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Laser
Laser
Mégajoule (LMJ) is a large laser-based inertial confinement fusion (ICF) research device being built near Bordeaux, in France
France
by the French nuclear science directorate, CEA. Laser
Laser
Mégajoule plans to deliver about 1.8 MJ of laser energy to its targets, making it about as energetic as its US counterpart, the National Ignition Facility (NIF). Laser
Laser
Mégajoule is the largest ICF experiment to be built outside the US, where ICF research has been strongly related to nuclear weapons research. Likewise, Laser
Laser
Mégajoule's primary tasks will be refining fusion calculations for France's own nuclear weapons.[1] Laser
Laser
Mégajoule uses a series of 176 laser beamlines. Each beamline contains two main glass amplifiers, which are optically pumped using xenon flashlamps. A "feeder" laser beam is fed via optical fiber into each of the beamlines where it travels through the two amplifiers. In order to extract more power from the amplifiers, which are not particularly efficient in transmitting power to the beam, the laser pulse is sent through the amplifiers twice by an optical switch in front of a mirror. At the other end of the beamline a deformable mirror is used to remove imperfections in the wavefront. The target chamber lies in a large experiment room in the middle of the building, with the beamlines arranged on either side. After being switched into the main room, the beams are first aimed towards the target chamber by mirrors, and then travel through an optical frequency multiplier to boost the frequency into the ultraviolet. The mirrors are arranged in order to have the pulse impinge in the middle of the chamber from all sides.

A huge monocrystal of potassium dihydrogen phosphate grown from solution by Saint-Gobain
Saint-Gobain
for frequency conversion on the LMJ.

Like NIF, LMJ intends to use the "indirect drive" approach, where the laser light is used to heat a high-Z cylinder made of some heavy metal (often gold) known as a "hohlraum". The hohlraum then gives off x-rays, which are used to heat a small fuel pellet containing a deuterium-tritium (DT) fusion fuel. Although considerable laser energy is lost to heating the hohlraum, x-rays are much more efficient at heating the fuel pellet, making the indirect drive method applicable to nuclear weapons research. The x-rays rapidly heat the outer layer of the pellet so quickly that it explodes outward, causing the remainder of the pellet to be forced inward and causes a shock wave to travel in through the pellet to the middle. When the shock wave converges from all directions and meets in the middle, the density and temperature briefly reach the Lawson criterion
Lawson criterion
and start fusion reactions. If the rate of reactions is high enough the heat generated by these reactions will be enough to cause surrounding fuel to fuse as well, this process continuing until the majority of the fuel in the pellet is consumed. This process is known as "ignition", and has long been a goal of fusion researchers. Construction on the Laser
Laser
Mégajoule started with a single set of eight beamlines known as the Ligne d'Intégration Laser
Laser
(Laser Integration Line), or LIL, powered by a 450 MJ energy bank. When problems are worked out in the LIL, construction will continue with the construction of four more similar units and the installation of the additional beamlines. LIL was completed in 2002. The first laser beam shots were planned for the beginning of 2014,[2] but commencement of operations was later postponed until December of that year.[3] References[edit]

^ "Le Laser
Laser
Mégajoule". CEA - Direction des Applications Militaires. Retrieved 12 June 2012.  ^ Charles Crespya; Denis Villate; Olivier Lobios (2013). "Study of laser megajoule calorimeter's thermal behaviour for energy measurement uncertainty optimisation". Review of Scientific Instruments. 81 (1). Archived from the original on 2013-07-11.  ^ Hélène Arzeno (11 January 2014). "Premier tir le 2 décembre au Laser
Laser
Megajoule". Sud Ouest. Retrieved 25 October 2014. 

External links[edit]

Optical systems in the LMJ Laser
Laser
Mégajoule (in French) Laser
Laser
Mégajoule (in English)

v t e

Fusion experimental devices by confinement method

Magnetic

Tokamak

International

ITER DEMO PROTO

Americas

STOR-M MEDUSA-CR Alcator C-Mod DIII-D UCLA ET LTX NSTX-U Pegasus PBX-M TEXT TFTR ETE Novillo

Asia and Australia

LT-1 CT-6 CFETR EAST HL-1(M) HL-2A HT-6(B, M) HT-7(U) KT-5 SUNIST ADITYA SST-1 IR-T1 JT-60 QUEST KTM GLAST KSTAR KDEMO

Europe

JET COMPASS GOLEM TJ-I Tore Supra TFR ASDEX Upgrade TEXTOR FTU IGNITOR RTP ISTTOK T-3 T-4 T-10 T-15 TCV START MAST MAST-U

Stellarator

Americas

ATF CAT HSX NCSX QPS SCR-1

Asia and Australia

H-1NF Lingyun CHS Heliotron J LHD TU-Heliac

Europe

UST-1 UST-2 TJ-IU TJ-II TJ-K WEGA Wendelstein 7-AS Wendelstein 7-X Uragan-1 Uragan-2 (Uragan-2M) Uragan-3 (Uragan-3M) L-2M

RFP

RFX TPE-RX EXTRAP T2R MST

Other

MTF LDX SSPX MFTF MCX Polywell Dense plasma focus ZETA

Inertial

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NIF OMEGA Nova Nike Shiva Argus Cyclops Janus Long path Laser
Laser
Inertial Fusion Energy

Asia

SG-I SG-II SG-III SG-IV GEKKO XII

Europe

HiPER Asterix IV (PALS) LMJ LULI2000 ISKRA Vulcan

Non-laser

Qiangguang-1 PTS Z machine PACER

International Fusion Materials Irradiation Facility

Coordinates: 44°38′30.88″N 0°47′15.91″W / 44.6419111°N 0.7877528°W / 44.6419111

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