Hostname: page-component-745bb68f8f-b6zl4 Total loading time: 0 Render date: 2025-02-06T11:52:47.526Z Has data issue: false hasContentIssue false
  • English
  • Français

Characteristics of pulsed power generator by versatile inductive voltage adder

Published online by Cambridge University Press:  05 December 2005

KIYOSHI YATSUI ,
KOUICHI SHIMIYA ,
KATSUMI MASUGATA ,
MASAO SHIGETA  and
KAZUHIKO SHIBATA
KIYOSHI YATSUI
Affiliation:
Extreme Energy-Density Research Institute, Nagaoka University of Technology, Nagaoka, Niigata, Japan
KOUICHI SHIMIYA
Affiliation:
Extreme Energy-Density Research Institute, Nagaoka University of Technology, Nagaoka, Niigata, Japan
KATSUMI MASUGATA
Affiliation:
Extreme Energy-Density Research Institute, Nagaoka University of Technology, Nagaoka, Niigata, Japan
MASAO SHIGETA
Affiliation:
Extreme Energy-Density Research Institute, Nagaoka University of Technology, Nagaoka, Niigata, Japan Permanent address: Ferrite Division, TDK Corporation, Narita, Chiba 286-8588, Japan.
KAZUHIKO SHIBATA
Affiliation:
Extreme Energy-Density Research Institute, Nagaoka University of Technology, Nagaoka, Niigata, Japan Permanent address: Ferrite Division, TDK Corporation, Narita, Chiba 286-8588, Japan.
Rights & Permissions [Opens in a new window]

Abstract

A pulsed power generator by inductive voltage adder, versatile inductive voltage adder (VIVA-I), which features a high average potential gradient (2.5 MV/m), was designed and is currently in operation,. It was designed to produce an output pulse of 4 MV/60 ns by adding 2 MV pulses in two-stages of induction cells, where amorphous cores are installed. As a pulse forming line, we used a Blumlein line with the switching reversed, where cores are automatically biased due to the presence of prepulse. Good reproducibility was obtained even in the absence of the reset pulse. Within ∼40% of full charge voltage, pulsed power characteristics of Marx generator, pulse forming line (PFL), transmission line (TL), and induction cells were tested for three types of loads; open-circuit, dummy load of liquid (CuSO4) resistor, and electron beam diode. In the open-circuit test, ∼2.0 MV of output voltage was obtained with good reproducibility. Dependences of output voltage on diode impedances were evaluated by using various dummy loads, and the results were found as expected. An electron-beam diode was operated successfully, and ∼18 kA of beam current was obtained at the diode voltage of ∼1 MV.

Keywords

Highly potential gradientInductive voltage adderPulsed electron beamPulsed power generator
Type
Research Article
Information
Laser and Particle Beams , Volume 23 , Issue 4 , October 2005 , pp. 573 - 581
Copyright
© 2005 Cambridge University Press

1. INTRODUCTION

Recently, the development of high-energy pulsed power generator was widely required (Mesyats, 2003; Mesyats et al., 2003; Bastrikov et al., 2003; Ozur et al., 2003) in the applications of a driver for inertial confinement fusion (Hora, 2004), pulsed microwave, free electron laser (Alesini et al., 2004), medical treatment, and nuclear spallation using pulsed proton beams (Nation, 1979). An inductive voltage adder system is a promising technology to obtain a high-voltage pulsed power, particularly in the high-current region in the order of several kilo-amperes. From such a viewpoint, a lot of high voltage accelerators using the inductive voltage adder system was developed in the past (Smith et al., 1988; Ramirez et al., 1988, 1992; Hoppe et al., 1998). Highly repetitive rate operation can be expected as well. The averaged potential gradient was, however, not high enough. For example, the averaged potential gradient was limited to 1.7 MV/m on “HERMES-III” at Sandia National Laboratories (Ramirez et al., 1992). If we are able to achieve a much higher potential gradient, it will be constructed to be more compact and realistic to various industrial applications.

From such a viewpoint, we have attempted to develop and demonstrate a compact pulsed power generator, VIVA-I, which features and is characterized by a high potential gradient. We designed a high potential gradient of 2.5 MV/m by using amorphous metallic cores. Experimentally, such an induction accelerator was successfully developed, of which details, including design concept and pulsed power characteristics, will be reported in this paper (Masugata et al., 1988).

