National Ignition Facility
337301
225204713
2008-07-12T13:16:18Z
AssegaiAli
5505831
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[[Image:NIF building layout.jpg|thumb|right|400px|NIF's basic layout. The laser pulse is generated in the room just right of center, and is sent into the beamlines (blue) moving into the amplifiers at the top (purple). After several passes through the amplifiers the light is cleaned up in the filters (blue) and sent into the "switchyard" (red) where it is aimed into the target chamber (silver). In the upper left is the assembly plant for the optical glass.]]
The '''National Ignition Facility''', or '''NIF''', is a [[laser]]-based [[inertial confinement fusion]] (ICF) research device under construction at the [[Lawrence Livermore National Laboratory]], in [[Livermore, California]], [[United States]]. NIF uses powerful lasers to heat and compress a small amount of [[hydrogen]] fuel to the point where [[nuclear fusion]] reactions take place. NIF is the largest and most energetic ICF device built to date, and the first that is expected to reach the long-sought goal of "ignition", when the fusion reactions become self-sustaining.
Construction started in 1997 but was fraught with problems and ran into a series of delays that greatly slowed progress into the early 2000s. Progress since then has been much smoother, but compared to initial estimates, NIF is five years behind schedule and almost four times more expensive than budgeted. By August 2007, 96 of the lasers (out of a planned 192) had been completed and commissioned, with a further 48 (for a total of 144) nearing completion. As of June 2008, construction of the NIF is estimated to be completed in March 2009 and that ignition (more energy coming out than what is put in) can be achieved by 2010.<ref>{{cite news | last = Trimble | first = Tyghe | title = The Laser to End All Lasers | publisher = Discover | date = [[2008-06-25]] | url = http://discovermagazine.com/2008/jul/25-the-laser-to-end-all-lasers | accessdate = 2008-07-03 }}</ref> Its price of over $4 billion and its role in [[nuclear weapon]] research has made it a controversial topic.
==Description==
===Background===
{{main|inertial confinement fusion#ICF mechanism of action|l1=ICF mechanism}}
[[Inertial confinement fusion]] (ICF) devices use "drivers" to rapidly heat the outer layers of a "target" in order to compress it. The target is a small spherical pellet containing a few milligrams of fusion fuel, typically a mix of [[deuterium]] and [[tritium]]. The heat of the laser burns the surface of the pellet into a [[Plasma (physics)|plasma]], which explodes off the surface. The remaining portion of the target is driven inwards due to [[Newton's Third Law]], eventually collapsing into a small point of very high density. The rapid blowoff also creates a [[shock wave]] that travels towards the center of the compressed fuel. When it reaches the center of the fuel and meets the shock from the other side of the target, the energy in the shock wave further heats and compresses the tiny volume around it. If the temperature and density of that small spot can be raised high enough, fusion reactions will occur.<ref name=how>"[https://lasers.llnl.gov/programs/nif/how_nif_works/ How NIF works]", Lawrence Livermore National Laboratory. Retrieved on [[October 2]] [[2007]].</ref>
The fusion reactions release high-energy particles, some of which (primarily [[alpha particle]]s) collide with the high density fuel around it and slow down. This heats the fuel further, and can potentially cause that fuel to undergo fusion as well. Given the right overall conditions of the compressed fuel—high enough density and temperature—this heating process can result in a [[chain reaction]], burning outward from the center where the shock wave started the reaction. This is a condition known as "ignition", which can lead to a significant portion of the fuel in the target undergoing fusion, and the release of significant amounts of energy.<ref name=econ>Per F. Peterson, ''[http://www.nuc.berkeley.edu/thyd/icf/IFE.html Inertial Fusion Energy: A Tutorial on the Technology and Economics]'', University of California, Berkeley, 1998. Retrieved on [[May 7]] [[2008]].</ref>
To date most ICF experiments have used lasers to heat the targets. Calculations show that the energy must be delivered quickly in order to compress the core before it disassembles, as well as creating a suitable shock wave. The energy must also be focused extremely evenly across the target's outer surface in order to collapse the fuel into a symmetric core. Although other "drivers" have been suggested, notably heavy ions driven in [[particle accelerator]]s, lasers are currently the only devices with the right combination of features.<ref>Per F. Peterson, ''[http://www.nuc.berkeley.edu/thyd/icf/target.html How IFE Targets Work]'', University of California, Berkeley, 1998. Retrieved on [[May 8]] [[2008]].</ref><ref>Per F. Peterson, ''[http://www.nuc.berkeley.edu/thyd/icf/driver.html Drivers for Inertial Fusion Energy]'', University of California, Berkeley, 1998. Retrieved on [[May 8]] [[2008]].</ref>
===Driver laser===
[[Image:NIF beamline diagram.jpg|thumb|400px|Simplified diagram of the beampath of a NIF laser beam, one of 48 similar beamlines. On the left are the amplifiers and optical switch, and on the right is the final spatial filter, switchyard and optical frequency convertor.]]
