EP0464383B1 - Plasma neutralisation cathode - Google Patents
Plasma neutralisation cathode Download PDFInfo
- Publication number
- EP0464383B1 EP0464383B1 EP91109114A EP91109114A EP0464383B1 EP 0464383 B1 EP0464383 B1 EP 0464383B1 EP 91109114 A EP91109114 A EP 91109114A EP 91109114 A EP91109114 A EP 91109114A EP 0464383 B1 EP0464383 B1 EP 0464383B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- holder
- emitter
- thermal emitter
- passage
- thermal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J3/00—Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
- H01J3/02—Electron guns
- H01J3/025—Electron guns using a discharge in a gas or a vapour as electron source
Abstract
Description
- This invention relates generally to glowing compensation cathodes, and more particularly to plasma compensation cathodes.
- There is known a glowing cathode (cf., Schats M.F."Heaterless Ignition of Inert Gas. Ion Thruster Hollow Cathodes" AJAA Paper, 1985) comprising a casing with a cylindrical insert secured to the inner surface of the casing and functioning as thermal emitter, a heater secured at the outer side of the casing, and an orifice secured to end face of the casing and acting as the outlet hole of the cathode. This construction of cathode requires high power heaters to heat thermal emitter to a temperature ensuring thermoionic emission sufficient for maintaining a stable discharge.
- There is also known a plasma compensation cathode (cf., L.A. Artsimovich, et al "Razrabotka statsionarnogo plazmennogo dvigatelya i ego ispytanie na iskusstvennom sputnike Zemli Meteor", Kosmicheskie issledovania, 1974, tom XII, vyp. 3, pages 455 and 456, Fig. 5). This compensation cathode has a casing with an outlet hole at one wall thereof, the casing accommodating coaxially to its outlet hole a tubular holder receiving a thermal emitter with a central through passage. The compensation cathode also includes a heater embracing the tubular holder, and heat screens positioned between the holder and casing walls. Connected to the tubular holder is a pipe for feeding gas to the interior of the casing and to the passage of thermal emitter through its inlet portion. This pipe is secured in the casing through an insulator.
- During operation of the compensation cathode gas is conveyed through the tubular holder to the passage of the thermal emitter. Heated to a high temperature, the thermal emitter ensures emission of electrons sufficient for maintaining stable electric discharge between the inner surface of the thermal emitter and anode of the plasma source. After bringing the device to steady-state operation conditions the heater is deenergized, and the compensation cathode continues to operate automatically, whereby the preferred temperature level is ensured by the energy liberated in the catholyte layer approximating to the product of ionic current resulting from discharge by the potential drop at the cathode. However, in the course of operation the discharge can move from the passage of the thermal emitter to the interior of the tubular holder resulting in evaporation of the material of the holder and fouling of the passage with holder material to almost complete clogging. As a result, thermoemission surfaces tend to degrade, and thermoemission current tends to decrease thereby reducing the service life of the compensation cathode to only tens of hours. In addition, direct connection of the holder of thermal emitter to the gas feeding pipe leads to vigorous heat transfer from the emitter to outer structural parts, and consequently to move prominent catholyte potential drop ensuring the energy necessary for maintaining automatic operating conditions. More prominent catholyte potential drop also leads to reduced service life of the thermal emitter because of intensified ionic bombardment. In addition, tight contact of thermoemissive materials with the holder at high working temperatures is accompanied by active chemical interaction, such as penetration of boron followed by formation of metal borides, which in turn causes embrittlement and cracking of the holder material and thermal emitter to result in irreversible deformation of the holder. This disadvantageous effect is especially pronounced at starting operating conditions accompanied by the highest temperature levels, which limits the service life and reduces the total number of engagements of the compensation cathode. Also, the helical heater embracing the tubular holder is characterized by low rigidity to result in sagging and deformation of its coils resulting in possible contact of the coils with the holder or thermal screens and short-circuiting of the heater. This in turn leads to fewer engagements of the compensation cathode and reduced service life thereof. In addition, the working gas can contain negligible quantities of such admixtures as oxygen, water, or the like, tending to react at high working temperatures with the material of the thermal emitter and affecting the thermoemissive characteristics of the material. Extended operation for tens or hundreds of hours makes this disadvantageous effect even more prominent to reduce the service life of the compensation cathode.