2. DESCRIPTION OF VIVA-I

Figure 1 illustrates the basic principle of a pulsed inductive voltage adder system. Due to rapid change of the magnetic flux of the primary circuit, a high-voltage output will be induced in the secondary circuit. Experimentally, primary pulses from a pulse generator are fed to two induction cells, in which magnetic cores are installed. Figure 1b shows the equivalent circuit. Two primary pulses are added in series on the secondary circuit.

Basic principle of pulsed induction voltage adder.

The inductive voltage adder system, VIVA-I, consists of a Marx generator, a Blumlein pulse forming line (PFL), a pulse distributor, four transmission lines (TLs), two induction cells, and a diode. The primary energy storage of VIVA-I is the Marx generator of 17-stages, which is exactly the same as that used in a pulsed-power generator, ETIGO-I (Yatsui et al., 1985). The stored energy of the Marx generator is 43 kJ at a charging voltage of ± 75 kV, which yields 2.55 MV of output voltage.

Both PFL and pulse distributors are located in de-ionized water. Figure 2 shows the cross-sectional view of this section. The PFL used is cylindrical Blumlein line (BL) with switching reversed. The intermediate conductor (IMC) of the BL is directly charged by the Marx generator in ∼500 ns. The BL switch is a self-breakdown SF6-gas switch located between IMC and the outer conductor (OC). The design parameters of the BL output are as follows: ZBL (output impedance) ∼ 12.5 Ω, τBL (pulse width) ∼ 60 ns, and VBL(max) (output voltage) ∼ −2 MV.

Cross-sectional view of VIVA-I.

The output pulse of the BL is fed to the pulse distributor through four-channel pre-pulse switches (water, self-breakdown), and divided into four 50-Ω pulses. The pulses are then transported to the inductive voltage adder section through four oil-filled coaxial TLs.

Figure 3 shows the cross-sectional view of the adding section, which consists of two induction cells and a diode. The outer diameter and length of each cell are ∼1 m and ∼0.8 m, respectively. Two 50-Ω TLs are connected to each cell in parallel. Thus, the average potential gradient of ∼2.5 MV/m is achieved by the application of 2 MV. Amorphous cores are immersed in oil and the oil-vacuum interface is made of an acrylic insulator. Properties of amorphous metallic cores installed inside the cells are presented in Table 1. The amorphous tape is 21-μm thick and the insulator is 6-μm thick, yielding a filling factor of ∼70%. The receptivity of the tape is ∼130 μΩ·m

Size and characteristics of amorphous core (1 core)

Cross-sectional view of pulse adding section.

Figure 4 shows a typical B-H curve. As seen from Figure 4, the core features a large flux swing that is ΔB = Bs + Br ≥ 1.75 T, where Bs and Br are the saturated flux density and residual flux density, respectively.

Typical B-H curve of iron-based amorphous core.

The output voltage from two induction cells is added in series by a center conductor/MITL (magnetically insulated transmission line). Such an added pulse is finally delivered to the diode. In the initial load test of the system, we installed a resistor of liquid (CuSO4) solution or electron-beam diode.

Figure 5 presents the equivalent circuit of the whole system of VIVA-I. Several results of the initial tests are presented as follows.

Equivalent circuit of VIVA-I. M.S. and P.S. are main switch and prepulse switch, respectively. OC, IMC, and IC stand for outer, intermediate and inner conductors of Blumlein line, respectively. T.L. means transmission line. In Figure 5, we see IPFL = Icell.1 + Icell.2, Icell.1 = Iex.1 + Id, and Icell.2 = Iex.2 + Id. In the absence of the load, we see Icell = Iex.

3. RESULTS OF INITIAL TESTS

Initial tests of the whole system were carried out at Vch (charging voltage of Marx generator) ∼30 kV, which is less than 40% of the full charge voltage. To obtain characteristics of magnetic cores in the saturated level within the limited range of Vch, we first installed two cores to each cell. As a result, the value of Vτ of each cell was reduced to ∼0.067 V × s instead of the initially designed value of ∼0.1 V × s.