NIF aims to create a single 500 [[watt|terawatt]] (TW) flash of light that reaches the target from numerous directions at the same time, within a few [[1 E-12 s|picoseconds]]. The design uses 192 individual "beamlets", which are amplified in 48 beamlines containing 16 laser amplifiers per line, each one amplifying four of the beamlets.<ref name=how/>
To ensure that the output of the beamlines is uniform, the initial laser light is amplified from a single source in the Injection Laser System (ILS). This starts with a low-power flash of 1053 nanometers (nm) infra-red light generated in a [[ytterbium]]-doped optical fiber laser known as the Master Oscillator.<ref>P.J. Wisoff et al., ''[http://adsabs.harvard.edu/abs/2004SPIE.5341..146W NIF Injection Laser System]'', Proceedings of SPIE Vol. 5341, pages 146–155</ref> The light from the Master Oscillator is split and directed into 48 Preamplifier Modules (PAMs). The PAMs pass the light four times through a circuit containing a [[neodymium]] glass amplifier similar to (but much smaller than) the ones used in the main beamlines, boosting the nanojoules of light created in the Master Oscillator to about 6 joules. According to LLNL, the design of the PAMs was one of the major stumbling blocks during construction. Improvements to the design since then have allowed them to surpass their initial design goals.<ref>''[http://www.llnl.gov/str/Powell.html Keeping Laser Development on Target for the NIF]'', Lawrence Livermore National Laboratory. Retrieved on [[October 2]] [[2007]]</ref>
The main amplification takes place in a series of glass amplifiers located at one end of the beamlines. Before "firing", the amplifiers are first [[Optical pumping|optically pumped]] by a total of 7,680 [[Xenon flash lamp]]s (the PAMs have their own smaller flash lamps as well). The lamps are powered by a [[capacitor]] bank which stores a total of 400 [[Joule|megajoules]] (MJ) of electrical energy. When the wavefront passes through them, the amplifiers release some of the light energy stored in them into the beam. This is not a particularly efficient process and less than a quarter of the stored energy is transferred into the beam as it passes though; to improve the energy transfer the beams are sent though the main amplifier section four times, using an [[Pockels effect|optical switch]] located in a mirrored cavity. In total these amplifiers boost the original 6 J provided by the PAMs to a nominal 4 MJ.<ref name=how/> Given the time scale of a few billionths of a second, the power is correspondingly very high, 500 TW.
After the amplification is complete the light is "switched" back into the beamline, where it runs to the far end of the building to the ''Target Chamber''. The total length of the laser from one end to the other is about 1,000 feet (305 meters). A considerable amount of this length is taken up by "spatial filters", small telescopes that focus the laser beam down to a tiny point, with a mask cutting off any stray light outside the focal point. The filters ensure that the image of the beam when it reaches the target is extremely uniform, removing any light that was mis-focussed by imperfections in the optics upstream. Spatial filters were a major step forward in ICF work when they were introduced in the [[Cyclops laser]], an earlier LLNL experiment. The various optical elements in the beamlines are generally packaged into Line Replaceable Units (LRUs), standardized boxes about the size of a small car that can be dropped out of the beamline for replacement from below.<ref>Larson, Doug W. (2004). ''[http://adsabs.harvard.edu/abs/2004SPIE.5341..127L NIF laser line-replaceable units (LRUs)]'', ''Optical Engineering at the Lawrence Livermore National Laboratory II: The National Ignition Facility.'' [[DOI:10.1117/12.538467]]. Retrieved on [[May 7]] [[2008]]</ref>
Just before reaching the Target Chamber the light is reflected off various mirrors in the ''switchyard'' in order to impinge on the target from different directions. Since the length of the overall path from the Master Oscillator to the target is different for each of the beamlines, optics are used to "slow" the light in order to ensure all of them reach the center within a few picoseconds of each other.<ref>Arnie Heller, ''[https://www.llnl.gov/str/JulAug05/VanArsdall.html Orchestrating the World's Most Powerful Laser]'', Science & Technology Review, July/August 2005. Retrieved on [[May 7]] [[2008]]</ref> As can be seen in the layout diagram above, NIF normally directs the laser into the chamber from the top and bottom. The target area and switchyard system can be reconfigured by moving half of the 48 beamlines to alternate positions closer to the equator of the target chamber.
[[Image:KDP crystal.jpg|thumb|right|A large [[Potassium dihydrogen phosphate|KDP]] crystal grown at [[LLNL]] to be cut into slices and used on NIF for [[Optical frequency multiplier|frequency conversion]] from the IR fundamental line at 1053 nm to UV at 351 nm.]]
One of the last steps in the process before reaching the target chamber is to convert the infrared light at 1053 nm into the ultraviolet (UV) at 351 nm in a device known as a [[optical frequency multiplier|frequency convertor]].<ref>P.J. Wegner et al.,''[http://adsabs.harvard.edu/abs/2004SPIE.5341..180W NIF final optics system: frequency conversion and beam conditioning]'', Proceedings of SPIE 5341, May 2004, pages 180–189.</ref> These are made of thin sheets cut from a single crystal of [[potassium dihydrogen phosphate]]. When the 1053 nm (IR) light passes through the first of two of these sheets, frequency addition converts a large fraction of the light into 527 nm light (green). On passing through the second sheet, frequency combination converts much of the 527 nm light and the remaining 1053 nm light into 351 nm (UV) light. IR light is much less effective than UV at heating the targets, because IR couples more strongly with hot [[electrons]] which will absorb a considerable amount of energy and interfere with compressing the target. The conversion process is about 50% efficient, reducing delivered energy to a nominal 1.8 MJ.<ref>Bibeau, Camille; Paul J. Wegner, Ruth Hawley-Fedder ([[June 1]] [[2006]]). "[http://lfw.pennnet.com/Articles/Article_Display.cfm?Section=ARTCL&ARTICLE_ID=257238&VERSION_NUM=3&p=12 UV SOURCES: World’s largest laser to generate powerful ultraviolet beams]". ''Laser Focus World''. Retrieved on [[May 7]] [[2008]].</ref>
One important aspect of any ICF research project is ensuring that experiments can actually be carried out on a timely basis. Previous devices generally had to cool down for hours to allow the flashlamps and laser glass to regain its shape after firing caused thermal expansion, limiting use to one or fewer firings a day. One of the goals for NIF is to reduce this time to 5 hours, in order to allow 700 firings a year.<ref name=performance>''[https://publicaffairs.llnl.gov/news/news_releases/2003/NR-03-06-01.html NIF Project Sets Record for Laser Performance]'', Lawrence Livermore National Laboratory, [[June 5]], [[2003]]. Retrieved on [[May 7]] [[2008]].</ref>
===NIF and ICF===
[[Image:Fusion microcapsule.jpg|150px|thumb|right|NIF's fuel "target", filled with either D-T gas or D-T ice. The capsule is held in the hohlraum using thin plastic webbing.]]
