This paper describes the ramp up of beam power for Spallation Neutron Source by ramping pulse length, repetition rate, and current emerging from H− source. Starting out with low rates (≤10 Hz) short lengths (≤0.2 ms), source low-energy transport delivered Lawrence Berkeley National Laboratory exceeded requirements almost perfect availability. discusses modifications that were required to exceed 0.2 ms length 0.2% duty factor acceptable availability performance. Currently, is supporting...

The Spallation Neutron Source operates reliably at 1.2 MW and will gradually ramp to 1.4 MW. This paper briefly recalls some of the struggles when unprecedented project was started ramped 1 over a 3½ year period. challenging, especially for H− ion source low-energy beam transport system, which make up injector. It took several more years push injector requirements, even longer reach close 100% availability. An additional breakthrough carefully staged, successful extension service cycle so...

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 Spallation Neutron Source (SNS) now routinely operates nearly 1 MW of beam power on target with a highly persistent ∼38 mA peak current in the linac and an availability ∼90%. H− pulses (∼1 ms, 60 Hz) are produced by Cs-enhanced, multicusp ion source closely coupled electrostatic low energy transport (LEBT), which focuses 65 kV into radio frequency quadrupole accelerator. plasma is generated RF excitation (2 MHz, ∼60 kW) copper antenna that has been encased thickness ∼0.7 mm porcelain...

Recent measurements of the H− beam current show that SNS is injecting about 55 mA into RFQ compared to ∼45 in 2010. Since 2010, exiting dropped from ∼40 ∼34 mA, which sufficient for 1 MW power. To minimize impact degradation, service cycle best performing source was extended 6 weeks. The only degradation fluctuations electron dump voltage towards end some cycles, a problem being investigated. Very recently, retuned, partly restored its transmission. In addition, electrostatic low-energy...

LBNL designed and built the Frontend for Spallation Neutron Source, including its H− source Low‐Energy Beam Transport (LEBT). This paper discusses performance of LEBT during commissioning accelerator, as well their while ramping up SNS beam power to 540 kW. Detailed discussions major shortcomings mitigations are presented illustrate effort needed take even a well‐designed R&D ion into operation. With these modifications, at 4% duty factor meets essential requirements that were set beginning project.

During the past year Spallation Neutron Source has operated with proton beam powers up to 1.4 MW good availability. However, after a recent premature target failure power was reduced 1 for ∼20-week service cycle of new target, whereas subsequent will be used at 1.2 MW. The ion source and low-energy transport deliver 50 60 mA H− beams into RFQ availbilities ∼99.5%. compromised transmission limits LINAC ∼35 mA, which is sufficient Our current injector efforts focus on improving reliability...

Spallation Neutron Source ramps to higher power levels that can be sustained with high availability. The goal is 1.4 MW despite a compromised radio frequency quadrupole (RFQ), which requires than design approach the nominal beam transmission. Unfortunately at RFQ often loses its thermal stability, problem apparently enhanced by losses and influxes of hydrogen. Delivering as much H(-) possible least amount hydrogen led plasma outages. root cause dense 1-ms long ∼55-kW 2-MHz pulses reflecting...

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...

Abstract The U.S. Spallation Neutron Source (SNS) is a state-of-the-art neutron scattering facility delivering the world’s most intense pulsed-neutron beams to wide array of instruments which are used conduct investigations in many fields science and engineering. accelerator system fed by an RF-driven, multicusp, H − ion source nominally provides pulsed beam currents 50-60 mA (1ms, 60Hz). This report discussion ongoing design improvements SNS Low Energy Beam Transport (LEBT) as well...

A simple ionization model has been used to compute metastable beam populations for atomic ions formed in low density, high electron temperature ECR plasma type ion sources. Metastable fractions each charge state of carbon, nitrogen and oxygen have evaluated. Computed are found be reasonable agreement with experimental data.

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, >30 kW, and high-duty cycles, ∼6%, as case Spallation Neutron Source (SNS) source, becomes unacceptably short. This work...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Vadim Dudnikov, B. Han, Rolland P. Johnson, S. N. Murray, T. R. Pennisi, M. Santana, Martin Stockli, F. Welton; Surface Plasma Source Electrode Activation by Impurities. AIP Conf. Proc. 26 September 2011; 1390 (1): 411–421. https://doi.org/10.1063/1.3637412 Download citation file: Ris (Zotero) Reference Manager...

