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Ultrafast terawatt laser sources for high-field particle acceleration and short wavelength generation

Description: The Laser Sources working group concerned itself with recent advances in and future requirements for the development of laser sources relevant to high-energy physics (HEP) colliders, small scale accelerators, and the generation of short wave-length radiation. We heavily emphasized pulsed terawatt peak power laser sources for several reasons. First, their development over the past five years has been rapid and multi-faceted, and has made relativistic light intensity available to the advanced accelerator community, as well as the wider physics community, for the first time. Secondly, they have strongly impacted plasma-based accelerator research over the past two years, producing the first experimental demonstrations of the laser wakefield accelerator (LWFA) in both its resonantly-driven and self-modulated forms. Thirdly, their average power and wall-plug efficiency currently fall well short of projected requirements for future accelerators and other high average power applications, but show considerable promise for improving substantially over the next few years. A review of this rapidly emerging laser technology in the context of advanced accelerator research is therefore timely.
Date: December 31, 1996
Creator: Downer, M.C. & Siders, C.W.
Partner: UNT Libraries Government Documents Department

Induction linacs and pulsed power

Description: Progress in electronic power conversion technology is making possible a new class of induction linacs that can operate at extremely high repetition rates. Advances in insulator technology, pulse forming line design and switching may also lead to a new type of high current accelerator with accelerating gradients at least an order of magnitude greater than those attainable today. The evolution of the induction accelerator pulsed power system will be discussed along with some details of these emerging technologies which are at the frontiers of accelerator technology.
Date: July 11, 1995
Creator: Caporaso, G.J.
Partner: UNT Libraries Government Documents Department

Results of Russian/US high performance DEMG experiment

Description: In November 1992, the AU Russian Scientific Research Institute of Experimental Physics (VNIIEF), Arzamas-16, Russia and the Los Alamos National Laboratory, Los Alamos NM, USA embarked on a historic effort to conduct a joint explosive pulse-power experiment. With the concurrence of the Ministry of Atomic Energy (Russia) and the Department of Energy (USA), the two laboratories, entered into a Laboratory-to-Laboratory collaboration in the areas of very high energy pulse-power and ultrahigh magnetic fields in order to explore problems of mutual scientific interest. The first experiment to be planned was an explosively powered, fast, high-current pulse-power system demonstration. The experiment used a flux compressor, inductive store, and high-current opening switch to demonstrate the feasibility of supplying many megajoules of electrical energy, on microsecond time scales, to high energy density physics experiments. The experiment was conducted in Arzamas-16 on September 22, 1993.
Date: December 1, 1996
Creator: Buyko, A.M.; Bidylo, N.P.; Chernyshev, V.K. & Demidov, V.A.
Partner: UNT Libraries Government Documents Department

An all solid state pulse power source for high PRF induction accelerators

Description: Researchers at the Lawrence Livermore National Laboratory (LLNL) are developing a flexible, all solid-state pulsed power source that will enable an induction accelerator to produce mulitkiloampere electron beams at a maximum pulse repetition frequency (prf) of 2 MHz. The prototype source consists of three, 15-kV, 4.8-kA solid-state modulators stacked in an induction adder configuration. Each modulator contains over 1300 field-effect transistors (FETs) that quickly connect and disconnect four banks of energy storage capacitors to a magnetic induction core. The FETs are commanded on and off by an optical signal that determines the duration of the accelerating pulse. Further electronic circuitry is provided that resets the magnetic cores in each modulator immediately after the accelerating pulse. The system produces bursts of five or more pulses with an adjustable pulse width that ranges from 200 ns to 2 {micro}s The pulse duty factor within a burst can be as high as 25% while still allowing time for the induction core to reset. The solid-state modulator described above is called ARM-II and is named for the Advanced Radiographic Machine (ARM)-a powerful radiographic accelerator that will be the principal diagnostic device for the future Advanced Hydrotest Facility (AHF).
Date: June 1998
Creator: Kirbie, H.
Partner: UNT Libraries Government Documents Department

Basic science with pulsed power & some off-the-wall ideas

Description: This paper discusses aspects of pulsed power for use in basic research, with a principal emphasis on ATLAS, a planned 36-MJ pulsed-power machine with a circular architechture designed primarily for z-pinch implosion of cylindrical foils. The objective of the paper is to give an overview and touch on subjects which might test the limits of this technology.
Date: April 1, 1995
Creator: Solem, J.C.
Partner: UNT Libraries Government Documents Department

