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the eimac 4cm2500kg is a ceramic/metal, multi- phase (water/vapor) cooled power tetrode de - signed for very high power rf service. the 4cm2500kg has a high density thoriated tungsten mesh flament mounted on water-cooled supports. pyrolytic graphite control and screen grids are used to provide stability at high dissipa - tion. the maximum anode dissipation rating is 2500 kilowatts. large diameter coaxial control grid and cathode terminals allow enhanced vhf performance. fila - ment power and flament support cooling water are supplied through connectors which allow for quick tube installation and replacement. multi-phase cooled cpi | 4cw50,000j for information on this and other cpi products, visit our website at: www.cpii.com , or contact: cpi mpp, eimac operation, 607 hansen way, palo alto, ca 94303 telephone : 1(800) 414-8823. fax : (650) 592-9988 | email : powergrid@cpii.com the values listed above represent specifed limits for the product and are subject to change. the data should be used for basic information only. formal, controlled specifcations may be obtained from cpi for use in equipment design. c ha r acte r istics 1 electrical filament: thoriated tungsten mesh voltage 15.5 v current at 15.5 volts (nominal) 640 a frequency of maximu ratings (cw) 130 mhz maximum useful frequency over 200 mhz amplifcation factor, average, grid to screen 6 direct interelectrode capacitances (grounded cathode): cin 1110 pf cout 150 pf cgp 5.5 pf direct interelectrode capacitances (grounded grid and screen) 2 cin 385 pf cout 152 pf c pk 0.07 pf cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg powe r tet r ode 1 mechanical: net weight 161 lb.; 73.0 kg gross weight 340 lbs; 154 kg operating position vertical, base down cooling water and forced air maximum overall dimensions: length 18.75 in; 47.62 cm diameter 17.03 in; 43.26 cm maximum operating temperature, envelope and ceramic/metal seals 200c available filament power connectors (not supplied with tube): filament power/water connector (2 required): eimac sk-2310 filament rf connector (1 required): eimac sk-2315 available anode cooling water connectors (not supplied with tube): note: 2 connectors are required per tube eimac sk-2322 or eimac sk-2323 4cm2500 kg
absolute maximum r atin g s : dc anode voltage 27 kilovolts dc screen voltage 2.5 kilovolts anode current # 190 amperes anode dissipation 2500 kilowatts screen dissipation 20 kilowatts grid dissipation 8.0 kilowatts r adio f r equency powe r amplifie r gr ounded gr id - drive pulsed for long pulse fusion applications or cw service (class ab or b) cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 2 4cm2500 kg typical ope r ation : anode-to-grid voltage 24 24 24 kvdc screen-to-grid 1000 1500 2000 vdc bias voltage 490 500 540 vdc anode current # 86.7 127 182 adc anode dissipation 441 728 1550 kw screen current # 5.8 7.5 4.1 adc screen dissipation 10.1 16.9 11.3 kw grid current # 10.3 10.0 6.1 adc drive power # 69.9 98.3 138.0 kw anode load impedance 145 102 74 ohms power output #* 1700 2400 3500 kw # average during the pulse * approximate employed to lift the tube and should be capable of safely supporting the full weight of the tube (up to 200 lbs with cooling water in the anode cooler) and should be operated with great care, especially when lower - ing the tube onto a resting place or into equipment. it is recommended that a thick rubber mat or similar mate - rial be used to absorb any undue shock that may occur if the tube is to be placed temporarily on a hard surface. storage C if a tube is to be stored as a spare it should be kept in its shipping crate and all water should be purged from the anode cooler and from the flament sup - ports/connectors. the anode cooler can be drained by inverting the tube. water should be purged from the in - ternal flament support structure by applying compressed air to one of the flament coolant ports and it is important to note that pressure during this process must be limited to 2 bar (29 psi). under no circumstances should one at - tempt to use an unregulated air source for this procedure. the tube should be stored with a portable vac- ion pump power supply connected to allow moni - toring the vacuum tubes vacuum properties (see section on vacion pump operation for details.) application mechanical unpacking C to insure safety of the operator per - forming the work as well as preventing damage to the tube, the following instructions should be followed: 1) open the crate by removing the lid, frst unlock- ing the toggle bolts in 8 places. 2) attach a lifting hoist to the lifting loop and raise the tube slightly with mounting brackets attached to support the weight of the tube. 3) remove 8 bolts securing the mounting brackets to the corners. 4) using the hoist, lift the tube and place on blocks or on a stand that supports its weight by the bottom of the lower corona ring. 5) remove the brackets from the tube. handling C this product contains a thoriated- tungsten flament, and although of a rugged mesh design, it is relatively fragile and a tube should be protected from shock and vibration. a lifting eye is available at the center of the anode cooler and should be used any time the tube is to be lifted for moving, etc. a lifting device such as a chain hoist may be
