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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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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Utilization of the CW magnetrons as coherent RF sources for superconducting RF accelerators

CW magnetrons designed and optimized for industrial heaters, driven by an injection-locking signal, were suggested to power Superconducting RF (SRF) cavities. However, the CW magnetrons, which are regenerative generators, are intended to operate in self-excitation mode, so, for reliable starting they use a large regenerative gain, causing a large regenerative instability in operation. Thus, power supply ripple, even shot noise, etc., lead to multiple sidebands forming a quasi-continuous noise spectrum at the carrier frequency. Therefore, in the traditionally used mode of operation and control, such magnetrons are inapplicable for powering high Q-factor SRF cavities. A new approach to operation and control of CW magnetrons considering non-stationary processes during start-up and operation makes it possible to find a mode of almost coherent RF generation of tubes with a significant reduction in regenerative instability and noise and increased efficiency. In our work is presented substantiation for the newly developed mode with an analysis of the new approach based on experimental results. •In this article, for the first time, non-stationary, regenerative processes are considered during the start-up and operation of CW magnetrons for powering high-Q superconducting RF cavities.•An analytical study, confirmed by experiments, showed that the traditionally used modes of starting and operating CW magnetrons are not suitable for powering high-Q superconducting RF cavities.•In fact, to make CW magnetrons suitable for such cavities, the physics of starting and operating CW magnetrons must be changed. This has been demonstrated in our work.•In developing the Stimulated Coherent Generation Mode [NIM A 980 (2020) 164366], we have shown the suitability of this mode for starting and operating CW magnetrons for high-Q superconducting RF cavities.•Analytical analysis, verified experimentally, substantiates in our article the suitability of the “Mode of stimulated coherent generation” of CW magnetrons for powering high-Q superconducting cavities in pulsed and continuous modes.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

RF synchronized short pulse laser ion source

A laser ion source that produces shortly bunched ion beam is proposed. In this ion source, ions are extracted immediately after the generation of laser plasma by an ultra-short pulse laser before its diffusion. The ions can be injected into radio frequency (RF) accelerating bucket of a subsequent accelerator. As a proof-of-principle experiment of the ion source, a RF resonator is prepared and H{sub 2} gas was ionized by a short pulse laser in the RF electric field in the resonator. As a result, bunched ions with 1.2 mA peak current and 5 ns pulse length were observed at the exit of RF resonator by a probe.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

High efficiency RF sources developments

Calabazas Creek Research, Inc. (CCR) and its collaborators are developing high efficiency RF sources operating from a few hundred MHz to C-Band and power levels from tens to hundreds of kilowatts with the goal of providing MW-relevant sources. The efficiencies approach or exceed 80% with projected costs as low as $0.50/ Watt. Sources under development include magnetrons with phase and amplitude control, single and multi-beam klystrons, multi-beam power grid tubes, and multiple beam IOTs. A magnetron system achieved more than 80% efficiency with fast amplitude control using modulation of the phase locking signal. This would be a low cost, high efficiency RF source for superconducting accelerators. An L-Band, single beam klystron was built with simulated efficiency of 80%. The klystron has yet to be tested to confirm the simulation results. CCR is currently developing a multi-beam klystron to produce more than 200 kW CW at 80% efficiency. Also in development is a multiple beam triode to produce 200 kW CW from 300 MHz to approximately 1 GHz. Not only does the simulated efficiency exceed 75%, but it would be the lowest cost RF source in this frequency range. Finally, CCR recently concluded research for a multiple beam IOT at 700 MHz using third harmonic drive to boost efficiency toward 85%. Successful development and transition to production of these sources will significantly alter the cost/performance landscape for RF power generation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

The new RF sources for accelerators

Several new RF sources are being developed for accelerator and collider applications. Assembly is nearing completion of a multiple beam inductive output tube at 352 MHz. An annular beam klystron is being developed to produce 10 MW pulses at 1.3 GHz. The annular beam approach provides significant cost reduction over similar multiple beam devices. Fabrication is underway on a 10 kW, periodic permanent magnet klystron at 2.815 GHz. Permanent magnets eliminate the solenoid and associated power supplies and cooling requirements to reduce operational cost. Investigations are beginning on a novel approach for driving accelerator cavities using pulse shaping to increase coupling efficiency and dramatically reduce RF power requirements.

