Pincer Mount Cathode

Abstract

A cathode device with an electrical contact junction that operates cooler and has more stable electrical resistance than prior art Provision of. The cathode device includes an emitter tip (16) for generating electrons. It includes an elongated heater (14) having a proximal end and a distal end. The emitter tip can be located at the distal end of the heater. Two spaced-apart legs (15a, 15b) extend away from the heater's distal end and terminate at the proximal end, forming an elongated slot therebetween. Two electrical contacts (20) compressively engage opposite outer surfaces of the two legs at the heater's proximal end to mechanically secure and electrically connect the two legs to their respective electrical contacts at a junction located away from the emitter tip to maintain a lower junction temperature.

Description

[Background technology]

[0001] Related Applications This application claims the benefit of U.S. Provisional Application No. 63 / 425,802, filed November 16, 2022. The entire teachings of the above application are incorporated herein by reference.

[0002] Thermionic cathodes utilizing LaB6 as the electron emitter can contain graphite-based Joule heating elements. Electron emission is directly related to the emitter temperature. Therefore, fluctuations in the heating current and / or thermal grounding to the graphite heater can cause emission fluctuations and degrade cathode performance. All joints between the power source and the graphite heater must be very stable to provide consistent performance. Unstable connections can lead to variations in thermal or electrical resistance, causing emission changes. These instabilities can result from poor electrical contact, or, if the joint is too hot, can cause chemical reactions between the materials and mechanical instabilities. For best performance, electrical joints must be tightly clamped and thermally grounded. The most challenging electrical joints are those directly connected to the ends of the graphite heater, where temperatures can be high. Summary of the Invention

[0003] The present disclosure provides a cathode device with an electrical contact junction that operates at a lower temperature and has a more stable electrical resistance than the prior art. The cathode device may include an emitter element for generating electrons. The cathode device may include an elongated graphite heater having a proximal end and a distal end, and the emitter element may be attached to the distal end of the graphite heater at an emitter mount located at the distal end. The distal end of the graphite heater may be a solid rod extending from the emitter mount, terminating at a proximal end, and bifurcating into two spaced-apart legs that may form an elongated slot therebetween. Two electrical contacts may compressively engage opposite outer surfaces of the two spaced-apart legs at the proximal end of the graphite heater to mechanically secure and electrically connect the two legs of the graphite heater to the respective electrical contacts at a junction located away from the emitter element to keep the junction cooler and simultaneously provide a good thermal ground. The elongated shape of the graphite heater reduces heat conduction from the hottest part of the heater to the electrical junction, which, combined with an efficient thermal ground at the proximal end, allows the junction temperature to remain low even when the emitter is very hot.

[0004] In certain embodiments, the two electrical contacts can be resiliently biased against the legs and toward each other. Each electrical contact can include a metal pin having a proximal portion extending along a longitudinal axis. Each pin can have a distal contact portion bent transversely to the longitudinal axis. Each pin can be rotationally biased about its respective longitudinal axis to bias the distal contact portion of each pin against its respective leg and toward each other. The proximal portion of each pin can extend through the insulating member along its respective longitudinal axis.

[0005] The present disclosure also provides a cathode device including an emitter tip for generating electrons. The cathode device may include an elongated heater having a proximal end and a distal end. The emitter tip may be located at the distal end of the heater. Two spaced-apart legs may extend away from the distal end of the heater and terminate at the proximal end, forming an elongated slot therebetween. Two electrical contacts compressively engage opposite outer surfaces of the two legs at the proximal end of the heater to mechanically secure and electrically connect the two legs to their respective electrical contacts at a junction located away from the emitter tip to maintain a lower junction temperature.

