The paper describes new electric circuits of multi-cascade generators based on stepped lines. The distinction of the presented circuits consists in initial storage of energy in electric and magnetic fields simultaneously. The circuit of each generator, relations of impedances, values of initial current and charge voltages are selected in such a manner that the whole of initially stored energy is concentrated at the generator output as a result of transient wave processes. In ideal case the energy is transferred with 100% efficiency to the resistive load where a rectangular voltage pulse is formed, whose duration is equals to the double electrical length of the individual cascade. At the same time there is realized a several time increase of output voltage as compared to the charge voltage of the generator. The use of the circuits proposed makes it possible to ensure a several time increase (as compared to the selection of the number of cascades) of the generator energy storage, pulse current and output electric power

Gordeev, V.S.

Myskov, G.A.

Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)

NEW CIRCUITS OF HIGH-VOLTAGE PULSE GENERATORS WITH INDUCTIVE-CAPACITIVE ENERGY STORAGEV.S. Gordeev, G.A. MyskovRussian Federal Nuclear Center – All-Russia Scientific ResearchInstitute of Experimental Physics (RFNC-VNIIEF)607188, Sarov, Nizhni Novgorod region, Mira Prospekt 37, RussiaE-mail: gordeev@expd.vniief.ruThe paper describes new electric circuits of multi-cascade generators based on stepped lines. The distinction of the presented circuits consists in initial storage of energy in electric and magnetic fields simultaneously. The circuit of each generator, relations of impedances, values of initial current and charge voltages are selected in such a manner that the whole of initially stored energy is concentrated at the generator output as a result of transient wave process-es. In ideal case the energy is transferred with 100% efficiency to the resistive load where a rectangular voltage pulse is formed, whose duration is equals to the double electrical length of the individual cascade. At the same time there is realized a several time increase of output voltage as compared to the charge voltage of the generator. The use of the circuits proposed makes it possible to ensure a several time increase (as compared to the selection of the number of cascades) of the generator energy storage, pulse current and output electric power.PACS numbers: 84.30.Ng; 84.70.+p1  INTRODUCTIONDevelopment of high-current linear induction accel-erators at VNIIEF promotes a search for new circuits for systems  of  high-voltage  pulse  formation.  As  a  result there were developed multi-cascade generators on step-ped lines possessing 100% efficiency in ideal case [1, 2]. As well as all generators based on transmission lines they can be subdivided in two types - generators with capacitive and inductive energy storage depending on the fact whether an initial electromagnet energy is sto-red only in the electric field or the magnetic one. Below presented are circuits of new type [2-9]. Due to the fact that the energy in them is stored simultaneously in both the electric and magnetic fields, such devices are called generators with inductive-capacitive energy storage or inductive-capacitive generators. They are made of ho-mogeneous line sections (cascades) of the same electri-cal length T0 as a stepped line. A stepped line cased with a current interrupter placed at the output form an induc-tive storage. A matched load is connected to generator output in parallel with the current interrupter. In the in-ternal space of stepped line there is placed a high-volt-age electrode forming together with stepped line case a capacitive storage in the form of homogeneous line sec-tions (n≥2) of the same electrical length T0.Generators operate in the following way. In the clo-sed circuit formed by the stepped line case and current interrupter under the action of the external source there appears the current I0  and the magnetic energy is stored in the whole volume of stepped lines. Simultaneously a high-voltage electrode is charged up to U0  voltage from another external source, and the electric energy is stored in  several  cascades.  