The name "National Ignition Facility" refers to the goal of "igniting" the fusion fuel, a long-sought threshold in fusion research. In existing (non-weapon) fusion experiments the heat produced by the fusion reactions rapidly escapes from the plasma, meaning that external heating must be applied continually in order to keep the reactions going. Ignition refers to the point where the energy given off in the fusion reactions currently underway is high enough to cause fusion reactions in the surrounding fuel. This causes a chain-reaction that allows the majority of the fuel to undergo a nuclear "burn". Ignition is considered a key requirement if [[fusion power]] is to ever become practical.<ref name=econ/>
NIF is designed primarily to use the ''indirect drive'' method of operation, in which the laser heats a small metal cylinder instead of the capsule inside it. The heat causes the cylinder, known as a ''[[hohlraum]]'' (German for "hollow room", or cavity), to re-emit the energy as intense [[X-ray]]s, which are more evenly distributed and symmetrical than the original laser beams. Experimental systems, including the [[OMEGA laser|OMEGA]] and [[Nova laser]]s, validated this approach through the late 1980s.<ref>J.D. Lindl et al., ''[http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHPAEN000011000002000339000001&idtype=cvips&gifs=yes The physics basis for ignition using indirect-drive targets on the National Ignition Facility]'', Physics of Plasmas, Vol. 11, February 2004, page 339. Retrieved on [[May 7]] [[2008]].</ref> In the case of the NIF, the large delivered power allows for the use of a much larger target; the baseline pellet design is about 2 mm in diameter, chilled to about 18 degrees above [[absolute zero]] and lined with a layer of solid [[deuterium]]-[[tritium]] (DT) fuel. The hollow interior also contains a small amount of DT gas.
[[Image:Nif hohlraum.jpg|150px|left|thumb|The gold plated ''hohlraum'' designed for the NIF.]]
This conversion process is fairly efficient; of the original ~4 MJ of laser energy created in the beamlines, 1.8 MJ is left after conversion to UV, and about half of the remaining is lost in the x-ray conversion in the hohlraum. Of the rest, perhaps 10 to 20% of the resulting x-rays will be absorbed by the outer layers of the target (see image below).<ref name=gain>Suter, L.; J. Rothenberg, D. Munro, et al., "[http://www.llnl.gov/tid/lof/documents/pdf/237134.pdf Feasibility of High Yield/High Gain NIF Capsules]", Lawrence Livermore National Laboratory, [[December 6]], [[1999]]. Retrieved on [[May 7]] [[2008]].</ref> The shockwave created by this heating absorbs about 140 kJ, which is expected to compress the fuel in the center of the target to a density of about 1000 g/mL;<ref name=density>Lindl, John, "[http://www7.nationalacademies.org/bpa/PLSC_Sept05_Presentation_Lindl.pdf NIF Ignition Physics Program]". Lawrence Livermore National Laboratory, [[September 24]], [[2005]]. Retrieved on [[May 7]] [[2008]].</ref> for comparison, [[lead]] has a normal density of about 11 g/mL. It is expected this will cause about 20 MJ of fusion energy to be released.<ref name=gain/> Improvements in both the laser system and hohlraum design are expected to improve the shockwave to about 420 kJ, in turn improving the fusion energy to about 100 MJ.<ref name=density/> However the baseline design allows for a maximum of about 45 MJ of fusion energy release, due to the design of the target chamber.<ref name=target>M. Tobin et all, ''[http://www.osti.gov/bridge/servlets/purl/10173645-oQwjVY/native/10173645.pdfTarget Area Design Basis and System Performance for NIF]'', American Nuclear Society, June 1994. Retrieved on [[May 7]] [[2008]].</ref>
NIF is also exploring new types of targets. Previous experiments generally used plastic ablators, typically [[polystyrene]] (CH). NIF's targets constructed by coating a plastic form in a layer of sputtered [[beryllium]] or beryllium-copper alloys, and then oxidizing the plastic out of the center.<ref> Douglas Wilson et all, ''[http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=PHPAEN000005000005001953000001&idtype=cvips&gifs=yes The development and advantages of beryllium capsules for the National Ignition Facility]'', Phys. Plasmas 5, 1953, 1998, DOI:10.1063/1.872865. Retrieved on [[May 7]] [[2008]].</ref><ref>''[https://www.llnl.gov/str/JulAug07/Atherton.html Meeting the Target Challenge]'', Science & Technology Review, July/August 2007. Retrieved on [[May 7]] [[2008]].</ref> In comparison to traditional plastic targets, beryllium targets offer higher density, high opacity to x-rays, and high thermal conductivity. All of these are advantageous in the indirect-drive mode where the incoming energy is in the form of x-rays. They also have a higher leftover ablative mass compared to the fuel inside, which has the benefit of being less sensitive to instability growth from the roughness of the DT ice (although plastic targets of the same mass also show this effect). A more practical benefit is that the mechanical strength of a Be target is high enough to contain the fuel in gas form at room temperature. This could allow the targets to be filled with fuel and stored for periods before being chilled to freeze the DT just before firing. In practice, however, the ice has to be carefully grown from an initial seed.<ref>''[https://lasers.llnl.gov/programs/nic/target_fabrication.php Target Fabrication]'', Lawrence Livermore National Laboratory. Retrieved on [[May 7]] [[2008]].</ref>
Although NIF was primarily designed as an indirect drive device, the energy in the laser is high enough to be used as a ''direct drive'' system as well, where the laser shines directly on the target. Even at UV wavelengths the power delivered by NIF is estimated to be more than enough to cause ignition, resulting in fusion energy gains of about forty times,<ref>S. V. Weber et all, ''[http://flux.aps.org/meetings/YR9596/BAPSDPP95/abs/S6P06.html Hydrodynamic Stability of NIF Direct Drive Capsules]'', MIXED session, November 08. Retrieved on [[May 7]] [[2008]].</ref> somewhat higher than the indirect drive system. In this case the value of the Be target is reduced and more traditional plastic targets are more appropriate. A more uniform beam layout suitable for direct drive experiments can be arranged through changes in the switchyard that move half of the beamlines to locations closer to the middle of the target chamber.
