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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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51 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Copper bromide vapour laser with an output pulse duration of up to 320 ns

We report the development of a copper bromide vapour laser with an output pulse duration of up to 320 ns. To lengthen the pulse, the discharge current was limited using a compound switch comprising a pulsed hydrogen thyratron and a tacitron. This technique permits limiting the excitation of the working levels at the initial stage of the discharge development to lengthen the inversion lifetime. The longest duration of a laser pulse was reached in tubes 25 and 50 mm in diameter for a pulse repetition rate of 2 – 4 kHz. (lasers and laser beams)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Frequency and energy characteristics of a Cu – Ne laser at different durations of the leading edge of the excitation pulse

The lasing characteristics of a copper vapour laser in a tube with forced heating, having a length of 50 cm and a diameter of 2 cm, excited by a train of pulses are investigated. Comparative studies of the frequency and energy characteristics of the laser are performed with a leading edge duration of the excitation pulse of ∼25 ns (when the capacitance discharges through a thyratron and a magnetic compression line) and ∼3 and 1 ns (using circuits with a high-speed switch – kivotron). It is shown that a decrease in the leading edge duration gives rise to an increase in the optimal pulse repetition rate up to ∼30 kHz, the generation efficiency up to 3.2 % and the generation power per unit length over 100 W m{sup −1}. The results obtained confirm the concept of limiting the frequency and energy characteristics of a copper vapour laser due to the insufficient rate of energy input into the plasma at high prepulse electron concentrations. (paper)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Experimental characterization of a coaxial plasma accelerator for a colliding plasma experiment

We report experimental results of a single coaxial plasma accelerator in preparation for a colliding plasma experiment. The utilized device consisted of a coaxial pair of electrodes, accelerating the plasma due to J×B forces. A pulse forming network, composed of three capacitors connected in parallel, with a total capacitance of 27 μF was set up. A thyratron allowed to switch the maximum applied voltage of 9 kV. Under these conditions, the pulsed currents reached peak values of about 103 kA. The measurements were performed in a small vacuum chamber with a neutral-gas prefill at gas pressures between 10 Pa and 14 000 Pa. A gas mixture of ArH{sub 2} with 2.8% H{sub 2} served as the discharge medium. H{sub 2} was chosen in order to observe the broadening of the H{sub β} emission line and thus estimate the electron density. The electron density for a single plasma accelerator reached peak values on the order of 10{sup 16} cm{sup −3}. Electrical parameters, inter alia inductance and resistance, were determined for the LCR circuit during the plasma acceleration as well as in a short circuit case. Depending on the applied voltage, the inductance and resistance reached values ranging from 194 nH to 216 nH and 13 mΩ to 23 mΩ, respectively. Furthermore, the plasma velocity was measured using a fast CCD camera. Plasma velocities of 2 km/s up to 17 km/s were observed, the magnitude being highly correlated with gas pressure and applied voltage.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Influence of the voltage pulse front shortening on the pulse repetition rate in a copper vapour laser

The lasing characteristics of a copper vapour laser are investigated in the regime of a pulse train excited in the internalheating tube with the diameter of 2 cm and length of 48 cm. Two power supply schemes are compared: a conventional scheme with a storage capacitor discharged through a thyratron connected to a peaking capacitor and the scheme in which the peaking capacitor is connected to the laser active element through a kivotron – a fast switch based on the 'open discharge' with a turn-on time of less than 1 ns. It is shown that in the considered range of the pulse repetition rates f = 2 – 16 kHz in the first case we deal with a typical energy dependence on frequency having a maximum near 4 – 5 kHz. In the second case, the lasing energy is frequency-independent; hence, the average power in this range is proportional to f. The results obtained are explained by the neutralised influence of the initial electron concentration on energy characteristics of the copper vapour laser. (control of laser radiation parameters)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

The Recent Improvements of the SNS Extraction Kicker Power Supplies

A total of 14 extraction kickers., with one as the hot spare., are in service to extract protons out of the storage ring at the SNS. The jitter issue and the short lifetime of the switches were resolved after the thyratrons were replaced with solid state switches in 2018. This paper discusses the recent improvements. Two thyristor switches suffered overheating damage in separate incidents. One was due to the oil pump failure and the other was the result of a disconnected oil hose. An ultrasonic flow meter and a fiber optic temperature monitoring system have been installed for each extraction kicker power supply. The flow meter continuously monitors the entire tank oil flow. The temperature monitor detects the thyristor switch real-time temperatures in three locations. Fault thresholds are selected so that the thyristor switches are protected from overheating damage. Alarms are configured to alert staff to take actions before faults occur. In addition., the cause of an intermittent misfire issue was identified, and the solution was implemented. Lastly., a future oscilloscope upgrade and an oil level sensor are discussed.

