Something unwanted lurks within accelerator beam pipes around the world: stray electrons. This haze of electrons interacts with positron and proton beams, often distorting them. Recent tests carried out at the Japanese accelerator facility KEK, however, confirm that a new insert designed by SLAC National Accelerator Laboratory researchers for the KEK beam pipe can reduce this electron cloud effect.
The tests show that triangular grooves on the beam pipe's interior surface trap stray electrons, reducing the number of electrons in the cloud by up to a factor of 10. (Read more about the design in "Don't Rain on My Parade" and more about the fundamental problem in the symmetry feature "Battling the Clouds.") The test results indicate a significant overall decrease in the number of electrons in the beam pipe. Better yet, the number of electrons detected continued to decrease over the duration of each test, suggesting that the electron cloud will continue to shrink over even longer periods of time.
"The tests went great," said SLAC researcher Mauro Pivi, who designed the new beam pipe with SLAC's Lanfa Wang, working with KEK physicists Yusuke Suetsugu and Hitoshi Fukuma. "This is a very good start, and we look forward to even better results as we optimize the design."
As Pivi notes, this is just the beginning of many rounds of testing. Later this year, slightly modified versions of the grooved beam pipe--this time with smaller grooves and an enhanced coating of titanium nitride to reduce the number of electrons produced--will be sent to KEK, the European accelerator laboratory CERN and the Cornell Electron Storage Ring Test Accelerator to be tested in different magnetic environments.
This story first appeared in SLAC Today on January 27, 2009.