Comments about IEC History and Future Directions

Transcription

1 Comments about IEC History and Future Directions George H. Miley University of Illinois Department of Nuclear, Plasma and Radiological Engineering, 103 S. Goodwin Ave., Urbana, IL Tel: (217) , The history of IEC development will be briefly described, and some speculation about future directions will be offered. The origin of IEC is due to the brilliance of Phil Farnsworth, inventor of electronic TV in the US. Early experiments were pioneered in the late 1960s by Robert Hirsch who later became head of the DOE fusion program. At that time studies of IEC physics quickly followed at the University of Illinois and at Penn State University. However, despite many successes in this early work, IEC research died as DOE funding stopped in the mid 1980s. In the early 90 s, R. W. Bussard of EMC revived work with a new major project based on a magnetic assisted IEC. While doing supportive studies for that project, G. Miley proposed a grided STAR mode IEC as a neutron source for NAA. This concept was later used commercially by Daimler- Benz in Germany to analysis impurities in incoming ores. This represented a first practical application of the IEC. During this period other research groups at LANL, U of Wisconsin and Kyoto University entered IEC research with innovative new concepts and approaches to IEC physics and applications. Much of this work is documented in the present and in past US-Japan Workshops. At present we stand on the threshold of a new area of IEC applications as neutron source, for isotope production, and as a plasma source. These applications provide a way to continue IEC understanding and technology development with the ultimate goal being a fusion power plant. Indeed, a distinguishing feature of the IEC vs. other fusion confinement approaches is the unique opportunity for spin off applications along the way to a power producing plant.

2 Characteristics in Pulse Operation of IEC Device with Confronting Two Plasma Sources M. Ohnishi, Y. Tsuji, N. Yoshida, and H. Osawa Kansai University Department of Electrical Engineering and Computer Science Yamate-cho, Suita-shi, Osaka, , Japan TEL: , An Inertial Electrostatic Confinement Fusion device converges the deuterium ions into the center. In order to avoid the atomic processes such as a charge exchange, an ionization, and an excitation, the gas pressure of the main vacuum chamber should be less than 0.5Pa. It is, however, difficult to initiate a glow discharge and keep it stable in such a low gas pressure. The ion source may be equipped to assist a discharge. The capability of the pulse power supply can deliver the current 100A at the applied voltage 80 kv during the period of 6 to 9 micro-second. The RF power supply of MHz works synchronously with the pulse power supply and an antenna sits in the side chamber attached to the main chamber. The aperture with a hole of 20 to 40 mm in diameter is inserted between the main and the side chamber to make a pressure difference between the main chamber and the plasma production chamber. While the gas pressure in the side chamber 4Pa, that of the main chamber is kept 0.5 Pa. The neutron production rate in using one plasma source achieves 5.1x10 7 1/sec, where the discharge current is 7.5 A, the applied voltage is 44 kv and the RF power is 200W. The increase of a plasma source will increases the discharge current and the neutron production rate. A large current operation can be realized under a low gas pressure by supplying the plasma produced in separate chambers. The neutron production rate will be expected by two times larger through the equipment of another RF plasma source in a confronting side. The results will be presented in the workshop.

3 Overview of the University of Wisconsin-Madison IEC Program * G.L. Kulcinski, E.C. Alderson, R.P. Ashley, D.R. Boris, L. Campbell, D.C. Donovan, B.J. Egle, G. A. Emmert, G.R. Piefer, R.F. Radel, P. Rusch, J.H. Sorebo, J.F. Santarius, S.J. Zenobia University of Wisconsin Fusion Technology Institute 1500 Engineering Drive, Madison, WI (608) , kulcinski@engr.wisc.edu The University of Wisconsin-Madison began its Inertial Electrostatic Confinement (IEC) program in 1994 and it continues today with a group of faculty, scientists and students. There are currently 3 major IEC chambers in operation (See Figure 1 below). Major experimental accomplishments include: 1) Steady State operation up to 180 kv and 60 ma, 2) production of steady state DD neutron rates up to 2 x 10 8 n/s, 3) Demonstration of fusion reactions with DD, D 3 He, and 3 He 3 He fuels, 4) Production of proof of principle levels of Positron Emission Tomography (PET) isotopes using protons from the D 3 He fusion reactions, 5) Coupling of a Helicon ion source to an IEC device, 6) detection of explosives with DD fusion neutrons, 7) Operation in a pulsed mode with DD fuels to produce 5 x 10 9 n/s during 1 ms pulses at 5-10 Hz, and 8) Detection of highly enriched U (93%) with pulsed neutrons from an IEC produced DD plasma. Major efforts in the development of IEC theory and modeling are now being coupled to advanced diagnostics in order to test out the predicted plasma behavior. Figure 1 Major IEC facilities at the University of Wisconsin-Madison

4 Improving IEC Particle Confinement Times Using Multiple Grids T.J. McGuire* and R.J. Sedwick Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 70 Vassar St. Rm , Cambridge, MA *ph: , A system of multiple concentric grids is shown to be capable of improving the efficiency of IEC fusion devices. Poor ion confinement in conventional IECs is the primary reason for low fusion gain. The ion orbit asymmetries due to a single grid cathode and stalk limit ions to fewer than 10 passes through the device regardless of collisions. Multiple grid systems are shown via a Particle-in-Cell simulation to allow ions to recirculate indefinitely in an idealized collisionless system. Background pressure can then be reduced without loss of total fusion output, improving both fusion output and efficiency. System density is limited by the build-up of un-neutralized space charge in the recirculating ion beams. A Particle-in-Cell code provides observations of total system density versus device size and input current. A hybrid device operating with low input currents and high recirculation at moderate background pressures is shown to provide IEC neutron generators with significantly improved electrical efficiency.