3.1. Open-circuit test

At first, the open-circuit tests were carried out by removing the center feeder/MITL of the adder. Figure 6 shows typical waveforms at Vch = 30 kV. As seen from Figure 6a, the charging voltage of PFL reaches 1.1 MV at t ∼ 600 ns, and then the BL switch is closed. From Figure 6b of the applied voltage of the cell (Vind), pre-pulse voltage of ∼100 kV is seen to be present for ∼600 ns, and after that negative main pulse of Vind ∼ 1.0 MV is obtained with the pulse width of ∼75 ns. Due to the presence of the pre-pulse above, cores are automatically biased, and good reproducibility was obtained even in the absence of the reset pulse. Figure 6c shows the excitation current of the cell (Iex). We see Iex builds up at t ∼ 610 ns, and gradually increases and reaches ∼8 kA at the peak of Vind at ∼700 ns. After t ∼ 780 ns, Iex significantly increases and reaches the peak value of 25 kA at t ∼ 850 ns, indicating the saturation of the magnetic cores at t ∼ 780 ns.

Typical waveforms of open-circuit test at Vch (charging voltage): (a) VPFL (voltage of PFL), (b) Vind (voltage of induction cell), (c) Iex (excitation current).

The integral of Vind from t ∼ 610 ns to ∼780 ns is calculated to be ∼0.065 V × s, which reasonably agrees with the previously stated Vτ value (∼0.067 V × s). As seen in the above agreement, it is clearly evident that the inverse excitation takes place by the prepulse.

Figure 7 shows the dependence of VPFL, Vind, and Iex on Vch. We see that both VPFL and Vind increase almost proportionally to Vch. Such a linear increase in Vind on Vch suggests that the magnetic cores are not saturated before the peak of Vind.

Dependence of VPFL, Vind, and Iex as a function of Vch (charging voltage) for open circuit test.

3.2. Dummy load test

Pulse-power characteristics were studied by using a resistance of liquid (CuSO4) solution as a dummy load. Three kinds of resistances (R[ell ] = 50, 120, and 580 Ω) were used in this test, where the dummy load was installed within the induction cell.

Figure 8 shows typical waveforms of VPFL, Vind, Vd, Icell, and Id. From Figure 8, we obtain the following peak values:

Typical waveforms of dummy-load test at Vch (charging voltage): (a) VPFL (voltage of PFL), (b) Vind (voltage of induction cell), (c) Vd (diode voltage), (d) Icell (cell current), and (e) Id (diode current).

It is noted here that Vind is reduced to almost half of VPFL. This is due to the fact that the input impedance of the induction adder decreases with the connection of the dummy load.

Figure 9 shows Vind and Vd (the peak diode voltage applied to the load) as a function of Vch. We see Vind and Vd are almost proportional to Vch. The voltage difference between Vind and Vd is basically due to the inductive voltage drop in the center conductor, L[ell ](dId /dt). We have calculated L[ell ] from the dimension of the center conductor to be ∼450 nH, which clearly corresponds with that estimated from these experimental results by using the relationship,

Dependence of Vd (diode voltage; marked by [bull ] (R = 50 Ω), [utrif ] (R = 120 Ω) and [squf ] (R = 580 Ω)) and Vind (voltage of induction cell; marked by ○) as a function of Vch (charging voltage) with R (impedance) as a parameter.

3.3. Electron-beam generation

The electron-beam generation experiment was carried out by using an annular diode (cathode; carbon, anode; Ti foil of thickness ∼20 μm), the outline of which is shown in Figure 10. The inner and outer diameters of the cathode are ID = 58 mm and OD = 76 mm, respectively, and the cathode-anode gap length dK-A = 17 mm. The axial magnetic field of BZ ∼ 0.84 T is applied to the diode and the drift region. The electron-beam current is measured by a Faraday cup placed at ∼160 mm downstream from the anode.

Cross-sectional view of electron-beam diode. The axial distance from the edge of the cathode is z = (a) 25 mm, (b) 70 mm, (c) 115 mm, and (d) 155 mm, respectively.

Figure 11 shows these typical waveforms of VPFL, Vind, Icell, Id, and Ib (beam current). Clearly, the electron-beam is generated with Vd ∼ 1 MV (estimated from Vind and Id by using Eq. (1)), Id ∼ 20 kA, and Ib ∼ 18 kA.

Typical waveforms of (a) VPFL, (b) Vind, (c) Icell, (d) Id, and (e) Ib (beam current). Vch = 30 kV, Bz (axial magnetic field strength) = 0.84 T, ID (inner diameter of cathode) = 58 mm, OD (outer diameter of cathode) = 76 mm, dk-a (cathode-anode gap length) = 17 mm.

By moving a thermo-sensitive paper in the axial direction, we have examined the behaviors of the axial transport of the electron beam. Figure 12 shows the results of various beam patterns in the z-axis. Although the electron beam can be transported downstream in the strong B-field region with almost the same diameter as the electron-beam diode, it begins to expand with larger diameter in the downstream with the weaker B-field.

