An in-situ technique for coating stainless steel vacuum tubes with Cu was developed to mitigate the problems of wall resistivity that leads to unacceptable ohmic heating of the cold bore of superconducting magnets and generation of electron clouds in RHIC that can limit future machine luminosity enhancement. Room temperature RF resistivity measurements indicated that 10 μm Cu coated stainless steel RHIC beam tube has a conductivity close to copper tubing. Before coating the RHIC beam pipe with copper, it is imperative to test the Cu coating’s conductivity at cryogenic temperatures to ensure coating effectiveness in lowering resistivity. A folded quarter wave resonator structure has been designed and built to be inserted inside a cryogenic system to measure the RF resistivity of copper coated RHIC tubing at liquid helium temperatures. The design is based on making the resonator structure out of a superconducting material such that the copper coating is the most lossy material. RHIC tubing samples prepared with different magnetron sputtering deposition modes are to be measured by the apparatus. Cu coating is to be optimized by iterative processes. Additionally, this device can also be used for the development of better, cheaper superconducting radio frequency (SRF) cavities and electron guns. The apparatus and its design details will be presented.

Electron cooling was proposed to increase the luminosity of the Relativistic Heavy Ion Collider (RHIC) operation for heavy ion beam energies below 10 GeV/nucleon. The electron cooling system needed should be able to deliver an electron beam of adequate quality in a wide range of electron beam energies (0.9-5 MeV). An option of using an electrostatic accelerator to produce electrons for cooling heavy ions in RHIC was evaluated in detail. In this paper, we describe the requirements and options which were considered in the design of such a cooler for RHIC, as well as the associated challenges. The expected luminosity improvement and limitations with such an electron cooling system are also discussed.

A part of a new EBIS-based heavy ion preinjector, the low energy beam transport (LEBT) section between the high current EBIS and the RFQ is a challenging design, because it must serve many functions. In addition to the requirement to provide an efficient matching between the EBIS and the RFQ, this line must serve as a fast "switchyard", allowing singly charged ions from external sources to be transported into the EBIS trap region, and extracted, highly charged ions to be deflected to off-axis diagnostics (time-of-flight or emittance). The space charge of the 5-10 mA extracted heavy ion beam is a major consideration in the design, and the space charge force varies for different ion beams having Q/m from 1-0.16. The line includes electrostatic lenses, spherical and parallel-plate deflectors, magnetic solenoid, and diagnostics for measuring current, charge state distributions, emittance, and profile. A prototype of this beamline has been built, and results of tests are presented.

The collimation system in the SNS ring includes a two-stage collimator consisting of a halo scraper and an appropriate fixed aperture collimator. This unit is placed between the first quadru-pole and the first doublet in the collimation straight section of the ring. The scraper is situated at the exact mid-point between these two magnets, and the fixed aperture collimator fills the space between the scraper and the doublet magnet. The scraper and collimator are surrounded by an outer shield structure. The downstream dose to the doublet and the attached corrector magnet will be estimated for normal operating conditions. In addition, the cooling water activation will be estimated. Finally, the dose at the flange locations will be estimated following machine shutdown.

The Spallation Neutron Source accumulator ring requires large aperture dipole magnets, strong focusing quadrupole and sextupole magnets, and low field corrector dipole, quadrupole, sextupole, and octopole magnets. All of these magnets will provide a fixed magnetic field throughout the accumulator's fill/storage/extraction cycle. Similar fixed field magnets are also being built for the beam transport lines from the linac and to the target. Because of the high intensity in the accumulator, the magnets must be built with tight tolerances for optimum field quality. Because some of the magnets are powered in strings, those magnets must have tight tolerances and consistent material properties to provide the same integral field from magnet to magnet. Radiation resistance, maintainability, and cost were other major factors in determining the magnets' design. The accumulator ring and transport line lattice design required 32 different magnet types out of the 312 magnets to be installed. This resulted in small quantity procurements that affected the cost of fabrication and testing of the magnets.

