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STABILIZED RELAXATION OSCILLATOR

Description: An unsynchronized thyratron relaxation oscillator circuit was developed, whose rate is stabilized through the use of a Schmitt discriminator to determine the thyratron firing point. Drift and jitter in the period are less than 0.1% after warmup. (auth)
Date: August 1, 1962
Creator: Cohn, C.E.
Partner: UNT Libraries Government Documents Department

High Voltage Pulsar For 184-inch Cyclotron Electric Deflector

Description: This paper describes a high voltage pulse generator developed to deflect the beam of the 184-inch cyclotron at Berkeley, California. The apparatus develops a deflecting potential of 200 kilovolts that rises from 10% to 90% of peak value in 0.1 microseconds. The unit employs two similar 100 kilovolt water cooled pulse transformers connected symmetrically about ground to the electric deflector bars. Water-cooled General Electric pulse capacitors are discharged through the two turn primary windings of the pulse transformers by triggering a battery of 16 paralleled Kuthe 5022 hydrogen thyratrons. Output voltages are developed across the 17 turn secondary winding of the pulse transformer. The transformer is mounted in an oil filled lucite case that provides both insulation and compact design.
Date: April 24, 1948
Creator: Kerns, Q.A.; Baker, W.R.; Edwards, R.F. & Farly, G.M.
Partner: UNT Libraries Government Documents Department

TUBE DESIGN AND CIRCUIT CONSIDERATIONS FOR FAST-HEATING ELECTRONIC SYSTEMS

Description: Fast-heating electronic systems are becoming increasingly important in military applications. Operational requirements in the range of 10 to 12 seconds must be accomplished with a combination of tube and circuit design. Definitions of tube and system operational time are numerous and interrelated so that selection of an appropriate test depends on the circuit application, ease of measurement, and test equipment capabilities. Circuit designs which minimize differences among tubes will also minimize drift during warm-up so that a stable operating point is reached more quickly. Properties of the vacuum tube classed as detrimental, such as interelectrode leakages, are more critical in fast operational tubes. Gains in operational time are achieved by: (1) reduction of the heated mass, (2) high cathode activation, and (3) reduction of conduction losses. General design considerations of the heater, cathode, and tube assembly are discussed. Six tube types encompassing subminiatures, miniature, hydrogen thyratron, and power triodes were developed and produced which function at 10 seconds in a fast operational system, tube characteristics are given. (auth)
Date: June 1, 1958
Creator: Hardin, K D
Partner: UNT Libraries Government Documents Department

Final report: Efficient thyratron modulator project

Description: The purpose of this program was to examine methods of increasing the efficiency of producing pulses to drive Klystrons in the 150 MW range. This may include 2 Klystrons in the 75 MW range. Specific methods of interest to improve the pulse efficiency were the use of a circuit to add energy to the tail of the pulse, the use of a bipyrimidal transformer, and the use of gas insulation as a means of improving the pulse shape. These methods were investigated using both thyratron and IGBT switching. The low cost designs developed in this work consisted of low voltage designs which don't require the oil immersion. These designs can be ''hot tuned'' based on the use of simple, tunable inductors.
Date: November 26, 1999
Creator: Adler, R. J.; Richter-Sand, R. J. & Gregg, C. W.
Partner: UNT Libraries Government Documents Department

BEAM COUPLING PHENOMENA IN FAST KICKER SYSTEMS.

Description: Beam coupling phenomena have been observed in most fast kicker systems through out Brookhaven Collider-Accelerator complex. With ever-higher beam intensity, the signature of the beam becomes increasingly recognizable. The beam coupling at high intensity produced additional heat dissipation in high voltage modulator, thyratron grids, thyratron driver circuit sufficient to damage some components, and causes trigger instability. In this paper, we will present our observations, basic coupling mode analysis, relevance to the magnet structures, issues related to the existing high voltage modulators, and considerations of the future design of the fast kicker systems.
Date: June 18, 2001
Creator: ZHANG,W.; AHRENS,L.A.; GLENN,J.; SANDBERG,J. & TSOUPAS,N.
Partner: UNT Libraries Government Documents Department

Design Optimization and Construction of the Thyratron/PFN Based Cost Model Modulator for the NLC