[[Image:Laser hohlraum target energy coupling.jpg|thumb|right|300px|Laser energy to hohlraum x-ray to target capsule energy coupling efficiency. Note the "laser energy" is after conversion to UV, which loses about 50% of the original IR power.]]
It has been shown, using scaled implosions on the OMEGA laser and computer simulations, that NIF should also be capable of igniting a capsule using the so called ''polar direct drive'' (PDD) configuration where the target is irradiated directly by the laser, but only from the top and bottom.<ref name=pdd>Yaakobi, B.; R. L. McCrory, S. Skupsky, et al. ''[http://www.lle.rochester.edu/pub/review/v104/104_03Polar.pdf Polar Direct Drive—Ignition at 1 MJ]'', LLE Review, Vol 104, September 2005, pp 186-8. Retrieved on [[May 7]] [[2008]].]</ref> In this configuration the target suffers either a "pancake" or "cigar" [[anisotropy]] on implosion, reducing the maximum temperature at the core. However, the amount of energy being dumped into the target by the laser is so high that it ignites anyway. Fusion gains in this configuration are estimated to be anywhere between ten and thirty times; less than the symmetrical direct-drive approach, but obtainable with no changes to the NIF beamline layout.
Other targets, called ''saturn targets'', are specifically designed to reduce the anisotropy and improve the implosion.<ref>True, M. A.; J. R. Albritton, and E. A. Williams, "[http://www.lle.rochester.edu/pub/review/v102/102_01Saturn.pdf The Saturn Target for Polar Direct Drive on the National Ignition Facility], LLE Review, Vol. 102, January-March 2005, pp 61-6. Retrieved on [[May 7]] [[2008]].</ref> They feature a small plastic ring around the "equator" of the target, which quickly vaporizes into a plasma when hit by the laser. Some of the laser light is refracted through this plasma back towards the equator of the target, evening out the heating. Ignition with gains just over thirty-five are thought to be possible using these targets on NIF,<ref name=pdd/> producing results almost as good as the fully symmetric direct drive approach.
==History==
===Impetus===
LLNL's history with the ICF program starts with physicist John Nuckolls, who predicted in 1972 that ignition could be achieved with laser energies about 1 kJ, while "high gain" would require energies around 1 MJ.<ref>Nuckolls et al, ''[http://www.nature.com/nature/journal/v239/n5368/pdf/239139a0.pdf Laser Compression of Matter to Super-High Densities: Thermonuclear (CTR) Applications]'', ''Nature'' Vol. 239, 1972, pp. 129</ref><ref>John Lindl, ''[http://www.osti.gov/bridge/servlets/purl/10126383-6NAuBK/native/10126383.pdf The Edward Teller Medal Lecture: The Evolution Toward Indirect Drive and Two Decades of Progress Toward ICF Ignition and Burn]'', 11th International Workshop on Laser Interaction and Related Plasma Phenomena, December 1994. Retrieved on [[May 7]] [[2008]].</ref> Although this sounds very low powered compared to modern machines, at the time it was just beyond the [[state of the art]], and led to a number of programs to produce lasers in this power range. LLNL decided early on to concentrate on glass lasers, while other facilities studied gas lasers using carbon dioxide (e.g. [[Antares laser]], [[Los Alamos National Laboratory]]) or KrF (e.g. [[Nike laser]], [[Naval Research Laboratory]]). By the 1980s the advantage of shorter wavelengths in terms of delivering energy to the interior of the targets had been conclusively demonstrated in LLNL's highly successful [[Shiva laser]]. This put the glass laser approach pioneered at LLNL in the lead for future development.
After the Shiva project, LLNL turned to the 20-beam 200 kJ [[Nova laser]] design which was expected to reach ignition conditions. During the initial construction phase, Nuckolls found an error in his calculations, and a October 1979 review chaired by John Foster Jr. of [[TRW]] confirmed that there was no way Nova would reach ignition. The Nova design was then modified into a smaller 10-beam design that added frequency conversion to 351 nm light, which would increase coupling efficiency.<ref name=peer>Matthew McKinzie and Christopher Paine, ''[http://www.nrdc.org/nuclear/nif2/findings.asp When Peer Review Fails]'', NDRC. Retrieved on [[May 7]] [[2008]].</ref> In operation, Nova was able to deliver about 20 to 30 kJ of laser energy, about half of what was initially expected, due to various nonlinear optical effects.
