EDITORS: Color photographs of the 20-meter-long laser pulse channel and high intensity electron beams generated by U-M researchers are available on request.

ANN ARBOR— Scientists at the University of Michigan are trying to put the power of advanced laser technology to work in table-top particle accelerators, which they believe may soon become as common in scientific research laboratories as the electron microscope. Just as advances in computer technology freed scientists from dependence on mainframes, U-M scientists believe new developments in the design of high-peak-power laser accelerators could reduce the need for massive, multi- million-dollar facilities like Stanford University’s Linear Accelerator Center Physics (CERN). ” Once we perfect the ability of these devices to accelerate electrons, they could revolutionize X-ray technology and particle physics,” said Donald Umstadter, associate research scientist in the U-M Center for Ultrafast Optical Science, which is funded by the National Science Foundation.

The development of chirped pulse amplification (CPA) in 1987 started a revolution in laser technology by making it possible to generate very short laser pulses with peak powers as high as 100 trillion watts. That’s the equivalent of 200 times the total electric power generation capacity of the United States, according to Gerard Mourou, director of the U-M center. ” By focusing all this power on a spot many times smaller than the period at the end of this sentence, we can produce laser beams of enormous intensity,” Mourou explained. ” The electric field surrounding this focal spot is strong enough to trap sub- atomic particles like electrons and accelerate them to high energies within just a few centimeters, instead of many kilometers as in conventional particle accelerators.” U-M researchers have already overcome several of the technological hurdles that prevent today’s scientist from equipping his or her laboratory with a table-top accelerator, according to Umstadter.

In a series of 1995 experimental and theoretical studies with chirped pulse amplification lasers, U-M scientists have conceived an electron accelerator capable of producing the shortest electron pulses on record and accelerating them to the highest energy with the least laser power, according to Umstadter. U-M scientists have demonstrated the potential of this technology by producing the first ” naturally” collimated or organized beam of electrons accelerated by a laser alone.

In this experiment, which was reported at the November 1995 Division of Plasma Physics meeting of the American Physical Society, U-M scientists ran laser pulses through a gas jet to produce a plasma wave capable of accelerating electrons to energies of one-billion electron-volts in a distance of one centimeter. In related work during the past year, researchers at the U- M center have demonstrated two methods of extending laser beams beyond their natural focal distances. In the first experiment, also reported at the November 1995 APS meeting, U-M scientists used a technique called relativistic self-focusing to generate the highest focused laser intensity ever produced in a laboratory and to create a channel extending the distance over which electrons were accelerated.

In another experiment, reported in the Jan. 5, 1996, issue of Science, U-M scientists produced a self-channeling, low-energy beam of laser light 80 microns in diameter that extended for more than 20 meters. ” One of our ultimate goals is to propagate high-energy beams over long distances,” said Umstadter, who predicts an explosion of applications for laser-based accelerators within the next few years” not just in physics, but in medicine, biology and chemistry, as well. ” Once we discover how to use these optical channels to accelerate electrons over longer distances, it may be possible to generate energies equivalent to today’s most powerful conventional particle accelerators with a compact, relatively inexpensive laser accelerator.”

Research at the U-M Center for Ultrafast Optical Science is funded in part by the National Science Foundation. Others collaborating in the research program include Anatoly Maksimchuk, engineering research associate; and U-M graduate students Alan Braun, Szu-Yuan Chen and Robert Wagner.

Center for Ultrafast Optical ScienceGerard MourouAmerican Physical SocietyNational Science FoundationAnatoly Maksimchuk