43 PARTICLE ACCELERATORS↗
NASA NTRS1973

RF-source resistance meters

Several embodiments of RF source resistance measuring devices are disclosed. Common to all embodiments in the feature of the inclusion of at least one variable resistor, and a peak readout meter. In one embodiment, two ganged unloaded potentiometers are employed while another embodiment comprises an automaticnulling RF power bridge circuit with a variable rather than a fixed bridge reference resistance. A third embodiment comprises a calorimeter with a varible rather than a fixed resistor, while in another embodiment attenuator pads with variable resistors are employed.

Oakley, E. C.↗
DOE OSTI2013

An Efficient RF Source for Jlab

We propose the development of a highly reliable high efficiency RF source for JLAB with a lower lifetime cost operating at 80% efficiency with system operating costs of about 0.7M$/year for the 6 GeV machine. The design of the RF source will be based upon two injection locked magnetrons in a novel combining architecture for amplitude modulation and a cross field amplifier (CFA) as an output tube for the 12 GeV upgrade. A cost analysis including efficiency and reliability will be performed to determine the optimum system architecture. Several different system architectures will be designed and evaluated for a dual injection locked magnetron source using novel combining techniques and possibly a CFA as the output tube. A paper design for the 1497 MHz magnetron system will be completed. The optimum system architecture with all relevant specifications will be completed so that a prototype can be built.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

High Efficiency, Low Cost RF Sources for Accelerators and Colliders

Calabazas Creek Research, Inc. (CCR) and its collaborators are developing high efficiency, low cost RF sources. Phase and Amplitude Controlled Magnetrons: CCR, Fermilab, and Communications & Power Industries, LLC (CPI) recently developed a 100 kW, 1.3 GHz magnetron system with amplitude and phase control. The system operated at more than 80% efficiency and demonstrated rapid control of amplitude and phase. Multiple Beam Triodes: CCR, in collaboration with CPI and JP Accelerator Works, Inc., is developing 200 kW, pulsed and CW RF sources from 350 to 700 MHz with projected efficiencies exceeding 80% and cost of $0.50/Watt. Prototype tubes are scheduled for tests in spring 2021. High Efficiency Klystrons:CCR, CPI, and Leidos, Inc. are building a 1.3 GHz, 100 kW klystron operating at 80% efficiency. High power testing is scheduled for summer 2021. Multiple Beam IOTs: CCR and Georgia Tech Research Institute are developing MBIOTs with simplified input coupling and high efficiency. Simulations indicate that 3rd harmonic drive power can increase the efficiency 8-10 %. The program is developing a prototype tube to produce 200 kW peak, 100 kW average power at 704 MHz.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

High efficiency, low cost, RF sources for accelerators and colliders

Accelerators for High Energy Physics (HEP) are large users of energy, much of it in the form of radiofrequency (RF) power to accelerate particles to very high energies. Proposed HEP projects will require even larger amounts of RF energy. Increasing concerns of the cost and availability of energy will require the HEP community to use energy as efficiently as possible. Successful transfer of HEP technology to the public and private sectors will be most effective if it is highly efficient. Historically, the HEP community has utilized available RF power sources, mainly in the form of vacuum tube technology, much of which was developed during the cold war or is otherwised used in the private sector. The private sector is moving to solid-state RF sources which do not exhibit the electrical efficiency that is needed for future HEP projects. Here we summarize the state of the development of a number of RF sources that promise efficiencies of 80% and above. We also outline future efforts that are needed to fully realize the potential of these sources.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

H - Ion Source RF Plasma Testing with 13 MHz and 27 MHz at the Spallation Neutron Source (SNS)

The baseline RF-driven H⁻ ion source configuration at the Spallation Neutron Source (SNS) facility uses a continuous wave (CW) 600 W 13 MHz RF system to ignite and maintain a low-density plasma inside the ion source vacuum chamber. After the continuous low-density 13 MHz plasma has been established, a pulsed (typical 1 ms pulse width and 60 Hz pulse repetition rate) 80 kW 2 MHz RF system is used to increase the plasma density to produce the pulsed H⁻ ion beam. Incremental upgrades and improvements to the SNS ion source systems have resulted in the ability to reliably operate an H⁻ ion source for SNS neutron production run cycles that can last up to four months. Conditions inside the SNS H⁻ ion source evolve throughout a four-month run cycle due to changes in impurity levels, sputtering, and erosion. As the internal ion source conditions change during the run cycle, there can also be changes in plasma stability and the 13 MHz RF power level required to ignite the plasma. This paper presents the preliminary results of testing performed on the SNS Ion Source Test Stand (ISTS) system where we looked at plasma ignition and plasma stability using 27 MHz RF in place of the baseline 13 MHz RF system.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Multiple Beam Triode Driven RF Sources for Accelerator Applications Phase I Final Report

