Part 1 of 17 Parts
My last series of posts dealt with a company called LPP Fusion which is developing a nuclear fusion reactor that will make use of a hydrogen and boron gaseous mixture for fuel. Theoretically, the fusion reaction that takes place between nuclei of hydrogen and nuclei of boron could provide a very efficient, radioactivity free form of nuclear energy with virtually unlimited fuel available. The reaction produces no dangerous penetrating radiation and no radioactive waste. Only stable helium nuclei, also known as alpha particles, are generated by the reaction. The electric charge of these particle allows the direct conversion of fusion energy into electricity.
These obvious advantages of hydrogen-boron fuel have been known for a long time but, until recently, the extreme physical conditions that are necessary for a hydrogen-boron fusion reactor seemed far beyond current technology.
However, the situation has changed dramatically because of the development of laser systems which can generate ultra-short pulses of coherent light in the range of a few femtoseconds. A femtosecond is a millionth of a billionth of a second. Also, important discoveries have been made with regard to a technique for amplifying these pulses by up to a trillion times.
This technique is called chirped pulse amplification (CPA). Gérard Mourou and Donna Strickland were the discovers of this technique and they were awarded a Nobel Prize for their work in 2018. With the assistance of CPA, it is possible to concentrate sufficient energy into an ultra-short pulse so that it reaches powers in the ranges of petawatts. A petawatt is a million billion watts. This is more than one hundred times the power of all electricity generated by all of the electrical power stations in the world combined but only for a tiny fraction of a second.
At the focus of these laser pulses, the light intensifies to thousands of billions of billions of watts per square centimeter. This can be compared to what would happen if the entire energy that reaches the Earth from the Sun were to be concentrated into a one millimeter spot. This is referred to as “extreme light.” Extreme light is a very exiting new research area for basic and applied physics. It has revolutionary implications for the future of technology. One of the very important areas of research that will be impacted is that of nuclear fusion research.
The idea of using lasers to trigger fusion reactions has been researched for more than fifty years. The basic concept of the research has been to bombard a tiny sphere of fuel from all sides simultaneously with pulses of energy. This causes the pellet of fuel to compress to extreme densities and to heat up to temperatures that are required for nuclear fusion reactions. The combination of very high temperature and very high density is necessary in order to reach a point referred to as “ignition”. This is a condition in which the reaction process becomes self-sustaining which results in an efficient “microexplosion” with the release of a large amount of energy.
Pursuit of the laser implosion approach to nuclear fusion resulted in the construction of the world’s biggest laser called the National Ignition Facility (NIF). It was constructed at the U.S. Lawrence Livermore National Laboratory at a cost of over three billion dollars.
They do not use hydrogen-boron at the NIF. Instead, they combine deuterium and tritium as a fuel which requires less extreme conditions than hydrogen-boron. The deuterium and tritium reaction requires temperatures of around one hundred million degrees and has a much higher rates of fusion reactions than hydrogen-boron fuel.
Despite some solid accomplishments, NIF has not reached its desired goal of achieving “ignition”. The prospects for constructing commercially viable laser fusion power stations based on the NIF approach appear less possible in the near future.
Please read Part 2 next