Damage patters of the electron beam at various distance from the cathode: z = (a) 25 mm, (b) 70 mm, (c) 115 mm, and (d) 155 mm.

4. CONCLUDING REMARKS

A versatile induction voltage adder, VIVA-I, was successfully constructed. It features a high potential gradient of ∼2.5 MV/m. The initial operating tests were carried out with less than 40% of full charge voltage. As a pulse forming line, we utilized a Blumlein line with the switching reversed, where the amorphous cores are automatically biased due to the presence of the prepulse, and good reproducibility was obtained even in the absence of the reset pulse. In the open-circuit test, ∼2.0 MV of output voltage was obtained with good reproducibility. Dependences of output voltage on diode impedances were evaluated by using various dummy loads, and the results were found as expected. An electron-beam diode was successfully operated. The electron beam transport was observed with the beam current of ∼18 kA.

ACKNOWLEDGMENT

This work was partly supported by a grant-in aid for scientific research from the Ministry of Education, Science and Culture of Japan.

References

REFERENCES

Alesini, D., Bertolucci, S., Biagini, M.E., Boni, R., Boscolo, M., Castellano, M., Clozza, A., Di Pirro, G., Drago, A., Esposito, A., Ferrario, M., Fusco, V., Gallo, A., Ghigo, A., Guiducci, S., Incurvati, M., Ligi, C., Marcellini, F., Migliorati, M., Milardi, C., Mostacci, A., Palumbo, L., Pellegrino, L., Preger, M., Raimondi, P., Ricci, R., Sanelli, C., Serio, M., Sgamma, F., Spataro, B., Stecchi, A., Stella, A., Tazzioli, F., Vaccarezza, C., Vescovi, M., Vicario, C., Zobov, M., Alessandria, F., Bacci, A., Boscolo, I., Broggi, F., Cialdi, S., Demartinis, C., Giove, D., Maroli, C., Petrillo, V., Rome, M., Serafini, L., Musumeci, P., Mattioli, M., Catani, L., Chiadroni, E., Tazzari, S., Dattoli, G., Doria, A., Flora, F., Gallerano, G.P., Giannessi, L., Giovenale, E., Messina, G., Mezi, L., Ottaviani, P.L., Picardi, L., Quattromini, M., Renieri, A., Ronsivalle, C., Cianchi, A., Schaerf, C. & Rosenzweig, J.B. (2004). The SPARC/X SASE-FEL projects. Laser Part. Beams 22, 341–350.Google Scholar
Bastrikov, A.N., Vizir, V.A., Volkov, S.N., Durakov, V.G., Efremov, A.M., Zorin, V.B., Kim, A.A., Kovalchuk, B.M., Kumpjak, E.V., Loginov, S.V., Sinebryuhov, V.A., Tsou, N.V., Cervjakov, V.V., Yakovlev, V.P. & Mesyats, G.A. (2003). Primary energy storages based on linear transformer stages. Laser Part. Beams 21, 295–299.Google Scholar
Hoppe, P., Bauer, W., Bluhm, H., Carboni, V., Fockler, J., Kessler, G., Leber, K., Nielsen, K., Prestwich, K., Ratajczak, W., Rusch, D., Singer, J., Smith, I. & Spence, P. (1998). The KALIF-HELIA Accelerator: Description, Program, and Status. Proc. 12th Int'l Conf. High-Power Particle Beams, Haifa, Israel (Markovits, M. & Shiloh, J., Eds.), 1, 218–221.
Hora, H. (2004). Developments in inertial fusion energy and beam fusion at magnetic confinement. Laser Part. Beams 22, 439–449.Google Scholar
Masugata, K., Hozumi, Y., Aoyama, T., Shimiya, K., Shigeat, M., Shibata, K. & Yatsui, K. (1988). VIVA-I, Versatile Inductive Voltage Adder for High Voltage Pulse Power Generation. Proc. 8th Int'l. Conf. High-Power Particle Beams, Novosibirsk, USSR (Breizman, N. & Kryozev, B., Eds.), 2, 1064–1069.
Mesyats, G.A. (2003). Guest editors Foreword on the occasion of high the 25th anniversary of the Institute of High Current Electronics of the Russian Academy of Sciences, and references therein. Laser Part. Beams 21, 121.Google Scholar
Mesyats, G.A., Korovin, S.D., Gunin, A.V., Gubanov, V.P., Stepchenko, A.S., Grishin, D.M., Landl, V.F. & Alekseenko, P.I. (2003). Repetitively pulsed high-current accelerators with transformer charging of forming lines. Laser Part. Beams 21, 197–209.Google Scholar
Nation, J. (1979). High power electron and ion beam generation. Part. Accel. 10, 1–30.Google Scholar
Ozur, G.E., Proskurovsky, D.I., Rotshtein, V.P. & Markov, A.B. (2003). Production and application of low-energy, high-current electron beams. Laser Part. Beams 21, 157–174.Google Scholar
Ramirez, J.J., Prestwich, K.R., Alexander, J.A., Corley, J.P., Denison, G.J., Huddie, C.W., Johnson, D.L., Pate, R.C., Weber, G.J., Burgess, E.L., Hamil, R.A., Poukey, J.W., Sanford, T.W.L., Seamons, L.O. & Zawadzkas, G.A. (1988). HERMES III–A 16 TW, short pulse, gamma ray simulator. Proc. 7th Int'l. Conf. High-Power Particle Beams, Karlsruhe, West Germany (Bauer, W. & Schmidt, E., Eds.), I, 148–157.
Ramirez, J.J., Prestwich, K.R. & Smith, I.D. (1992). High power, short-pulse generators based on induction voltage adder. Proc. IEEE 80, 946–957.Google Scholar
Smith, I., Corocan, P., Nishimoto, H. & Wake, D. (1988). Conceptual Design of 1 30 MV Driver for LIBRA. Proc. 7th Int'l. Conf. High-Power Particle Beams, Karlsruhe, West Germany (Bauer, W. & Schmidt, E., Eds.), I, 127–136.
Yatsui, K., Tokuchi, A., Tanaka, H., Ishizuka, H., Kawai, A., Sai, E., Masugata, K., Ito, M. & Matsui, M. (1985). Geometric focusing of intense pulsed ion beams from racetrack type magnetically insulated diodes. Laser Part. Beams 3, 119–155.Google Scholar
Figure 0