Calabazas Creek Research, Inc, (CCR), in collaboration with Microwave Power Products, Inc. (MPP), formerly Communications & Power Industries, LLC (CPI,) and JP Accelerator Works, Inc. (JPAW), embarked on a program to develop multiple beam triodes to produce RF power from 350 – 800 MHz with an average power exceeding 200 kW. The effort was motivated by the performance of a triode-based RF source which produces 25 kW of UHF power at 90% efficiency. The CCR effort focused on implementing this technology into a multiple beam device to increase the output power while retaining the low cost, compact size, and high efficiency. The program performed extensive simulations indicating that the goals could be achieved, and a prototype multiple beam triode was built, baked, and tested. Unfortunately, a grid to cathode short terminated the testing before the tube could generate RF power. Nevertheless, the effort demonstrated that a multiple beam triode could be designed, built, baked, and energized to high voltage. The multiple beam triode used oxide cathodes, which are only capable of pulsed operation. The multiple beam triode will be rebuilt using dispenser cathodes, which will allow high duty or continuous operation. The grids were also modified to be more robust to avoid previous issues. The MB triode will provide the beam power for RF generation. The RF is generated by surrounding the triode with input and output cavities to convert beam power to RF power. RF cavities to generate 200 kW CW at 350-450 MHz using the MB triode with dispenser cathodes was assembled during the program. The next Phase of this effort is to assemble the multiple beam triode using the subassemblies built in the Phase I program and test with the RF cavities. The Phase I program also initiated design of a higher frequency, higher power multiple beam triode. That design is forecast to produce approximately 500 kW CW from 350 - 500 MHz.

43 PARTICLE ACCELERATORS↗
DOE OSTI2023

Demonstration of Magnetron as an Alternative RF Source for SRF Accelerators

Magnetron has been considered as alternate high-efficiency, low-cost RF sources for linacs and storage rings [1] for national labs and industrial applications. After the demonstration of magnetrons power to drive and combine for a radio frequency cavity at 2450 MHz in CW mode, we have used trim coils adding to a water-cooled magnetron and amplitude modulation feedback to further suppress the side-band noise to -46.7 dBc level. We also demonstrated the phase-locking to an industrial grade cooking magnetron transmitter at 915 MHz with a 75 kW CW power delivered to a water load by using a -26.6 dBc injection signal [2]. The sideband noise from the 3-Phase SCRs DC power supply can be reduced to -16.2 dBc level. Further noise reduction and their power combining scheme using magic-tee and cavity type combiners for higher power application (2x75kW) are to be presented. We intent to use one power station to drive the normal conducting and superconducting RF cavities for the inductrial linac. We also going to demonstarte a vertical SRF cavity test with a high input coupling Q using a 2.45GHz magnetron and comparing with a baseline test result using a solid state amplifier.

Wang, H.↗
DOE OSTI2019

Magnetron R&Ds for High Efficiency CW RF Sources of Particle Accelerators

A proof of principle experiment carried out at JLab's magnetron R&D test stand has demonstrated a -25dB injection signal to phase lock a 2.45GHz 1.2kW CW magnetron within 2.1 Hz of root mean square deviation (RMSD) value with the optimization of magnetic field trimming of ±25% in order to overcome the frequency pushing of more than 4MHz in the RF power output range of 45-100%. In addition, a test stand for a newly built 1497 MHz, 13kW, CW magnetron prototype is ready for the high power injection test with outcome aimed for the CEBAF klystron replacement. Based on these R&D results, a 915MHz, 2?75kW CW commercial heating type magnetron system is being developed as high efficiency (>80%) RF source to drive an electron linac for industrial applications.

