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  • Online Resource  (14)
  • AIP Publishing  (14)
  • Zhao, Wei  (14)
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  • Online Resource  (14)
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  • AIP Publishing  (14)
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  • 1
    In: Review of Scientific Instruments, AIP Publishing, Vol. 90, No. 6 ( 2019-06-01)
    Abstract: Surface modification technique of secondary electron emission (SEE) characteristics of materials, which is utilized to suppress or promote the SEE from material surface under electron bombardment, has extensive applications in a variety of fields. Measurement of the secondary electron yield (SEY) and the secondary electron spectrum (SES) before and after surface modification is essential for the evaluation of effectiveness and the investigation of mechanism of material modification. A SEY and SES measurement system is reported in this article. The comparative measurements of the total SEY, the true SEY, the backscattered electron yield, and the SES of nickel and free-standing vertical graphene, which was grown in situ on the surface of nickel substrate by plasma enhanced chemical vapor deposition, were performed using this system. The measurement results demonstrate that this system could facilitate the study of surface modification on the SEE characteristics of conductive materials.
    Type of Medium: Online Resource
    ISSN: 0034-6748 , 1089-7623
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 209865-9
    detail.hit.zdb_id: 1472905-2
    SSG: 11
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  • 2
    In: Physics of Plasmas, AIP Publishing, Vol. 30, No. 4 ( 2023-04-01)
    Abstract: A one-dimensional self-consistent fluid model was employed to comparatively investigate the influence of pre-ionization on the helium direct-current glow discharge in the large gap and the small gap at atmospheric pressure. For the large-gap and small-gap discharges, the negative glow space and the cathode fall layer are both offset to the cathode with the increase in pre-ionization, which is mainly ascribed to the decrease in charged particle density in the original negative glow space as a result of the increased probability of collision and recombination between ions and electrons, and the new balance between the positive and negative charges established at the distance closer to the cathode. The electron density tends to grow in the negative glow space due to the elevated pre-ionization, while the ion density exhibits an overall downward tendency in the cathode fall layer because the increase in secondary electrons produces more newly born electrons that neutralize more ions via the recombination reaction. Thanks to the pre-ionization, a significant reduction of sustaining voltage and discharge power is obtained in both the large-gap and small-gap discharges. A remarkable characteristic is that the absent positive column in the small-gap discharge comes into being again due to the pre-ionization. Moreover, with the increase in the pre-ionization level, the potential fall shifts from the cathode fall layer to the positive column in the large-gap discharge, while it is always concentrated in the cathode fall layer in the small-gap discharge.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2023
    detail.hit.zdb_id: 1472746-8
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  • 3
    In: Applied Physics Letters, AIP Publishing, Vol. 102, No. 3 ( 2013-01-21)
    Abstract: A stable diffuse large-volume air plasma source was developed by using argon-induced dielectric-barrier discharges at atmospheric pressure. This plasma source can be operated in a filamentary discharge with the average areal power density of 0.27 W/cm2 and the gas temperature of 315±3 K. Spatial measurement of emission spectrum and temperature indicates that this plasma is uniform in the central region along the transverse direction. It is also found that the formation of diffuse air plasma mainly lies in the creation of sufficient seed electrons by the Penning effect through collisions between two argon or nitrogen metastables at low electric fields.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    RVK:
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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  • 4
    In: Physics of Plasmas, AIP Publishing, Vol. 27, No. 4 ( 2020-04-01)
    Abstract: A two-dimensional fluid model was used to investigate the characteristics of a multiple-current-pulse dielectric barrier discharge (DBD) equipped with ring electrodes in helium at atmospheric pressure. The simulation results show that the discharge at peak moment follows the Townsend mode in the DBD with two current pulses in each half cycle. However, when there are three or four current pulses in each half cycle, the discharge mode at the first current peak transforms to the glow mode. Additionally, for the first and third current pulse, the breakdown first occurs in the radial center of the ring electrodes. But for the discharge in the second and fourth current pulse, it ignites from the periphery of the ring electrodes. Moreover, the discharge structure, i.e., the radial spatial distributions of current density, electron density, and electric field at peak moments, shows a feature of alternation between (1) higher current density, electron density, and electric field locating in the radial center of ring electrodes (center-advantage) and (2) higher current density, electron density, and electric field locating in the periphery of ring electrodes (periphery-advantage). This behavior is attributed to the fact that non-uniform surface charge accumulation during the previous discharge has different effects on the electric field in the gas gap in the subsequent discharge.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 1472746-8
