System and method for increasing operational lifetime of a field emission vacuum tube

Abstract

Systems and methods extending operational lifetime of field emission array vacuum tubes. A getter within the vacuum tube is selectively activated based on operational state trigger conditions like gate current, time intervals, or electron pulse counts. Getters may be activated through conductive or inductive heating. The method involves providing a vacuum tube, FEA construct, and getter; evacuating and sealing the tube; and getter activation based on predetermined trigger conditions. This approach efficiently manages vacuum quality, prolonging tube life.

Description

[0001] SYSTEM AND METHOD FOR INCREASING OPERATIONAL LIFETIME OF A FIELD EMISSION VACUUM TUBE

[0002] FIELD OF THE INVENTION

[0003] The disclosure herein relates to systems and methods for increasing operational lifetime of a field emission array vacuum tube. In particular, the disclosure relates to the use of getters to slow the deterioration of a vacuum within a vacuum tube over time.

[0004] Field Emission Array (FEA) sources such as a Spindt type, CNT type, or the like any other type are electron emitters that may be used in vacuum tubes for example for X-ray tubes or Field Emission visual displays. FE Arrays typically produce a high emission current at first but the emission current degrades rapidly and settling at a lower relatively stable emission current.

[0005] This degradation is due to residual gas within the vacuum tube interacting with the emitter for example gas adsorption on the emitter surface, surface oxidation, ion sputtering, or ion implantation. Such degradation may be reduced by maintaining the array at a higher vacuum.

[0006] Accordingly, the useful lifetime of X-ray tubes is limited by the constant deterioration of the vacuum while the tube is activated. Getters such as Non-Evaporable Getters (NEG or NEG-pumps) may be used to improve the vacuum during the production of vacuum tubes by introducing a reactive material that is which combines with residual gas molecules. Thus by activating a getter during manufacture of the tube, residual gas may be removed from the evacuated space.

[0007] However it has been found that, even when a getter is used during manufacture of FEA vacuum tubes, the vacuum steadily deteriorates after manufacture due to the relatively small volume of the tube as well as the electron bombardment of the anode which releases gaseous particles into the vacuum during operation.

[0008] The need remains, therefore, for maintaining vacuum in FEA vacuum tubes. The invention described herein addresses the above-described needs.

[0009] SUMMARY OF THE INVENTION

[0010] Aspects of the present invention provide systems and methods for extending the operational lifetime of a field emission array (FEA) vacuum tube. The system may incorporate a getter unit within the vacuum tube and may selectively activate the getter based on a trigger condition related to the operational state, thereby contributing to the maintenance of vacuum quality and prolonging tube life. A key aspect of the invention may be the use of a controller that is configured to automate getter activation based on various operational parameters.

[0011] The system comprises a vacuum tube, an FEA construct positioned within the vacuum tube (the FEA construct including a cathode, a plurality of field emission type electron sources, and a gate electrode), a getter unit positioned inside the vacuum tube, and a controller. The controller can be configured to selectively activate the getter unit based on a trigger condition. This trigger condition may be derived from: (1) a gate current signal, (2) a predetermined time interval, or (3) a count of electron pulses. The system may feature conductive activation, inductive activation or both.

[0012] The system may also include a gate current monitor connected between the gate electrode and the cathode, wherein the controller may be configured to receive a gate current signal from the gate current monitor, and wherein the trigger condition may be based on this gate current signal. In such embodiments, the controller may be configured to activate the getter unit when the gate current exceeds a predetermined threshold value or when a second derivative of the gate current is increasing, either of which may be indicative of vacuum deterioration.

[0013] In alternative embodiments, the trigger condition may be based on a predetermined time interval, such that the getter is activated periodically according to a schedule. In another embodiment, the system may include a counter that tracks the number of electron pulses emitted by the FEA construct. The controller can then activate the getter unit after a predetermined number of pulses have been emitted.