5 Integral Transport Approach for Molecular Ion Processes in IEC Devices G.A. Emmert * and J.F. Santarius Fusion Technology Institute Univ. of Wisconsin Madison, WI * (608) , gaemmert@wisc.edu A model for the transport of atomic ions and neutrals in spherical, gridded IEC devices was presented at the 2004 US-Japan workshop on IEC devices. We have extended this model to include molecular ions as well as atomic ions. Various molecular and atomic processes (charge exchange, ion impact ionization, and dissociative processes) between deuterium ions (D +, D 2 +, and D 3 + ) and the background gas are included. Ions enter the intergrid region primarily as D 3 + ions and, while being accelerated by the falling electrostatic potential, interact with the background gas to produce a source of cold ions (D + and D 2 + ) through interactions with the background gas. These cold ions are accelerated by the potential and produce additional cold ions through interactions with the background gas. A formalism has been developed which includes the bouncing motion of ions in the electrostatic potential well and sums over all generations of cold ions. This leads to a set of coupled Volterra integral equations for each ion species. The integral equations are solved numerically, and the energy spectrum of the ion and fast neutral flux is calculated. Macroscopic quantities, such as the current collected by the cathode, and the fusion rate between ions and fast neutral atoms and molecules with the background gas, are calculated. Comparison of the results from the multiple ion species model with an atomic ion model and with experimental data for the Wisconsin IEC device will be presented. Research supported by the US Dept. of Energy under grant DE-FG02-04ER54745.

6 A Counter Stream Beam D-D Neutron Generator H. Momota *, L. Wu, T. Hayamizu, and G. H. Miley University of Illinois Department of Nuclear, Plasma and Radiological Engineering, 103 S. Goodwin Ave, Urbana IL * momota@ameritech.net A counter stream beam D-D neutron generator to provide up to neutron/sec is proposed on the base of the d-d reactions. The generator consists of linear reaction chamber with 3m long and an external magnetic field of 0.3T, neutralizer at both sides of the reaction chamber, and r-f ion sources at both ends of the linear system. The magnetic field at the reaction chamber stabilizes the counter beam plasma against electrostatic two stream modes as well as magneto-static Weibel s filamentary modes. The r-f ion source is biased at 30keV so as to accelerate ions towards reaction chamber and neutralizers add electrons to the accelerated ions to perform total charge neutrality. The presentation concerns the total system including neutralizer and the stability issues and r-f ion sources are discussed separately at this workshop.

7 Low Pressure IECF Operation Using Differentially-Pumped Ion Sources K. Yamauchi*, K. Nozaki, M. Watanabe, A. Okino and E. Hotta Tokyo Institute of Technology, Department of Energy Sciences, 4259-J2-35 Nagatsuta, Midori-ku, Yokohama , Japan * , In a conventional inertial electrostatic confinement fusion (IECF) device using a glow discharge, the neutron/proton production rate is proportional to the cathode current because beambackground reactions are dominant in contrast with the original IECF concept. However, since the neutron/proton production rate of beam-beam reactions is proportional to the cathode current squared, beam-beam reactions have a potential to increase the neutron/proton production rate in a high cathode current region. In this study, a new IECF device using differentially-pumped ion sources was designed for the low pressure operation without the glow discharge. In the IECF chamber, a cylindrical grid cathode is concentrically placed on the axis of a cylindrical mesh anode, and two ion sources are oppositely mounted around the mesh anode. The ion sources allow the IECF device to be operated at a pressure of 10-4 Torr in the IECF chamber, which is much lower than that of 10-1 Torr in the ion sources. Generated ions in the ion sources are extracted through each orifice by the pressure gradient and the extraction electric field, and then accelerated to the IECF cathode. At first, a performance as differential pumping system and discharge characteristics of ion sources were investigated. Then, the neutron production rate at a lower pressure compared with that of a conventional IECF device was measured. Neutron production rate at a pressure of 0.3 mtorr was proportional to the ion current to the power of This implies that the fraction of beam-beam reactions was increased by the reduction of background pressure in the IECF chamber.