At  the  moment  when the  energy storage process is finished a switch S1 is turned on clos-ing  a  gap  between  a  high-voltage  electrode  and  the stepped line case. As a result, electromagnet waves ap-pear in the stepped line. A generator circuit, relations of cascade impedances as well as I0 and U0 values are se-lected in such a way that as a result of transient wave processes the whole energy is concentrated at the gener-ator output. At the moment when the first wave arrives to  it  there occurs  current  interrupter  S2  disconnection, and energy is supplied to the load where a squared pulse is formed with 2T0 duration.2  ELECTRIC CIRCUITS OF GENERATORSFig. 1 shows three circuits of generators with induc-tive-capacitive energy storage [2-6] that differ in confi-guration of capacitive storage. Capacitive storages in the first and second circuits consist of two cascades, and in the third circuit the number of charged cascades grows up to 4. Note that only those circuits have been found that raise the voltage.abcFig. 1. Circuits of generators with inductive-capaci-tive energy storage.In  order  to  get  100%  efficiency  in  ideal  case, impedances as well as U0 and I0 should be selected ac-cording to the formulas given below.For the first variant (Fig. 1a):),2(...,,2,1,)])(1/[()1(1 −=+−++= niiiZZ i λλλλВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.Серия: Ядерно-физические исследования (39), с. 36-38.36)]1)(2/[()1(11 −+−++=− nnZZ n λλλλ ,  ⋅= λ1ZZ n)1/()1( −++ nλλ , ( )( ) )]1(/[1/ 100 +−+= λλλ nZUI .For the second variant (Fig. 1b):3,...,2,1)],)(1/[()1(1 −=+−++= niiiZZ i λλλλ , =− 2nZ ( ) ( ) ( ) ,]5223/[112 −+−++=− nnZZ n λλλλ  ( ) )]522)(2/[(111 −+−++=− nnZZ n λλλλ ,  1ZZ n =( ) ( )2/1 −++ nλλλ ,  ( )( ) /522/ 100 −+= nZUI λ( )]1[ +λλ .For the third variant (Fig. 1c):( ) ( ) ( ) 4,...,2,1],1/[11 −=+−++= niiiZZ i λλλλ , ( ) ( ) ( ) ,]432/[113 −+⋅−++=− nnZZ n λλλλ  =− 2nZ,3−nZ  ( ) ( ) ,]32/[111 −++=− nZZ n λλλ  1−= nn ZZ , ( ) ( ) ( )]1/[32/ 100 +−+= λλλ nZUIFactor  λ equals to the relation between electric and magnetic energies stored in the generator. The voltage on the matched load for the first, second and third vari-ants  exceeds  U0  by  (λ+n-1)/2λ,  (2λ+2n-5)/2λ  and (λ+n-3)/λ times, respectively. Addition of every supple-mentary cascade to the generator raises the voltage on the load by for the first variant and by U0/λ for the sec-ond and third variants.As an example, Fig. 2 presents relations between im-pedances for  generators  with total  electrical  length of stepped lines equaling 3T0 for the case when in the elec-tric and magnetic fields the equal energy is stored (λ=1). In the first and second variants the generator consists of four cascades, and in the fourth variant – of five cas-cades. The voltage on the matched load exceeds U0 by 2,  2.5  and  3  times,  respectively.  Connection  of  each supplementary  cascade  raises  the voltage  for  the  first circuit by 0.5U0 and for the second and third one - by U0.abcFig. 