Slatted Cathode for Frequency Agility of MILO HPM Source

Abstract

A magnetically insulated line oscillator (MILO) that is a high power microwave (HPM) source. A cross field device with a plurality of azimuthally extending spaced apart slats.

Claims

1. A cross field device comprising: an anode and a cathode; said cathode having a plurality of azimuthally extending spaced apart slats.

2. The cross field device of claim 1 wherein the number of said azimuthally extending spaced apart slats is changeable.

3. The cross field device of claim 1 wherein the width said azimuthally extending spaced apart slats is changeable.

4. The cross field device of claim 1 wherein the number of said azimuthally extending spaced apart slats and the width said azimuthally extending spaced apart slats is changeable.

5. The cross field device of claim 1 wherein one or more of said azimuthally extending spaced apart slats fold inside each other.

6. The cross field device of claim 1 wherein the length of one or more of said azimuthally extending spaced apart slats is changeable.

7. The cross field device of claim 1 wherein the space between one or more of said azimuthally extending spaced apart slats is changeable.

8. The cross field device of claim 1 wherein the frequency content, electrical fields, and pulse lengths of said cross field device can be controlled by moving said slats into and out of a cylinder surface.

9. A cross field device comprising: a cavity having an aperture and changes to said aperture of said cavity change the capacitance of the cavity.

10. The cross field device of claim 9 wherein changes to said aperture of said cavity change both the capacitance of said cavity and the fundamental or resonant frequency of said cavity.

11. The cross field device of claim 9 further including one or more spaced apart vanes located in said cavity wherein changing the dimensions of said one or more of said vanes changes the aperture of said cross field device.

12. The cross field device of claim 9 further including one or more spaced apart vanes located in said cavity wherein changing the width of said one or more of said vanes changes the aperture of said cross field device.

13. The cross field device of claim 9 further including one or more spaced apart vanes located in said cavity wherein changing the number of vanes in said cavity changes the aperture of said cross field device.

14. The cross field device of claim 2 wherein said cross field device is a MILO.

15. The cross field device of claim 2 wherein said cross field device is a Magnetron.

16. The cross field device of claim 2 wherein said cross field device is a Reltron.

17. The cross field device of claim 9 wherein said cross field device is a MILO.

18. The cross field device of claim 9 wherein said cross field device is a Magnetron.

19. The cross field device of claim 9 wherein said cross field device is a Reltron.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0037] In the drawings, which are not necessarily drawn to scale, like numerals may describe substantially similar components throughout the several views. Like numerals having different letter suffixes may represent different instances of substantially similar components. The drawings illustrate generally, by way of example, but not by way of limitation, a detailed description of certain embodiments discussed in the present document.

[0038] FIG. 1 shows a prior art canonical MILO geometry.

[0039] FIG. 2 illustrates Pulse and spectral content produced by canonical MILO.

[0040] FIG. 3 a cut-away representation of the slatted cathode MILO for an embodiment of the present invention.

[0041] FIG. 4A is a side view of the slatted cathodes shown in FIG. 3.

[0042] FIG. 4B shows a partially unfolded slat that may be used with an embodiment of the present invention.

[0043] FIG. 4C shows a folded slat that may be used with an embodiment of the present invention.

[0044] FIG. 4D shows an expandable slat that may be used with an embodiment of the present invention.

[0045] FIG. 4E shows a telescoping slat that may be used with an embodiment of the present invention.

[0046] FIG. 5 shows the electrical output of a slatted cathode. The configuration shows that under the right circumstances, the output of the slated cathode is the same as that as the solid cathode.

[0047] FIG. 6 shows frequency output a slatted cathode geometry and a solid cathode geometry. Notice the shift in frequency as well as the change in spectral content and second harmonic. Additional frequencies are also present near 4 Ghz.

[0048] FIG. 7 shows a MILO having a frequency tunable geometry.

[0049] FIG. 8 is a particle trajectory plot of a frequency adjustable MILO geometry. The plot also shows the time domain pulse. Notice the cavities, in the slow-wave structure, do not have symmetric size.

