BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
After having provided collisions of polarized protons at a beam energy of 100 GeV since 2001, the Relativistic Heavy Ion Collider~(RHIC) at BNL reached its design energy of polarized proton collision at 250 GeV. With the help of the two full Siberian snakes in each ring as well as careful orbit correction and working point control, polarization was preserved during acceleration from injection to 250~GeV. During the course of the Physics data taking, the spin rotators on either side of the experiments of STAR and PHENIX were set up to provide collisions with longitudinal polarization at both experiments. Various techniques to increase luminosity like further beta star squeeze and RF system upgrades as well as gymnastics to shorten the bunch length at store were also explored during the run. This paper reports the performance of the run as well as the plan for future performance improvement in RHIC.
Tech-X, Boulder, Colorado
KEK, Ibaraki
BNL, Upton, Long Island, New York
Funding: Supported in part by the DOE Office of Science, Office of Nuclear Physics under grant No. DE-FG02-06ER84508.
Non-scaling FFAGs are sensitive to a slew of resonances during the acceleration ramp. An important consideration - because it affects the amount of rf power required - will be the speed at which resonances must be crossed. We present simulations of possible non-scaling FFAGs, focusing especially on the effects of space charge, using newly developed capabilities in the code PTC*.
* E. Forest, Y. Nogiwa, F. Schmidt, "The FPP and PTC Libraries", ICAP'2006.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In preparation for the RHIC polarized proton run 2009, simulations were carried out to evaluate the million turn dynamic apertures for different beta*s at the proposed beam energies of 100 GeV and 250 GeV. One goal of this study is to find out the best beta* for this run. We also evaluated the effects of the second order chromaticity correction. The second order chromaticties can be corrected with the MAD8 Harmon module or by correcting the horizontal and vertical half-integer resonance driving terms.
BNL, Upton, Long Island, New York
As first step in a staged approach towards a RHIC-based electron-ion collider, installation of a 4 GeV energy-recovery linac in one of the RHIC interaction regions is currently under investigation. To minimize costs, the interaction region of this collider has to utilize the present RHIC magnets for focussing of the high-energy ion beam. Meanwhile, electron low-beta focussing needs to be added in the limited space available between the existing separator dipoles. We discuss the challenges we are facing and present the current design status of this e-A interaction region.
ODU, Norfolk, Virginia
JLAB, Newport News, Virginia
Muons, Inc, Batavia
BNL, Upton, Long Island, New York
Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86351
Recirculating linear accelerators (RLA) are the most likely means to achieve the rapid acceleration of short-lived muons to multi-GeV energies required for Neutrino Factories and TeV energies required for Muon Colliders. One problem is that in the simplest schemes, a separate return arc is required for each passage of the muons through the linac. In the work described here, a novel arc optics based on a Non Scaling Fixed Field Alternating Gradient (NS-FFAG) lattice is developed, which would provide sufficient momentum acceptance to allow multiple passes (two or more consecutive energies) to be transported in one string of magnets. With these sorts of arcs and a single linac, a Recirculating Linear Accelerator (RLA) will have greater cost effectiveness and reduced losses from muon decay. We will develop the optics and technical requirements to allow the maximum number of passes by using an adjustable path length to accurately control the returned beam phase to synchronize with the RF.
BNL, Upton, Long Island, New York
CERN, Geneva
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
In the article we review the nonlinear beam dynamics from nonlinear magnetic fields in the Relativistic Heavy Ion Collider. The nonlinear magnetic fields include the magnetic field errors in the interaction regions, chromatic sextupoles, and sextupole component from arc dipoles. Their effects on the beam dynamics and long-term dynamic apertures are evaluated. The online measurement and correction methods for the IR nonlinear errors, nonlinear chromaticity, and horizontal third order resonance are reviewed. The overall strategy for the nonlinear effect correction in the RHIC is discussed.
