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A Linear hybrid kicker modulator for ETA-II

Description: A new type of pulse modulator is being developed at Livermore that will rapidly split a high current electron beam into two halves, enabling each half to proceed along separate pathways. Each modulator will be capable of applying a {+-}10kV, 200A pulse onto a transmission line electrode structure with a rise time less than 10 ns, a pulse repetition frequency greater than 1 MHz, and a maximum pulse duration of 400 ns. The electrode structure, located inside the beam-transport pipe, generates an electromagnetic field that acts on part of the original beam to ``kick`` it in another direction. The true merit of this high-speed modulator will be its flexibility in pulse duration and shape. The electrodynamics involved in altering the beam`s trajectory require the modulator to generate a time-varying pulse that is precisely tailored in amplitude. Consequently, the modulator is driven by an arbitrary waveform generator and must act more as a linear amplifier than as a simple switch. The requirements of high peak power and wide analog bandwidth (about 50 MHz) will be addressed by merging a solid-state driver with an output stage of high-power vacuum tubes. Modulator development and performance data will be presented as will the issues of beam-induced voltage and transit-time isolation that are considered when driving a beam load.
Date: June 29, 1997
Creator: Buckles, R.; Davis, B. & Yen, B.
Partner: UNT Libraries Government Documents Department

Pulse transformer R and D for NLC klystron pulse modulator

Description: The authors 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 requires a larger core size. After making a tradeoff among these parameters carefully, a conventional pulse transformer with a rise time of 250ns and a 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 using a klystron load are also presented.
Date: July 1, 1997
Creator: Akemoto, M.; Gold, S.; Krasnykh, A. & Koontz, R.
Partner: UNT Libraries Government Documents Department

Plastic Laminate Pulsed Power Development

Description: The desire to move high-energy Pulsed Power systems from the laboratory to practical field systems requires the development of compact lightweight drivers. This paper concerns an effort to develop such a system based on a plastic laminate strip Blumlein as the final pulseshaping stage for a 600 kV, 50ns, 5-ohm driver. A lifetime and breakdown study conducted with small-area samples identified Kapton sheet impregnated with Propylene Carbonate as the best material combination of those evaluated. The program has successfully demonstrated techniques for folding large area systems into compact geometry's and vacuum impregnating the laminate in the folded systems. The major operational challenges encountered revolve around edge grading and low inductance, low impedance switching. The design iterations and lessons learned are discussed. A multistage prototype testing program has demonstrated 600kV operation on a short 6ns line. Full-scale prototypes are currently undergoing development and testing.
Date: September 1, 2000
Partner: UNT Libraries Government Documents Department

Pulsed power supply for PAR injection/extraction septum magnet

Description: A 22.5 {mu}H, 22.5 m{Omega} transformer septum magnet must be pulsed at a 60 Hz rate to inject beam from a 450 MeV positron linac into a positron accumulator ring (PAR) and to extract beam from it. Of the 60 pulses per second the first 24 are used for injection and the 30th for extraction. The 25th through the 29th are not used. This pattern is repeated continuously. A design study was performed of the power supply proposed in the APS Title I design. This supply produces a pulse that is approximately a half-sine-wave with a base width of approximately 1/3 ms; its peak current is adjustable from 3.5kA to 4.7kA and is repeatable within {+-}0.05%. The septum steel is reset by a half-sine pulse of reverse polarity a few milliseconds after the forward current pulse. No beam is present during reset. The use of the transformer design minimizes the cost of the capacitors used for energy storage.
Date: September 23, 1990
Creator: McGhee, D.G.
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

