Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597061
M. Akemoto, S. Takeda
Accelerator Test Facility (ATF) is now under construction to develop the major accelerator components of Japan Linear Collider (JLC)[l]. The ATF consists of a 1.54 GeV S-band linear accelerator and 1.54 GeV damping ring. Nine 85 MW klystrons (TOSHIBA W712) are used as rf sources of the linac. Various components have been developed for compact size, high efficiency, high stability and long life of modulators. In order to make a compact modulator, a compact self-healing (SH) type of capacitor has been developed. Three compact pulse modulators have been designed and constructed to drive the 85 MW klystrons. In this paper, the design, specifications and results of performance tests of the modulators are described.
{"title":"Pulse Modulator Developments For Japan Linear Collider","authors":"M. Akemoto, S. Takeda","doi":"10.1109/MODSYM.1994.597061","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597061","url":null,"abstract":"Accelerator Test Facility (ATF) is now under construction to develop the major accelerator components of Japan Linear Collider (JLC)[l]. The ATF consists of a 1.54 GeV S-band linear accelerator and 1.54 GeV damping ring. Nine 85 MW klystrons (TOSHIBA W712) are used as rf sources of the linac. Various components have been developed for compact size, high efficiency, high stability and long life of modulators. In order to make a compact modulator, a compact self-healing (SH) type of capacitor has been developed. Three compact pulse modulators have been designed and constructed to drive the 85 MW klystrons. In this paper, the design, specifications and results of performance tests of the modulators are described.","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115516690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597095
C.A. Pirrie, C. A. Roberts, P. W. Robinson, K. Cook
It is well known that hydrogen thyratrons can hold-off inverse voltages which are equal in magnitude to their forward voltage hold-off ratings with impunity, provided that a sufficient time is allowed to lapse after forward conduction has ceased. However, circuits exist where it is not feasible to avoid the application of appreciably large inverse voltages at the thyratron anode immediately upon the cessation of forward current. Bi-directional hollow-anode thyratrons which can conduct peak reverse currents of many kiloamps are oftcn used to overcqme this problem [l], [2]. However, there arc instances where large inverse currents cannot be tolerated, either because of the effect produced at the load, or because of recovery time considerations, and the use of hollow-anode thyratrons must therefore be ruled out. Applications where such circuits can be found include medium-to-high power copper vapour lasers and certain types of kicker magnets. This paper describes the phenomena of thyratron arc-back and anode erosion which can result from high inverse voltage. The mechanisms by which these phenomena affect thyratron performance are discussed. A relatively simple saturable anode inductor is shown to alleviate greatly the phenomenon of arc-back, by providing a delay between the cessation of forward current and the application of inverse voltage. The performance of an experimental thyratron in a high repetition rate circuit with appreciable inverse voltage is also described. Lifetest results indicate that substantial improvement in operating life has been obtained by controlling the adverse effects of anode erosion, induced by high inverse voltages.
{"title":"Thyratron Design & Circuit Techniques To Overcome The Adverse Effects Of High Inverse Voltages","authors":"C.A. Pirrie, C. A. Roberts, P. W. Robinson, K. Cook","doi":"10.1109/MODSYM.1994.597095","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597095","url":null,"abstract":"It is well known that hydrogen thyratrons can hold-off inverse voltages which are equal in magnitude to their forward voltage hold-off ratings with impunity, provided that a sufficient time is allowed to lapse after forward conduction has ceased. However, circuits exist where it is not feasible to avoid the application of appreciably large inverse voltages at the thyratron anode immediately upon the cessation of forward current. Bi-directional hollow-anode thyratrons which can conduct peak reverse currents of many kiloamps are oftcn used to overcqme this problem [l], [2]. However, there arc instances where large inverse currents cannot be tolerated, either because of the effect produced at the load, or because of recovery time considerations, and the use of hollow-anode thyratrons must therefore be ruled out. Applications where such circuits can be found include medium-to-high power copper vapour lasers and certain types of kicker magnets. This paper describes the phenomena of thyratron arc-back and anode erosion which can result from high inverse voltage. The mechanisms by which these phenomena affect thyratron performance are discussed. A relatively simple saturable anode inductor is shown to alleviate greatly the phenomenon of arc-back, by providing a delay between the cessation of forward current and the application of inverse voltage. The performance of an experimental thyratron in a high repetition rate circuit with appreciable inverse voltage is also described. Lifetest results indicate that substantial improvement in operating life has been obtained by controlling the adverse effects of anode erosion, induced by high inverse voltages.","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114462153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597081
R. Hitchcock
The constructional details of pulse transformers and their effects on waveforms present problems to designers of high voltage modulators. In applications of line type modulators where pulse flatness is critical, a pulse transformer can introduce ripple on the waveforms that cannot be compensated for by making adjustments to the pulse forming network. Some investigators have solved this problem experimentally by adding a damping network to the secondary winding to improve the pulse flatness. The lack of sufficient pulse transformer models has led the author to investigate a pulse transformer model that is based on the physical construction of an actual device. W. H. Bostick presented a useful pulse transformer model in chapter 12 of “Pulse Generators” of the MIT Rad. Lab. Series and discussed the windings’ transmission line effect. The waveform distortion caused by the transmission line effect is modeled into the Secondary by including a series inductance with the secondary capacitance to ground. Bostick claimed this to be “a crude approximation”.
