23 Matching Results

Search Results

Advanced search parameters have been applied.

Fast SCR Thyratron Driver

Description: As part of an improvement project on the linear accelerator at SLAC, it was necessary to replace the original thyratron trigger generator, which consisted of two chassis, two vacuum tubes, and a small thyratron. All solid-state, fast rise, and high voltage thyratron drivers, therefore, have been developed and built for the 244 klystron modulators. The rack mounted, single chassis driver employs a unique way to control and generate pulses through the use of an asymmetric SCR, a PFN, a fast pulse transformer, and a saturable reactor. The resulting output pulse is 2 kV peak into 50 {Omega} load with pulse duration of 1.5 {mu}s FWHM at 180 Hz. The pulse risetime is less than 40 ns with less than 1 ns jitter. Various techniques are used to protect the SCR from being damaged by high voltage and current transients due to thyratron breakdowns. The end-of-line clipper (EOLC) detection circuit is also integrated into this chassis to interrupt the modulator triggering in the event a high percentage of line reflections occurred.
Date: June 18, 2007
Creator: Nguyen, M.N.
Partner: UNT Libraries Government Documents Department

Fast thyratron driver

Description: A fast solid-state pulse generator used as a thyratron grid driver for kicker pulsers, has been developed and built with power MOSFETs and a transmission line transformer. The MOSFET, pulsed on and off by a pair of P-N channel HEXFETs, switches charged capacitors into the transformer connected in parallel on one end and in series on the other end to step up the voltage. The resulting output pulse parameters are 2 kilovolts peak (into 50 Ohms), 13 nanoseconds risetime (10--90%), 250 nanoseconds duration, and less than 50 picoseconds pulse-to-pulse jitter. Various methods are employed to protect the MOSFETs from thyratron arc back, including the use of TransZorbs and a magnetic diode. 3 refs., 3 figs.
Date: April 1, 1991
Creator: Nguyen, M.N. & Cassel, R.L.
Partner: UNT Libraries Government Documents Department

Heats of Formation of Triplet Ethylene, Ethylidene, and Acetylene

Description: Heats of formation of the lowest triplet state of ethylene and the ground triplet state of ethylidene have been predicted by high level electronic structure calculations. Total atomization energies obtained from coupled-cluster CCSD(T) energies extrapolated to the complete basis set limit using correlation consistent basis sets (CBS), plus additional corrections predict the following heats of formation in kcal/mol: Delta H0f(C2H4,3A1) = 80.1 at 0 K and 78.5 at 298 K, and Delta H0f(CH3CH,3A") = 86.8 at 0 K and 85.1 at 298 K, with an error of less than +-1.0 kcal/mol. The vertical and adiabatic singlet-triplet separation energies of ethylene were calculated as Delta ES-T,vert = 104.1 and Delta ES-T,adia = 65.8 kcal/mol. These results are in excellent agreement with recent quantum Monte Carlo (DMC) values of 103.5 +- 0.3 and 66.4 +- 0.3 kcal/mol. Both sets of computational values differ from the experimental estimate of 58 +- 3 kcal/mol for the adiabatic splitting. The computed singlet-triplet gap at 0 K for acetylene is Delta ES-T,adia(C2H2) = 90.5 kcal/mol, which is in notable disagreement with the experimental value of 82.6 kcal/mol. The heat of formation of the triplet is Delta H0f(C2H2,3B2) = 145.3 kcal/mol. There is a systematic underestimation of the singlet-triplet gaps in recent photodecomposition experiments by ~;;7 to 8 kcal/mol. For vinylidene, we predict Delta H0f(H2CC,1A1) = 98.8 kcal/mol at 298 K (exptl. 100.3 +- 4.0), Delta H0f(H2CC,3B2) = 146.2 at 298 K, and an energy gap Delta ES-T-adia(H2CC) = 47.7 kcal/mol.
Date: June 28, 2007
Creator: Nguyen, M.T.; Matus, M.H.; Lester Jr, W.A. & Dixon, David A.
Partner: UNT Libraries Government Documents Department