[0006] In certain embodiments, the two electrical contacts can be resiliently biased against the legs and toward each other. Each electrical contact can include a metal pin having a proximal portion extending along a longitudinal axis. Each pin can have a distal contact portion bent transversely to the longitudinal axis. Each pin can be rotationally biased about its respective longitudinal axis to bias its distal contact portion against its respective leg and toward each other. The proximal portion of each pin can extend through the insulating member along its respective longitudinal axis. In one embodiment, the distal contact portion of each pin can be bent perpendicular to the longitudinal axis. In one embodiment, the emitter tip can be an emitter element attached to an elongated graphite heater within an emitter mount at the distal end of the graphite heater. In another embodiment, the emitter tip can be a single-piece heater / emitter formed from an integral piece of refractory metal. In some embodiments, the single-piece heater / emitter can be formed from tungsten or a tungsten alloy. An electrically insulating spacer member may be compressed between the two spaced apart legs of the heater at the proximal end of the heater.

[0007] The present disclosure also provides a method for forming a cathode device, the method including providing an emitter element for generating electrons. An elongated graphite heater having a proximal end and a distal end can be provided. The emitter element can be attached to the graphite heater within an emitter mount located at the distal end. The distal end of the graphite heater can be a solid rod extending from the emitter mount, terminating at a proximal end, and bifurcating into two spaced-apart legs that can form an elongated slot therebetween. Two electrical contacts can compressively engage opposite outer surfaces of the two spaced-apart legs at the proximal end of the graphite heater to mechanically secure and electrically connect the two legs of the graphite heater to the respective electrical contacts at a junction located away from the emitter element to keep the junction cooler and simultaneously provide a good thermal ground.

[0008] In certain embodiments, the two electrical contacts can be resiliently biased against the legs and toward each other. Each electrical contact can include a metal pin having a proximal portion extending along a longitudinal axis. Each pin can have a distal contact portion bent transversely to the longitudinal axis. Each pin can be rotationally biased about its respective longitudinal axis to bias the distal contact portion of each pin against its respective leg and toward each other. The proximal portion of each pin can extend through the insulating member along its respective longitudinal axis.

[0009] The present disclosure also provides a method for forming a cathode device, the method including providing an emitter tip for generating electrons. An elongated heater having a proximal end and a distal end can be provided. The emitter tip can be located at the distal end of the heater. Two spaced-apart legs can extend away from the distal end of the heater and terminate at the proximal end, forming an elongated slot therebetween. Two electrical contacts can compressively engage opposite outer surfaces of the two spaced-apart legs at the proximal end of the heater to mechanically secure and electrically connect the two legs of the heater to their respective electrical contacts at a junction located away from the emitter tip to maintain a lower junction temperature.

[0010] In certain embodiments, the two electrical contacts can be resiliently biased against the legs and toward each other. Each electrical contact can include a metal pin having a proximal portion extending along a longitudinal axis. Each pin can have a distal contact portion bent transversely to the longitudinal axis. Each pin can be rotationally biased about its respective longitudinal axis to bias its distal contact portion against its respective leg and toward each other. The proximal portion of each pin can extend through the insulating member along its respective longitudinal axis. In some embodiments, the distal contact portion of the pin can be bent perpendicular to the longitudinal axis. In some embodiments, the emitter tip can have an emitter element attached to the elongated graphite heater within an emitter mount at the distal end of the graphite heater. In another embodiment, the emitter tip can be a single-piece heater / emitter formed from an integral piece of refractory metal. The single-piece heater / emitter can be formed from tungsten or a tungsten alloy. An electrically insulating spacer member may be compressed between the two spaced apart legs of the heater at the proximal end of the heater.