8 Theoretical Exploration of Some Issues Affecting IEC Fusion Rates 1 J.F. Santarius and G.A. Emmert University of Wisconsin Fusion Technology Institute 1500 Engineering Drive Madison, WI USA ; santarius@engr.wisc.edu Questions have arisen regarding the effect of the ion energy distribution when comparing D-D and D-T fusion reaction rates in IEC plasmas. 2 In particular, most present IEC experiments operate at pressures of Pa (~1-30 millitorr), for which most fusion reactions occur due to beam ions and fast charge-exchange (CX) neutrals interacting with the background gas. The relevant σv values are thus projectile-target ones, and the lower velocity of T ions at a given energy compared to D ions will give a lower σv value. This presentation will examine the effect of the ion and fast CX neutral energy distributions on the relative D-T to D-D reaction rate ratio for various parameter regimes. The other main issue to be explored in the presentation is the effect of the mix of species in the fusion source region on the total fusion reaction rate. Some indications exist that increasing D + and, to some extent, D 2 + fractions compared to the present D 3 + in the source region will lead to increased fusion rates for the same input power. One indicator is that the integral equation theoretical approach, discussed in the presentation by Emmert, predicts that CX neutrals produced by interactions of D 3 + with background D 2 0 create most of the fusion products when the CX neutrals fuse with the background gas. On intuitive ground, the relatively low-energy CX neutrals generated by D 3 + should be less effective in producing fusion than the more energetic ions and CX neutrals from the faster D + and D 2 + species. 1 Research supported by the US Dept. of Energy under grant DE-FG02-04ER Jaeyoung Park, private communication (2006).

9 High Voltage Pulse Modulator Hiroshi Horibe*, Masami Onishi, Hodaka Osawa Kurita Manufacturing Corporation Design Department Ujitawara town Kyoto Japan ; I work for Kurita Manufacturing Corporation in Kyoto Japan. My company products PBII equipment (Plasma Based Ion Implantation: Diamond like Carbon surface modification system equipment), high voltage power supply and pulse modulator. We delivered high voltage pulse modulator to Kansai University last year for IEC project. I talk about this modulator first. And also talk about other kind of pulse modulator which means Tube Modulator, Thyratron Modulator, IGBT Modulator and Pulse Transformer type. I talk something about my experience for high voltage, high repetition field. And introduce my company a little bit.

10 Stabilization of Counter Beam Plasma Column T. Hayamizu * H. Momota, L. Wu and G. H. Miley University of Illinois Department of Nuclear, Plasma and Radiological Engineering, 103 S. Goodwin Ave, Urbana IL * thayami2@uiuc.edu For the purpose of obtaining high efficiency of a penning trap neutron generator, the radius of the counter beam plasma column is required to be as small as possible. The radial profile r-f the plasma density caused a coupling between axial electrostatic waves and radial modes and consequently instability of a thin plasma column. Another magneto-static mode known as Weibel s instability prevent plasma from nuclear collisions because filamented on going ions and coming back ions take different paths after onset of the instability. Theoretical analyses indicated, however, that applying an external magnetic field parallel to the plasma column stabilizes both modes. Stability criteria for both modes are presented.

11 Theoretical Modeling of an Inertial Electrostatic Confinement Device A. Blumenthal Millburn High School 462 Millburn Ave., Millburn, NJ (973) , Potential well models of Inertial Electrostatic Confinement (IEC) devices have been formulated with solutions to Poisson's equation. The most recent and precise model comes from Swanson (1975), which accommodates a two-charge species with a normal distribution of azimuthal and radial ion energies. This study examines three variations in the potential well model from Swanson (1975) and developed by Meyer (2005), to improve the accuracy of the potential well solution for practical use to researchers. The first develops two functions in terms of the grid radius parameter: one for grid transparency and the second for standard deviation in azimuthal ion energy. The second variation is the modification of the ion species, and these potential wells are examined in terms of the mass-to-charge ratio factor. Third, variations in ion current are used to explain the effects different ion gun configurations as an alternative to gas discharge.

12 Investigation of Cylindrical Geometries in an Inertial Electrostatic Confinement Device 3 Brian J. Egle*, Gerald L. Kulcinski, John F. Santarius, Robert P. Ashley, Ross F. Radel, David R. Boris, Eric C. Alderson, Samuel J. Zenobia, David C. Donavan, John H. Sorebo, Logan D. Campbell University of Wisconsin Madison Fusion Technology Institute 1500 Engineering Drive Madison, WI *Phone Number: egle@wisc.edu The University of Wisconsin s Inertial Electrostatic Confinement (IEC) group has constructed a new device which has initially been tasked with investigating the performance characteristics of cylindrical anode and cathode geometries versus spherical geometries. The new device is named Helium-3 Cylindrical Transmutation Reactor ( 3 HeCTRE). It is a single walled stainless steel cylindrical vacuum vessel with dimensions of 46 cm in diameter by 46 cm in height. Experimental data taken with 3 HeCTRE compares two cathodes made with tungsten-rhenium wire, a 10 cm diameter sphere and a 10 cm diameter by 19 cm tall cylinder. Two cylindrical anode configurations were used for the experimental data, a 27 cm diameter by 43 cm tall stainless steel wire anode and a 25 cm diameter by 43 cm tall solid stainless steel anode. The data from 3 HeCTRE was compared to previous work by the Wisconsin group using an identical 10 cm diameter spherical cathode and a 50 cm diameter spherical anode. Experiments were conducted to investigate both the D-D and the D- 3 He fusion reactions. The data was collected at operating conditions ranging from -50 to -150 kilovolts cathode voltages, 30 milliamps meter current, and 0.3 pascal of pressure. Initial experimental data from 3 HeCTRE for both the cylindrical and spherical cathodes with the cylindrical wire anode showed a decrease in performance from the work done in a previous device at similar operating conditions. The results for D-D and D- 3 He are shown in figure 1 and 2 respectively. Figure 1: Initial experimental results for D-D reaction Figure 2: Initial experimental results for D- 3 He reaction 3 Research funded by the Grainger Foundation and Wilson Greatbatch