[0014] The getter unit itself may comprise a Non-Evaporable Getter (NEG) material, such as a St122 type composition of 70% Titanium and 30% St707. The controller may activate the getter unit by conductively heating the getter unit, for example, by passing a current of at least 3A through activation pins connected to the getter unit. The conductive heating may raise the getter unit's temperature to approximately 500 degrees Celsius.

[0015] The field emission type electron sources within the FEA construct can be implemented using various technologies, including Spindt type electron sources, carbon nanotubes (CNTs), metal-insulator-metal (MIM) type electron sources, or metal-insulator-semiconductor (MIS) type electron sources.

[0016] The system may feature conductive activation, inductive activation or both. In such embodiments, the system may further comprising activation pins for conductive activation and a frequency selector for inductive activation.

[0017] The invention also encompasses a method of manufacturing the FEA vacuum tube. The method includes providing a vacuum tube, introducing the FEA construct and getter unit into the tube, evacuating gas from the tube, activating the getter unit to remove residual gas, sealing the vacuum tube, and then activating the getter unit again.

[0018] The invention further encompasses a method of operating the FEA vacuum tube. The method includes operating the FEA construct and assessing if getter activation is due, and activating the getter unit if activation is deemed necessary. This assessment can be performed using the various triggering mechanisms described above (gate current monitoring, time intervals, or electron pulse counts).

[0019] Specifically, the method of operating the FEA vacuum tube can be carried out by: providing a clock; scheduling getter activation based upon the clock; setting the clock to zero; checking the clock to determine if getter activation is due, wherein assessing if getter activation is due comprises comparing the clock to the getter activation schedule.

[0020] The method of operating the FEA vacuum tube can be carried out by: providing a controller; setting a trigger count (TC); setting an operation count (OC) to zero; incrementing the operation count (OC) as the FEA construct is operated, wherein assessing if getter activation is due comprises comparing the operation count (OC) to the trigger count (TC).

[0021] The method of operating the FEA vacuum tube can be carried out by: providing a gate current monitor; monitoring a gate current; storing the gate current; and analyzing the gate current to detect vacuum deterioration, wherein assessing if getter activation is due comprises determining if vacuum deterioration is detected based on the analyzed gate current.

[0022] The method for increasing the operational lifetime of a field emission array (FEA) vacuum tube, the method comprising: providing a vacuum tube; providing an FEA construct within the vacuum tube, the FEA construct including a cathode, a plurality of field emission type electron sources, and a gate electrode; positioning a getter unit inside the vacuum tube; operating the FEA construct; and activating the getter unit based on a trigger condition related to the operational state of the vacuum tube. The getter can be activated by conductive activation or inductive activation.

[0023] This approach provides a flexible and adaptable system and method for extending the lifetime of FEA vacuum tubes by efficiently managing vacuum quality.

[0024] BRIEF DESCRIPTION OF THE FIGURES

[0025] For a better understanding of the embodiments and to show how it may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings.

[0026] With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of selected embodiments only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects. In this regard, no attempt is made to show structural details in more detail than is necessary for a fundamental understanding; the description taken with the drawings making apparent to those skilled in the art how the various selected embodiments may be put into practice. In the accompanying drawings:

[0027] Fig. 1 is a block diagram indicating selected elements of a system for increasing operational lifetime of a field emission vacuum tube;

[0028] Fig. 2 is a schematic representation of a possible field emission array;

[0029] Fig. 3A is a schematic representation of a vacuum tube incorporating a conductively activated getter according to a first embodiment of the system;

[0030] Fig. 3B is a schematic representation of a vacuum tube incorporating an inductively activated getter according to another embodiment of the system;

[0031] Fig. 3C is a schematic representation of a vacuum tube incorporating a getter bank according to another embodiment of the system;

[0032] Fig. 3D is a schematic representation of a vacuum tube incorporating an inductive getter bank according to another embodiment of the system;

[0033] Fig. 4 schematically represents a flange unit for use in embodiments of the system for increasing operational lifetime of a field emission vacuum tube;

[0034] Fig. 5 is a flowchart of a method for preparing an embodiment of a prolonged lifetime field emission vacuum tube;

