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  • Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences  (3)
  • Chen Xi-Meng  (3)
  • 2015-2019  (3)
  • 1
    Online Resource
    Online Resource
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2017
    In:  Acta Physica Sinica Vol. 66, No. 12 ( 2017), p. 124101-
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 66, No. 12 ( 2017), p. 124101-
    Abstract: The transmission of 1.5 keV-electrons through a conical glass capillary is reported. This study aims to understand the so-called guiding effect for the negatively charged particles (e.g. electrons). The guiding mechanism is understood quite well with positively charged particles in particular highly charged ions, but not clear with electrons, i.e., even the basic scheme mediated by the existence of negative charge patches to guide the electrons is still somewhat controversial. The study of the charging-up dynamics causing the electrons transport inside the capillary will shed light on this issue. In order to perform this, a data acquisition system has been setup to follow the time evolution of the twodimensional angular distribution of the transmitted electrons. The electrons are detected by the multi-channel plate (MCP) detector with a phosphor screen. The image from the phosphor screen is recorded by a charge-coupled device camera. The timing signals for the detected events are extracted from the back stack of the MCP detector and recorded by the data acquisition system, synchronized with the acquired images. The electron beam has a size of 0.5 mm0.5 mm and a divergence of less than 0.35. The inner diameter of the straight part of the capillary is 1.2 mm and the exit diameter is 225 m. A small conducting aperture of 0.3 mm in diameter is placed at the entrance of the capillary. Two-dimensional angular distribution of the transmitted electrons through conical glass capillary and its time evolution are measured. The results show that the transmission rate decreases and reaches to a constant value for the completely discharged glass capillary with time going by. The centroid of the angular distribution moves to an asymptotic value while the width remains unchanged. These transmission characteristics are different from those indicated in our previous work (2016 Acta Phys. Sin. 65 204103). The difference originates from the different manipulations of the capillary outer surface. A conducting layer is coated on the outer surface of the capillary and grounded in this work. This isolates various discharge/charge channels and forms a new stable discharge channel. The transmission rate as a function of the tilt angle shows that the allowed transmission occurs at the tilt angle limited by the geometrical factors, i.e., the geometrical opening angle given by the aspect ratio as well as the beam divergence. The transmission characteristics suggest that most likely there are formed no negative patches to facilitate the electron transmission through the glass capillary at this selected beam energy. It is different from that of highly charged ions, where the formation of the charge patches prohibits the close collisions between the following ions and guides them out of the capillary.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2017
    Location Call Number Limitation Availability
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  • 2
    Online Resource
    Online Resource
    Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences ; 2018
    In:  Acta Physica Sinica Vol. 67, No. 20 ( 2018), p. 203401-
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 67, No. 20 ( 2018), p. 203401-
    Abstract: The ions with different incident energies transmitting through insulating nanocapillaries are studied in various configurations. For the low energy ions transmitting through nanocapillaries, Stolterfoht et al.[2002 Phys. Rev. Lett. 88 133201] have observed the guiding effect. Subsequent studies revealed that the self-organizing charge patches on the capillary wall inhibit charge exchange and the ions are transmitted along the capillary axis direction. The high energies of ions transmitting through nanocapillaries are measured, the main transmission mechanism is multiple random inelastic collisions below the surface, and the charge patches will not affect the transmitted ions trajectories. The transmission features of the intermediate energy ions are different from those of the low and high energy ions. The ion beams with intermediate energies have many applications, so it is necessary to understand the transmission features of the intermediate energy ions though nanocapillaries. Recent studies have focused on the transmission of the intermediate energies ions through the nanocapillaries. In the present work, we investigate thie transmission features, such as the two-dimensional transmitted angular distributions, the charge states and position distributions, and the evolution of the relative transmission rate and the charge purity of 30 keV H+ transmitting through nanocapillaries in a polycarbonate membrane at the angles of-1 and-2. The experimental data clearly show that the transmitted H+ ions consist of the transmitted scattering H+ ions, which are located around the direction of the incident beam, and the transmitted guiding H+ ions, which are located around the direction of the capillary axis. With the charges depositing in the capillary, the proportion of the transmitted scattering H+ ions increases and the proportion of the transmitted guiding H+ ion decreases, which directly demonstrates the dynamical evolution of the scattering ions and the guiding ions. To understand the competition between the transmitted scattering ions and the transmitted guiding ions and the physical picture of the intermediate energy ions transmitting through the insulating nanocapillaries, the trajectories of the H+ ions in the capillary and the potential distribution and electric field intensity distribution in the capillary are numerically simulated. The results show that the potential distributions and electric field intensitiesy are different for H+ ions transmitting through nanocapillaries at various tilt angles, and the simulation results are in good agreement with the experimental data. The experimental and simulation results give us a further insight into the mechanisms of guiding and scattering in intermediate energy ions transmitting through nanocapillaries.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2018
    Location Call Number Limitation Availability
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  • 3
    In: Acta Physica Sinica, Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences, Vol. 65, No. 20 ( 2016), p. 204103-
    Abstract: It has been found that the transmission rate of the electrons through insulating capillaries as a function of time/incident charge is not the same as that of the ions. The question arises that by using the electrons, if the negative charge patches can be formed to facilitate the transmission of the following electrons, thereby substantiating that the so-called guiding effect works also for electrons. This study aims to observe the time evolutions of the transmission of electrons through a straight glass tube and a tapered glass capillary. This will reveal the details of how and (or) if the negative charge patches can be formed when the electrons transport through them. In this work, a set of MCP/phosphor two-dimensional detection system based on Labview platform is developed to obtain the time evolution of the angular distribution of the transmitted electrons. The pulsed electron beams are obtained to test our detection system. The time evolution of the angular profile of 1.5 keV electrons transmitting through the glass tube/capillary is observed. The transmitted electrons are observed on the detector for a very short time and disappear for a time and then appear again for both the glass tube and tapered glass capillary, leading to an oscillation. The positive charge patches are formed in the insulating glass tube and tapered glass capillary since the secondary electron emission coefficient for the incident energy is larger than 1. It is due to the fact that fast discharge of the deposited charge leads to the increase of the transmission rate, while the fast blocking of the incident electrons due to the deposited positive charge leads to the decrease of the transmission rate. The geometrical configuration of the taper glass capillary tends to make the secondary electrons deposited at the exit part to form the negative patches that facilitate the transmission of electrons. This suggests that if the stable transmission needs to be reached for producing the electron micro-beam by using tapered glass capillaries, the steps must be taken to have the proper grounding and shielding of the glass capillaries and tubes. Our results show a difference in transmission through the insulating capillary between electrons and highly charged ions.
    Type of Medium: Online Resource
    ISSN: 1000-3290 , 1000-3290
    Language: Unknown
    Publisher: Acta Physica Sinica, Chinese Physical Society and Institute of Physics, Chinese Academy of Sciences
    Publication Date: 2016
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
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