TFTR NEUTRAL-BEAV 'EST FACILITY*
'i. V. Turitzln, =>. A. liewiran Princeton University Plasma Physics Laboratory P.O. Sox 451 P-*M:ceton, NJ 035^4
"Summary
"FTP 'Jeut-a1. 5eam System will have thirteen 4is- arge ion sources, ?ac*i ^ith its own power supply, elve or tne-.s .vi1" 3e utilized for supplemental ating }f *_ne "'•T3 tokamak plasma, wnile the thir- -'•- A1'1' -,e y-d'cared to 3n of-machine test cnamter r :c:,rre :eve opTienx ind/or conditioning. A test '.'•:' i; :on for jne source was set -jp using prototype riDTe"1: tO s:„v°r and :orrect jossiole deficlen- fS, ana to operly coorcinate the equipment. This .*. facw it. ear-t^ents the first opportunity for •e-o! ir-! •jr11. 'ntegrated system of hardware supplied by r •? 'e /*•rd ( each of whom desiqned and built hts urgent to ormance specifications. For the . *, 3 ' ' 3 t:e n coordination of the different portions FIG. ? OUTDOOR fARD e -'za'. i/srejr, particular attention was given r-.snnei safety and safe equipment operation. The Swi t: h^ear, /oi tage Controller, . r^rsforrre'- "ri\ r-aoer discusses various system components. Rectifier, Acce' Dummy L::ad and the auxiliary Din sec c-aracteristics, interconnection and control. load iuost^ti T *.'•?. "seated in t^re outdoor /ar'- Due :s of ;r-.e '•eccrt'. - initiated ".est anase *i' : be to the ^i'jlTg *a' . materia! , ' t ^as necessary to r n f: ted at a '.ater -late. erec t a ~ - .tt$ i 1 jd "acert tc t "e t-^as ^T met-recti er Figure 2 ;hows tne outdoor jar The remainder of tne equipment is housed indoor*;. r-^S Lay The Surge rioom, Cooling hater Skid, High Voltage Enclosure, ?nd Target Chamber are located i't ? lit "n« 'leutral Beam Test Facility consists of dri area. The Modulator-Regulato- is on the main "' ir . ..•,:door suDstation yard and an indoor installation. An : The Power Distribution Center, Filament Lr.7 / ' *•---» ••/ stiig building adjacent to the experimental complex p Equipment, Arc Low Vo'tage Equiament, Local Contr;" ;•: ^ PL *as modified to serve as the test facility. Center, and Decel Power Supply were placed on a "igure ' shows diagrammatical";/ the overall layout uf mezzanine erected for this facil'ty. The Surge Poor's, FIG. 1 TFTR NEUTRAL BEAM TEST FACILITY *This tfork was supported by U.S. Department of Energy Contract DE-AC02-76-CH0-3073. Tfi"' DDCiiMEKi lo u:;Llic,iUfi '. Disconnecting Switch. This 1s a manual ly-operated no-load disconnect swftcn for primary sower isolation, rated 600 amps continuous, with fault current capacity of 57,000 amps peak asymmetrical. 2. Vacuum Interrupter, ft fast-actinc vacuum inter rupter has a continuous duty rating of 12u0 ai^os at 13.3kV, an interrupting capacity for a orim.iry fault of 52.000 amps peak asymmetrical, witi an interrupting time of 25 mil Ifseconds. Voi tage Control Ier . The oil immersed, 3-phase autotransformer is fed from the switch-^ear unit by bus duct. The output voltage is variable from 2.76kV to U.SkV, in 17 discrete values. A separate impulse from the control station is required to move from one -tap to the next one. No tap change can be made luring the pulse. The tap changer returns automatically to its lowest position after opening of the vacuum inter rupter. Normal pulse load on the autotransformer is a maximum of 530 amperes for 5 seconds. It can withstand a fault current of 57,000 amperes asymetncai. The FIG. 3 INDOOR INSTALLATION voltage controller weighs anorox'mate1/ 20,000 pounds. Transformer-Recti fjer. ~'r.e output of this unit at wh' •-£ • 63kV equipment is noused, is under positive air rated pulse current of 55 Vnps will range from jGfcVDC pre cure to mi limine dust intrusion. Figure 3 shows to laSkvOC as selected b/ the t-p changer. -^e indoor installation. A 2-ton monorail hoist serves t'ne mezzanine area ana :he M-oaulator-Regul ator; the 1. Power Transformer. Tne oil filled transformer nas ? jui'di.ng 20-ton bridge crane services the pit area. a step-up 1 ine-to-1 ine rafo of '• to 7. B. The ori-'ary winding is wye-connected to the output of the auto transformer by bus duct. The two seconaary windings, Equipment Description wye and delta, are connectea for 12-pulse operation. The pulse rating of the transformer is 10.5MW; equiva "The TFTR Neutral Beam Test Facility is a low lent tbermal racing is estimated to be 3MW. The trans impedance power system with an output of 65 amps at former has been designee to witnstand simultaneous iiJOkVDL, with a,pulse duration of 5 seconds at a duty faults of the ion sour;.