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

2

Program of works

Final objective of work: Development of a plasma-focus discharge chamber with DT-neutrons yield of 1013 n/pls. Problems to be solved to achieve the final objective :

• Tryout of the regime of stable yield of DD-neutrons 1011 n/pls during
• peration 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.

3

PF-chamber of Mather type

Copper anode  70 mm Steel cathode  120 mm, 280 mm long. Ceramic insulator  70 mm, 70 mm high. Stainless steel case.

4

Cascade facility

16 energy sections with capacity Cs = 41 µF each. Maximum charging voltage U0 = 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.

5

L

• a

d

U

• P R

Ê Á

L

Ê Á L K / 2

L

K / 2 L 1 Ò

L

2 Ò

L

n

R

è

Ñ

Ê

Ñ

Ê Á

Ï Ð

1

L

• a

d

U

• P R

Ê Á

L

Ê Á L K / 2

L

K / 2 L 1 Ò

L

2 Ò

L

n

R

è

Ñ

Ê

Ñ

Ê Á

Ï Ð

1

ССB = n·CS, where n – number of used sections. Р – switching solid body dischargers. RCB = RS/n, where RS = 30 m – ohmic resistance of one section. LCB = 32/n nH – capacitor bank inductance. LК = 30/n nH – inductance of cable transmission line. СК = 1.7 µF – capacity of cable transmission line. LТ= L1Т + L2Т= 5.2 nH +4 nH=9.2 nH - inductance of current collector. Ln=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 RU = 330  and Rogowski coil ПР1, recording current in active resistance.

Equivalent electrotechnical circuit of Cascade facility

6

Experiments with PF-chamber on Cascade facility

• 6

• 6

• 6

• 6

• 5
• 35
• 30
• 25
• 20
• 15
• 10
• 5

Время, с отн.ед.

Signals recorded on Cascade facility, 6 sections, Р0 = 8 torr, U = 40 kV, yield 6,51·1010 n/pls. Location of PF-chamber on the current collector of Cascade facility

• 6

• 6

• 6

• 6

• 5
• 3x10

• 2x10

• 1x10

Производная тока, А/с Время, с

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Results of experiments on Cascade facility

Calculated dependence of chamber inductance on time

a) – current in the chamber

b) – voltage at the chamber input

I Udt L

t





L,nH Time, s I, A Time, s U, V Time, s a) b)

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ÑÂÌ Ã Lí Lc1 Lc2 Lc10 Rc1(t) Rc2(t) Rc10(t) ê ê ê Ð

Geometry of sectionalized EOS Electric diagram of the current generator with sectionalized EOS

Current generator for the explosive experiment with plasma focus chamber

9

1 2 3 4 5

Current generator with sectionalized EOS

Generator design Экспериментальная сборка Load voltage Ток в нагрузке

10

Experiment on plasma focus chamber powering by EMG (working gas is DT-mixture at pressure ~ 8 torr)

Экспериментальная сборка 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.

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.

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Results of explosive experiment. Current measurements.

• 200,0k

Время, с I, A explosion BD5 experiment 49 BD5 167,0µ 168,0µ 169,0µ 170,0µ 171,0µ 172,0µ 173,0µ 174,0µ 175,0µ 0,0 200,0k 400,0k 600,0k 800,0k 1,0M 1,2M 1,4M 1,6M 1,8M

Integr BD1 Integr BD2 Integr BD3 Integr BD5 Integr BD6

• 3,0x10

• 2,5x10

• 2,0x10

• 1,5x10

• 1,0x10

• 5,0x10

explosion BD5 experiment 49 BD5 Производная тока, A/с Время, с

Current waveforms from explosive experiment Current waveforms from explosive and laboratory experiments Signals from induction probes in explosive and laboratory experiments Current pulse parameters in the explosive experiment: The current reaches the maximum of 1,46 МА in 2,04 µs after the beginning

• f discharge.

The shell starts imploding in 2,74 µs after the beginning of discharge. The current drops to 1,4 MA by the beginning of shell implosion. Under similar conditions in the laboratory experiments with deuterium filling the current reaches the maximum of 1,38 МА by the time of 2,88 µs after the beginning of discharge.

12

Results of explosive experiment. Neutron measurements.

171,0µ 172,0µ 173,0µ

• 7
• 6
• 5
• 4
• 3
• 2
• 1

U (V) Time (mks) D1

tn= 933ns

171,0µ 172,0µ 173,0µ

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• 10
• 8
• 6
• 4
• 2

tn= 940ns

U (V) Time (mks) D2 171,0µ 172,0µ 173,0µ

• 12
• 8
• 4

U (V) Time (mks) D2 D3

Detector signal for measurements to 1011 n/pls. Detector signal for measurements to 1012 n/pls. Detector signal for measurements to 1013 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 1,42·1012 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 1,79·1012 n/pls. The fluence of neutrons with energies within the range 0,3÷15 MeV was 3,74·108 n/cm2. The average energy of neutrons within the specified spectrum range was 7 MeV.

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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 1012 neutrons per pulse has been achieved. 3. The experimental results have been used to determine the directions

• f further work on bringing the neutron yield to 1013 neutrons per

pulse.

Conclusion

Thank you for attention!