- Number 364 |
- June 4, 2012
CEBAF upgrade test a success
Jefferson Lab's CEBAF accelerator,
is shown during installation.
DOE's Jefferson Lab is in the midst of a $310 million upgrade project to provide physicists worldwide with an unprecedented ability to study the basic building blocks of matter. Now, key components of the upgrade to the lab’s particle accelerator have aced a rigorous test conducted under real operating conditions, confirming that the newly designed, state-of-the art components meet specification.
The lab's CEBAF accelerator delivers beams of electrons for probing the protons, neutrons, quarks and gluons in the nucleus of the atom. The upgrade will enhance the research capabilities of the accelerator by doubling the energy of its electron beam from 6 billion electron-Volts (GeV) to 12 GeV, along with other upgrades and additions. To increase the energy of the CEBAF accelerator, 10 new sections, called cryomodules, will be added.
Last fall, the first two of the new cryomodules were installed, along with the new microwave-power sources needed to power them. Since October, the two have been operated along with the accelerator's more than 40 original cryomodules, delivering electron beam for the lab’s experimental program.
One of the new cryomodule-plus-microwave systems was given a chance to shine on April 26, when accelerator operators ran the first full operational tests, while also delivering high-current beam.
For the test, operators ramped up the microwave-power system that powers the cryomodules. The voltage hit 98 Megavolts (98 million volts), the value that each of the 10 new cryomodules will need to provide in order to accelerate an electron beam to 12 GeV. The system reached this base specification and maintained the performance for more than an hour without faulting or developing a problem that would cause the electron beam to automatically trip off. The tests were conducted at the highest beam power anticipated for the planned research program.
"This test has demonstrated that the integrated cryomodule plus microwave-power system can successfully deliver the performance that was envisioned in 2001, and which is needed for the planned nuclear physics research program in the 12 GeV era," said Leigh Harwood, associate project manager for the 12 GeV Upgrade project. "The critical new technology for upgrading the accelerator to 12 GeV is now a demonstrated fact."
"This is the first time that we were able to demonstrate performance with a real beam. And we were delivering the highest-quality, parity beams to all three halls during this period of time. So, they are not just performing, they are performing to all of the requirements that we know how to put on," said Andrew Hutton, Jefferson Lab associate director of the Accelerator Division.
Further tests of the one cryomodule, dubbed SL-25 for its current location in the accelerator, later surpassed the base specification. The cryomodule voltage was increased in 2 Megavolt steps to 104 Megavolts, while the cryomodule continued to deliver high-current beam, demonstrating that capability for more than an hour. A later test, performed May 18, achieved high-current running at 108 Megavolts for a full hour, meaning the cryomodule performed more than 10 percent better than its base specification, meeting the desired performance goal for providing highly reliable, high-energy operation.
"The base specification is that it should be able to produce 98 Megavolts, but everything is sized 10 percent bigger than that, such that if there were to be a weak cavity, the others could be pushed, which is in fact what we did during this test," Hutton explained. "This achievement is a credit to the teams that designed, built, installed and commissioned the cryomodules, the microwave systems and controls."
Further testing of either of the two installed cryomodules was curtailed due to time constraints.
Meanwhile, Jefferson Lab is moving forward with work to upgrade the accelerator. At 8:18 a.m. on May 18, the accelerator was shut off to allow the upgrade to proceed. The upgrade entails the installation of additional cryomodules, microwave systems, arc magnets and other components. Already complete is the construction of a fourth experimental hall, a 250-foot extension to the lab's underground accelerator tunnel, and new utilities; installation of the detector system in that fourth hall has already begun.
The 12 GeV Upgrade project is expected to be completed in 2015.
[Kandice Carter, 757.269.7263,