pPYRGHIA~Fg,g K/ / /?j s-Ae " P721 &aIry ~ llplk_~ A L 11P ZLI "A r e~q ~~OtJ819'24'CILRW aIrR!S W.JL ~, L Sel-, 0 ~war soin rk cognarf un o E ",uw L U WHITE SANDS MISSILE RANGE, N.M. -The nation's first :,,round-based, free-electron la- ser, perhaps the precursor to weap- c)ns that could strike enemy mis- iiles as they rise from their launch pads, is under construction. The $1.7 billion Strategic De~~ fense Initiative project managed by the.Army's Strategic Defense Command. could develop the tech- nology for a key element in a com- plex of strategic defense systems which could defend either the United States or its allies. About 20 miles east of White Sands'main post a wide drive an- gles away from the main road deep into the desert scrub brush. Culverts fordrainage, a drilling derrick for waterwells, power lines and bt1ii1ding excavations line the way to an expanding rectangle of cleared land that marks the site for an ambitious experiment in ]a- sertechnology. According to treaties with the Soviets, White Sands and the Pacif- ic atoll of Kwai'alien are the two U.S. testing ranges designated for strategic defense Pxperiments. After a series of environmental studies, the 20 square-mile Oro Grande location was selected. "We have to bring in water, power [about f ive times what all of White Sands presently uses] and roads - build a whole research complex," said Col. Jamei F. McNulty, head of the GBFEL tech- nology i ntegration experiment McNulty is a tall, silver-haired f ield artilleryman who served two tours of duty in Vietnam, but who a Iso found time between field as- signments to study at a half-dozen prestigious institutions, including assachusetts Institute of Tech- nologyand Lawrence Livermore National Laboratory, where he gathered advanced degrees in nu- ,-1ear physics and management . before receiving his present assign- ,nent in January 1986. His first months on the job were spent attending the Defense Systems Management College at Fort Belvoir, Va., during the week and traveling around the country trying to organize the project on weekends. His staff has groWn from zero to 42 in the firstyear and a half although, he said, laser and optical experts are a rarity. I "It is exciting," he said. "I start- ed with absolutely nothing but a piece of paper. [Lt.] Gen. [John] Wall [commander of the Washing- ton-based SDC] said to me,'Don't come back until it works."' While the project is seen as an experiment and not a weapon sys- tem, it is aimed at a well-defined military end. The Army has defense applications for the technology if it is approved for further develop- mentAPOOMOWP&~eleag government It is part of a futuristic trend that will place the American soldier farther from his enemies, but will at the same time extend the strate- gic battlefield, McNulty said. -A ground-based I~ser, if used in in a weapon system, would work in r conjunction with a relay mirror it in stationary (geosychronous) orbit ,)~rb over the laser site, and fighting mirrors orbiting over areas such as the Soviet Union that might be expected to launch missiles. The la- ser beam, generated on the ground and reflected over tens of thousands of kilometers by mir- rors, would focus on and destroy tar- gets such as the ballistic missile and the "buses" that can carry 10 to 15 warheads plus dozens of decoys. %_1000 intepretation of the ABM treaty, work on the free-electron laser can go ahead, because it is a fixed, ground-based element and there- fore "treaty compliant." Application of the treaty to the mirrors being developed by other Army and Air Force teams is understudy. Interestingly enough, even MeNulty doesn't know what the fl- nal design of the laser will look like. It could be either a long, straight structure (the induction laser proposed by TRW and Law- rence Livermore National Lab- oratory) or a more compact race- track design (the radio frequency [RFI laser proposed by BoeingAero- space Co. and Los Alamos Na- tional Laboratory). The final choice is to be made by the end of fiscal 1988. i-CUFAMIkIM VM6003-2 generation of a stream of electrons, the charged particles that vibrate around the nucleus of an atom. The electrons are injected into a charged medium, stripped from their atoms (thus the name free- . electron) and then accelerated to near the speed of light The induction lacer uses the magnetic fields produced by large magnets to speed up the elec- trons; the RF laser employs radio waves pumped into resonant cav- ities to do the same thing. The speeding electrons are then passed through a device with varying magnetic fields which are used to make the electrons oscillate or move back and forth, hence the box is known as a "wiggler." Each time the electron wiggles, See LASER, Page 40 An artist's conception of the Ground Based Free Electron the foreground. An underground tunnel takes the laser Laser experiment now under construction at White Sands beam to the opposite end of the facility (3 to 5 kilometers Missile Range shows the facilities for forming the beam in away) for transmission into space. 