Design of a 1-MV induction injector for the Relativistic Klystron Two-Beam Accelerator

Description: A Relativistic Klystron Two-Beam Accelerator (RK-TBA) is envisioned as a rf power source upgrade of the Next Linear Collider. Construction of a prototype, called the RTA, based on the RK-TBA concept has commenced at the Lawrence Berkeley National Laboratory. This prototype will be used to study physics, engineering, and costing issues involved in the application of the RK-TBA concept to linear colliders. The first half of the injector, a 1 MeV, 1.2 kA, 300 ns induction electron gun, has been built and is presently being tested. The design of the injector cells and the pulsed power drive units are presented in this paper.
Date: May 1, 1997
Creator: Anderson, D.E.; Eylon, S.; Lidia, S.; Reginato, L.; Vanecek, D.; Yu, S. et al.
Partner: UNT Libraries Government Documents Department

Development of the pulse transformer for NLC klystron pulse modulator

Description: We have studied a conventional pulse transformer for the NLC klystron pulse modulator. The transformer has been analyzed using a simplified lumped circuit model. It is found that a fast rise time requires low leakage inductance and low distributed capacitance and can be realized by reducing the number of secondary turns, but it produces larger pulse droop and core size. After making a tradeoff among these parameters carefully, a conventional pulse transformer with a rise time of 250ns and pulse droop of 3.6% has been designed and built. The transmission characteristics and pulse time-response were measured. The data were compared with the model. The agreement with the model was good when the measured values were used in the model simulation. The results of the high voltage tests are also presented.
Date: May 1, 1997
Creator: Akemoto, M.; Gold, S.; Koontz, R. & Krasnykh, A.
Partner: UNT Libraries Government Documents Department

Caballero: A high current flux compressor system for 100 MJ solid liner experiments

Description: Pulse power systems delivering in excess of 100 MJ represent one of the next major challenges to the pulse power community. While a laboratory pulse power system in this energy range if feasible, it represents a very substantial investment of both time and resources. Prudence requires that fundamental proof-of-principle for the contemplated application is established before such massive resources are committed. Explosive pulse power systems using magnetic flux compression provide a direct path to such demonstrations. Furthermore, as energy requirements grow, single use explosive systems may represent the only affordable source of ultra-high energy environments.
Date: November 1, 1997
Creator: Reinovsky, R.E.; Lindemuth, I.R.; Lopez, E.A.; Goforth, J.H. & Marsh, S.P.
Partner: UNT Libraries Government Documents Department

Data acquisition techniques for explosive high current generators

Description: The Hydrodynamic and X-Ray Physics Group (P-22) at Los Alamos National Laboratory has developed hardware, software, and procedures to work with explosively driven high current generators to obtain time resolved data. Data recording in this physically and electrically harsh environment requires special equipment, techniques, and processes. There are three distinct areas of consideration to record this class of data. First is the explosive shot pad area, second is bunker area, and third is the data handling and documentation considerations. It is well within the capability of P-22 to provide 100 to 200 data recording channels and to provide 50 to 100 fiber optic data paths to the recording area. The equipment has high frequency bandwidths from 20 MHz to 500 MHz. This work has been conducted in various sites in the United States and Russia. The work in Russia presents a particular challenge in the areas of planning for the change in AC power voltage and frequency, different coaxial and connector systems, making sure all components and spare equipment are included in the equipment shipped before the experiment.
Date: October 1, 1997
Creator: Petersen, T.L.; Allred, G.D. & Anderson, B.G.
Partner: UNT Libraries Government Documents Department

The pulse modulator for the mod-anode of the cluster klystron

Description: A high voltage pulse generator using a Zarem type modulator was developed. The Zarem type circuit doesn`t require a matched load, making it suitable to drive the mod-anode of the cluster klystron, which has a capacitive load. The principle and the experiments, as well as the analyses and the simulations of the observed phenomena, (ringing, pulse {open_quotes}skirt{close_quotes} and {open_quotes}deficiency{close_quotes}) are presented.
Date: May 1, 1996
Creator: Zhao, Y.; Palmer, R. & Wang, H.
Partner: UNT Libraries Government Documents Department

High Breakdown Strength, Multilayer Ceramics for Compact Pulsed Power Applications

