National Ignition Facility (NIF) – World’s Biggest Laser Fusion Experiment
The National Ignition Facility (NIF) is a large internal confinement fusion (ICF) device setup at the Lawrence Livermore National Laboratory in Livermore, California. Till date, it is known to be the world’s largest and most energetic laser device. It has the size of three football fields with a height of a 10 stories building. The device covers 172,800 square feet in physical size. It also has the record for being one of world’s most costly research devices with an annual budget of almost $140 million. The construction cost of the device came up to almost $3540 million. The whole device requires almost 1000 staffs for its maintenance.
The device also has the speciality of producing more energy than it consumed to start the reaction. The heat produced by the powerful lasers compresses a little amount of hydrogen fuel so as to produce a nuclear fusion reaction. They were able to produce a high temperature heat in such a way that it produced ignition. The device is mainly used to produce high energy through fusion reaction so as to aid and maintain nuclear weapons and also to design by studying the behaviour of matter under the conditions found within nuclear weapons.
The whole concept was budgeted and brought into action in 1997. But they had to delay the project due to initial testing failures and thus it was pushed further to 2000. The whole device was completed by 2009, though it was supposed to be completed by 2004, and the cost went up four times more than it was originally budgeted. After complete certification by the United States Department of Energy, the first laser beam experiment was conducted in June 2009 and the first combined ignition was completed by October 2010. The tests shows that the device was able to generate 2 million joules of energy with a temperature as high as 90 million degrees and pressures of about 100 billion times the Earth’s atmospheric pressure. The same pressure and temperature can only be found in the cores of stars and other huge gas filled planets.
The basic building layout of the NIF is shown below. The laser is created in the room, shown right of center. It is then split into two and passed through both sides, as shown with blue lines. After many passes through the beam lines, the light is then passed on to the “switchyard” (red) where it is aimed into the target chamber (silver).
Though the researchers have accomplished a high energy output, they are working harder to obtain a single 500 terawatt flash of light that reaches the target from all directions at one time, and that too within a fraction of a second. There are 48 beam lines inside the device which amplifies 192 beamlets. The beam lines contain 16 amplifiers per line, each one amplifying 4 of the beamlets.
An Injection Laser System (ILS) is used to make sure that the beam lines are uniform in nature. The initial laser light is amplified from a single source in the ILS. The output of the ILS met up on a target that has atoms of deuterium (hydrogen with one neutron) and tritium (Hydrogen with two neutrons). They fuse together and produce a high burst of energy. The process in the ILS starts with a low power flash of infra-red light (1053 nanometers) generated in an ytterbium-doped optical fiber laser known as the Master Oscillator. The output light of the Master Oscillator is again divided into 48 Pre-amplifier Modules. These modules make the light pass through a circuit containing a neodymium glass amplifier smaller than the ones used in the main beam lines, boosting the nano joules of light created in the Master Oscillator to about 6 joules. The design of the PAM has been re-modified since then, and it has helped them in making higher energies than the ones earlier obtained.
Since the whole activity in the device is similar to the ones happening in the cores of huge stars, researchers are trying to study how fusion produced some of the heavy atomic elements, such as gold and uranium.