脉冲变压器的结构细节及其对波形的影响是高压调制器设计人员面临的难题。在线路型调制器的应用中，脉冲平坦度是至关重要的，脉冲变压器会在波形上引入纹波，无法通过调整脉冲形成网络来补偿。一些研究者通过实验解决了这个问题，通过在次级绕组上增加阻尼网络来改善脉冲平坦度。由于缺乏足够的脉冲变压器模型，作者研究了一种基于实际设备物理结构的脉冲变压器模型。W. H. Bostick在MIT Rad实验室的“脉冲发生器”第12章中提出了一个有用的脉冲变压器模型。并讨论了绕组对传输线的影响。通过在次级电容中加入串联电感，将传输线效应引起的波形畸变模拟到次级电容中。博斯蒂克称这只是“粗略的近似”。
{"title":"The Development Of A Distributed Linear Pulse Transformer Model","authors":"R. Hitchcock","doi":"10.1109/MODSYM.1994.597081","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597081","url":null,"abstract":"The constructional details of pulse transformers and their effects on waveforms present problems to designers of high voltage modulators. In applications of line type modulators where pulse flatness is critical, a pulse transformer can introduce ripple on the waveforms that cannot be compensated for by making adjustments to the pulse forming network. Some investigators have solved this problem experimentally by adding a damping network to the secondary winding to improve the pulse flatness. The lack of sufficient pulse transformer models has led the author to investigate a pulse transformer model that is based on the physical construction of an actual device. W. H. Bostick presented a useful pulse transformer model in chapter 12 of “Pulse Generators” of the MIT Rad. Lab. Series and discussed the windings’ transmission line effect. The waveform distortion caused by the transmission line effect is modeled into the Secondary by including a series inductance with the secondary capacitance to ground. Bostick claimed this to be “a crude approximation”.","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121708778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597065
H. Yasotornrat
147 Any lead or lag in current with respect to the applied voltage is called a power factor loss and depends upon the degree of lead or lag. Since the power is distributed as an Alternating Current ( AC) in a sine wave form, this lead or lag can be measured as an angle with respect to some time zero and both the current and voltage can be shown as related to each other by this angle ( hence the term phase angle ).
{"title":"Three Phase Power Factor Corrections And Three Phase Current Balance For Electrical Power Distribution Systems","authors":"H. Yasotornrat","doi":"10.1109/MODSYM.1994.597065","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597065","url":null,"abstract":"147 Any lead or lag in current with respect to the applied voltage is called a power factor loss and depends upon the degree of lead or lag. Since the power is distributed as an Alternating Current ( AC) in a sine wave form, this lead or lag can be measured as an angle with respect to some time zero and both the current and voltage can be shown as related to each other by this angle ( hence the term phase angle ).","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122612951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597056
F.E. Peterkin, K. Schoenbach, R. Block, R. Dougal, M. McKinney
{"title":"Studies Of Breakdown In Photoconductive GaAs Switches","authors":"F.E. Peterkin, K. Schoenbach, R. Block, R. Dougal, M. McKinney","doi":"10.1109/MODSYM.1994.597056","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597056","url":null,"abstract":"","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"545 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123377717","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597080
R. Gardenghi, R. C. Houlne, B.G. Keggins, L. E. Wilson, K.R. Maerten
This paper describes the design, testing and performance of a new high voltage transformer. An existing compact lightweight high voltage transformer was re-designed to improve its reliability and maintainability. The transformer is used in a dc power supply which is nominally rated at 100 kV and 1.5 Amperes. The entire supply is located within a pressure vessel with Sulphur Hexafluoride ( S F g ) gas for insulation and cooling. The original design encompassed a delta-wye transformation with zig-zag secondaries to provide 12 pulse rectification. The windings were configured in concentric coil pairs with the small (zag) secondary mounted outside the main (zig) windings with molded-in-place silicone rubber spacers. The unit performed well except for a relatively high failure rate due primarily to insulation breakdown between the zig and the zag windings. The transformer was re-designed by changing the mechanical configuration of the windings to sectional, side-by-side windings or "pies." This new winding configuration simplifies the implementation of the zig-zag connections and reduces voltage stress between windings. Added advantages are that it is easier to manufacture and also much easier to repair. The design reduces the major manufacturing steps by approximately 50 percent. The expected lifetime or mean-time-between-failure (MTBF) of this transformer has been increased by a calculated factor of ten.
