Effects of magnetic configuration on hot electrons in highly charged ECR plasma

Abstract

To investigate the hot electrons in highly charged electron cyclotron resonance (ECR) plasma, Bremsstrahlung radiations were measured on two ECR ion sources at the Institute of Modern Physics. Used as a comparative index of the mean energy of the hot electrons, a spectral temperature, T spe , is derived through a linear fitting of the spectra in a semi-logarithmic representation. The influences of the external source parameters, especially the magnetic configuration, on the hot electrons are studied systematically. This study has experimentally demonstrated the importance of high microwave frequency and high magnetic field in the electron resonance heating to produce a high density of hot electrons, which is consistent with the empirical ECR scaling laws. The experimental results have again shown that a good compromise is needed between the ion extraction and the plasma confinement for an efficient production of highly charged ion beams. In addition, this investigation has shown that the correlation between the mean energy of the hot electrons and the magnetic field gradient at the ECR is well in agreement with the theoretical models.

Correlation of bremsstrahlung and energy distribution of escaping electrons to study the dynamics of magnetically confined plasma

“…These studies can be characterised based on whether or not the obtained results provide spatially and/or temporally resolved information, as well as based on the origin of the measured bremsstrahlung (plasma emission, thick target radiation induced by escaping electrons). Techniques resulting to volume integrated and time averaged results have been used most widely to probe the general plasma properties [6][7][8][9][10][11][12][13][14][15][16], but there has been also significant development in the use of spatially [17,18] and temporally [19] resolved methods. However, unambiguous de-convolution of either thick-target (wall) or plasma bremsstrahlung spectra to obtain the electron energy distribution (EED) of the escaping or confined electrons is seemingly impossible despite some notable efforts [13,20,21].…”

Effects of magnetic configuration on hot electrons in a minimum-B ECR plasma

“…Electron cyclotron resonance (ECR) ion sources are used to produce a wide range of ions, from singly charged to multiply charged ions (MCIs) and have been widely applied to both basic and applied scientific research due to their efficiency and reliability [1,2]. In the past decades, a series of well performing ECR ion sources were developed at the Institute of Modern Physics (IMP) [3][4][5][6][7][8][9][10] and continuous efforts were spent to deepen the understanding of the plasma mechanisms involved in these ion sources and thereby to further improve their performances [11][12][13][14][15][16].…”

“…This article deals with experimental studies of the hot electron population of a highly charged ECR ion source. As collisions between electrons and ions within the plasma volume lead to bremsstrahlung radiation, the analysis of bremsstrahlung spectra is a powerful diagnostic tool for studying the hot electron population [22,23] and can also be used to probe the electron heating mechanism in ECR produced plasmas, from compact all-permanent magnet [24] to large fully superconducting devices [13,25]. To compare our results with previous articles published on the same subject, bremsstrahlung measurement was chosen to diagnose the plasma of SECRAL-II ion source.…”

“…A number of previous studies taken on ECRISs [13,[25][26][27] show that the magnetic field configuration is extremely important for the production of hot electrons in minimum-B topology. Although these earlier studies showed important results, the mechanism behind the correlation of magnetic field parameters to the bremsstrahlung spectral temperature T s is not yet clear.…”

Effect of elastic modulus and thickness of the interlayer on the bond strength for ceramic coating-substrate system

“…These requirements can be met with a special coating on the substrate in the material protection field, especially ceramic and other brittle coating [1], because surface properties, such as wear resistance, high temperature and corrosive resistance, can be improved by the coating. Considerable methods are used to make the coating, such as thermal spraying, sol-gel method and thermal chemical reaction [2,3]. However it is still a challenge to obtain the good bond strength between the ceramic coating and substrate.…”