[en] Short communication

[en] Short communication

[en] The design of the Spallation Neutron Source (SNS) prototype low-energy beam transport (LEBT) system is discussed. This LEBT must transfer 35 mA of H^- current from the ion source outlet aperture to the entrance of the radio-frequency quadrupole (RFQ). The plasma generator is a radio frequency-driven multicusp source, operated at 6% duty factor (1 ms, 60 Hz). The entire LEBT configuration is electrostatic, with a high-voltage extraction gap followed by two sets of einzel lenses. The second einzel lens will be split into four quadrants to permit the application of transverse steering and beam chopping fields. The H^- ion source emits a gas flow into the LEBT that must be efficiently pumped to reduce stripping losses of the H^- ions. Therefore, an efficient electrode design is incorporated to reduce the gas pressure between the electrodes. Alignment requirements and related issues will also be discussed

[en] An RFQ-based neutron generator system is described that produces pulsed neutrons for the active screening of sea-land cargo containers for the detection of shielded special nuclear materials (SNM).A microwave-driven deuteron source is coupled to an electrostatic LEBT that injects a 40 mA D+ beam into a 6 MeV, 5.1 meter-long 200 MHz RFQ.The RFQ has a unique beam dynamics design and is capable of operating at duty factors of 5 to 10 percent accelerating a D+ time-averaged current of up to 1.5 mA at 5 percent duty factor, including species and transmission loss. The beam is transported through a specially-designed thin window into a 2.5-atmosphere deuterium gas target. A high-frequency dipole magnet is used to scan the beam over the long dimension of the 5by 35 cm target window. The source will deliver a neutron flux of 1 cdot107 n/(cm2s) to the center of an empty cargo container. Details of the ion source, LEBT, RFQ beam dynamics and gas target design are presented

[en] Advanced neutron interrogation systems for the screening of sea-land cargo containers for shielded special nuclear materials (SNM) require a high-yield neutron source to achieve the desired detection probability, false alarm rate, and throughput. An accelerator-driven neutron source is described that produces a forward directed beam of high-energy (up to 8.5 MeV) neutrons utilizing the D(d,n) 3He reaction at deuteron beam energies of up to 6 MeV. The key components of the neutron source are a high-current RFQ accelerator and an innovative neutron production target. A microwave-driven deuteron source is coupled to an electrostatic LEBT that injects a 40 mA D+-beam into a 6 MeV, 5.1 meter-long, 200 MHz RFQ. The RFQ is based on an unusual beam dynamics design and is capable of operating at a duty factor that produces more than 1.2 mA time average beam current. The beam is transported to a 2-atmosphere deuterium gas target with a specially-designed, thin entrance window. A high-frequency dipole magnet is used to spread the beam over the long dimension of the 4 by 35 cm target window. The source will be capable of delivering a neutron flux of ∼2 x 107 n/(cm2 x s) to the center of a sea-land cargo container and is expected to satisfy the requirements for full testing and demonstration of advanced neutron interrogation techniques based on stimulated SNM signatures

[en] The Front-End Systems (FES) of the Spallation Neutron Source (SNS) project have been described in detail elsewhere [1]. They comprise an rf-driven H^- ion source, electrostatic LEBT, four-vane RFQ, and an elaborate MEBT. These systems are planned to be delivered to the SNS facility in Oak Ridge in June 2002. This paper discusses the latest design features, the status of development work, component fabrication and procurements, and experimental results with the first commissioned beamline elements

[en] Advanced neutron interrogation systems for screening sea-land cargo containers for shielded special nuclear materials (SNM) require a high-yield neutron source to achieve the desired detection probability, false alarm rate, and throughput. The design of an accelerator-driven neutron source is described that utilizes the D(d,n)³He reaction to produce a forward directed beam of up to 8.5 MeV neutrons. Key components of the neutron source are a high-current radio frequency quadrupole (RFQ) accelerator and a neutron production gas target. The 5.1 m long, 200 MHz RFQ accelerates a 40 mA deuteron beam from a microwave-driven ion source coupled to an electrostatic low energy beam transport (LEBT) system to 6 MeV. At a 5% duty factor, the time-average D⁺ beam current on target is 1.5 mA. A thin entrance window has been designed for the deuterium gas target that can withstand the high beam power and the gas pressure. The source will be capable of delivering a flux >1 x 10⁷ n/(cm² s) at a distance of 2.5 m from the target and will allow full testing and demonstration of a cargo screening system based on neutron stimulated SNM signatures