[0050] FIG. 9 shows the spectral output of 4 different MILO's of the same size using our NOVEL frequency variable control method. The spread is near 400 kHz.

[0051] FIGS. 10A and 10B are a composite showing the time-domain pulse of a standard 2.4 Ghz MILO and one with a smaller aperture and one with a larger aperture.

DETAILED DESCRIPTION OF THE INVENTION

[0052] Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed method, structure, or system. Further, the terms and phrases used herein are not intended to be limiting, but rather to provide an understandable description of the invention.

[0053] In one embodiment, as shown in FIGS. 3 and 4A, the present invention concerns a device 200 having an anode 202, vacuum 204, beam dump 206 and strips or slats 210 which replace the azimuthally continuous cathode. The slats reduce the number of neutrals because LCR circuit and thereby allowing the fundamental frequency of the slats reduce the surface area. By reducing the surface area by a factor of 2, the neutrals are reduced by a factor of 2. If the surface area of the cathode is reduced then the neutrals are reduced by a factor of 5. The teachings of this embodiment may be used a cross-field device, including MILO's, Magnetrons, Reltrons, TWT, etc. The embodiments of the present invention may also be applied to the electronics in microcircuits.

[0054] In other embodiments, as shown in FIGS. 4B and 4C, slatted cathode can be built out of slats 400 and 402 that fold inside each other mechanically exposing empty spaces or slats with larger azimuthal length akin to a window blinds. As shown in FIG. 4D, another way to change the width of a slat is to provide a main slat 410 which includes interior wings 411 and 412 which move in and out of the main slat 410. In yet another embodiment, the azimuthal length of the slat is adjustable by providing telescoping slats 420 and 430. These can be mechanical controlled from a distance via motors that move the slats in and out. Another example would be those street billboards that have multiple images depending on which slats are facing forward. Again these are controlled by motors and computers. In this case depending on the need the frequency content, electrical fields and pulse lengths can be controlled by moving slats into and out of the cylinder surface.

[0055] The embodiments of the present invention will increase the pulse length by reducing the surface area and by reducing the number of desorbed neutrals according to that surface area reduction. The slatted cathode is designed to maintain the electrical performance of a full or standard cathode as shown in FIGS. 5 and 6 but it reduces the number of neutrals produced by the cathode and so the pulse length is increased and the pulse repetition rate is improved. In addition, the number of slats can be chosen for the desired operation.

[0056] In one embodiment, the present invention uses a slatted cathode which transforms the cathode from a solid cylinder-like structure (azimuthally continuous) to one that has slats around the edge of the cylinder structure. The slats are capable of providing the necessary current and also introduce additional frequencies (at other than resonant frequencies) making the MILO a multifrequency device. It also makes the device controllable meaning that it allows not just for multiple frequencies but that these can be called up or generated as desired and with the users' controlsimply by varying the number of slats and the width of the slats.

[0057] Reduction of the surface area may be calculated. For a solid cylinder, the surface area is given by

SA=2*Pi*r*L

[0058] where Pi is the mathematical constant approximated by 3.1416, r is the radius of a cylinder, L is the length of the cylinder.

[0059] Recall that our cathode is cylindrical. For this example, we choose r to be=5 cm and L=20 cm. This gives a surface area for a full cylinder SA=628.32 cm.sup.2.

[0060] For a slatted cathode, the relationship for the surface area of the slatted cathode is

[00001]$SAsc=\frac{\mathrm{Arc}\mathrm{Length}}{360}*\left(2*Pi*r*L\right)*\left(\#\mathrm{of}\mathrm{Slats}\right)$

[0061] Where arc length is the azimuthal extent of the slat for the canonical example of 9 slats each of arc length of 10 degrees with a radius of 5 cm and length of 20 cm each, SAsc=157.08 cm.sup.2.

