X-Ray Laser

The concept for x-ray lasers goes back to the 1970s, when physicists realized that laser beams amplified with ions would have much higher energies than beams amplified using gases. Nuclear explosions were even envisioned as a power supply for these high-energy lasers. That vision became a reality at the time of the Strategic Defense Initiative of the 1980s, when x-ray laser beams initiated by nuclear explosives were generated underground at the Nevada Test Site. From fiscal years 1986 through 1993, SDI0 spent $138 million for nuclear directed energy technology.

The Lawrence Livermore program to research nuclear-pumped x-ray laser systems accelerated after President Reagan's "Star Wars" speech to introduce the Strategic Defense Initiative (SDI) in 1983. Teller thought such a laser system would provide a shield for the United States against Soviet missiles. He championed the x-ray laser effort and numerous other R&D activities, including guided antimissile missiles called Brilliant Pebbles.

Livermore's Novette, the precursor of the Nova laser, was used for the first laboratory demonstration of an x-ray laser in 1984. In the early 1980s, researchers were exploring how to produce x-ray laser beams initiated by nuclear explosives at the Nevada Test Site. At the same time, success was achieved creating a soft-x-ray (about 200 angstroms) laser in a laboratory setting using the Novette laser, which was a test bed for the design of Nova. Nova became operational in December 1984.

One of the weapons that had been considered under President Reagan’s SDI program was a nuclear powered X-ray laser. It would have been powered by a small nuclear explosion that produced a pulse of intense X-rays. Therefore, the weapon could not be placed in orbit, installed on a celestial body, or station in space under the Outer Space Treaty. Even if the United States could use such a weapon without it being orbited, installed, or stationed in space, and thus not subject to the literal Article IV prohibitions, the United States still would have to show the world community that the spirit of the Outer Space Treaty was not violated.

In its 1984 directed energy plan, SDIO planned to pursue the development of nuclear directed energy to provide a base of knowledge that would permit the United States to better judge potential Soviet capabilities and to provide the basis for a ground-based or pop-up nuclear directed energy capability should it be needed at some point for the strategic defense system follow-on phases. SDIO'S contributions included theoretical computational research along with contributions for diagnostic packages for Department of Energy underground nuclear tests and related laboratory experiments. SDIO and the Department of Energy have conducted a cooperative program that has included mission analyses as well as exploring system engineering concerns.

Based on their understanding of the physics of an X-ray laser, LLNL scientists developed computer models, which were used with other means to predict the results of underground tests. If the results of an underground test agreed with the predictions, LLNL scientists concluded that they generally understood the physics of how the aspect being measured worked. If there were significant differences, this meant that the physics were not well understood. In general, quantitative means that the results were "close" to the predictions, and qualitative means the results were "not as close."

The X-ray laser is important to the SD1 program because the final SD1 design could depend upon whether the x-ray laser is feasible. If the Soviets could build an X-ray laser, then the survivability of American space assets could be questioned. Therefore, the United States would have to design its ballistic missile defense system to either survive or counter a Soviet X-ray laser attack. X-ray lasers have several potential military applications including counter-defense, booster kill, post-boost vehicle kill, reentry vehicle kill and discrimination of reentry vehicle decoys. The technology requirements for each mission are different.

LLNL official channels, which included Mr. Roy Woodruff, former LLNL Associate Director for Defense Systems, made statements about the status and potential of the X-ray laser, which were similar to most of the statements identified by Mr. Woodruff as being "overly optimistic and technically incorrect."

The initial LLNL X-ray laser design concept was referred to as Excalibur and had an established brightness (power intensity) goal. Theoretical calculations on a different idea evolved into the Super-Excalibur concept in early to mid-1984, which had a brightness goal significantly higher than Excalibur. Brightness is the amount of power that can be delivered (per unit solid angle) by a directed-energy weapon. Brightness of the laser beam can be measured either at the laser device (source) or at the target, where the brightness would be less than at the source due to the source-target separation.

The Super-Excalibur concept “seems likely to make X-ray lasers a really telling strategic defense technology. For instance, a single X-ray laser module the size of an executive desk which applied this technology could potentially shoot down the entire Soviet land-based missile force, if it were to be launched into the module's field of view." (letter to Nitze from Teller) According to LLNL Director, Dr. Roger Batzel, there was nothing in Dr. Edward Teller's letters that violated any laws of physics. In addition, Dr. Teller identified the Super-Excalibur concept as "in principle," and the letters contained many qualifiers.

Although Super-Excalibur was conceptually much simpler, the physics may prove to be more difficult. According to Mr. Woodruff, the statement concerning the number of independently aimable beams was an example of Dr. Lowell Wood “selling Super-Excalibur." He also felt that Dr. Wood's use of artist's drawings depicting possible x-ray laser usage implied an unwarranted reliability to something that did not exist other than as a theoretical calculation.

There are four properties of the x-ray laser that determine its performance: (a) the total power in the laser beam; (b) the color of the laser light; (c) the size or spreading (divergence) of the laser beam; and (d) when the laser beam turns on and how long it lasts. The measurement of these properties is a difficult task because of the nuclear environment, and the high intensity, short timescale of the 1asing process. There was no “design flaw” in these experimental measurements. The high intensity laser pulse interacts strongly with the measuring device during the time of observation. A scientific question was how accurately DOE could make the measurements and, thus, whether the quoted absolute power was correct.

1978 Diablo Hawk--failed test of x-ray laser
November 1980 Dauphin-test including Hagelstein's design
March 1983 Cabra x-ray laser test-failure because data garbled
December 1983 Romano test-length of rods vs. gain showed x-ray lasing
August 1984 Correo Test by Los Alamos-false brightness from interaction of sensors with bomb
March 23, 1985 Cottage test-one sensor modified to look at brightness problem-Teller hailed as success
December 1985 Goldstone test in spite of bent canister showed brightness less than expected by factor 10
September 1986 Labquark - focusing seemed to work