BNL, Upton, Long Island, New York, USA
JLab, Newport News, Virginia, USA
A high-energy, multiple-pass energy recovery (ER) experiment proposal, using CEBAF, is in preparation by a JLab-BNL collaboration. The experiment will be proposed in support of the electron-ion collider project (EIC) R&D going on at BNL. This new experiment extends the 2003, 1-pass, 1 GeV CEBAF-ER demonstration into a range of energy and recirculation passes commensurate with BNL's anticipated linac-ring EIC parameters. The experiment will study ER and recirculating beam dynamics in the presence of synchrotron radiation, provide opportunity to develop and test multiple-beam diagnostic instrumentation, and can also probe BBU limitations. This paper gives an overview of the ER@CEBAF project, its context and preparations.
BNL, Upton, Long Island, New York, USA
FZJ, Jülich, Germany
ESRF, Grenoble, France
The Relativistic Heavy Ion Collider (RHIC) has two main operating modes with heavy ions and polarized protons respectively. In addition to a continuous increase in the bunch intensity in all modes, two major new systems were completed recently mitigating the main luminosity limit and leading to significant performance improvements. For heavy ion operation stochastic cooling mitigates the effects of intrabeam scattering, and for polarized proton operation head-on beam-beam compensation mitigated the beam-beam effect. We present the performance increases with these upgrades for heavy ions and polarized protons, as well as an overview of all operating modes past and planned.
BNL, Upton, Long Island, New York, USA
SUNY SB, Stony Brook, New York, USA
SBU, Stony Brook, New York, USA
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
HOM damping is a challenge for high-current SRF linacs possibly generating HOM power at a level of 10 KW per cavity. A rectangular waveguide used as a natural high pass filter is a good option as high power, large spectrum HOM damper. However, its size is too big, causing a big challenge for the cooling and cryogenic system. A reliable, compact HOM damping scheme using a ridged waveguide is being developed to damp high power (> 10 kW), large spectrum HOMs ( up to 40 GHz) that may be generated in the 647 MHz 5-cell eRHIC ERL SRF linac. The size of a ridged waveguide is less than a quarter of the regular waveguide, which alleviates the thermal issue. This paper presents the design of a ridged waveguide and estimated HOM damping results using a ridged waveguide. The thermal or cooling design of the ridged waveguide will also be addressed.
BNL, Upton, Long Island, New York, USA
To avoid the luminosity loss due to cross-angle collision, crab cavities are being considered for the electron-ion collider designs at Brookhaven National Laboratory. In this article, we study the effects of crab cavities on the proton beam dynamics without and with beam-beam interactions. Dynamic apertures are to be calculated with various parameters of crab cavities. To minimize the distortion from a single crab cavity, harmonic crab cavities are also considered.
BNL, Upton, Long Island, New York, USA
Fermilab, Batavia, Illinois, USA
Recent developments of the ERL-based design of future high luminosity electron-hadron collider eRHIC focused on balancing technological risks present in the design versus the design cost. As a result a lower risk design has been adopted at moderate cost increase. The modifications include a change of the main linac RF frequency, reduced number of SRF cavity types and modified electron spin transport using a spin rotator. A luminosity-staged approach is being explored with a Nominal design (L ~ 1033 cm-2 s-1) that employs reduced electron current and could possibly be based on classical electron cooling, and then with the Ultimate design (L > 1034 cm-2 s-1) that uses higher electron current and an innovative cooling technique (CeC). The paper describes the recent design modifications, and presents the full status of the eRHIC ERL-based design.
BNL, Upton, Long Island, New York, USA
High current Superconducting Radiofrequency (SRF) 5-cell cavities are essential for the proposed ERL-based electron-ion collider eRHIC in BNL. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the ERL create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in the eRHIC 5-cell cavity with different ERL bunch patterns using both methods. We also discuss possible solutions to reduce this HOM power.
BNL, Upton, Long Island, New York, USA
SUNY SB, Stony Brook, New York, USA
eRHIC project is a future electron-hadron collider proposed at BNL. The proposed electron accelerator will generate up to 20 GeV polarized electrons which will collide with proton beams with energy up to 250 GeV. The proposed collider will deliver electron-nucleon luminosity of 1033- 1034 cm-2 ses−1. A superconducting RF (SRF) 5-cell elliptical cavity will be utilized in electron accelerator. This paper presents a study of higher-order modes (HOM) for this 647 MHz SRF cavity. Different types of HOM modes and their BBU instabilities were investigated for frequencies up to 3.2 GHz. Threshold current values of beam breakup are estimated by GBBU code. Further improvement on this threshold current has been explored and discussed.
BNL, Upton, Long Island, New York, USA
Crab crossing is an essential concept in the newly proposed colliders or the upgrades. It enables crossing angles to achieve lower β* without a loss of luminosity. The frequency of the crab cavity shall be chosen with various considerations, including the luminosity degradation, emittance growth due to synchro-beta resonances and RF noises. We use the figure of merits and related simulation to establish the frequency scaling relations with important beam parameters, which guide the choice of crab cavity frequency for new designs.
BNL, Upton, Long Island, New York, USA
The ERL-ring eRHIC adopts the electron accelerator design of a multi-pass energy recovery linac (ERL), with fixed field alternating gradient (FFAG) recirculating passes. To ensure the beam quality in the accelerating and decelerating stage and the energy recovery efficiency, detailed start-to-end simulation is required to evaluate the various beam dynamics effects, such as synchrotron radiation, wake fields, coherent synchrotron radiation. In this paper, we present the eRHIC ERL start-to-end simulation strategy with various simulation codes and the current status.
BNL, Upton, Long Island, New York, USA
To reduce the technical risk of the future electron-ion collider eRHIC currently under study at BNL, the ring-ring scheme has been revisited over the summer of 2015. The goal of this study was a design that covers the full center-of-mass energy range from 32 to 141 GeV with an initial luminosity around 1033 cm-2 sec-1, upgradeable to 1034 cm-2 sec-1 later on. In this presentation the baseline design will be presented, and future upgrades will be discussed.
BNL, Upton, Long Island, New York, USA
High electron beam polarization (70-80%) is required in the future electron-ion collider eRHIC over the whole electron beam energy range from 5 GeV to 20 GeV. This paper analyzes important aspects for achieving a high electron polarization level in the ring-ring design option of eRHIC and presents the design of spin rotators required to generate the longitudinal polarization orientation at the interaction point. Experiment considerations require bunch spin patterns with both spins up and down. A highly polarized beam will be produced by a photo-injector, accelerated to full collision energy by an injector accelerator and injected into the storage ring. Beam depolarization time in the storage ring has to be minimized in the presence of spin rotators, detector solenoid and damping wiggler, which establishes specific requirements for the ring lattice.