the original shipping crate with the shock mounts and hard - ware should be retained in a dry place for future use such as moving a tube over a considerable distance. instructions on affxing the shock mounts is included with each tube. mounting - the 4cm2500kg must be mounted vertical - ly, base down. the full weight of the tube should rest on the screen-grid contact fange at the base of the tube, and all lifting of the tube should be done with the lifting eye which is attached to the top of the anode cooling jacket. anode cooling - the anode is cooled by circulating high velocity water near the boiling point through the structure. the inlet and outlet connections are clearly marked on top of the anode cooling jacket and it is im - portant they be connected only as indicated. multiphase cooling provides effcient removal of heat from the anode and assures additional capacity for temporary overloads. tube life can be seriously compromised by the condition of the cooling water. if it becomes contaminated, deposits will form on the inside of the water jacket causing localized anode heating and eventual tube failure. to insure mini - mum electrolysis and power loss, the water resistance at 25c should always be one megohm per cubic centi - meter or higher. the relative water resistance should be periodically checked using readily available instruments. high velocity water fow is required to maintain high thermal effciency; for this reason operation at low - er anode dissipation using lower fow rates than what is listed in the table on p.3 is not recommended. cooling water must be well fltered, with effective - ness the equivalent of a 100-mesh screen, to elimi - nate any solid material and avoid the possibility of blockage of any cooling passages, as this would im - mediately affect cooling effciency and could produce localized anode overheating and failure of the tube. minimum water fow requirements for the anode are shown in the table for an outlet water tempera - ture not to exceed 100c and inlet water temperature cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 3 4cm2500 kg at 49c. system pressure should not exceed 100 psi. anode water approx. jacket dissipation flow press drop (kw) (gpm) (psi) 2500 200 87 this cooling data is applicable to steady-state or tran - sient anode dissipation. at signifcantly reduced anode dissipation a lower fow rate may be permissible but using the maximum fow rate will protect the tube from unfore - seen events that may cause surges in anode dissipation. eimac application bulletin #16, water purity re - quirements in liquid cooling systems, is available on request and contains considerable de - tail on purity requirements and maintenance systems. base cooling - the tube base requires air cooling with a minimum of 50 cfm of air at 50c maximum at sea level, di - rected toward the base seal areas from a general purpose fan. it should be noted that temperatures of the ceramic/ metal seals and the lower envelope areas are the control - ling and fnal limiting factor. temperature-sensitive paints are available for use in checking temperatures in these areas before equipment design and air-cooling require - ments are fnalized. eimac application bulletin ab-20, measuring temperature of power grid tubes, covers this subject in detail and is available on request. water cooling of the flament and screen grid supports is also required, with inlet water temperature not to ex - ceed 49c. each of the two flament connectors include both an inlet and an outlet line, with the proper connec - tor for the inlet water shown on the tube outline draw - ing. minimum fow for the f1 connector is 2.0 gpm, at an approximate pressure drop of 12 psi. minimum fow for the f2 connector is 4.0 gpm, at an approximate pres - sure drop of 50 psi. the screen grid cooling water is fed by means of 1-18 npt tapped holes shown on the tube outline drawing, with a minimum fow of 2.0 gpm required, at an approximate pressure drop of 12 psi.