{"title":"A High Reliability Compact Lightweight High Voltage Transformer","authors":"R. Gardenghi, R. C. Houlne, B.G. Keggins, L. E. Wilson, K.R. Maerten","doi":"10.1109/MODSYM.1994.597080","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597080","url":null,"abstract":"This paper describes the design, testing and performance of a new high voltage transformer. An existing compact lightweight high voltage transformer was re-designed to improve its reliability and maintainability. The transformer is used in a dc power supply which is nominally rated at 100 kV and 1.5 Amperes. The entire supply is located within a pressure vessel with Sulphur Hexafluoride ( S F g ) gas for insulation and cooling. The original design encompassed a delta-wye transformation with zig-zag secondaries to provide 12 pulse rectification. The windings were configured in concentric coil pairs with the small (zag) secondary mounted outside the main (zig) windings with molded-in-place silicone rubber spacers. The unit performed well except for a relatively high failure rate due primarily to insulation breakdown between the zig and the zag windings. The transformer was re-designed by changing the mechanical configuration of the windings to sectional, side-by-side windings or \"pies.\" This new winding configuration simplifies the implementation of the zig-zag connections and reduces voltage stress between windings. Added advantages are that it is easier to manufacture and also much easier to repair. The design reduces the major manufacturing steps by approximately 50 percent. The expected lifetime or mean-time-between-failure (MTBF) of this transformer has been increased by a calculated factor of ten.","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128660203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597098
T. Mehr, R. Tkotz, J. Christiansen, S. Dollinger, K. Frank, A. Gortler, U. Herleb, M. Schlaug, A. Schwandner, W. Hartmann, J. Stroh
12 % 3.1011 AIS 169 11s (FWECM) 1.69 mC 58/233 Hz Pseudospark switches are currently under development to replace conventional thyratrons in pulsed gas discharge lasers. In comparison with thyratrons, the pseudospark switch has some fimdamental advantages like a peak current of more than 100 kA [l], a current reversal capability of 100% and a rate of current rise of up to 8.1011 AIS [2]. These advantages will make the pseudospark switch an improvement over existing switch technology if lifetime of conventional thyratrons could be achieved. Lifetime of pseudospark switches is strictly correlated with erosion phenomena at the central electrode bore holes. Results of two experiments, performed to measure lifetime and erosion in sealed off pseudospark switches, will be reported.
AIS 169 11s (FWECM) 58/233 Hz伪火花开关目前正在开发中，以取代脉冲气体放电激光器中的传统闸管。与闸流管相比，伪火花开关具有峰值电流超过100 kA [l]、电流反转能力100%、电流上升速率高达8.1011 AIS等基本优势[2]。如果能达到传统闸流管的寿命，这些优点将使伪火花开关在现有开关技术的基础上得到改进。假火花开关的寿命与中心电极孔的腐蚀现象密切相关。两个实验的结果，执行测量寿命和侵蚀在封闭的假火花开关，将报告。
{"title":"Lifetime Measurements Of Pseudospark Switchs For Pulsed Gas Discharge Lasers","authors":"T. Mehr, R. Tkotz, J. Christiansen, S. Dollinger, K. Frank, A. Gortler, U. Herleb, M. Schlaug, A. Schwandner, W. Hartmann, J. Stroh","doi":"10.1109/MODSYM.1994.597098","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597098","url":null,"abstract":"12 % 3.1011 AIS 169 11s (FWECM) 1.69 mC 58/233 Hz Pseudospark switches are currently under development to replace conventional thyratrons in pulsed gas discharge lasers. In comparison with thyratrons, the pseudospark switch has some fimdamental advantages like a peak current of more than 100 kA [l], a current reversal capability of 100% and a rate of current rise of up to 8.1011 AIS [2]. These advantages will make the pseudospark switch an improvement over existing switch technology if lifetime of conventional thyratrons could be achieved. Lifetime of pseudospark switches is strictly correlated with erosion phenomena at the central electrode bore holes. Results of two experiments, performed to measure lifetime and erosion in sealed off pseudospark switches, will be reported.","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128361002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597028
W. Reass, D. Deb
Plasma Source Ion Implantation (PSII) is a materials surface modification process which can be used to improve performance characteristics of manufacturing tooling and products. Since improvements can be realized in surface hardness, reduced friction, wear, galling, and increased resistance to corrosion, PSI1 is applicable to a broad spectrum of manufactured items. In PSII, the object to be implanted is placed in a weakly ionized plasma and pulsed to a high negative voltage. The plasma ions are accelerated into the object's surface, thereby changing its' chemical and physical composition. The plasma dynamic load impedance is highly variable, dependent on implant object area, plasma density, and material composition. The modulator load impedance may be a