The Spallation Neutron Source (SNS) is being designed, constructed, installed and commissioned by the staff of six national laboratories, Argonne National Laboratory, Brookhaven National Laboratory, Jefferson National Accelerator Laboratory, Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, and Oak Ridge National Laboratory. The accelerator systems are designed to deliver a 695 ns proton-pulse onto a mercury target at a 60-Hz repetition rate and an average power of 2-MW. Neutron moderators that will convert the spallation neutrons into slow neutrons for material science research will surround the target. The Front-End systems are designed to generate an H- beam of minipulses, 68% beam on, 32% beam off every 965 ns, at 2.5 MeV for 1 ms, 60 times a second. The Front-End systems include a RF driven, volume-production ion source, beam chopping system, RFQ, and beam transport. The ion source will have to achieve about 65 mA to deliver 52 mA at the input to the linac. The linac consists of a drift tube linac up to 86.8 MeV, a coupled-cell linac to 185 MeV, and a superconducting RF linac to the nominal energy of 1 GeV. The design of the superconducting section includes 11 cryomodules with three, 0.61-beta cavities per cryomodule and 17 cryomodules with four, 0.81-beta cavities per cryomodule, with space to install four more 0.81-beta cryomodules. The accumulator ring is designed for charge exchange injection at full energy. The peak charge per bunch at the end of the accumulation cycle will reach 2.08x10**14 for 2-MW operation. The goal is to control beam losses to less than 1x10**-4.

An Overview of the Spallation Neutron Source Project

The Spallation Neutron Source (SNS) project is a collaboration among Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos and Oak Ridge National Laboratories. The linac, which injects beam into an accumulator ring, is comprised of both normal and superconducting RF (SRF) accelerating structures. Two room-temperature RF structures, a 402.5-MHz drift-tube linac (DTL) and an 805-MHz coupled-cavity linac (CCL), accelerate an H-minus beam from 2.5 MeV to 186 MeV. The SRF linac accelerates the beam to 1 GeV through 81 elliptical, multicell niobium cavities. This paper reviews the linac physics design and its expected beam dynamics performance.

/pdf/expected-beam-performance-of-the-sns-linac-30lfjfj12o.pdf

Expected beam performance of the SNS linac

The Spallation Neutron Source (SNS) is being designed, constructed, installed, and commissioned by the staff of six national laboratories, Argonne National Laboratory, Brookhaven National Laboratory, Jefferson National Accelerator Laboratory, Lawrence Berkeley National Laboratory, Los Alamos National Laboratory, and Oak Ridge National Laboratory. The accelerator systems are designed to deliver a 695 ns proton-pulse onto a mercury target at a 60-Hz repetition rate and an average power of 2-MW. Neutron moderators that will convert the spallation neutrons into slow neutrons for material science research will surround the target. Eighteen neutron beam lines will be available for users, although initially, only 10 instruments are planned. The FrontEnd Systems are designed to generate a 52 mA, Hbeam of minipulses, 68% beam on, 32% beam off, every 945 ns, at 2.5 MeV for 1 ms, 60 times a second. The Front-End systems include a RF driven, volumeproduction ion source, beam chopping system, RFQ, and beam transport. The linac consists of a drift tube linac up to 86.8 MeV, a coupled-cell linac to 185.7 MeV, and a superconducting RF linac to the nominal energy of 1 GeV. The design of the superconducting section includes 11 cryomodules with three, 0.61-beta cavities per cryomodule and 15 cryomodules with four, 0.81-beta cavities per cryomodule, with space to install six more 0.81-beta cryomodules. The accumulator ring is designed for charge exchange injection at full energy and will reach 2.08x10E+14 protons/pulse at 2-MW operation. The goal is to reduce uncontrolled beam losses to less than 1x10E-4. A detailed overview of the accelerator systems and progress at the various laboratories will be presented.

