2370-12 School and Training Course on Dense Magnetized Plasma as a Source of Ionizing Radiations, their Diagnostics and Applications 8 - 12 October 2012 How to build a small Plasma Focus - Recipes and tricks Leopoldo Soto Comision Chilena de Energia Nuclear Casilla 188-D, Santiago Chile Center for Research and Applications in Plasma Physics and Pulsed Power, P4 Chile How to build a small Plasma Focus Recipes and tricks Leopoldo Soto Comisión Chilena de Energía Nuclear Casilla 188-D, Santiago, Chile and Center for Research and Applications in Plasma Physics and Pulsed Power, P4, Chile [email protected] School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission To build a plasma focus it is necessary to defin the followings parameters: - Energy ? - Capacitor, C? - Voltage operation, V0? - Inductance, L? - Current peak, I0 ? - Anode radius, a? - Effective anode length (over the insulator), z? - Operational pressure, p? - Insulator length, lins ? - Cathode radius, b? School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Why and for what a small PF? To do plasma research To study plasma dynamics and intabilities To study the X-ray emmited To study the neutrons emmited To study plasma jets … School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Why and for what a small PF? To develop a non radioactive source To do flash radiography and non destructive testing To do litography To develop a portable non-radiactive source of neutrons for field applications … To teach experimental plasma physics and nuclear techniques, to train students School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission You must make a decision about that PF you want Free decision about energy and voltage operation A motived decision, because you have a suitable set of capacitors (somebody gift to you or you found its in a old storeroom or laboratory). Some kV and tens of nF - few μF School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Motivation A plasma focus is a self-scale plasma device Devices operated in a wide range of bank energy (0.1 J – 1 MJ) have the same phenomenology L. Soto, C. Pavez, J. Moreno, A. Tarifeño and F. Veloso, Plasma Sources Sci. Technol. 19 ,055017 (2010) School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Motivation, Scaling rules Scaling parameters allow to reproduce similar phenomenology in devices operatedinawiderangeofbankenergy(0.1J–1MJ) L. Soto, C. Pavez, J. Moreno, A. Tarifeño and F. Veloso, Plasma Sources Sci. Technol. 19 ,055017 (2010) School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Motivation Scaling law for neutron yield, Y, to E<1kJ 200J FMPF-1 6 ] kA PF-400J 125J 9 I : 4,5 [ -4 0 I x 1 .43 8 5 Y = log Y PF-50J 4 PF-50J 1,7 1,8 1,9 2,0 2,1 log I 200J 6 125J FMPF-1 PF-400J : J] 8 [E 2,3 E .43 5 2 Y = PF-50J log Y 4 PF-50J 1,6 1,8 2,0 2,2 2,4 2,6 log E L. Soto et al. Plasma Sources Sci. Technol. 19 ,055017 (2010) School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Motivation Scaling parameters allow to reproduce similar phenomenology in devices operated in a wide range of bank energy (0.1 J – 1 MJ) Similarities and differences in devices from 1MJ to 0.1J Similarities ∼ ∼ The pinch radius and pinch length scale with the anode radius, and rp (0.1-0.2) a, zp (0.8-1) a ∼ ∼ 24 -3 The mean value of the pinch ion density scale with the filling gas density, and <n> 18n0 5x10 m . The drive parameter, the energy density parameter and the energy per mass parameter have practically the same value for any plasma focus experimentally optimized for neutron emission. This implies that: The magnetic field at the pinch radius has a value of the order of 30 to 40 T for anyyp PF experimentally yp optimized for neutron emission. The Alfvén speed in the pinch has practically the same value in any PF experimentally optimized for neutron emission. Any PF device with a similar drive parameter, energy