The collimation system in the SNS ring includes a two-stage collimator consisting of a halo scraper and an appropriate fixed aperture collimator. This unit is placed between the first quadru-pole and the first doublet in the collimation straight section of the ring. The entire structure is surrounded by an outer shield structure. The downstream dose to the doublet and the attached corrector magnet will be estimated for normal operating conditions. In addition, the activities of cooling water, tunnel air, and dose to cables will be estimated. The dose at the flange locations will be estimated following machine shutdown. Finally, the implied dose to surroundings during the removal of an exposed collimator will be made.

The Spallation Neutron Source accelerator will provide a 1 GeV, 1.44 MW proton beam to a liquid mercury target for neutron production. The expected highest doses to components are in the collimation regions. This paper presents the mechanical engineering design of a typical collimator highlighting the features incorporated to assist with collimator removal once it is activated. These features include modular shielding, integrated crane mounting, remote water fittings and vacuum clamps. Also presented is the design Work in progress at present to validate the remote vacuum clamp design. This includes a test rig that mimics an active handling scenario where vacuum bellows can be compressed and clamps removed/replaced from a safe distance.

A High Level RF (HLRF) system consisting of power amplifiers (PA's) and ferrite loaded cavities is being built by Brookhaven National Laboratory (BNL) for the Spallation Neutron Source (SNS) project. Four cavities were built and are being tested. Each cavity has two gaps with a design voltage of 10 kV per gap and will be driven by a PA directly adjacent to it. The PA uses a 600 kW tetrode to provide the necessary drive current. All the PA's were built and are being tested at BNL prior to shipping to ORNL. A dynamic tuning scheme used to help compensate for the effect of beam loading was implemented and tested.

Brookhaven is providing the Ring and Transfer Lines Beam Diagnostics for the Spallation Neutron Source (SNS), to be installed at Oak Ridge National Laboratory. The customary diagnostics that will be present include Beam Position Monitors (BPM), Ionization Profile Monitors (IPM), Beam Loss Monitors (BLM), Beam Current Monitors (BCM), Coherent Tune Measurement, and Wire Scanners. An overview of these systems is presented, along with brief discussions of SNS-specific problems that must be addressed, including unprecedented beam power, large dynamic range, a stringent loss budget, space charge, beam halo, and electron cloud. We also present an overview of systems more specifically tailored to address these problems, including Beam-in-Gap measurement and cleaning, two types of incoherent tune measurement, halo monitor, and video monitors for stripping foils and the electron catcher.

The Spallation Neutron Source (SNS) accumulator ring is designed to accumulate, via H- injection, protons of 2 MW beam power at 1 GeV kinetic energy at a repetition rate of 60 Hz [1]. At such beam intensity, electron-cloud is expected to be one of the intensity-limiting mechanisms that complicate ring operations. This paper summarizes mitigation strategy adopted in the design, both in suppressing electron-cloud formation and in enhancing Landau damping, including tapered magnetic field and monitoring system for the collection of stripped electrons at injection, TiN coated beam chamber for suppression of the secondary yield, clearing electrodes dedicated for the injection region and parasitic on BPMs around the ring, solenoid windings in the collimation region, and planning of vacuum systems for beam scrubbing upon operation.

The collimating system in the accumulator ring and transfer lines of the Spallation Neutron Source (SNS) project is responsible for stopping 0.1% of the 2 MW beam of 1.0 GeV protons that are in the beam halo. The collimating structures are a combination of movable beam scrapers and stationary absorbers. Specifically, pairs of charge-exchange foils or scrapers moving in-and-out of the beam in the vertical and horizontal directions help guide the halo protons into respective absorbers which consist of an intricate design of a double wall beam tube, a water-cooled particle bed and radial shielding. Off-momentum protons, with the help of respective charge exchange foils and a dipole magnet, are directed to a momentum dump consisting of a cooled particle bed downstream of a double-walled window separating it from the vacuum space. Addressed in this paper is the thermo-mechanical response and survivability of key components of the collimating system (such as the collimating beam tube in the absorbers, the beam windows and the primary element of the bean scraper structure) in the event of intercept of the full beam under accident conditions. While the potential for the full beam to be intercepted by these components is remote, still special attention will be paid in assessing the amount of full beam (or number of pulses) they can tolerate.