/pdf/an-overview-of-the-spallation-neutron-source-project-4ve3feno05.pdf

The SNS is a spallation neutron research facility being built at Oak Ridge National Laboratory in Tennessee [1]. The Linac portion of the SNS (with the exception of the superconducting cavities) is the responsibility of the Los Alamos National Laboratory (LANL), and this responsibility includes the RF system for the entire linac. The linac accelerates an average beam current of 2 mA to an energy of 968 MeV. The linac is pulsed at 60 Hz with an H beam pulse of 1 ms. The first 185 Mev of the linac uses normal conducting cavities, and the remaining length of the linac uses superconducting cavities [2]. The linac operates at 402.5 MHz up to 87 MeV and then changes to 805 MHz for the remainder. This paper gives an overview of the Linac RF system. The overview includes a description and configuration of the high power RF components, the HV converter/modulator, and the RF controls. Issues and tradeoffs in the RF system will be discussed, especially with regards to the use of pulsed superconducting cavities. Figure 1: SNS Linac configuration. 1 OVERVIEW OF SNS LINAC The SNS Linac is a nominal 968 MeV, 2 mA average, H accelerator (Figure 1). The system provides 52 mA peak at 1 ms pulse width and a 60 Hz repetition rate. The beam is chopped with a 68% chopping factor, for an average beam during the pulse of 36 mA. The accelerator begins with an injector and RFQ (from Berkeley), then a Drift Tube Linac (DTL) to 86.8 MeV, followed by a Coupled-Cavity Linac (CCL) to 186 MeV. Los Alamos is responsible for the DTL and CCL structures and all of the linac RF systems. The remaining part of the accelerator uses superconducting cavities (from Jefferson Laboratory), using s=0.61 cavities to 375 MeV, then s=0.81 cavities to 968 MeV. The RFQ and DTL operate at 402.5 MHz, and the CCL and superconducting cavities operate at 805 MHz. The different structures and frequencies require that 3 different types of klystrons be used. The RFQ and DTL will use 2.5 MW peak klystrons at 402.5 MHz. The CCL *Work supported by the US Department of Energy will use 5 MW peak klystrons at 805 MHz, and the superconducting cavities will use 550 kW klystrons at 805 MHz. The types and quantities and applications are listed in Table 1. Table 1: Types and quantities of klystrons and HV systems for the SNS Linac H Energy 968 MeV Average beam during pulse 36 mA Pulse Width 1 ms Rep Rate 60 Hz Klystrons 402.5 MHz, 2.5 MW pk (includes 1 for RFQ , 6 for DTL) 805 MHz, 5 MW pk (includes 4 for CCL, 2 for HEBT) 805 MHz, 0.55 MW pk, SC 7

/pdf/the-spallation-neutron-source-sns-linac-rf-system-2p7jg49tep.pdf

The Spallation Neutron Source (SNS) Linac RF System

INFN Milano - LASA is involved in the development and industrialization for the production of 704.4 MHz medium beta (E = 0.67) cavities for the ESS project. In this framework, we are designing a medium beta prototype cavity exploring both Large Grain and Fine Grain Niobium for its production as well as a high beta (E = 0.86) Large Grain cavity. In the meanwhile, an activity is ongoing for upgrading the LASA test facility to be able to test these kind of resonators.

Infn milano - lasa activities for ess

The Spallation Neutron Source (SNS) linac is comprised of both normal and superconducting rf (SRF) accelerating structures. The SRF linac is accelerates the beam from 186 to 1250 MeV through 117 elliptical, multi-cell niobium cavities. This paper describes the SRF linac architecture, physics design considerations, cavity commissioning, and the expected beam dynamics performance.

/pdf/superconducting-linac-for-the-sns-2dtpdadfmk.pdf

Superconducting Linac for the SNS

The Spallation Neutron Source (SNS) is designed to ultimately reach an average proton beam power of 2 MW for pulsed neutron production. The SNS physics groups analyze the machine performance within the hardware constraints, optimize the accelerator design, and establish the best path towards a 2 MW and higher Spallation Neutron Source.

/pdf/design-optimization-and-the-path-towards-a-2-mw-spallation-4xd32nquir.pdf

Design optimization and the path towards a 2 MW Spallation Neutron Source

A High Intensity Linac for the National Spallation Neutron Source

The Spallation Neutron Source (SNS) linac will deliver a 1.0 GeV proton beam to its accumulator ring. The normal conducting segment of the linac has a radio frequency quadrupole (RFQ), six drift tube linac (DTL) tanks powered by seven 402.5 MHz klystrons and four coupled cavity linac (CCL) modules powered by four 805 MHz klystrons that deliver the 180 MeV beam to the superconducting section of the linac (SCL) that employs eighty one 6-cell cavities powered by eighty-one 805 MHz klystrons. The normal conducting accelerating linac segment has been completely installed in the linac tunnel and successfully conditioned and commissioned. Corresponding high voltage converter modulator (HVCM) and low level RF (LLRF) control systems have been installed and tested.

Installation and Testing for Commissioning of Normal Conducting RF Linac Segment in the SNS

Expected Beam Performance of the SNS Linac (Invited)

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