few tens of ohms and a few thousand picofarads early in time. Late in time, the load may appear as 20,000 Ohms and 100 picofarads. The modulator system must accommodate any process changes, in addition to (frequent) initial "start-up" object arcs (from impurities). To implant the required ion densities in a minimum of time, multi-kilohertz rep-rates are often required. An evolutionary design approach was utilized to design a cost-effective and reliable modulator system with components of established performance, suitable for a manufacturing environment. This paper, in addition to presenting the anticipated modulator design required for the PSI1 application, wi l l review similar modulator topologies and determine operational lifetime characteristics. Further improvements in system electrical efficiency can also be realized with incremental design modifications to the high voltage switch tubes. Development options for upgraded switch tubes of higher efficiency will also be presented.
{"title":"Initial Design Of A 1 Megawatt Average, 150 Kilovolt Pulse Modulator For An Industrial Plasma Source Ion Implantation Processor","authors":"W. Reass, D. Deb","doi":"10.1109/MODSYM.1994.597028","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597028","url":null,"abstract":"Plasma Source Ion Implantation (PSII) is a materials surface modification process which can be used to improve performance characteristics of manufacturing tooling and products. Since improvements can be realized in surface hardness, reduced friction, wear, galling, and increased resistance to corrosion, PSI1 is applicable to a broad spectrum of manufactured items. In PSII, the object to be implanted is placed in a weakly ionized plasma and pulsed to a high negative voltage. The plasma ions are accelerated into the object's surface, thereby changing its' chemical and physical composition. The plasma dynamic load impedance is highly variable, dependent on implant object area, plasma density, and material composition. The modulator load impedance may be a few tens of ohms and a few thousand picofarads early in time. Late in time, the load may appear as 20,000 Ohms and 100 picofarads. The modulator system must accommodate any process changes, in addition to (frequent) initial \"start-up\" object arcs (from impurities). To implant the required ion densities in a minimum of time, multi-kilohertz rep-rates are often required. An evolutionary design approach was utilized to design a cost-effective and reliable modulator system with components of established performance, suitable for a manufacturing environment. This paper, in addition to presenting the anticipated modulator design required for the PSI1 application, wi l l review similar modulator topologies and determine operational lifetime characteristics. Further improvements in system electrical efficiency can also be realized with incremental design modifications to the high voltage switch tubes. Development options for upgraded switch tubes of higher efficiency will also be presented.","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133362233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597094
R. P. Knight, B. Newton, R. Sheldrake, C.R. Weatherup
EEV is a world leader in the production of Inductive Output Tubes (IOT's), which are now beginning to replace conventional klystrons in television transmitters. Unlike conventional TV klystrons, the I O T requires a crowbar to protect its carbon control grid and its cathode in the event of a fault. A bought-in IOT test equipment at EEV originally used a spark gap crowbar, but this was replaced by a thyratron crowbar when an IOT under test was destroyed because the spark gap failed to fire. The thyratron choice for this socket, which ages and tests 40kW IOT's at 28kVd.c., was a single gap glass thyratron type CX1722A/3 . This was installed in November 1991 and is still working satisfactorily after 10,000 filament and 4,200 high voltage hours and 2,600 crowbar events. Commercial transmitters require 24 hour a day, seven day a week operation. Transmitter reliability is essential and fault conditions must be dealt with by a fail-safe crowbar system. Accordingly, EEV has developed a two gap ceramic thyratron, CX2708, for use in commercial equipments. This 3" diameter thyratron is rated for 40kV d.c. hold-off, and for a fault level of 6 coulombs. All CX2708 thyratrons are tested for 24 hour hold-off at 40Kv d.c. at the maximum specified heater and reservoir voltages, and are also tested discharging 16pF from 40kV through a resistance of 23R followed by 6.4C of power supply follow-on at the minimum specified heater and reservoir voltage. These exacting tests were essential to meet the severe reliability reqirements, and are being performed on all production CX2708 thyratrons to ensure continued reliability and quality. Measurements have been made of the capabilities of the CX2708 with regard to capacitor discharge and follow-on current level and duration. These