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GRID-CONTROLLED P&'ER TDBES IN PARTICI&ACCEIERA?~ APPLICATIONS
PT. V. Hoover Radio Corporation of America Electronic Components and Devices Lancaster, Pennsylvania
Summary Shielded-Grid Triodes
Tvpical illustrative examples are cited The shielded-grid triode, shown in Fig. 1, for the use of grid-controlled power tubes has been employed in particle-accelerator in the various classes of particle acceler- service for more than a decade, dating from ators, e.p., cyclotrons, synchrocyclotrons, the beginnings of the Livermore LINACS (e.g., proton synchrotrons, electron synchrotrons, A-La). The original prototype sample of a and linear accelerators, A state-of-the- shielded-grid triode has provided the rf art review of triode and tetrcde power-tube power to the Derkeley Bevatron2 for the past technology is nresented, together with some eleven years and has operated for more than anparent trends in the design and develop- bh,OOO hours. ment of new tubes. The use of triodes and Shielded-grid triodes, described earlier tetrodes with integral cavity-resonators in the literaturej, are capable of producing enhances the feasibility of their use at continuous power (cw) up to 700 kilowatts and increasingly higher freauencies and/or power pulsed peak power up to 2 megawatts. The levels. In addition to their use as radio- single-ended version of the shielded-grid freouency generators in
providing rf power for the Oak Ridge tube type is intended for operation at high Isochronou cyc1otrors. The Berkeley and peak pulse power and more modest average power, Yale HILAC F (Heavy Ion Linear Accelerator) the tube is equipped with filament strands machines are powered at 70 megacycles by five containing a matrix-oxide emitter; the filament shielded-grid triodes operatin& at pulse du- heating power is then only 2.7 kilowatts (1.5 rations of 2.5 milliseconds. Four shielded- volts at 1800 amperes). prid triodes have operated for more than Fig. L shows a cross-sectional sketch of 20,000 hours in HILAC machines and one tube triode units for use in uhf tubes. Integral has operated for nearly 30,000 hours. Pulsed wire-support fins extend from the control-grid rf power for the Los Alamos PHERMEX7electron cylinder on both sides of the directly-heated accelerator has been supplied at 50 megacycles filament strand. Active 0.0033-inch-diameter by six shielded-grid triodes. The PHERMEX tungsten wires are wound laterally in grooves machine has been in operation for two years across the fins in a circumferential direction without a failure in the power-amplifier tubes. on the outside diameter of the grid cylinder at a ptch of 72 turns per inch; the wires are then Super-Power UHF Triodes covered with copper by a firm rolling operation. This construction provides a short thermal- The 205& super-power triode shown in conduction path for the flow of grid heat to Fig. 2 is believed to be the most powerful the fluid-cooled, copoer grid-cylinder, and triode in the world. It is capable of effectively overcorrr,s the problems of excessive producing at least 10 megawatts of pulse power grid temperature sometimes encountered in and can operate at frequencies up to 600 mega- triodes of classical design. The possibilities cycles. It has generated 450 kilowatts of of primary grid emission are thus minimized. continuous power at hs0 megacycles, and is Grid-wire-to-filament-strand spacing is 0.015 probably capable of considerably higher power inch. Thorough fluid cooling and individual at uhf - possibly in excess of 1000 kilowatts. pantographic suspension of the filament strands At lower freouencies, technical projections provide'a thermally stable structure. Grid- indicate that this tube should be capable of anode spacing is 0.29 inch. Intense-cooling producing about 2300 kilowatts of continuous technioues are applied to the copper anode power output. When operated as a grounded- structure for the purpose of providing high grid (cathode-driven) uhf amplifier8, this anode-dissipation capability. triode has a power gain of 13 db and a plate- The first application of the uhf super- conversion efficiency of 50 per cent. power triode in particle accelerators has been k shown in Fig. 2, the tube has a in operation for several years at Argonne double ended-configuration3, i.e., the vacuum National Laboratories. A single triode pro- envelope is desiened so that the tube is vides all of the rf power necessary or the positioned at the middle of a half-wave cir- operation of a SO-Nev LINAC Injector $ to the cuit when it is operating in the fundamental- Argonne Zero-Gradient Synchrotron (ZGS). The order circuit mode. The anode electrode at krgonne radio-freouency system shown in Fig. 5 +,he center of the tube is