Experimental setup. Scheme of experimental setup for each shot: (1) selection of a 500 kV energy proton beam from the initial broadband TNSA spectrum generated by the main beam, (2) generation of a WDM sample by the heater beam, (3) downshift measurement of the proton energy spectrum of the selected beam after Passing through the WDM target and (4) characterization of the WDM sample by SOP and XPHG diagnostics. Typical raw experimental data obtained for each snapshot of the magnetometer as well as SOP and XPHG diagnoses are shown. attributed to him: Nature Connections (2022). DOI: 10.1038 / s41467-022-30472-8
An international team of scientists has discovered a new way to develop fusion energy by further understanding the properties of warm dense matter, an extreme state of matter similar to that found in the cores of giant planets such as Jupiter.
The results, led by Sophia Malko of the US Department of Energy’s Princeton Plasma Physics Laboratory (PPPL), detail a new technique for measuring the “stopping force” of nuclear particles in plasma using an ultrafast, high-repetition laser. Understanding the proton’s stopping power is particularly important for integrating into self-confinement (ICF).
Running sun and stars
This process contrasts with the creation of fusion at PPPL, which heats plasma to temperatures of up to a million degrees in magnetic confinement facilities. Plasma, the hot, charged state of matter made up of free electrons and atomic nuclei or ions, fuels fusion reactions in both types of research, aimed at reproducing the fusion that powers the sun and stars as a safe and clean source. and nearly limitless power to generate electricity in the world.
The “stopping force” is a force that affects charged particles due to the collision of electrons in the material resulting in a loss of energy. “For example, if you don’t know the stopping power of a proton, you cannot calculate the amount of energy deposited in the plasma, and therefore design lasers at the appropriate energy level to create fusion ignition,” said Malko, lead author of a research paper outlining the results in Nature Connections. Theoretical descriptions of the stopping power in a substance with a high energy density, especially in warm dense material are tricky, and measurements are largely missing. Our paper compares the experimental data for the energy loss of a proton in a warm dense material with theoretical models of the stopping force.
The Nature Connections The investigation investigated the power to stop the proton in a largely unexplored system using low-energy ion beams and warm, dense laser-produced plasmas. To produce the low-energy ions, the researchers used a special magnet-based device that selects the low-energy constant energy regime from a broad proton spectrum generated by the interaction of the laser and plasma. The selected beam then passes through a warm, dense laser-driven material and its energy loss is measured. The theoretical comparison with the experimental data showed that the closest matched sharply with the classical models.
Instead, the closest agreement came from recently developed first-principle simulations based on a multibody or interacting quantum mechanical approach, Malko said.
Accurate stop measurements
Accurate stop measurements can also advance the understanding of how protons produce what is known as fast ignitionadvanced scheme of Inertial confinement fusion. “In rapid proton-driven ignition, where the protons must heat the compressed fuel from very low to high temperature states, the proton’s stopping power and the state of the material are tightly related,” Malko said.
She explained that “the stopping force depends on the density and temperature of the state of matter,” both of which are in turn influenced by the energy deposited by the proton beam. “Thus, the uncertainties in the stopping force directly lead to the uncertainties in the total energy of the proton and laser “The energy needed for ignition,” she said.
Malko and her team are conducting new experiments at DOE LaserNetUS facilities at Colorado State University to extend their measurements to the so-called Bragg peak region, where maximum power loss occurs and where theoretical predictions are uncertain.
This paper was co-authored by 27 researchers from the United States, Spain, France, Germany, Canada and Italy.
Malko et al., the proton stopped measurements at low speed in warm dense carbon, Nature Connections (2022). DOI: 10.1038 / s41467-022-30472-8
Princeton Plasma Physics Laboratory
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