Emissivity of a multibeam electron gun with a glassy carbon field-emission cathode

2016 ◽  
Vol 61 (2) ◽  
pp. 290-295 ◽  
Author(s):  
N. A. Bushuev ◽  
O. E. Glukhova ◽  
Yu. A. Grigor’ev ◽  
D. V. Ivanov ◽  
A. S. Kolesnikova ◽  
...  
Author(s):  
K.C.A. Smith ◽  
A.D.G. Cumming

To improve the performance of the field emission electron gun requires that greater total currents are drawn from the field emission cathode. This involves various practical difficulties associated with the vacuum environment, and in addition, the Boersch effect energy broadening may become important at high currents and for certain applications, for example in pulsed transmission microscopy (Smith and Cleaver, 1976). As part of a study of field emission guns under high current conditions we have measured the energy spreads in a pulsed triode gun system. Positive going pulses on the control electrode, or Wehnelt, were used to draw peak currents of up to 2 mA for 10 μS durations, the pulses being of 4 kV amplitude. A (111) orientated single crystal tungsten cathode was used, of 150 mm tip radius, and the energy of the emitted electrons measured in an analyser due to Brack (1962). This consists of a three electrode einzel lens with a superimposed axial magnetic field, and is designed to have a high coefficient of chromatic aberration.


Author(s):  
A. S. Baturin ◽  
I. N. Yeskin ◽  
A. I. Trufanov ◽  
N. N. Chadaev ◽  
E. P. Sheshin ◽  
...  

Author(s):  
A. N. Broers

A field emission cathode electron gun with two stages of acceleration has been built in order to measure the electron beam brightness that can be produced in practice from a tungsten field emission cathode. The gun is similar to that reported by A. Crewe except that the accelerating electrodes are plane, rather than shaped, apertures, and the cathode is located by a gimbal mechanism which allows the cathode to be tilted over an arc of 70° in any direction and positioned laterally. The gun electrodes have been precisely machined with the apertures round within 0.25 micron and aligned with respect to each other to better than 10 micron. The second accelerating electrode is followed by scan plates, a test grid, and an electron detector which together allow the probe size to be measured in the usual scanning electron microscope mode.


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