Bright Spot Characterization of Low dI/dt X-pinch Plasmas using Soft X-ray Spectroscopy with Bennett Relation

Fuente: arXiv
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Main Authors: Choi, YeongHwan, Cha, Muhyeop, Lee, Hakmin, Chi, Hsiao-Chien, Choi, Seongmin, Bong, Seungmin, Jeon, Seonghun, Choi, Ookjin, Ghim, Young-chul, Hwang, Yong-Seok, Chung, Kyoung-Jae
Format: Preprint
Published: 2026
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author Choi, YeongHwan
Cha, Muhyeop
Lee, Hakmin
Chi, Hsiao-Chien
Choi, Seongmin
Bong, Seungmin
Jeon, Seonghun
Choi, Ookjin
Ghim, Young-chul
Hwang, Yong-Seok
Chung, Kyoung-Jae
author_facet Choi, YeongHwan
Cha, Muhyeop
Lee, Hakmin
Chi, Hsiao-Chien
Choi, Seongmin
Bong, Seungmin
Jeon, Seonghun
Choi, Ookjin
Ghim, Young-chul
Hwang, Yong-Seok
Chung, Kyoung-Jae
contents This study investigates the characteristics of X-pinch plasmas driven under low current rise rate ($dI/dt$) conditions using soft x-ray spectroscopy combined with the Bennett relation. X-pinch experiments were conducted on the SNU X-pinch device using copper wires at a low $dI/dt$ of 0.2-0.3 kA/ns. The resulting 1-10 keV soft x-ray signals, measured by an x-ray filtered AXUV photodiode array (XFPA), exhibit significant nonlinear effects due to the high intensity of the soft x-ray pulses. This work characterizes the nonlinear behavior of the AXUV-HS5 Si PIN photodiodes under intense pulsed radiation using a pulsed laser. We identified a charge conservation property that the total collected charge remains proportional to the incident pulse energy despite temporal profile distortion. Based on this diagnostic finding, we developed and applied a new framework for plasma parameter estimation. By combining a spherical emission model with the Bennett equilibrium, this approach determines that the soft x-ray source plasma is a 'bright spot', characterized by a plasma density $n_e \sim 10^{21} \text{ cm}^{-3}$, size $d \sim 30-40\ μ\text{m}$, electron temperature $T_e \sim 1 \text{ keV}$, and an emission duration $t_B \sim 1 \text{ ns}$, rather than an extremely compressed 'hot spot'.
format Preprint
id arxiv_https___arxiv_org_abs_2603_27927
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Bright Spot Characterization of Low dI/dt X-pinch Plasmas using Soft X-ray Spectroscopy with Bennett Relation
Choi, YeongHwan
Cha, Muhyeop
Lee, Hakmin
Chi, Hsiao-Chien
Choi, Seongmin
Bong, Seungmin
Jeon, Seonghun
Choi, Ookjin
Ghim, Young-chul
Hwang, Yong-Seok
Chung, Kyoung-Jae
Plasma Physics
Instrumentation and Detectors
This study investigates the characteristics of X-pinch plasmas driven under low current rise rate ($dI/dt$) conditions using soft x-ray spectroscopy combined with the Bennett relation. X-pinch experiments were conducted on the SNU X-pinch device using copper wires at a low $dI/dt$ of 0.2-0.3 kA/ns. The resulting 1-10 keV soft x-ray signals, measured by an x-ray filtered AXUV photodiode array (XFPA), exhibit significant nonlinear effects due to the high intensity of the soft x-ray pulses. This work characterizes the nonlinear behavior of the AXUV-HS5 Si PIN photodiodes under intense pulsed radiation using a pulsed laser. We identified a charge conservation property that the total collected charge remains proportional to the incident pulse energy despite temporal profile distortion. Based on this diagnostic finding, we developed and applied a new framework for plasma parameter estimation. By combining a spherical emission model with the Bennett equilibrium, this approach determines that the soft x-ray source plasma is a 'bright spot', characterized by a plasma density $n_e \sim 10^{21} \text{ cm}^{-3}$, size $d \sim 30-40\ μ\text{m}$, electron temperature $T_e \sim 1 \text{ keV}$, and an emission duration $t_B \sim 1 \text{ ns}$, rather than an extremely compressed 'hot spot'.
title Bright Spot Characterization of Low dI/dt X-pinch Plasmas using Soft X-ray Spectroscopy with Bennett Relation
topic Plasma Physics
Instrumentation and Detectors
url https://arxiv.org/abs/2603.27927