CN102376514A - Cathode - Google Patents
Cathode Download PDFInfo
- Publication number
- CN102376514A CN102376514A CN2011102099198A CN201110209919A CN102376514A CN 102376514 A CN102376514 A CN 102376514A CN 2011102099198 A CN2011102099198 A CN 2011102099198A CN 201110209919 A CN201110209919 A CN 201110209919A CN 102376514 A CN102376514 A CN 102376514A
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- China
- Prior art keywords
- emitter
- negative electrode
- emission
- described negative
- face
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J35/00—X-ray tubes
- H01J35/02—Details
- H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
- H01J35/06—Cathodes
- H01J35/065—Field emission, photo emission or secondary emission cathodes
Abstract
The invention relates to a cathode with a cathode head in which an emitting electrode (1) is arranged. The emitting electrode emits electrons when a flament voltage is applied. According to the invention, the emitting electrode(1) is molded into an annular spiral band(2), and the annular spiral band(2) possesses an outwardly directed emitting electrode face (3) and an inwardly directed emitting electrode face (4). The cathode has a good blocking performance, at the same time, enables a high electron emitting rate to be realized, and has a longer service life.
Description
Background technology
The present invention relates to a kind of negative electrode.
This negative electrode is as electron source, comprises an emitter and is arranged in the X-ray tube.The electronics that is produced by said emitter quickens along the direction of anode (target).Electronics slows down when striking anode, wherein, produces a kind of X ray that can be used for diagnosing image or can be used for treating irradiation.In addition, utilize the examination of materials that X ray can realize analyzing or the check on the safe practice.
The emitter design that is suitable as electron source is the heat emission utmost point (carrying out thermionic emission through resistance heating or through the laser radiation of emitter) or an emitter (through the electronics of field emission generation).
Technical field
DE 199 55 845 A1 disclose a kind of heat emission utmost point that is designed to spiral emitter (coiled-coil filament).A kind of heat emission utmost point that is designed to flat emitter is for example disclosed in DE 27 27 907 C2 and DE 199 14 739 C1.The above-mentioned heat emission utmost point through resistance heating, that is, heats through galvanization (loading heater current) respectively.DE 10 2,005 043 372 A1 disclose a kind of emitter, and it heats and so thermal electron through laser beam when radiation.
When the operation X-ray tube; Preferably by tungsten; Apply a filament voltage (resistance heating) in the heat emission extremely that tantalum or rhenium are formed and therefore be heated to about 2000 ℃, make electronics, become electronics freely then because its warm-up movement can overcome the work function of the uniqueness of emitter material.After its heat emission, electronics quickens towards anode through the electromotive force of about 120kV.Surface at anode when the electrons hit anode produces X ray.
Usually the high temperature of coiled-coil filament that has the average line footpath of about 0.4mm causes the volatilization of emitter material and slowly the attenuating of the spiral wire that causes thus, and this finally can cause fractureing of spiral wire.In incandescent lamp, this consequence is known.
Therefore vacuum gas content in the vacuum casting of the temperatures involved X-ray tube on the emitter also weaken the vacuum effectiveness in the vacuum casting, makes emitter material produce volatilization, therefore reduced compressive resistance.Under the situation of worst, when spillage of material is too much, in emitter material, produces and fracture, this has caused the inefficacy of X-ray tube.
Have only through reducing the working temperature of spiral emitter, just can reach and reduce loss and therefore life-saving correspondingly, yet reduce the minimizing that working temperature can cause undesirable electronics emission.In order to stop the minimizing of the electronics emission that the working temperature that reduced by the spiral emitter causes, simple especially method is used in suggestion, that is, will be used for electronics radiation emitted area and do relatively largely, and needn't use higher heater current basically.This can realize through so-called flat emitter.When suitable design, this flat emitter is compared for said volume to be heated and with the spiral emitter has the obviously bigger radiation emitted area that helps.