Description: As design studies and various R and D efforts continue on Next Linear Collider (NLC) systems, much R and D work is being done on X-Band klystron development, and development of pulse modulators to drive these X-Band klystrons. A workshop on this subject was held at SLAC in June of 1998, and a follow-up workshop is scheduled at SLAC June 23-25, 1999. At the 1998 workshop, several avenues of R and D were proposed using solid state switching, induction LINAC principles, high voltage hard tubes, and a few more esoteric ideas. An optimized version of the conventional thyratron-PFN-pulse transformer modulator for which there is extensive operating experience is also a strong candidate for use in the NLC. Such a modulator is currently under construction for base line demonstration purposes. The performance of this ''Cost Model'' modulator will be compared to other developing technologies. Important parameters including initial capital cost, operating maintenance cost, reliability, maintainability, power efficiency, in addition to the usual operating parameters of pulse flatness, timing and pulse height jitter, etc. will be considered in the choice of a modulator design for the NLC. This paper updates the progress on this ''Cost Model'' modulator design and construction.
Date: March 15, 1999
Creator: Koontz, Roland F
Partner: UNT Libraries Government Documents Department

A gate drive circuit for gate-turn-off (GTO) devices in series stack.

Description: A gate-turn-off (GTO) switch is under development at the Advanced Photon Source as a replacement for a thyratron switch in high power pulsed application. The high voltage in the application requires multiple GTOs connected in series. One component that is critical to the success of GTO operation is the gate drive circuit. The gate drive circuit has to provide fast high-current pulses to the GTO gate for fast turn-on and turn-off. It also has to be able to operate while floating at high voltage. This paper describes a gate drive circuit that meets these requirements.
Date: April 13, 1999
Creator: Despe, O.
Partner: UNT Libraries Government Documents Department

GAS DISCHARGE SWITCH EVALUATION FOR RHIC BEAM ABORT KICKER APPLICATION.

Description: A gas discharge switch EEV HX3002 is being evaluated at Brookhaven National Laboratory as a possible candidate of RHIC Beam Abort Kicker modulator main switch. At higher beam energy and higher beam intensity, the switch stability becomes very crucial. The hollow anode thyratron used in the existing system is not rated for long reverse current conduction. The reverse voltage arcing caused thyratron hold-off voltage de-rating has been the main limitation of the system operation. To improve the system reliability, a new type of gas discharge switch has been suggested by Marconi Applied Technology for its reverse conducting capability.
Date: June 30, 2002
Creator: ZHANG,W.; SANDBERG,J.; SHELDRAKE,R. & PIRRIE,C.
Partner: UNT Libraries Government Documents Department

The Advanced Photon Source linac modulators PSpice simulation and upgrade.

Description: The APS linac modulators provide DC pulses to Thales 35/45-MW klystrons. The modulators are pulse forming network (PFN)-type pulsers with EMI 40-kV switch-mode charging supplies. The PFN consists of two 8-cell lines connected in parallel. EEV CX1836A thyratrons are used as discharge switches. The PSpice simulation of the modulators using OrCAD release 9.1 made it possible to find appropriate parameters of RC circuits that reduce high-frequency ringing of the pulse transformer primary voltage. In order to improve pulse top flatness (originally {+-}3%), new coils were built and installed. The coils allow discrete tuning of pulse waveforms by changing the amount of used turns. The advantage of two parallel-line PFN configurations was also used. An equivalent method using a low-voltage generator was used for PFN fine tuning.
Date: June 28, 2002
Creator: Cours, A. & Smith, T.
Partner: UNT Libraries Government Documents Department

Analysis of beam loss induced abort kicker instability

Description: Through more than a decade of operation, we have noticed the phenomena of beam loss induced kicker instability in the RHIC beam abort systems. In this study, we analyze the short term beam loss before abort kicker pre-fire events and operation conditions before capacitor failures. Beam loss has caused capacitor failures and elevated radiation level concentrated at failed end of capacitor has been observed. We are interested in beam loss induced radiation and heat dissipation in large oil filled capacitors and beam triggered thyratron conduction. We hope the analysis result would lead to better protection of the abort systems and improved stability of the RHIC operation.
Date: May 20, 2012
Creator: W., Zhang; Sandberg, J.; Ahrens, L.; Fischer, W.; Hahn, H.; Mi, J. et al.
Partner: UNT Libraries Government Documents Department