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 4 all cooling must be applied before or simultaneously with the applica - tion of electrode voltages, including the filament, and should normally be maintained for several minutes after all volt - ages are removed to allow for tube cooldown. elect r ical absolute maximum ratings - values shown for each type of service are based on the absolute system and are not to be exceeded under any service conditions. these ratings are limited values outside which serviceability of the tube may be impaired. in order not to exceed absolute ratings the equipment designer has the responsibility of determining an average design value for each rating be - low the absolute value of that rating by a safety factor so that the absolute values will never by exceeded under any usual conditions of supply-voltage variation, load varia - tion, or manufacturing variation in the equipment itself. it does not necessarily follow that combinations of ab - solute maximum ratings can be attained simultaneously. high voltage - normal voltages used with this tube are deadly, and equipment must be designed properly and operating precautions followed. design all equip - ment so that no one can come in contact with high volt - ages. equipment must include safety enclosures for the high-voltage circuits and terminals, with interlock switches to open primary circuits of the power sup - ply and to discharge high voltage capacitors when ac - cess doors are opened. interlock switches must not be bypassed to allow operating with access doors open. always remember that high voltage can kill. filament operation - filament turn-on and turn- off should be programmed. filament voltage should be smoothly increased from zero to the operating level over a period of two minutes, and a motor-driven continuously variable auto-transformer (such as a variac ? or a pow - erstat ? ) is suggested. inrush current must never be al - lowed to exceed twice normal operating current. normal turnoff procedure should be a smooth decrease from the operating voltage to zero over a period of two minutes. 4cm2500 kg during periods of standby service, flament life may be increased by a small reduction in flament voltage. black heat operation (a reduction of flament voltage to 50% or less of nominal voltage) is prohibited. during standby periods, forced air cooling and water fow must be main - tained on the flament supports to ensure the ceramic/ metal seal temperature does not exceed 200c. in addi - tion, anode cooling water fow must be maintained at a rate that ensures the outlet water temperature never ex - ceeds 100c. see cautionary information regarding hot water on p.5. serious damage and personal harm can re - sult if water fow is interrupted while power is applied to the flament therefore system interlocks are necessary to remove all power to the tube if coolant fow is not present for any reason. filament voltage should be measured at the tube base, using an accurate rms-responding meter. where hum is an important system consideration, it is permissible to operate the flaments with dc rather than ac power. contact cpi microwave power prod - ucts, eimac operation application engineering for special precautions when using a dc flament supply. care should be exercised to keep any rf power out of the flament of the tube, as this can cause excessive oper - ating temperatures. both sides of the flament must be bypassed to assure monopotential operation. it should be ascertained that no resonance exists in the flament circuit which could be excited during operation. when this tube is operated at combined screen and grid dis - sipations above 10 kilowatts the flament power should be reduced to maintain proper flament temperature (i.e., resistance) and thereby assure optimum life. contact cpi microwave power products, eimac operation ap - plications engineering for specifc recommendations. this tube is designed for commercial service, with only one off/on flament cycle per day. if additional on/off cycling of flament power is anticipated it is recommended the user contact cpi microwave power products, eimac opera - tion applications engineering for additional information. vacion ? pump operation C the tube is supplied with an ion pump and magnet, permanently mounted on the flament structure at the base (stem). the primary func -
cpi | 4cw50,000j cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 5 tion of this device is to allow monitoring of the condition of the tube vacuum, as shown by an ion current meter. with an operational tube it is recommended the vac-ion pump be operated full time so tube vacuum may be moni - tored on a continuous basis. a reading of less than 10 uadc should be considered as normal, indicating excel - lent tube vacuum. in addition to other interlock circuitry it is recommended that full advantage be taken of the vacion pump readout by providing circuitry which will shut down all power to the tube in the event the readout current exceeds 50 uadc. in the event of such a shut - down, the vacion pump should be operated alone un - til vacuum recovery is indicated by a reading of 10 uadc or less, at which point the tube may again be made op - erational. if the vacuum current rises again it should be considered as indicating a circuit problem such as some tube element may be over-dissipating and outgassing. the vacion pump requires a positive voltage applied to the center pin of approx. 