A Stability of LCLS Linac Modulators

Description: Information concerning to a stability of LCLS RF linac modulators is allocated in this paper. In general a 'pulse-to-pulse' modulator stability (and RF phase as well) is acceptable for the LCLS commission and FEL programs. Further modulator stability improvements are possible and approaches are discussed based on our experimental results.
Date: June 13, 2012
Creator: Decker, F.-J.; Krasnykh, A.; Morris, B.; Nguyen, M. & /SLAC
Partner: UNT Libraries Government Documents Department

A Hierarchical Control Architecture for a PEBB-Based ILC Marx Modulator

Description: The idea of building power conversion systems around Power Electronic Building Blocks (PEBBs) was initiated by the U.S. Office of Naval Research in the mid 1990s. A PEBB-based design approach is advantageous in terms of power density, modularity, reliability, and serviceability. It is obvious that this approach has much appeal for pulsed power conversion including the International Linear Collider (ILC) klystron modulator application. A hierarchical control architecture has the inherent capability to support the integration of PEBBs. This has already been successfully demonstrated in a number of industrial applications in the recent past. This paper outlines the underlying concepts of a hierarchical control architecture for a PEBB-based Marx-topology ILC klystron modulator. The control in PEBB-based power conversion systems can be functionally partitioned into (three) hierarchical layers; system layer, application layer, and PEBB layer. This has been adopted here. Based on such a hierarchical partition, the interfaces are clearly identified and defined and, consequently, are easily characterised. A conceptual design of the hardware manager, executing low-level hardware oriented tasks, is detailed. In addition, the idea of prognostics is briefly discussed.
Date: December 15, 2011
Creator: Macken, K.; Burkhart, C.; Larsen, R.; Nguyen, M.N.; Olsen, J. & /SLAC
Partner: UNT Libraries Government Documents Department

Recent Upgrade of the Klystron Modulator at SLAC

Description: The SLAC National Accelerator Laboratory employs 244 klystron modulators on its two-mile-long linear accelerator that has been operational since the early days of the SLAC establishment in the sixties. Each of these original modulators was designed to provide 250 kV, 262 A and 3.5 {mu}S at up to 360 pps using an inductance-capacitance resonant charging system, a modified type-E pulse-forming network (PFN), and a pulse transformer. The modulator internal control comprised of large step-start resistor-contactors, vacuum-tube amplifiers, and 120 Vac relays for logical signals. A major, power-component-only upgrade, which began in 1983 to accommodate the required beam energy of the SLAC Linear Collider (SLC) project, raised the modulator peak output capacity to 360 kV, 420 A and 5.0 {mu}S at a reduced pulse repetition rate of 120 pps. In an effort to improve safety, performance, reliability and maintainability of the modulator, this recent upgrade focuses on the remaining three-phase AC power input and modulator controls. The upgrade includes the utilization of primary SCR phase control rectifiers, integrated fault protection and voltage regulation circuitries, and programmable logic controllers (PLC) -- with an emphasis on component physical layouts for safety and maintainability concerns. In this paper, we will describe the design and implementation of each upgraded component in the modulator control system. We will also report the testing and present status of the modified modulators.
Date: November 4, 2011
Creator: Nguyen, M.N.; Burkhart, C.P.; Lam, B.K.; Morris, B. & /SLAC
Partner: UNT Libraries Government Documents Department

Compact, Intelligent, Digitally Controlled IGBT Gate Drivers for a PEBB-Based ILC Marx Modulator

Description: SLAC National Accelerator Laboratory has built and is currently operating a first generation prototype Marx klystron modulator to meet ILC specifications. Under development is a second generation prototype, aimed at improving overall performance, serviceability, and manufacturability as compared to its predecessor. It is designed around 32 cells, each operating at 3.75 kV and correcting for its own capacitor droop. Due to the uniqueness of this application, high voltage gate drivers needed to be developed for the main 6.5 kV and droop correction 1.7 kV IGBTs. The gate driver provides vital functions such as protection of the IGBT from over-voltage and over-current, detection of gate-emitter open and short circuit conditions, and monitoring of IGBT degradation (based on collector-emitter saturation voltage). Gate drive control, diagnostic processing capabilities, and communication are digitally implemented using an FPGA. This paper details the design of the gate driver circuitry, component selection, and construction layout. In addition, experimental results are included to illustrate the effectiveness of the protection circuit.
Date: June 7, 2010
Creator: Nguyen, M. N.; Burkhart, C.; Olsen, J. J. & Macken, K.
Partner: UNT Libraries Government Documents Department