FAST BEAM CHOPPERS FOR THE ELECTRON-RING ACCELERATOR

Description: Two beam choppers were constructed which produce an approximately square, 20-ns pulse of 3+-MeV electrons out of the best portion of the 300-ns Astron beam or an 8-{micro}s microwave electron linac beam for injection into the electron-ring accelerator (ERA) compressor. The choppers are impedance-matched traveling-wave devices which deflect the beam with equal strength electric and magnetic forces, and are powered with either three-electrode spark gaps or thyratrons and a 20-ns pulse line. The electron beam is biased out of the beam-transport system with a dc magnetic field, and switched into it with the chopper.
Date: February 7, 1969
Creator: Faltens, Andris & Kerns, Cordon.
Partner: UNT Libraries Government Documents Department

Dual Power Supplies for PEP-II Injection Kickers

Description: Originally the PEP-II injection kickers were powered by one power supply. Since the kicker magnets where not perfectly matched, the stored beam got excited by about 7% of the maximum kicker amplitude. This led to luminosity losses which were especially obvious for trickle injection when the detector is on for data taking. Therefore two independent power supplies with thyratrons in the tunnel next to the kicker magnet were installed. This also reduces the necessary power by about a factor of four since there are no long cables that have to be charged. The kickers are now independently adjustable to eliminate any non-closure of the kicker system and therefore excitation of the stored beam. Setup, commissioning and fine tuning of this system are discussed.
Date: May 25, 2005
Creator: Olszewski, J; Decker, F.-J.; Iverson, R.H.; Kulikov, A.; Pappas, C. & /SLAC
Partner: UNT Libraries Government Documents Department

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

AN ALTERNATIVE APPROACH TO LOW FREQUENCY RF ACCELERATORS AND POWER SOURCES.

Description: The Muon Collider and Neutrino Factory projects require low frequency rf cavities because the size and emittance of the muon beam is much larger than is usual for electron or proton beams. The range of 30 MHz to 200 MHz is of special interest. However, the size of an accelerator with low frequency will be impractically large if it is simply scaled up from usual designs. In addition, to get very high peak power in this range is difficult. Presented in this paper is an alternative structure that employs a quasi-lumped inductance that can significantly reduce the transverse size while keeping high gradient. Also addressed is a power compression scheme with a thyratron. This gives a possible solution to provide very high peak power.
Date: June 18, 2001
Creator: ZHAO, Y.
Partner: UNT Libraries Government Documents Department

A NEW CONCEPTUAL DESIGN OF THE SNS FULL TURN FAST EXTRACTION KICKER POWER SUPPLY SYSTEM.

Description: The new conceptual design of full turn fast extraction kicker power supply system of the Spallation Neutron Source main ring will be presented in this paper. In this design, the extraction kicker power modulators will be located outside of the tunnel, as requested by the SNS Project. Its purpose is to minimize the components inside of the synchrotron tunnel. The high voltage modulator will use Blumlein pulser and hollow-anode thyratron structure, a parallel termination resistor and two transmission cables. Main advantages include: flexible system configuration for unipolar single drive or push-pull double drive of the kicker magnets, lower charging voltage, lower beam impedance, lower number of high voltage cables, and large design margin for implementation and future upgrade.
Date: June 18, 2001
Creator: ZHANG,W.; SANDBERG,J.; TSOUPAS,N.; MI,J.; LAMBIASE,R.; PAI,C. et al.
Partner: UNT Libraries Government Documents Department

High voltage, fast turn-on and turn-off switch: Final report for period September 2, 1998 - March 17, 1999

Description: The aspect to be investigated during this contract was an electron-beam triggered diamond switch to be used in high power modulators. Today's high power modulators require higher voltage switches than those developed to date. Specifically, the proposed 1 TeV linear collider, the NLC/ILC at the Stanford Linear Accelerator Center (SLAC), consists of two linacs with 6600 X-Band klystrons powered by 3300 high power modulators. These modulators require switches capable of handling 80 kV, switching 8 kA with pulse durations ranging from 2 ps (linac) to 6 {micro}s (pre-linac) with switching times <50 ns at pulse repetition frequencies up to 180 Hz. In addition the large number of switches and other components dictate a pulse to pulse jitter of <10 ns and a mean time between failures of at least 50,000 hours. The present approach is to use hydrogen filled thyratrons. While these switches meet the voltage and conduction current requirements they lack the required reliability (pulse to pulse jitter) and lifetime. Research to improve these aspects is in progress. A solid state switch inherently offers the required reliability and lifetime. However, Si-based switches developed to date are limited to about 5 kV and several must be stacked in series to deliver the required voltage. This further increases the already large parts count and compromises reliability and lifetime. A monolithic, solid state switch capable of meeting all the requirements for X-Band modulators would be ideal. DOE selected this proposal for a Phase 1 SBIR award and this final report describes the progress made during the contract.
Date: April 10, 1999
Creator: Schein, Jochen; Xu, Xiaoxi; Qi, Niansheng; Gensler, Steven; Prasad, Rahul & Krishnan, Mahadevan
Partner: UNT Libraries Government Documents Department