3000 vdc to operate properly. one source for vacion power supplies is varian, inc. varians web site www.varianinc.com has several models which may be suitable for use with the 4cm2500kg. var - ian model 9290200 (120 volt ac line) or 9290201 (220 volt ac line) appear suitable. alternatives for varian power supplies are: heatwave labs http://www.cathode.com/ and duniway stockroom http://www.duniway.com/ at the tetrode a coaxial cable is attached to the vacion pump and comes attached to the tube as delivered. this cable assy. includes a resistor that prevents the flament current from being shorted to ground. the end of the resis - tor has a solder lug that is attached using one of the small screws to the magnet assy at the vacion pump. the other end of this cable has a female receptacle (type mhv, also designated mil. ug-1016a/u or amphenol type 27075). to plug onto this receptacle a male plug type ug-932/u, also supplied with each tube, is normally used for mak - ing up an extender cable of the required length. the other end of the extender cable goes to the vacion power supply; the varian supplies require a kings plug 4cm2500 kg 1065-1 (not supplied with the 4cm2500kg). for info see: http://www.kingselectronics.com/ and cable type rg- 58a/u or belden 8259 is recommended for this connector. in the case of a tube being held as a spare, it is recom - mended the vacion pump be operated continuously if possible, otherwise it should be operated periodically to check the condition of tube vacuum and operated as long as necessary to achieve a reading of 10 uadc or lower. figure 1 shows the relationship between tube vacu - um and the ion current reading. electrode voltages, including flament voltage, should never be applied if a reading of 50 uadc or higher is obtained. in the event that poor vacuum cannot be improved by op - eration of the vacion pump the user should contact cpi microwave power products, eimac operation and review the details with an applications engineer. if the tetrode is grid-driven the cathode (and therefore the flament power supply) is generally referenced to dc ground potential, that is no bias voltage or other voltage is supplied to the flament. in this case the vacion pow - er supply may be used with no isolation and the shield and connector on the vacion cable should be grounded for reasons of electrical safety. if however the tetrode is to be used in grounded-grid (cathode-driven) con - fguration as is typical in the case of vhf, then rf drive applied to the tubes cathode/flament will also be pres - ent on the vacion cable and therefore good rf isolation must be provided to prevent rf power from fowing on this cable. the system designer must therefore incor - porate rf fltering on the vacion cable to keep rf en - ergy from passing back into the vacion power supply and its metering circuit; ferrite chokes around the cable may be suitable. the flament supply should be ground - ed as any dc voltage that is applied from the flament to ground will interfere with proper vacion operation. anode operation - the maximum anode dissipa - tion rating of 2500 kilowatts should not be exceeded even for very brief periods during setup or tuning. anode current which fows at high anode voltages with no rf, such as interpulse idling current, must be avoided
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 6 by such means as reducing screen voltage or increas - ing control grid bias during the idling period. current fowing at high anode voltage causes signifcant x-ray generation. at typical class ab idling currents x-ray intensity is very high and represents a signifcant po - tential hazard to personnel in the vicinity of the tetrode. see x-radiation hazard on p.7 for more information. operation with low values of anode current under some conditions of high instantaneous anode voltage (such as regulator service or lower power and low impedance tuning conditions) can, as a result of the screen and grid voltages chosen, lead to anode damage and subse - quent failure from spot heating as a result of focusing effects in the tube. if operation under such conditions is necessary cpi microwave power products, eimac operations application engineering should be contact - ed for assistance in selection of operating parameters. grid operation - the maximum grid dissipation is 8 kilowatts and protective measures should be taken to insure that this rating is not exceeded. grid dissipation is approximately equal to the product of dc grid current and peak positive grid voltage. a protective spark gap device should be connected between the control grid and the cathode to guard against excessive voltage. under some operating conditions the control grid may ex - hibit a negative resistance characteristic. this may oc - cur with high screen voltage when increasing the drive power results in a net decrease in grid current. large values of negative grid current can cause the amplifer to become regenerative. the driver stage must be designed to