1. Introduction
In conventional nuclear fusion, the presence of a Coulomb barrier (greater than MeV energies) between interacting nucleons has proved to be very challenging. Conventional nuclear fusion efforts are generally concentrated at overcoming the Coulomb barrier through the confinement of energetic ions of tens to hundreds of keV. By contrast, the Alpha Ring fusion concept is based on changing the height and extent of the Coulomb barrier, increasing the quantum tunneling efficiency, thereby increasing fusion reaction rates. Furthermore, our rotating systems generate significant centrifugal forces to compress pressure profiles which help bring the reactants together.
The first feature of our approach involves using the collective temporal and spatial behaviors of free and low-energy electrons to generate negative electric fields, aimed at overcoming the primary obstacle to fusion, which is the Coulomb repulsion between positively charged nuclei. Poisson’s equation governing fields depends only on the difference between electron and ion densities and not on their energies, which allows for a more favorable condition for quantum tunneling between initially low-energy reactants. For example, a highly emissive material, such as lanthanum hexaboride (LaB
6), is heated by rotating neutrals to provide a reservoir of free electrons. At the same time, the radial movement of emitted electrons is blocked by the same rotating high-density (~10
26/m
3) neutrals at the outer electrode, such that the free electrons just outside the emitter acquire a high density (~10
22/m
3). The oscillatory or collapsing behaviors of these free electrons, such as those existing in resonant plasma waves [
1], can further enhance local electron densities. Since fusion events occur in temporal and spatial scales of femtoseconds and femtometers, even high-frequency dynamic electric fields can counteract the repulsive Coulomb electric fields between reactant nuclei, thereby causing fusion.
To increase the density of reactants, the second feature of our approach involves utilizing centrifugal force created by rotation [
2,
3,
4,
5,
6]. A highly compressed state, including neutrals, electrons and ions through centrifugal or ponderomotive forces, results in significant fusion events since the fusion rate depends on the product of densities of reactants. The efficiency of using neutrals and ions, instead of requiring a fully ionized plasma, is emphasized in the Alpha Ring’s technology.
The Coulomb barrier is a result of electromagnetic forces which can be modified by appropriate dynamics of negative charges. The wave nature of reactants allows quantum tunneling through this reduced barrier. In
Section 2 (Rotating System for Fusion), the authors present a cylindrical rotating plasma immersed in an axial magnetic field. In
Section 3 (Coulomb Electric Fields and Potentials Between Two Atoms), it is shown that high gradients of free electrons and negative charges can establish a strong negative potential by centrifugal acceleration. In
Section 4 (Enhancement of Fusion Cross Section by Electron Screening), the Schrodinger equation is used to quantify the enhancement of fusion by electron screening, while
Section 5 (Enhancement of Fusion Cross Section by Plasma Oscillations) delves into the enhancement of the fusion cross sections by plasma oscillations.
Section 6 (Ion-Neutral Coupling) describes how the ion–neutral coupling controls the dynamics of neutrals.
Section 7 (Design Parameters of a Rotating Fusion Chamber) provides the design parameters of an example rotating fusion chamber with key performance numbers.
Section 8 is the conclusion, and
Section 9 is the discussion.
3. Coulomb Electric Fields and Potentials Between Two Atoms
Instead of imparting extremely high kinetic energy to the fusion reactants to overcome the electrostatic repulsion, Alpha Ring’s technology focus on employing an electron-rich region to reduce the Coulomb barrier to fuse two nuclei.
Free electrons in the Alpha Ring rotating device may be viewed as collectively catalyzing the fusion reaction of two nuclei. In early days, around 1957, the muon was described as catalyzing the fusion of a pair of hydrogen and deuterium atoms. Just as one muon can catalyze the fusion process by allowing two reactant nuclei to get closer to one another (~1 pico-meter), billions of free electrons in the vicinity of many reactants catalyze multiple fusion reactions. Effectively, the electrons reduce the energy barrier that prevents the two reactants from coming close enough to react. However, muon catalyzed fusion is not commercially viable, as muons have a much greater mass than electrons and, hence, producing them is much more energetically expensive. In addition, muons have a very short lifetime of approximately 2 microseconds.