'Approved For.R616.1se 2000/68/08 :,CIAmROP! CPYRGHT Sandia National Laboratories Photo An 8-inch howitzer used by scientists at Researchers there are using technology Sandia National Laboratories shoots a new developed in the nuclear weapons program shell design through monitored targets. to create improved conventional weapons. said Max Newsom, manager of the partment. It advanced projects de liuse combill"aon vWul?ppeiroov"ZIP2 a wide range of options that for ex- ample, could reduce the mili- tary s logistics tail and at the same time improve the weapon's effectiveness. 10W -5ju. "Advanced conventional muni- tions are of increasing na~onal im- portance and we have only scratched the surface of their poten- tial capability," Newsom said. Sandia is not operating on an unlimited budget, however, and the See SANDIA, Page 42 Laser From Page 35 photons. tiny particles of light are produced. Through subsequent stimulation of the electrons by the photons, up to 40 percent of the electron beam's energy is extracted to produce the high power laser beam. In the hiduction device, a small "seed" laser, operating at a pre-de- termined frequency, is fired into a 100-foot-long wiggler. The seed la- ser is amplified as energy is ex- tracted from the electron beam and converted to light energy at the same frequency as the seed laser. The electron beam, as it exits the wiggler, is quickly separated and discarded so that only the laser beam goes on to the optical system. The laser beam is focused to about the diameter of a pencil, is then allowed to expand (to about one meter) naturally in a vacuum as it moves through a 3- to 5-kilome- ter-long beam tunnel. It must ex- pand, otherwise, the focused beam is powerful enough to blow apart the mirror designed to di rect it into space. The RF concept does not use a seed laser. The light produced by the electron beam is reflected back and fo rth in the wiggler be- tween sets of mirrors (called a ring resonator and the size of a foot crating ball field), each time gene more photons and f' inally being al lowed to escape through a hole in the mirror to the optical systern. In December, a request for pro- posals will be sent out to industry from the ground-based laser pro- j ect office. In February, industrial competitors will submit their plans and designs. And in June, MeNulty and his team will pick the winner. "Each team has technical mile- stones to meetbefore the decision is made," McNulty said. He noted that even then the team still won't know for sure if the design works. "But we will at least know what the unknowns are," McNulty said. One of those unknowns is how to keep the electron and light beams stable and straight in the long wiggler of the induction laser. "In the optical guidance scheme, the electrons ride in a trough, or tunnel, of light," McNulty said. The packets of elec- trons and li-~,it must be exactly in synchronization. If we can't keep them in the trough, we will never have the efficiency we need. We should have evidence by the end of December if it can work." The RF laser also has its prob lems. Using mirrors to multiply the light forces researchers to the ragged edge of technology. The needed lenses (mirrors) have to be of two types: paraboloid and hyper-paraboloid. The paraba- loid has an off-center focus. The by- perparaboloid is specially de- signed for reflections at glancing grazing angles. "Where we can't put light di- rectly onto a mirror, we skip it off," McNulty said. Both types of mirrors are nee- essary for the RF laser to work Both have been designed and are in the final stages of fabrication, but remain to be tested. The testing is scheduled for December and January. After the laser beam is generat- ed it has to be controlled in a vacu- um and then shaped and correct- ed for atmospheric effects before it is reflected into space from a ground mirror. Reseaehers have the --formidable task of building a -meter-wide mirror to direct four the beam. There also is a "signifi- cant engineering challenge" to use a single aperture to receive the beacon beam coming down and transmit the weapon beam going up, McNulty said. There are some more knotty problems with using lasers in the at- mosphere over long distances. uj 40 gj Igo." NN~ 'k U, -7, *~ etilr~ ~K, r'Q;, -a, v-, V.771t:' 94- IV M 27" #Lip 4', 6L 7_ 7" ~,*M A ot R, R`_ Eli, ~7 T, K__ Mmm White Sands Missile Range illustration Turrets will house the control system that of mirrors based in space. Ultimately it will AP0r6w9dsFeinRe*dsadIft00f*W08-, CPA-FkVPW0Q78VFWW~Nl146ft" manufactured laser beam toward a system destroy them. "Laserbeams don't like air," MeNultysaid. Turbulence, water, dust or eddy currents in the atmosphere can affect a laser beam just as fog can disperse a light beam. Also, a laser beam heats the air through which it travels. That causes the air density to change, which bends the laser beam and produces"thermal blooming," which once again dissipates its power. Finally, nitrogen in the air ab e photons, or particles of sorbsth light, that make up a laser beam. Nitrogen alters the wave lengths of the light and spits it out in other directions. "Those are the three things we have to overcome," he said.