PLASMA FOCUS NEUTRON SOURCE POWERED BY EXPLOSIVE MAGNETIC GENERATOR - PowerPoint PPT Presentation

PLASMA FOCUS NEUTRON SOURCE POWERED BY EXPLOSIVE MAGNETIC GENERATOR V.E. Ablesimov, A.V. Andrianov, A.A. Bazanov, Yu.N. Dolin, P.V. Duday, A.Yu. Fevralev, A.M. Glybin A.M., A.V. Ivanovskiy, A.E. Kalinychev, G.V. Karpov, A.I. Krayev, S.S. Lomtev, V.N. Nudikov, N.I. Pozdov, S.M. Polyushko, A.F. Rybakov, A.N. Turov, A.A. Zimenkov Russian Federal Nuclear Center - All-Russia Research Institute of Experimental Physics Russia, 607190, Sarov, E-mail:karpov@elph.vniief.ru

Program of works Final objective of work: Development of a plasma-focus discharge chamber with DT-neutrons yield of 10 13 n/pls. Problems to be solved to achieve the final objective : • Tryout of the regime of stable yield of DD-neutrons 10 11 n/pls during operation of the plasma focus discharge chamber on the capacitor bank. • Acquisition of data (inductance and voltage at the plasma focus chamber input as a function of time) ensuring stable operation of the chamber. • Creation of an explosive current source generating a voltage pulse, close to the pulse produced on the capacitor bank, on the plasma focus chamber in the explosive experiment. 2

PF-chamber of Mather type Copper anode  70 mm Ceramic insulator  70 mm, 70 mm high. Stainless steel case. Steel cathode  120 mm, 280 mm long. 3

Cascade facility 16 energy sections with capacity C s = 41 µF each. Maximum charging voltage U 0 = 50 kV. The number of the used sections can be varied. Maximum energy intensity is 820 kJ. Maximum current is ~ 5 MA for the time ~ 5  s. 4

Equivalent electrotechnical circuit of Cascade facility P R P R L L L L Ê Ê Á Á Ê Ê Á L Á L 2 L 2 L Ò Ò L L Ò Ò 2 2 U U o o K K / / 2 2 1 1 K K / / L L n n R R è è Ñ Ñ Ñ Ñ Ê Ê Á Á Ê Ê L L o o a a d d Ï Ï Ð Ð 1 1 С С B = n · C S , where n – number of used sections. Р – switching solid body dischargers. R CB = R S / n , where R S = 30 m  – ohmic resistance of one section. L CB = 32/ n nH – capacitor bank inductance. L К = 30/ n nH – inductance of cable transmission line. С К = 1.7 µ F – capacity of cable transmission line. L Т = L 1 Т + L 2 Т = 5.2 nH +4 nH=9.2 nH - inductance of current collector. L n =13 nH – inductance of load connection link with current collector. Voltage data are taken from the readings of the voltage probes consisting of active resistance R U = 330  and Rogowski coil ПР 1 , recording current in active resistance. 5

Experiments with PF-chamber on Cascade facility 12 2x10 12 1x10 Производная тока, А/с 0 12 -1x10 12 -2x10 12 -3x10 0,0 -6 -6 -6 -6 -5 2,0x10 4,0x10 6,0x10 8,0x10 1,0x10 Время, с 5 0 -5 -10 отн.ед. -15 -20 -25 -30 -35 0,0 2,0x10 -6 4,0x10 -6 6,0x10 -6 8,0x10 -6 1,0x10 -5 Время, с Signals recorded on Cascade facility, Location of PF-chamber on the current collector of Cascade facility 6 sections , Р 0 = 8 torr, U = 40 kV, yield 6,51·10 10 n/pls. 6

Results of experiments on Cascade facility I, A t  Udt  0 L a) I Time, s U, V L,nH b) Time, s Time, s Calculated dependence of chamber inductance on time a) – current in the chamber b) – voltage at the chamber input 7

Current generator for the explosive experiment with plasma focus chamber L í Ð R c1 (t) R c2 (t) R c10 (t) ê ê ê ÑÂÌ Ã L c1 L c2 L c10 Electric diagram of the current generator with Geometry of sectionalized EOS sectionalized EOS 8

Current generator with sectionalized EOS 4 5 2 3 1 Generator design Load voltage Экспериментальная сборка 9 Ток в нагрузке