Identifying Longitudinal Jitter Sources in the LCLS Linac

Description: The Linac Coherent Light Source (LCLS) at SLAC is an x-ray Free Electron Laser (FEL) with wavelengths of 0.15 nm to 1.5 nm. The electron beam stability is important for good lasing. While the transverse jitter of the beam is about 10-20% of the rms beam sizes, the jitter in the longitudinal phase space is a multiple of the energy spread and bunch length. At the lower energy of 4.3 GeV (corresponding to the longest wavelength of 1.5 nm) the relative energy jitter can be 0.125%, while the rms energy spread is with 0.025% five times smaller. An even bigger ratio exists for the arrival time jitter of 50 fs and the bunch duration of about 5 fs (rms) in the low charge (20 pC) operating mode. Although the impact to the experiments is reduced by providing pulse-by-pulse data of the measured energy and arrival time, it would be nice to understand and mitigate the root causes of this jitter. The thyratron of the high power supply of the RF klystrons is one of the main contributors. Another suspect is the multi-pacting in the RF loads. Phase measurements down to 0.01 degree (equals 10 fs) along the RF pulse were achieved, giving hints to the impact of the different sources.
Date: July 6, 2012
Creator: Decker, Franz-Josef; /SLAC; Akre, Ron; /SLAC; Brachmann, Axel; /SLAC et al.
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 Pulsed Modulator Power Supply for the g-2 Muon Storage Ring Injection Kicker

Description: This paper describes the pulse modulator power supplies used to drive the kicker magnets that inject the muon beam into the g-2 storage ring that has been built at Brookhaven. Three modulators built into coaxial structures consisting of a series circuit of an energy storage capacitor, damping resistor and a fast thyratron switch are used to energize three magnets that kick the beam into the proper orbit. A 100 kV charging power supply is used to charge the capacitor to 95 kV. the damping resistor shapes the magnet current waveform to a 450 nanosecond half-sine to match the injection requirements. this paper discusses the modulator design, construction and operation.
Date: March 29, 1999
Creator: Mi,J.; Lee, Y.Y.; Morse, W. M.; Pai, C.; Pappas, G.; Sanders, R. et al.
Partner: UNT Libraries Government Documents Department

A NEW CROWBAR SYSTEM FOR THE PROTECTION OF HIGH POWER GRIDDED TUBES AND MICROWAVE DEVICES

Description: As part of the electron cyclotron heating (ECH) facility upgrade at the DIII-D National Fusion Facility, two 8.4 MW modulator/regulator power systems were designed and constructed (Ref. 1). Each power system uses a high power tetrode to modulate and regulate the cathode voltage for two 1 MW-class 110 GHz gyrotrons (Ref. 2). A critical element in the power system is the fault energy divertor, or crowbar switch, that protects the tetrode and the gyrotrons in the event of an arc fault. Traditionally, mercury filled ignitron switches are used for this application, but it was desired to eliminate hazardous materials and improve overall switching performance. The new crowbar switch system was required to meet the following requirements: Operating voltage: -105 kVdc; Peak current (750 ms e-fold): 1.6 kA; Follow-on current: <1 kA (25 ms); Charge transfer per shot: <15 Cb; and Turn-on time: <1 {micro}s. The switch that was chosen for the new design is a low pressure deuterium filled device, called a metal-arc thyratron, manufactured by Marconi Applied Technologies (Ref. 3). In addition to the new crowbar switch assembly, improved fault signal processing circuitry was developed. This new circuitry uses fiber-optics for signal and trigger transmission and a complex programmable logic device for high speed signal and logic processing. Two generations of metal-arc thyratrons have been commissioned in the two ECH power systems constructed at DIII-D. In the first, the crowbar system performed extremely well, meeting all of the operating requirements and demonstrating its ability to protect a 36 gauge copper wire from fusing (energy let-through <10 J). However, after accumulating over 500 shots, the metal-arc thyratrons lost their ability to reliably hold-off voltage. This problem was solved by Marconi with a design modification of the thyratron electrodes. The second generation tubes were installed in the second ECH power system. ...
Date: April 2001
Creator: Pronko, S. G. E. & Harris, T. E.
Partner: UNT Libraries Government Documents Department