By contrast, electrons, unlike muons, can be easily produced by high electron emissive material, such as lanthanum hexaboride, at 1500 K, with high densities by emitters and act collectively to produce a high electric field, especially under compression by a centrifugal acceleration of over a billion times the value of gravitational acceleration on the earth surface. Our recent computer modeling of the rotation process [
7] shows the centrifugal force is balanced by a steep pressure gradient of negative charges (electrons, and negatively charged hydrogen ions, H
−). It also shows that fusion reactants experience the attractive force over a much larger distance than just the tunneling region.
From the rotation, the increase in azimuthal velocity
vq leads to a centrifugal force, which is balanced mainly by the pressure gradient,
, where
p is the pressure,
T is the temperature,
n is the number density, and ρ is the mass density. It was shown in [
7] that, at a velocity of
near the outer wall, the corresponding centrifugal acceleration is
. A density gradient is developed to balance the centrifugal force, leading to a higher density, nearly 1000 times the average density at the outer wall.
4. Enhancement of Fusion Cross Section by Electron Screening
A certain part of the confining wall is composed of electron emitter materials. A surplus of electrons on the inner electrode generates an electron-rich region in proximity to the electrode surface, which rotates in the same direction as the positively charged particles due to the Lorentz force resulting from the potential difference between the inner and outer electrodes. One of the key factors in calculating fusion reaction rates is the cross section, which is usually very small at low energy due to the extremely low penetration factor through the Coulomb barrier around the nucleus. The tunneling through the Coulomb barrier is purely a quantum mechanical phenomenon and can be described by the Coulomb scattering process based on the Schrodinger equation, as follows:
where
V(
r) =
Z1Z2e2/
r is the Coulomb potential between particles of charges
Z1e and
Z2e. Equation (2) can be solved for the Coulomb wave function
around the nucleus [
8]. Since the nuclear radius (~10
−15 m) is much smaller than the Coulomb radius (~10
−10 m), the penetration probability
P is related closely to the wave function near
r = 0,
, and obtained as follows [
8]:
where
α =
e2/ℏ
c is the fine structure constant, v is the particle velocity,
c is the light velocity in vacuum, and
η is the Sommerfeld constant, which is related to the fine structure constant representing the electromagnetic forces between subatomic charged particles and essentially determining how an atom holds together its electrons. The Sommerfeld constant can be expressed in terms of the particle energy
E as follows [
8]:
where
m is the mass in the center of mass frame,
EG is the Gamow energy equivalent to the Coulomb potential at the Bohr nuclear radius, where the Coulomb repulsion is transitioned to the strong interaction regime. Therefore, Gamow energy represents the height of the Coulomb barrier for tunneling, which is proportional to the nuclear charges squared, making it much more difficult to obtain a fusion interaction between high-
Z nuclei. Since the reaction rate is proportional to the penetration factor, the fusion cross section is customarily written as follows [
9]:
where
S(
E) is the astrophysical factor, which represents the probability of nuclear reaction after penetration. Usually,
S(
E) represents a weak dependence on
E and can be expanded in power of
En, where the coefficients of expansion are determined from experiments.
When the penetration probability is small, the fusion cross section can also be calculated from the WKB method [
8]. Under this approximation, the barrier penetration factor
P can be found as follows:
where
is the wave decay constant in the barrier region and the integral covers the radial range where
E <
V(
r). For unscreened Coulomb potential,
, the integral can be carried out exactly and we have the penetration probability as follows [
8]:
where
and
Upk is the peak potential barrier. In the case of small
E,
is negligible and
Here
P has the same exponential dependence on energy
E, as given in Equation (3), when
E is much smaller than
EG (
η >> 1, a generally valid approximation for most cases). It is important to note that this same potential also governs the radiative decay as pointed out by Gamow, Gurney, and Condon [
10,
11].