water-cooled by a was built by Continental Electronics. The flow of 150 eallons per minute. Ceramic cylindrical vessel in the foreground of Fie. 5 bushings on either side of the anode insulate contains the super-power triode and associated it from the grid-flange terminals at each end radio-freouency circuitry, together with of the tube (two grid-terminal connections coupling circuits to a rectangular waveguide are necessary for double-ended circuitry). which conducts the power to the LINAC tank The ceranic-to-metal vacuum-seals are of the visible in the background of the photograph. radial-compression type described previously. This eauipment operates at a frequency of 200 This giant t.riode contains a total of 90 megacycles with SOO-microsecond pulses, and injividual units combined in a common vacuum has been tested at peak power output in excess envelope. Fig. 3 shows the grid-cathode of 5 megawatts. The initial sample of the mount assembly with its plurality of in- super-vower triode has operated in the Argonne dividual triodes arrayed on a 6.6-inch-diame- system: for more than 5500 hours over a period ter cylinder; the active-region length of of four years. Circuitry to operate a super- each triode is IL inches. Cathode construction power tr'iode is currently being procured by is of the individual directly-heated fila- Brookhaven National Laboratories for use in mentary type. Two different types of emitters conjunction with the LINK Injector to the are ootional, depending on the specific servile Alternating-Gradient Synchrotron (AGS). in which a particular tube type is to be A single super-power uhf triode is also employed. Thoriated-tungsten filament strands employed to supply radio-frequency power are utilized in tube types intended for the Cambridge Electron Accelerator (CEA) 18" services reauirinfr high average power or long- at Karvard&IT. The major portion of the pulse, high-duty-factor operation. Vhen eau+- radio-freauency equipment, shown in Fig. 6, ped with thoriated-tungsten filament+ the tube was built by the WA Equipment Division. The requires a heating power of about 30 kilowatts rf driver amplifier, employing a tetrode, is (h.2 volts at 7200 amperes). If a oarticular shown in the right side of the photograph. ‘78 EXE TRANSACTIONS ONNUCLEAR SCIENCE JUX?
The super-power tricde is housed in the triodes and tetrodes with vacuum-contained cylindrical cavity-resonator on the left atop class a devices designated as a rectangular wavegl.ide which conducts the rf to differentiate them from power to the accelerator system. This equip- classical tubes. ment onerates as a linear anolifier at h7h megacycles and produces 8-millisecond saw Super-Power Triode Coaxitron for b25-MC Service tooth shaped uulses with peak power in excess of LOO kilowatts and average power in the order Fig. 7 is a photograph of the first RCA of 100 kilowatts. The two-stage rf amplifier Super-Power Coaxitron, nominally capable of operates from a common ILL-kilovolt dc power producing 5 megawatts of peak power without supuly and provides a paJer gain of about 28db. tuning over a frequency range of 10 per cent The original sample super-power triode has centered at h2.5 megacycles. The device has operated in the CEA equipment for nearly 10,000 been tested to peak power of 9 megawatts with hours over a period of four years. Two-stage a plate potential of 32 kilovolts. Power gain tetrode-triode equipment has also been supplied is in the range of 13 to 15 db, and plate- to the naresbury-Liverpool Electron Acceler- conversion efficiency of 54 per cent has been ator currently under construction in Great measured. RF driving power is applied through Britain. a coaxial line to the base of the tube. Output power is delivered through a large coaxial Gridded Tubes with Integral RF Cavities...Coaxwiicrcrs ceramic window atop the tube. The ceramic window is inserted transversely into a wave- Grid-controlled tubes have been operated guide to conduct output peer to the load. almost exclusively in conjunction with ex- Cooling water and plate potential are applied ternal rf resonators. This practice has per- to appendages on the under-side of the tube. mitted a universality of application in This particular Coaxitron employs 96 indi- utilizing a particular tube type over a range vi&altriode units in an arrangement similar of frequencies, but it has also placed grid- to that shown in Figs. 3 and h. ded tubes at a disadvantage in the following respects: Super-Power Triode Coaxitron for 8054~ Service
