The Stanford linear accelerator will be closed for at least two days after a bolt of electricity torched a technician yesterday.

The worker was installing a circuit breaker near an electrical panel in the two-mile-long particle accelerator around 11:15 a.m. when “for some reason we have not yet ascertained, an electrical arc passed from the circuit breaker to the panel,” said Stanford Linear Accelerator Center spokesperson Neil Calder. “He was not electrocuted, but the arc ignited his clothes and he was thrown over backwards.

“He was wearing safety gloves, glasses, thank God, a head scarf and boots,” Calder added.

Two other technicians quickly rolled him over and smothered the fire, and nothing else was damaged, Calder said.

Calder did not release the victim’s identity but said he was a contract worker, not a SLAC employee.

He was taken to the burn unit at Valley Medical Center in San Jose with second- and third-degree burns on his legs and upper body, Calder said.

The temporary closure probably will not affect research at the accelerator: It was only recently turned back on after a routine “shutdown period” for maintenance, and a new round of experiments is not scheduled to start until later this week, Calder said.

Accidents are rare at the facility, one of the world’s leading centers for particle physics research. Calder said the last injury at SLAC occurred in January when a worker fell off a ladder.