By creating an external negative potential in addition to the positive Coulomb potential, the height and width of the overall Coulomb barrier to be penetrated is reduced. This external potential is typically generated by a layer of negative charges, with a characteristic distance longer than the separation between the nuclei. This property is crucial to quantum tunneling and, consequently, to fusion. The total potential is thus the sum of Coulomb potential and the screening potential, which is the integration of the screening field
Fs(
r) over the whole space. Accounting for this effect, the Schrodinger equation becomes the following:
And the barrier penetration factor
P’ can be found as follows:
Here, the new integration range of integration
r1′ to
r2′ is over the region where
. In general,
(
r) has a negligible variation within this very small range and can be represented by a constant
Us. For the case of screening by a charge sheet,
is given, as shown in the caption of
Figure 2. Since the result in Equation (7) is independent of
r1 and
r2, we can neglect the new values of
r1′ and
r2′ in Equation (10). Under this approximation, Equation (10) is identical to Equation (6) if
E in Equation (6) is replaced by (
E +
Us). As a result, we can use a similar formula as in Equation (3) and obtain penetration probability with screening effects as follows:
And the screened cross section, as in Equation (5), can be written as follows:
The screening energy can thus affect the fusion cross section, especially when it is close to or higher than the particle energy.
Figure 3 shows the cross sections for a p-
11B reaction for screening energies up to
Us = 45 keV, using Gamow energy
EG = 2.29 MeV for p-B and the following empirical astrophysical factor,
. For the p-B cross section, the values of those three coefficients are as follows:
C0 = 195 MeV-barn,
C1 = 241 barn, and
C2 = 231 barn/MeV [
12]. The resonant structure near
E = 148 keV, as shown in [
11], is neglected because the energy of our interest is far away from 148 keV.
Without screening (
Us = 0), the cross sections drop quickly when the particle energy goes below a few tens of keV. With the screening effect, the cross sections turn nearly flat below a few keV’s of
E because the screening energy dominates over the particle energy in this region. The cross section rises very quickly with the screening energy (from 10
−44 to ~10
−34 m
2 as
Us increases from 10 to 45 keV). The strong ion–neutral coupling in the rotation chamber is responsible for bringing neutrals to acquire rotation energies of 1–20 eV. In the following section, we will show how to create a fusion environment with high screening energies and compare the effect to other known processes, such as muon-catalyzed fusion [
13,
14].
In the preceding section, we have demonstrated the significance of screening energy in determining the screened cross section. By modulating the electron density distributions surrounding the positive Coulomb potential, a negative potential can be created, and the corresponding screening energy can be evaluated. It should be emphasized that the collective electron motions generate the electric field that leads to the screening effect, and the physical presence of electrons between the fusing nuclei is not necessary.
Bound electrons around the nucleus can provide a certain degree of screening for the incoming projectile. However, their charge distribution is basically fixed, and the screening effect was found to be limited, usually from 27 eV (for the hydrogen atom) to, at most, a few hundred eVs. On the other hand, the muon in the muon–hydrogen reaction is also bounded by the nucleus. However, due to its large mass (~200 times the electron mass), it brings the two nuclei in the hydrogen molecule much closer and thus facilitates higher possibilities for fusion. The screening energy for the muon–hydrogen is in the vicinity of 5 keV. However, an efficient muon fusion process is difficult to achieve due to its short lifetime, around 2 microseconds [
14]. Since bound electrons cannot provide a sufficient screening effect for the fusion process [
15,
16], a different approach using unbound (free) electrons is explored in the next section.
Screening by Dynamic Free Electron Oscillations
High-density free electrons are created when there are high frequency excitations which ions cannot follow due to their mass. In the case when there is a thin slab layer of electrons created because of the high centrifugal force, the resultant negative electric field will reduce the Coulomb barrier. We emphasize the utilization of repetitive excitation of electron emitters through electrical means. Given the ultrafast timescale of femtoseconds for the fusion process, the impact of such electron interactions will manifest within the critical layer.