13 Spectroscopic Diagnosis of Plasma in the IEC * E. Alderson, G. Kulcinski, J. Santarius, R. Ashley, G.Piefer, R. Radel, D. Boris, B. Egle, S. Zenobia, University of Wisconsin, Dept of Nuclear Engineering and Engineering Physics, 1500 Engineering Dr. Madison, WI (608) ealderson@wisc.edu Spectroscopic analysis of emission lines produced by plasma in an Inertial Electrical Confinement (IEC) fusion device provides a useful noninvasive probe of IEC physics. In order to obtain a useful signal, a primarily linear ion path was produced via controlled injection of ions from a helicon plasma source into a spherical geometry IEC. The Doppler shifted emission spectrum yields a way to determine the relative ion energy distribution, as well as maximum ion energy. This diagnostic campaign examines how ion energy distributions depend on background pressure and cathode voltage. This work also contrasts the Balmer H α line and He I line measurements and compares the spectra of these neutralized species with the emission of ions by observing the Doppler shifted Ar II lines under similar conditions. *Research funded by the Granger Foundation

14 Steady State Implantation of He + and D + in Carbon-Carbon Velvet S.J. Zenobia*, G.L. Kulcinski, T. Knowles, R.F. Radel, D.R. Boris, C. Seyfert, D. Donovan, A. Creuziger, J. Nacker University of Wisconsin Madison Nuclear Engineering Engineering Physics, 1500 Engineering Drive Madison, WI (608) , zenobia@wisc.edu The High Average Pulsed Laser (HAPL) program [1] focuses on the design of a commercial direct-drive Inertial Confinement Fusion (ICF) reactor. Candidate materials used for the first wall armor of this reactor must be able to withstand temperatures near their operational limit and significant radiation damage due to ion bombardment. Carbon-carbon velvet (CCV) and tungsten-coated carbon-carbon velvet (CCV/W) samples (designed and created at Energy Science Laboratories Inc.) were irradiated and post-irradiation analyzed. The response of CCV and CCV/W in an ICF environment was investigated using energetic helium and deuterium ions to simulate the ICF target debris. CCV and CCV/W samples were irradiated at ll50 C to He + /cm 2 and a CCV sample was irradiated to D + /cm 2 at ll50 C. Current investigations include both CCV and CCV/W sample irradiations to ions/cm 2 at 1000ºC and 1150ºC, using both helium and deuterium ions. A Scanning electron microscope (SEM) was used for post-irradiation analysis on the CCV and CCV/W samples exposed to ions/cm 2. The CCV samples irradiated at 1150ºC and ions/cm 2 experienced significant roughening and fiber shaft corrugation from both the helium and deuterium ions. At 1150ºC and He + /cm 2 the tungsten sputter-coating on the CCV/W sample experienced surface roughening and rupturing. Sample irradiation was performed in the UW Inertial Electrostatic Confinement (IEC) laboratory and damage analysis was performed in the LEO 1530 SEM. Exposed-D + Exposed-He + 4 μm 4 μm Figure 1: SEM micrographs of CCV after irradiation to 1x10 19 ions/cm 2 at 1150 C. Acknowledgements: Partial financial support provided by the Naval Research Laboratory, the University of Wisconsin, the Grainger Foundation, and Wilson Greatbatch. [1] J.D. Sethian, An Overview of the Development of the First Wall and other Principal Components of a Laser Fusion Power Plant, Journal of Nuclear Materials, 347, p , 2005.

15 Vapor Deposition in IEC to increase Neutron Production * P.E. Rusch, R.F. Radel, G.L. Kulcinski, G.R. Piefer University of Wisconsin Fusion Technology Institute 1500 Engineering Drive, Madison, WI (608) , perusch@wisc.edu This paper addresses the method of using vapor deposited titanium on the walls, high voltage insulator, and electrodes of an Inertial Electrostatic Confinement Fusion device in order to increase neutron production rates. In current devices, high energy charge exchange neutrals do not frequently result in fusion when colliding with the first wall. Increasing the amount of deuterium in the wall may increase neutron production due to these neutral atoms. Titanium readily absorbs hydrogen species. Recent experiments at UW-Madison have utilized a vapor deposition titanium source in order to generate an approximately 1 micron thick coating on an aluminum surface. This coating will be used to trap deuterium in the surface layer of the IEC first wall. Previous work performed by researchers at Kyoto University has shown increased neutron rates by depositing titanium on IEC electrodes [1]. This work will investigate the change in neutron production rate after depositing titanium coatings on IEC first walls, insulators, and electrodes. References [1] K. Noborio, Y. Yamamoto, Y. Ueno, and S. Konishi, Evaluation of the Reaction Rate Between Beam Particles and Adsorbed Particles on the Electrodes of IECF Device, Given at 8 th US-Japan Workshop on Inertial Electrostatic Confinement Fusion, 2006 * Research supported by the Grainger Foundation.