[0035] Fig. 6A is a flowchart of a general method for operating a prolonged lifetime field emission vacuum tube;

[0036] Fig. 6B is a flowchart of a time triggered method for operating a prolonged lifetime field emission vacuum tube;

[0037] Fig. 6C is a flowchart of a count triggered method for operating a prolonged lifetime field emission vacuum tube; Fig. 6D is a flowchart of a gate current triggered method for operating a prolonged lifetime field emission vacuum tube; and

[0038] Figs. 7A-C show various graphs showing how the gate current changes over time in FEA tubes indicating deterioration of the tube vacuum.

[0039] DETAILED DESCRIPTION OF THE EMBODIMENT

[0040] Aspects of the present disclosure relate to systems and methods for increasing operational lifetime of a field emission array (FEA) vacuum tube. In particular, the disclosure relates to the use of getters to slow the deterioration of a vacuum within a vacuum tube over time.

[0041] Maintenance of the vacuum in FEA vacuum tubes is particularly difficult because of their small volume. X-ray vacuum tubes are further hampered by the generation of gaseous particles by electron bombardment of the anode target during operation. Thus the vacuum continues to deteriorate even when a getter is used to improve the initial vacuum during manufacture of FEA.

[0042] It has been found that the lifetime of FEA vacuum tube may be increased by introducing a getter into the vacuum tube and activating the getter repeatedly at particular intervals throughout the lifetime of the tube. Various methods for triggering getter activation are described herein such at regular intervals of time and after a certain number of uses.

[0043] According to a particular embodiment, the gate current of the FEA may be monitored as it has been surprisingly found that the gate current of the FEA provides an early indication of vacuum deterioration. Such early indications may be used to trigger getter activation.

[0044] As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely examples of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. 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.

[0045] As appropriate, in various embodiments of the disclosure, one or more tasks as described herein may be performed by a data processor, such as a computing platform or distributed computing system for executing a plurality of instructions. Optionally, the data processor includes or accesses a volatile memory for storing instructions, data or the like. Additionally or alternatively, the data processor may access a non-volatile storage, for example, a magnetic hard disk, flash-drive, removable media or the like, for storing instructions and / or data.

[0046] It is particularly noted that the systems and methods of the disclosure herein may not be limited in its application to the details of construction and the arrangement of the components or methods set forth in the description or illustrated in the drawings and examples. The systems and methods of the disclosure may be capable of other embodiments, or of being practiced and carried out in various ways and technologies.

[0047] Alternative methods and materials similar or equivalent to those described herein may be used in the practice or testing of embodiments of the disclosure. Nevertheless, particular methods and materials described herein for illustrative purposes only. The materials, methods, and examples not intended to be necessarily limiting. Accordingly, various embodiments may omit, substitute, or add various procedures or components as appropriate. For instance, the methods may be performed in an order different from described, and that various steps may be added, omitted or combined. In addition, aspects and components described with respect to certain embodiments may be combined in various other embodiments.

[0048] Reference is now made to the block diagram of Fig. 1 which shows selected elements of a system 100 for increasing operational lifetime of a field emission vacuum tube 120. The system 100 includes a vacuum tube 120, incorporating a field emission construct 140 and a getter unit 160, and a controller 180.

[0049] The getter typically comprises a reactive material which may be activated to combine with residual gas molecules within the vacuum tube thereby improving the vacuum tube. A getter activator 162 may be provided to activate the getter as required for example by raising its temperature above an activation threshold.

[0050] Where required the getter may be a Non-Evaporable Getter pump (NEG) such as an St122 type composition of 70% Titanium and 30% St707 which may be activated by an operating temperature of 500 Celsius. Other getters may be used as required.