Though planar transmit has the longer life-span, still use the spiral emitter, because flat emitter is because its bigger swept area (emission area) is difficult through the electric field obstruct.
Substitute by heat emission (the heat emission utmost point) and produce free electron, also can launch (emitter) by the field and produce free electron.This emitter is for example open by DE 10 2,005 049 601 A1 and DE 10 2,008 026 634 A1.
Through applying voltage, electronics is for example drawn in the CNT (CNT) from a kind of material with high emission current density, wherein, not necessarily will heat this material.Said CNT has the length of diameter and the some μ m of about 10nm.The superelevation electric field occurs at sharp-pointed top, this only can realize the electronics emission through field effect.Through the available current density of this emitter with less than 2A/cm
2Typical value be starkly lower than the current density of the heat emission utmost point, can realize 10A/cm through the heat emission utmost point
2Current density.
This emitter is owing to needn't heat or heating (so-called " the pop-up utmost point ") Quick connecting pipe fitting very just a little only, and this possibility makes this technology that is used for X-ray tube have a great attraction.If current density is improved several A/cm
2, with the life-span of limiting field emitter.For life-saving, as everyone knows, can a plurality of emitter modules be arranged side by side, make the total load of an emitter be assigned on these emitter modules and reduce the total load that is used for single emitter module, and therefore prolonged the life-span of an emitter.The manufacturing of emitter module is expensive and therefore correspondingly cost is very high.In addition, each emitter module control separately.Therefore this scheme is difficult to realize technically in rotarting anode-X-ray tube.
In order to obtain being used for the high field intensity greater than 1V/ μ m of electronics emission, or need high voltage, otherwise with the distance of anode must be very little.Another kind possibly be exactly to use between emitter on the scene and the anode to draw grid (Extraktionsgitters) (being control electrode Gate-Elektrode), and it is positioned on the positive potential relative with electron emission layer.When distance during, produce this field intensity through maneuverable average voltage in some kV scopes at about 100 μ m to 1mm.The said grid of drawing is made up of the for example thin tungsten filament with some 10 μ m lines footpath, and has the pitch of typical from 100 to 200 μ m.
Summary of the invention
The technical problem that the present invention will solve is, makes a kind of negative electrode that has high electron emissivity and longer life and have good barrier.
According to the present invention, above-mentioned technical problem is able to solve through the negative electrode with cathode taps, wherein is provided with emitter, said emitter emitting electrons when applying filament voltage.According to the present invention, said emitter is shaped to the hurricane band of annular, and said hurricane band has outwards directed an emission pole-face and the emission pole-face to interior orientation.Because this emitter is shaped to hurricane band according to the present invention, rather than as from prior art known be shaped to helix, said emitter has the cross section that is different from circular cross section.Therefore produce for spiral emitter at the emitter that is provided with in according to negative electrode of the present invention and obtain obvious improved surface-volume-ratio, make the volatilization of emitter material reduce significantly with circular cross section with non-circular cross sections.
According to one of negative electrode of the present invention favourable expansion design, the hurricane band of said annular has the cross section (n >=3) of n dihedral, therefore for example can be embodied as trapezoidal, rectangular, cross section rhombus or foursquare.In hurricane band, also can realize and conventional n dihedral different cross-sectional areas.
Do not have as known flat emitter according to negative electrode of the present invention; One side of only using emitter usually is as emitter area (emission area); Can be but become freely electronics from both sides through thermionic emission, that is, and from the emission pole-face of outside orientation with from emission pole-face to interior orientation; Towards said anode suction, anode is arranged on the center of negative electrode usually through external electric field.Through according to solution of the present invention-compare-correspondingly increased spendable emission area with traditional flat emitter that only has an available emission pole-face.