2. Circuits of generators (see Fig.1) for the case when the total electrical length of stepped lines is 3T0 and λ=1.In  Fig. 3  presented  are  circuits  similar  to  those shown in Fig. 1 but with connection of switch S1 to the high-voltage electrode of capacitive storage through ad-ditionally charged (up to the voltage U0) transmission line with impedance Z0 [7-9]. In such devices, for exam-ple, those with a supplementary line in the form of high-voltage  cable  lines  connected  in  parallel,  switches  of multi-channel commutator S1 will be removed from the stepped  line  volume  that  will  facilitate  their  mainte-nance and substitution.For the circuits presented in Fig. 3 the relations of parameters have been obtained, provided they are ad-hered to, they possess 100% efficiency in the ideal case.For the first variant (Fig. 3a):( ) ( ) ( ) ,1,...,2,1,]1/[11 −=+−++= niiiZZ i λλλλ  ( ) ( )322/121 −++= nZZ n λλλ ,  ( ) /1210 += λλZZ( ) 2322 −+ nλ , ( )( ) ( )]1/[322/ 100 +−+= λλλnZUI .For the second variant (Fig. 3b):( ) ( ) ( ) 3,...,2,1,]1/[11 −=+−⋅++= niiiZZ i λλλλ , ( ) ( ) ( )]3733/[1212 −+−++=− λλλλ nnZZ n ,  =− 1nZ( ) ( ) ( )]2733/[11 −+−++ λλλλ nnZ ,  ( ) /11 += λλZZ n( )2−+ λn ,  ( ) ( ) 210 733/12 −++= λλλ nZZ ,  =0I( )( ) ( )]1/[733/ 10 +−+ λλλnZU .For the third variant (Fig. 3c):( ) ( ) ( ) ,4,...,2,1,]1/[11 −=−+++= niiiZZ i λλλλ  ( ) ( )( )]433/[112 −+−++=− λλλλ nnZZ n ,  =− 3nZ22 −nZ ,  ( ) ( )]33/[111 −++=− λλλ nZZ n ,  12 −= nn ZZ , ( ) ( ) ]39/[12 210 −++= λλλ nZZ ,  ( ) ⋅= 100 / ZUI( ) ( )]1/[33 +−+ λλλn .abcFig. 3. Circuits similar to those presented in Fig. 1  but with connection of switch S1 to a high-voltage electrode of the capacitive storage through a sup-plement transmission line.The  output  voltage  for  the  first,  second  and  third variants exceeds U0 by (2n+2λ–3)/2λ, ( ) λλ 2/733 −+ n  and 3(n+ λ –3)/2λ times, respectively. Addition of every supplementary cascade to the generator raises the volt-age by U0/λ for the first variant and by 3U0/2λ for the second and third variants.As an example,  Fig.  4  shows optimal relations  of impedances for generators with a total electrical length of stepped lines of 3T0, for the case λ=1. The voltage on the matched load exceeds U0 by 3.5, and 4.5 times, re-spectively. Connection of each supplementary cascade raises the voltage for the first circuit by U0  and for the second and third circuits - by 1.5U0.In order to raise the voltage on the load, in all cir-cuits under consideration it is necessary to increase the ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.Серия: Ядерно-физические исследования (39), с. 37-38.37number  of  cascades  and/or  diminish the parameter  λ. Addition of supplementary cascades is accompanied by the growth of  relation between maximal  and minimal impedances of stepped line that for coaxial lines does not exceed 20, as a rule, provided one type dielectric is used in the whole generator.abcFig. 4. Circuits of generators (see Fig. 3) for a par-ticular case that the total electrical length of stepped lines is 3T0 and λ=1.In  order  to  disconnect  the  current  interrupter,  one can use the circumstance that at the moment when the first wave arrives to the current interrupter the current grows for all circuits discussed by (λ+1) times. This can simplify realization of synchronous operation of several generators as a part of the multi-module facility. To reli-ably disconnect the current interrupter, it is expedient to increase the parameter λ, i.e., to grow the electric ener-gy  fraction  in  the  total  energy  storage.  