* and tie modulatnr-regulator. factor of 0.033 . It is shown schematically in Figure It weighs approximately 115,000 pounds. =+. Each subsystem i-3 described below. FIG 4 SCHEMATIC DIAGRAM OF NEUTRAL 9EAM POWE* SUPPLY Primary Power Subsystem 2. 72-Pulse Rectifier. Two 3-ohase full-wave bricge network's are connected in series, resulting in an out Energy for test facility operation is supplied by put rippla frequency of 720 Hz. tacn bridge leg is made tne local public utility system. An existing UBkV up of 96 silicon power diodes connected 1n series, fflr substation transforms it \o 13.3kV through a 50 MVA a total of 1152 diodes. These are grouped into 6 transformer. strings and are immersed in transformer oi;. Each diode 1s rated 300 amps RMS, 2500 PIV. Switchgear. This is a self-contained metal-clad unit. It includes: 2 Surge 3oon. "he equipment in this room is fed Auxiliary Supply Subsystem '•"3TI the transfcrmer-rectifier by a run of high voltage coaxial caoie. 7his room contains: Ion Source F1 .anient Supply- The filament supply 1s split into two portions. The circuitry referenced i. Vans i en t Suppression Capacitor. Tnis unit in- to ground is in the Filament Low Voltage Equipment ."?ase: t-e rate of rise of the leading edge of the cabinet. This consists of a motor-operatea variable :j-*reit oulse when the load is switched on. fhe voltage transformer, a soft-start network and a tapped -aoacitor Dank consists of six parallel strings of four line inductor. Input is from a 480V, 3-phase 6DH2 - -nicrofarad, 50k'/ capacitors in series, resulting in a distribution bus of the Power Distribution Center. 5 -nicrofarad, 2Q0lcV unit which is charged to 168kVDC. Output is 0-iOCiVAC, 3-phase, pulsed on anJ off from the •acp capacitor ias a 300 ohm current limiting resistor Local Control Center. The circuitry nefe enced to the JM a neon bulb to indicate *ts charged conditon. accel high voltage 1s contained in a portion of the High Voitage Enclosure. This consists of a step-down :. Safety ^w-iches.. These switches discharge the transformer and a 12-pulse rectifier rated 6000 amps, :aoac*,tor Dank, with a time constant of 800 ^sec. One 13VDC for 6 seconds every 2.5 minutes. ,wi*.cr is electrically neld open and gravity closed. v? -.eccnd switcn is a tiarua 1 switcn operated from the Arc Supply- The arc supply is nearly identical to '.-i'.-rie of tne surge room, and serves as a back-up. the filament supply. Its output is rated at 3000 amps, "i; switch is key interlocked with power carrying 50VDC for 5 seconds every 2.5 minutes. •*:events of the system. The surge room door cannot be enu-rec jrless all power is removed, the key interlock High Voltage Enclosure. This unit houses those '.•-•ain is saMofied, and the switch is locked in Its portions of the filament and arc power supplies which grounded ;>osi tion. are referenced to the accel high voltage, and a circuit for passive limiting of energy available to a source ; ,nwL;ar. Tils unit consists of six ignitron tuoes fault, until the modulator-regulator can switch off •' •.Fr":«?":. .-^*.r. corona rings and protective spark gaps. accel and gradient grid voltages. The Hign Voltage '-'. i: ^ed *>on -i lignt pipe signal into a trigger Enclosure is internally cooled and insulated by SF^ ;eAera:-r //hich j-ilizes a Cryotron tuDe to develoo t.ne it 30 PSIG. It is connected to the Modulator-fteguTator •"-'••n.g ?j*ze. Th»? crowbar diverts fault energy away with a triaxial caole. •Von the iiod'jla tor-regulator within 2 to 3 microseconds i-~.?r fault detection, ihe crowbar handles a charge of ^^r^^'^tS' / JO cou'ombs until the vacuum interrupter Auxiliary Services Subsystem '^en: 3no disconnects the power supply. Power Distribution Center. This unit switches ana '. 1'':'*,es Pesistor. This 5 ohm resistor serves as a monitors all non-pulsed AC power for the system. It :j'-jT-.g impedance *or the high voltage coaxial l''ie contains protective circuitry and distribution trans *.p*.«es^ tie capacitor Dank ana the Tiocu'i a tor-regulator, formers. -t consists of ten power resistors connected in parallel , ^:P '•atfta 50 ohms, 125kV, 50 kilojoules, mounted atop local Control Center. The control center contains f.re crowoar stack . equipment for local operation of the Test Facility. Its mimic panel with status lamps, digital meter dis plays and fault annunciators monftors the sy:tem status. ''ad'j1 ator-Pegul 3 tor Sups /stem A panel containing test points and a multichannel oscil1oscope provides additional information. A CAMAC P'ITS -jRit switcnei arc regulates the voltage de- irate is provided for computerization of data and ':/pred to the ion source through a nigh voltage switch operational parameters, for generatinr timing signals, *LDe. Major components are: and for monitoring events and fault sequences. Other modules are available for buffering and storing data -Jigh Voltage Switch Tube. This is a high power for use by the TFTR real-time system control coft'puter tetrode, speriaJly aesigned for t.hfs application, rated facility (CICADA), and to emulate CICADA for loci? -J*. 