On the physics, define the emission current of adjustment through Jason Richardson's equation:
Wherein,
The I emission current,
A Jason Richardson constant,
A
eEmission area,
T absolute transmission utmost point temperature (K),
W
AFrom the work function of the electronics of emitter material (for tungsten 10
6Am
-2K
-1),
k
BBoltzmann constant
Therefore, under the common constant situation of parameter, can increase emission current through increasing spendable emission area.On the contrary, under lower emission temperature, can reach same emission current, this makes evaporation reduce and has therefore prolonged the emitter life-span.
In addition, through the location flexibly or the orientation of hurricane band in electric field, from the emission pole-face of outside orientation, be improved with comparing with traditional spiral emitter (coiled-coil filament) from the extraction of electrons emitted on the emission pole-face of interior orientation.If the circular cross section level that will be present in the coiled-coil filament (spiral wire) is divided into two and half shells, the surface normal of lower half shell always is in reverse to or deviates from preferred acceleration direction.This causes undesirable runaway electron, and especially when when lower high pressure (for example 20kV) moves X-ray tube down, because in this case, not every electronics all can quicken towards anode.Therefore these loss electronics do not contribute to tube current and collide with the inwall of vaccum case, and this has caused extra, undesirable heating to vaccum case.
In contrast, the surface normal of the emitter area of wide annular (the main surface of overflowing that is used for electrons emitted) when being set to 90 degrees with hurricane band perpendicular to acceleration direction.Therefore, more polyelectron can quicken towards anode direction.For the quantum of output of the electronics that helps tube current increases, the loss electronics reduces.In addition, the emitter area of the contrary acceleration direction of its surface normal reduces to minimum through the vertical location of the hurricane band in the vaccum case.
Because the hurricane band of said annular can not seal based on conduction ground contacting, has produced so-called " emission defect point " at the contact position place, its along at X-ray tube constitutes bright zone and has therefore hindered the even distribution of focus.If the emission defect point is inevitable,,, a contacting foot is set in each end of the hurricane band of annular according to the especially favourable expansion design of negative electrode of the present invention in order at least obviously to be reduced in this emission defect point in the contact position zone.Said contacting foot also has following advantage in this position as replenishing the surface of emission, that is, conductive contact is connected and needn't directly on the hurricane band of annular, be realized.When directly conductive contact was connected, transition point was because the heat radiation of contact material is colder than the actual transmission face of emission pole-face mostly.This is once more owing to low temperature produces the emission defect point.
Contact base favourable is arranged in principle with the cross section of the hurricane band of annular irrelevant, and therefore in all designs according to negative electrode of the present invention, can realize.
Description of drawings
Describe four embodiment of the present invention in detail by accompanying drawing below, yet the present invention is not limited thereto.In the drawings,
Fig. 1 shows first kind of execution mode according to emitter of the present invention,
Fig. 2 shows second kind of execution mode according to emitter of the present invention,
Fig. 3 shows the third execution mode according to emitter of the present invention,
Fig. 4 shows the 4th kind of execution mode according to emitter of the present invention.
Embodiment
Said emitter 1 be arranged on a negative electrode not on the cathode taps shown in Fig. 1 to Fig. 4.
In the execution mode of Fig. 1 description according to negative electrode of the present invention, outwards directed emission pole-face 3 is in vertical position respectively with the emission pole-face 4 to interior orientation.The hurricane band 2 of said annular has constant diameter along emission pole-face 3 and 4.This normal structure can be realized through manufacturing technology especially simply.
According to the design of Fig. 2 and Fig. 3, the hurricane band 2 of said annular is with to compare angle at the embodiment shown in Fig. 1 different, is in order to reach the optimal orientation in electric field, and wherein, electric field is to form through outside negative electrode, presenting how much situation.