Tan, Yugang↗
DOE OSTI2025

A High-Voltage High-Current Benchtop Test Stand for Solid-State Switch Testing at the SNS

Solid-state switches already replaced thyratrons in the SNS extraction kicker power supplies, offering improved efficiency and reliability. However, recent supply chain disruptions, combined with a self-firing issue, led us to explore alternative solutions. A vendor-developed MOS-Gated Thyristor switch was introduced but ultimately failed during testing. To investigate the failure and assess possible improvements, a benchtop test stand was constructed to evaluate the performance of a single stage board. This test stand features a Pulse Forming Network (PFN) that operates at 6 kV and 6 kA, with a repetition rate exceeding 60 Hz, simulating real operational conditions. By utilizing this setup, we seek to gain a better understanding of the failure mechanisms, refine the switch designs, and ultimately develop a more reliable alternative for the extraction kicker power supplies.

Bullman, Austin [ORNL]↗
DOE OSTI2023

Dual Triggered Beam Extraction Kicker (Rev. 1)

A Blumlein modulator is a relatively inexpensive pulsed power device that can deliver highly repeatable pulses that can be used to change the path of beam pulses. The modulator is primarily built with transmission line cable which is relatively inexpensive. Due to the highly repeatable nature of a Blumlein modulator it is a great tool for kicking beam pulses while producing very little spill or losses in beam current. One of the challenges with a Blumlein kicker is that the length of the kicking pulse output by the modulator is determined by the length of the cables. Cable lengths are set prior to implementation for the desired kicking pulse width. The Blumlein modulator at LANSCE uses a single thyratron which can deliver two 50-kilovolt 1,000-amp pulses of opposite polarity to kicking plates at the same time. This method makes for a very strong kick that is highly repeatable. A method that has been discussed, to deliver a different pulse width, is to add a second trigger that would be fired, once the desired pulse width has been delivered, cutting out the remaining pulse. The second trigger would offer a lot of variability with the pulse width of the kicker. This method has only ever been attempted using low current and relatively low voltages compared to the scale needed to properly kick a beam pulse. This in turn allows for the use of power supplies with a higher repetition rate. The advancement of this standard kicker technology in the accelerator facilities would attract attention within the scientific and engineering communities. The project detailed within will investigate the capabilities of different triggering topologies and design a prototype dual triggered Blumlein kicker modulator capable of variable kicking pulse width.

43 PARTICLE ACCELERATORS↗
NASA NTRS1974

Development and planning and design of equipment pumping generator of semiconductor lasers

The schematic of a multidimensional current pulse generator is studied. A MTKh-90 cold cathode thyratron is used as the current commutator. In the autooscillation mode on a frequency of 380 hertz the generator creates a current to 100 amps per pulse in a control resistance of 1 ohm. The pulse duration is regulated within the limits from 0.1 to 3.0 microseconds.

Popkov, A. V.↗
NASA NTRS1975

Double-discharge copper-vapor laser

Power supply for discharge pulses consists of two capacitors that are made to discharge synchronously with adjustable time intervals. First pulse is switched with hydrogen thyratron, and second by spark gap. Lasing action peaks for appropriate combination of these two parameters.

Chen, C. J.↗
NASA NTRS1976

Electric-discharge-pumped nitrogen ion laser

The routine operation is described of an N2(+) laser oscillating on the first negative band system of N2(+) which is produced in a preionized transverse discharge device. The discharge design incorporates features which favor the efficient production of the excitation transfer reaction of He2(+) with N2. A capacitive discharge switched by means of a high-current grounded grid thyratron is used to meet the design requirement of a volumetric discharge in high-pressure gas mixtures where the electric discharge need not have an ultrafast rise time (greater than 10 nsec) but should be capable of transferring large quantities of stored electric energy to the gas. A peak power of 180 kW in an 8-nsec laser pulse was obtained with a 0.1% mixture of N2 in helium at a total pressure of 3 atm. The most intense laser oscillations were observed on the (0,1) vibrational transition at 427.8 microns.