- The present invention aims at providing a plasma compensation cathode which would be so constructed as to lock discharge zone in the passage of the thermal emitter, prevent chemical interaction of the thermal emitter with the material of the holder and with the thermal system maintaining automatically the preferred temperature of the thermal emitter at minimised cathodic potential drop, and also to increase the rigidity of the heater and facilitate additional cleaning of gas from impurities.
- The aim of the invention is attained by a plasma compensation cathode according to the claim.
- The use in the proposed plasma compensation cathode of a thermal emitter with a special passage for feeding gas, a layer of chemically inert material, a system of coaxial heat screens, a support ring, an insulation sleeve, a getter, and mechanical filters makes it possible to substantially extend the service life and increase the total number of actuations of the cathode.
- The invention will now be described in greater detail with reference to a specific embodiment thereof taken in conjunction with the accompanying drawings, in which:
- Fig. 1 shows a general view of the proposed plasma compensation cathode; and
- Fig. 2 is a section taken along
line 11 in Fig. 1 - A plasma compensation cathode comprises a casing 1 (Fig. 1) having an
inlet hole 2. The casing accommodates coaxially ahollow holder 3 and athermal emitter 4 with acentral passage 5. Theholder 3 is positioned inside casing 1 coaxially with theoutlet hole 2 and embraced by aheater 6 fashioned as a spiral one end of which is secured to the casing and the other to theholder 3. Theheater 6 is provided with asupport ring 7 located at its midportion and functioning as an additional support point. - The
central passage 5 of thethermal emitter 4 is blind at the side of admission of gas, and is communicated with the interior of theholder 3 by way of a central passage 8 (Fig. 2) made in the wall of thethermal emitter 4, the axis of this passage extending perpendicularly to the axis of thecentral passage 5, andlongitudinal grooves 9 provided at the side surface of thethermal emitter 4 at location of the inlet holes of thethrough passage 8. Occupying the space between the inner surface of theholder 3 and side surface of thethermal emitter 4 is a layer 10 (Fig. 1) of material chemically inert at high temperatures to the materials of theholder 3 andthermal emitter 4. Positioned between theheater 6 and walls of casing 1 is a system ofcoaxial heat screens 11 connected successively throughspacer rings 12 and secured atpipe 13 for feeding gas to define a sealedcavity 14 wherethrough the interior of theholder 3 communicates with thegas feeding pipe 13. A space between theholder 3 andpipe 13 accommodates agetter 15 positioned betweenmechanical filters 16, whereas thepipe 13 is secured in asupport insulator 17. Theheater 6 is separated from the system ofheat screens 11 by aninsulation sleeve 18 in which thesupport ring 7 is secured. - In operation of the proposed plasma compensation cathode the gas flows along the
pipe 13 through thegetter 15 andmechanical filters 16 to the interior of theholder 3, and then through thegrooves 9 and throughpassage 8 to thecentral passage 5 of thethermal emitter 4. Theheater 6 acts to heat thethermal emitter 4 to a temperature ensuring emission of electrons sufficient for sustaining a stable electric discharge between the inner surface of thethermal emitter 4 and anode (not shown) of a plasma source. After bringing the device to steady state operating conditions theheater 6 is deenergized and the compensation cathode operates automatically, whereby the required temperature level of thethermal emitter 4 is ensured thanks to the energy resulting from the discharge. - When the
