The BNL EBIS Program: Status and plans

Recently an Electron Beam Ion Source (EBIS), on long term loan from Sandia National Laboratories, has been put into operation at Brookhaven National Laboratory. This source is being primarily used as a test device to answer questions relevant to the eventual design of an EBIS-based heavy ion preinjector for RHIC; a secondary objective is to determine parameters of an EBIS capable of delivering fully stripped light ions up to neon for medical applications. Such a source can easily produce all ions in charge states as needed, but the challenge lies in reaching intensities of interest to RHIC (2--3 {times} 10{sup 9} particles/pulse). The source studies are planned to address issues such as scaling of the electron beam current in stages up to 10 A, possible onset and control of instabilities, external ion injection, parametric studies of the ion yield, charge state distributions and emittance of the extracted ion beam, ion cooling in the trap, and other technical and physics issues

Measurement of the analyzing power in pp elastic scattering in the peak CNI region at RHIC

We report the first measurements of the A_N absolute value and shape in the -t range from 0.0015 to 0.010GeV/c^2 with a precision better than 0.005 for each A_N data point using a polarized atomic hydrogen gas jet target and the 100 GeV RHIC proton beam.Comment: 4 pages, 5 figure

Simulation of 10 A Electron Beam Formation and Collection for a High Current EBIS

Development of an Electron Beam Ion Source (EBIS) for the Relativistic Heavy Ion Collider (RHIC) at BNL requires operating with a 10 A electron beam, which is approximately an order of magnitude higher current than in any existing EBIS device. A test stand is presently being designed and constructed where EBIS components will be twisted. It will be reported in a separate paper at this Conference. The design of the 10 A electron gun, drift tubes and electron collector requires extensive computer simulations. Calculations have been performed at Novosibirsk and BNL using two different programs, SAM and EGUN. Results of these simulations will be presented

Ionization of polarized 3He+ ions in EBIS trap with slanted electrostatic mirror.

Methods of producing the nuclear polarized {sup 3}He{sup +} ions and their ionization to {sup 3}H{sup ++} in ion trap of the electron Beam Ion Source (EBIS) are discussed. Computer simulations show that injection and accumulation of {sup 3}He{sup +} ions in the EBIS trap with slanted electrostatic mirror can be very effective for injection times longer than the ion traversal time through the trap

Model Simulations of Continuous ION Interjection Into EBIS Trap with Slanted Electrostatic Mirror

The efficiency of trapping ions in an EBIS is of primary importance for many applications requiring operations with externally produced ions: RIA breeders, ion sources, traps. At the present time, the most popular method of ion injection is pulsed injection, when short bunches of ions get trapped in a longitudinal trap while traversing the trap region. Continuous trapping is a challenge for EBIS devices because mechanisms which reduce the longitudinal ion energy per charge in a trap (cooling with residual gas, energy exchange with other ions, ionization) are not very effective, and accumulation of ions is slow. A possible approach to increase trapping efficiency is to slant the mirror at the end of the trap which is opposite to the injection end. A slanted mirror will convert longitudinal motion of ions into transverse motion, and, by reducing their longitudinal velocity, prevent these ions from escaping the trap on their way out. The trade off for the increased trapping efficiency this way is an increase in the initial transverse energy of the accumulated ions. The slanted mirror can be realized if the ends of two adjacent electrodes- drift tubes - which act as an electrostatic mirror, are machined to produce a slanted gap, rather than an upright one. Applying different voltages to these electrodes will produce a slanted mirror. The results are presented of 2D and 3D computer simulations of ion injection into a simplified model of EBIS with slanted mirror

High Performance Ebis for Rhic.