In technical scheme shown in Figure 2, the emitter mask of the outside orientation of toroidal helical band 2 has pyramidal gradient, in contrast, for the emitter among Fig. 3, the emission pole-face 3 infundibulate crustal inclination of the outside orientation of the hurricane band 2 of annular.In the emitter of Fig. 2, the diameter of the last seamed edge of the hurricane band 2 of annular is less than the diameter of the following seamed edge of the hurricane band 2 of annular.In contrast, in the emitter of Fig. 3, the diameter of the last seamed edge of the hurricane band 2 of annular is greater than the diameter of the following seamed edge of the hurricane band 2 of annular.
Ideally, the Potential Distributing in both sides is identical.Yet the variation through angle can realize electron opticly the operation that is directed against being arranged and be positioned at the focus distribution on the anode.
Because the hurricane band 2 of said annular can not seal based on the contacting of conduction; So produced in the contacting position so-called " emission defect point ", its along at X-ray tube constitutes bright zone and has therefore hindered the even distribution of focus.
Can be in an advantageous manner contacting foot 5 and 6 be set and remedies, as realizing in the described design of Fig. 4 through end at the hurricane band 2 of annular.Said contacting foot 5 and 6 also has following advantage in this position as replenishing the surface of emission, that is, the contacting of conduction needn't directly be realized on the hurricane band 2 of annular.When the contacting that directly conducts electricity, transition point is because the heat radiation of contact material is colder than the actual transmission face of emission pole- face 3 and 4 mostly.This is once more because low temperature produces the emission defect point.
Contacting foot 5 and 6 favourable be provided with nature can through Fig. 1 extremely embodiment illustrated in fig. 3 realize without a doubt.
Make this negative electrode when having good barrier, also can realize high electronics emission and have the longer life-span according to the execution mode of all descriptions of negative electrode of the present invention.
Claims (13)
1. negative electrode that has cathode taps; Wherein be provided with emitter (1); Said emitter emitting electrons when applying filament voltage; It is characterized in that said emitter (1) is shaped to the hurricane band (2) of annular, this hurricane band has the emission pole-face (3) of outside orientation and to the emission pole-face (4) of interior orientation.
2. according to the described negative electrode of claim 1, it is characterized in that said emitter (1) is designed to the hurricane band (2) of annular.
3. according to the described negative electrode of claim 1, it is characterized in that said emitter (1) has the cross section (n >=3) of n dihedral.
4. according to the described negative electrode of claim 1, it is characterized in that said emitter (1) has trapezoidal cross section.
5. according to the described negative electrode of claim 1, it is characterized in that said emitter (1) has rectangular cross section.
6. according to the described negative electrode of claim 1, it is characterized in that said emitter (1) has the cross section of rhombus.
7. according to the described negative electrode of claim 1, it is characterized in that said emitter (1) has a foursquare cross section.
8. according to the described negative electrode of claim 1, it is characterized in that said hurricane band (2) has constant thickness.
9. according to the described negative electrode of claim 1, it is characterized in that the emission pole-face (3) of said outside orientation is parallel to the vertical axis extension of said emitter (1).
10. according to the described negative electrode of claim 1, it is characterized in that the said vertical axis extension that is parallel to said emitter (2) to the emission pole-face (4) of interior orientation.
11., it is characterized in that the emission pole-face (3) of said outside orientation is with respect to angle of longitudinal axis inclination of said emitter (1) according to the described negative electrode of claim 1.
12., it is characterized in that said emission pole-face (4) to interior orientation is with respect to the longitudinal axis of said emitter (1) angle that tilts according to the described negative electrode of claim 1.