(a) An rf resonator must be designed Fig. 8 is a photograph of a Super-Power and built for a specific appli- Triode Coaxitron designed for service at 805 cation before a particular tube megacycles. This tube, a frequency-scaled is useful. version of the Coaxitron described above, is intended to produce 1.25 megwatts of peak lb) rhe use of external rf resonators power (75 kilowatts of average power) in has needlessly restricted the upper- pulsed service with 2000-microsecond pulses. frequency capabilities of gridded Fig. 9 shows the Coaxitron installed in test- tubes as a consequence of circuit evaluation equipment; driving power is sup- losses, spurious modes, parasitic plied by a coaxial line at the base of the circuits, voltage-insulation tube, and output power is delivered by a problems, possible difficulties with waveguide connected atop the tube. circuit contacts, and the like. The 805 megacycle Coaxitron employs b8 unit triodes, generically similar to those (cl Circuits external to the vacuum shown in Figs. 3 and h. Thoriated-tungsten envelope require pressurization at filamentary cathode strands are heated with the highest power levels in order 8.75 kilowatts of power. Power gain of the to obviate environmental problems tube is 12 dh, and a plate-conversion ef- with dust, humidit and voltage ficiency of L2 per cent has been measured at a oulsed olate voltage of 35 kilovolts. breakdown. 1 Peak power output up to 1.h megawatts has It has been annarent for a number of years been produced. A Ccaxitron of this type that these disadvantages could be overcome should be capable of producins about 300 by the design of grid-controlled tubes in kilowatts of continuous paJer (Cw) at a which the electronics systems and rf-cavity plate voltage of 20 kilovolts. It is believ- resonators would he contained in a common ed that a variant design of the tube will be vacuum-vessel, as is the practice in virtual& capable of producing 2.5 megawatts of peak all nicrowave-tyoe power generators. Pio- power at 1 percent duty-factor while produc- neering continuously-pumped triodes and tet- ing pulses of 2SO-microsecond duration. rodes of this generic ty-oe have been used at Prototype samples of the 805 megacycle 200 mepacycles as super-power rf generators Coaxitron have been delivered to Los Alamos for t e University of Minnesotal' and Har- Scientific Laboratory for evaluation in con- well 18 LINACS. Fore recently, RCA has been nection with proposed LINAC applications. engaged in the development of sealed-off Additional samples are Currently being built for Prookhaven National Laboratory. 1965 HOOVER: GRIE-CONTROLLED POWERllJBES INPARTICLE-A CELERATOR AF'PLICATIONS 79
Advantages of Coaxitrons It is apparent that these advantages will permit Coaxitrons to establish new standards of re- In addition to the well-known time- liability, life, and over-all performance as proven advantages of grid-controlled tubes, generators of rf power. it is evident that the Coaxitron concept offers the following advantages: Grid-Controlled Tubes for Driver-AmplifierSq?ss (a) The capability and advantages of Contemporary super-power vhf and uhf gridded electronics have been ex- triode stages operate with power gains in the tended by the Coaxitron concept in range of 12 to 17 db, with gain being freouency- terms of both power and frequency. dependent as a consequence of increased circuit losses at the higher frequencies. Thus, from (b) Circuit efficiency is improved con- the standpoint of power gain, the grounded-grid siderably at the higher frequencies, triode super-power amplifier is at a disadvan- and circuits can be designed for tage in comparison with velocity-modulated optimum performance with fewer re- devices, e.g., multi-cavity klystrons and strictions. traveling-wave tubes. The following para- praohs describe high-gain tetrodes and related (cl Location of the rf-cavity circuits techniques which provide enhanced gain per- within the vacuum envelope of the formance in driver-amplifier stages. Coaxitron provides superior voltage hold-off capabilities. Vacuum in- High-Gain lJHF Tetrode sulation eliminates the need for circuit pressurization, pressure vessels Hany years of experience with beam power and cavity-circuit maintenance. tubes like the types 616 and 807 have proved T&en sepatie insulators are used that the aligned-wire geometry of the tetrode for the rf fields and the dc-supply electron gun is capable of providing high voltages, Coaxitrons can be de- power gain when tubes are operated as grounded- signed to operate at considerably cathode (grid-driven) amplifiers. The ex- higher voltapes before difficulties tension of this gun design for use at higher are encountered with voltage- voltages, higher current densities, and ultra- pradient problems. high frequencies was accomplished more than a decade ago in a high-gain tetrode capable of !d) The Coaxitron eliminates tuning and producting 5 kilowatts of power for uhf loading adjustments and eliminates television