2 megawatt anode dissipation for a 5 sec. pulse and (stand-along) operation. 21Q -.'.' noldoff2. fiie anoae is cooled by circulating 'ow-conauct'vity *ater at about 250 GPM. Electrical Cooling Water System. A low-conductivity closed- 'nsulation of the external portion of the tube is loop water system supplies cooling for the Modulator- achieved oy circulating SF. at about 20 CFM at a Regulator, High Voltage Enclosure, and Uwel Supply. pressure of 3 PSIG. The voltage drop across the tube This u 1t Is rated 350 GPM at 100 PSIG o<* 'i megohm- will vary linearly to compensate for the voltage droop centimeter water. from the transformer-rectifier during the power pulse; a minimum of 3k'/ is needed for regulation. Linear operation up to 30ky across the tube with 65 amps is Source Protection Subsystem sessile without exceeding anode dissipation. The nominal filament Current is 4620 amps at 3.85VDC. The Fault Detector. Two basic types of faults are tube ': connectec in a floating deck configuration with possible, each requiring a different response. One its at'ode at priirary power supply potential ana the type is due to accel faults, characterized by a sudden cathoje connected to the Ion source. collapse of accel voltage, necessitating a turn off of power to the loc Soarce for several msec, before re Gradient: Grid Divider. A compensated RC voltage start. Such faults are common, occurring almost every divider sets tne potential" of the 1on source gradient pulse. The second type of faults, due usually to an grid at values ranging from 75% to 90* of the switch arc spot, occur less often and require a termination tube cathoae potential. Current is in the mllliamp of the pulse. range. Heat produced 1n the resistors is dissipated by boiling freon in a clnsed-loop systei. The fault detector observes Accel, Gradient Grid, and Oecel voltages and currents, either by capadtive or inductive sensing. It compares each waveform to a reference. If the current waveform exceeds the refer ence for some period of time or the voltage waveform goes below Arc Modulator. An arc modulator circuit located inferences 1'n the nigh voltage enclosure controls the shape of the ar<; current pulse and shunts the arc current away from 1. A. HeUz, P. Winje, and H. Murray, '-TFTP Seutral the jecel Power Supply. Tms water-cooled vacuum- 2. E\ Carter, J. i3"'»:*nan, J. StaHey, A. Ceitz, tiice regulated supoiy feeds the ion source grid which R. Winje, and R. Gray, "Twenty Million Watt vacuu"1 suDoressei free electrons from backstreamlng Into the Tubes and Test Results', IZEi Trans, on 'luc. Sci , icn extraction chamber. The oecel power supply Vol. NS26, No. 3 (June 1979 J. pdO69-4071 . oroduces a pu'se of • /<7 at 15 amps. 3. M. Katz. private communication. 3ulsed Loaas 4. W. Praeg, "Overcurrent Protection for the TFT* Neutral Beam Sources During Soarx Down-', Proc . ith Symo. or Engr. ^rcos. 'jf "us lor 3es . IEEF. Dupl . \o. •.cad Aarks 7KHiaa5-5 DPS *iov. i J73. . pnei-^es. Accel . T^,e accel dummy load, enclosed in a meta'* 5. V Bowen, A. Deitz, 'i. ''urray, and 3.. «inje, ''Quiing, consists of a numoer of vertical stacks of 'Design and Test of ire T/-j n sm i s s '"on Line T.- the TFT? carson resistors which can oe connected in series and Neutral Beam Ion Source", Proc. %i^ Symp. on £ngr. parallel to yield a range of values from 1 BOO to 4150 Probs. of Fusion Rez . IEEE ?upl No. 79CHH41-5 NPS ohms. Forced air keeps the- resistors coot during (Nov. 1979), p705-70E. pulsing. Connection to the output of the modulator- regulator is /1a RG-1&/U coaxial cable. Arc/F1-ament. These dummy loads are housed to gether in a high-voltage case located above the target chamber. Nlcnrome elements used for the load are forced air cooled, Target Chamber Vh1s vacuum vessc-1 carries tne (on source and contains an instrumented, water-cooled calorimeter for particle beam power measurements. Both mechanical and turbomolecular pumps maintain the vacuum. A specially aesigned high-voltage transmission line connects the ion source to the High Voltage Enclosure^ providing filament, arc, accel and gradient grid power, and 19 digital and analog data channels. This transmission line is filled with SFg at 3 to 4 PSIG for cooling and Insulation^,