Basic principle of pulsed induction voltage adder.

Figure 1

Cross-sectional view of VIVA-I.

Figure 2

Size and characteristics of amorphous core (1 core)

Figure 3

Cross-sectional view of pulse adding section.

Figure 4

Typical B-H curve of iron-based amorphous core.

Figure 5

Equivalent circuit of VIVA-I. M.S. and P.S. are main switch and prepulse switch, respectively. OC, IMC, and IC stand for outer, intermediate and inner conductors of Blumlein line, respectively. T.L. means transmission line. In Figure 5, we see IPFL = Icell.1 + Icell.2, Icell.1 = Iex.1 + Id, and Icell.2 = Iex.2 + Id. In the absence of the load, we see Icell = Iex.

Figure 6

Typical waveforms of open-circuit test at Vch (charging voltage): (a) VPFL (voltage of PFL), (b) Vind (voltage of induction cell), (c) Iex (excitation current).

Figure 7

Dependence of VPFL, Vind, and Iex as a function of Vch (charging voltage) for open circuit test.

Figure 8

Typical waveforms of dummy-load test at Vch (charging voltage): (a) VPFL (voltage of PFL), (b) Vind (voltage of induction cell), (c) Vd (diode voltage), (d) Icell (cell current), and (e) Id (diode current).

Figure 9

Dependence of Vd (diode voltage; marked by [bull ] (R = 50 Ω), [utrif ] (R = 120 Ω) and [squf ] (R = 580 Ω)) and Vind (voltage of induction cell; marked by ○) as a function of Vch (charging voltage) with R (impedance) as a parameter.

Figure 10

Cross-sectional view of electron-beam diode. The axial distance from the edge of the cathode is z = (a) 25 mm, (b) 70 mm, (c) 115 mm, and (d) 155 mm, respectively.

Figure 11

Typical waveforms of (a) VPFL, (b) Vind, (c) Icell, (d) Id, and (e) Ib (beam current). Vch = 30 kV, Bz (axial magnetic field strength) = 0.84 T, ID (inner diameter of cathode) = 58 mm, OD (outer diameter of cathode) = 76 mm, dk-a (cathode-anode gap length) = 17 mm.

Figure 12

Damage patters of the electron beam at various distance from the cathode: z = (a) 25 mm, (b) 70 mm, (c) 115 mm, and (d) 155 mm.