The RHIC injection kicker

Beam transfer from the AGS to RHIC is performed in single-bunch mode. Close spacing of the bunches in the collider requires an injection kicker with a rise time of <90 nsec, suggesting adoption of a travelling wave structure. The required vertical kick of 0.186 t{center_dot}m is provided by 4 magnets, each 1.12 m long with a 48.4 x 48.4 mm aperture and operated at 1.6 kA. The kicker is constructed as a {open_quotes}C{close_quotes} cross section magnet, in which ferrite and high-permittivity dielectric sections alternate. The dielectric blocks provide the capacity necessary for the nominally 25 {Omega} characteristic impedance of the travelling wave structure, but impose the practical limit on the peak voltage, and thus current, achievable. Computer studies to minimize local electric field enhancements resulted in a configuration capable of holding {approximately} 50 kV, with adequate safety margin over the nominal 40 kV. Equivalent circuit analysis indicated the possibility of lowering the nominal voltage by operating mismatched into 20 {Omega} terminations without degrading the pulse shape. In this paper, the experience gained in the fabrication of the production units and the results from various single-unit tests and operation of four kickers with beam in the {open_quotes}Sextant Test{close_quotes} are reported

The Beam_Optics at the Extraction Region of SNS Ring: Revisited

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Unique Features in Magnet Designs for R and D Energy Recovery Linac at BNL.

In this paper we describe the unique features and analysis techniques used on the magnets for a R&amp;D Energy Recovery Linac (ERL) [1] under construction at the Collider Accelerator Department at BNL. The R&amp;D ERL serves as a test-bed for future BNL ERLs, such as an electron-cooler-ERL at RHIC [2] and a future 20 GeV ERL electron-hadron at eRHIC [3]. Here we present select designs of various dipole and quadruple magnets which are used in Z-bend merging systems [4] and the returning loop, 3-D simulations of the fields in aforementioned magnets, particle tracking analysis, and the magnet's influence on beam parameters. We discuss an unconventional method of setting requirements on the quality of magnetic field and transferring them into measurable parameters as well as into manufacturing tolerances. We compare selected simulation with results of magnetic measurements. A 20 MeV R&amp;D ERL (Fig. 1) is in an advanced phase of construction at the Collider-Accelerator Department at BNL, with commissioning planned for early 2009. In the R&amp;D ERL, an electron beam is generated in a 2 MeV superconducting RF photo-gun, next is accelerated to 20 MeV in a 5 cell SRF linac, subsequently passed through a return loop, then decelerated to 2 MeV in the SRF linac, and finally is sent to a beam dump. The lattice of the R&amp;D ERL is designed with a large degree of flexibility to enable the covering of a vast operational parameter space: from non-achromatic lattices to achromatic with positive, zero and negative R56 parameter. It also allows for large range tunability of Rlz and lattice RS4 parameters (which are important for transverse beam-break-up instability). Further details of the R&amp;D ERL can be found elsewhere in these proceedings [5]. The return loop magnets are of traditional design with the following exceptions: (a) The bending radius of the 60{sup o} dipole magnets is 20 cm, which is rather small. We use 15{sup o} edges on both sides of the dipoles to split very strong focusing evenly between the horizontal and vertical planes (so-called chevron-magnet). (b) The requirements on field quality of the loop's quadrupoles had been determined by the requirement to preserve a very low normalized transverse slice emittance of electron beam ({var_epsilon} {approx} 1 mm-mrad). We used direct tracking of a sample electron beam to verify a high degree of the emittance preservation. (c) Each quadrupole is equipped with a dipole trim coil, which can be also used to excite a sextupole component, if required, for emittance preservation of e-beam with a large energy spread. One of the unique features of all ERLs is the necessity for merging low and high energy electron beams. In the R&amp;D ERL, 2 MeV from the SRF gun merges with the 20 MeV electron beam coming around the return loop into the same trajectory at a position within the SRF linac. In the linac, injected bunch is accelerated to 20 MeV, while the returned or ''used'' bunch is decelerated to 2 MeV. The challenge for a merger design is to provide conditions for emittance compensation [5] and also for achromatic conditions of a low energy, space-charge dominated-e-beam [4,6]. The scheme which satisfies these requirements (called 2-bend [4]) is used on the R&amp;D ERL. The Z-bend is approximately 4-meter long. It bends the beam trajectory in the vertical plane. It is comprised of four dipole magnets designed to be equally focusing in both planes, with bending radius {approx} 60 cm, and bending angles of: +15{sup o}, -30{sup o}, +30{sup o} and -15{sup o}. The beam dynamics in the Z-bend results in a large-size (centimeters) near-laminar electron beam [7]. The large beam size and very low slice emittance of the e-beam dictates the tolerances on the magnetic field to be very tight. The integrated nonlinear kicks should not exceed {approx} 20 micro-radian per magnet at a typical radius {approx} 1 cm. The magnets in the Z-bend are rather short (15 cm effective length for the 15{sup o} magnet) and have a rather large aperture of 6 cm. Analysis predicts that the influence of various field components on the emittance growth are complicated by the fact that the beam trajectory bends significantly in the Einge fields. Hence, we decided to use direct tracking in the calculated fields extracted from Opera3d of test beam to evaluate and to minimize influence of magnetic field on the beam emittance. In addition, we used predictions of Opera3d and compared them with results of magnetic measurements for the return loop dipole and quadrupole. One of the features of the loop magnets is that they are fabricated with a very high geometric tolerance, allowing them to be an excellent test bed for bench-marking our predictions. Agreement with the prediction provides us with sufficient confidence that Z-bend magnets will preserve beam emittance