Description: Advanced ceramics are being developed for use in large area, high voltage devices in order to achieve high specific energy densities (>10 6 J/m 3 ) and physical size reduction. Initial materials based on slip cast TiO2 exhibited a high bulk breakdown strength (BDS >300 kV/cm) and high permittivity with low dispersion (e�100). However, strong area and thickness dependencies were noted. To increase the BDS, multilayer dielectric compositions are being developed based on glass/TiO2 composites. The addition of glass increases the density (�99.8% theoretical), forms a continuous grain boundary phase, and also allows the use of high temperature processes to change the physical shape of the dielectric. The permittivity can also be manipulated since the volume fraction and connectivity of the glassy phase can be readily shifted. Results from this study on bulk breakdown of TiO2 multilayer structures with an area of 2cm 2 and 0.1cm thickness have measured 650 kV/cm. Furthermore, a strong dependence of breakdown strength and permittivity has been observed and correlated with microstructure and the glass composition. This paper presents the interactive effects of manipulation of these variables.
Date: July 20, 1999
Creator: Gilmore, B.; Huebner, W.; Krogh, M.L.; Lundstrom, J.M.; Pate, R.C.; Rinehart, L.F. et al.
Partner: UNT Libraries Government Documents Department

A High Power Linear Solid State Pulser

Description: Particle Accelerators require high voltage and often high power. Typically the high voltage/power generation utilizes a topology with an extra energy store and a switching means to extract that stored energy. The switches may be active or passive devices. Active switches are hard or soft vacuum tubes, or semiconductors. When required voltages exceed tens of kilovolts, numerous semiconductors are stacked to withstand that potential. Such topologies can use large numbers of critical parts that, when in series, compromise the system reliability and performance. This paper describes a modular, linear, solid state amplifier which uses a parallel array of semiconductors, coupled with transmission line transformers. Such a design can provide output signals with voltages exceeding 10kV (into 50-ohms), and with rise and fall times (10-90 % amplitude) that are less than 1--ns. This compact solid state amplifier is modular, and has both hot-swap and soft fail capabilities.
Date: April 1, 1999
Creator: Yen, Boris; Davis, Brent & Booth, Rex
Partner: UNT Libraries Government Documents Department

Photonic Power Delivery Through Optical Fiber Using Very High Power Laser Diode Arrays

Description: Described is a system that will provide isolated electric power for a circuit that drives the core reset of a pulsed power modulator. This can be accomplished by coupling light from a number of diode laser bars to bundles of 200 um multimode optical fibers. This is then coupled to photo-voltaic power converters that will deliver 16 V 29mA of electricity from 1 watt of optical power. Spot size at the bundle face is a Gausian ellipse with a major axis of 1.4 mm radius and a minor axis of four bundles of 12 fibers generating a total of 24 W of electrical power. Various schemes are used to maximize coupling into the optical filber while limiting the number of optical components, and comparing components such as fresnel and aspheric lenses and lens ducts for effectiveness and cost. This will provide a completely isolated low power source for high voltage, high current environments where tradional isolation techniques yield inadequate isolation or prove too cumbersome.
Date: May 1, 1999
Creator: Heino, Matthew & Saethre, Robert
Partner: UNT Libraries Government Documents Department


Description: There has been a lot of interest in compact sources of high brightness, relativistic electron beams. One approach for developing such a source is to apply a high gradient that remains constant during the generation and acceleration of the electron beam. In this paper, we describe high voltage pulse generators that deliver up to 5 MV with 1 ns pulse duration. These devices are synchronizable to an external trigger with jitter of {approx}0.5 ns and can establish gradients in excess of 1 GV/m between two electrodes without breakdown. In the presence of field gradients up to 0.5 GV/m, electron beams of bunch lengths ranging from 1 ns to 0.3 ps and diameter < 300 {micro}m have been generated by irradiating the cathode with UV lasers. Characteristics of these electron beams as well as those produced via field emission at gradients up to 1 GV/m will be discussed.
Date: November 12, 2002
Partner: UNT Libraries Government Documents Department

Variation of high-power aluminum-wire array Z-pinch dynamics with wire number, array radius, and load mass

Description: A systematic study of annular aluminum-wire z-pinches on the Saturn accelerator shows that the quality of the implosion, including the radiated power, increases with wire number. Radiation magnetohydrodynamic (RMEC) xy simulations suggest that the implosion transitions from that of individual wire plasmas to that of a continuous plasma shell when the interwire spacing is reduced below {approximately} 1.4 mm. In the plasma-shell regime, the experimental implosions exhibit 1D- and 2D-code characteristics as evidenced by the presence of a strong first and a weak second radiation pulse that correlates with a strong and weak radial convergence. In this regime, many of the radiation and plasma characteristics are in agreement with those simulated by 2D-RMHC rz simulations. Moreover, measured changes in the radiation pulse width with variations in array mass and radius are consistent with the simulations and are explained by the development of 2D fluid motion in the rz plane. Associated variations in the K-shell yield are qualitatively explained by simple K-shell radiation scaling models.
Date: June 1, 1997
Creator: Sanford, T.W.L.; Mock, R.C. & Marder, B.M.
Partner: UNT Libraries Government Documents Department