As an example, we consider a plasma wave with the sinusoidal form of
where
n1 is the plasma wave amplitude and Λ is the wavelength. From Poisson’s equation, the corresponding electric potential energy can be found to be as follows:
The amplitude of the potential variation is thus the screening energy, which can be written as follows:
For a typical plasma wave induced by a visible or infrared laser, the wavelength is Λ ~ 10
−6 m [
17]. In this case, the screening potential is
Us = 4.6 keV for a plasma wave amplitude of
n1 = 10
25 m
−3. This energy is comparable to the screening energy for the muon-catalyzed hydrogen fusion (5 keV). Therefore, we expect an electron plasma wave of amplitude ~10
25 m
−3 around a hydrogen atom would result in a cross section close to the muon-catalyzed fusion. Apparently, such plasma waves should be easier to produce than the short-lived muons. The nonlinear collapse [
18,
19] of plasma waves can lead to the compression of even smaller spatial scales. These highly localized oscillating electric fields lead to ponderomotive forces that are proportional to the gradient of field intensities. These forces compress positive ions together and help to lower the Coulomb barrier between positively charged nuclei.
6. Ion–Neutral Coupling
Although neutrals do not experience electrical and/or magnetic forces, their rotation in the confinement region is dependent on their interaction with charged particles (
Figure 4). This interaction is facilitated by an ion–neutral coupling process, whereby a small number of charged particles transfer motion to the surrounding neutral particles. More importantly rotating neutrals are influenced by the centrifugal force; acceleration as high as 10
9 g has been observed.
B. Lehnert [
21] produced a partially ionized plasma centrifuge, where the motion of gas mixture is driven by a small amount of rotating plasma. Plasma motion is controlled by externally imposed crossed electric and magnetic fields; that is, an imposed radial electric field and current, via an applied voltage, between a cylindrical pair of electrodes and an imposed perpendicular axial magnetic field. Lehnert also reported high rotational velocities, large separation degrees, and stable velocity profiles could be attained at comparatively small power losses, within certain parameter ranges.
An outward electric field (E) coexists with an axial magnetic field (B) within the annular cavity. This magnetic field aligns perpendicularly to the radial electric field lines and parallels the surface of the cylindrical electrode. Under the influence of the cross-field phenomenon (E × B), charged particles, ions and electrons, undergo radial motion directed towards the outer cylindrical surface. This radial movement, perpendicular to the axial magnetic field, creates a Lorentz force that propels ions into azimuthal rotational motion, orthogonal to both the radial electric field (E) and axial magnetic field (B). Frequent high-frequency collisions between ions and neutral atoms result in their collective motion. Ions within the annular space experience electrostatic forces due to electric fields, where a relatively small number of ions suffice to drive numerous neutrals via ion–neutral coupling. Ions, serving to induce neutral rotation, can originate from various mechanisms, such as inductive or capacitive coupling. This coupling aligns the co-rotation of neutrals with positively charged particles. Under centrifugal compression, ions, electrons, and neutrals are pressed against the outer cylindrical surface. The aim is to position fusion at the chamber’s outer edge, where electrons, neutrals, and ions converge due to substantial centrifugal acceleration (>109 g). Centrifugal compression operates on the combined co-rotating ensemble of particles, including neutral atoms, positive ions, and electrons, compressing them into a thin, densely populated rotating layer of fusion reactant nuclei and trapped electrons. This thin, centrifugally compressed layer generates a significant electric field, exerting its influence on the desired reactants.
The process of ion–neutral coupling and the collaborative oscillations among reactant particles lead to a reduction in space charge and associated instabilities. When neutrals are included in the overall fusion reactions, the gain is higher than using the charge species alone.
The following equations describe how neutrals through their frequent collisions with ions can be made to follow the external electromagnetic excitations.
where
M and
m are the mass of ion and electron,
ni,e are the densities of ions and electrons,
vi,e are the velocities of ions and electrons,
pi,e are the momentums of ions and electrons,
E is the electric field,
B is the magnetic field, and the coupling term,
Pie, is the momentum change due to ion–electron interaction (note that
Pie = −
Pei).
Neglecting the viscosity tensor and
terms and adding Equations (16) and (17), the interaction terms are canceled, and we have the following:
Equation (18) can be written as follows:
where
is the combined ion–electron density, and the average velocity and effective electric current are (assuming
n ~
ni ~
ne).
Now, consider the interactions between the charge current and the neutrals. Their equations can be written as follows:
Equations (22) and (23) show that the neutrals can be influenced by
force through collisions with charges represented by
term. Computer simulations [
7] have yielded results indicating the possibility of accelerating neutrals to energies in the keV range. This suggests that significantly higher fusion cross sections can be achieved compared to the existing method.