[0051] The controller 180 may be configured to trigger the getter activator 162 to activate the getter unit 160 at required intervals throughout the lifetime of the tube 120. The required intervals may be at regular time intervals according to a predetermined required rate, additionally or alternatively, the required intervals may depend upon the usage of the tube, for example the getter unit 160 may be activated after a certain number of electron pulses have been generated. Accordingly, the controller 180 may be activated by various trigger conditions as suit requirements. For example the controller may be connected to triggering units such as a clock 182, a counter 184, a gate current monitor 186, a memory unit 188 or the like as well as combinations thereof as appropriate.

[0052] It is noted that the field emission construct 140 comprises a cathode 142, a field emission array, and a gate electrode 144. A gate current monitor 186 may be connected between the gate electrode 144 and the cathode 142 and configured to provide a gate current signal GS. The controller may be configured to receive the gate current signal when the field emission construct is operated.

[0053] Referring now to Fig, 2, which schematically represents a possible electron emitting construct for use in embodiments of the switchable x-ray source. A field emission type electron source may be electrically connected to a driving circuit via a signal line and further electrically connected to a gate electrode 224. The coordinated electrical activation of the driving circuit and the gate electrode 224 connected to a field emission type electron source 222 results in its activation, i.e. , electron emission. The field emission type electron source 222 performs the electron emission 230 by an electric field formed between the field emission type electron source 222 and the gate electrode 224.

[0054] The field emission type electron source 222 may be, e.g., a Spindt type electron source, a carbon nanotube (CNT) type electron source, a metal-insulator-metal (MIM) type electron source or a metal-insulator- semiconductor (MIS) type electron source. In a preferred embodiment, the electron source 222 may be a Spindt type electron source.

[0055] The activation signal AS may comprise a series of gate pulses GP generated. Accordingly, the electron emission 230 may follow a similar regular pattern of emission.

[0056] With reference to Fig. 3A which is a schematic representation of a vacuum tube 320A incorporating an FEA 340A and a conductively activated getter 360A according to a first embodiment of the system. A pair of FEA control pins 341 A, 343A protrude from the vacuum tube which provide conductive connection to the gate electrode and the cathode electrode. The control pins 341 A, 343A may be used to activate electron emission by providing a gate voltage. It is further noted that the FEA control pins 341A, 343A may be used to monitor the gate current during electron emission.

[0057] A pair of getter activation pins 361A, 362A protrude from the vacuum tube 320A which provide conductive connection to the getter 360A accordingly, a current may be passed through the getter 360A thereby raising its temperature above its activation temperature in order to activate the getter 360A. Accordingly, the getter activation pins 361A, 362A may be selected such that they are capable of sustaining a current of, say, three amperes or so in order to activate the getter when required.

[0058] With reference to Fig. 3B which is a schematic representation of a vacuum tube 320B incorporating the FEA 340B and an inductively activated getter 360B according to another embodiment of the system.

[0059] The inductively activated getter 360B is contained within the vacuum tube 320B in connected between the terminals of a secondary inductive coil 364B operable to generate a current through the getter 360B when inductively coupled with a corresponding primary inductive coil 362B outside the vacuum tube 320. By providing a varying primary potential across the primary coil 362B, a varying secondary potential is induced in the secondary coil 364B thereby generating a current through the getter unit 360B connected thereacross.

[0060] It is noted that a getter may eventually reach saturation after repeated activations. Accordingly, as represented in Fig. 3C, multiple getters may be incorporated in a getter bank 360C in order to multiply the capacity and delay saturation of the getter unit thereby prolonging the operation lifetime of the FEA vacuum tube 320C. It is noted that, although Fig. 3C shows an array of getters 360C connected in parallel to common getter activation pins 361 C, 363C, alternative arrangements may be provided as required. For example, multiple getters may be connected to common getter activation pins in series or each one of the individual getters may be connected to its own individual activation pins allowing each getter to be activated individually.

[0061] An alternative, multiple getter system 360D is illustrated in Fig. 3D in which each one of the individual getter units may be connected to its own individual inductive circuit including a secondary induction coil 364D. It has been found that individual getter activation may be enabled by selecting secondary inductive circuits 364D having characteristic resonant frequencies and providing a primary induction coil 362D connected to a frequency selector 365D. Accordingly, the frequency of the primary induction coil 362D may be selected such that it resonates with the required secondary induction coil 364D and activates the required getter unit 360D.