16 Recent Progress in Pulsed Neutron Production at the UW Advanced Fusion Fuels Facility R.P.Ashley, Ross Radel, John Sorebo University of Wisconsin Fusion Technology Institute 1500 Engineering Drive Madison, WI USA ; The pulsed mode of operation of the Inertial Electrostatic Confinement fusion device has significant advantages for the detection of highly enriched uranium using fusion neutrons. The requirement for effective detection is a controlled series of high level D-D fusion neutron pulses and the time resolved detection of the resultant fission neutrons. This presentation will discuss the experimental apparatus designed to achieve this requirement and the performance enhancements that have recently been achieved. The technique of controlling the ion source to create the neutron pulses is discussed, and comparisons of the advantages and disadvantages of using this technique are made. Detecting HEU with the IEC fusion reactor Research supported by the Grainger Foundation and Wilson Greatbatch Assoc.

17 Dipole-Assisted IEC T. Hayamizu, R. E. Thomas, I. Parcel, H. Momota, and G. H. Miley University of Illinois at Urbana-Champaign, Nuclear, Plasma, and Radiological Engineering, 105 NEL, 103 S. Goodwin Avenue, Urbana, IL USA Progress and future plans for measurements of plasma properties in the UIUC Dipole-Assisted IEC will be described. The electron temperature and density were measured earlier using a triple probe technique [1]. It was verified that the addition of the magnetic field served to effectively focus the ions accelerated by the IEC grids. In addition, it was found that electron temperature was in 2-10 electron volt range and that temperature decreases slightly with increasing magnetic field strength, consistent with localization of lower energy electrons in the core region. For the next step, methods to control the potential inside the dipole using a biased insert are being investigated. An emissive probe has been constructed to measure the potential in order to verify the effectiveness of the potential control. Figure 1: A photograph of the plasma in the UIUC Dipole-Assisted IEC device. Note the strong focusing achieved through the magnet. [1] G. H. Miley, H. Momota, P.J. Shrestha, R. Thomas, and Y. Takeyama, Space Propulsion Based on Dipole Assisted IEC System, AIP Conference Proceedings, STAIF 2006, 813, pp , Albuquerque, New Mexico, February 12-16, (2006).

18 Detection of Highly Enriched Uranium Using the UW IEC Device * R.F. Radel, R.P. Ashley, J.H. Sorebo, G.L. Kulcinski, J.F. Santarius, G.R. Piefer, D.R. Boris, B.J. Egle, S.J. Zenobia, E.C. Alderson, and D.C. Donovan University of Wisconsin Fusion Technology Institute 1500 Engineering Drive, Madison, WI (608) , rfradel@wisc.edu This presentation overviews the work that has been done to date towards the development of a compact, reliable means to detect Highly Enriched Uranium (HEU) and other fissile materials and outlines the progress in the design and construction of a pulsed Inertial Electrostatic Confinement (IEC) D-D fusion device to be used for the detection of these materials. Initial pulsing experiments are being performed in a 0.6 m 3 vessel. Voltage on the 20 cm W-Re IEC cathode is held relatively constant during operation through the use of a 200 nf high-voltage capacitor. Hot filaments provide electrons to ionize fuel (typically D 2 ) gas. Cathode currents in excess of 5 ampere have been generated by pulsing a negative bias on the hot filaments. Between pulses, ion current is suppressed by holding these filaments at positive bias. D-D neutron rates of 2.4x10 9 n/s were achieved during 500μs pulses at 105 kv on the cathode, producing 3.35 A at a background pressure of 0.33 Pa. This neutron production rate has allowed the successful demonstration of HEU detection at UW-Madison, as shown in Figure 1. Neutron Counts HEU Detection Results 1.2x10 9 n/s during 0.5 ms pulses (2000 pulses) Fusion Pulse Thermal Neutron Decay Delayed Fission Neutrons No HEU HEU Time (ms) Figure 1: HEU Detection Results. IEC operation without HEU shows thermal neutron decay tail, but few counts between pulses. * Research supported by the U.S. Domestic Nuclear Detection Office under grant and the Grainger Foundation.

19 Atomic Processes in a R-F Discharge Deuterium Ion Source L. Wu *, H. Momota, T. Hayamizu, and G. H. Miley University of Illinois Department of Nuclear, Plasma and Radiological Engineering, 103 S. Goodwin Ave, Urbana IL * lwu2@uiuc.edu We discuss atomic processes in a R-F ion source for the penning trap D-D neutron generator. Applied r-f field accelerates electrons in a D 2 atmosphere and bring about various atomic reactions such as producing various states of atomic D, D ions, D 2 ions, and D 3 ions. By assuming all ionic species to be in low levels, number density of respective species are described in a set of rate equations. Numerical solutions of the rate equations are discussed for various feeding pressure of deuterium. Effects of loss rate of the ionic species are discussed too.