A high voltage pulse generator for the mod-anode of the cluster klystron

Description: A high voltage pulse generator using Zarem type was developed. The advantage of the Zarem type circuit is that it does not require a matched load. In our case the purser is dedicated to drive a mod-anode, which is a capacitive load. Therefore the Zarem type circuit is desirable. This report addresses systematically the R & D work, including the basic Principle and the designing consideration, the low voltage and high voltage experiments. A lot of irregular phenomena were observed, including ringing, pulse ``skirt`` and ``deficiency``. Also addressed are the analyses, simulation and solutions.
Date: October 1, 1995
Creator: Zhao, Yongxiang & Wang, Hai-peng
Partner: UNT Libraries Government Documents Department

Proposed inductive voltage adder based accelerator concepts for the second axis of DARHT

Description: As participants in the Technology Options Study for the second axis of the Dual Axis Radiographic HydroTest (DARHT) facility located at Los Alamos National Laboratories, the authors have considered several accelerator concepts based on the Inductive Voltage Adder (IVA) technology that is being used successfully at Sandia on the SABRE and HERMES-III facilities. The challenging accelerator design requirements for the IVA approach include: {ge}12-MeV beam energy; {approximately}60-ns electrical pulse width; {le}40-kA electron beam current; {approximately}1-mm diameter e-beam; four pulses on the same axis or as close as possible to that axis; and an architecture that fits within the existing building envelope. To satisfy these requirements the IVA concepts take a modular approach. The basic idea is built upon a conservative design for eight ferromagnetically isolated 2-MV cavities that are driven by two 3 to 4-{Omega} water dielectric pulse forming lines (PFLs) synchronized with laser triggered gas switches. The 100-{Omega} vacuum magnetically insulated transmission line (MITL) would taper to a needle cathode that produces the electron beam(s). After considering many concepts the authors narrowed their study to the following options: (A) Four independent single pulse drivers powering four single pulse diodes; (B) Four series adders with interleaved cavities feeding a common MITL and diode; (C) Four stages of series PFLs, isolated from each other by triggered spark gap switches, with single-point feeds to a common adder, MITL, and diode; and (D) Isolated PFLs with multiple-feeds to a common adder using spark gap switches in combination with saturable magnetic cores to isolate the non-energized lines. The authors will discuss these options in greater detail identifying the challenges and risks associated with each.
Date: June 1, 1997
Creator: Smith, D.L.; Johnson, D.L. & Boyes, J.D.
Partner: UNT Libraries Government Documents Department

Very fast kicker for accelerator applications

Description: We describe a very fast counter traveling wave kicker with a full pulse width of about 7 ns. Successful test experiment has been done with hi-tech semiconductor technology FET pulse generator with a MHz- range repetition rates and maximum kick strength of the order of 3 G{center_dot}m. Further. increase of the strength seems to be quite possible with the FET pursers, that makes the kicker to be very useful tool for bunch-by-bunch injection/extraction and other accelerator applications.
Date: November 1, 1996
Creator: Grishanov, B.I.; Podgorny, F.V.; Ruemmler, J. & Shiltsev, V.D.
Partner: UNT Libraries Government Documents Department

Pulse power for high energy density physics experiments

Description: Pulse power technology has been supported and developed in the US over the last 4 decades by the Department of Energy in support of the nuclear weapons and energy research programs, and by the Department of Defense for advanced weapons technology and nuclear weapons effects research. Recent, changes in the priorities and orientation of these programs have made the planning and conduct of basic science experiments possible using facilities heretofore completely dedicated to a more narrow range of experimental activities. The purpose of the `Spring Workshop on Basic Science Using Pulsed Power` is to introduce high performance pulse power technology to a broader cross-section of the community and to discuss, with the community, experiments which can be planned now using currently operating systems and to begin to consider experiments which can be planned for the systems of the future.
Date: May 1, 1995
Creator: Reinovsky, R.E.
Partner: UNT Libraries Government Documents Department

