Soviets Tour ‘Star Wars’ Test Plant : National security: The visit caps arms negotiations in Geneva.

Under heavy security, a 10-member delegation of Soviet scientists and arms negotiators broke new ground in East-Wast relations on Saturday by touring a vital component of the United States’ “Star Wars” research.

The high-level Soviet visit to the 2,770-acre TRW Inc. laser testing facility, nestled in grassy hill country one mile north of San Clemente, capped months of planning between Soviet and American arms reduction negotiators.

“The Soviet delegation was very pleased and interested in the tour,” said a senior Bush Administration official who attended the precedent-setting visit to a U.S. laboratory conducting sensitive research on the controversial Strategic Defense Initiative.

He added that the visit “went a long way to demonstrating the value” of a new atmosphere of scientific cooperation that is being proposed in ongoing arms reduction talks in Geneva.

The official, who asked not to be identified, was referring to a U.S. proposal that was put on the table in Geneva about two weeks ago. The proposed new Defense in Space Treaty would set up new ground rules for the development of space-based defense systems.

One of the elements of the proposal is reciprocal laboratory visits. U.S. officials believe that the visit will set the stage for annual data exchanges between the two superpowers and will persuade the Soviets of the value of regular laboratory visits.

First announced in September, Saturday’s tour and inspection of the “Alpha” chemical laser system was billed as an extension of the Geneva strategic arms reduction talks, Marine Lt. Col. Alan R. Freitag said.

Other than holding an impromptu press conference when the Soviets arrived Friday at the Marine Corps Air Station in El Toro, organizers of the tour maintained strict control over information about the tour. Neither the press nor local officials were allowed to accompany the group Saturday.

Officials have even declined to say where the visitors spent the night on Friday, or whether they returned to the Marine base after the tour of the plant, located on unincorporated land at the end of Avenida Pico.

The TRW facility is home to the “Alpha” chemical laser, a component of SDI’s “Zenith Star” program, company officials said. Under the Zenith Star program, American researchers are hoping to develop a satellite-based laser that will detonate nuclear warheads in mid-trajectory.

From the laser testing facility, the Soviet group was expected to move on to tour the Los Alamos National Laboratory in New Mexico, another center where SDI research is being conducted.

At Los Alamos, the Soviets will examine the Beam Experimental Aboard Rocket, a project that is developing rocket-mounted devices that will generate powerful beams of atomic particles. The particle beams will be able to either identify or destroy incoming missiles.

Whisked into Orange County without any fanfare, the Soviets, led by Ambassador Yuri Nazarkin, head of the Soviet delegation to the strategic arms and space defense talks in Geneva, were briefed by American scientists, company executives and military personnel at 8:45 a.m., said Julie Wright, director of public affairs for TRW Inc.

“It was a very good exchange,” Wright said about the morning-long meeting. After lunch, she said, the 30-member contingent of scientists, government representatives and military personnel boarded a bus and drove for five minutes to the laser testing site that is built on a corner of the sprawling facility.

Once there, the group examined parts of the Alpha laser testing equipment for about three hours, she said. Dressed in sterile “bunny suits,” the Soviets climbed inside a 50-foot-tall vacuum chamber that houses the high-power chemical laser, Wright said. The vacuum chamber simulates a space environment.

The group then returned to the center’s main building for a “wrap-up” and left the site at 4:15 p.m., Wright said.