tolerate this condition. one technique is to swamp the driver so that the change in load, due to secondary grid emission, is a small percentage of the total driver load. screen operation - the maximum screen grid dissi - pation is 20 kilowatts. with no ac applied to the screen grid, dissipation is simply the product of dc screen volt - age and the dc screen current. rf heating of the screen must be measured in calculating total screen dissipa - tion at frequencies greater than 60 mhz. anode voltage, anode loading, or bias voltage must never be removed while flament and screen voltages are present, since 4cm2500 kg screen dissipation ratings will be exceeded. suitable protective circuitry must be provided to remove screen power in case of a fault condition. a protective spark- gap device should be connected between screen grid and the cathode to guard against excessive voltage. operation of the 4cm2500kg at its maximum vhf power capabilities will result in suffcient rf current screen grid heating to cause signifcant reverse screen grid cur - rent due to thermionic emission. such operation will not cause tube damage if proper procedures are followed; however, the screen grid circuit must be designed with this characteristic in mind so that the correct operating voltage will be maintained on the screen under all con - ditions. dangerously high anode current may fow if the screen power supply exhibits a rising voltage character - istic with negative screen current. a current path from the screen to cathode must be provided by a bleeder re - sistor to absorb the reverse current without allowing the screen grid voltage to rise excessively. a series-regulated power supply can only be used when an adequate bleed - er resistor is provided; a shunt-regulated power supply is also very effective towards meeting this requirement. pulse operation - the thermal time constants of the internal tube elements vary from a few milliseconds in the case of the grids to about 200 milliseconds for the an - ode. in many applications the meaning of duty as applied to a pulse chain is lost because the interpulse period is very long. for pulse lengths greater than 10 milliseconds, where the interpulse period is more than 10 times the pulse duration, the element dissipations and required cooling are governed by the watt-seconds during the pulse. pro - vided the watt-seconds are less than the listed maximum dissipation rating and suffcient cooling is supplied, tube life will not be compromised. to maintain high cooling ef - fciency the anode water fow must be suffcient to insure turbulent fow. see flow recommendation on page 3. fault protection - in addition to the normal anode over-current interlock and coolant interlock, the tube must be protected from internal damage caused by any arc which may occur. a protective resistance should always be connected in series with the grid and anode to help ab - sorb power supply stored energy if an arc should occur.
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 7 an electronic crowbar, which will discharge power sup - ply capacitors in a few microseconds after the start of an arc, is required. the protection criteria for each supply is to short each electrode to ground, one at a time, through a vacuum relay switch and a 6-inch length of #30 awg cop - per wire. the wire will remain intact if criteria are met. as noted under grid operation and screen opera - tion, a protective spark gap should be connected from the control grid to ground and from the screen grid to ground. cpi application bulletin #17 titled fault protection contains considerable detail and is available on request. load vswr - the load vswr should be monitored and the detected signal used to operate the interlock system to remove anode voltage within 20 milliseconds after a fault occurs. in the case of high stored energy in the load system, care must be taken to avoid excessive return energy from damaging the tube and associated circuit components. mode suppression considerations - high- performance high-power gridded tubes including the 4cm2500kg have natural circular resonance modes of oscillation which must be suppressed during initial test - ing of equipment. the short compact stem structure of eimac tubes provides easy access for mode suppres - sion techniques. it is recommended that short pulse test - ing be used to detect this phenomenon and to evaluate the effectiveness of the suppression techniques used. the 4cm2500kg has been found to exhibit circular mode oscillations in both l band and s band frequency ranges. these modes must be suppressed externally to prevent damage to the tube and to provide stable opera - tion in the intended application. one technique which has worked to suppress these circular modes is using ferrite tiles. the ferrite tiles can be cemented (using general electric rtv-102 or equivalent) to the conical and fat surfaces of the screen deck at the base of the tube. the size of the tiles can be up to approximately one inch square or rectangular and 0.1 to 0.3 inch thick. the ferrite must have properties such that it is not lossy at the fundamental frequency otherwise exces - 4cm2500 kg sive heating of the ferrite may occur. one source for the ferrite