[0011] This patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0012] The foregoing will become apparent from the following more detailed description of exemplary embodiments, as illustrated in the accompanying drawings, in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the embodiments. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram of an electron emitter with a cathode device. [Figure 2A] FIG. 1 is a perspective view showing a portion of one embodiment of a cathode device according to the present disclosure. [Figure 2B] FIG. 1 is a perspective view showing a portion of one embodiment of a cathode device according to the present disclosure. [Figure 3] FIG. 1 is a perspective view showing a portion of one embodiment of a cathode device according to the present disclosure. [Figure 4] FIG. 1 is a perspective view showing a portion of one embodiment of a cathode device according to the present disclosure. [Figure 5A] FIG. 1 is a side view of one embodiment of a cathode device. [Figure 5B] FIG. 2 is a cross-sectional view of a split rod portion of a graphite heater. [Figure 6A] 5B is a detailed view, i.e., a perspective view, of the cathode device of FIG. 5A. [Figure 6B] FIG. 5B is a detailed view of the cathode device of FIG. 5A, namely a front view. [Figure 6C] FIG. 5B is a detailed view of the cathode device of FIG. 5A, namely a front view. [Figure 6D] FIG. 5B is a detailed or enlarged view of the cathode device of FIG. 5A. [Figure 6E]FIG. 5B is a detailed or enlarged view of the cathode device of FIG. 5A. [Figure 7A] 1 is a comparative graph comparing heater resistance of pincer mount cathodes of the present disclosure with prior art cathodes. [Figure 7B] 1 is a comparative graph comparing heater resistance of pincer mount cathodes of the present disclosure with prior art cathodes. [Figure 8A] FIG. 1 is a detailed view, i.e., a perspective view, of another embodiment of a cathode device. [Figure 8B] FIG. 1 is a detailed view, namely a front view, of another embodiment of a cathode device. [Figure 8C] FIG. 1 is a detailed view, namely a side view, of another embodiment of a cathode device. [Figure 8D] FIG. 2 is a detailed or enlarged view of another embodiment of a cathode device. [Figure 9] FIG. 10 is a side view showing a portion of another embodiment of a cathode device. [Figure 10A] FIG. 10 is a front view of another embodiment of a cathode device. [Figure 10B] FIG. 10 is a side view of another embodiment of a cathode device. [Figure 11A] FIG. 10 is a front view of another embodiment of a cathode device. [Figure 11B] FIG. 10 is a side view of another embodiment of a cathode device. [Figure 11C] FIG. 2 is an enlarged view of another embodiment of a cathode device. [Figure 11D] FIG. 2 is an enlarged view of another embodiment of a cathode device. [Figure 12A] FIG. 10 is a front view of another embodiment of a cathode device. [Figure 12B] FIG. 10 is a side view of another embodiment of a cathode device. [Figure 12C] FIG. 2 is an enlarged view of another embodiment of a cathode device. [Figure 12D] FIG. 2 is an enlarged view of another embodiment of a cathode device. [Figure 12E] FIG. 10 is a perspective view of another embodiment of a cathode device. [Figure 12F] FIG. 10 is an enlarged side view of another embodiment of a cathode device. [Figure 13A] FIG. 10 is a front view of another embodiment of a cathode device. [Figure 13B] FIG. 10 is a side view of another embodiment of a cathode device. [Figure 14] 10 is a graph showing heater resistance versus time for three samples of the same pincer-mount cathode device. [Figure 15A] FIG. 10 is a front view of yet another cathode device according to the present disclosure. [Figure 15B] FIG. 10 is a side view of yet another cathode device according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] A description of exemplary embodiments follows.

[0015] Referring to FIG. 1, an electron emitter or electron gun 10 in this disclosure emits electrons e - 2A-6E, an embodiment of the cathode device 12 includes a pincer-mounted cathode device 12 for generating electrons e, such as LaB6 (lanthanum hexaboride) or CeB6 (cerium hexaboride) crystals, mounted on an intermediate connection or transition portion, i.e., emitter mount 24, located at the distal end of the graphite heater 14. - The emitter mount 24 may include an elongated graphite or carbon heater or heater rod 14 supporting an emitter tip or element, or cathode element 16, for emitting electrons e. The graphite heater 14, emitter mount 24, and emitter element 16 may extend along a central longitudinal emitter axis A. -may be emitted along axis A by emitter element 16. Graphite heater 14 may have an elongated split rod portion 15 extending along axis A, forming two spaced apart elongated legs 15a and 15b on opposite sides of axis A with an elongated space, opening, or slot 18 therebetween, extending from emitter mount 24 away from the distal end of graphite heater 14 and terminating at the proximal end of graphite heater 14. Referring to FIG. 5B , each leg 15a and 15b may have an outwardly facing curved, rounded surface 13 and an inwardly facing flat surface 11. The inwardly facing surfaces 11 of legs 15a and 15b may face each other and form a slot 18 therebetween.