20 D-D Axial Neutron Generators: New Developments Michael Fuller, Melvin Piestrup, Charles Gary, Ted Cremer, Jack Harris Adelphi Technology, Inc., 981-B Industrial Road San Carlos, CA x20 Jani Reijonen, Tak-Pui Lou, K.-N. Leung, Richard Gough - E.O. Lawrence Berkeley National Laboratory Glenn Jones - G & J Jones Enterprises A new generation of getter-type neutron generators based on RF-Plasma ion sources has become available commercially. These ion sources produce larger ion currents with greater percent of atomic ion species (vs. molecular) than conventional methods. Both spiral and solenoid external-antennae designs have been built and tested. An overview will be presented of RF- Plasma neutron generator systems in fabrication and currently operational.

21 Development of Fast Numerical Code Based on Direct Interaction of Charged Particles N. Yoshida, Y. Tsuji, H. Osawa, and M. Ohnishi Kansai University Department of Electrical Engineering and Computer Science Yamate-cho, Suita-shi, Osaka, , Japan TEL: , A particle simulation is useful to analysis for the behavior of plasma particles. Our previous computational codes ignore the effect of charged particles on the self-interaction and take into account only static electric field between the anode and the cathode. The interaction among charged particles must be treated as N-body problems. The calculation of N-body problems needs much computational time. However, the plasma possesses high density at the center of IEC device. It is problem that the previous codes ignore the interaction. New code including the interaction is computed by the chip specialized to calculated gravity multi body problems. This machine is called Grape-6a. Grape-6a can study the interaction among plasma particles, because a equation of electrostatic coulomb force is similar to that of universal gravitation are. The computation time of the case that Grape-6a is used is compared with the ordinary computational time. I will talk that the computation time is reduced if Grape-6a is used. As the result, the calculation may be more reliable and predict more precisely the results of experiment.

22 Plasma Characteristics of the Ion Source Region In the University of Wisconsin IEC Device D.R. Boris, G.A. Emmert, J. F. Santarius University of Wisconsin-Madison Fusion Technology Institute 1500 Engineering Dr., Madison WI Ph: (608) drboris@wisc.edu The ion source region of the original UW-Inertial Electrostatic Confinement device consists of filament assisted DC discharge plasma that exists between the wall of the IEC vacuum chamber and the grounded spherical steel grid that makes up the anode of the IEC device. The plasma characteristics of the source region have been investigated using a planar tantalum Langmuir probe and a 75 cm 2 antenna made of stainless steel mesh used for the propagation of ion acoustic waves. The Langmuir probe is used as both a receiver for the ion acoustic waves and as a standalone diagnostic tool to obtain density and electron temperature measurements in the ion source region. Using these diagnostics the average ion mass of the source plasma has been measured for varying neutral gas pressures and varying filament conditions. This figure illustrates the experimental setup of the ion acoustic wave diagnostic used in the ion source region of the UW IEC device. Research supported by the US Dept. of Energy under grant DE-FG02-04ER54745, and the Grainger Foundation.

23 Anti-Personnel Landmine Detection by Use of an IEC Neutron Source K. Yoshikawa 1, K. Masuda 1 *, T. Takamatsu 1, S. Shiroya 2, T. Misawa 2, Y. Takahashi 2, E. Hotta 3, K. Yamauch 3, M. Ohnishi 4 and H. Osawa 4 1 Inst. of Advanced Energy, Kyoto Univ., Gokasho, Uji, Kyoto , Japan 2 Res. Reactor Inst., Kyoto Univ., Kumatori-cho, Sennan-gun, Osaka , Japan 3 Dept. of Energy Science, Tokyo Inst. of Tech., Midori-ku, Yokohama , Japan 4 Dept. of Elec. Engng, Kansai Univ., Yamate-chom, Suita, Osaka , Japan *masuda@iae.kyoto-u.ac.jp, Current status and achievements are described on the R&D of humanitarian anti-personnel landmine detection system by using an Inertial Electrostatic Confinement (IEC) fusion device as a compact D-D neutron source. A newly developed compact water-cooled IEC device of an inner diameter of 30 cm was manufactured for improvements of humanitarian landmine detection system. This device consists of double jacket chambers to provide sufficient water cooling, having the diameters of inner and outer chambers of, respectively, 30 cm and 40 cm. The 5 cm thick water jacket was designed as well to assure the sufficient reflection of 2.45 MeV D-D neutrons downward, where a thinner 1cm thick water jacket is installed at the bottom. This nonuniformity of water jacket thickness is expected to result in multiplied neutron flux downward. This water-cooling system enables the IEC device to operate stably at a high cathode current, leading to CW neutron yield of for cathode voltage of 80 kv and current of 45 ma with excellent reproducibility and long-term stability. A series of blind trials of detection of landmine imitators (wax-mixed diluted 100 g and 300 g TNT and RDX) was made to examine prototype detection system performance characteristics using the IEC30 neutron source. Three sets of NaI/BGO combined scintillators, and digitalized data acquisition system with anti-coincidence analysis were employed to measure neutron captured 10.8 MeV γ-rays emitted from nitrogen atoms in the landmine imitators.