[0062] The surface area is reduced by 4. Now for the repetition rate improvement. This repetition rate is governed by the following

[00002]$Rep=\frac{\mathrm{Pressure}}{\#\mathrm{neutrals}}*\left(7E19\frac{\mathrm{molecules}}{\mathrm{liter}*\mathrm{torr}}\right)*\mathrm{Pumping}\mathrm{speed}\mathrm{of}\mathrm{vacuum}$

[0063] where #neutrals are the number of molecules desorbed each pulse #neutral is a function of the surface area of a cathode. and if the surface area for a full cathode is 628 cm.sup.2 and each pulse releases about 3.5E15 molecules/cm{circumflex over ()}2/pulse then #neutrals=2.2 E18.

[0064] Pressure=10-6 torr and Pumping speed is 20 liters/sec. This yields a Repetition Rate of 0.000636 Hertz. By reducing the surface area by 4 to ?157 cm this yields Nneutrals=5.5E17 and a repetition rate of 0.00254 Hertzan improvement of 4.

[0065] In yet other embodiments, the cavity remains the same and only the entrance is changed. This changes the capacitance and the resonant frequency. The invention accomplishes the changes by changing the basic circuit of the cross-field device, including MILO's, Magnetrons, Reltrons, TWT, etc. the embodiments of the present invention may also be applied to the electronics in microcircuits.

[0066] In another aspect, the present invention provides a MILO 700 having a frequency tunable geometry as shown in FIG. 7. This embodiment has a modifiable cavity entrance 710 so that the capacitance is changed by altering the entrance or aperture of the cavity. As shown in FIG. 7, one or more spaced apart slow wave blocks or sections 720-723 are adapted to change thickness as desired thereby changing the dimensions of cavities 740-742. In other words, there is an aperture reduction as the thickness of blocks or sections 720-723 increases.

[0067] This frequency adjustability/variability/variability may be command controlled. By this, it is meant that a change of the internal geometry via mechanical means can alter the spectral output of a MILO. FIG. 8 shows a particle trajectory plot, in 2 dimensions, as well as the time domain plot of the pulse. This particular geometry increased the aperture entrance.

[0068] The present invention yields narrowband frequencies just like the canonical device. FIG. 9 shows the FFT of 4 shots, canonical, 2 smaller cavity apertures, and 1 larger aperture. The narrowband spectral content has a controllable spread of approximately 375 kHz which is about 15% of the center frequency.

[0069] This is controlled by the size of the aperture. In a larger MILO such as a 1.6 or 1.3 GHz device, 500 kHz variation is expected. Also, notice that this modification cleans up the narrow band peak. Notice that a 2.4 GHz contains a small side lobe which is reduced with our method

[0070] FIG. 10A shows a composite image of two different shots. One with a slightly shorter pulse and one with a longer pulse than the canonical.

[0071] In other words, the embodiments of the present invention can also control the pulse startup.

[0072] Additionally, the embodiments of the present invention can also increase the peak fields as shown in FIG. 10B.

[0073] The embodiments of the present invention not only can change or tune the frequency of the device but also change the start of the pulse and increase field strength

[0074] It is important to state that this change in aperture size, either smaller or larger, even deeper into the cavity can be accomplished via mechanical means. In this case, sections 720-723 are each insertable and removeable from cavity 710. In a preferred embodiment, sections 720-723 are disks or vanes. In other embodiments, disks or vanes 720, 722 and 723 may be embedded into a main disk or vane 721 or put back into the main disk or vane (akin to a plastic chair piece that hides the hydraulic steel lift, one piece fits into the other one, and when extended it makes the piece longer. This mechanism can be driven by electrical, hydraulic, or mechanical energy.

[0075] While the foregoing written description enables one of ordinary skill to make and use what is considered presently to be the best mode thereof, those of ordinary skill will understand and appreciate the existence of variations, combinations, and equivalents of the specific embodiment, method, and examples herein. The disclosure should therefore not be limited by the above-described embodiments, methods, and examples, but by all embodiments and methods within the scope and spirit of the disclosure.