[0016] An electrical connection or connector 22 having two resilient or spring-loaded electrical contacts, contact members, or pins 20 can be coupled, connected, attached, secured, or adhered to an insulating member 26, such as a ceramic disk, by brazing, for example, at a braze joint 30. The two electrical contacts or pins 20 can be metal pins, such as molybdenum, molybdenum-rhenium, or molybdenum alloy pins. The pins 20 can be resiliently compressively engaged with opposite or facing outer surfaces 13 of two spaced-apart legs 15 a and 15 b of the graphite heater 14 for mechanically securing, compressing, or clamping therebetween along a lateral clamping axis C and electrically connecting to the respective legs 15 a and 15 b. Each pin 20 may have an elongated, straight proximal portion 20a extending along a longitudinal axis L and an elongated, straight distal contact portion 20b bent laterally and extending along an angular or transverse axis T that is angled, perpendicular, or orthogonal to the proximal portion 20a and the longitudinal axis L. The two pins 20 may each extend along the longitudinal axis L through a hole 32 in the insulating member 26 for connecting to electrical power. The distal ends of the transverse distal contact portions 20b may extend substantially parallel and adjacent to each other and may be resiliently pried apart or spaced apart to form a slight gap therebetween. The distal contact portions 20b may be spaced slightly above and parallel to the top surface of the insulating member 26. The distal contact portion 20b of each pin 20 may be bent relative to the proximal portion 20a just above the top surface of the insulating member 26. The distal contact portion 20b of each pin 20 may be resilient, biased, or spring loaded laterally or rotationally about their respective longitudinal axes L in the direction of arrows 34 to resiliently compressively engage, compress, clamp, or capture the legs 15a and 15b of the graphite heater 14 between the two distal contact portions 20b with a resilient spring force F. A small, narrow, flat, electrically insulating spacing or spacer member or spacer 36 may be disposed between the two legs 15a and 15b and may be compressed therebetween.The spacers 36 can provide a more secure and stable mechanical and electrical connection between the legs 15a and 15b of the graphite heater 14 and the distal contact portion 20b by limiting the amount or distance the legs 15a and 15b can move or compress toward one another. In some embodiments, the inward-facing surface of each distal contact portion 20b can include a rounded or curved groove or recess 38 extending parallel to and opposite the central axis A to receive the curved outer surface 13 of the respective legs 15a and 15b and help to position, capture, and firmly mechanically secure the legs 15a and 15b of the graphite heater 14 therebetween, while also providing a secure and stable electrical connection therebetween at the electrical junction 28. The diameter and length of the proximal and distal portions 20a and 20b of the pins 20 can be varied to provide each pin with a resilient spring force F or bias ranging from approximately 1 to 3.5 pounds. For a 0.016-inch diameter graphite heater 14, a holding pressure of approximately 4,000 to 13,000 psi can be achieved for secure attachment. Depending on the dimensions of the pins 20, the lateral spring force F (FIG. 6A) of each pin 20 relative to each leg 15a and 15b can include elastic twisting of the pin 20 about its longitudinal axis L, creating a resilient torsional spring force, and / or elastic bending of the distal contact portion 20b relative to the transverse axis T and / or axis L, creating a cantilever spring force. The location at which the legs 15a and 15b of the graphite heater 14 engage the distal contact portion 20b can be a moment arm away from each longitudinal axis L, i.e., the distance between axis L and axis A.