Throughout these efforts, the amount of energy needed to reach ignition had continually risen and it was unclear whether or not the current 200 kJ estimate were more reliable than earlier ones. The [[United States Department of Energy|Department of Energy]] (DOE) decided that direct experimentation was the best way to settle the issue, and between 1978 and 1988 ran a series of underground experiments at the [[Nevada Test Site]] that used small nuclear bombs to directly illuminate ICF fuel components with high-energy X-rays; LLNL ran their program under the name "Halite", while LANL ran theirs as "Centurion".<ref>John Lindl, ''Development of the Indirect-Drive Approach to Inertial Confinement Fusion and the Target Physics Basis for Ignition and Gain'', Physics of Plasmas Vol. 2, No. 11, November 1995; pp. 3933–4024</ref> Initial data was available by mid-1984, and the testing ceased in 1988. Although there is little publicly available data from the Halite-Centurion series, it appears the experiments suggested that an implosion energy of about 20 MJ was required, and that given that about 1/5th of the laser energy is delivered as X-rays, drivers on the order of 100 MJ would be needed.<ref>A 1987 Los Alamos panel chaired by G. Canavan concluded "laser energies in the 100 MJ range ... may be required for [laboratory] fusion experiments ..." ''Technical Review of HF-Driven Laser Fusion'', Los Alamos National Laboratory, [[17 February]] [[1987]], p. 9</ref>
===LMF and Nova Upgrade===
Nova's partial success, combined with the Halite-Centurion numbers, prompted DOE to request a custom military ICF facility they called the "Laboratory Microfusion Facility" (LMF) that could achieve fusion yield between 100 and 1000 MJ. Based on the LASNEX computer models, it was estimated that LMF would require a driver of about 10 MJ,<ref name=peer/> in spite of the Halite-Centurion test that suggested a higher power. Building such a device was within the state of the art, but would be expensive, on the order of $1 billion.<ref name=upgrade>''Nova Upgrade - A Proposed ICF Facility to Demonstrate Ignition and Gain'', Lawrence Livermore National Laboratory ICF Program, July 1992</ref> LLNL returned a design with a 5 MJ 350 nm (UV) driver laser that would be able to reach about 200 MJ yield, which was enough to access the majority of the LMF goals. The program was estimated to cost about $600 million FY 1989 dollars, and an additional $250 million to upgrade it to a full 1000 MJ if needed, and would grow to well over $1 billion if LMF was to meet all of the goals the DOE asked for.<ref name=upgrade/> Other labs also proposed their own LMF designs using other technologies.
Faced with this enormous project, in 1989/90 [[United States National Academy of Sciences|National Academy of Sciences]] conducted a second review of the US ICF efforts on behalf of the [[US Congress]]. The report concluded that "considering the extrapolations required in target physics and driver performance, as well as the likely $1 billion cost, the committee believes that an LMF [i.e. a Laser Microfusion Facility with yields to one gigajoule] is too large a step to take directly from the present program." Their report suggested that the primary goal of the program in the short term should be resolving the various issues related to ignition, and that a full-scale LMF should not be attempted until these problems were resolved.<ref name=icfreview>''Review of the Department of Energy’s Inertial Confinement Fusion Program, Final Report'', National Academy of Sciences</ref> The report was also critical of the gas laser experiments being carried out at LANL, and suggested they, and similar projects at other labs, be dropped. The report accepted the LASNEX numbers and continued to approve an approach with laser energy around 10 MJ. Nevertheless the authors were aware of the potential for higher energy requirements, and noted "Indeed, if it did turn out that a 100-MJ driver were required for ignition and gain, one would have to rethink the entire approach to, and rationale for, ICF."<ref name=icfreview/>
In July 1992 LLNL responded to these suggestions with the '''Nova Upgrade''', which would reuse the majority of the existing Nova facility, along with the adjacent Shiva facility. The resulting system would be much lower power than the LMF concept, with a driver of about 1 to 2 MJ.<ref>Tobin, M.T et all, ''[http://ieeexplore.ieee.org/Xplore/login.jsp?url=/iel2/578/5735/00218762.pdf?tp=&isnumber=&arnumber=218762 Target area for Nova Upgrade: containing ignition and beyond]'', Fusion Engineering, 1991, pg. 650–655. Retrieved on [[May 7]] [[2008]].</ref> The new design included a number of features that advanced the state of the art in the driver section, including the multi-pass design in the main amplifiers, and 18 beamlines (up from 10) that were split into 288 "beamlets" as they entered the target area in order to improve the uniformity of illumination. The plans called for the installation of two main banks of laser beamlines, one in the existing Nova beamline room, and the other in the older Shiva building next door, extending through its laser bay and target area into an upgraded Nova target area. The lasers would deliver about 500 TW in a 4 ns pulse. The upgrades were expected to allow the new Nova to produce fusion yields between 2 and 20 MJ<ref name=upgrade/> The initial estimates from 1992 estimated construction costs around $400 million, with construction taking place from 1995 to 1999.
===NIF emerges===
Throughout this period the ending of the [[Cold War]] led to dramatic changes in defense funding and priorities. As the need for nuclear weapons was greatly reduced and various arms limitation agreements led to a reduction in warhead count, the US was faced with the prospect of losing a generation of nuclear weapon designers able to maintain the existing stockpiles, or design new weapons.<ref>William Broad, ''[http://query.nytimes.com/gst/fullpage.html?res=9D0DE4D9133DF932A15755C0A962958260 Vast Laser Plan Would Further Fusion and Keep Bomb Experts]'', New York Times, [[June 21]], [[1994]]. Retrieved on [[May 7]] [[2008]].</ref> At the same time, progress was being made on what would become the [[Comprehensive Nuclear-Test-Ban Treaty]], which would ban all criticality testing. This would make the reliable development of newer generations of nuclear weapons much more difficult.