[0062] Referring now to Fig. 4, which schematically represents a possible flange unit for use in embodiments of the system, The flange may include a FEA unit and a getter unit for incorporation within the vacuum tube. The flange further provides a set of control pins including a gate pin, a ground pin, a focus pin and a pair of filament pins.

[0063] The gate pin and the ground pin may serve as the pair of FEA control pins. Accordingly, the gate pin may be connected to the gate electrode and the ground pin may be connected to the cathode electrode. The focus pin may be used to control a focusing electrode. The filament pins may serve as getter activation pins.

[0064] Reference is now made to the flowchart of Fig. 5 showing a method 500 for preparing a prolonged lifetime vacuum tube for use with field emission arrays. The method includes providing an open vacuum tube 502, introducing into the tube a field emission array (FEA) into the vacuum tube 504 and introducing into the tube a getter unit into the vacuum tube 506. Gas is evacuated from the vacuum tube 508, for example by attaching a vacuum pump. The getter unit is activated 510 for a first time to remove residual gas molecules before the vacuum tube is sealed. The vacuum tube is sealed 512, for example by pinching the glass closed. Following the sealing of the vacuum tube the getter unit is activated for a second time 514.

[0065] For example, it has been surprisingly found that activating a St122 type NEG getter with a constant current of 10 watts at 3 amps for 2-3 minutes significantly extends the lifetime of the FEA vacuum tube.

[0066] Referring now to the flowchart of Fig. 6A showing a method 600 for operating an embodiment of the FEA vacuum tube throughout its lifetime.

[0067] Even when a getter is used during manufacture of FEA vacuum tubes, the vacuum steadily deteriorates after manufacture due to the relatively small volume of the tube as well as the electron bombardment of the anode which releases gaseous particles into the vacuum during operation. In order to overcome this problem, the getter (NEG) for the FEA vacuum tube is activated repeatedly throughout the lifetime of the FEA vacuum tube.

[0068] The method 600 may include providing a getter enabled FEA vacuum tube 602, operating the FEA 604, the controller may assess if the activation is due 606. If it is due then the getter is activated 608 and if not the FEA may be operated again and reassessed until getter activation is due.

[0069] Various indications may be recorded that trigger activation of the getter unit. For example embodies are described herein of time triggered activation, count triggered activation, gate-current triggered activation, second differential triggered activation and the like either individually or in combination.

[0070] Additionally or alternatively, still other methods may be used such as anode current triggered activation. The product (lAnode*Timesec) of the anode knode current and the time Timesec that the FEA has been operated which indicates the total charge transferred and therefore the number of electrons emitted by the FEA source.

[0071] The flowchart of Fig. 6B shows a time triggered method 600B for operating a getter enabled FEA vacuum tube. The count triggered method includes providing an FEA construct and a getter unit in a vacuum tube 602B, providing a clock 604B, setting a getter activation schedule 606B, setting the clock to zero 608B, operating the FEA construct 610B and checking the clock 612B. If the getter activation is due then activating the getter unit 614B if not then the FEA may be operated again until getter activation is due.

[0072] The flowchart of Fig. 6C shows a count triggered method 600C for operating a getter enabled FEA vacuum tube. The time triggered method includes providing an FEA construct and a getter unit in a vacuum tube 602C, providing a counter 604C, setting a trigger count (TC) 606C, for example say a thousand pulses, setting an operation count (OC) to zero pulses 608C, operating the FEA construct 610C, incrementing the operation count 612C and comparing the counter with the trigger count 614C. If the operation count (OC) is greater than the trigger count (TC) then activating the getter unit 616C if not then the FEA may be operated again until the operation count (OC) is greater than the trigger count (TC).

