| Paper | Title | Page |
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| TU1004 | Development of High-Current, High-Duty-Factor H- Injectors | 213 |
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| SNS, FNAL, and CERN have projects that require the production of H- beams with increased intensity and increased duty factors. The most demanding requirements are set by SNS, which plans to upgrade its power to 3 MW. This power level requires a LINAC peak current of 59 mA, which results from an RFQ input current between 67 and 95mA when injecting with rms-emittances between 0.20 and 0.35 Pi-mm-mrad, respectively. Predicted downstream losses exclude the use of higher emittance beams. Ion source lifetime and reliability requirements are also stringent to meet the 99.5% availability goal for the injector of a user facility with 95% availability. LEBT options are currently being studied to optimally match the ion source output into the RFQ with a minimal distortion of the beam emittance. Several ion source and LEBT options under consideration will be discussed. | ||
| MOP045 | Performance of SNS Front End and Warm Linac | 145 |
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| The Spallation Neutron Source accelerator systems will deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60Hz repetition rate with 38 mA peak current, a 1 GeV linear accelerator, an accumulator ring and associated transport lines. The 2.5MeV beam from the Front End is accelerated to 86 MeV in the Drift Tube Linac, then to 185 MeV in a Coupled-Cavity Linac and finally to 1 GeV in the Superconducting Linac. With the completion of beam commissioning, the accelerator complex began operation in June 2006. Injector and warm linac performance results will be presented including transverse emittance evolution along the linac, longitudinal bunch profile measurements at the beginning and end of the linac, and the results of a beam loss study. | ||
| TUP053 | Initial Tests of an Elemental Cs-System for the SNS Ion Source | 364 |
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| The ion source employed in the Spallation Neutron Source* (SNS) is an RF-driven, Cs-enhanced, multi-cusp H- source. To date, the source has been successfully utilized in the commissioning of the SNS accelerator producing 10–40 mA. Presently, Cs is dispensed within the source using Cs2CrO4 cartridges located in an air heated/cooled cylindrical collar surrounding the outlet aperture. The temperature of the collar is elevated to release Cs into the source. Typically, this process can only be repeated 2-3 times before the Cs is depleted and the source needs to be replaced. In addition, the dispensers are subject to poisoning by the residual gases in the source leading to beam decay. This is especially problematic at high duty-factor. This report describes the design of an elemental Cs system incorporating an external reservoir based on the proven Fermilab system. Source performance is characterized and compared for both the original and the elemental Cs systems. | ||
| TUP054 | A Proposed Helicon Driver for the SNS Ion Source | 367 |
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| The H- ion source employed in the Spallation Neutron Source* (SNS) is an RF-driven, multi-cusp source, which utilizes a helical antenna to inductively couple power into the source plasma. To date, the source has been successfully utilized in the commissioning of the SNS accelerator producing 10–40 mA of H- with duty-factors of ~0.1%. Ultimately, the SNS facility will require beam duty-factors of 6% and ~60 mA of H- injecting the linac. This may require currents of up to ~100 mA from the source depending on the ion source emittance. To date, the SNS source has only delivered sustained currents of ~33 mA at full duty factor. Therefore, we are developing plasma generators capable of achieving much higher plasma densities. Plasmas generated through helicon-wave coupling can develop densities up to 100 times greater than those produced by conventional inductive coupling. This report presents an initial design and discusses considerations for a source which combines the forward portion of the SNS source with a helicon system. The helicon system consists largely of components retrofitted from the proven hydrogen VASIMR system employed in space propulsion. | ||
| TUP055 | A Plasma Gun Driver for the SNS Ion Source | 370 |
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The ion source developed for the Spallation Neutron Source (SNS) is an RF-driven, multi-cusp source designed to produce ~ 40 mA of H- with a normalized rms emittance of less than 0.2 π mm mrad. To date, the source has been successfully utilized in the commissioning of the SNS accelerator producing 10–40 mA of H- with duty-factors of ~0.1%. Recently, we found the H- yield from the source could be increased dramatically with the introduction of streaming plasma particles injected into the primary RF plasma from a hemispherical glow discharge chamber located in the rear of the source. In some cases, a 50% increase in the H- beam current was observed. The system also eliminated the need for other plasma ignition systems like a secondary low-power RF generator. This report details the design of the plasma gun as well as the parametric dependence of H- current on source operating conditions. Comparisons are made with and without the gun energized. Finally, an off-line test stand was employed to characterize the plasma current emitted directly from the gun as well as perform lifetime characterization.
SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U. S. Department of Energy. |
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| TUP056 | The Development of a High-Power, H- Ion Source for the SNS-Based on an External Antenna | 373 |
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| The ion source developed for the Spallation Neutron Source* (SNS) is a radio frequency, multi-cusp H- source, which utilizes an internal antenna immersed within the source plasma. To date, the source has been utilized successfully in commissioning of the SNS accelerator delivering 10 - 40 mA with duty-factors of ~0.1% for periods of several weeks. Ultimately, the SNS facility will require beam currents of ~60 mA at 6% duty-factor. Tests have shown that the internal antenna is susceptible to failure at this duty-factor. Currently, two ion sources are being developed which feature ceramic plasma chambers surrounded by an external antenna. The first is a low-power, test version which employs a high-inductance external antenna and produces considerably higher H- beam currents than the original SNS source when both are operated without Cs. The second is a high-power version which features a Faraday shield with an integrated magnetic confinement structure and is designed to operate at full duty factor. The performance of this source should also greatly exceed that of the present SNS source. Details of the design and the measured performance of each source are discussed. |