A5101454915- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Gyrotron and Vacuum Electronics Research
- Superconducting Materials and Applications
- Nuclear Physics and Applications
- Magnetic confinement fusion research
- Plasma Diagnostics and Applications
- Microwave Engineering and Waveguides
- Muon and positron interactions and applications
- Photonic and Optical Devices
- Advanced X-ray Imaging Techniques
- Micro and Nano Robotics
- Radiation Detection and Scintillator Technologies
- Atomic and Subatomic Physics Research
- Electromagnetic Simulation and Numerical Methods
- High-pressure geophysics and materials
- Advanced Fiber Laser Technologies
- Energy Harvesting in Wireless Networks
- Pulsed Power Technology Applications
- Spacecraft and Cryogenic Technologies
- Mechanical and Optical Resonators
- Nuclear reactor physics and engineering
- Antenna Design and Analysis
- Radiation Effects in Electronics
- Electromagnetic Scattering and Analysis
Oak Ridge National Laboratory
2012-2024
Spallation Neutron Source
2002-2024
Indiana University Bloomington
2020
University of Missouri
2020
Muons (United States)
2015
Fermi Research Alliance
2015
Argonne National Laboratory
1994-2002
Advanced Photon Source
2002
Since 2009, the Spallation Neutron Source (SNS) has been producing neutrons with ion beam powers near 1 MW, which requires extraction of ∼50 mA H− ions from source a ∼5% duty factor. The 50 are achieved after an initial dose ∼3 mg Cs and heating collar to ∼170 °C. normally persist for entire 4-week service cycles. Fundamental processes reviewed elucidate persistence SNS beams without steady feed why temperature may have be kept 170
The propagation characteristics of twisted hollow waveguides are considered, and various analysis methods proposed. It is shown that a waveguide can support waves travel at speed slower than the light <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</i> . These modes particular interest, as slow wave structures have many potential applications in accelerators electron traveling tubes. Since there no exact closed form solution for electromagnetic...
Despite the challenges, neutron resonance spin echo still holds promise to improve upon for measurement of slow dynamics in materials. We present a bootstrap, radio frequency flipper using high temperature superconducting technology capable flipping with either nonadiabatic or adiabatic modes. A 2 MHz has been achieved, which would achieve an effective field integral 0.35 T m meter separation spectrometer at current device specifications. In bootstrap mode, self-cancellation Larmor phase...
The U.S. Spallation Neutron Source (SNS) is an accelerator-based, pulsed neutron-scattering facility, currently in the process of ramping up neutron production. In order to ensure that SNS will meet its operational commitments as well provide for future facility upgrades with high reliability, we are developing a rf-driven, H(-) ion source based on water-cooled, ceramic aluminum nitride (AlN) plasma chamber. To date, early versions this have delivered 42 mA front end and unanalyzed beam...
The operational lifetime of a radio-frequency (rf) ion source is generally governed by the length time insulating structure protecting antenna survives during exposure to plasma. Coating with thin layer material common means extending life such antennas. When low-power/low-duty factor rf excitation employed, lifetimes several hundred hours are typical. high-power, &gt;30 kW, and high-duty cycles, ∼6%, as case Spallation Neutron Source (SNS) source, becomes unacceptably short. This work...
The Spallation Neutron Source (SNS) makes use of superconducting cavities for the acceleration negative H ions in main linac. Two types 6-cell Niobium are used portion linac: 33 /spl beta/=0.61 and 48 beta/=0.81 cavities. Each cavity is powered via a coaxial fundamental power coupler (FPC) simple yet robust design. electromagnetic design components that has been modeled some those properties have measured experimentally. Modeling includes impedance matching window waveguide to doorknob...
The U.S. Spallation Neutron Source (SNS) now operates with ∼1 MW of beam power to target the near-term goal delivering 1.4 MW. Plans are being considered incorporate a second station into facility which will require ∼2.8 power. Presently, H− pulses (∼1 ms, 60 Hz) produced by an RF-driven, Cs-enhanced, multi-cusp ion source injects RFQ (Radio Frequency Quadrupole) accelerator that, in turn, feeds SNS Linac. Currently source/RFQ system delivers ∼35 mA pulsed current linac is mostly sufficient...
The Spallation Neutron Source (SNS) makes use of 33 medium beta (0.61) and 48 high (0.81) superconducting cavities. Each cavity is equipped with a fundamental power coupler, which should withstand the full klystron 550 kW in reflection for duration an RF pulse 1.3 msec at 60 Hz repetition rate. Before assembly to cavity, vacuum components coupler are submitted acceptance procedures consisting preliminary quality assessments, cleaning clean room assembly, leak checks baking under vacuum,...
The analysis of neutron diffraction experiments often assumes that neutrons are elastically scattered from the sample. However, there is growing evidence a significant fraction detected in fact inelastically scattered, especially soft materials and aqueous samples. Ignoring these inelastic contributions gives rise to inaccurate experimental results. To date, has been no simple method with broad applicability for signal separation experiments. Here, we present robust believe could be suited...