Ii . Since that time, variants of potentially troublesome sliding the tube have been designed for a variety of contacts in the resonant circuits. radar pulse transmitters and increasingly These advantages reduce set-up tine, higher continuous-power (cw) capability. One down time for tuhe changes, and of these tetrodes has operated for more than operator-skill reouirements. Factory- ho,000 hours in a uhf TV transmitter. tuned, tamper-proof circuits in then- A typical high-gain uhf tetrode is shown selves will eliminate a factor which in Fig. 10. Forty individual tetrode electron- has been a major contributory cause gun units have been arrayed circumferentially to field-failures in grid-controlled in a common envelope. Erectly-heated, panto- tubes. graphically-suspended filamentary cathodes are employed. Depending on the type of service (e) For a given power capability, the intended, the tube is equipped with either compact integral-circuit Coaxitron thoriated-tungsten or matrix-oxide cathodes. oackage simplifies handling, in- Filament, control-grid, and screen-grid support stallation, storage, and shipment. structures are water-cooled to enhance thermal and mechanical stability of the structure. The (f) Because :oaxitrons can be designed anode, atop the.tube in Fig. 10, is intensively to.operate in fundamental-order water-cooled and has demonstrated a capability circuit modes, there is a very of dissipating more than 100 kilowatts of significant reduction in the number continuous power. of oarasitic or spurious circuit \&hen the classical tetrode electron gun modes which can cause tube and cir- was adapted for uhf use, careful design con- cuit malfunction. The use of sideration was given to the provision of fundamental-order circuit modes very-low-inductance leads and the isolation of minimizes electrical stored energy input-circuit from output-circuit displacement in the circuits and thereby opti- currents. Internal screen-grid bypass ca- mizes broad-band amplifier performance. pacitors are used, and the mechanical 80 IEEETRANSACI'IONS ON NUCLEAR SCIENCE JUIX?
configuration of the tube is such that it can phase-shift of only h.9 degrees was measured only be operated in the high-gain grounded- at 1365 megacycles when all supply voltages cathode (grid-driven) node of amplifier were varied by 10 per cent and rf drive power service. Goaxial circuit connections are was simultaneously varied by 1 db. It is provided on top of the tube. Filament ter- now quite practical to design a "totem-pole" minals, screen-grid terminal, and a coaxial amplifier for use in conjunction with the control-grid terminal are placed on the under- high-gain uhf tetrode shown in Fig. 10, thereby side of the tube. Brazed ceramic-to-metal providing very compact driver stages with seals are used. excellent rf phase stability. At low freauencies, the tube shown in Fig. 10 has produced 125 kilowatts of con- Gridded Tubes as Hard-Tube Modulators &Regulators tinuous power (cw) at a plate-conversion efficiency of 80 per cent and a power gain Triodes and tetrodes have been used for of 33 db, requiring a driving power of only more than two decades as hard-tube modulators 5;s watts. Thus, transistorized amplifiers in pulsing radar transmitters 16. As the need can drive the tube at lower frequencies. At for more precise control of particle acceler- 1139 megacycles the high-gain tetrode has ators has developed, machine engineers have produced 56 kilowatts of continuous power begun to employ triodes and tetrodes as pulse with a plate-conversion efficiency of 58 per modulators and regulators of supply voltages cent at a power gain of 19 db, and it is to rf generators. Thus, a triode hard-tube helieved to be capable of significantly modulator and regulator system is used to higher power. Variant designs are capable of supply plate pulses to the rf-generator tube producing 2 megawatts of short-pulse power, (shown in Fig2 2) used in the Areonne National e.g., at L251 megacycles with a plate-con- Labs InjectorY to the Zero-Gradient-Synchrotron version efficiency of $ per cent and a power (ZGS). More recently, Rheaumel7 has reported gain of 20 db. The uhf tetrodes can be used on a hard-tube modulator and regulator system for applications at frequencies up to 950 being procured for the rf system employed in megacycles. A typical circuit in which a the LINAC injector to the Brookhaven National uhf tetrode drives a super-power triode at Labs Alternating-Gradient-Synchrotron (AGS). L76 megacycles is shown at the right-hand The advantages of hard-tube modulator systems side of Fig. 6. for particle-accelerator service include the following: "Totem-Pole" Amplifier CircYitS (a) Rapid means for regulation in the Driver-amplifier stages employing grid- face