13. according to the described negative electrode of claim 1, it is characterized in that, contacting foot (5,6) be set in the end of the hurricane band (2) of said annular.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE201010038904 DE102010038904B4 (en) | 2010-08-04 | 2010-08-04 | cathode |
| DE102010038904.8 | 2010-08-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN102376514A true CN102376514A (en) | 2012-03-14 |
Family
ID=45495010
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011102099198A Pending CN102376514A (en) | 2010-08-04 | 2011-07-26 | Cathode |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN102376514A (en) |
| DE (1) | DE102010038904B4 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104717816A (en) * | 2013-12-11 | 2015-06-17 | 西门子公司 | X-Ray Tube Assembly |
| CN106783517A (en) * | 2016-12-19 | 2017-05-31 | 韩婧杰 | Face shape illuminating lamp |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4012656A (en) * | 1974-12-09 | 1977-03-15 | Norman Ralph L | X-ray tube |
| US4473777A (en) * | 1982-09-29 | 1984-09-25 | The Perkin-Elmer Corporation | Electron emitter assembly |
| CN2242521Y (en) * | 1995-11-16 | 1996-12-11 | 谭大刚 | Medical X-ray tube of fluorescent-enhancement type |
| CN1981360A (en) * | 2004-05-27 | 2007-06-13 | 卡伯特微电子公司 | X-ray source with nonparallel geometry |
| CN101720491A (en) * | 2007-04-20 | 2010-06-02 | 帕纳科有限公司 | X-ray source |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT265448B (en) * | 1963-04-30 | 1968-10-10 | Matsushita Electronics Corp | Process for the production of flat cathodes for electron tubes |
| DE2727907A1 (en) | 1977-06-21 | 1979-01-18 | Siemens Ag | X-ray tube glow cathode |
| JPS5568056A (en) * | 1978-11-17 | 1980-05-22 | Hitachi Ltd | X-ray tube |
| DE19914739C1 (en) | 1999-03-31 | 2000-08-03 | Siemens Ag | Cathode with directly heated emitter |
| DE19955845A1 (en) | 1999-11-19 | 2001-05-31 | Siemens Ag | Cathode for vacuum tube e.g. for X=ray tube |
| DE102005043372B4 (en) | 2005-09-12 | 2012-04-26 | Siemens Ag | X-ray |
| DE102005049601A1 (en) | 2005-09-28 | 2007-03-29 | Siemens Ag | X-ray beam generator for use in clinical computer tomography has positive ion filter electrode located in vicinity of cold electron gun |
| DE102008026634B4 (en) | 2008-06-04 | 2011-01-05 | Siemens Aktiengesellschaft | Field emission cathode and X-ray tube with a field emission cathode |
-
2010
- 2010-08-04 DE DE201010038904 patent/DE102010038904B4/en active Active
-
2011
- 2011-07-26 CN CN2011102099198A patent/CN102376514A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4012656A (en) * | 1974-12-09 | 1977-03-15 | Norman Ralph L | X-ray tube |
| US4473777A (en) * | 1982-09-29 | 1984-09-25 | The Perkin-Elmer Corporation | Electron emitter assembly |
| CN2242521Y (en) * | 1995-11-16 | 1996-12-11 | 谭大刚 | Medical X-ray tube of fluorescent-enhancement type |
| CN1981360A (en) * | 2004-05-27 | 2007-06-13 | 卡伯特微电子公司 | X-ray source with nonparallel geometry |
| CN101720491A (en) * | 2007-04-20 | 2010-06-02 | 帕纳科有限公司 | X-ray source |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104717816A (en) * | 2013-12-11 | 2015-06-17 | 西门子公司 | X-Ray Tube Assembly |
| CN104717816B (en) * | 2013-12-11 | 2017-10-10 | 西门子公司 | X-ray radiator |
| US9848483B2 (en) | 2013-12-11 | 2017-12-19 | Siemens Aktiengesellschaft | X-ray tube assembly |
| CN106783517A (en) * | 2016-12-19 | 2017-05-31 | 韩婧杰 | Face shape illuminating lamp |
Also Published As
| Publication number | Publication date |
|---|---|
| DE102010038904A1 (en) | 2012-02-09 |
| DE102010038904B4 (en) | 2012-09-20 |
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| PB01 | Publication | ||
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| RJ01 | Rejection of invention patent application after publication | ||
| RJ01 | Rejection of invention patent application after publication |
Application publication date: 20120314 |