Researchers determine a new method to measure high-energy-density plasmas and facilitate inertial confinement fusion

Researchers determine a new method to measure high-energy-density plasmas and facilitate inertial confinement fusion

Nature Communication (2022). DOI: 10.1038/s41467-022-30472-8″ width=”800″ height=”437″/>
Experimental setup. Diagram of the experimental setup for each shot: (i) selection of a proton beam with an energy of 500 keV from an initial broadband TNSA spectrum generated by the main beam, (ii) generation of a WDM sample by the beam heating, (iii) measurement of the energy spectrum of the protons of the selected beam after passing through the WDM target and (iv) characterization of the WDM sample by the SOP and the XPHG diagnostics. Typical raw experimental data acquired for each shot are presented for the magnet spectrometer as well as for SOP and XPHG diagnostics. Credit: Nature Communication (2022). DOI: 10.1038/s41467-022-30472-8

An international team of scientists has discovered a new method to advance the development of fusion energy through a better understanding of the properties of hot dense matter, an extreme state of matter similar to that found in the heart giant planets like Jupiter.

The findings, led by Sophia Malko of the U.S. Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL), detail a new technique for measuring the “stopping power” of nuclear particles in plasma using ultra-intense lasers with high repetition rate. Understanding the stopping power of protons is particularly important for inertial confinement fusion (ICF).

Powering the Sun and the Stars

This process contrasts with the creation of PPPL fusion, which heats plasma to temperatures of a million degrees in magnetic confinement facilities. Plasma, the hot, charged state of matter composed of free electrons and atomic nuclei, or ions, powers fusion reactions in both types of research, which aim to replicate on Earth the fusion that powers the sun and the stars as a safe and clean source of energy. and virtually unlimited energy to generate the world’s electricity.

“Stopping power” is a force acting on charged particles due to collisions with electrons in matter that result in a loss of energy. “For example, if you don’t know the stopping power of protons, you can’t calculate the amount of energy deposited in the plasma and therefore design lasers with the right energy level to create fusion ignition” , said Malko, lead author of a paper that describes the findings in Nature Communication. “Theoretical descriptions of stopping power in high-energy-density matter and especially hot dense matter are difficult, and measurements are largely lacking,” she said. “Our paper compares experimental data of proton energy loss in hot dense matter with theoretical models of stopping power.”

The Nature Communication research has investigated the stopping power of protons in a largely unexplored regime using low-energy ion beams and hot dense laser-produced plasmas. To produce the low-energy ions, the researchers used a special magnet-based device that selects the low-energy fixed-energy system from a broad spectrum of protons generated by the interaction of lasers and plasma. The selected beam then passes through hot, laser-driven dense matter and its energy loss is measured. Theoretical comparison with the experimental data showed that the closest match was in clear disagreement with the classical models.

Instead, the closest agreement has come from recently developed first-principle simulations based on a many-body or interacting quantum mechanical approach, Malko said.

Precise stop measurements

Precise shutdown measurements can also advance understanding of how protons produce what is known as rapid ignition, an advanced scheme of inertial confinement fusion. “In proton-driven rapid ignition, where protons must heat compressed fuel from a very low temperature state to a high temperature, the stopping power of the proton and the state of the material are closely related”, Malko said.

“The stopping power depends on the density and the temperature of the state of the material,” she explained, and both are in turn affected by the energy deposited by the proton beam. “Thus, uncertainties in stopping power lead directly to uncertainties in total proton energy and laser energy needed for ignition,” she said.

Malko and his team are performing new experiments at Colorado State University’s DOE LaserNetUS facilities to extend their measurements to the so-called Bragg peak region, where the maximum energy loss occurs and theoretical predictions are most uncertain.

The co-authors of this article included 27 researchers from the United States, Spain, France, Germany, Canada and Italy.

Discover a new way to bring the energy that powers the sun and stars to Earth

More information:
S. Malko et al, Low Velocity Proton Stopping Measurements in Hot Dense Carbon, Nature Communication (2022). DOI: 10.1038/s41467-022-30472-8

Provided by Princeton Plasma Physics Laboratory

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