Laudenslager, J. B.↗
NASA NTRS1987

Engine flow visualization using a copper vapor laser

A flow visualization system has been developed to determine the air flow within the combustion chamber of a motored, axisymmetric engine. The engine has been equipped with a transparent quartz cylinder, allowing complete optical access to the chamber. A 40-Watt copper vapor laser is used as the light source. Its beam is focused down to a sheet approximately 1 mm thick. The light plane is passed through the combustion chamber, and illuminates oil particles which were entrained in the intake air. The light scattered off of the particles is recorded by a high speed rotating prism movie camera. A movie is then made showing the air flow within the combustion chamber for an entire four-stroke engine cycle. The system is synchronized so that a pulse generated by the camera triggers the laser's thyratron. The camera is run at 5,000 frames per second; the trigger drives one laser pulse per frame. This paper describes the optics used in the flow visualization system, the synchronization circuit, and presents results obtained from the movie. This is believed to be the first published study showing a planar observation of airflow in a four-stroke piston-cylinder assembly. These flow visualization results have been used to interpret flow velocity measurements previously obtained with a laser Doppler velocimetry system.

Regan, Carolyn A.↗
NASA NTRS1989

Stratified charge rotary engine - Internal flow studies at the MSU engine research laboratory

High-speed visualization and laser Doppler velocimetry (LDV) systems consisting of a 40-watt copper vapor laser, mirrors, cylindrical lenses, a high speed camera, a synchronization timing system, and a particle generator were developed for the study of the fuel spray-air mixing flow characteristics within the combustion chamber of a motored rotary engine. The laser beam is focused down to a sheet approximately 1 mm thick, passing through the combustion chamber and illuminates smoke particles entrained in the intake air. The light scattered off the particles is recorded by a high speed rotating prism camera. Movies are made showing the air flow within the combustion chamber. The results of a movie showing the development of a high-speed (100 Hz) high-pressure (68.94 MPa, 10,000 psi) fuel jet are also discussed. The visualization system is synchronized so that a pulse generated by the camera triggers the laser's thyratron.

Hamady, F.↗
DOE OSTI2014

Development of a pulse modulator to drive 6.19 MW klystron for 15 MeV electron linac

We present the design, construction, and characterization of a line-type pulse high-voltage modulator system capable of generating 140-kV, 6 μs pulses width at 150 pulses per second into a Klystron as load. The modulator is used to energize a variety of highpower microwave devices requiring voltage stability and reproducibility. Voltage ripple is less than 0.4% during the flat top, with a shot-to-shot voltage variation of less than 0.2 %. The primary circuit consists of six-stage tuneable pulse-forming networks (PFN's). The PFN is charged by a highly stable charging power supply. The total energy stored is released through a CX-1559 E2V make thyratron into a 1: 11 pulse transformer, which generates 140 kV, 6 μs pulses. The flat-top voltage generated by the modulator is highly desirable for driving RF sources requiring high quality electron beams. Linac is one of the important fields of study in modern technology due its wide applications for medical and industrial purposes in addition to physics research. (author)

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Spark gaps synchronization using electrical trigger pulses

In pulse power systems, it is required to have synchronized triggering of two or more high voltage spark gaps capable of switching large currents, using electrical trigger pulses. This paper intends to study the synchronization of spark gaps using electrical trigger. The trigger generator consists of dc supply, IGBT switch and driver circuit which generates 8kV, 400ns (FWHM) pulses. The experiment was carried out using two 0.15uF/50kV energy storage capacitors charged to 12kV and discharged through stainless steel spark gaps of diameter 9 mm across 10 ohm non inductive load. The initial experiment shows that synchronization has been achieved with jitter of 50 to 100ns. Further studies carried out to reduce the jitter time by varying various electrical parameters will be presented. (author)

43 PARTICLE ACCELERATORS↗