of variations in system parane- controlled tubes have frequently occupied ters, inordinate space and have been unduly com- plicated in both mechanical and electrical (b) Good response against transients, details. nuring the past year, RCA engineers have been engaged in the development of SO- (cl Flexibility in varying pulse duration called "totem-oole" amplifier circuits which and repetition rates, are very compact and simple in construction, ~~~c~f~~~~p~~~~~~~~~~~l~provenents in (d) Excellent "first-line defense" in fault-protection of rf power amplifiers, Fig. 11 is a photograph of a "totem-pole" amplifier. lt comprises a six-stage cascade (e) Favorable pulse-rise and pulse-fall of triodes and tetrodes capable of producing times, a neak power output of 5 kilowatts at 1300 megacycles with a minimum gain of 50 db (f-1 Low internal noise, across an untuned bandwidth (to 1-db points) of 10 per cent. The "totem-pole" amplifier is (9) Long-life service capability, even only 2L inches long. The amplifier obviously when switching high average power derives its name frcRn the manner in which the in long-pulse applications, individual stages are stacked. Coaxial resonators are arranged so that there is (h) (Capability of operating into widely commonality between the output resonator of varying loads with modest pulse one stage and the input resonator of the distortion, follol,7ing stage; this arrangement eliminates the need for coupling cables and kindred (i) Eapability of producing higher pulse complexities. The amplifier could be short- voltapes without the use of pulse ened physically Sn applications requiring transformers. less bandwidth. The rf phase stability of the "totem-pole" amplifier is outstanding. A Fig. 12 shows a super-power hard-tube 1965 HOOVER: GRID-CONTROILEDKMERl'UBES IN PARTICLE-AWELERAmR APPLICATI~S 81
Linearity. Grid-controlled tubes modulator capable of producing 21 megawatts (67) . of peak power (1200 kilowatts of average operate simply and efficiently as power). Pulses of 2000-microsecond duration linear amplifiers. are produced at 35 kilovolts and currents up to 600 amperes. This particular modulator (h) Life. Grid-controlled tubes have emplqys a parallel pair of shielded triodes established an excellent record of (shown in Fig. 1). Tube drop is in the order life and reliability over the gamut of 3 kilovolts. of applications required in particle- accelerator service. Advantages of Grid-Controlled Tubes for Particle-Accelerator Applications (i) Low harmonic-frequency output. Grid- controlled tubes can operate with In summary, the use of grid-controlled comparatively low harmonic-frequency tubes provides the following advantages in output. particle-accelerator applications:
(a) Excellent rf phase stability. Bibliographical References
(b) Stable operation with load mismatch. 1. W. N. Parker and M. V. Hoover, "Gas Tubes Grid-controlled tubes can operate Protect High-Power Transmitters" E- without isolators under conditions of lectronics, January, 1956, V. 20 z 1Jlh. severe load mismatch. One of the most severe variable-load situations is 2. C. N. Winningstad, "Generating R-F Energy encountered in connection with LINACS for 6-BEV Pevatron", Electronics, Feb. 1955, operating in the "standing-wave" mode. v. 28, No. 2, p. 16lr. In this case, the load presented to the f Rower amplifier by the LINAC 3. M. V. Hoover, "Advances in the Techniques tank F swings from nearly zero at the and Applications of Very-High-Power Grid- beginning of the pulse to an approximate Controlled Tubes", British Proc. I.E., match as the tank gradient is establish- V. 105, Part B. Suppl. No. 10, 1958. ed. Another load transient appears when Paper presented at the InternationlCon- the beam is injected into the LINAC. vention on Microwave Valves in London on The use of hard-tube modulators facili- May 20, 1958. tates rapid corrective control of the rf generator output in the face of load h. B. H. Smith, "RF System of the Berkeley variations. e&Inch Cyclotron", Lawrence Radiation Laboratory Report No. UP&-10021, April (cl Freedom from the requirements of 2, 1962. focusing magnets. 5. F. M. Russell, II Strong Focusing Cyclotron (d) Reduction of insulation requirements in with separated Orbits"'; Oak Ridge equipment and cables as a result of National Laboratory Report, ORNL $31, 1963. low operating voltages. The need for oil tanks and pot-heads is obviated. 6. E. L. Hubbard et al. "Heaw-Ion Linear Even when grid-controlled tubes are Accelerator", Rev. of Sci.- Instruments, high-level pulsed, the voltapes required v. 32, No. 6, pp. 621~634, .June, 19t,l. are usually sufficiently low to oermit pulsing without the use of pulse trans- 7. D. Venable, t'PHERMEX", Physics Today, formers. Dec., 19611, v. 17, No. 12, p. 19.