The Oak Ridge National Laboratory operates the Spallation Neutron Source, consisting of a H− ion source, 1 GeV linac and an accumulator ring. accumulated &lt;1 μs-long, ∼35 A beam pulses are extracted from ring at 60 Hz directed onto liquid Hg target. Spalled neutrons to ∼20 world class instruments. Currently, facility routinely with ∼1.2 MW average power, which soon will be raised 1.4 MW. future upgrade second target station calls for raising power 2.8 This paper describes status two...
The quadrupole and dipole modes frequencies can be very close in a long four-vane RFQ as structure length increases. This requires extra mode stabilizer design to improve field stability, which may add system complexity cost. Therefore, we investigate other designs have potential advantages different spectrum. These are realized by modifying the cut-back scheme folded-dipole (FD) or double-dipole (DD) RFQs. In this paper, spectrums of these structures further investigated function properties...
The LANSCE accelerator is currently powered by a filament-driven, biased converter-type H- ion source that operates at 10%, the highest plasma duty factor for this type of source, using only ∼2.2 SCCM H2. needs to be replaced every 4 weeks, which takes up days. measured negative beam current 12-16 mA falls below desired 24 acceptance LANCSE accelerator. SNS (Spallation Neutron Source) RF-driven, injects ∼50 into 60 Hz with 6% and an availability >99.5% but requires ∼30 Up 7 A h have been...
The U.S. Spallation Neutron Source (SNS) is a state-of-the-art neutron scattering facility delivering the world's most intense pulsed beams to wide array of instruments which are used conduct investigations in many fields science and engineering. Neutrons produced by spallation liquid Hg due bombardment short (∼1µs), (∼35 A) pulses protons delivered at 60 Hz from storage ring fed high-intensity, 1 GeV H− LINAC. This has operated almost continuously since 2006, with ion source performance...
The cryomodule tests are on going to have better understandings of physics as a whole and eventually provide safe reliable operation for neutron production. Some features revealed be interesting issues need more attentions than expected, such operating condition, collective effects between cavities, HOM coupler issues, end-group stability, cavity-coupler interactions, vacuum/gas physics, waiting investigations. Up now SNS cryomodules were mainly tested at 2.1 K/4.4 K, 10 pulse per second...
The Spallation Neutron Source (SNS) radio-frequency quadrupole (RFQ) had resonance control instabilities at duty factors higher than approximately 4%. Systematic investigations have been carried out to understand the cause of instability and ensure operational stability RFQ. most critical source is revealed be an interaction between hydrogen released by beam bombardments RFQ rf field resulting in a discharge, which consumes additional power could operate unstable region. This paper reports...
The Spallation Neutron Source H− ion source is operated with a pulsed 2-MHz RF (50-60 kW) to produce the 1-ms long, ∼50 mA beams at 60 Hz. A continuous low power (∼300 W) 13.56-MHz plasma, which initially ignited H2 pressure bump, serves as starter plasma for high discharges. To reduce risk of outages lower flow rates desired improved performance following radio frequency quadrupole, matching network was characterized over broad range its two tuning capacitors. H-α line intensity and...
RF Test Facility (RFTF) has been constructed to support present and future needs in testing, processing conditioning of various high power components normal conducting superconducting systems at the SNS. The facility is expected have additional subsystems that are needed for complete (SRF) testing processing. A full capacity voltage converter modulator (HVCM) with 11 MW peak 8% duty cycle installed driving one or two klystron amplifiers. waveguides completed WR-2100 WR-1150 402.5 MHz 805...
The U.S. Spallation Neutron Source (SNS) will require substantially higher average and pulse H− beam currents than can be produced from conventional ion sources such as the base line SNS source. of 40–50mA (SNS operations) 70–100mA (power upgrade project) with a rms emittance 0.20–0.35πmmmrad ∼7% duty factor needed. We are therefore investigating several advanced source concepts based on rf plasma excitation. First, performance characteristics an external antenna Al2O3 chamber combined...
<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Charged-particle accelerators use various vacuum windows on their accelerating radio-frequency (RF) cavities to throughput very high RF power. Before being placed the cavities, should be cleaned, baked, and fully conditioned prevent a poor from outgassing, as well other forms of contamination. An example is coaxial fundamental power coupler (FPC) with an annular alumina ceramic window for each 81...
The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory reached 1‐MW of beam power in September 2009, and now routinely operates near for the production neutrons. This paper reviews performance, operational issues, implemented planned mitigations SNS H− ion source to support such high power‐level beams with availability. Some results from R&D activities are also briefly described.
Electromagnetic modeling of the multicusp external antenna H(-) ion source for Spallation Neutron Source (SNS) has been performed in order to optimize high-power performance. During development SNS source, failures due high voltage and magnet holder rf heating concerns under stressful operating conditions led characteristics analysis. In simulations, plasma was modeled as an equivalent lossy metal by defining conductivity sigma. Insulation designs along with material selections such ferrite...
The U.S. Spallation Neutron Source (SNS) is a state-of-the-art neutron scattering facility delivering the world's most intense pulsed beams to wide array of instruments, which are used conduct investigations in many fields engineering, physics, chemistry, material science, and biology. Neutrons produced by spallation liquid Hg bombardment short (∼1 µs), (∼35 A) pulses protons delivered at 60 Hz an accumulator ring fed high-intensity, 1 GeV, H- LINAC (linear accelerator). This has operated...