[0017] Anchoring the proximal ends of the legs 15a and 15b of the graphite heater 14 between the two distal contact portions 20b of the pin 20, away from the LaB6 crystal emitter tip 16, reduces heat conduction from the hottest portion of the heater 14 to the electrical junction 28. As seen in FIG. 4 by the direction of arrow 40, current flows either up one leg 15a and across the emitter mount 24 at the distal end of the heater 14, or down the other leg 15b in a direction parallel to and opposite to the current in leg 15a. The bidirectional current partially cancels and reduces the magnetic field at the emitter tip 16. Separating the hot emitter tip 16 from the electrical junction 28, combined with efficient thermal grounding at the electrical junction 28 between the graphite heater 14 and the pin 20, allows the temperature of the electrical junction 28 to remain low, even when the emitter 16 is very hot. The pin 20 can function as a heat sink, thermally connected to a larger heat sink in the insulating member 26 or grounded. The rounded or curved grooves 38 in the distal contact portion 20b can increase the contact area between the legs 15a and 15b of the heater 14, thereby increasing the thermal contact heat sink surface area for better heat sinking capability and increasing the electrical contact surface area to provide a more stable electrical connection. Keeping the electrical connection or joint 28 cooler reduces chemical reactions and mechanical movement of the components, resulting in a more consistent electrical resistance for the pincer-mount cathode device 12 of the present disclosure compared to a standard cathode device of the prior art, as shown in the comparative graphs of FIGS. 7A and 7B. This consistent electrical resistance allows the cathode device 12 and electron emitter 10 of the present disclosure to operate more consistently with less variation in electron emission, thereby providing a consistent electron e - can be provided.

[0018] In some embodiments, the graphite heater 14 can be formed from, but is not limited to, non-pyrolytic graphite. The diameter of the heater rod 14, before splitting, can range from approximately 0.01 to 0.036 inches. The width of the slot 18 can be approximately 0.003 to 0.008 inches. The heater rod 14 need not have a circular cross-section; in some embodiments, it can have a rectangular cross-section. The power supplied to the cathode device 12 can have a source voltage of approximately 2 to 4 volts and a source current of approximately 1 to 4 amperes. The emitter element 16 can have a crystalline tip ranging from a perfect cone point (0 μm flat) to a tip flat of approximately 2 mm, and in some cases, to a tip flat of approximately 3 mm. The operating temperature of the emitter element 16 can range from approximately 1500 to 1900°K. In some embodiments, the pin 20 can have a diameter of approximately 0.039 inches. In one embodiment, the horizontal length of distal pin portion 20b from longitudinal axis L may be approximately 0.143 inches (FIG. 6B), but in other embodiments may range from approximately 0.0625 to 0.25 inches. The exposed height H of legs 15a and 15b of graphite heater 14 between the intermediate transition or connection portion, i.e., the contact point between emitter mount 24 and distal contact portion 20b, is L (FIG. 5A) may be approximately 0.05 to 0.2 inches or greater to provide thermal isolation or spacing of the emitter element 16 and emitter mount 24 from the electrical junction 28 and distal contact portion 20b. Additionally, the height of the tip of the emitter element 16 from the top surface of the insulating member 26 may be approximately 0.256 inches in some embodiments, and approximately 0.2 to 1 inch in other embodiments, to provide thermal isolation or spacing. Referring to FIG. 6E, in the illustrated embodiment, the distance between the transverse axes T when clamping the heater 14 may be approximately 0.048 inches.

[0019] 8A-8D show another embodiment of a cathode device 45 of the present disclosure, in which the distal contact portions 20b of the pins 20 of the cathode device 45 can capture two graphite clamping blocks 42 to secure the legs 15a and 15b of the graphite heater 14 therebetween. The distal contact portions 20b can have inwardly facing flats 44 for engaging the flat outer surfaces of the graphite clamping blocks 42. The inner surfaces of the clamping blocks 42 can have rounded or curved recesses or grooves 38 extending parallel to the axis A to capture the opposing outer surfaces 13 of the legs 15a and 15b of the graphite heater 14, similar to that shown in FIG. 6E.