Design Considerations for a PEBB-Based Marx-Topology ILC Klystron Modulator

Description: The concept of Power Electronic Building Blocks (PEBBs) has its origin in the U.S. Navy during the last decade of the past century. As compared to a more conventional or classical design approach, a PEBB-oriented design approach combines various potential advantages such as increased modularity, high availability and simplified serviceability. This relatively new design paradigm for power conversion has progressively matured since then and its underlying philosophy has been clearly and successfully demonstrated in a number of real-world applications. Therefore, this approach has been adopted here to design a Marx-topology modulator for an International Linear Collider (ILC) environment where easy serviceability and high availability are crucial. This paper describes various aspects relating to the design of a 32-cell Marx-topology ILC klystron modulator. The concept of nested droop correction is introduced and illustrated. Several design considerations including cosmic ray withstand, power cycling capability, fault tolerance, etc., are discussed. Details of the design of a Marx cell PEBB are included.
Date: December 9, 2009
Creator: Macken, K.; Beukers, T.; Burkhart, C.; Kemp, M.A.; Nguyen, M.N.; Tang, T. et al.
Partner: UNT Libraries Government Documents Department

Gate Drive For High Speed, High Power IGBTs

Description: A new gate drive for high-voltage, high-power IGBTs has been developed for the SLAC NLC (Next Linear Collider) Solid State Induction Modulator. This paper describes the design and implementation of a driver that allows an IGBT module rated at 800A/3300V to switch up to 3000A at 2200V in 3{micro}S with a rate of current rise of more than 10000A/{micro}S, while still being short circuit protected. Issues regarding fast turn on, high de-saturation voltage detection, and low short circuit peak current will be presented. A novel approach is also used to counter the effect of unequal current sharing between parallel chips inside most high-power IGBT modules. It effectively reduces the collector-emitter peak current, and thus protects the IGBT from being destroyed during soft short circuit conditions at high di/dt.
Date: June 18, 2007
Creator: Nguyen, M.N.; Cassel, R.L.; de Lamare, J.E.; Pappas, G.C. & /SLAC
Partner: UNT Libraries Government Documents Department

Final Design of the SLAC P2 Marx Klystron Modulator

Description: The SLAC P2 Marx has been under development for two years, and follows on the P1 Marx as an alternative to the baseline klystron modulator for the International Linear Collider. The P2 Marx utilizes a redundant architecture, air-insulation, a control system with abundant diagnostic access, and a novel nested droop correction scheme. This paper is an overview of the design of this modulator. There are several points of emphasis for the P2 Marx design. First, the modulator must be compatible with the ILC two-tunnel design. In this scheme, the modulator and klystron are located within a service tunnel with limited access and available footprint for a modulator. Access to the modulator is only practical from one side. Second, the modulator must have high availability. Robust components are not sufficient alone to achieve availability much higher than 99%. Therefore, redundant architectures are necessary. Third, the modulator must be relatively low cost. Because of the large number of stations in the ILC, the investment needed for the modulator components is significant. High-volume construction techniques which take advantage of an economy of scale must be utilized. Fourth, the modulator must be simple and efficient to maintain. If a modulator does become inoperable, the MTTR must be small. Fifth, even though the present application for the modulator is for the ILC, future accelerators can also take advantage of this development effort. The hardware, software, and concepts developed in this project should be designed such that further development time necessary for other applications is minimal.
Date: November 8, 2011
Creator: Kemp, M. A.; Benwell, A.; Burkhart, C.; Larsen, R.; MacNair, D.; Nguyen, M. et al.
Partner: UNT Libraries Government Documents Department