An Electron Beam Ion Source (EBIS), capable of producing high charge states and high beam currents of any heavy ion species in short pulses, is ideally suited for injection into a synchrotron. An EBIS-based, high current, heavy ion preinjector is now being built at Brookhaven to provide increased capabilities for the Relativistic Heavy Ion Collider (RHIC), and the NASA Space Radiation Laboratory (NSRL). Benefits of the new preinjector include the ability to produce ions of any species, fast switching between species to serve the simultaneous needs of multiple programs, and lower operating and maintenance costs. A state-of-the-art EBIS, operating with an electron beam current of up to 10 A, and producing multi-milliamperes of high charge state heavy ions, has been developed at Brookhaven, and has been operating very successfully on a test bench for several years. The present performance of this high-current EBIS is presented, along with details of the design of the scaled-up EBIS for RHIC, and the status of its construction. Other aspects of the project, including design and construction of the heavy ion RFQ, Linac, and matching beamlines, are also mentioned

Ion Optics of RHIC EBIS

RHIC EBIS has been commissioned to operate as a versatile ion source on RHIC injection facility supplying ion species from He to Au for Booster. Except for light gaseous elements RHIC EBIS employs ion injection from several external primary ion sources. With electrostatic optics fast switching from one ion species to another can be done on a pulse to pulse mode. The design of an ion optical structure and the results of simulations for different ion species are presented. In the choice of optical elements special attention was paid to spherical aberrations for high-current space charge dominated ion beams. The combination of a gridded lens and a magnet lens in LEBT provides flexibility of optical control for a wide range of ion species to satisfy acceptance parameters of RFQ. The results of ion transmission measurements are presented

Design and Performance of the Matching Beamline Between the Bnl Ebis and an Rfq.

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

Absolute polarimetry at RHIC

Precise and absolute beam polarization measurements are critical for the RHIC spin physics program. Because all experimental spin-dependent results are normalized by beam polarization, the normalization uncertainty contributes directly to final physics uncertainties. We aimed to perform the beam polarization measurement to an accuracy of $\Delta P_{beam}/P_{beam} < 5$. The absolute polarimeter consists of Polarized Atomic Hydrogen Gas Jet Target and left-right pairs of silicon strip detectors and was installed in the RHIC-ring in 2004. This system features \textit{proton-proton} elastic scattering in the Coulomb nuclear interference (CNI) region. Precise measurements of the analyzing power $A_N$ of this process has allowed us to achieve $\Delta P_{beam}/P_{beam} =4.2$ in 2005 for the first long spin-physics run. In this report, we describe the entire set up and performance of the system. The procedure of beam polarization measurement and analysis results from 2004-2005 are described. Physics topics of $A_N$ in the CNI region (four-momentum transfer squared $0.001 < -t < 0.032 ~ ({\rm GeV}/c)^2$) are also discussed. We point out the current issues and expected optimum accuracy in 2006 and the future.Comment: 10 pages, PSTP07 proceedings contributio

A high-performance electron beam ion source

At Brookhaven National Laboratory, a high current Electron Beam Ion Source (EBIS) has been developed as part of a new preinjector that is under construction to replace the Tandem Van de Graaffs as the heavy ion preinjector for the RHIC and NASA experimental programs. This preinjector will produce milliampere-level currents of essentially any ion species, with q/A {ge} 1/6, in short pulses, for injection into the Booster synchrotron. In order to produce the required intensities, this EBIS uses a 10A electron gun, and an electron collector designed to handle 300 kW of pulsed electron beam power. The EBIS trap region is 1.5 m long, inside a 5T, 2m long, 8-inch bore superconducting solenoid. The source is designed to switch ion species on a pulse-to-pulse basis, at a 5 Hz repetition rate. Singly-charged ions of the appropriate species, produced external to the EBIS, are injected into the trap and confined until the desired charge state is reached via stepwise ionization by the electron beam. Ions are then extracted and matched into an RFQ, followed by a short IH Linac, for acceleration to 2 MeV/A, prior to injection into the Booster synchrotron. An overview of the preinjector is presented, along with experimental results from the prototype EBIS, where all essential requirements have already been demonstrated. Design features and status of construction of the final high intensity EBIS is also be presented