[0020] 9 shows another embodiment of a cathode device 46 of the present disclosure, in which the distal contact portion 20b is bent at only a slight transverse angle relative to the longitudinal axis L, sandwiching and compressing the legs 15a and 15b of the graphite heater 14 via a graphite block 42 along a common single clamping axis C. The distal contact portion 20b can bend elastically like a cantilever beam. In some embodiments, the graphite block 42 can be omitted, and the legs 15a and 15b of the graphite heater 14 can be compressed, gripped, or held directly between the distal contact portions 20b on opposite sides of the pin 20.

[0021] 10A and 10B show another embodiment of a cathode device 48 that is similar to cathode device 12 but may differ in that the distal contact portion 20b of the cathode device 48 is spaced further away from the insulating member 26. This allows the emitter tip 16 to be spaced above or away from the insulating member 26 by a greater distance. The remaining features may be similar to cathode device 12.

[0022] 11A-11D show another embodiment of a cathode device 50 that is similar to cathode device 48 but may differ in that the lateral or horizontal distal contact portions 20b have shorter lengths, thereby moving the straight proximal portions 20a extending through insulating member 26 closer together, as seen in the front view of FIG. 11A. In the front view, proximal portions 20a are spaced apart a distance slightly greater than the diameter of split rod portions 15 of heater 14, such that heater 14 is clamped such that the outer diameter of split rod 15 approximately matches the outer diameter of the two spaced apart proximal portions 20a. The spring force clamping the heater 14 can include a torsional spring force of the distal contact portions 20b about the longitudinal axis L when the split rod 15 is positioned between the distal contact portions 20b, as shown by the arrows in the side view of Figure 11B, and / or elastic bending of the proximal portions 20a above the insulating member 26 about the longitudinal axis L away from each other. Figures 11C and 11D show an embodiment in which the proximal portions 20a can be spaced slightly further apart and can include emitter elements 16 having crystal planes of about 80 μm and heaters 14 having diameters of about 0.016 inches.

[0023] 12A-12D , cathode device 52 is another embodiment of the present disclosure, similar to cathode device 12, except that distal contact portion 20b can be bent along transverse axis T at a different or smaller angle relative to longitudinal axis L, e.g., 60° rather than 90°, such that distal contact portion 20b is angled upward from proximal portion 20a and away from insulating member 26. This can raise or increase the distance that emitter tip 16 is spaced from insulating member 26. In other embodiments, other angles, e.g., 30° or 45°, or any other suitable angle, can be used to provide the desired distance of emitter tip 16 from insulating member 26. The remaining features can be similar to cathode device 12. The spring force F of each pin 20 can include elastic torsion of pin 20 about longitudinal axis L and / or elastic bending of distal contact portion 20b relative to transverse axis T and / or axis L. 12C and 12D show an embodiment having an emitter element 16 with crystal planes of about 50 μm and a heater 14 with a diameter of about 0.016 inches.

[0024] 12E and 12F show another embodiment of a cathode device 54 that is similar to cathode device 52, but differs in that heater 14 may have a disk-shaped emitter element 16 with a flat top surface having crystal planes of about 2 mm. Heater 14 may have a diameter of about 0.021 inches.

[0025] 13A and 13B show another embodiment of a cathode device 56, which differs from the cathode device 52 in that, after passing through the insulating member 26, the distal contact portions 20b are bent away from each other, each along a first transverse axis T1, e.g., at 60° relative to the corresponding longitudinal axis L, and then bent toward each other, each along a second transverse axis T2, e.g., at 60° relative to the corresponding longitudinal axis L. The distal ends of the distal contact portions 20b can overlap each other to clamp the split rod 15 of the heater 14 therebetween. This allows the emitter tip 16 to be positioned at a greater height or distance from the insulating member 26 than that provided by the cathode device 52. The spring force F exerted by each pin 20 on the split rod 15 may be provided by a torsional spring force about the longitudinal axis L and elastic bending of the distal contact portion 20b about axes T1, T2, and / or L.