Longevity of optically activated, high gain GaAs photoconductive semiconductor switches

Description: The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to well over 10 million pulses by reducing the density of carriers at the semiconductor to metal interface. This was achieved by reducing the density in the vertical and lateral directions. The first was achieved by varying the spatial distribution of the trigger light thereby widening the current filaments that are characteristic of the high gain switches. The authors reduced the carrier density in the vertical direction by using ion implantation. These results were obtained for currents of about 10 A, current duration of 3.5 ns, and switched voltage of {approximately}2 kV. At currents of {approximately}70 A, the switches last for 0.6 million pulses. In order to improve the performance at high currents new processes such as deep diffusion and epitaxial growth of contacts are being pursued. To guide this effort the authors measured a carrier density of 6 x 10{sup 18} electrons (or holes)/cm{sup 3} in filaments that carry a current of 5 A.
Date: August 1, 1997
Creator: Loubriel, G.M.; Zutavern, F.J. & Mar, A.
Partner: UNT Libraries Government Documents Department

Compact high-voltage structures

Description: A basic understanding of the critical issues limiting the compactness of high-voltage systems is required for the next generation of impulse generators. In the process of optimizing the design of a highly reliable solid-dielectric over-voltage switch, an understanding of the limiting factors found are shown. Results of a l3O kV operating switch, having a modest field enhancement of 16% above the average field stress in the switching region, are reported. The resulting high reliability is obtained by reducing the standard deviation of the switch to 6.8%. The total height of the switch is 1 mm. The resulting operating parameters are obtained by controlling field distribution across the entire switch package and field shaping the desired point of switch closure. The disclosed field management technique provides an approach to improve other highly stressed components and structures.
Date: June 9, 1997
Creator: Wilson, M. J. & Goerz, D.A.
Partner: UNT Libraries Government Documents Department

Pegasus II experiments and plans for the Atlas pulsed power facility

Description: Atlas will be a high-energy (36 MJ stored), high-power ({approximately} 10 TW) pulsed power driver for high energy-density experiments, with an emphasis on hydrodynamics. Scheduled for completion in late 1999, Atlas is designed to produce currents in the 40-50 MA range with a quarter-cycle time of 4-5 {mu}s. It will drive implosions of heavy liners (typically 50 g) with implosion velocities exceeding 20 mm/{mu}s. Under these conditions very high pressures and magnetic fields are produced. Shock pressures in the 50 Mbar range and pressures exceeding 10 Mbar in an adiabatic compression will be possible. By performing flux compression of a seed field, axial magnetic fields in the 2000 T range may be achieved. A variety of concepts have been identified for the first experimental campaigns on Atlas. These experiments include Rayleigh-Taylor instability studies, convergent (e.g., Bell-Plesset type) instability studies, material strength experiments at very high strain and strain rate, hydrodynamic flows in 3-dimensional geometries, equation of state measurements along the hugoniot and adiabats, transport and shock propagation in dense strongly-coupled plasmas, and atomic and condensed matter studies employing ultra-high magnetic fields. Experimental configurations, associated physics issues, and diagnostic strategies are all under investigation as the design of the Atlas facility proceeds. Near-term proof-of-principle experiments employing the smaller Pegasus II capacitor bank have been identified, and several of these experiments have not been performed. This paper discusses a number of recent Pegasus II experiments and identifies several areas of research presently planned on Atlas.
Date: September 1, 1997
Creator: Shlachter, J.S.; Adams, P.J. & Atchison, W.L.
Partner: UNT Libraries Government Documents Department

Electrical performance of a three-stage flux compression generator system

Description: In previous papers at prior Megagauss Conferences, we have described the design and performance of two stage FCG pulsed power packages. This paper extends the effort to a three stage pulsed power package that increases the power amplification and versatility of the self contained packages. The first tow stages are helical FCGs. The second stage is energized by using a magnetic coil connected to the first FCG. The coupling technique is similar in concept to the cascaded devices previously demonstrated by A.I. Pavlovski, but uses a more direct coupling geometry. The third generator is a fast operating plate generator that produces a one microsecond long pulse. The plate generator output is coupled to the high impedance load to provide better impedance matching. The design and performance of a three stage FCG pulsed power package into a high impedance load is described.
Date: September 1, 1996
Creator: Hoeberling, R.F.; Fowler, C.M.; Freeman, B.L.; King, J.C.; Vorthman, J.E. & Wheeler, R.B.
Partner: UNT Libraries Government Documents Department