Development Status of the ILC Marx Modulator

Description: The ILC Marx Modulator is under development as a lower cost alternative to the 'Baseline Conceptual Design' (BCD) klystron modulator. Construction of a prototype Marx is complete and testing is underway at SLAC. The Marx employs solid state elements, IGBTs and diodes, to control the charge, discharge and isolation of the modules. The prototype is based on a stack of sixteen modules, each initially charged to {approx}11 kV, which are arranged in a Marx topology. Initially, eleven modules combine to produce the 120 kV output pulse. The remaining modules are switched in after appropriate delays to compensate for the voltage droop that results from the discharge of the energy storage capacitors. Additional elements will further regulate the output voltage to {+-} 0.5%. The Marx presents several advantages over the conventional klystron modulator designs. It is physically smaller; there is no pulse transformer (quite massive at these parameters) and the energy storage capacitor bank is quite small, owing to the active droop compensation. It is oil-free; voltage hold-off is achieved using air insulation. It is air cooled; the secondary air-water heat exchanger is physically isolated from the electronic components. This paper outlines the current developmental status of the prototype Marx. It presents a detailed electrical and mechanical description of the modulator and operational test results. It will discuss electrical efficiency measurements, fault testing, and output voltage regulation.
Date: June 16, 2008
Creator: Nguyen, M.; Beukers, T.; Burkhart, C.; Larsen, R.; Olsen, J.; Tang, T. et al.
Partner: UNT Libraries Government Documents Department

Development of Modulator Pulse Stability Measurement Device and Test Results at SLAC

Description: In this paper, the development of a pulse stability measurement device is presented. The measurement accuracy is better than 250uV, about 4.2ppm of a typical 60V input pulse. Pulse signals up to +/- 80V peak can be measured. The device works together with an oscilloscope. The primary function of the measurement device is to provide a precision offset, such that variations in the flattop of the modulator voltage pulse can be accurately resolved. The oscilloscope records the difference between the pulse flattop and the reference for a series of waveforms. The scope math functions are utilized to calculate the rms variations over the series. The frequency response of the device is characterized by the measured cutoff frequency of about 6.5MHz. In addition to detailing the design and calibration of the precision pulse stability device, measurements of SLAC line-type linac modulators and recently developed induction modulators will be presented. Factors affecting pulse stability will be discussed.
Date: August 19, 2011
Creator: Huang, C.; Burkhart, C.; Kemp, M.; Morris, B.; Beukers, T.; Ciprian, R. et al.
Partner: UNT Libraries Government Documents Department

Advanced Gate Drive for the SNS High Voltage Converter Modulator

Description: SLAC National Accelerator Laboratory is developing a next generation H-bridge switch plate [1], a critical component of the SNS High Voltage Converter Modulator [2]. As part of that effort, a new IGBT gate driver has been developed. The drivers are an integral part of the switch plate, which are essential to ensuring fault-tolerant, high-performance operation of the modulator. The redesigned driver improves upon the existing gate drive in several ways. The new gate driver has improved fault detection and suppression capabilities; suppression of shoot-through and over-voltage conditions, monitoring of dI/dt and Vce(sat) for fast over-current detection and suppression, and redundant power isolation are some of the added features. In addition, triggering insertion delay is reduced by a factor of four compared to the existing driver. This paper details the design and performance of the new IGBT gate driver. A simplified schematic and description of the construction are included. The operation of the fast over-current detection circuits, active IGBT over-voltage protection circuit, shoot-through prevention circuitry, and control power isolation breakdown detection circuit are discussed.
Date: May 7, 2009
Creator: Nguyen, M.N.; Burkhart, C.; Kemp, M.A.; /SLAC; Anderson, D.E. & Ridge, /Oak
Partner: UNT Libraries Government Documents Department

ILC Marx Modulator Development Program Status

Description: Development of a first generation prototype (P1) Marx-topology klystron modulator for the International Linear Collider is nearing completion at the Stanford Linear Accelerator Center. It is envisioned as a smaller, lower cost, and higher reliability alternative to the present, bouncer-topology, 'Baseline Conceptual Design'. The Marx presents several advantages over conventional klystron modulator designs. It is physically smaller; there is no pulse transformer (quite massive at ILC parameters) and the energy storage capacitor bank is quite small, owing to the active droop compensation. It is oil-free; voltage hold-off is achieved using air insulation. It is air cooled; the secondary air-water heat exchanger is physically isolated from the electronic components. The P1-Marx employs all solid state elements; IGBTs and diodes, to control the charge, discharge and isolation of the cells. A general overview of the modulator design and the program status are presented.
Date: March 4, 2009
Creator: Burkhart, C.; Beukers, T.; Larsen, R.; Macken, K.; Nguyen, M.; Olsen, J. et al.
Partner: UNT Libraries Government Documents Department

