Figure i. All devices are fixed on a stainless steel positioning plate, and the whole is placed in an ultra-high vacuum target chamber. The target chamber vacuum is better than 1.0X10Pa. The electron beam generated by the LaB6 electron gun is collimated by a two-stage diaphragm, and the diaphragm aperture is 1.0 mm, 0.5mm, the diaphragms are 10mm apart, and each diaphragm is connected to a sensitive ammeter. The capillary is wrapped with aluminum foil to prevent its outer surface from charging. A deflection plate is placed at the exit of the capillary. A 1-dimensional position sensitive detector (PSFC) 131 is behind the deflection plate. The distance between the capillary exit and the detector is 50 mm. The acquisition card is collected and read by the data acquisition software. 2 Results and Discussion Before measuring the angular distribution of the emitted electrons, it is necessary to wait until the output of the emitted electrons reaches a stable level before the measurement results are credible. In the case of workers 1 letter Stolterfoht team - Author: Yu Yang was (1976), male, atomic physics accelerator-based doctor, associate professor in; 1.yumlpcas put. cn.h Qiu: "WWW. Typical angular distribution of exit electrons. The relationship between output electron yield and time. The intensity of the ion beam used is in the order of nA. It takes about 10 minutes from the opening of the beam until the detector receives a stable signal. It means that it takes a certain time to form a "guided electric field" on the inner wall of the capillary. In this work, due to the high electron beam current, after the beam is turned on, a large amount of charge can be quickly deposited on the inner surface of the capillary to form a guided electric field, so almost at the same time when the beam is turned on, A stable signal is received on the detector, which is the typical angle distribution spectrum of the outgoing electrons measured by a position-sensitive detector. The incident electron beam energy is 1000eV and the current intensity is 5. The energy is 1000eV and the current intensity is 5. 15PA. ， The absolute output of the emitted electron changes with time. Within 10min, the impact of the electric incident energy on the electron transmission efficiency is about 30.2nA, and the output fluctuation is less than 10%. It should be noted that the 1-dimensional position is used. Sensitive detectors cannot directly obtain the absolute yield of electrons. The calculation of the absolute yield through the given 1-dimensional angular distribution integral requires the addition of assumptions. For example, the angular distribution completely conforms to the Gaussian distribution, etc. Error. To avoid this, we did not use the position of the Faraday cup resolved total current emitted directly measured, when the angular distribution of electronic information can not be obtained, but it can accurately obtain the absolute yield of emitted electrons. The transmission efficiency of the beam in the capillary is an important characteristic of guiding ability. The transmission efficiency is defined as: = / o // i, where is the incident current and /. Is the absolute output of the emitted electrons. After normalizing the incident current, we calculated the transmission efficiency of the electron beam with energy in the range of 200 ~ 1200eV as shown. The experiment found that as the incident energy increases, the electron transmission efficiency decreases. 3 Schematic diagram of the guiding effect of the theoretical model According to the guiding effect model. Among them: qf is the charge state of the outgoing particles, for electrons -1; Ep is the kinetic energy of incident electrons; Ug is the guiding potential formed by the deposited charge on the inner wall of the capillary, which is related to the incident flow intensity. It is saturated, so Ug can be considered as a constant; in the experiment of the interaction between charged particles and microporous membrane, it is defined as the angle between the incident particle and the capillary axis, that is, the angle of incidence. In the conical tube experiment, the electron beam is incident coaxially , Defined as the capillary cone angle. According to the output particle yield relationship given by the guidance effect model, the transmission efficiency measured by the experiment is fitted. Since q, Ug, are all regarded as constants, after the incident current is normalized, the transmission efficiency n is only related to exp ( ―Ep) Correlation, a negative exponential relationship. It can be seen that the experimental results are in good agreement with the fitting curve based on the guidance effect model. 4. Conclusion The electron-guiding effect was observed when a high-current and intense electron beam was incident on a single tapered SiO2 capillary. Due to the large electron beam intensity in the experiment, the inner wall of the capillary can quickly form a guided electric field, and the electrons are guided out of the capillary stably in mmin. The one-dimensional angular distribution of the emitted electrons was measured using a position-sensitive Faraday tube. By measuring the absolute yield of the emitted electrons, the effect of incident energy on the electron transmission efficiency was studied. The experiment found that the higher the incident energy, the lower the electron emission efficiency, and the transmission efficiency and the incident energy have a negative exponential relationship. The experimental results are in good agreement with the guidance effect model.
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DM-610(6+1 pockets)
DM-910(9+1 pockets)
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