Prospectus of ignition enhancement in a two-stroke SI engine

Description: Conventional two-stroke spark-ignition (SI) engines have difficulty meeting the ignition requirements of lean fuel-air mixtures and high compression ratios, due to their breaker operated, magneto-coil ignition systems. In the present work, a breakerless, high-energy electronic ignition system was developed and tested with and without a platinum-tipped electrode spark plug. The high-energy ignition system showed an improved lean-burn capability at high compression ratios relative to the conventional ignition system. At a high compression ratio of 9:1 with lean fuel-air mixtures, the maximum percentage improvement in the brake thermal efficiency was about 16.5% at 2.7 kW and 3000 rpm. Cylinder peak pressures-were higher ignition delay was lower, and combustion duration was shorter at both normal and high compression ratios. Combustion stability as measured by the coefficient of variation in peak cylinder pressure was also considerably improved with the high-energy ignition system.
Date: December 1, 1995
Creator: Manivannan, P.V.; Ramesh, A.; Poola, R.B. & Dhinadgar, S.J.
Partner: UNT Libraries Government Documents Department

Advanced power conversion based on the Aerocapacitor{trademark}

Description: The authors report here, for the first time, high frequency testing of a new type of electrochemical double layer capacitor (EDLC), based on carbon aerogels: the Aerocapacitor. Carbon aerogels, are a novel type of carbon foam developed by Lawrence Livermore National Laboratory for military applications. The unique properties of carbon aerogels, high surface area (700 m{sup 2}/g), high density (1g/cc), well controlled pore diameter and high material conductivity (25 S/cm) made it an ideal EDLC electrode material. Using carbon aerogel as the electrode material, the authors have developed Aerocapacitors. These new EDLC`s have a frequency response comparable to that of aluminum electrolytic capacitors and are thus ideally suited to power conversion applications.
Date: October 1997
Creator: Josephs, L. C.; Gregory, D. & Roark, D.
Partner: UNT Libraries Government Documents Department

The Ranchero explosive pulsed power system

Description: The authors are currently developing a high explosive pulsed power system concept that they call Ranchero. Ranchero systems consist of series-parallel combinations of simultaneously initiated coaxial magnetic flux compression generators, and are intended to operate in the range from 50 MA to a few hundred MA currents. One example of a Ranchero system is shown here. The coaxial modules lend themselves to extracting the current output either from one end or along the generator midplane. They have previously published design considerations related to the different module configurations, and in this paper they concentrate on the system that they will use for their first imploding liner tests. A single module with end output. The module is 1.4-m long and expands the armature by a factor of two to reach the 30-cm OD stator. The first heavy liner implosion experiments will be conducted in the range of 40--50 MA currents. Electrical tests, to date, have employed high explosive (HE) charges 43-cm long. They have performed tests and related 1D MHD calculations at the 45-MA current level with small loads. From these results, they determine that they can deliver currents of approximately 50 MA to loads of 8 nH.
Date: September 1, 1997
Creator: Goforth, J.H.; Atchison, W.L. & Bartram, D.E.
Partner: UNT Libraries Government Documents Department

Development of solid-state induction modulators for high PRF accelerators

Description: Researchers at the Lawrence Livermore National Laboratory and EG&G Energy Measurements are developing a new solid-state power system for two proposed accelerators. One of the accelerators is a circular arrangement of induction cells called a recirculator. It is designed to accelerate heavy ions for an inertial fusion study that proposes to substitute heavy-ion beams for laser beams as the driver for fusion targets. The other accelerator is a linear induction accelerator for electron beams called the Advanced Radiographic Machine (ARM). Both accelerators require their induction cells to be pulsed at a very high repetition frequency (prf) for a short burst containing 5 to 15 pulses. The recirculator has a pulse schedule that varies in pulse width from 1 {mu}s to 400 ns and in prf from 50 to 150 kHz. The ARM accelerator has a pulse schedule that varies in pulse width from 1 {mu}s to 200 ns and in prf from 150 kHz to 1 MHz. The need for complex pulse agility in these accelerators led the authors to examine solid-state switching components that have an on/off capability. The intrinsic speed of solid-state switching satisfies the high prf requirements, while the on/off switching action of some semiconductor devices enables the authors to select an arbitrary pulse width. To accommodate these requirements, they selected field effect transistors (FETs) as the preferred switching elements. The same FET switching technology applies to both accelerators due to their similar pulse requirements. However, these two accelerators differ greatly in peak power and prf range. For example, the power system for the ARM accelerator must supply over 3 kA of beam-current loading to a 150-kV induction cell. For the authors research, two full-scale prototypes were built - a 5-kV induction recirculator cell and a single 15-kV induction modulator for the ARM accelerator. The authors discuss ...
Date: July 5, 1995
Creator: Kirbie, H.; Hawkins, S. & Hickman, B.
Partner: UNT Libraries Government Documents Department