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  • 5
    In: Physics of Plasmas, AIP Publishing, Vol. 26, No. 1 ( 2019-01-01)
    Abstract: A two-dimensional fluid model was used to investigate the characteristics of helium dielectric barrier discharge (DBD) equipped with ring electrodes at atmospheric pressure. Simulation results show that the transition of discharge also exists as the traditional parallel-plate DBD. The discharge mode translates from the Townsend mode to the glow mode during the rising phase and returns to the Townsend mode in the falling phase of the discharge. Meanwhile, symmetric discharge current and current densities at different radial positions are observed in each cycle, and the current density peak at the radial center of the ring electrode is always higher than that at other positions. In addition, the charged particles follow a periphery-advantage spatial distribution, and the relative temporal variation of charged particles is faster in the periphery than in the central region because of the higher electric field existing there. Moreover, the density of surface charges assembled in the periphery changes faster than that in the central region of the upper dielectric barrier and exhibits an uneven periphery-advantage distribution, which is also ascribed to the higher electric field in the periphery resulted from the ring electrode configuration. Comparing the ring electrode DBD with the traditional one indicates that an inverse discharge structure is observed between the two electrode configurations.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2019
    detail.hit.zdb_id: 1472746-8
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  • 6
    In: Physics of Plasmas, AIP Publishing, Vol. 24, No. 4 ( 2017-04-01)
    Abstract: A two-dimensional self-consistent fluid model was employed to investigate the spatiotemporal characteristics of discharges in atmospheric pressure argon (Ar) dielectric barrier discharge driven by a Gaussian voltage. The simulation results show that a discharge with multiple current pulses occurs each half-cycle in the gas gap. A transition from the Townsend mode to the glow mode is observed with the increasing applied voltage each half-cycle at a lower driving frequency (7.5 kHz). It is also found that the glow mode survives all the discharge phases at a higher driving frequency (12.5 kHz and 40 kHz). The change in the discharge mode with the driving frequency mainly lies in the fact that a lot of charged particles created in the discharge gap have no enough time to drift and diffuse around, and then these particles are assembled in the discharge space at higher frequency. Additionally, the spatial distributions of the electron density indicate that a center-advantage discharge is ignited at the driving frequencies of interest, resulting in the radial non-uniformity of discharge because of the edge effects. However, this overall non-uniformity is weakened with the driving frequency increased to 40 kHz, at which concentric ring patterns are observed. These distinct behaviors are mainly attributed to the fact that many charged particles generated are trapped in the gas gap and then accumulated to make the extension along the radial direction due to the charged particles transport and diffusion, and that the effective overlapping of a large number of avalanches induced by the increased “seed” electron density with the driving frequency. Meanwhile, the surface charged particles accumulated on the dielectric barriers are also shown to play a role in the formation of the discharge structure.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2017
    detail.hit.zdb_id: 1472746-8
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  • 7
    In: Physics of Plasmas, AIP Publishing, Vol. 27, No. 7 ( 2020-07-01)
    Abstract: A two-dimensional fluid model was used to investigate the characteristics of helium dielectric-barrier discharge (DBD) equipped with double-ring electrodes at atmospheric pressure. Simulation results show that although the temporal evolutions of discharge current and current density at different radial positions exhibit the same or similar characteristics to those in traditional DBD, a distinctive spatial discharge structure is observed during the discharge process. The spatial distribution of electron density at current peak moments exhibits a periodical complementary feature between the center-advantage and the periphery-advantage with the inner ring electrode covering the radial axis from 0.5 to 1.0 mm. When the inner ring electrode covers the radial axis from 1.0 to 1.5 mm, the spatial distribution of electron density satisfies another periodical complementary behavior between the electrode-center-advantage and the coexistence of periphery-advantage and center-advantage. These complementary discharge features mainly result from non-uniform electric field and surface charge distribution at the end of the previous discharge. The difference of the discharge structure between the two cases is attributed to the fact that Laplacian field distributions are largely dependent on the arrangement of double-ring electrodes. Our observations show that electrode geometry plays an important role in the formation of the discharge structure.
