Abstract
The U.S. Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is the world's most powerful accelerator-driven pulsed neutron source. An H- injector feeds the accelerator with high current (>50 mA), time structured (1ms, 60 Hz) H- beam. The injector consists of an RF-driven, Cs-enhanced H- ion source and an electrostatic low energy beam transport section. In the recent three run cycles, an H- ion source operated 1/44 months for each run with excellent availability near 99.9%. The presently ongoing run is also on track to finish another 1/44 months run with similar high availability. Lately, we have tested a solid-state RF system for the ion source to replace the existing vacuum-tube type RF amplifier for the sake of improving the ease of operation and maintenance. Progress has also been made on the continued development of an external antenna RF H- ion source with a focus on improvement to its plasma ignition scheme.
| Original language | English |
|---|---|
| Article number | 012044 |
| Journal | Journal of Physics: Conference Series |
| Volume | 2244 |
| Issue number | 1 |
| DOIs | |
| State | Published - Apr 25 2022 |
| Externally published | Yes |
| Event | 19th International Conference on Ion Sources, ICIS 2021 - Virtual, Online Duration: Sep 20 2021 → Sep 24 2021 |
Funding
The U.S. Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is the world’s highest power accelerator-based pulsed neutron facility. Typically, the SNS accelerator delivers ~35GW of instantaneous power proton pulses to a mercury target for a duration of ~700-800 ns at 60 Hz (average power ~1.4 MW) producing intense, short-pulse neutrons for scientific research for a broad range of disciplines, such as physics, chemistry, biology, and materials science. The accelerator system of the SNS consists of a 65 keV H- injector, a 2.5 MeV RFQ, a 1-GeV linac chain (DTL-CCL-SCL), and a proton accumulator ring. The accumulator ring requires ~35 mA, time-structured (60 Hz, 1.0-ms with ~200-300 ns chopped for every ~1 !s) H- beam delivered from the linac. The H- injector produces and delivers the beam current with the required time structure to the RFQ accelerator. Depending on the operation power of the RFQ, the injector is required to deliver beam current varying from ~40 mA to ~60 mA to achieve ~35 mA in the linac. The H- injector includes an RF-driven, Cs-enhanced, multi-cusp H- ion source and a compact, two-lens electrostatic Low Energy Beam Transport (LEBT) system. Figure 1 shows a schematic view of the H- injector coupled to the RFQ accelerator. The ion source plasma is driven by a 2-MHz RF through a 2.5-turn porcelain-coated, water-cooled, copper-tube antenna which is placed internally in the ion source chamber. Typically, the 2-MHz RF is operated at 60 Hz with 1 ms pulse length with 40-65 kW to generate the required H- beam. To facilitate fast and reliable ignition of the 2-MHz high-density pulsed plasma, a continuous, low power (typically ~300W) 13.56-MHz RF maintains a low-density background plasma in the chamber. A solid reaction cesium dispenser system (Cs2CrO4 + Zr, Al) is used for ion source cesiation. A Mo cone attached to the ---------------------------------------------------------------------------------------------------------------------------This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The publisher acknowledges the US government license to provide public access under the DOE Public Access Plan (http://energy.gov/downloads/doe-public-
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