A three-dimensional ion optical code IBSimu, which is being developed at the University of Jyväskylä, features positive and negative plasma extraction models self-consistent space charge calculation. The has been utilized for modeling existing system H(-) source Spallation Neutron Source. Simulation results are in good agreement with experimental data. high-current downstream electron dumping intermediate energy designed. According to simulations it provides lower emittance compared baseline...

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...

We present a self-consistent method for analyzing measured emittance data that yields unbiased estimates the root-mean-square (rms) emittance. The self-consistent, elliptical exclusion analysis uses an ellipse to determine bias from outside ellipse, before calculating rms bias-subtracted within ellipse. Increasing size until estimate saturates allows determining minimum area includes all real signals, even those buried in noise. Variations of shape and orientations are used test robustness...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Martin P. Stockli, B. X. Han, S. N. Murray, T. R. Pennisi, M. Santana, F. Welton; Towards Understanding the Cesium Cycle of Persistent H− Beams at SNS. AIP Conference Proceedings 26 September 2011; 1390 (1): 123–133. https://doi.org/10.1063/1.3637382 Download citation file: Ris (Zotero) Reference Manager...

The SNS H− ion source is a dual-frequency RF-driven (13.56-MHz low power continuous RF superimposed by 2-MHz high pulsed with ∼1.0 ms pulse length at 60 Hz), Cs-enhanced source. This paper discusses the applications of optical emission spectroscopy for plasma conditioning, cesiation, failure diagnostics, and studies build-up outage issues.

The Oak Ridge National Laboratory operates the Spallation Neutron Source, consisting of a H− ion source, 1 GeV linac and an accumulator ring. accumulated <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 ion source for the Spallation Neutron Source is a radio-frequency (rf) multi-cusp, volume-type H− that coupled to rf quadrupole accelerator through low energy beam transport (LEBT) system consisting of five electrostatic elements. To gain deeper understanding operation this and continue refine design, we have performed extraction simulations using computer code PBGUNS. A comparison presented between simulation measured phase space various values LEBT electrode potentials. Both emittance...

The U.S. Spallation Neutron Source (SNS) is the leading accelerator‐based, pulsed neutron‐scattering facility, currently in process of ramping up neutron production. In order to insure meeting operational requirements as well providing for future facility beam power upgrades, a multifaceted H‐ ion source development program ongoing. This work discusses several aspects this program, specifically design and first measurements an RF‐driven, external antenna based on A1N ceramic plasma chamber,...

The Spallation Neutron Source (SNS), a large scale neutron production facility, routinely operates with 30–40 mA peak current in the linac. Recent measurements have shown that our RF-driven internal antenna, Cs-enhanced, multi-cusp ion sources injects ∼55 of H− beam (∼1 ms, 60 Hz) at 65-kV into Radio Frequency Quadrupole (RFQ) accelerator through closely coupled electrostatic Low-Energy Beam Transport system. Over last several years decrease RFQ transmission and issues antennas has...

The Spallation Neutron Source (SNS) now routinely operates near 1 MW of beam power on target with 30-40 mA peak current in the linac and an overall availability ∼90%. H− pulses (∼1 ms, 60Hz) are produced by a RF-driven, Cs-enhanced, multi-cusp ion source closely coupled to electrostatic Low Energy Beam Transport (LEBT) which focuses into RFQ accelerator. LEBT normally have combined ∼99%. plasma is generated RF excitation (2MHz, ∼60kW) copper antenna has been encased thickness ∼0.7 mm...

The H− injector for the SNS RFQ accelerator consists of an RF-driven, Cs-enhanced ion source and a compact, two-lens electrostatic LEBT. LEBT output input beam current are measured by deflecting on to annular plate at entrance. Our method procedure have recently been refined improve measurement reliability accuracy. new measurements suggest that earlier tended underestimate currents 0-2 mA, but essentially confirm 50-60 mA being injected into RFQ. Emittance conducted test stand featuring...

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...