days, unprecedented in the history of Berkeley Lab. All ALS and Laboratory staff are invited.

On Thursday, October 4, at 12:15 p.m., the groundbreaking ceremony for the ALS User Support Building will take place on the Renner Deck next to the building site west of the ALS. The 30,000-square-foot, three-story structure, to be funded by DOE’s Office of Basic Energy Sciences, will offer modern experimental staging and assembly space, support laboratories, and offices.

ALS User Support Building.

The next day, the Laboratory will host the groundbreaking ceremony for the Berkeley Lab Guest House (12:00 noon on the site of the new structure, west of Building 2). Located within a short walk of the ALS and the cafeteria, the Guest House will provide 70 beds in single- and double-occupancy rooms and will include a main lobby, lounge areas, a fitness center, laundry, vending areas, and an outdoor patio. Funding for the Guest House will be provided through external financing, and expenses will be covered by revenues collected for room rentals, vending, and sales. The Howard Hughes Medical Institute has provided a generous grant for furniture, fixtures, and equipment.

Berkeley Lab Guest House.

The late Gary Krebs, ALS User Services Group Leader from 1998 to 2007, worked tirelessly on plans for the Guest House. Members of his family are among those expected to attend.

UEC Corner: ALS Users’ Meeting update

Contact: Tony van Buuren, vanbuuren1@llnl.gov

For the first time, the Users’ Meetings of the Advanced Light Source and the Molecular Foundry are being organized jointly and simultaneously. The meeting will be held on October 4–6. At the meeting there will be a joint plenary session, a joint poster session, and several joint workshops. We hope to stimulate strong interactions between the two user communities. The ALS meeting co-chairs, Peter Fischer and Ken Goldberg, together with Jeff Bokor from the Molecular Foundry, have put together an exciting program highlighting scientific achievements at these facilities and looking toward the future. More information on the Users’ Meeting can be found on the Web site.

Also, it is time for the annual election of new members to the ALS Users’ Executive Committee. Please take a moment to look at the UEC Election Web site and nominate suitable candidates from the ALS community who would be willing to serve. If you have any questions, please contact me or any other UEC representative. I look forward to meeting many of you at this year’s meeting.