BNL, Upton, Long Island, New York, USA
Coherent Electron Cooling (CeC) requires detailed con- trol of the phase between the hadron an the FEL-amplified wave packet. This phase depends on local electron beam parameters such as the energy spread and the peak current. In this paper, we examine the effects of local density variations on the cooling rates for CeC.
Tech-X, Boulder, Colorado, USA
BNL, Upton, Long Island, New York, USA
Next generation ion colliders will require effective cooling of high-energy hadron beams. Coherent electron cooling (CEC) can in principle cool relativistic hadron beams on orders-of-magnitude shorter time scales than other techniques. We present Vlasov-Poisson and delta-f particle-in-cell (PIC) simulations of a CEC modulator section. These simulations correctly capture the subtle time and space evolution of the density and velocity wake imprinted on the electron distribution via anisotropic Debye shielding of a drifting ion. We consider 1D and 2D reduced versions of the problem, and compare the exact solutions of Wang and Blaskiewicz with Vlasov-Poisson and delta-f PIC simulations. We also consider interactions under non-ideal conditions where there is a density gradient in the electron distribution, and present simulations of the ion wake.
* V.N. Litvinenko and Y.S. Derbenev, Phys. Rev. Lett. 102, 114801 (2009).
Tech-X, Boulder, Colorado, USA
BNL, Upton, Long Island, New York, USA
PSI, Villigen, Switzerland
Increasing the luminosity of ion beams in particle accelerators is critical for the advancement of nuclear and particle physics. Coherent electron cooling promises to cool high-energy hadron beams significantly faster than electron cooling or stochastic cooling. Here we show simulations of a single pass through a coherent electron cooler, which consists of a modulator, a free-electron laser, and a kicker. In the modulator the electron beam copropagates with the ion beam, which perturbs the electron beam density according to the ion positions. The FEL, which both amplifies and imparts wavelength-scale modulation on the electron beam. The strength of modulated electric fields determines how much they accelerate or decelerate the ions when electron beam recombines with the dispersion-shifted hadrons in the kicker region. From these field strengths we estimate the cooling time for a gold ion with a specific longitudinal velocity.
* Vladimir N. Litvinenko, Yaroslav S. Derbenev, Physical Review Letters 102, 114801 (2009)
BNL, Upton, Long Island, New York, USA
We present a lattice design of a CW Electron Recovery Linacs (ERL) for future electron-hadron colliders eRHIC and LHeC. In eRHIC, an six-pass ERL installed in the existing Relativistic Heavy Ion Collider (RHIC) tunnel will collide 5-30 GeV polarized electrons with RHIC’s 50-250 (325) GeV polarized protons or 20-100 (130) GeV/u heavy ions. In LHeC, a stand-along 3-pass 60 GeV CW ERL will collide polarized electrons with 7 TeV protons. After collision, electron beam energy is recovered and electrons are dumped at low energy. Two superconducting linacs are located in the two straight sections in both ERLs. . The multiple arcs are made of Flexible Momentum Compaction lattice (FMC) allowing adjustable momentum compaction for electrons with different energies. The multiple arcs, placed above each other, are matched to the two linacs straight sections with splitters and combiners.
BNL, Upton, Long Island, New York, USA
Kink instability presents one of the limiting factors from achieving higher luminosity in ERL based electron ion collider (EIC). However, we can take advantage of the flexibility of the linac and design a feedback system to cure the instability. This scheme raises the threshold of kink instability dramatically and provides for higher luminosity. We studied the effectiveness of this system and its dependence on the amplitude and phase of the feedback. In this paper we present results of theses studies of this scheme and describe its theoretical and practical limitations.
BNL, Upton, Long Island, New York, USA
There is a need for an Optics-Free FEL Oscillators (OFFELO) to further the advantages of free-electron lasers and turning them in fully coherent light sources. While SASE (Self-Amplified Spontaneous Emission) FELs demonstrated the capability of providing very high gain and short pulses of radiation and scalability to the Xray range, the spectra of SASE FELs remains rather wide (~0.5%-1%) compared with typical short wavelengths FEL-oscillators (0.01% - 0.0003% in OK-4 FEL). Absence of good optics in VUV and X-ray ranges makes traditional oscillator schemes with very high average and peak spectral brightness either very complex or, strictly speaking, impossible. In this paper, we discuss lattice of the X-ray optics-free FEL oscillator and present results of initial computer simulations of the feedback process and the evolution of FEL spectrum in X-ray OFFELO. We also discuss main limiting factors and feasibility of X-ray OFFELO.
BNL, Upton, Long Island, New York, USA
PKU/IHIP, Beijing, People's Republic of China
Stony Brook University, Stony Brook, USA
BNL, Upton, Long Island, New York, USA
The ion trapping effect is an important effect in energy recovery linac (ERL). The ionized residue gas molecules can accumulate at the vicinity of the electron beam pass and deteriorate the quality of the electron beam. In this paper, we present simulation results to address this issue in eRHIC and find best beam pattern to eliminate this effect.
