|Fig. 1: President Reagan Addresses the United States of America from the Oval Office on National Security and the Strategic Defense Initiative. (Source: Wikimedia Commons)|
In 1963, L. Herwig proposed the nuclear pumped laser, based on the idea that the ions produced from nuclear reactions can be used as a driver for the laser medium. Since high power and high efficiency lasers with short wavelengths require high pumping power densities, nuclear pumping is an extremely appealing method. Nuclear pumped lasers could therefore direct significant amounts of energy emitted in a nuclear explosion into a very narrowly collimated beam. This beam would not only be able to destroy or damage targets from very long ranges, but also preclude subsequent use due to its own self-damaging mechanism to the initial weapon.  This system would ultimately constitute "a 'third generation' of nuclear weapons, the first two generations being the atomic (fission) and the hydrogen (fusion) bombs," according to Edward Teller, also known as "the father of the hydrogen bomb".  In this sense, it would be able to target energy toward specific targets instead of spreading energy into all directions.
On March 23, 1983, President Reagan announced plans to build a defensive Anti Ballistic Missile (ABM) system to protect against a potential intercontinental ballistic missile attack on the United States (Fig. 1). The Strategic Defense Initiative (SDI) program outlines a multilayered defense system. The first line of this defense aimed to destroy missiles in their boost phase just after launch, with a candidate for this first line being the nuclear-explosion-pumped X-ray laser. 
|Fig. 2: An artistic representation of space-based ballistic missile defense nuclear pumped laser system. It simulates what an Excalibur firing at three target warheads. (Source: Wikimedia Commons.)|
This prompted two major efforts by the Strategic Defense Initiative Organization (SDIO) - the Centaurus program and the Falcon program.  Centaurus was a collaborative research effort between the Idaho National Engineering Laboratory and the Lawrence Livermore National Laboratory while Falcon was based on the research at the Sandia National Laboratory, both programs aiming to create a laser platform using the high-energy and high-power capability of nuclear pumped laser technology.  While there remains limited information and published data from the Centaurus program, it is known that the Falcon involved using "various mixtures of xenon, argon, neon, and helium at wavelengths of 585, 703, 725, 1271, 1733, 1792, 2032, 2630, 2650, and 3370 nm with intrinsic efficiency as high as 2.5%".  The location of these nuclear pumped laser weapons was also explored between space-based BDM systems, earth-based systems and a pop-up system. The space-based BMD system remained the most obviously advantageous due to its position to provide an almost immediate response to any detected attack.  Fig. 2 shows an artist's rendition of a potential space-based BMD nuclear pumped laser defense under the Lawrence Livermore National Laboratory's Excalibur research program.
Yet, by 1985, tests showed that the beams were unsuccessful and there was a growing sense that the Strategic Defense Initiative needed to turn to other strategies and options for nuclear defense. However, underground tests of nuclear pumped lasers continued to take place until 1992. 
While nuclear pumped laser research has historically been dominated by the military applications, there also exists noteworthy non-military, humanitarian applications for such high power lasers. For example, nuclear pumped laser technology is extremely promising in potentially deflecting asteroids, particularly because of its ability to beam energy on it at a high enough intensity to cause "ablation of matter".  Other applications for nuclear pumped laser technology to explore in the future include space propulsion, power transmission and asteroid mining. 
© Claire Zau. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
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