Hot roating plasma in the PSP-2 experiment

2008

Phys. Rev. Lett.

The wave-particle α-channeling effect is generalized to include rotating plasma. Specifically, radio frequency waves can resonate with α particles in a mirror machine with E × B rotation to diffuse the α particles along constrained paths in phase space. Of major interest is that the α-particle energy, in addition to amplifying the RF waves, can directly enhance the rotation energy which in turn provides additional plasma confinement in centrifugal fusion reactors. An ancillary benefit is the rapid removal of alpha particles, which increases the fusion reactivity.In magnetic mirror fusion devices, centrifugal forces can significantly enhance the magnetic confinement [1,2,3]. A radial electric field induces rapid E × B plasma rotation, leading to the centrifugal force that directly confines ions axially. Electrons are then confined axially through the ambipolar potential. The radial field thus not only enhances the plasma confinement, but also produces the necessary heating for the plasma, as injected cold neutral fuel atoms are seen as moving at the rotation velocity in the rotating frame. Lately there has been a renewed interest in this effect [4,5,6,7], strengthened by recent findings of reduced turbulence due to sheared rotation [8,9].What we show here is that in a DT (deuterium-tritium) centrifugal fusion reactor, the energy of α-particles, the byproducts of the fusion reaction, might be advantageously induced to directly produce this rotation. The predicted effect relies on exploiting the population inversion of the birth distribution of α particles. This is a generalization of the alpha channeling effect, where injected wave energy can be amplified at the expense of the α-particle energy, with the alpha particles concomitantly removed as cold particles [10]. In tokamaks, if the wave energy is damped on ions, the fusion reactivity might be doubled [11]. Similar advantageous uses of α-channeling can be expected in mirror machines [12]. With several waves, a significant amount of the α-particle energy can be advantageously channeled in both tokamaks [13] and mirrors [14]. However, in previous considerations of α-channeling, the plasma was not rotating strongly.In strongly rotating plasma, significant new effects can occur because there are two further reservoirs of particle energy, namely rotational and potential energy. For example, through a suitable choice of wave parameters, particles can now absorb wave energy yet cool in kinetic energy, with the excess energy being stored in potential energy. Alternatively, particle potential energy might be lost to wave energy with kinetic energy constant. These possibilities could not be achieved through particle manipulation in stationary systems, where the only coupling is between the kinetic energy with the wave energy. What is important for centrifugal mirror fusion is that radiofrequency waves can drive a radial α-particle current, with the dissipated power extracted from the α-particle birth energy, thereby maintaining the radial potential which produces the nece...

mentioning

confidence: 52%

Section: Figmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

αChanneling in a Rotating Plasma

2008

Phys. Rev. Lett.

“…The electrodes have typically reduced the rotation velocity to the Alfven CIV limit, or else required extensive conditioning to avoid this limit. 1, 12,29 In addition, the electrodes could be a source of instability and require sufficient density for conductivity. 9 Because eliminating the electrodes entirely is a critical issue, we note that this principle can still be used to produce rotation even if power loss is much larger than expected.…”

Section: Discussionmentioning

confidence: 99%

Alpha channeling in rotating plasma with stationary waves

2010

Physics of Plasmas

An extension of the alpha channeling effect to supersonically rotating mirrors shows that the rotation itself can be driven using alpha particle energy. Alpha channeling uses radiofrequency waves to remove alpha particles collisionlessly at low energy. We show that stationary magnetic fields with high n θ can be used for this purpose, and simulations show that a large fraction of the alpha energy can be converted to rotation energy.

“…This minimizes the overall cost and complexity of separation. We classify 10 km/s as moderate because rotation speeds over 100 km/s have been achieved recently in a Maryland experiment, and past rotating plasma experiments have reached 2,000 km/s [16,17]. However it is common for rotating plasmas to be limited to the Alfven critical ionization velocity (CIV), which is around 1 km/s for a plasma containing transuranic elements [18,19,20].…”

Section: Plasma Mass Separationmentioning

confidence: 99%

Plasma Mass Filters For Nuclear Waste Reprocessing

2011

Practical disposal of nuclear waste requires high-throughput separation techniques. The most dangerous part of nuclear waste is the fission product, which contains the most active and mobile radioisotopes and produces most of the heat. We suggest that the fission products could be separated as a group from nuclear waste using plasma mass filters. Plasmabased processes are well suited to separating nuclear waste, because mass rather than chemical properties are used for separation. A single plasma stage can replace several stages of chemical separation, producing separate streams of bulk elements, fission products, and actinoids. The plasma mass filters may have lower cost and produce less auxiliary waste than chemical processing plants. Three rotating plasma configurations are considered that act as mass filters: the plasma centrifuge, the Ohkawa filter, and the asymmetric centrifugal trap.