Design of a High-bunch-charge 112-MHz Superconducting RF Photoemission Electron Source

High-bunch-charge photoemission electron-sources operating in a continuous wave (CW) mode are required for many advanced applications of particle accelerators, such as electron coolers for hadron beams, electron-ion colliders, and free-electron lasers (FELs). Superconducting RF (SRF) has several advantages over other electron-gun technologies in CW mode as it offers higher acceleration rate and potentially can generate higher bunch charges and average beam currents. A 112 MHz SRF electron photoinjector (gun) was developed at Brookhaven National Laboratory (BNL) to produce high-brightness and high-bunch-charge bunches for the Coherent electron Cooling Proof-of-Principle (CeC PoP) experiment. The gun utilizes a quarter-wave resonator (QWR) geometry for assuring beam dynamics, and uses high quantum efficiency (QE) multi-alkali photocathodes for generating electrons

High luminosity electron-hadron collider eRHIC

We present the design of a future high-energy high-luminosity electron-hadron collider at RHIC called eRHIC. We plan on adding 20 (potentially 30) GeV energy recovery linacs to accelerate and to collide polarized and unpolarized electrons with hadrons in RHIC. The center-of-mass energy of eRHIC will range from 30 to 200 GeV. The luminosity exceeding 10{sup 34} cm{sup -2} s{sup -1} can be achieved in eRHIC using the low-beta interaction region with a 10 mrad crab crossing. We report on the progress of important eRHIC R&amp;D such as the high-current polarized electron source, the coherent electron cooling, ERL test facility and the compact magnets for recirculation passes. A natural staging scenario of step-by-step increases of the electron beam energy by building-up of eRHIC's SRF linacs is presented

Gluons and the quark sea at high energies:distributions, polarization, tomography

This report is based on a ten-week program on "Gluons and the quark sea at high-energies", which took place at the Institute for Nuclear Theory in Seattle in Fall 2010. The principal aim of the program was to develop and sharpen the science case for an Electron-Ion Collider (EIC), a facility that will be able to collide electrons and positrons with polarized protons and with light to heavy nuclei at high energies, offering unprecedented possibilities for in-depth studies of quantum chromodynamics. This report is organized around four major themes: i) the spin and flavor structure of the proton, ii) three-dimensional structure of nucleons and nuclei in momentum and configuration space, iii) QCD matter in nuclei, and iv) Electroweak physics and the search for physics beyond the Standard Model. Beginning with an executive summary, the report contains tables of key measurements, chapter overviews for each of the major scientific themes, and detailed individual contributions on various aspects of the scientific opportunities presented by an EIC