Experiment on plasma focus chamber powering by EMG (working gas is DT-mixture at pressure ~ 8 torr) The experimental assembly included 1. Helical explosive magnetic generator Ø 200 mm. 2. Explosive current opening switch consisting of 10 sections. 3. Mather-type plasma focus chamber. 4. System for gas pump-down and filling of the chamber. Экспериментальная сборка Measuring and diagnostic systems Electric measurements: а) measuring systems to control the initial powering of a helical EMG and its further operation together with a sectionalized explosive current opening switch; b) differential induction probes to measure the azimuthal distribution of current in the plasma focus discharge chamber. Neutron measurements: а) scintillation detectors to measure the time-of-flight and the time dependence of neutron radiation intensity; b) activation detectors from aluminum, copper, molybdenum, indium, Teflon and zinc to realize integral measurements of the neutron yield. 10

Results of explosive experiment. Current measurements. 1,8M Integr BD1 explosion BD5 1,6M Integr BD2 experiment 49 BD5 12 1,5x10 Integr BD3 1,4M Integr BD5 12 1,0x10 Integr BD6 11 1,2M 5,0x10 Производная тока, A/с 0,0 1,0M 11 -5,0x10 800,0k 12 -1,0x10 600,0k 12 -1,5x10 400,0k 12 -2,0x10 200,0k 12 -2,5x10 0,0 12 -3,0x10 167,0µ 168,0µ 169,0µ 170,0µ 171,0µ 172,0µ 173,0µ 174,0µ 175,0µ 0,0 1,0µ 2,0µ 3,0µ 4,0µ 5,0µ 6,0µ 7,0µ Время, с Current waveforms from explosive experiment Signals from induction probes in explosive and laboratory experiments explosion BD5 experiment 49 BD5 1,8M 1,6M Current pulse parameters in the explosive experiment: 1,4M 1,2M The current reaches the maximum of 1,46 МА in 2,04 µs after the beginning 1,0M of discharge. 800,0k I, A The shell starts imploding in 2,74 µs after the beginning of discharge. 600,0k 400,0k The current drops to 1,4 MA by the beginning of shell implosion. 200,0k 0,0 -200,0k Under similar conditions in the laboratory experiments with deuterium filling 0,0 1,0µ 2,0µ 3,0µ 4,0µ 5,0µ 6,0µ 7,0µ Время, с the current reaches the maximum of 1,38 МА by the time of 2,88 µs Current waveforms from explosive after the beginning of discharge. and laboratory experiments 11

Results of explosive experiment. Neutron measurements. t  n= 940ns D2 t  n= 933ns D1 0 0 0 -1 -2 -2 -4 -4 -3 U (V) U (V) U (V) -6 -4 -8 D2 -8 -5 -6 -12 -10 D3 -7 -12 171,0µ 172,0µ 173,0µ 171,0µ 172,0µ 173,0µ 171,0µ 172,0µ 173,0µ Time (mks) Time (mks) Time (mks) Detector signal for measurements Detector signal for measurements Detector signal for measurements to 10 11 n/pls. to 10 12 n/pls. to 10 13 n/pls. Scintillation measurements The detectors are placed at the angle of ~20 ° to the chamber axis at the distance of 58,33 m. The time-of-flight interval was 939 ± 6 ns, that corresponds to the neutron energy of 14,16 ± 0,15 MeV. The neutron pulse duration at half-height was ~185 ns. Corresponding duration of DD-neutrons was 110 ÷ 130 ns. The integral yield calculated due to probes signals was 1,42·10 12 n/pls . Activation measurements The activation detectors from aluminum, copper, molybdenum, indium, Teflon and zinc were used. The detectors were located on the edge flange of the chamber. The integral neutron yield estimated due to activation measurements was 1,79·10 12 n/pls . The fluence of neutrons with energies within the range 0,3 ÷ 15 MeV was 3,74·10 8 n/cm 2 . The average energy of neutrons within the specified spectrum range was 7 MeV. 12

Conclusion 1. New approach for preparation and realization of experiments on plasma focus chamber powering by the explosive magnetic generator has been realized. 2. The explosive experiment with deuterium-tritium filling of the plasma focus chamber has been conducted. The neutron yield exceeding 10 12 neutrons per pulse has been achieved. 3. The experimental results have been used to determine the directions of further work on bringing the neutron yield to 10 13 neutrons per pulse. 13

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