Wang, H.↗
DOE OSTI2017

Characteristics of a high-power RF source of negative hydrogen ions for neutral beam injection into controlled fusion devices

An injector of hydrogen atoms with an energy of 0.5–1 MeV and equivalent current of up to 1.5 A for purposes of controlled fusion research is currently under design at the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences. Within this project, a multiple-aperture RF surface-plasma source of negative hydrogen ions is designed. The source design and results of experiments on the generation of a negative ion beam with a current of >1 A in the long-pulse mode are presented.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

Neutral particle dynamics in a high-power RF source

Previous studies on the spatial discharge structure in the SPIDER source of negative hydrogen/deuterium ions carried out at low applied power are extended towards description of the discharge maintenance under the conditions of the actual rf power deposition of 100 kW planned for a single driver of the source. In addition to the expected higher electron density, the results show strong increase of the electron temperature and of the temperatures of the neutral species (hydrogen atoms and molecules). In the discussions, not only the spatial distribution of the plasma parameters but also that of the fluxes in the discharge (particle and energy fluxes) is involved. The obtained results come in confirmation of basic concepts for low-pressure discharge maintenance: (i) mutually related electron density and temperature as a display of the generalized Schottky condition, (ii) discharge behavior governed by the fluxes, i.e. strong nonlocality in the discharge, and (iii) a non-ambipolarity in the discharge regime, which originates from shifted maxima of the electron density and temperature and shows evidence in a vortex electron flux and in a dc current in a rf discharge, the latter resulting from a shift in the positions of the maxima of the electron density and plasma potential.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

RF Sources for Electron Accelerators With a focus on high-duty-factor, low-to-moderate energy architectures

A charged particle, such as an electron or a proton, is accelerated through its interaction with either a static (DC) or time-varying (RF) electric field. The magnitude of the accelerating field, or gradient, is typically given in units of volts per meter; in charged-particle accelerators, fields are usually expressed as kV/m or MV/m. The energy of the accelerated particle is usually expressed in terms of electron volts, or eV. An electron starting at rest at ground potential, and accelerated to an electrode with a potential of 1 kV, will have an energy of 1 keV.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

SU-E-J-71: Feasibility Study On MRI-Based BANG3 Gel Dosimetry Using Dual-Source Parallel RF Transmission System

Purpose: In this work, we present the feasibility of use of the parallel RF transmission with multiple RF source (MultiTransmit) imaging in MRI-based polymer gel dosimetry. Methods: The commercially available BANG3 gel was used for gel dosimetry. Spin-spin relaxation rate R2 was used to quantify the absorbed dose. The image quality (signal-to-noise ratio, SNR; image uniformity) and B1 field inhomogeneity between conventional single-source and MultiTransmit MR imaging were compared. Finally, the estimated R2 uncertainty σ(R2) and dosimetric performance (i.e., dose resolution) between conventional single-source and MultiTransmit MR imaging were compared. Results: Image quality and B1 field homogeneity within each calibration vial and large phantom was statistically better in MultiTransmit imaging than in conventional single-source RF transmission imaging (P < 0.005 for all calibration vials). In particular, σ(R2) (defined as the standard uncertainty of R2) was lower on the MultiTransmit images than on the conventional single-source images. Furthermore, the MultiTransmit measurement gives a lower than that obtained using the conventional single-source method. Conclusion: The improved image quality and B1 homogeneity resulted in reduced dose uncertainty (i.e., σ(R2) and dose resolution) in MRI-based polymer gel dosimetry, suggesting that MultiTransmit MR imaging has potential benefits for use in clinical 3D gel dosimetry without the need for the complicated B1 field correction method.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

A collisional radiative model for caesium and its application to an RF source for negative hydrogen ions

A collisional radiative (CR) model for caesium atoms in low-temperature, low-pressure hydrogen-caesium plasmas is introduced. This model includes the caesium ground state, 14 excited states, the singly charged caesium ion and the negative hydrogen ion. The reaction probabilities needed as input are based on data from the literature, using some scaling and extrapolations. Additionally, new cross sections for electron collision ionization and three-body recombination have been calculated. The relevance of mutual neutralization of positive caesium ions and negative hydrogen ions is highlighted: depending on the densities of the involved particle species, this excitation channel can have a significant influence on the population densities of excited states in the caesium atom. This strong influence is successfully verified by optical emission spectroscopy measurements performed at the IPP prototype negative hydrogen ion source for ITER NBI. As a consequence, population models for caesium in electronegative low-temperature, low-pressure hydrogen-caesium plasmas need to take into account the mutual neutralization process. The present CR model is an example for such models and represents an important prerequisite for deducing the total caesium density in surface production based negative hydrogen ion sources.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