[0073] It is particularly noted that where a gate current monitor is available, the activation of the controller may trigger activation of the getter according to the monitored gate current, where the monitored gate current indicates that the vacuum has deteriorated. The flowchart of Fig. 6D shows a gate current triggered method 600D for operating getter enabled FEA vacuum tube.

[0074] The method includes providing a vacuum tube 602D, providing a field emission array construct 604D, providing a getter unit 606D, providing a gate current monitor 608D and providing a controller 610D. The field emission construct includes a cathode, a plurality of field emission type electron sources, and a gate electrode, and the gate current monitor is connected between the gate electrode and the cathode.

[0075] The FEA construct is operated 612D and the gate current monitor records the gate current 614D. The controller receives the gate current signal from the gate current monitor and stores it in a current log in a memory 616D.

[0076] The controller may analyze the current log 618D and, if vacuum deterioration is detected 620D, activate the getter 622D otherwise the FEA may be operated again and further gate current data accumulated until the controller identifies in the gate current log indications of vacuum deterioration within the vacuum tube. For example, indications of vacuum deterioration may include the gate current exceeding a threshold value.

[0077] In still another embodiment, the trigger condition for getter activation may be based on the operating voltage required to achieve the working anode current of the tube. During normal operation, the required operating voltage is routinely recalibrated to maintain a consistent anode current. This calibration data can be leveraged to trigger getter activation. Specifically, the controller may be configured to monitor the operating voltage over time and activate the getter unit when the operating voltage exceeds a predetermined threshold value. Alternatively, the controller may analyze the second derivative of the operating voltage's degradation. A deviation from a linear degradation pattern, as indicated by the second derivative, may signify vacuum deterioration and trigger getter activation.

[0078] The flowchart of Fig. 6E shows a calibration triggered method 600E for operating getter enabled FEA vacuum tube.

[0079] The method includes providing a vacuum tube 602E, providing a field emission array construct 604E, providing a getter unit 606E and providing a controller 608E. The field emission construct includes a cathode, a plurality of field emission type electron sources, and a gate electrode, and the gate current monitor is connected between the gate electrode and the cathode.

[0080] The FEA construct is operated 61 OE and a calibration curve may be generated of operating voltage against anode current 612E. The controller receives the calibration curve and stores it in a current log in a memory 614E.

[0081] The controller may compare the calibration curve with previously stored calibration curves 616E and analyze trends in variation of those calibration curves 618E and, if vacuum deterioration is detected 620E, activate the getter 622E otherwise the FEA may be operated again and when appropriate, recalibrated until the controller identifies indications of vacuum deterioration within the vacuum tube. For example, indications of vacuum deterioration may include operational voltage increasing above a threshold value, a non linear variation in the calibration curve or the like.

[0082] It has been surprisingly found that one early indication of vacuum deterioration includes an increase in the second derivative of the gate current. As shown in Fig. 7A, typical gate current deterioration rate is linear under a constant vacuum level. However, in the relatively small enclosed volume of a FEA vacuum tube the Gate Current deterioration rate starts to rise exponentially at a critical vacuum level such as can be seen in Fig. 7B, for example in the deviation from the linear in gate current seen after 2000 pulses. Accordingly, by using a second derivative, it is possible to know that a getter re-activation is required before significant deterioration of performance. Such a procedure may be automated by the controller. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment of the disclosure. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

[0083] Although the invention has been described in conjunction with specific embodiments thereof, it is evident that other alternatives, modifications, variations and equivalents will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications, variations and equivalents that fall within the spirit of the invention and the broad scope of the appended claims. Additionally, the various embodiments set forth hereinabove are described in terms of exemplary block diagrams, flow charts and other illustrations. As will be apparent to those of ordinary skill in the art, the illustrated embodiments and their various alternatives may be implemented without confinement to the illustrated examples. For example, a block diagram and the accompanying description should not be construed as mandating a particular architecture, layout or configuration.