density parameter and ion density, has a temperature of the same order. Thus, an experimental measure of temperature in a particular PF could be used to estimate the temperature of any PF experimentally optimized for neutron emission. The temperature was measured by other authors in a plasma focus of some kJ by means of spectroscopy techniques in ∼ 0.6 - 1 keV. Then, it is possible to assume that the temperature in any plasma focus operating properly, included the smallest ones like the PF-50J and the Nanofocus, has a temperature of that order. L. Soto, C. Pavez, J. Moreno, A. Tarifeño and F. Veloso, Plasma Sources Sci. Technol. 19 ,055017 (2010) “Drive parameter of neutron-optimized dense plasma foci”, D. Klir and L. Soto, accepted in in IEEE TPS to e published in December 2012) School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Motivation Similarities and differences in devices from 1MJ to 0.1J Differences The plasma focus is a self scale device. However, the stability regime, in which a particular PF device lives, depends on the energy of the device and of the size of the anode radius. Large PF devices (hundred of kJ and MJ) are in the ideal MHD region, and are unstable. On the contrary, the smallest device with stored energy less than 1J, Nanofocus, could be presents enhanced stability by means of resistive effects. PF devices in the range of hundred and tens of joules could be present enhanced stability by means of LLR effects. γ τ = 1 i i Ωτ = 1 i i / 5 1024 / 10 SPEED2 pinch PF-1000 pinch pinch Different plasma foci that = r = i = r i = r 0 i a 0 aa PF- 360 aa 1 wworkork wiwithth stostoredred eenergynergy = 1021 50kJ - 1MJ S ranging from 0.1 J to 1MJ 1kJ - 50kJ 7kJ 100J - 1kJ Fuego Nuevo II are plotted in the diagram m] PACO 4 1J - 100J 18 UNU/ICTP-PFF 10 < 1J for Z-pinch stability given [A PF-400J Ideal MHD 200J by Haines and Coppins FMPF-1 pinch r PF-50J 125J 15 4 I 10 PF-50J 1012 NF 0.25J NF 0.1J N α E/a 109 1015 1016 1017 1018 1019 1020 1021 1022 -1 N [m ] L. Soto, C. Pavez, J. Moreno, A. Tarifeño and F. Veloso, Plasma Sources Sci. Technol. 19 ,055017 (2010) School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Motivation A hundred joules PF as a neutron source, PF-400J 6 1.2x10 20 1.0x106 10 PF-400J 5 8.0x10 0 Voltage (kV) Y 6.0x105 0.8 4.0x105 0.4 A/s) 5 12 2.0x10 0.0 -0.4 6 7 8 9 10 11 12 dI/dt (10 dI/dt Pressure (mbar) 9 0 8 -1 7 -2 FM2 (volt) FM2 6 -3 5 4 0.0 3 -0.4 2 68 ns FM2 (volt) FM2 -0.8 1 ΔL = 1.5 m SHOT84 270603 0 0 200 400 600 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 t (ns) energy (MeV) PF-400J P. Silva, J. Moreno, L. Soto, L. Birstein, R. Mayer, and W. Kies, App. Phys. Lett. 83, 3269 (2003) School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Motivation A tens joules PF as a neutron source, PF-50J FM1 at 30.5 cm from the axis FM2 at 78.5 cm from the axis 2,0x104 0,4 dI/dt 4 0,0 1,6x10 -0,4 1,2x104 0 FM1 Y 8,0x103 a. u. a. u. -2 3 0 FM2 4,0x10 -2 Δ t = 22 ns => E = 2.48MeV n 456789 0 100 200 300 400 Pressure (mbar) time (ns) Average over 20 shots Neutrons maximum mean energy of 2.7 MeV, dispersion of 1.8 MeV L. Soto, P. Silva, J. Moreno, M. Zambra, W. Kies, R. E. Mayer, A. Clausse, L. Altamirano, C. Pavez, and L. Huerta “Demonstration of neutron production in a table top pinch plasma focus device operated at only tens of joules”. J. Phys. D: App. Phys. 41, 205215 (2008) School and Training on Dense Magnetized Plasmas L. Soto, Thermonuclear Plasma Department ICTP, Trieste, Italy, 8-12 October, 2012 Chilean Nuclear Energy Commission Motivation A tens joules PF as a neutron source, PF-50J Lef=6.3mm, ra=3mm, rcat=6.5mm, rcat/ra=2.17, Vc=28.7(8) kV, “Statistical characterization of the reproducibility of neutron emission of small plasma focus devices” A. Tarifeño-Saldivia and L. Soto, Physics of Plasmas 19, 092512 (2012) School and Training on Dense Magnetized Plasmas L.