[0026] Figure 14 is a graph showing the heater electrical resistance of three samples of the same pincer-mount cathode device operating at 1800°K, which can vary naturally over a small range of approximately 0.01 ohms. The graph shows that the resistance of each sample remains stable over time, but each sample can have a slightly different resistance. For example, pincer-mount cathode device A can have a resistance of approximately 1.634 ohms, pincer-mount cathode device B can have a resistance of approximately 1.645 ohms, and pincer-mount cathode device C can have a resistance of approximately 1.635 ohms.

[0027] 15A and 15B illustrate another embodiment of a cathode device 58 of the present disclosure, which differs from cathode device 12 in that graphite heater 14 may be replaced with a single-piece, integral, elongated heater / emitter 60 formed from a single piece of a refractory metal or metal alloy, such as tungsten or a tungsten alloy, extending along a central emitter axis A. Heater / emitter 60 may have an elongated proximal split rod portion 60a having legs 15a and 15b with a slot 18 therebetween, and a rounded or curved outer surface 13. The distal end of heater / emitter 60 is oriented along axis A to emit electrons e - The emitter tip 60b may be an emitter tip for emitting electrons, which may be tapered into a conical or approximately conical (frustoconical) shape as shown, or may have any other suitable shape, such as a disk shape. An intermediate connecting or transition portion 60c may be disposed between the emitter tip 60b and the split rod portion 60a, such that the emitter tip 60b extends distally from the connecting portion 60c and the legs 15a and 15b extend proximally from the connecting portion 60c. The inner surface 11 may be flat, and an insulating member 36 may be disposed therebetween. The proximal ends of the legs 15a and 15b may be clamped by the distal contact portion 20b of the pin 20. When power is applied to the heater / emitter 60, current flows through the legs 15a and 15b, moves up and down the leg 15b, crosses the connecting portion 60c, and moves down and down the leg 15a, similar to that shown in FIG. 4 . Electrons e - may be formed and emitted from emitter tip 60b along axis A. By forming heater / emitter 60 integrally from the same material, the manufacturing process may be simplified.

[0028] While exemplary embodiments have been specifically shown and described, it will be understood by those skilled in the art that various changes in form and detail can be made therein without departing from the scope of the embodiments encompassed by the appended claims. While specific dimensions have been set forth, it will be understood that the dimensions can be varied depending on the circumstances at hand. Additionally, various features of different disclosed embodiments can be combined together or omitted.

Claims

1. an emitter element for generating electrons; an elongated graphite heater having a proximal end and a distal end, the emitter element being mounted to the graphite heater in an emitter mount at the distal end, and two spaced apart legs extending from the emitter mount and terminating at the proximal end to form an elongated slot therebetween; two electrical contacts compressively engaging opposite outer surfaces of two spaced apart legs at the proximal end of the graphite heater to mechanically secure and electrically connect the two legs of the graphite heater to respective electrical contacts at the junction away from the emitter element to maintain a lower temperature at the junction.

2. 10. The cathode device of claim 1, wherein the two electrical contacts are resiliently biased relative to the legs and toward each other.

3. 3. The cathode device of claim 2, wherein each electrical contact comprises a metal pin having a proximal portion extending along a longitudinal axis, each pin having a distal contact portion bent transversely to said longitudinal axis, each pin being rotationally biased about its respective longitudinal axis to bias the distal contact portion of each pin against its respective leg and toward each other.

4. The cathode device of claim 3 , wherein the proximal portion of each pin extends through the insulating member along a respective longitudinal axis.

5. an emitter tip for generating electrons; an elongated heater having a proximal end and a distal end, the emitter tip being located at the distal end of the heater, and two spaced apart legs extending away from the distal end of the heater and terminating at the proximal end to form an elongated slot therebetween; two electrical contacts compressively engaging opposite outer surfaces of the two spaced legs at the proximal end of the heater to mechanically secure and electrically connect the two legs of the heater to respective electrical contacts at the junction away from the emitter tip to maintain a lower junction temperature.

6. 6. The cathode device of claim 5, wherein the two electrical contacts are resiliently biased relative to the legs and toward each other.