Claims

CLAIMS1. A system for extending the operational lifetime of a field emission array (FEA) vacuum tube, comprising: a vacuum tube; an FEA construct positioned within the vacuum tube, the FEA construct including a cathode, a plurality of field emission type electron sources, and a gate electrode; a getter unit positioned inside the vacuum tube; and a controller configured to activate the getter unit based on a trigger condition related to the operational state of the vacuum tube.

2. The system of claim 1, further comprising a gate current monitor connected between the gate electrode and the cathode, wherein the controller is configured to receive a gate current signal from the gate current monitor, and wherein the trigger condition is based on the gate current signal.

3. The system of claim 1 , wherein the trigger condition is based on a predetermined time interval.

4. The system of claim 1 , further comprising a counter, wherein the trigger condition is based on a number of electron pulses emitted by the FEA construct.

5. The system of claim 2, wherein the controller is configured to activate the getter unit when the gate current exceeds a predetermined threshold value.

6. The system of claim 2, wherein the controller is configured to activate the getter unit when a second derivative of the gate current is increasing.

7. The system of claim 1 , wherein the getter unit comprises a Non-Evaporable Getter (NEG) material.

8. The system of claim 7, wherein the NEG material comprises a St122 type composition of 70% Titanium and 30% St707.

9. The system of claim 8, wherein the controller activates the getter unit by conductively heating the getter unit, the activation pins being capable of sustaining a current of at least 3A.

10. The system of claim 9, wherein the controller activates the getter unit by raising its temperature to approximately 500 degrees Celsius.

11. The system of claim 1 , wherein the field emission type electron sources comprise Spindt type electron sources.

12. The system of claim 1, wherein the field emission type electron sources comprise carbon nanotubes (CNTs).

13. The system of claim 1 , wherein the field emission type electron sources comprise a metal-insulator- metal (MIM) type electron source.

14. The system of claim 1 , wherein the field emission type electron sources comprise a metal-insulator- semiconductor (MIS) type electron source.

15. The system of claim 1 , further comprising activation pins for conductive activation.

16. The system of claim 1 , further comprising an activation mechanism comprising an inductive activator.

17. A system for increasing the operational lifetime of a field emission array (FEA) vacuum tube, comprising: a vacuum tube; an FEA construct positioned within the vacuum tube, the FEA construct including a cathode, a plurality of field emission type electron sources, and a gate electrode; a getter bank positioned inside the vacuum tube, the getter bank comprising a plurality of getter units; and a controller configured to selectively activate at least one getter unit within the getter bank using an activation mechanism.

18. The system of claim 17, wherein the activation mechanism comprises a conductive activator.

19. The system of claim 18, further comprising a plurality of getter activation pins extending from the vacuum tube and conductively connected to the getter units.

20. The system of claim 19, wherein the controller is configured to selectively pass a current through at least one of the getter activation pins to activate the corresponding getter unit.

21. The system of claim 17, wherein the plurality of getter units are connected in parallel to common getter activation pins.

22. The system of claim 17, wherein the plurality of getter units are connected in series to common getter activation pins.

23. The system of claim 17, wherein each of the plurality of getter units is connected to its own individual activation pin.

24. The system of claim 17, wherein the activation mechanism comprises an inductive activator.

25. The system of claim 24, wherein each getter unit is connected to a secondary inductive coil.

26. The system of claim 25, further comprising a primary induction coil positioned outside the vacuum tube and operatively coupled to the secondary inductive coils.

27. The system of claim 26, wherein the controller is configured to selectively apply a varying potential to the primary induction coil to induce a current in at least one of the secondary inductive coils, thereby activating the corresponding getter unit.

28. The system of claim 27, wherein each secondary inductive coil has a characteristic resonant frequency.

29. The system of claim 28, further comprising a frequency selector configured to provide a range of frequencies to the primary induction coil.

30. The system of claim 17, wherein the controller is configured to activate the getter units in a predetermined sequence.

31. The system of claim 17, further comprising a gate current monitor connected between the gate electrode and the cathode, wherein the controller is configured to receive a gate current signal from the gate current monitor, and wherein the controller is configured to selectively activate the getter units based on the gate current signal.