Redesign of the H-Bridge Switch Plate of the SNS High Voltage Converter Modulator

Description: The 1-MW High Voltage Converter Modulators [1] have operated in excess of 250,000 hours at the Spallation Neutron Source. Increased demands on the accelerator performance require increased modulator reliability. An effort is underway at SLAC National Accelerator Laboratory to redesign the modulator H-bridge switch plate with the goals of increasing reliability and performance [2]. The major difference between the SLAC design and the existing design is the use of press-pack IGBTs. Compared to other packaging options, these IGBTs have been shown to have increased performance in pulsed-power applications, have increased cooling capability, and do not fragment and disassemble during a fault event. An overview of the SLAC switch plate redesign is presented. Design steps including electrical modeling of the modulator and H-bridge, development of an integrated IGBT clamping mechanism, and fault tests are discussed. Experimental results will be presented comparing electrical performance of the SLAC switch plate to the existing switchplate under normal and fault conditions.
Date: May 7, 2009
Creator: Kemp, M.A.; Burkhart, C.; Nguyen, M.N.; /SLAC; Anderson, D.E. & Ridge, /Oak
Partner: UNT Libraries Government Documents Department

P1-Marx Modulator for the ILC

Description: A first generation prototype, P1, Marx-topology klystron modulator has been developed at the SLAC National Accelerator Laboratory for the International Linear Collider (ILC) project. It is envisioned as a lower cost, smaller footprint, and higher reliability alternative to the present, bouncer-topology, baseline design. The application requires 120 kV (+/-0.5%), 140 A, 1.6 ms pulses at a rate of 5 Hz. The Marx constructs the high voltage pulse by combining, in series, a number of lower voltage cells. The Marx employs solid state elements; IGBTs and diodes, to control the charge, discharge and isolation of the cells. Active compensation of the output is used to achieve the voltage regulation while minimizing the stored energy. The P1-Marx has been integrated into a test stand with a 10 MW L-band klystron, where each is undergoing life testing. A review of the P1-Marx design and its operational history in the L-band test stand are presented.
Date: August 26, 2010
Creator: Beukers, T.; Burkhart, C.; Kemp, M.; Larsen, R.; Nguyen, M.; Olsen, J. et al.
Partner: UNT Libraries Government Documents Department

Status of the SLC damping ring kicker systems

Description: The damping ring kickers for the SLAC Linear Collider must meet extreme requirements on rise and fall time, flatness, time and amplitude jitter and drift, voltage, repetition rate, and reliability. After several generations of improvements to the pulsers, magnets, and controls, and evolution in the understanding of the requirements, the kicker systems are no longer a serious constraint on SLC performance. Implications for future linear colliders are discussed. 14 refs.
Date: May 1, 1991
Creator: Mattison, T.; Cassel, R.; Donaldson, A.; Gough, D.; Gross, G.; Harvey, A. et al.
Partner: UNT Libraries Government Documents Department

Development Status of The ILC Marx Modulator

Description: The ILC Marx Modulator is under development as a lower cost alternative to the 'Baseline Conceptual Design' (BCD) klystron modulator. Construction of a prototype Marx is complete and testing is underway at SLAC. The Marx employs solid state elements, IGBTs and diodes, to control the charge, discharge and isolation of the modules. The prototype is based on a stack of sixteen modules, each initially charged to {approx}11 kV, which are arranged in a Marx topology. Initially, eleven modules combine to produce the 120 kV output pulse. The remaining modules are switched in after appropriate delays to compensate for the voltage droop that results from the discharge of the energy storage capacitors. Additional elements will further regulate the output voltage to {+-}0.5%. The Marx presents several advantages over the conventional klystron modulator designs. It is physically smaller; there is no pulse transformer (quite massive at these parameters) and the energy storage capacitor bank is quite small, owing to the active droop compensation. It is oil-free; voltage hold-off is achieved using air insulation. It is air cooled; the secondary air-water heat exchanger is physically isolated from the electronic components. This paper outlines the current developmental status of the prototype Marx. It presents a detailed electrical and mechanical description of the modulator and operational test results. It will discuss electrical efficiency measurements, fault testing, and output voltage regulation.
Date: June 7, 2010
Creator: Nguyen, M.; Beukers, T.; Burkhart, C.; Larsen, R.; Olsen, J. & Tang, T.
Partner: UNT Libraries Government Documents Department