BNL, Upton, Long Island, New York
The reduction of beta* beyond the 1m design value at RHIC has been consistently achieved over the last 6 years of RHIC operations, resulting in an increase of luminosity for different running modes and species. During the recent 2007-08 deuteron-gold run the reduction to 0.70 from the design 1 m achieved a 30% increase in delivered luminosity. The key ingredients in allowing the reduction have been the capability of efficiently developing ramps with tune and coupling feedback, orbit corrections on the ramp, and collimation at injection and on the ramp, to minimize beam losses in the final focus triplets, the main aperture limitation for the collision optics. We will describe the operational strategy used to reduce the b*, at first squeezing the beam at store, to test feasibility, followed by the operationally preferred option of squeezing the beam during acceleration, and the resulting luminosity increase obtained in the Cu-Cu run in 2005, Au-Au in 2007 and the deuteron-Au run in 2007-08. We will also include beta squeeze plans and results for the upcoming 2009 run with polarized protons at 250 GeV.
BNL, Upton, Long Island, New York
MIT, Middleton, Massachusetts
Funding: Work performed under US DOE contract DE-AC02-98CH1-886
Design of a medium energy electron-ion collider (MEeIC) is under development at Collider-Accelerator Department, BNL. The design envisions a construction of 4 GeV electron accelerator in a local area inside the RHIC tunnel. The electrons will be produced by a polarized electron source and accelerated in the energy recovery linac. Collisions of the electron beam with 100 GeV/u heavy ions or with 250 GeV polarized protons will be arranged in the existing IP2 interaction region of RHIC. The luminosity of electron-proton collisions at 1032 cm-2 s-1 level will be achieved with 40 mA CW electron current with presently available parameters of the proton beam. Efficient cooling of proton beam at the collision energy may bring the luminosity to 1033 cm-2 s-1 level. The important feature of the MEeIC is that it would serve as first stage of eRHIC, a future electron-ion collider at BNL with both higher luminosity and energy reach. The majority of the MEeIC accelerator components will be used for eRHIC.
BNL, Upton, Long Island, New York
A gas fluorescence beam profile monitor has been realized at the relativistic heavy ion collider (RHIC) using the polarized atomic hydrogen gas jet. RHIC proton beam profiles in the vertical plane are obtained as well as measurements of the width of the gas jet in the beam direction. For gold ion beams, the fluorescence cross section is sufficiently large so that profiles can be obtained from the residual gas alone, albeit with long light integration times and lower number of Au ions than protons. We estimate the fluorescence cross-section of 100 GeV protons and Au ions on hydrogen gas to be 6.6x10-21 cm2 ~1.7x10-16 cm2, respectively*. We calculate the beam emittance to provide an independent measurement of the RHIC beam. This optical beam diagnostic technique, utilizing the beam induced fluorescence from injected or residual gas, represents a step towards the realization of a simple and truly noninvasive beam monitor for high-energy particle beams together with a wall-current-monitor system and/or a low light level optical temporal measurement system, a 3-dimensional particle beam profile system can be envisioned providing routine diagnosis of high-energy particle beams.
*T. Tsang, et. al., Rev. Sci. Instrum. 79, 105103 (2008).
CERN, Geneva
BNL, Upton, Long Island, New York
The effect of magnet misalignments in the beam orbit and linear optics functions are reviewed and correction schemes are applied to the negative momentum compaction lattices of PS2. Chromaticity correction schemes are also proposed and tested with respect to off-momentum optics properties. The impact of the correction schemes in the dynamic aperture of the different lattices is finally evaluated.
CERN, Geneva
BNL, Upton, Long Island, New York
In view of the CERN Proton Synchrotron proposed replacement with a new ring (PS2), a detailed optics design as been undertaken following the evaluation of several lattice options. The basic arc module consists of cells providing negative momentum compaction. The straight section is formed with a combination of FODO and quadrupole triplet cells, to accommodate the injection and extraction systems, in particular the H- injection elements. The arc is matched to the straight section with a dispersion suppressor and matching module. Different lattices are compared with respect to their linear optics functions, tuning flexibility and geometrical acceptance properties.
Tech-X, Boulder, Colorado
KEK, Ibaraki
BNL, Upton, Long Island, New York
Funding: Supported in part by the DOE Office of Science, Office of Nuclear Physics under grant No. DE-FG02-06ER84508.
Recent simulations of non-scaling FFAGs suggest that the effects of magnet fringe fields are of signal importance. We present PTC* simulations that include realistic models for the fringes. In particular, we study how fringe extent and other parameters affect important measures of machine performance.
*E. Forest, Y. Nogiwa, F. Schmidt, "The FPP and PTC Libraries", ICAP'2006.