!e) Freedom from x-rays. 8. E. E. Fpitzer, "Grounded-Grid Power Amplifiers", Electronics, April, 19h6, !f) Compactness. The compactness of grid- V. 19, No. b, p. 136. controlled tubes simplifies handling, installation, storaee, and shipment. 9. R. Perry, "The ZGS Injector", Hinutes of Compactness can be an important advan-@ the Conference on Linear Accelerator for in certain particle-accelerator instal- High Energies held at Frookhaven National lations in which low ceilings are used Laboratory August 20-Z&, 1962, p. 7. for reasons of economy in tunnel con- struction. 82 IEEETRANSACI?ONS ONNUCLEAR SCIENCE
P. V. Livdahl, "ZGS Injector Linac", i%nutes of the Conference on Proton Linear Accelerators held at Yale Uni- versity, October 21-25, 1963, p. 231.
F. 8. Livdahl, ltOperational Experience with the ZGS Injector", Paper presented at Iiubna (Russia) Conference in 1963.
10. M. S. Livingston and W. A. Shurcliff, "The Cambridge Electron Accelerator", Science, October 20, 1961, V. 13t, NO. 3~86, p. 1186.
11. 2. R. Tucker et al. "The Resnatron as a 200 MC Power Amplifier", Proc. IRE, V. LC, p. lh83, August, 1958.
12. K. Patchelor, "The Proton Linear Accelerator of the Rutherford L'aboratory", Minutes of the Conference on Linear Accelerators for High Energies held at Brookhaven National Laboratory, August 20-2L, 1962, p. 19.
13. F. S. Keith, Ff. N. Parker and G. L. Rintz, "The Coaxitron . ..A High-Power Froad-Rand, Integral-Cavity UHF Amnlifier", Paper presented, at AIDE Winter General Meeting in New York City, January 28, 1962.
"RCA Super-Power Coaxitrons....A New Concept in Packaged Broad-Band Amplifiers" RCA Publication No. ~~-285. a. W. P. Pennett, "A Beam Power Tube for UHF Service", RCA Review, V. 16, 1955, p. 321. 15. R. L. Bailey, "A Broadband, High-Gain, Power Amplifier for Phased Arrays Using Phase-Stable &ridded Tubes", Paper to be presented at IEEE Convention In New York City on March 2c, 1965.
16 . G. M. Glasoe and J. V. Lebacqz, "Pulse Generators", Me-Graw Hill, 19h8.
17. R. H. Rheaume, "Hard-Tube Modulator for the AGS Linac RF Fower Amplifier", Proc. of the Eighth Symposium on Hydrogen Thyratrons and Modulators held at Fort Monmoutb on May 12-lh, 196l1, p. 288. 1965 HOOVER: CXtD-CONTROLLED POWERTUBES IN PARTICLE-ACCELEFATOR APPLICATIONS 83
LIDUID COOLING APPLIED HERE COPPER ANOOE
CYLINDER U. \ THORIATED-TUNGSTEN GRID LIOUIO COOLING FILAMENTARY CATHODE APPLIED HERE Fig. 3. Grid-Cathode Assembly for Super-Power Fig. 4. Cross-section of Triode Unita for SUlper UHF Triode. Power Tubes.
Fig. 5. Power-Amplifier Stage for Argonne Fig. 6. The High-Powtv ?U Generator for the National Labs. LINAC. Cambridge Electron Acceierator. 84 IEEE TRANSACTIONSON NLKLE4RSCIENCE June
Fig. 7. A !&Megawatt UHF Triode Coaxltron. Fig. 8. An 805Megacycle Triode Coaxitron for Particle-Accelerator Service.
Fig. 9. An 80!%Megacycle Triode Coaxitron Fig. 10. High-Gain UHF Tetrode. in Test Cubicle. 1965 HOOVER: CXCD-CONTROLLEDPOWER TUBES IN PARTICLE-ACCELERATORAPPLICATIONS 85
Fig. 11. A New High-Gain "Totem-Pole" Amplifier UtilFaing Triodes and Tetrodes.
Fig. 12. A Typcial Super-Power Hard-Tube Modulator Employing Triodes.