On their first try, researchers at the Spallation Neutron Source in Oak Ridge, Tennessee, successfully ran an ion beam through the first of 10 accelerator tanks from Los Alamos. The achievement clears the way for Los Alamos to continue building five more of the so-called drift-tube linear accelerator tanks, or DTLs, as well as four coupled-cavity linacs that will further accelerate the SNS beam.
The SNS is sponsored by the Department of Energy's Office of Science, and currently is the largest civilian science construction project in the United States.
Los Alamos SNS Division Leader Don Rej said ensuring a robust physics design and precision alignment of hardware were the keys to making sure the accelerator worked right the first time.
"This was a major team effort between Oak Ridge National Laboratory and Los Alamos. Reaching this major milestone for the SNS accelerator program took a lot of combined expertise from more than 100 staff from Los Alamos and our colleagues from the other labs," Rej said. "Los Alamos had complete technical responsibility for the design, engineering and manufacturing of all the components and subsystems. Last week, it all came together for the first time."
In addition to the DTLs and coupled-cavity linacs, Los Alamos is responsible for the high-voltage pulsed-power systems, high-power radio frequency systems, control systems and the overall accelerator physics design, including beam dynamics and diagnostics, Rej said.
The SNS consists of a source of an ion source and a radio frequency quadrupole accelerator, built by Lawrence Berkeley National Laboratory and successfully completed and tested last winter; the 10 Los Alamos linacs and one-of-a-kind superconducting niobium linac cavities designed by the Thomas Jefferson National Accelerator Facility; an accumulator ring from Brookhaven National Laboratory; a mercury spallation target designed by Oak Ridge; and a suite of neutron scattering detection instruments from Argonne National Laboratory and Oak Ridge.
The SNS will produce 1.4 million watts of short proton pulses that strike the target to produce pulses of neutrons every 17 milliseconds. By producing 10 times more neutrons than the most powerful sources available today, the SNS will let researchers take brighter, more detailed snapshots of material structures and even enable them to make "movies" of molecules in motion.
The August 28 test involved accelerating a beam of negatively charged hydrogen ions through the first drift-tube linear accelerator tank, or linac, and measuring the speed, current and other characteristics of the beam in a diagnostics section also designed by Los Alamos. Continued around-the-clock tests of the first section will continue through early October.
The short-pulsed current initially measured four milliamperes and, after a week is nearing 20 milliamperes. This raised the initial beam energy produced by the ion source of 2.5 million electron volts, or MeV, up to 7.5 MeV. By June 2006, when SNS is scheduled for completion, the additional linac sections will accelerate the beam to 1000 MeV, or 92 percent of the speed of light.
"This was a major step for the SNS," said Norbert Holtkamp, SNS accelerator systems director at Oak Ridge.
"Commissioning the first DTL Tank represents the next stage in the SNS accelerator, requiring integrated operation of the linac itself along with associated RF, cooling, control and diagnostic systems that have been developed by Los Alamos National Laboratory as part of the SNS partnership," said Thom Mason, associate laboratory director for SNS at Oak Ridge. "It is the culmination of years of hard work and we look forward to more successes as we proceed to higher energy and beam power over the next several months."
Rej said the successful test confirmed the performance of the beam generated and accelerated in the SNS front end. Acceleration at small intensities through the first Los Alamos drift-tube linac showed 100 percent transmission of the beam, which was a second crucial milestone.
Making sure the diagnostic instruments worked properly was crucial to the test, Rej added.
"We had to confirm that the beam traveled down precisely the right path," he said. "Misalignment could have damaged the components or made them radioactive."
When completed, about 450 workers will staff the SNS project, and thousands of materials scientists, chemists, physicists and other researchers from around the world will run experiments there.
The overall SNS budget is $1.4 billion. Oak Ridge National Laboratory is leading the effort, and Los Alamos' share of the work totals about $200 million. Other members of the SNS partnership are the Argonne, Brookhaven and Lawrence Berkeley national laboratories and the Thomas Jefferson National Accelerator Facility.
Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is operated by Los Alamos National Security, LLC, a team composed of Bechtel National, the University of California, The Babcock & Wilcox Company, and Washington Group International for the Department of Energy's National Nuclear Security Administration.
Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.