measurements show that the requirements of commercial equipments are well within the capabilities of the CX2708. A complete crowbar unit (type MA2447A) has also been developed for use with the CX2708. This unit incorporates automatic fault current triggering of the crowbar when a preset current level is exceeded. Interlocking of the grid 1 current to indicate that the crowbar is ready to fire and external triggering via optic links are additional important features. Two methods of setting the triggering level are discussed in detail with particular reference to noise immunity. Under typical operating conditions the unit will protect a 0.05mm diameter wire (47 SWG). Protection is fast with a firing delay of only 1lOns under fault conditions and 50011s via the external trigger. Under fault conditions at the full 40kV the "let through" to the fault is 2.3mC and only 0.023A2s. Many CX2708 thyratrons are now operating satisfactorily in transmitters throughout the world. The target spurious firing rate from the thyratron is less than one per year to ensure first class reliability. A d.c. hold-off test at 40kV at EEV has reached 3,500 hours without a single spurious firing and is ongoing. A further j~mp
{"title":"A High Reliability, Fail Safe, Thyratron Crowbar System For The Protection Of High Power Microwave Tubes In Television Transmitters","authors":"R. P. Knight, B. Newton, R. Sheldrake, C.R. Weatherup","doi":"10.1109/MODSYM.1994.597094","DOIUrl":"https://doi.org/10.1109/MODSYM.1994.597094","url":null,"abstract":"EEV is a world leader in the production of Inductive Output Tubes (IOT's), which are now beginning to replace conventional klystrons in television transmitters. Unlike conventional TV klystrons, the I O T requires a crowbar to protect its carbon control grid and its cathode in the event of a fault. A bought-in IOT test equipment at EEV originally used a spark gap crowbar, but this was replaced by a thyratron crowbar when an IOT under test was destroyed because the spark gap failed to fire. The thyratron choice for this socket, which ages and tests 40kW IOT's at 28kVd.c., was a single gap glass thyratron type CX1722A/3 . This was installed in November 1991 and is still working satisfactorily after 10,000 filament and 4,200 high voltage hours and 2,600 crowbar events. Commercial transmitters require 24 hour a day, seven day a week operation. Transmitter reliability is essential and fault conditions must be dealt with by a fail-safe crowbar system. Accordingly, EEV has developed a two gap ceramic thyratron, CX2708, for use in commercial equipments. This 3\" diameter thyratron is rated for 40kV d.c. hold-off, and for a fault level of 6 coulombs. All CX2708 thyratrons are tested for 24 hour hold-off at 40Kv d.c. at the maximum specified heater and reservoir voltages, and are also tested discharging 16pF from 40kV through a resistance of 23R followed by 6.4C of power supply follow-on at the minimum specified heater and reservoir voltage. These exacting tests were essential to meet the severe reliability reqirements, and are being performed on all production CX2708 thyratrons to ensure continued reliability and quality. Measurements have been made of the capabilities of the CX2708 with regard to capacitor discharge and follow-on current level and duration. These measurements show that the requirements of commercial equipments are well within the capabilities of the CX2708. A complete crowbar unit (type MA2447A) has also been developed for use with the CX2708. This unit incorporates automatic fault current triggering of the crowbar when a preset current level is exceeded. Interlocking of the grid 1 current to indicate that the crowbar is ready to fire and external triggering via optic links are additional important features. Two methods of setting the triggering level are discussed in detail with particular reference to noise immunity. Under typical operating conditions the unit will protect a 0.05mm diameter wire (47 SWG). Protection is fast with a firing delay of only 1lOns under fault conditions and 50011s via the external trigger. Under fault conditions at the full 40kV the \"let through\" to the fault is 2.3mC and only 0.023A2s. Many CX2708 thyratrons are now operating satisfactorily in transmitters throughout the world. The target spurious firing rate from the thyratron is less than one per year to ensure first class reliability. A d.c. hold-off test at 40kV at EEV has reached 3,500 hours without a single spurious firing and is ongoing. A further j~mp","PeriodicalId":330796,"journal":{"name":"Twenty-First International Power Modulator Symposium, Conference","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1994-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115680839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 1994-06-27DOI: 10.1109/MODSYM.1994.597064
B. L. Thomas, R. White, A. Auyeung, K. Harris, J. Green, R. Ness, R. Rodriguez, J. Mynk, J. Grippe
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