central passage 5 at the side of admission of gas is blind, the electric discharge inpassage 5 can be stabilized by changing the pressure of gas and dimensions of thepassage 5. This prevents fixation of discharge at the walls ofholder 3 resulting in fouling and clogging ofpassage 5 of thethermal emitter 4, which facilitates maintaining the initial thermal emission from the inner surface of thethermal emitter 4 and substantially increases the service life of the compensation cathode. Positioning between the inner surface ofholder 3 and side surface of thethermal emitter 4 oflayer 10 of material chemically inert to the material of holder andthermal emitter 4 obviates chemical interaction and diffusion of materials thereby making impossible irreversible deformation ofholder 3 and cracking ofholder 3 andthermal emitter 4. The accompanying advantage is substantially increased number of actuations and extended service life of the cathode. - The system of
coaxial heat screens 11 defining withgas feeding pipe 13 and holder 3 a sealedcavity 14 makes it possible to substantially reduce the heat flow fromholder 3 of thethermal emitter 4 to outer parts of the cathode structure and, as a consequence, to reduce the potential drop at the cathode to the level of gas ionization potential and substantially extend the service life of the compensation cathode. - Provision of the
support ring 7 secured in theinsulation sleeve 18 allows to increase rigidity of the spiral ofheater 6, prevent short-circuiting of the spiral of heater 6 (viz., engagement of the spiral coils withholder 3 or screens 11) even at a substantial deformation of spiral coils due to multiple engagement thermocycles. This again enables to increase the number of actuations and extend the service life of the compensation cathode. - Provision of the proposed compensation cathode with
getter 15 positioned betweenmechanical filters 16 immediately at the location where the gas is admitted to the interior of theholder 3 affords extra fine chemical cleaning of gas from admixtures of oxygen, water, and the like, and ensures more stable thermoemission characteristics ofthermal emitter 4 resulting in an extended service life of the compensation cathode. - The invention can be used for neutralizing ion beams in accelerators with closed electron drift and extended acceleration zone, in accelerators with anodic layer and narrow acceleration zone, in plasma-ion accelerators, and also for compensating space and surface discharges.
Claims (1)
- A plasma compensation cathode comprising a casing (1) accommodating coaxially with its outlet hole (2) a hollow, tubular holder (3) which is embraced by a heater (6), and a thermal emitter (4) with a central passage (5) communicating with the interior of the holder (3), whereby said thermal emitter is positioned within the holder, the cathode further comprising coaxial heat screens (11) interposed between the heater (6) and walls of the casing (1), and a pipe (13) for feeding a gas to the interior of the holder (3), said pipe being secured in a support insulator (17),
CHARACTERIZED in that the central passage (5) of thermal emitter (4) is blind at the end of the emitter which is closer to the gas admission through the pipe, and communicates with the interior of the holder (3) by way of a through passage (8) made in the wall of the thermal emitter (4) so that its axis intersects the axis of the central passage (5), and longitudinal grooves (9) along the side surface of the thermal emitter (4) from the location of the inlet holes of the through passage (8) to the end of the emitter which is closer to the gas feeding pipe (13); a getter (15) is positioned between mechanical filters (16) at the location where the gas is admitted to the interior of the holder; whereby the interior of the holder (3) communicates with the gas feeding pipe (13) through a sealed cavity (14), said cavity being defined by clearances between the coaxial heat screens (11) which are successively connected by spacer rings (12) and secured at the gas feeding pipe (13), a space between the inner surface of the holder (3) and side surface of the thermal emitter (4) accommodating a layer (10) of material chemically inert at high temperatures to the material of the holder (3) and the thermal emitter (4), whereby the the cavity (14) accommodates the getter (15) positioned between the holder and the gas feeding pipe; and the heater (6) at a midportion thereof is provided with a support ring (7) which is secured in an insulation sleeve (18) separating the thermal heater (6) from the coaxial thermal screens (11).