32. The system of claim 17, wherein each getter unit comprises a Non-Evaporable Getter (NEG) material.

33. A method of manufacturing a field emission array (FEA) vacuum tube with a getter, comprising the steps of: providing a vacuum tube; introducing an FEA construct into the vacuum tube, the FEA construct including a cathode, a plurality of field emission type electron sources, and a gate electrode; introducing a getter unit into the vacuum tube; evacuating gas from the vacuum tube; activating the getter unit to remove residual gas; sealing the vacuum tube; and activating the getter unit again.

34. The method of claim 33, wherein evacuating gas from the vacuum tube comprises attaching a vacuum pump to the vacuum tube.

35. The method of claim 33, wherein sealing the vacuum tube comprises pinching the glass closed.

36. The method of claim 33, wherein activating the getter unit comprises conductively heating the getter unit with a current of at least 3 A.

37. The method of claim 33, wherein activating the getter unit comprises raising its temperature to approximately 500 degrees Celsius.

38. The method of claim 33, wherein the getter unit comprises a Non-Evaporable Getter (NEG) material.

39. A method of operating a field emission array (FEA) vacuum tube with getter activation, the method comprising: providing a FEA vacuum tube including a FEA construct and a getter unit; operating the FEA construct; assessing if getter activation is due; if getter activation is due, activating the getter unit; and if getter activation is not due, continuing to operate the FEA construct and reassessing if getter activation is due.

40. The method of claim 39, further comprising: providing a clock; scheduling getter activation based upon the clock; setting the clock to zero; checking the clock to determine if getter activation is due, wherein assessing if getter activation is due comprises comparing the clock to the getter activation schedule.41 . The method of claim 39, further comprising: providing a controller; setting a trigger count (TC); setting an operation count (OC) to zero;incrementing the operation count (OC) as the FEA construct is operated, wherein assessing if getter activation is due comprises comparing the operation count (OC) to the trigger count (TC).

42. The method of claim 39, further comprising: providing a gate current monitor; monitoring a gate current; storing the gate current; and analyzing the gate current to detect vacuum deterioration, wherein assessing if getter activation is due comprises determining if vacuum deterioration is detected based on the analyzed gate current.

43. The method of claim 42, wherein analyzing the gate current to detect vacuum deterioration comprises determining if the gate current exceeds a threshold value.

44. The method of claim 42, wherein analyzing the gate current to detect vacuum deterioration comprises determining if the second derivative of the gate current is increasing.

45. The method of claim 39, wherein activating the getter unit comprises conductively heating the getter unit.

46. The method of claim 45, wherein conductively heating the getter unit comprises passing a current of at least 3A through the getter unit.

47. A method for increasing the operational lifetime of a field emission array (FEA) vacuum tube, the method comprising: providing a vacuum tube; providing an FEA construct within the vacuum tube, the FEA construct including a cathode, a plurality of field emission type electron sources, and a gate electrode; positioning a getter unit inside the vacuum tube; operating the FEA construct; and activating the getter unit based on a trigger condition related to the operational state of the vacuum tube.

48. The method of claim 47, further comprising monitoring a gate current signal, and wherein the trigger condition is based on the gate current signal.

49. The method of claim 47, wherein the trigger condition is based on a predetermined time interval.

50. The method of claim 47, further comprising counting electron pulses emitted by the FEA construct, and wherein the trigger condition is based on a number of electron pulses.

51. The method of claim 48, wherein activating the getter unit comprises activating the getter unit when the gate current exceeds a predetermined threshold value.

52. The method of claim 48, wherein activating the getter unit comprises activating the getter unit when a second derivative of the gate current is increasing.

53. The method of claim 47, wherein activating the getter unit comprises conductively heating the getter unit with a current of at least 3 A.

54. The method of claim 47, wherein activating the getter unit comprises raising its temperature to approximately 500 degrees Celsius.

55. The method of claim 47, further comprising activating the getter unit with conductive activation.

56. The method of claim 47, further comprising activating the getter unit with inductive activation.

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