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2020
    detail.hit.zdb_id: 1472746-8
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  • 8
    In: AIP Advances, AIP Publishing, Vol. 12, No. 5 ( 2022-05-01)
    Abstract: A self-consistent two-dimensional fluid model is employed to investigate the coaxial–coplanar dielectric-barrier discharge (DBD) excited by the sinusoidal voltage in atmospheric helium. Simulation results show that there are two current pulses in the positive half cycle, but only one in the negative half cycle. The discharge is transformed from the Townsend-like mode, through the glow-like mode, and back to the Townsend-like mode in both the positive and negative half cycles, during which the electric field line exhibits an arc-shape profile due to the configuration of coaxial–coplanar electrodes. In the glow-like mode, the cathode fall is located near the inner edge of the ground electrode at the first positive current peak, but close to the outer edge of the ground electrode at the second positive current peak. At the negative current peak, the cathode fall is distributed near the outer edge of the high voltage electrode. Since the instantaneous anode and the instantaneous cathode are on the same side of the discharge space, the dielectric layer is simultaneously covered by positive and negative surface charges due to the movement of charged particles. It is also found that the surface charge density changes significantly on the dielectric layer facing the electrodes. A further study reveals that a stronger discharge always occurs in the central circular area and an alternately complementary discharge takes place in the periphery ring area in the positive half cycle due to the activator–inhibitor effect. This feature is helpful for producing uniform plasma in a whole cycle of DBD.
    Type of Medium: Online Resource
    ISSN: 2158-3226
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2022
    detail.hit.zdb_id: 2583909-3
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  • 9
    Online Resource
    Online Resource
    AIP Publishing ; 2013
    In:  Physics of Plasmas Vol. 20, No. 7 ( 2013-07), p. 073509-
    In: Physics of Plasmas, AIP Publishing, Vol. 20, No. 7 ( 2013-07), p. 073509-
    Type of Medium: Online Resource
    ISSN: 1070-664X , 1089-7674
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2013
    detail.hit.zdb_id: 1472746-8
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  • 10
    Online Resource
    Online Resource
    AIP Publishing ; 2012
    In:  Applied Physics Letters Vol. 100, No. 25 ( 2012-06-18)
    In: Applied Physics Letters, AIP Publishing, Vol. 100, No. 25 ( 2012-06-18)
    Abstract: A stable nonthermal laminar atmospheric-pressure plasma source equipped with dielectric-barrier discharge was developed to realize more efficient plasma generation, with the total energy consumption reduced to nearly 25% of the original. Temperature and emission spectra monitoring indicates that this plasma is uniform in the lateral direction of the jet core region. It is also found that this plasma contains not only abundant excited argon atoms but also sufficient excited N2 and OH. This is mainly resulted from the escape of abundant electrons from the exit, due to the sharp decrease of sustaining voltage and the coupling between ions and electrons.
    Type of Medium: Online Resource
    ISSN: 0003-6951 , 1077-3118
    RVK:
    Language: English
    Publisher: AIP Publishing
    Publication Date: 2012
    detail.hit.zdb_id: 211245-0
    detail.hit.zdb_id: 1469436-0
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