24 Detection of Nitrogen Based Explosives Using the UW IEC Device 4 D.C. Donovan*, R.F. Radel, R.P. Ashley, J.F. Santarius, G.L. Kulcinski University of Wisconsin Fusion Technology Institute 1500 Engineering Drive, Madison, WI *(608) dcdonovan@wisc.edu The UW IEC fusion device has been run at steady state conditions using D-D fuel to produce sufficiently high neutron rates to cause gamma ray emission from a sample of high nitrogen content explosives material. Previous work on this subject at Wisconsin has resulted in the successful detection of a sample of C-4 explosives using neutron rates of 6.3x10 7 neutrons/sec, achieved by running at a cathode voltage of 135 kv and a current of 60 ma. After improvements to the system, neutron rates have now been raised to 2.2x10 8 neutrons/sec. Running at a cathode voltage of 120 kv and a current of 60 ma, successful detection of nitrogen samples has been achieved at rates of 1.0x10 8 n/s. With this increase in performance, the use of three NaI detectors, and a new detector configuration, we have now been able to successfully detect a sample of Urea (45% Nitrogen content) using less scanning time than before even with a lower cathode voltage of 120 kv. These results have also been furthered by the use of a unique detector and shielding setup used to model a variety of realistic scenarios. The shorter scanning time and lower cathode voltages lead to a design of a more compact and efficient scanning device to be used for the detection of explosives in containers traveling through vital locations such as airports, seaports, and across borders Exposure of 400 g Sample of Urea to 1.2x10^8 Neutrons/Sec (120 sec counting time) Counts 100 Excess Counts due to Nitrogen Activation With Urea Without Urea Energy (MeV) 4 Research Supported by the Grainger Foundation and the Greatbatch Foundation

25 FDTD Simulation on RF Ion Source for IEC H. Osawa, N. Yoshida, and M. Ohnishi Kansai University Department of Electrical Engineering and Computer Science Yamate-cho, Suita-shi, Osaka, , Japan TEL: , Three dimensional Finite Difference Time Domain (FDTD) method code is developed for the analysis of plasma profile in RF ion source for IEC. The code includes effect of time developing electromagnetic field by MHz radio frequency source, the atomic process of electron deuterium molecular and the particle tracking of electrons. The following figure and photo show the simulation results and the experimental photo. The code can follow the experimental plasma profile (density and position) to be very good coincident. In IEC device, beam beam fusion is effective for neutron production. More ion beam from ion source is needed for the fusion. The result of the code is useful for design of high performance RF ion source for neutron production in IEC device. Result of FDTD code White dots mean the spatial profile of electrons which have adequate energy for electron impact ionization. Photo of plasma in ion source RF coil antenna is set in the RF ion source for IEC device. Plasma is surrounding the antenna.

26 Measurement of 3 He( 3 He,2p) 4 He Reactions in an IEC Device Gregory R. Piefer 1,2, John F. Santarius 2, Robert P. Ashley 2, Gerald L. Kulcinski 2 1 Phoenix Nuclear Labs, 8123 Forsythia St. Suite 140 Middleton, WI, USA, greg.piefer@phoenixnuclearlabs.com Fusion Technology Institute, University of Wisconsin-Madison, 1500 Engineering Drive Madison, WI, USA, grpiefer@wisc.edu For the first time, the reaction rate for the 3 He( 3 He,2p) 4 He reaction has been measured in an IEC device. The rates measured so far are 748 ± 117 reactions / sec at 134 kv and 268 ± 76 reactions / sec at 124 kv (25 ma cathode current, 27 mpa background pressure). This result is significant, because it should lead to the ability to make accurate measurements of the 3 He- 3 He fusion cross section, and lay the framework for future experiments involving this fuel cycle. A sample proton spectrum from the proton detection system is shown below: Some of the major accomplishments required to achieve this goal include a greater than tripling of the maximum operational voltage (185 kv), a 6 fold increase in insulator lifetime (6 months), a system which can recycle 3 He gas at high efficiency, an increase in maximum current while decreasing pressure (75 27 mpa), independent control over ion current, and a factor of reduction in the noise level of our nuclear detection system. These accomplishments will also be discussed. Research on this project was funded by the Grainger Foundation, the Greatbatch Foundation, and the University of Wisconsin.