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
SU904843045A RU2012946C1 (en) | 1990-06-26 | 1990-06-26 | Plasma cathode-compensator |
SU4843045 | 1990-06-26 |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0464383A2 EP0464383A2 (en) | 1992-01-08 |
EP0464383A3 EP0464383A3 (en) | 1992-07-15 |
EP0464383B1 true EP0464383B1 (en) | 1994-09-21 |
Family
ID=21523026
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP91109114A Expired - Lifetime EP0464383B1 (en) | 1990-06-26 | 1991-06-04 | Plasma neutralisation cathode |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0464383B1 (en) |
JP (1) | JP2963903B2 (en) |
AT (1) | ATE112096T1 (en) |
DE (1) | DE69104142T2 (en) |
RU (1) | RU2012946C1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN105626410A (en) * | 2015-12-25 | 2016-06-01 | 上海空间推进研究所 | Plume neutralizer of space electric thruster |
CN111720281A (en) * | 2020-06-24 | 2020-09-29 | 遨天科技(北京)有限公司 | Array coaxial type vacuum arc thruster device |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE19813589C2 (en) * | 1998-03-27 | 2002-06-20 | Karlsruhe Forschzent | Method for generating a pulsed electron beam and electron beam source for carrying out the method |
FR2897747B1 (en) * | 2006-02-23 | 2008-09-19 | Commissariat Energie Atomique | ARC PLASMA TORCH TRANSFER |
CN102355791A (en) * | 2011-09-28 | 2012-02-15 | 南京创能电力科技开发有限公司 | Device for insulation connecting between cathode and anode of plasma generator |
RU2502238C2 (en) * | 2012-02-07 | 2013-12-20 | Федеральное государственное унитарное предприятие "Опытное конструкторское бюро "Факел" | Plasma cathode |
RU2667155C1 (en) * | 2017-03-28 | 2018-09-17 | Федеральное государственное унитарное предприятие "Опытное конструкторское бюро "Факел" ФГУП "ОКБ "Факел" | Hollow cathode |
RU2662795C1 (en) * | 2017-04-18 | 2018-07-31 | Федеральное государственное унитарное предприятие "Опытное конструкторское бюро "Факел" ФГУП "ОКБ "Факел" | Hollow cathode |
RU2684633C2 (en) * | 2017-05-10 | 2019-04-11 | Федеральное государственное унитарное предприятие "Опытное конструкторское бюро "Факел" (ФГУП "ОКБ "Факел") | Cathode-compensator |
RU2684309C1 (en) * | 2018-03-14 | 2019-04-08 | Федеральное государственное унитарное предприятие "Опытное конструкторское бюро "Факел" ФГУП "ОКБ "Факел" | Plasma hollow cathode |
CN113371233B (en) * | 2021-07-29 | 2022-08-30 | 哈尔滨工业大学 | Anode structure and cusp field thruster |
CN114320801B (en) * | 2021-12-28 | 2022-07-01 | 哈尔滨工业大学 | Cold cathode capable of being started quickly |
CN114458564B (en) * | 2022-04-12 | 2022-07-12 | 国科大杭州高等研究院 | Hall thruster ring type partial pressure gas path insulation structure |
CN115681054B (en) * | 2023-01-03 | 2023-05-09 | 国科大杭州高等研究院 | Self-maintaining Hall thruster |
Family Cites Families (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5853460B2 (en) * | 1981-12-14 | 1983-11-29 | 株式会社東芝 | Hollow cathode discharge device |
JPS58169752A (en) * | 1982-03-30 | 1983-10-06 | Toshiba Corp | Hollow-cathode discharge device |
-
1990
- 1990-06-26 RU SU904843045A patent/RU2012946C1/en active
-
1991
- 1991-06-04 DE DE69104142T patent/DE69104142T2/en not_active Expired - Fee Related
- 1991-06-04 AT AT91109114T patent/ATE112096T1/en active
- 1991-06-04 EP EP91109114A patent/EP0464383B1/en not_active Expired - Lifetime
- 1991-06-25 JP JP3180134A patent/JP2963903B2/en not_active Expired - Lifetime
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN105626410A (en) * | 2015-12-25 | 2016-06-01 | 上海空间推进研究所 | Plume neutralizer of space electric thruster |
CN105626410B (en) * | 2015-12-25 | 2018-08-03 | 上海空间推进研究所 | A kind of space electric thruster plume averager |
CN111720281A (en) * | 2020-06-24 | 2020-09-29 | 遨天科技(北京)有限公司 | Array coaxial type vacuum arc thruster device |
Also Published As
Publication number | Publication date |
---|---|
JP2963903B2 (en) | 1999-10-18 |
DE69104142T2 (en) | 1995-01-19 |
RU2012946C1 (en) | 1994-05-15 |
JPH04299000A (en) | 1992-10-22 |
EP0464383A3 (en) | 1992-07-15 |
ATE112096T1 (en) | 1994-10-15 |
DE69104142D1 (en) | 1994-10-27 |
EP0464383A2 (en) | 1992-01-08 |
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