Previously measured experimental brightness as a function of the emission current. The Langmuir limit values calculated using the simulated axial cathode current density, are added to the plot as curves of the same type lines but without the symbols.
Example of the electron gun model used in previously performed measurements. The cathode apical radius of curvature Rcc is 60 μm.
The simulated brightness B, emittance E, and the Langmuir limit. Rectangular keys are the value of brightness obtained, the cathode apical radius of curvature is 120 μm and the lens position is 40 mm.
Enlarged trajectories around the minimal beam size position for the beams that are emitted normal to the cathode surface. Lens excitations for (a), (b), (c), and (d) are 1000, 600, 400, and 350 A T, respectively.
An example of a virtual cathode formed around a curved cathode.
An example of a truncated Maxwellian distribution. The solid curve is the truncated Maxwellian distribution.
Imaging concept for the measurements of brightness. Broken lines denote the parallel beam, and solid lines denote Koehler illumination conditions. On the target, there are a Faraday cage with a pico ammeter and a gold-plated Si edge.
Emission current plotted as a function of the wehnelt voltage. The solid curve with symbols denotes the measured emission currents. The broken and the dotted curves are the simulated emission currents for the wehnelt positions of the −0.1 and −0.2 mm, respectively.
Simulated emission current defines the cathode temperature. Emission current of the 164 μA corresponds to the cathode temperature of 1419.3 K.
Simulated emission current that is used to define the cathode temperature. The beam energy is 10 keV, the wehnelt bias is −670 V, and the heating current is 2.4 A, however, the cathode temperature is slowly increasing. Emission currents of 37, 57, and 96 μA result in cathode temperatures of 1400, 1426, and 1459 K, respectively.
The measured and the simulated brightness as well as the Langmuir limit are shown by the solid, broken, and dotted curves, respectively. The beam energy is 10 keV and the wehnelt bias is −670 V.
The measured brightness and the simulated Langmuir limit for Koehler illumination conditions, the beam energy of 5 keV, and cathode temperature of 1805 K. The simulated brightness is also shown as the broken curve.
The measured brightness and the simulated Langmuir limit for Koehler illumination conditions and cathode temperature of 1805 K, where the beam energy is 2 keV. The simulated brightness is also shown as the broken curve.
The measured and the simulated brightness, as well as Langmuir limit, shown as a function of the image position b. The simulated emittance is also plotted as the solid line. The simulated cathode temperature is 1419.3 K and the image position b is 10 m in the parallel beam conditions.
The measured and the simulated brightness/Langmuir limit: B/L. l., as a function of the ratio b/a between the image position and the lens position.
Setup conditions and the measured brightness B.
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