Abstract
A new Nd:YAG laser Thomson scattering (TS) system has been developed to explore the mechanism of high-beta plasma formation in the RT-1 device. The TS system is designed to measure electron temperatures (Te) from 10 eV to 50 keV and electron densities (ne) of more than 1.0 × 1017 m-3. To measure at the low-density limit, the receiving optics views the long scattering length (60 mm) using a bright optical system with both a large collection window (260-mm diameter) and large collection lenses (300-mm diameter, a solid angle of ∼68 × 10-3 str). The scattered light of the 1.2-J Nd:YAG laser (repetition frequency: 10 Hz) is detected with a scattering angle of 90° and is transferred via a set of lenses and an optical fiber bundle to a polychromator. After Raman scattering measurement for the optical alignment and an absolute calibration, we successfully measured Te = 72.2 eV and ne = 0.43 × 1016 m-3 for the coil-supported case and Te = 79.2 eV and ne = 1.28 × 1016 m-3 for the coil-levitated case near the inner edge in the magnetospheric plasmas.
Highlights
The Ring Trap 1 (RT-1) device creates a laboratory magnetosphere that is obtained via a levitated superconducting ring magnet in a vacuum.1 The RT-1 experiment forms a peaked density profile, which is spontaneously created via “inward diffusion.”2,3 Stable confinement of high-beta plasmashas been reported in RT-1 magnetospheric plasmas.3The coexistence of electrons with heterogeneous energies has recently been found via spectroscopic measurements of the heliumline ratio and X-ray measurements in the RT-1
We developed a density reconstruction method from the interferometer data2,4 and modified it by introducing a new model function and a global optimization fit to obtain a realistic profile
We have started the development of a TS diagnostic system for the RT-1. 11 a)
Summary
The Ring Trap 1 (RT-1) device creates a laboratory magnetosphere that is obtained via a levitated superconducting ring magnet in a vacuum. The RT-1 experiment forms a peaked density profile, which is spontaneously created via “inward diffusion.” Stable confinement of high-beta plasmas (local electron beta ~ 1). The Ring Trap 1 (RT-1) device creates a laboratory magnetosphere that is obtained via a levitated superconducting ring magnet in a vacuum.. The RT-1 experiment forms a peaked density profile, which is spontaneously created via “inward diffusion.” Stable confinement of high-beta plasmas (local electron beta ~ 1). High-energy electrons are trapped in the outer confinement region. This result infers a spatial structure similar to the. Even though the helium-line ratio-spectroscopy provides the electron density and the temperature for the low-energy component, an accurate profile of the neutral density is necessary to estimate the local quantities. High-Temperature Plasma Diagnostics (HTPD 2018) in San Diego, California, USA. This article describes the development of the TS diagnostic system for the RT-1. The initial results of the TS measurement for the RT-1 plasma are shown at the end of the article
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