7. 7. The cathode device of claim 6, wherein each electrical contact comprises a metal pin having a proximal portion extending along a longitudinal axis, each pin having a distal contact portion bent transversely to said longitudinal axis, each pin being rotationally biased about its respective longitudinal axis to bias the distal contact portion of each pin against its respective leg and toward each other.

8. The cathode device of claim 7 , wherein the proximal portion of each pin extends through the insulating member along a respective longitudinal axis.

9. The cathode device of claim 7 , wherein the distal contact portion of each pin is bent perpendicular to the longitudinal axis.

10. 6. The cathode device of claim 5, wherein the emitter tip is an emitter element attached to an elongated graphite heater within an emitter mount at the distal end of the graphite heater.

11. 6. The cathode device of claim 5, wherein said emitter tip and said elongated heater are a single-piece heater / emitter formed from an integral piece of refractory metal.

12. 12. The cathode device of claim 11, wherein the single-piece heater / emitter is formed from tungsten or a tungsten alloy.

13. 6. The cathode device of claim 5 further comprising an electrically insulating spacer member compressed between the two spaced apart legs of the heater at the proximal end of the heater.

14. 1. A method of forming a cathode device, comprising: providing an emitter element for generating electrons; providing an elongated graphite heater having a proximal end and a distal end, the emitter element mounted to the graphite heater in an emitter mount at the distal end, and two spaced apart legs extending from the emitter mount and terminating at the proximal end to form an elongated slot therebetween; and compressively engaging opposite outer surfaces of the two spaced apart legs at the proximal end of the graphite heater to mechanically secure and electrically connect the two legs of the graphite heater to respective electrical contacts at the junction located away from the emitter element, so that the two electrical contacts keep the junction cooler.

15. 15. The method of claim 14, further comprising resiliently biasing the two electrical contacts against the legs and toward each other.

16. 16. The method of claim 15, wherein each electrical contact comprises a metal pin having a proximal portion extending along a longitudinal axis, each pin having a distal contact portion bent transversely to the longitudinal axis, the method further comprising rotationally biasing each pin about its respective longitudinal axis to bias the distal contact portion of each pin against its respective leg and toward each other.

17. The method of claim 16, further comprising extending the proximal portion of each pin along its respective longitudinal axis through an insulating member.

18. 1. A method of forming a cathode device, comprising: providing an emitter tip for generating electrons; providing an elongated heater having a proximal end and a distal end, the emitter tip located at the distal end of the heater, and two spaced apart legs extending away from the distal end of the heater and terminating at the proximal end to form an elongated slot therebetween; The two legs of the heater are connected to respective electrical contacts at the junction located away from the emitter tip to keep the junction cooler with two electrical contacts. and compressively engaging opposite outer surfaces of the two spaced apart legs at the proximal end of the heater to mechanically secure and electrically connect the heater to the heater.

19. 20. The method of claim 18, further comprising resiliently biasing the two electrical contacts against the legs and toward each other.

20. 20. The method of claim 19, wherein each electrical contact comprises a metal pin having a proximal portion extending along a longitudinal axis, each pin having a distal contact portion bent transversely to the longitudinal axis, the method further comprising rotationally biasing each pin about its respective longitudinal axis to bias the distal contact portion of each pin against its respective leg and toward each other.

21. 21. The method of claim 20, further comprising extending the proximal portion of each pin along its respective longitudinal axis through an insulating member.

22. 21. The method of claim 20, further comprising providing the distal contact portion of the pin bent at a right angle to the longitudinal axis.

23. 20. The method of claim 18, further comprising providing the emitter tip as an emitter element attached to an elongated graphite heater within an emitter mount at the distal end of the graphite heater.

24. 20. The method of claim 18, further comprising providing the emitter tip and the elongated heater in a single-piece heater / emitter formed from an integral piece of refractory metal.

25. 25. The method of claim 24, further comprising providing a single-piece heater / emitter formed from tungsten or a tungsten alloy.

26. 20. The method of claim 18, further comprising compressing an electrically insulating spacer member at the proximal end of the heater between the two spaced apart legs of the heater.

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