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First Step to a Spallation Neutron Source
    Given that all journeys begin with a single step, this past year a big first step was taken on the road to opening the Spallation Neutron Source (SNS) when Berkeley Lab researchers commissioned the SNS front-end system, the first of that facility's five major components. When completed, the SNS will be the world's premier facility for neutron scattering science.
Members of the Berkeley Lab Front End Group are shown here with the successfully completed and commissioned front-end system for the Spallation Neutron Source (SNS). With a team of more than 40 scientists, engineers, and technicians, Berkeley Lab was the first SNS partner to complete its part of the project-on time and on budget.  

The SNS is a $1.4 billion multilaboratory collaboration sponsored by the U.S. Department of Energy (DOE) to provide the world's most intense pulsed beams of neutrons. Neutrons are the chargeless particles that exist within atomic nuclei along with protons, their positively charged counterparts. Because of their electrical neutrality, highly energized neutrons can be used as deep-penetrating, nondestructive probes. When a beam of neutrons is directed into a sample material, most pass through, but some bounce off atomic nuclei, a "scattering" that reveals much about the positions, motions, and magnetic properties of those nuclei. From studying the decay of bones during osteoporosis, to improving the storage capacity of CDs and DVDs, to making more accurate weather forecasts from satellite data, the science of neutron scattering provides unique insights into the properities of solid materials.

The SNS will be located at Oak Ridge National Laboratory (ORNL) in Tennessee and is scheduled to begin operations in 2006. It is designed to deliver an average of 1.4 million watts of neutron beam power onto a target--nearly 10 times the capacity of today's most powerful pulsed neutron sources. In addition to Berkeley Lab and ORNL, the other collaborating partners on the SNS are Argonne, Brookhaven, and Los Alamos national laboratories, and the Jefferson national accelerator facility.

Each of the SNS collaborating partners was assigned a specific responsibility. Berkeley Lab's was the front-end system, which generates a beam of negative hydrogen ions and prepares it for delivery into a linear accelerator. From there, these negative ions will be energized to about one billion electron volts in a one-millisecond long pulsed beam and injected into an accumulator ring. Upon entering the ring, the negative ion beam is converted into a proton beam and compressed into one microsecond pulse-lengths. It is then extracted from the ring and smashed into a mercury target to produce neutron beams that can be moderated and guided into designated experimental stations.

  "This milestone should serve as evidence that a collaboration like this can work, and that DOE laboratories can effectively combine resources to serve our nation's needs."

"Berkeley Lab is proud to be the first of the SNS partners to deliver our project on time and on budget," said Berkeley Lab Director Charles Shank when the front-end system was officially commissioned. "This milestone should serve as evidence that a collaboration like this can work, and that DOE laboratories can effectively combine resources to serve our nation's needs."

Said SNS Project Director Thom Mason at ORNL, "As the first SNS partner lab to complete its part of the project, Berkeley Lab is leading the way to successful completion of SNS, on time and on budget. We at Oak Ridge National Lab are grateful for the skill and dedication of the Front End team at Berkeley and the outstanding job it has done."

The SNS front-end system consists of a negative hydrogen ion source, low-energy beam transport (LEBT) system, radio-frequency quadrupole (RFQ) accelerator, and medium-energy beam transport (MEBT) system. A low-energy beam of negative hydrogen ions created in the first two components is passed into the RFQ, which groups the beam into discrete pulses and accelerates them to 2.5 million electron volts. The MEBT creates short gaps in the pulsed beam by chopping it into minipulses of 645 nanoseconds duration, with separations of 300 nanoseconds, in order to facilitate the beam's ultimate extraction from the SNS accumulator ring.

"The completion and successful commissioning of the SNS front-end system has been a huge triumph for us and a terrific accomplishment for the Front End team," says Rick Gough, the physicist who heads the Ion Beam Technology (IBT) program for Berkeley Lab's Accelerator and Fusion Research Division (AFRD).

Construction of the SNS front-end system began in October, 1998, and the projected costs for making it were about $20 million. The system was assembled and tested, component by component, by a Front End Group team that included more than 40 scientists, engineers and technicians.

"That all of the technical challenges in making this system were so successfully met is a credit to the team effort that has characterized the work of the Front End Group throughout this project," Gough says.

In addition to Gough, key members of the Front End Group included physicist Rod Keller, who served as senior team leader with overall responsibility for the SNS Front End Group, physicist John Staples, who led the design of the RFQ and MEBT, and physicist Rainer Thomae, who led the design of the negative ion source/LEBT, all with AFRD; and project manager Ron Yourd, chief engineer Richard DiGennaro, lead electrical systems engineer Alex Ratti, and lead control systems engineer Steve Lewis, all with Berkeley Lab's Engineering Division.

-- Lynn Yarris

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