BNL, Upton, Long Island, New York, USA
PKU/IHIP, Beijing, People's Republic of China
Stony Brook University, Stony Brook, USA
The future electron-ion collider eRHIC requires a high average current (~50 mA), short bunch (~3 mm), low emittance (~20 μm) polarized electron source. The maximum average current of a polarized electron source so far is more than 1 mA, but much less than 50 mA, from a GaAs:Cs cathode [1]. One possible approach to overcome the average current limit and to achieve the required 50 mA beam for eRHIC, is to combine beamlets from multiple cathodes to one beam. In this paper, we present the feasibility studies of this technique.
BNL, Upton, Long Island, New York, USA
Tech-X, Boulder, Colorado, USA
JLAB, Newport News, Virginia, USA
Coherent electron cooling (CEC) has a potential to significantly boost luminosity of high-energy, high-intensity hadron-hadron and electron-hadron colliders*. In a CEC system, a hadron beam interacts with a cooling electron beam. A perturbation of the electron density caused by ions is amplified and fed back to the ions to reduce the energy spread and the emittance of the ion beam. To demonstrate the feasibility of CEC we propose a proof-of-principle experiment at RHIC using one of JLab’s SRF cryo-modules. In this paper, we describe the experimental setup for CeC installed into one of RHIC's interaction regions. We present results of analytical estimates and results of initial simulations of cooling a gold-ion beam at 40 GeV/u energy via CeC.
* Vladimir N. Litvinenko, Yaroslav S. Derbenev, Physical Review Letters 102, 114801
BNL, Upton, Long Island, New York, USA
* V.N. Litvinenko, I. Ben-Zvi, Proceedings of FEL'2004, http://jacow.org/f04/papers/WEBOS04/
BNL, Upton, Long Island, New York, USA
We are presenting the layout and the optics of a beam line to be used as a medical gantry in radiation therapy. The optical properties of the gantry’s beam line are such as to make the beam line achromatic and uncoupled. These two properties make the beam spot size, which is delivered and focused by the gantry, on the tumor of the patient, independent of the angular orientation of the gantry. In this paper we present the layout of the magnetic elements of the gantry, and also present the theoretical basis for the optics design of such a gantry.
* N. Tsoupas et. al. “Uncoupled achromatic tilted S-bend” Presented at the 11th Biennial European Particle Accelerator Conference, Genoa, Italy, June 23-27,2008
BNL, Upton, Long Island, New York, USA
We show that the paraxial field equation for a free electron laser (FEL) in an infinitely wide electron beam with a kappa-2 energy distribution can be reduced to a fourth ordinary differential equation (ODE). Its solution for arbitrary initial phase space density modulation has been derived in the wave-vector domain. For initial current modulation with Gaussian profile, close form solutions are obtained in space-time domain.
BNL, Upton, Long Island, New York, USA
FRIB, East Lansing, Michigan, USA
MIT, Middleton, Massachusetts, USA
We present the design of 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 1034 cm-2 s-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&D such as the high-current polarized electron source, the coherent electron cooling and the compact magnets for recirculating passes. A natural staging scenario of step-by-step increases of the electron beam energy by builiding-up of eRHIC's SRF linacs and a potential of adding polarized positrons are also presented.
BNL, Upton, Long Island, New York, USA
JLAB, Newport News, Virginia, USA
AES, Medford, NY, USA
The Brookhaven National Laboratory (BNL) 5-cell, 703 MHz superconducting RF accelerating cavity has been installed in the high-current energy recovery linac (ERL) experiment. This experiment will function as a proving ground for the development of high-current machines in general and is particularly targeted at beam development for an electron-ion collider (eRHIC). The cavity performed well in vertical tests, demonstrating gradients of 20 MV/m and a Q0 of 1010. Here we will present its performance in the horizontal tests, and discuss technical issues involved in its implementation in the ERL.
BNL, Upton, Long Island, New York, USA
BNL, Upton, Long Island, New York, USA
As part of the search for a phase transition or critical point on the QCD phase diagram, an energy scan including 5 different energy settings was performed during the 2010 RHIC heavy ion run. While the top beam energy for heavy ions is at 100 GeV/n and the lowest achieved energy setpoint was significantly below RHICs injection energy of approximately 10 GeV/n, we also provided beams for data taking in a medium energy range above injection energy and below top beam energy. This paper reviews RHIC experience and challenges for RHIC medium energy operations that produced full experimental data sets at beam energies of 31.2 GeV/n and 19.5 GeV/n.
BNL, Upton, Long Island, New York, USA
Stony Brook University, Stony Brook, USA
USC, Los Angeles, California, USA