Abstract:
There is disclosed a method of controlling an electron gun without causing decreases in brightness of the electron beam if a current-limiting aperture cannot be used. The electron gun (10) has a cathode (11), a Wehnelt electrode (12), a control electrode (13), an anode (14), and a controller (22). The Wehnelt electrode (12) has a first opening in which the tip of the cathode is inserted, and focuses thermal electrons emitted from the tip of the cathode (11). The thermal electrons emitted from the tip of the cathode (11) are caused to pass into a second opening by the control electrode (13). The anode (14) accelerates the thermal electrons emitted from the cathode (11) such that the thermal electrons passed through the second opening pass through a third opening and impinge as an electron beam (B1) on a powdered sample (8). The controller (22) sets the bias voltage and the control voltage based on combination conditions of the bias voltage and control voltage to maintain the brightness of the beam constant.
Abstract:
An electron source includes a first electrode, a second electrode, a thermionic element interposed between and electrically isolated from the first electrode and the second electrode, and a guard electrode interposed between and electrically isolated from the first electrode and the second electrode. The thermionic element and the guard electrode may be at substantially the same voltage. Another electron source includes a first electrode, a second electrode, a thermionic element interposed between and electrically isolated from the first electrode and the second electrode, and a thermal expansion component interposed between and electrically isolated from the first electrode and the second electrode. The thermal expansion component may be heated to cause expansion. The heating may be cycled to cause alternating expansion and contraction.
Abstract:
La présente invention concerne un générateur de faisceau d'électrons (14) pouvant fonctionner en impulsions ou en continu, le faisceau d'électrons étant émis dan un canon à électrons principal (2) comportant une cathode (11) émettrice et une anode (15). On associe à ce canon à électrons principal (2) un canon à électrons auxiliaire (1) comportant une cathode (3) une grille (6) destinée à moduler en impulsions un faisceau d'électrons auxiliaire (17) lorsque l'on fonctionne en impulsions ou à ajuster le courant du faisceau d'électrons auxiliaire (17) lorsque l'on fonctionne en continu et une anode (5). L'anode (5) est en contact thermique et électrique avec la cathode (11) du canon à électrons principal (2). Le faisceau d'électrons auxiliaire (17) commande l'émission de la cathode (11). Le faisceau d'électrons émis par le canon à électrons principal (2) n'est pas perturbé par la traversée de la grille (6). Application notamment aux tubes hyperfréquences à interaction longitudinale fonctionnant à puissances moyenne et/ou crête élevées.
Abstract:
A disk-shaped cathode pellet is installed and secured by a retainer onto a heater cap that incorporates a heater. The part of this retainer that covers the periphery of the electron emission surface of the cathode pellet functions as a portion of a Wehnelt electrode. Alternatively, the retainer is formed such that the average angle of the surface with respect to the outermost shell of the electron beam matches the Pierce angle such that the part of this retainer that covers the periphery of the electron emission surface of the cathode pellet functions as a Wehnelt electrode.