Design of a Low Aspect Ratio Electron Gun for a 220 GHz Sheet Electron Beam EIK

AbstractA converging sheet electron beam with a cross section of 0.05 × 2 mm and current density of 200 A/cm^2, which is formed by an electron gun, is modeled using the synthesis and analysis methods at the condition of magnetic shielding of the cathode. The deformation in the cross section of the beam in the focusing magnetic field is analyzed based on a computer three-dimensional model of an electron optical system with a sheet electron beam. The current-voltage characteristic of an electron gun is studied experimentally in the pulse mode. A collector current of 200 mA is obtained with the beam thickness being 70 μm.

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New type electron gun with electrostatic and electromagnetic lenses

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107459 ◽

1978 ◽

Vol 36 (1) ◽

pp. 62-63

Author(s):

T. Ichinokawa ◽

H. Maeda

Keyword(s):

Electron Microscopy ◽

Electron Beam ◽

Optimum Condition ◽

Bias Voltage ◽

Electron Gun ◽

Charge Effect ◽

Micro Fabrication ◽

Maximum Brightness ◽

New Type ◽

The Ideal

I. IntroductionThermionic electron gun with the Wehnelt grid is popularly used in the electron microscopy and electron beam micro-fabrication. It is well known that this gun could get the ideal brightness caluculated from the Lengumier and Richardson equations under the optimum condition. However, the design and ajustment to the optimum condition is not so easy. The gun has following properties with respect to the Wehnelt bias; (1) The maximum brightness is got only in the optimum bias. (2) In the larger bias than the optimum, the brightness decreases with increasing the bias voltage on account of the space charge effect. (3) In the smaller bias than the optimum, the brightness decreases with bias voltage on account of spreading of the cross over spot due to the aberrations of the electrostatic immersion lens.In the present experiment, a new type electron gun with the electrostatic and electromagnetic lens is designed, and its properties are examined experimentally.

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Energy Distribution in Electron Beams

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100096096 ◽

1972 ◽

Vol 30 ◽

pp. 568-569

Author(s):

Tamotsu Ohno

Keyword(s):

Electron Beam ◽

Energy Distribution ◽

Cross Section ◽

Integral Curve ◽

Electron Beams ◽

Electron Gun ◽

Angular Divergence ◽

Apparent Increase ◽

Integral Width ◽

The Cross

The energy distribution in an electron; beam from an electron gun provided with a biased Wehnelt cylinder was measured by a retarding potential analyser. All the measurements were carried out with a beam of small angular divergence (<3xl0-4 rad) to eliminate the apparent increase of energy width as pointed out by Ichinokawa.The cross section of the beam from a gun with a tungsten hairpin cathode varies as shown in Fig.1a with the bias voltage Vg. The central part of the beam was analysed. An example of the integral curve as well as the energy spectrum is shown in Fig.2. The integral width of the spectrum ΔEi varies with Vg as shown in Fig.1b The width ΔEi is smaller than the Maxwellian width near the cut-off. As |Vg| is decreased, ΔEi increases beyond the Maxwellian width, reaches a maximum and then decreases. Note that the cross section of the beam enlarges with decreasing |Vg|.

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A New High Intensity Grid Cap for RCA-EMU-3 Electron Microscopes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100101323 ◽

1968 ◽

Vol 26 ◽

pp. 316-317

Author(s):

George Christov ◽

Bolivar J. Lloyd

Keyword(s):

Electron Beam ◽

Electron Microscope ◽

High Voltage ◽

High Intensity ◽

Electron Gun ◽

Tungsten Filament ◽

Fluorescent Screen ◽

Electron Microscopes ◽

Pass Through ◽

Ground Potential

A new high intensity grid cap has been designed for the RCA-EMU-3 electron microscope. Various parameters of the new grid cap were investigated to determine its characteristics. The increase in illumination produced provides ease of focusing on the fluorescent screen at magnifications from 1500 to 50,000 times using an accelerating voltage of 50 KV.The EMU-3 type electron gun assembly consists of a V-shaped tungsten filament for a cathode with a thin metal threaded cathode shield and an anode with a central aperture to permit the beam to course the length of the column. The cathode shield is negatively biased at a potential of several hundred volts with respect to the filament. The electron beam is formed by electrons emitted from the tip of the filament which pass through an aperture of 0.1 inch diameter in the cap and then it is accelerated by the negative high voltage through a 0.625 inch diameter aperture in the anode which is at ground potential.

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Point-Cathode Electron Gun Using Electron-Beam Bombardment for Cathode Tip Heating

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179749 ◽

1990 ◽

Vol 48 (1) ◽

pp. 198-199

Author(s):

Ryo Iiyoshi ◽

Susumu Maruse ◽

Hideo Takematsu

Keyword(s):

Electron Beam ◽

Tungsten Wire ◽

Local Heating ◽

Electron Gun ◽

Original Position ◽

Beam Power ◽

Radius Of Curvature ◽

High Brightness ◽

Beam Focusing ◽

Time Operation

Point cathode electron gun with high brightness and long cathode life has been developed. In this gun, a straightened tungsten wire is used as the point cathode, and the tip is locally heated to higher temperatures by electron beam bombardment. The high brightness operation and some findings on the local heating are presented.Gun construction is shown in Fig.l. Small heater assembly (annular electron gun: 5 keV, 1 mA) is set inside the Wehnelt electrode. The heater provides a disk-shaped bombarding electron beam focusing onto the cathode tip. The cathode is the tungsten wire of 0.1 mm in diameter. The tip temperature is raised to the melting point (3,650 K) at the beam power of 5 W, without any serious problem of secondary electrons for the gun operation. Figure 2 shows the cathode after a long time operation at high temperatures, or high brightnesses. Evaporation occurs at the tip, and the tip part retains a conical shape. The cathode can be used for a long period of time. The tip apex keeps the radius of curvature of 0.4 μm at 3,000 K and 0.3 μm at 3,200 K. The gun provides the stable beam up to the brightness of 6.4×106 A/cm2sr (3,150 K) at the accelerating voltage of 50 kV. At 3.4×l06 A/cm2sr (3,040 K), the tip recedes at a slow rate (26 μm/h), so that the effect can be offset by adjusting the Wehnelt bias voltage. The tip temperature is decreased as the tip moves out from the original position, but it can be kept at constant by increasing the bombarding beam power. This way of operation is possible for 10 h. A stepwise movement of the cathode is enough for the subsequent operation. Higher brightness operations with the rapid receding rates of the tip may be improved by a continuous movement of the wire cathode during the operations. Figure 3 shows the relation between the beam brightness, the tip receding rate by evaporation (αis the half-angle of the tip cone), and the cathode life per unit length, as a function of the cathode temperature. The working life of the point cathode is greatly improved by the local heating.

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