This paper summarizes the design of the HBBT clean-up system consisting of a combination of charge exchange foils and absorbers. Pairs of foils moving in-and-out of the beam in both planes help guide the halo protons into respective absorbers that feature a double wall beam-tube, a water-cooled particle bed responsible and heavy radial shielding. Off-momentum protons are directed to a momentum dump via similar charge exchange foils and in combination with a dipole magnet. The paper addresses the survivability of the double beam tube in the absorber and the special window in the momentum dump that intercept halo protons over a relatively small footprint under normal operating conditions and potentially full beam under accident conditions.

A high level RF system (HLRF) consisting of power amplifiers (PA's) and ferrite loaded cavities is being designed and built by Brookhaven National Laboratory (BNL) for the Spallation Neutron Source (SNS) project. It is a fixed frequency, two harmonic system whose main function is to maintain a gap for the kicker rise time. Three cavities running at the fundamental harmonic (h=l) will provide 40 kV and one cavity at the second harmonic (h=2) will provide 20 kV. Each cavity has two gaps with a design voltage of 10 kV per gap and will be driven by a power amplifier (PA) directly adjacent to it. The PA uses a 600kW tetrode to provide the necessary drive current. The anode of the tetrode is magnetically coupled to the downstream cell of the cavity. Drive to the PA will be provided by a wide band, solid state amplifier located remotely. A dynamic tuning scheme will be implemented to help compensate for the effect of beam loading.

The accumulator ring of the Spallation Neutron Source (SNS) is designed to accept high-intensity H{sup -} beam of 1 GeV kinetic energy from the injecting LINAC, and to accumulate, in a time interval of 1 msec, 2 x 10{sup 14} protons in a single bunch of 700 nsec. In order to optimize the effective straight-section spaces for beam-injection, extraction and collimation, we have minimized the width of the large aperture quadrupoles which are located in the same straight sections of the accumulator ring with the injection and extraction systems. By minimizing the width of the quadrupoles to {+-}40.4 cm, the beam-injection and extraction angles are lowered to 8.75{sup o} and 16.8{sup o} respectively. Further optimization of the narrow quadrupole, minimizes the strength of the dodecapole multipole component of the quadrupole, thus reducing the width of the 12pole structure resonance and allowing a larger tune space for stability of the circulating beam. In this paper we present results derived from magnetic field calculations of 2D and 3D modeling, and discuss the method of optimizing the size of the quadrupole and minimizing its dodecapole multipole component.

One of the primary tasks in the design of the Spallation Neutron Source (SNS) ring is to control collective effects including space charge, transverse and longitudinal instabilities, and electron cloud. Transverse painting is used to alleviate space charge force; longitudinal painting along with chromatic sextupoles are used to enhance Landau damping; injection kicker vacuum pipes are carefully shielded, and extraction kicker impedances are measured in detail and optimized; beam halo, beam loss and electron production are minimized; finally, damping systems at various frequencies are planned. This paper summarizes these design implementations.

The integral part of the primary collimator of the SNS accumulator ring is a halo intercept assembly in the form of movable scraper blades that allow the interception of the halo protons in four planes. In order to achieve large Coulomb scattering of the halo protons and energy losses of less than 1%, platinum was chosen as the material of choice while its thickness was optimized to satisfy the energy loss requirements. This paper outlines the adopted design of the scraper assembly and presents the thermal response of the system that intercepts the beam halo as well as the subsequent thermal stress analysis and the issues associated with the performance of the scraper. Specifically, the current design incorporates a highly conducting material (copper) in the blade structure interfacing with the platinum scraper and is responsible for conducting the deposited energy away from the beam interception region. The mechanical performance and durability of such system, especially of the special bonding between the dissimilar materials, is the primary focus of this effort

Injection is key in the low-loss design of high-intensity proton facilities like the Spallation Neutron Source (SNS). During the design of both the accumulator and the rapid-cycling-synchrotron version of the SNS, extensive comparison has been made to select injection scenarios that satisfy SNS's low-loss design criteria. This paper presents issues and considerations pertaining to the final choice of the SNS injection systems

During accumulation the RF beam current in the the Spallation Neutron Source ring rises from 0 to 50 Amperes. A clean, 250 nanosecond gap is needed for the extraction kicker risetime. Large momentum spread and small peak current are needed to prevent instabilities and stopband related losses. A robust RF system meeting these requirements has been designed.