Out of these changes came the [[Stockpile Stewardship and Management Program]], which, among other things, included funds for the development of methods to design and build nuclear weapons that would work without having to be explosively tested. In a series of meetings that started in 1995, an agreement formed between the labs to divide up the SSMP efforts. An important part of this would be confirmation of computer models using low-yield ICF experiments. The Nova Upgrade was too small to use for these experiments,<ref>Letter from Charles Curtis, Undersecretary of Energy, [[June 15]], [[1995]]</ref> and a redesign emerged as NIF in 1994. The estimated cost of the project was just over $1 billion,<ref>1.9 Cost (NIF CDR, Chapter 9)</ref> with completion in 2002. Physicist Richard Garwin described the outcome this way, "Sandia got the microelectronics research center [MESA], which had minimal relevance to the CTBT. Los Alamos got the Dual-Axis Radiographic Hydrodynamic Test facility. Livermore got the National Ignition Facility—the white elephant eating us out of house and home. They all maintained these were essential to stockpile stewardship, which they are not."<ref name=slate>Nathan Hodge and Sharon Weinberger, ''[http://www.slate.com/id/2122382/entry/2122493/ A Nuclear Family Rivalry]'', Slate Magazine, [[July 13]], [[2005]]. Retrieved on [[May 7]] [[2008]].</ref>
In spite of the "agreement", the large project cost combined with the ending of similar projects at other labs resulted in several highly critical comments by other weapons labs, in particular, [[Sandia National Laboratories]]. In May 1997, Sandia fusion scientist Rick Spielman publicly stated that NIF had "virtually no internal peer review on the technical issues" and that "Livermore essentially picked the panel to review themselves"<ref>"Livermore's costly fusion laser won't fly, scientists say", Albuquerque Tribune, [[May 29]], [[1997]], p. 1</ref> Similar complaints about the makeup of the "oversight" committees, consisting largely of LLNL contractors, led to a lawsuit being filed by the Natural Resources Defense Council.<ref>''[http://fas.org/sgp/news/2000/10/nrdcnif.html NATURAL RESOURCES DEFENSE COUNCIL and TRI-VALLEY CARES v. BILL RICHARDSON and DEPARTMENT OF ENERGY]''. Retrieved on [[May 7]] [[2008]].</ref> A retired Sandia manager, Bob Puerifoy, was even more blunt; "NIF is worthless ... it can't be used to maintain the stockpile, period."<ref>L. Spohn, "NIF opponents to cite criticism of laser in court battle", Albuquerque Tribune, [[June 13]], [[1997]], p. A15.</ref>
===Construction problems===
Work on the NIF started with a single beamline demonstrator, Beamlet. Beamlet operated between 1994 and 1997 and was entirely successful. It was then sent to [[Sandia National Laboratories]] as a light source in their [[Z machine]]. A full-sized demonstrator then followed, in AMPLAB, which started operations in 1997.<ref>J. A. Horvath, ''[https://e-reports-ext.llnl.gov/pdf/234367.pdf Assembly and Maintenance of Full Scale NIF Amplifiers in the Amplifier Module Prototype Laboratory (AMPLAB)]'', Third Annual International Conference on Solid State Lasers for Application (SSLA) to Inertial Confinement Fusion (ICF), [[July 16]], [[1998]]</ref> The official groundbreaking on the main NIF site was in June 1997.
At the time, the DOE was estimating that the NIF would cost approximately $1.1 billion and another $1 billion for related research, and would be complete as early as 2002.<ref name=GAO1>''[http://www.gao.gov/archive/2000/rc00141.pdf NATIONAL IGNITION FACILITY, Management and Oversight Failures Caused Major Cost Overruns and Schedule Delays]'', GAO, August 2000</ref> Later in 1997 the DOE approved an additional $100 million in funding and pushed the operational date back to 2004. As late as 1998 LNLL's public documents stated the overall price was $1.2 billion, with the first eight lasers coming online in 2001 and full completion in 2003.<ref>Howard T. Powell and Richard H. Sawicki, ''[https://www.llnl.gov/str/Powell.html Keeping Laser Development on Target for the National Ignition Facility]'', S&TR, March 1998. Retrieved on [[May 7]] [[2008]].</ref>
Sandia, with extensive experience in pulsed power delivery, designed the capacitor banks used to feed the flash lamps, completing the first unit in October 1998. To everyone's surprise, the Pulsed Power Conditioning Modules (PCMs) suffered capacitor failures that led to "explosions". This required a redesign of the module to contain the debris, but since the buildings holding them had already been poured, this left the new modules so tightly packed that there was no way to do maintenance in-place. Yet another redesign followed, this time allowing the modules to be removed from the bays for servicing.<ref name=peer/> Continuing problems of this sort further delayed the operational start of the project, and in September 1999 an updated DOE report stated that NIF would require up to $350 million more and completion would be pushed back to 2006.<ref name=GAO1/>