The ILC P2 Marx and Application of the Marx Topology to Future Accelerators

Description: The SLAC P2 Marx is under development as the linac klystron modulator for the ILC. This modulator builds upon the success of the P1 Marx, which is currently undergoing lifetime evaluation. While the SLAC P2 Marx's (henceforth, 'P2 Marx') target application is the ILC, characteristics of the Marx topology make it equally well-suited for operation at different parameter ranges; for example, increased pulse repetition frequency, increased output current, longer pulse width, etc. Marx parameters such as the number of cells, cell capacitance, and component selection can be optimized for the application. This paper provides an overview of the P2 Marx development. In addition, the scalability of the Marx topology to other long-pulse parameter ranges is discussed.
Date: August 19, 2011
Creator: Kemp, M.A.; Benwell, A.; Burkhart, C.; Hugyik, J.; Larsen, R.; Macken, K. et al.
Partner: UNT Libraries Government Documents Department

Design, analysis and measurement of very fast kicker magnets at SLAC

Description: Recent experience with SLC has shown that very fast, ferrite-loaded, transmission-line, beam-kicker magnets can cause significant and undesirable distortion of a 1.5-2.5 kA, 20-4- kV pulse as it travels through the magnet. In general, there is a net lengthening of the pulse, with increases in its rise and fall times, a decrease in amplitude, and an unsymmetrical rounding of the flattop. In this partially tutorial treatise, a number of practical design considerations are discussed in terms of equivalent circuits, magnet circuit dispersion and dissipation, undesired circuit shunting and coupling, high-voltage breakdown problems and high-order-mode losses that lead to beam tube heating. These effects are linked to the properties of the materials, the presence of radiation and realizable magnet topologies. Measurements and calculations of some of these characteristics for several magnet designs are reviewed. The results presented come from a truly eclectic effort. 8 refs., 1 fig.
Date: March 1, 1989
Creator: Weaver, J.N.; Bowden, G.B.; Bulos, F.; Cassel, R.L.; Donaldson, A.R.; Harvey, A. et al.
Partner: UNT Libraries Government Documents Department

Design of the Second-Generation ILC Marx Modulator

Description: SLAC National Accelerator Laboratory (SLAC) has initiated a program to design and build a Marx-topology modulator to produce a relatively compact, low-cost, high availability klystron modulator for the International Linear Collider (ILC). Building upon the success of the P1 Marx, the SLAC P2 Marx is a second-generation modulator whose design further emphasizes the qualities of modularity and high-availability. This paper outlines highlights of this design and presents single-cell performance data obtained during the proof-of-concept phase of the project.
Date: September 14, 2010
Creator: Kemp, M. A.; Benwell, A.; Burkhart, C.; Larsen, R.; MacNair, D.; Nguyen, M. et al.
Partner: UNT Libraries Government Documents Department

Solid-State Modulators for RF And Fast Kickers

Description: As the switching capabilities of solid-state devices increase, these devices are being incorporated into modulator designs for high voltage accelerator applications. Solid-state modulators based on inductive adder circuit topology have demonstrated great versatility with regard to pulse width and pulse repetition rate while maintaining fast pulse rise and fall times. Additionally, these modulators are capable of being scaled to higher output voltage and power levels. An explanation of the basic circuit operation will be presented as well as test data of several different hardware systems.
Date: March 14, 2006
Creator: Cook, E. G.; Akana, G. L.; Gower, E. J.; Hawkins, S. A.; Hickman, B. C.; Brooksby, C. A. et al.
Partner: UNT Libraries Government Documents Department