Inductive-storage pulse-circuit device

Description: Inductive storage pulse circuit device is disclosed which is capable of delivering a series of electrical pulses to a load in a sequential manner. Silicon controlled rectifiers as well as spark gap switches can be utilized in accordance with the present invention. A commutation switching array is utilized to produce a reverse current to turn-off the main opening switch. A commutation capacitor produces the reverse current and is initially charged to a predetermined voltage and subsequently charged in alternating directions by the inductive storage current.
Date: January 21, 1982
Creator: Parsons, W.M. & Honig, E.M.
Partner: UNT Libraries Government Documents Department

Applications of a versatile new instrument module

Description: The authors have found a number of interesting applications for the Pulse Arrival Time Recording Module (PATRM). This CAMAC module is capable of recording the arrival time of up to 4 million pulses. The result is a list of 32-bit binary numbers in which each number represents the arrival time of a single pulse expressed in terms of the number of {open_quotes}ticks{close_quotes} of a 10MHz clock which have elapsed since the beginning of the count. The versatility arises from the fact that the data list can be analyzed by whatever algorithm the authors can put into software, and that they can {open_quotes}play it back{close_quotes} as many times as desired. The authors already have the following applications: (1) Neutron multiplicity counting in waste assay. (2) Study of dead-time recovery and double pulsing in individual channels. (3) Auto-correlation analysis for Rossi-{alpha} measurements in critical systems. (4) Variable channel width multichannel scaler for delayed neutron counting. (5) Cross-correlation analysis and conventional multi-scaling. (6) Time dependent multiplicity measurements during neutron interrogation. The authors expect in the coming year to test an updated version of the PATRM which will incorporate a 100MH clock and label each pulse with the channel from which it came. The device will be configured as a single PC card installable in any high performance IBM type computer.
Date: March 1, 1997
Creator: Brunson, G.S. & Arnone, G.J.
Partner: UNT Libraries Government Documents Department

A low-power, CMOS peak detect and hold circuit for nuclear pulse spectroscopy

Description: A low-power CMOS peak detecting track and hold circuit optimized for nuclear pulse spectroscopy is presented. The circuit topology eliminates the need for a rectifying diode, reducing the effect of charge injection into the hold capacitor, incorporates a linear gate at the input to prevent pulse pileup, and uses dynamic bias control that minimizes both pedestal and droop. Both positive-going and negative-going pulses are accommodated using a complementary set of track and hold circuits. Full characterization of the design fabricated in 1.2{mu}m CMOS including dynamic range, integral nonlinearity, droop rate, pedestal, and power measurements is presented. Additionally, analysis and design approaches for optimization of operational characteristics are discussed.
Date: December 31, 1994
Creator: Ericson, M.N.; Simpson, M.L.; Britton, C.L.; Allen, M.D.; Kroeger, R.A. & Inderhees, S.E.
Partner: UNT Libraries Government Documents Department

Magnetic switches and circuits

Description: This report outlines the use of saturable inductors as switches in lumped-element, magnetic-pulse compression circuits is discussed and the characteristic use of each is defined. In addition, the geometric constraints and magnetic pulse compression circuits used in short-pulse, low-inductance systems are considered. The scaling of presaturation leakage currents, magnetic energy losses, and switching times with geometrical and material parameters are developed to aid in evaluating magnetic pulse compression systems in a particular application. Finally, a scheme for increasing the couping coefficient in saturable stripline transformers is proposed to enable their use in the short-pulse, high-voltage regime.
Date: May 1, 1982
Creator: Nunnally, W.C.
Partner: UNT Libraries Government Documents Department

Development and evaluation of systems for controlling parallel high di/dt thyratrons

