Diagnostics of the magnetized low-pressure hydrogen plasma jet: Molecular regime

Qing, Z Zhou; Otorbaev, DK; Brussaard, Gjh Seth; Sanden, van de Mcm Richard; Schram, DC Daan

doi:10.1063/1.362930

Cited by 56 publications

(42 citation statements)

References 51 publications

(82 reference statements)

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“…H − ions recombine with H 2 + to form hydrogen atoms in highly excited states, causing population inversion. This work continues the discussion of MAR processes in a cascaded arc [19,22]. New evidence for the existence of MAR processes is given by examining atomic state distributions and using a collisional radiative model.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the production rate of each excited state [19] correlates very well with the shape of the cross section of H 2 + + H − [24]. To study the importance of these molecular processes a more advanced CR model is needed in which molecular processes are included [22,41]. This is necessary to prove that the observed population inversion in the blue afterglow is caused by MAR processes.…”

Section: -7mentioning

confidence: 99%

“…The intensity of the emission is proportional to the density of the upper level u. For an optically thin plasma [22], the spectral emission coefficient…”

Section: B Optical Emission Spectroscopymentioning

confidence: 99%

“…[21] using a Radiation frequency (RF) plasma. However, Qing et al [22] concluded that three-body recombination cannot be responsible for the observed population inversion in the magnetized hydrogen expansion because of the too low electron density and too high electron temperature [23]. Both parameters were obtained with a Langmuir double probe.…”

Section: Introductionmentioning

confidence: 99%

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Population inversion in a magnetized hydrogen plasma expansion as a consequence of the molecular mutual neutralization process

et al. 2011

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A weakly magnetized expanding hydrogen plasma, created by a cascaded arc, was investigated using optical emission spectroscopy. The emission of the expanding plasma is dominated by H α emission in the first part of the plasma expansion, after which a sharp transition to a blue afterglow is observed. The position of this sharp transition along the expansion axis depends on the magnetic field strength. The blue afterglow emission is associated with population inversion of the electronically excited atomic hydrogen states n = 4 − 6 with respect to n = 3. By comparing the measured densities with the densities using an atomic collisional radiative model, we conclude that atomic recombination processes cannot account for the large population densities observed. Therefore, molecular processes must be important for the formation of excited states and for the occurrence of population inversion. This is further corroborated at the transition from red to blue, where a hollow profile of the excited states n = 4 − 6 in the radial direction is observed. This hollow profile is explained by the molecular mutual neutralization process of H 2 + with H − , which has a maximum production for excited atomic hydrogen 1 − 2 cm outside the plasma center.

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Section: Introductionmentioning

confidence: 99%

Section: -7mentioning

confidence: 99%

“…The intensity of the emission is proportional to the density of the upper level u. For an optically thin plasma [22], the spectral emission coefficient…”

Section: B Optical Emission Spectroscopymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Population inversion in a magnetized hydrogen plasma expansion as a consequence of the molecular mutual neutralization process

et al. 2011

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“…The several lines shown in Fig. 2 are assigned perfectly to the transitions of the Fulcher-α system ( [5]. Figure 3 shows an optical emission spectrum in this wavelength range observed from the same plasma as that shown in Fig.…”

Section: The Japan Society Of Plasma Science and Nuclear Fusion Researchmentioning

confidence: 94%

Dramatic Enhancement of OH(A2Σ+) Density in a Recombining Hydrogen Plasma

Shibagaki

Asakawa

Hayashi

et al. 2008

Plasma and Fusion Research

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Optical emission spectra in the wavelength range of molecular hydrogen were observed in both ionizing and recombining plasma modes of hydrogen discharges. The optical emission spectrum from the ionizing plasma was dominated by the Fulcher-α system (a 3 Σ + g − d 3 Π − u ) of molecular hydrogen. On the other hand, the optical emission spectrum from the recombining plasma was composed of many lines, and was completely different from the spectrum of the ionizing plasma. The many peaks observed from the recombining plasma were assigned to the Recombining plasmas are important in nuclear fusion research since they are closely related to plasma detachment, which is considered to be a promising approach for avoiding excess heat flux to the divertor plate in a nuclear fusion machine [1]. It is well known that in a recombining plasma, highly excited states are populated significantly via three-body recombination, and the optical emission spectrum is considerably different from that of an ionizing plasma [2]. In the case of a recombining hydrogen plasma, the optical emission spectrum of atomic hydrogen has been investigated well, however, the optical emission spectrum in the wavelength region of molecular hydrogen has not been investigated thoroughly. Therefore, in this study, we examine the optical emission spectrum in the wavelength region of molecular hydrogen in a recombining hydrogen plasma.The plasma source [3] was a linear machine with a uniform magnetic field of 350 G along the cylindrical axis. An rf power source at 13.56 MHz was connected to a helical antenna wound around a glass tube with an inner diameter of 1.6 cm. The glass tube was attached to a stainless steel vacuum chamber. A plasma column with the diameter same as the glass tube was confined radially by the external magnetic field. We used pure hydrogen for discharge in this experiment. The plasma was produced in a pulsed mode with a repetition frequency of 10 Hz and a discharge duration of 4 ms to avoid over-heating of the author's e-mail: sasaki@nuee.nagoya-u.ac.jp machine. The diagnostic method was conventional optical emission spectroscopy, which was performed in the downstream region at a distance of 22 cm from the helical antenna using a spectrograph with a focal length of 50 cm. The spectrum was recorded using a charge-coupled device camera with a gated image intensifier (ICCD camera). The gate of the ICCD camera was opened from 3.95 to 3.99 ms after the initiation of the pulsed discharge.Two types of discharge were observed when the gas pressure was higher than 30 mTorr. Low rf power resulted in a low-density mode discharge with an electron density of the order of 10 11 cm −3 . A high-density mode discharge with an electron density of the order of 10 12 cm −3 was obtained at rf powers higher than ∼1.5 kW [3]. On the other hand, when the gas pressure was lower than 30 mTorr, a low-density mode discharge was obtained even at a high rf power of 3 kW. In the high-density mode discharges at gas pressures lower than 50 mTorr and all the low-density mo...

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A New Design for Secondary Electron Measurement and Application

Liu

Yan

2018

Springer Proceedings in Physics

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Diagnostics of the magnetized low-pressure hydrogen plasma jet: Molecular regime

Cited by 56 publications

References 51 publications

Population inversion in a magnetized hydrogen plasma expansion as a consequence of the molecular mutual neutralization process

Population inversion in a magnetized hydrogen plasma expansion as a consequence of the molecular mutual neutralization process

Dramatic Enhancement of OH(A2Σ+) Density in a Recombining Hydrogen Plasma

A New Design for Secondary Electron Measurement and Application

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