Throughout this period the problems with NIF were not being reported up the management chain. In 1999 then [[Secretary of Energy]] [[Bill Richardson (politician)|Bill Richardson]] reported to Congress that the NIF project was on time and budget, following the information that had been passed onto him by E. Michael Campbell, NIF's director. In August that year it was revealed that Campbell had misled Richardson, and in fact neither claim was close to the truth.<ref name=nyt>James Glanz, ''[http://www.nytimes.com/library/national/science/081900sci-laser-missiles.html Laser Project Is Delayed and Over Budget]'', New York Times, [[August 19]], [[2000]]. Retrieved on [[May 7]] [[2008]].</ref> As the GAO would later note, "Furthermore, the Laboratory's former laser director, who oversaw NIF and all other laser activities, assured Laboratory managers, DOE, the university, and the Congress that the NIF project was adequately funded and staffed and was continuing on cost and schedule, even while he was briefed on clear and growing evidence that NIF had serious problems."<ref name=GAO1/> Richardson later commented "I have been very concerned about the management of this facility… bad management has overtaken good science. I don't want this to ever happen again." A DOE Task Force reporting to Richardson late in January 2000 summarized that "organizations of the NIF project failed to implement program and project management procedures and processes commensurate with a major research and development project… [and that] …no one gets a passing grade on NIF Management: not the DOE's office of Defense Programs, not the Lawrence Livermore National Laboratory and not the University of California."<ref>''[http://www.seab.energy.gov/publications/nif_rpt.pdf Interim Report of the National Ignition Facility Laser System Task Force]'', Secretary of Energy Advisory Board, [[January 10]], [[2000]]. Retrieved on [[May 7]] [[2008]].</ref> Campbell resigned from the project in September 1999, when it was disclosed that he never completed a doctorate from Princeton that he had allowed the laboratory to believe he held.<ref name=nyt1>''[http://query.nytimes.com/gst/fullpage.html?res=9505E7D7113BF932A0575BC0A96F958260 Top U.S. Laser Expert Admits Lack of a Ph.D. and Resigns]'', New York Times, [[August 31]], [[1999]]. Retrieved on [[May 7]] [[2008]].</ref>
===Re-baseline and GAO report===
In the wake of these revelations the DOE started a comprehensive "Rebaseline Validation Review of the National Ignition Facility Project" in 2000, which took a critical look at the project, identifying areas of concern and adjusting the schedule and budget to insure completion. John Gordon, National Nuclear Security Administrator, stated "We have prepared a detailed bottom-up cost and schedule to complete the NIF project… The independent review supports our position that the NIF management team has made significant progress and resolved earlier problems."<ref>Ian Hoffman, ''[http://lanl-the-rest-of-the-story.blogspot.com/2007/06/nuclear-testing-gear-in-doubt-livermore.html Nuclear testing gear in doubt]'', MediaNews Group, </ref> The report revised their budget estimate to $2.25 billion, not including related R&D which pushed it to $3.3 billion total, and pushed back the completion date to 2006 with the first lines coming online in 2004.<ref name=fas65>''[http://www.aip.org/fyi/2000/fyi00.065.htm New Cost and Schedule Estimates for National Ignition Facility]'', FYI: The API Bulleting of Science Policy News, American Institute of Physics. Retrieved on [[May 7]] [[2008]].</ref><ref>''[http://www-ferp.ucsd.edu/FPA/ARC00/fpn00-29.shtml More on New NIF Cost and Schedule]'', FYI, American Institute of Physics, Number 65, [[June 15]], [[2000]]. Retrieved on [[May 7]] [[2008]].</ref>
Given the budget problems, the [[US Congress]] requested an independent review by the [[General Accounting Office]] (GAO). They returned a highly critical report in August 2000 stating that the budget was likely $3.9 billion, including R&D, and that the facility was unlikely to be completed anywhere near on time.<ref name=GAO1/><ref name=fas101>''[http://www.aip.org/fyi/2000/fyi00.101.htm GAO Report Cites New NIF Cost Estimate]'', FYI, American Institute of Physics, Number 101: August 30, 2000. Retrieved on [[May 7]] [[2008]].</ref> The report, "''Management and Oversight Failures Caused Major Cost Overruns and Schedule Delays''," identified management problems for the overruns, and also criticized the program for failing to include a considerable amount of money dedicated to target fabrication in the budget, including it in operational costs instead of development.<ref name=nyt/> A follow-up report the next year included all of these items, pushing the budget to $4.2 billion, and the completion date to around 2008.
The public fighting between the various Department of Energy laboratories soon started anew. Los Alamos publicly attacked the facility as ill-conceived.<ref>Jocelyn Kaiser, David Malakoff, Robert F. Service, ''ScienceScope'', Science, Volume 288, Number 5471, June 2, 2000</ref> On [[25 May]] Sandia vice president Tom Hunter told the ''[[Albuquerque Tribune]]'' that the NIF should be downsized so that it would not "disrupt the investment needed" in other labs.<ref name=sandia>''[http://www.sciencemag.org/cgi/content/summary/288/5471/1563c Family Quarrel; internal fight over the future of the world's largest laser]'', Science, Vol. 288. No. 5471, [[June 2]], [[2000]], p. 1563, DOI: 10.1126/science.288.5471.1563c. Retrieved on [[May 7]] [[2008]].</ref> Criticism of the project also came from politicians, government officials and review panels, some going so far as to refer to the project as being "out of control".<ref> Jim Dawson, ''[http://scitation.aip.org/journals/doc/PHTOAD-ft/vol_54/iss_1/21_1.shtml NIF Moves Forward Amid Controversy]'', Physics Today, January 2001, pp. 21. Retrieved on [[May 7]] [[2008]].</ref>
===Progress===
Although the NIF remained a controversial program, after the rebaselining effort construction has gone largely according to plan. The early problems with the PAMs and PCMs were ironed out, and construction then started to proceed more rapidly.
