Resonance surface, microwave power absorption, and plasma density distribution in an electron cyclotron resonance ion source

Salahshoor, M.; Aslaninejad, M.

doi:10.1103/physrevaccelbeams.22.043402

Cited by 8 publications

(2 citation statements)

References 17 publications

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“…Therefore, for the preferential heating of heavy ions by the damping of the wave, the ion temperature of the heavy isotopes should be slightly more than that of the lighter isotopes. As the heavy ions are confined within the hot core of the plasma, 33 we can expect a little difference in the temperatures of heavy (slightly more) and lighter isotopes in a mixed ECR plasma. However, the large density of heavier isotopes increases the critical velocity and therefore, the wave must travel at a larger phase velocity for heating the heavier isotopes.…”

Section: Resultsmentioning

confidence: 99%

Studies of pure and nitrogen gas mixed xenon ECR plasma: Signature of abundance dependent unusual trends in isotope anomaly

2022

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We report the effect of N 2 gas-mixing in the xenon electron cyclotron resonance (ECR) plasma, and abundance-dependent novel, exciting and unusual trends of the isotope anomaly. The xenon plasma was produced using a 10 GHz all-permanentmagnet NANOGAN ECR ion source, and the charge state distributions of naturally abundant six stable xenon isotopes with and without N 2 gas-mixing (at 25%, 50%, and 75%) were recorded. The intensity ratio of the heavier to lighter isotope, where the heavier isotope is less abundant, showed a clear signature of the isotope anomaly as explained by the linear Landau wave damping theory. Contrary to the theoretical prediction that the isotope anomaly should vanish with a relatively large fraction of the heavier isotope in mixed plasmas, the trends of intensity ratios observed in such cases are very unusual and have almost the mirror-symmetrical shapes of those trends recorded with less abundant heavier isotope. Further, the effect of relative mass difference on the isotope anomaly was also evidenced. The N 2 gas-mixing of the xenon plasma at 25% and 50% shifted the entire charge state distribution toward the higher intensity side owing to the supply of additional electrons that caused high ionization efficiency. However, a prominent gas-mixing effect was observed at 75% of N 2 mixing in the xenon plasma beyond the +7 charge state. The abundancedependent unusual trends in isotope anomaly have been explained by considering different ionic temperatures, ion heating by the wave damping, and Coulomb scattering in the core of the plasma.charge state distribution, electron cyclotron resonance (ECR) plasma, gas mixing effect, isotope anomaly, low energy accelerator, mass analyzer | INTRODUCTIONThe capability of producing multiply charged positive ions via the electron-impact ionization without using any cathode/filament made the electron cyclotron resonance ion sources (ECRIS) very popular among the accelerator physicists. [1][2][3][4][5][6][7] The intensities in ECRIS are mainly governed by the ion-confinement using the magnetic fields. In a typical structure, multipole permanent magnets are used for the radial confinement of the ions, whereas the axial confinement of the ions is achieved either by the permanent magnets or the electromagnets. 8,9 The fourth generation high-frequency ECRIS utilized superconducting magnetic coils for the axial confinement of the ions. [10][11][12] The resonant electrons, which have a gyration frequency equals to the frequency of the input electromagnetic wave, gain enough kinetic energy to ionize the gaseous atom/molecules and yield intense plasma. 13

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Section: Resultsmentioning

confidence: 99%

Studies of pure and nitrogen gas mixed xenon ECR plasma: Signature of abundance dependent unusual trends in isotope anomaly

2022

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“…This software has already presented its capability for simulating the plasma sources as well as the electromagnetic fields and the particle trajectories [55]. It has also been extensively used to simulate MS devices [56][57][58][59][60][61][62] and other types of plasma sources such as gliding arc discharge [63], vacuum arc discharge [64], plasma arc welding [65], atmospheric plasma jet [66][67][68], dielectric barrier discharge [69], capacitively coupled plasma [70], inductively coupled plasma [71], microwave plasma [72] and electron cyclotron resonance plasma [73,74].…”

Section: Simulation Modelmentioning

confidence: 99%

Electron trapping efficiency of a magnetron sputtering cathode

Salahshoor

2024

Plasma Sources Sci. Technol.

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A common feature of all types of magnetron sputtering assemblies is an effective confinement of electrons by an appropriate combination of electric and magnetic fields.Therefore, studying the motions of electrons in the fields of magnetron assemblies is of particular importance.Here, we systematically analyze the electron motions in front of a typical DC magnetron sputtering cathode.We first calculate the profiles of the magnetron's magnetic field for balanced and two types of unbalanced configurations.Then, we compute the profiles of the cathode's electric field before the gas discharge and after the plasma formation.A semi-analytical model is utilized to compute the plasma potential.We then track the motion of electrons released from the target and electrons produced through impact ionization of the background gas in the prescribed fields.A Monte Carlo model is implemented to consider electron-gas collisions and a mixed boundary condition is employed to account for electron-wall interactions.The study analyzes the impact of field profiles on the cathode's efficiency in trapping electron by examining electron escape from the magnetic trap and electron recapture at the target surface.It is shown that the presence of plasma in all configurations leads to a significant increase in the trapping efficiency and the ionization performance, as well as a decrease in the recapture probability.These effects are attributed to the high electric field developed in the cathode sheath.Moreover, we statistically analyze the trapping efficiency by illustrating the spatial distributions of electron locations in both axial and radial dimensions.It is demonstrated that during their azimuthal drift motion, the electrons released from the middle region at the target surface have the smallest range of axial and radial locations, in all configurations in the absence of plasma.Finally, the impact of field profiles on the average energies of electrons is discussed.

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