27 Theoretical Double Potential Well Regimes and Potential Well Measurements at the University of Missouri-Columbia R. M. Meyer*, M. A. Prelas, and S. K. Loyalka University of Missouri-Columbia Nuclear Science and Engineering Institute E2433 Thomas and Nell Lafferre Hall, Columbia, MO * * phone: (573) Multiple potential wells were hypothesized by Farnsworth 1 and Hirsch 2 based on the mutual repulsion of like charged particles constricted to intersecting radial orbits. Such a potential structure would be ideally suited to thermally insulate ions heated to fusion reactive energies from the container s physical boundary. 3 Modeling has shown that the number of alternating potential wells is practically limited to two, 4 and that these may not be stable. 5 Experimental results indicating the existence of double potential well structures have not been within experimental uncertainty 6,7,8 or based on assumptions that are not strictly true. 9 Thanks to the phenomenal increase in computational power over the last ~40 years, we identify double potential well regimes with respect to particle angular energy and perveance. The regimes are identified by computing many solutions to the 1-D orbital model and displaying the results in the form of contour plots. In addition, we present an automated electrostatic probe system for collecting data with regard to the radial potential profile in an Inertial Electrostatic Confinement device at the University of Missouri-Columbia. 1. P. T. Farnsworth, Electric Discharge Device For Producing Interactions Between Nuclei, U.S. Patent #3,258,402, June R.L. Hirsch, Inertial-Electrostatic Confinement of Ionized Fusion Gases, J. of Applied Physics, vol. 38, no. 11, pp. 4522, Oct O. A. Lavrent ev, Investigation of an electromagnetic trap, AEC-tr-7002, (1970). 4. I. V. Tzonev, Effect of Large Ion Angular Momentum Spread and High Current on Inertial Electrostatic Confinement Potential Structures, M. S. Thesis, University of Illinois-Urbana- Champaign, C. W. Barnes, Computer Simulation of Electrostatic Confinement of Plasmas, Annals New York Academy of Sciences, vol. 251, pp. 370, D.J. Meeker, J.T. Verdeyen, and B.E. Cherrington, Measurement of electron density in a cylindrical inertial electrostatic plasma confinement device, J. Appl. Phys., vol. 44, no. 12, Dec D.A. Swanson, B.E. Cherrington, and J.T. Verdeyen, Potential well structure in an inertial electrostatic plasma confinement device, Phys. of Fluids, vol. 16, no. 11, pp. 1939, Nov K. Yoshikawa et. al., Measurement of Strongly Localized Potential Well Profiles in an Inertial-Electrostatic Fusion Neutron Source, Nuc. Fusion, vol. 41, no. 6, pp , Y. Gu and G. H. Miley, Experimental study of potential structure in a spherical IEC fusion device, IEEE Trans. on Plasma Science, vol. 28, no. 1, pp. 331, Feb

28 Intensity Distribution of D- 3 He Fusion Reaction Rate in an IEC device T. Fujimoto, T. Oishi, H. Zen, T. Takamatsu, K. Masuda and K. Yoshikawa Institute of Advanced Energy, Kyoto University Last year, in order to make clear the intensity distribution and embedded fusion fraction of D- 3 He fusion reaction rate in an IEC device, we used a proton counting system with a solid state detector (SSD) and circular collimator masks of three different diameters on a linearly movable rod set between the SSD and the IEC chamber. Using this device, the intensity distribution of D- 3 He fusion reaction rate was obtained by analyzing the experimental results with ML-EM (Most Likelihood-Expectation Maximization) method, commonly utilized in CT scanning. The results showed volumetric production of the 14.7 MeV protons within and nearby the cathode grids (57 %), and embedded fusion on the six rings (43 %). In this study, the error margin of last year s result was evaluated by adding the range of measurement error based on Poisson distribution and reconstructing to ML-EM method. As a result of that, the contribution within and nearby the cathode grids has about 30% or less error rate, and that on the six rings became %. But a new fact has come to light that the yield on the feedthrough neglected by the assuming spherical symmetry in ML-EM method has a profound effect on the reconstruction of D- 3 He fusion distribution because of the material of the feedthrough is Mo that is same to the cathode material and the position of the feedthrough element is adjacent to the cathode area. Therefore we applied a new analysis which considers the feedthrough element beside the cathode area in ML-EM method. However with this analysis, the place of the feedthrough cannot be accurately reconstructed with the present measurement condition because of the insufficient spatial resolution around there. To cope with this problem, a new proton counting system was developed. It has a chamber between the movable SSD and the IEC to improve the spatial resolution around the feedthrough area. And the chamber has a collimator that shields much more X ray to improve S/N ratio in it. By using the improved analysis method and the new proton counting system, it was found that almost 100% D- 3 He protons generate on metal surface including cathode rings and feedthrough in the IEC device.

29 Recent Results from the LANL IEC Program R. A. Nebel, E. Evstatiev, L. Chacon, G. Lapenta, J. Park Los Alamos National Laboratory Los Alamos, New Mexico Theoretical works by Barnes and Nebel 1,2 have suggested that a tiny oscillating ion cloud may undergo a self-similar collapse in a harmonic oscillator potential formed by a uniform electron background. One issue for this concept is how much plasma compression can be achieved by the POPS oscillations. Recent work 3 has shown that by properly programming the distribution function of the injected electrons it is possible to significantly improve the space charge neutralization and the plasma compression. This paper extends that previous work in a systematic fashion by developing a formalism that determines the required velocity distribution of the injected electrons so space charge neutralization can be achieved. This formalism is then included as a boundary condition in a griddles particle code. Results indicate that although the formalism works well during the early phases of compression, when the compression gets large the solution bifurcates and becomes unphysical. 1. R. A. Nebel, D. C. Barnes, Fusion Technology 38, 28 (1998). 2. D. C. Barnes, R. A. Nebel, Physics of Plasmas 5, 2498 (1998). 3. J. Park, R. A. Nebel, S. Stange, S. K. Murali, Physics of Plasmas 12, (2005).