24 research outputs found
The Magnetic Centrifugal Mass Filter
Mass filters using rotating plasmas have been considered for separating nuclear waste and spent nuclear fuel. We propose a new mass filter that utilizes centrifugal and magnetic confinement of ions in a way similar to the asymmetric centrifugal trap. This magnetic centrifugal mass filter is shown to be more proliferation resistant than present technology. This filter is collisional and produces well confined output streams, among other advantages. _________________________________________________
Wave-particle Interactions In Rotating Mirrors
Wave-particle interactions in E×B rotating plasmas feature an unusual effect: particles are diffused by waves in both potential energy and kinetic energy. This wave-particle interaction generalizes the alpha channeling effect, in which radio frequency waves are used to remove alpha particles collisionlessly at low energy. In rotating plasmas, the alpha particles may be removed at low energy through the loss cone, and the energy lost may be transferred to the radial electric field. This eliminates the need for electrodes in the mirror throat, which have presented serious technical issues in past rotating plasma devices. A particularly simple way to achieve this effect is to use a high azimuthal mode number perturbation on the magnetic field. Rotation can also be sustained by waves in plasmas without a kinetic energy source. This type of wave has been considered for plasma centrifuges used for isotope separation. Energy may also be transferred from the electric field to particles or waves, which may be useful for ion heating and energy generation
Despite "super-human" performance, current LLMs are unsuited for decisions about ethics and safety
Large language models (LLMs) have exploded in popularity in the past few
years and have achieved undeniably impressive results on benchmarks as varied
as question answering and text summarization. We provide a simple new prompting
strategy that leads to yet another supposedly "super-human" result, this time
outperforming humans at common sense ethical reasoning (as measured by accuracy
on a subset of the ETHICS dataset). Unfortunately, we find that relying on
average performance to judge capabilities can be highly misleading. LLM errors
differ systematically from human errors in ways that make it easy to craft
adversarial examples, or even perturb existing examples to flip the output
label. We also observe signs of inverse scaling with model size on some
examples, and show that prompting models to "explain their reasoning" often
leads to alarming justifications of unethical actions. Our results highlight
how human-like performance does not necessarily imply human-like understanding
or reasoning.Comment: ML Safety Workshop, NeurIPS 202
Simulation of Alpha Particles in Rotating Plasma Interacting With a Stationary Ripple
Superthermal ExB rotation can provide magnetohydrodynamic (MHD) stability and enhanced confinement to axisymmetric mirrors. However, the rotation speed has been limited by phenomena at end electrodes. A new prediction is that rotation might instead be produced using a magnetic ripple and alpha particle kinetic energy, in an extension of the alpha channeling concept. The interaction of alpha particles with the ripple results in visually interesting and practically useful orbits
Alpha Channeling in a Rotating Plasma
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
On the stepwise nature of self-supervised learning
We present a simple picture of the training process of self-supervised
learning methods with joint embedding networks. We find that these methods
learn their high-dimensional embeddings one dimension at a time in a sequence
of discrete, well-separated steps. We arrive at this conclusion via the study
of a linearized model of Barlow Twins applicable to the case in which the
trained network is infinitely wide. We solve the training dynamics of this
model from small initialization, finding that the model learns the top
eigenmodes of a certain contrastive kernel in a stepwise fashion, and obtain a
closed-form expression for the final learned representations. Remarkably, we
then see the same stepwise learning phenomenon when training deep ResNets using
the Barlow Twins, SimCLR, and VICReg losses. Our theory suggests that, just as
kernel regression can be thought of as a model of supervised learning,
\textit{kernel PCA} may serve as a useful model of self-supervised learning
Alpha Channeling in a Rotating Plasma
The wave-particle alpha-channeling effect is generalized to include rotating
plasma. Specifically, radio frequency waves can resonate with alpha particles
in a mirror machine with ExB rotation to diffuse the alpha particles along
constrained paths in phase space. Of major interest is that the alpha-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.Comment: 4 pages and 3 figure
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Metrics For Comparing Plasma Mass Filters
High-throughput mass separation of nuclear waste may be useful for optimal storage, disposal, or environmental remediation. The most dangerous part of nuclear waste is the fission product, which produces most of the heat and medium-term radiation. Plasmas are well-suited to separating nuclear waste because they can separate many different species in a single step. A number of plasma devices have been designed for such mass separation, but there has been no standardized comparison between these devices. We define a standard metric, the separative power per unit volume, and derive it for three different plasma mass filters: the plasma centrifuge, Ohkawa filter, and the magnetic centrifugal mass filter. _________________________________________________
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Plasma Mass Filters For Nuclear Waste Reprocessing
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