material is: national magnetics group, inc. in bethlehem, pa, usa. for further information con - tact cpi microwave power products, eimac operation. in some instances, a compromise between tube ef - fciency and anode load impedance by way of modi - fying the output matching tuning and loading will prevent circular mode oscillations from occurring while a tube is delivering peak output. adjustment of both the screen voltage and grid bias voltage while testing for circular mode oscillations is also predi - cated and fne adjustments in both parameters will often reduce or eliminate circular mode oscillations. x-radiation hazard - high-vacuum tubes operating at voltages higher than 15 kilovolts produce progres - sively more dangerous x-ray radiation as the voltage is increased. this tube, operating at its rated voltages and currents, is a potential x-ray source. only limited shield - ing is afforded by the tube envelope. moreover, the x- radiation level may increase signifcantly with tube aging and gradual deterioration, due to leakage paths or emis - sion characteristics as they are affected by the high volt - age. x-ray shielding may be required on all sides of tubes operating at these voltages to provide adequate protec - tion throughout the life of the tube. periodic checks on the x-ray level should be made, and the tube should never be operated without required shielding in place. if there is any question as to the need for or the adequacy of shielding, an expert in this feld should be contacted to perform an x-ray survey. in cases where shielding has been found to be required, operation of equipment with interlock switches cheated and cabinet doors open in order to be better able to locate an equip - ment malfunction can result in serious x-ray exposure. radio-frequency radiation - avoid exposure to strong rf felds even at relatively low frequency. absorption of rf energy by human tissue is dependent on frequency. osha (occupational safety and health administration) recommends that prolonged exposure to rf radiation should be limited to 10 milliwatts per square centimeter.
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 8 interelectrode capacitance - the actual inter - nal interelectrode capacitance of a tube is infuenced by many variables in most applications, such as stray capacitance to the chassis from the tube terminals and associated wiring. to control the actual capacitance values within the tube, as the key component involved, the industry and military services use a standard test procedure described in electronic industries associa - tion standard rs-191. the test is performed on a cold tube, and in the case of the 4cm2500kg, with no special shielding. other factors being equal, controlling inter - nal tube capacitance in this way normally assures good interchangeability of tubes over a period of time. the capacitance values shown in the test specifcation or tech - nical data are taken in accordance with standard rs-191. hot surfaces C surfaces of tubes can reach temperatures of several hundred c and cause serious burns if touched for several minutes after all power is removed. material compliance - this product and package conforms to the conditions and limitations specifed in 49cfr 173.424 for radioactive material, excepted package-instruments or articles, un2910. in addition, this product and package contains no beryllium oxide (beo). high voltage C normal operating voltages can be deadly. remember the high voltage can kill. low-voltage high-current circuits - personal jewelry, such as rings, should not be worn when working with flament contacts or connectors as a short circuit can produce very high current and melting, resulting in severe burns. rf radiation C exposure to strong rf felds should be avoided, even at relatively low frequencies. cardiac pacemakers may be affected. operating hazards proper use and safe operating practices with respect to power tubes are the responsibility of equipment manufacturers and users of such tubes. all persons who work with or are exposed to power tubes or equipment which utilizes such tubes must take precautions to protect themselves against possible serious bodily injury. do not be careless around such products. operation of this tube may involve the following hazards, any one of which, in the absence of safe operating practices and precau - tions, could result in serious harm to personnel. 4cm2500 kg the equipment designer is cautioned to make allow - ance for the capacitance values, including tube-to-tube variation and strays, which will exist in any normal ap - plication. measurements should be taken with mount - ing which represent approximate fnal layout if capacitance values are highly signifcant in the design. special applications - when it is desired to op - erate this tube under conditions different from those listed here, write to cpi microwave power prod - ucts, eimac operation attn: applications engi - neering; 607 hansen way, palo alto, ca 94304 usa.
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 4cm2500 kg
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg
cpi | multi - phase cooled powe r tet r ode 4 cm 2500kg 4cm2500 kg

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