Linear Collider Passes 2 Major Milestones : Scientists Testing Electron Accelerator Say It Set Energy Record

Times Science Writer

At least two months before it is expected to achieve full operation, the Stanford Linear Collider has passed two major milestones, including reaching energies far greater than any other electron accelerator in the world.

The successes have provided a little breathing room for scientists here who do not yet know whether their bold experiment will actually work. The collider, a radical new design created by Nobel laureate Burton Richter, is scheduled to go into operation sometime in June after scientists finish "fine-tuning" it, Richter said at a press briefing Wednesday.

Reputation on the Line

Richter, one of the world's top experts on high-energy physics, has staked his reputation on the new machine, built at a fraction of the cost of its major competitor now under construction near Geneva, Switzerland, and designed to achieve the same goals. Both machines are expected to shed new light on the weak force of the atomic structure, the force that is so weak it allows some elements to decay into others, thus releasing radiation.

Scientists here announced Wednesday that about a month ago electrons passing through the accelerator during test runs achieved energies of 53 billion volts, more than enough to accomplish the objectives of the machine providing other criteria can also be met.

"That's a world record," said physicist John Rees.

Sitting in one corner of the briefing room, and using a small calculator, Richter figured out that such a high level of energy is equivalent to "a stack of flashlight batteries more than a million miles tall."

"That's four times higher than the distance to the moon," he said.

Any moving particle, including a baseball thrown across a sand lot, has energy, Richter said. And although electrons are among the smallest particles in the universe, if they can be accelerated fast enough, the energy represented by a single moving electron can be enormous.

Near Speed of Light

In its test run, the electrons were accelerated to near the speed of light.

A second major milestone was passed March 27 when scientists managed to get two beams of electrons and positrons traveling in opposite directions to cross each other, a key element in making the machine work.

None of the particles collided during that test because the beams were too broad, thus allowing the particles to pass each other unperturbed, but it was a high point for scientists working with the linear collider.

"People were jumping up and down and running around," said physicist Roger Erickson.

The next major hurdle will be to condense those beams to about one-tenth the thickness of a human hair and focus those smaller beams so that they will cross each other, thus allowing some electrons to collide with positrons.

"So there is a good deal of fine-tuning still remaining," Rees said.

If they succeed, the collision should yield Z particles. The Z particle is believed to be the subatomic particle that carries the weak force.

Each collision, called an "event," should produce Z particles, and Richter is hoping for 500 to 1,000 events by October of this year.

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