Our Vision for Fusion
We aim to realize a commercial fusion reactor based on the p-11B reaction (a fusion reaction between hydrogen and boron-11), which is considered the “ultimate clean energy source.” An explanation of the p-11B reaction, also known as “advanced fuel fusion,” can be found here.
Until now, achieving the p-11B reaction has long been considered extremely difficult. This is because in thermal fusion —the approach pursued by many fusion research institutions and companies—the p-11B reaction requires very high plasma temperatures. Therefore, we are taking a novel approach to induce the p-11B reaction, one that differs from conventional thermal fusion.
What is Thermal Fusion?
In thermal fusion, fusion reactions occur when plasma particles confined at high temperature and high density collide with each other due to their thermal motion, allowing them to overcome the Coulomb barrier.
The graph below shows the velocity distribution of particles in plasma at a certain temperature. The horizontal axis represents particle velocity, and the vertical axis represents the proportion of particles with that velocity. When the plasma temperature is 10 keV* (approximately 100 million degrees Celsius), not all particles in the plasma move at the same speed; there is a distribution of particles with various speeds, from slow to fast. In thermal fusion, the fusion reaction occurs when a very small fraction of particles on the high-velocity (i.e., high-energy) tail of this distribution collide. Therefore, the entire plasma needs to be maintained at a high temperature.
Horizontal axis: Particle velocity
Vertical axis: Particle distribution
Many nuclear fusion research institutions and companies are aiming for fusion reactions using thermal plasma. Generally, when people think of “fusion,” they often imagine thermal fusion.
*) keV: Electronvolt (eV) is a unit of energy, and 1 keV (kiloelectronvolt) = 1,000 eV. In the fields of plasma and fusion, the temperature of ions and electrons is often expressed in electronvolts, and 1 eV is equivalent to approximately 10,000 degrees Celsius.
Advantages
If a sufficient number of fuel plasma particles undergo fusion reactions per unit time, the energy generated by the reactions can heat the plasma, allowing the fusion reaction to be self-sustaining without external energy input. This is called “self-ignition.”
Disadvantages
Thermal fusion requires confining high-temperature, high-density plasma for extended periods. The conditions for temperature, density, and confinement time required for self-ignition are extremely demanding, and no experiment has achieved all of them simultaneously to date.
Considering only temperature, for example, even the D-T reaction, which has the highest fusion reactivity, requires temperatures of 10 keV (approximately 100 million degrees Celsius) or higher. The p-11B reaction requires even higher temperatures (approximately 1 billion degrees Celsius). However, as the plasma temperature increases, radiative losses* also increase, leading to energy loss. Therefore, it is considered extremely difficult to achieve practical application of the p-11B reaction using conventional thermal fusion alone.
*) Radiative losses: When the trajectory of a moving charged particle is bent by an electric or magnetic field, the charged particle radiates some of its energy as electromagnetic waves. Energy loss due to such radiation is called “radiative loss.”
Our Non-Thermal Fusion Approach
As mentioned above, inducing the p-11B reaction through thermal fusion is extremely challenging. We aim for the p-11B reaction by a non-thermal plasma formed by using high-energy particle beams, leveraging the unique characteristics of both FRCs and magnetic mirrors.
A particle beam consists of ions accelerated to high energy, which are then neutralized and injected into the plasma. In our approach, the fusion reaction primarily occurs between boron-11 in the plasma and hydrogen injected by the beam.
Let us briefly explain our approach to realizing non-thermal fusion. As explained here, an FRC has a closed magnetic field region within an open magnetic field region. Because a high-density plasma (core plasma) is confined in this closed magnetic field region, previous research has focused on the performance of the core plasma. However, the characteristics of the core plasma are strongly influenced by the surrounding open magnetic field region, and confined high-energy ions also exist in this surrounding region. Therefore, we aim to achieve non-thermal fusion through a completely new concept: applying a strong magnetic mirror field to FRC’s open magnetic field region and utilizing both of these regions as reaction fields.
Features
No Need to Heat the Entire Plasma to High Temperatures
Inducing the p-11B reaction via thermal fusion requires temperatures of around 100 keV (approximately 1 billion degrees Celsius). However, in non-thermal fusion, the primary reactions are caused by high-energy ions of several hundred keV, eliminating the need to heat the entire core plasma to extreme temperatures.
Furthermore, in FRCs, high-energy ions have large orbits that reach the boundary of the core plasma. This allows for the construction of a system where the core plasma and high-energy beam ions, with significantly different energy levels, can coexist.
Easy Control of Power Output
In our method, the power output can be adjusted by controlling the injected beam. This enables power generation according to electricity demand, making it promising for use as both a peak power source and a base load power source.
Relatively Low Development Costs
Realizing fusion power generation requires the following steps
Step 1
Inducing a fusion reaction.
Step 2
Increasing the reaction efficiency so that the output energy exceeds the input energy.
Step 3
Continuously inducing fusion reactions (sustained power supply).
In non-thermal fusion, both the reaction rate and ion trajectories depend on the beam energy. Therefore, the above steps 1 and 2 can be experimented with using relatively small-scale devices by adjusting the number and current of the beams. Regarding step 3, there are research and development challenges such as heat load, but the requirements for many components are considered lower than in thermal fusion. Moreover, the FRC-mirror hybrid reactor has a simple structure, offering advantages in terms of maintainability and cooling compared to other methods.
In this way, we are leveraging the complementary features of both FRCs and magnetic mirrors, pursuing research and development towards the realization of a p-11B fusion reactor through a novel approach different from conventional methods.
References
[1] H. Matsuura, “2. Advanced-Fuel Fusion Plasmas and their Nuclear Burning,” J. Plasma Fusion Res. Vol.98, No.2 (2022),