The  analysis shows that the circuits proposed should possess a high efficiency at varying both cascade impedances and the parameter λ in rather a wide range.3  COMPARISON OF CIRCUITS WITH IN-DUCTIVE-CAPACITIVE AND CAPACI-TIVE ENERGY STORAGETo determine the field of possible application of the circuits proposed, let us compare characteristics of cir-cuits with inductive-capacitive energy storage and those with capacitive energy storage. As the first one let us se-lect a circuit of five-cascade inductive-capacitive gener-ator (Fig. 5a) presented in Fig. 2c, and as the second one - a circuit of a similar five-cascade capacitive generator (Fig. 5b) [2]. The last circuit was used when developing accelerators STRAUS and STRAUS-2 [10].In the ideal case both circuits possess 100% efficien-cy and form a squared pulse of voltage of 2T0 duration. To perform comparison, let us commit the values U0, Z, T0. In the first circuit the electric energy is stored 3U0 2T0/2Z as well  as magnetic  energy that  is  equal  to it. That is, the total energy storage is 3U02T0/Z. The output voltage,  current  and  electrical  power  in  the  matched mode are  U=3U0,  I=U0/2Z,  P=3U02/2Z.  In  the  second circuit, in the course of charging the forming line, the electric energy 6U02T0/5Z is stored. The output voltage, current  and  electrical  power  are  U=3U0,  I=U0/5Z, P=3U02/5Z in the matched mode.abFig. 5. Circuits of generators with inductive-capaci-tive (a) and capacitive (b) energy storage.Thus,  the  inductive-capacitive  generator  provides the same voltage rise in the maximal efficiency mode as the capacitive generator. However, in the first case the energy storage,  current  and output power increase by 2.5 times.From  the  comparison  performed  one  can  make  a conclusion that generators with inductive-capacitive en-ergy storage possess significant advantages. Along with a rather high factor of voltage increase they provide in-crease of energy storage, current and power by several times. An additional advantage of such devices (as com-pared to the capacitive generator discussed above (Fig. 5b) whose operating pulse is a second voltage one), is the absence of the pre-pulse voltage on the load. The last  circumstance  can  be  determinative  for  powerful generators with low-impedance loads.REFERENCES1. V.S.Bosamykin,  V.S.Gordeev,  A.I.Pavlovskii  New schemes for high-voltage pulsed generators based on stepped transmission lines // Proc. of IX Intern. Conf.  on High-Power Particle Beams “BEAMS 92”. Wash-ington, DC, May 25-29, 1992 v. 1, p. 511-516.2. V.S.Gordeev. Schemes of high-voltage pulse shapers on the basis of stepped transmission lines for high-cur-rent accelerators //  Problems of Atomic Science and  Technology.  Issue:  Nuclear-Physics  Research (35). 1999, No. 4, p. 68-70.3. V.S.Gordeev, V.S.Bosamykin. Schemes of high-pow-er  pulsed  generators  with  inductive  storages  on stepped  lines  //  Proc.  of  XI  Intern.  Conf.  on  High-  Power Particle  Beams “BEAMS 96”.  Prague,  1996. v. 2, p. 938-941.4. V.S.Gordeev,  V.S.Bosamykin.  Generator  of  high-voltage pulses. RF Patent N2121216. BI. 1998. № 30.5. V.S.Gordeev,  V.S.Bosamykin.  Generator  of  high-voltage pulses. RF Patent N2121217. BI. 1998. № 30.6. V.S.Gordeev,  V.S.Bosamykin.  Generator  of  high-voltage pulses. RF Patent N2121218. BI. 1998. № 30.7. V.S.Gordeev,  G.A.Myskov.  Generator  of  high-volt-age pulses. RF Patent N2161858. BI. 2001. № 1.8. V.S.Gordeev,  G.A.Myskov.  Generator  of  high-volt-age pulses. RF Patent N2161859. BI. 2001. № 1.9. V.S.Gordeev,  G.A.Myskov.  Generator  of  high-volt-age pulses. RF Patent N2164054. BI. 2001. № 7.10. V.S.Gordeev, G.A.Myskov, V.O.Fillipov. et al. Inves-38tigation of STRAUS-2 pulse electron accelerator char-acteristics // Problems of Atomic Science and Technol-ogy. Issue: Nuclear-Physics Research (35). 1999. No. 4, p. 71-73.ВОПРОСЫ АТОМНОЙ НАУКИ И ТЕХНИКИ. 2001. №5.Серия: Ядерно-физические исследования (39), с. 39-38.3940

New circuits of high-voltage pulse generators with inductive-capacitive energy storage

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New circuits of high-voltage pulse generators with inductive-capacitive energy storage

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Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)