Description: Increasing numbers of high power, high repetition rate applications dictate the use or thyratrons in multiple of hard parallel configurations to achieve the required rate of current rise, di/dt. This in turn demands the development of systems to control parallel thyratron commutation with nanosecond accuracy. Such systems must be capable of real-time, fully-automated control in multi-kilohertz applications while still remaining cost effective. This paper describes the evolution of such a control methodology and system.
Date: January 1, 1982
Creator: A., Litton. & McDuff, G.
Partner: UNT Libraries Government Documents Department

Feedback threshold control extends pulse rate measurements into the pileup region

Description: By using feedback control of the discrimination threshold we have added 4 to 6 decades to the useful range of otherwise conventional pulse counting systems. The additional range is obtained at the high end by retarding saturation of the output count rate with higher threshold levels. We have implemented the method with low-power microcircuits that provide a 9-decade range (10/sup -5/ to 10/sup 4/ R/h) without the need for range or mode switching.
Date: January 1, 1986
Creator: Valentine, K.H.; Kopp, M.K. & Williams, J.A.
Partner: UNT Libraries Government Documents Department

A Solid-State Nanosecond Beam Kicker Modulator Based on the DSRD Switch

Description: A fast solid-state beam kicker modulator is under development at the SLAC National Accelerator Laboratory. The program goal is to develop a modulator that will deliver 4 ns, {+-}5 kV pulses to the ATF2 damping ring beam extraction kicker. The kicker is a 50 {Omega}, bipolar strip line, 60 cm long, fed at the downstream end and terminated at the upstream end. The bunch spacing in the ring is 5.6 ns, bunches are removed from the back end of the train, and there is a gap of 103.6 ns before the next train. The modulator design is based on an opening switch topology that uses Drift Step Recovery Diodes as the opening switches. The design and results of the modulator development are discussed. There are many applications that benefit from very fast high power switching. However, at MW power levels and nanosecond time scales, solid state options are limited. One option, the Drift Step Recovery Diode (DSRD) has been demonstrated as capable of blocking thousands of volts and switching in nanosecond to sub-nanosecond ranges. When used as an opening switch, the DSRD exhibits a very fast turn off transient. The process is described in detail by its pioneers in [5,6]. In essence, charge is pumped into and then extracted from the DSRD under pulsed conditions. The turn off transient occurs precisely when the pumped charge is equal to the extracted charge and the DSRD is switched off. At the SLAC National Accelerator Laboratory, a DSRD is being used as an opening switch in the development of a fast kicker modulator. The modulator is designed to create {+-}5kV pulses with <1ns rise and fall time on a 50{Omega} strip line kicker. As is common in beam optics, the absence of power in the kicker before and after the pulse is very ...
Date: August 19, 2011
Creator: Akre, R.; Benwell, A.; Burkhart, C.; Krasnykh, A.; Tang, T.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Energy losses in switches

Description: The authors experiments show energy losses between 2 and 10 times that of the resistive time predictions. The experiments used hydrogen, helium, air, nitrogen, SF{sub 6} polyethylene, and water for the switching dielectric. Previously underestimated switch losses have caused over predicting the accelerator outputs. Accurate estimation of these losses is now necessary for new high-efficiency pulsed power devices where the switching losses constitute the major portion of the total energy loss. They found that the switch energy losses scale as (V{sub peak}I{sub peak}){sup 1.1846}. When using this scaling, the energy losses in any of the tested dielectrics are almost the same. This relationship is valid for several orders of magnitude and suggested a theoretical basis for these results. Currents up to .65 MA, with voltages to 3 MV were applied to various gaps during these experiments. The authors data and the developed theory indicates that the switch power loss continues for a much longer time than the resistive time, with peak power loss generally occurring at peak current in a ranging discharge instead of the early current time. All of the experiments were circuit code modeled after developing a new switch loss version based on the theory. The circuit code predicts switch energy loss and peak currents as a function of time. During analysis of the data they noticed slight constant offsets between the theory and data that depended on the dielectric. They modified the plasma conductivity for each tested dielectric to lessen this offset.
Date: July 1, 1993
Creator: Martin, T. H.; Seamen, J. F. & Jobe, D. O.
Partner: UNT Libraries Government Documents Department