LRU installation started in 2005, and has continued at an increasing pace since then. In May 2003, the NIF achieved "first light" on a bundle of 4 beams, producing a 10.4kJ pulse of IR light in a single beamline.<ref name=performance/> In 2005 the first 8 beams (a full bundle) were fire fired producing 153 kJ of infrared light, thus eclipsing OMEGA as the highest energy laser (per pulse) on the planet. By January 2007 all of the LRUs in the Master Oscillator Room (MOOR) were complete, and the computer room had been installed. By August 2007 96 laser lines were completed and commissioned, and "A total infrared energy of more than 2.5 megajoules has now been fired, this is more than 40 times what the Nova laser typically operated at the time it was the world's largest laser."<ref>''[https://publicaffairs.llnl.gov/news/news_releases/2007/NR-07-11-05.html World's largest laser picks up the pace]'', Lawrence Livermore National Laboratory, [[November 21]], [[2007]]. Retrieved on [[May 7]] [[2008]].</ref> The lab currently calls for construction to be complete in March 2009, with the first attempts at ignition using a 1.8MJ of IR power starting the next year (about 1MJ of UV).<ref name=performance/>
Recent reviews of the project have been positive, generally in keeping with the post-GAO Rebaseline schedules and budgets. However, there are lingering concerns about the NIF's ability to reach ignition, at least in the short term. An independent review by the [[JASON Defense Advisory Group]] was generally positive about NIF's prospects over the long term, but concludes that "The scientific and technical challenges in such a complex activity suggest that success in the early attempts at ignition in 2010, while possible, is unlikely."<ref name=jason>''[http://www.fas.org/irp/agency/dod/jason/nif.pdf NIF Ignition]'', JASON Program, [[June 29]], [[2005]]</ref> The group suggested a number of changes to the completion timeline to bring NIF to its full design power as soon as possible.
The delays in NIF construction have led to something of a race with the French [[Laser Mégajoule]], which has very similar energies as NIF. Mégajoule started construction later than NIF but has a shorter planned building time, estimated to be complete in 2010. Mégajoule has run into problems of its own, however, and has been pushed back to 2012.<ref>''[http://www.photonics.com/content/spectra/2007/October/features/89220.aspx Photonics With a French Twist]''Photonics Spectra, October 2007. Retrieved on [[May 7]] [[2008]].</ref>
==Criticisms==
Outside of the problems with the project itself, criticism of NIF has been focused on its role in the [[Stockpile Stewardship and Management Program]] (SSP). This program is an umbrella effort to study the long-term storage of the nuclear stockpile, and a variety of groups have been highly critical of the effort, dismissing it as a program of "scientific welfare" that has little to do with science and much to do with keeping a nuclear industry alive. The [[Federation of American Scientists]] noted that "Some claim that the experiments were politically essential; only with the promise of huge, expensive projects would the laboratory management publicly endorse a testing moratorium."<ref name=fasssp>A. Fitzpatrick, I. Oelrich, ''[http://fas.org/2007/nuke/Stockpile_Stewardship_Paper.pdf The Stockpile Stewardship Program: Fifteen Years On]'', Federation of American Scientists, March 2007. Retrieved on [[May 7]] [[2008]].</ref> NIF is singled out as a particularly weak portion of the SSP, with questions about its capability to generate information that is actually useful to the Project.
However, in 2001 it was learned that LLNL was pursuing a method to allow the use of [[plutonium]] and [[uranium]] in experiments on NIF;<ref>Marylia Kelley, ''[http://www.inesap.org/bulletin21/bul21art33.htm Plutonium, HEU, and Lithium Hydride]'', International Network of Engineers and Scientists Against Proliferation, Bulletin 21. Retrieved on [[May 7]] [[2008]].</ref> this would allow a direct examination of [[equation of state]] parameters for these materials at extremely high pressures and densities not currently allowed by subcritical experiments which compress the fissile material using conventional explosives. The decision to proceed with the use of plutonium, other fissile materials, fissionable materials, and lithium hydride in experiments conducted at the NIF was finalized by the National Nuclear Security Administration in November 2005.<ref>''[http://www.nap.edu/catalog.php?record_id=11960 Plasma Science: Advancing Knowledge in the National Interest]'', National Research Council, 2007, page 228</ref><ref>''Record of Decision: Final Site-wide Environmental Impact Statement for Continued Operation of Lawrence Livermore National Laboratory and Supplemental Stockpile Stewardship and Management Programmatic Environmental Impact Statement'', U.S. Department of Energy, Federal Register, Vol. 70, No. 228, [[November 29]], [[2005]], pp. 71491–71500.</ref> A 2007 report by the National Research Council's Plasma Science Committee concluded that "NIF is crucial to the NNSA Stockpile Stewardship Program because it will be able to create the extreme conditions of temperature and pressure that exist on Earth only in exploding nuclear weapons and that are therefore relevant to understanding the operation of our modern nuclear weapons."<ref>Plasma 2010 Committee, ''[http://books.nap.edu/catalog.php?record_id=11960#toc Plasma Science: Advancing Knowledge in the National Interest]'', National Research Council, 2007</ref>
<gallery>
Image:NIF_target_chamber.jpg|A construction worker inside NIF's 10 meter target chamber. Almost all of the engineering on the NIF laser is on an enormous scale.
Image:NIF target chamber exterior.jpg|Exterior view of the upper 1/3rd of the target chamber. The large square beam ports are prominent.
Image:nif_flashlamps.jpg|The flashlamps used to pump the main amplifiers are the largest ever in commercial production.
Image:Laser glass slabs.jpg|The glass slabs used in the amplifiers are likewise much larger than previous lasers.
</gallery>
==References==
{{reflist|2}}
==External links==
*[https://lasers.llnl.gov National Ignition Facility homepage]
*[http://www.ingenia.org.uk/ingenia/articles.aspx?Index=466 NIF Director, Dr Ed Moses, on the progress of the facility], ''Ingenia'' magazine, December 2007
{{fusion experiments}}
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[[Category:Inertial confinement fusion research lasers]]
[[Category:Nuclear stockpile stewardship]]
[[Category:Research institutes in the United States]]
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