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R&D ERL: G5 test and commissioning plan

Description: Gun-to-5-cell cavity (G5) setup (Fig 1-2) can be considered as the first stage of the final BNL ERL design. The goal of the G5 setup is to test critical ERL components with the beam and characterize the beam produced by the gun. Also, this test will be used to assess effectiveness of the zigzag merger, which will be installed later in the ERL setup. The major components under the test will include the SRF gun, the five-cell SRF cavity, vacuum components, parts of the control and diagnostic systems. G5 is designed to measure the following beam parameters: (1) projected bunch emittance (?) and Twiss parameters ({alpha}, {beta}); (2) slice emittance; (3) bunch length; and (4) longitudinal and transverse halo.
Date: February 10, 2010
Creator: Kayran, D. & Pozdeyev, E.
Partner: UNT Libraries Government Documents Department

ION TRAPPING AND CATHODE BOMBARDMENT BY TRAPPED IONS IN DC PHOTOGUNS.

Description: DC photoguns are used to produce high-quality, high-intensity electron beams for accelerator driven applications. Ion bombardment is believed to be the major cause of degradation of the photocathode efficiency. Additionally to ions produced in the accelerating cathode-anode gap, the electron beam can ionize the residual gas in the transport line. These ions are trapped transversely within the beam and can drift back to the accelerating gap and contribute to the bombardment rate of the cathode. This paper proposes a method to reduce the flow of ions produced in the beam transport line and drifting back to the cathode-anode gap by introducing a positive potential barrier that repels the trapped ions. The reduced ion bombardment rate and increased life time of photocathodes will reduce the downtime required to service photoinjectors and associated costs.
Date: June 25, 2007
Creator: POZDEYEV,E.
Partner: UNT Libraries Government Documents Department

Cathode Ion Bombardment in RF Photoguns

Description: In this paper, we use the method of rapid oscillating field to solve the equation of ion motion in an RF gun. We apply the method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of ions produced in the gun can reach the cathode if no special precautions are taken. Also, the paper proposes a simple mitigation recipe that can reduce the rate of ion bombardment.
Date: September 1, 2008
Creator: Pozdeyev,E.; Kayran, D. & Litvinenko, V.
Partner: UNT Libraries Government Documents Department

Ion bombardment in RF photoguns

Description: A linac-ring eRHIC design requires a high-intensity CW source of polarized electrons. An SRF gun is viable option that can deliver the required beam. Numerical simulations presented elsewhere have shown that ion bombardment can occur in an RF gun, possibly limiting lifetime of a NEA GaAs cathode. In this paper, we analytically solve the equations of motion of ions in an RF gun using the ponderomotive potential of the Rf field. We apply the method to the BNL 1/2-cell SRF photogun and demonstrate that a significant portion of ions produced in the gun can reach the cathode if no special precautions are taken. Also, the paper discusses possible mitigation techniques that can reduce the rate of ion bombardment.
Date: May 4, 2009
Creator: Pozdeyev,E.; Kayran, D. & Litvinenko, V. N.
Partner: UNT Libraries Government Documents Department

Report on Design, Development, and Characterization of a Coaxial Resonator Based Single-gap Gridless Multiharmonic Buncher

Description: The design of the multiharmonic buncher is determined by Facility for Rare Isotope Beam (FRIB) requirements. The buncher will bunch stable ion beams for injection into the FRIB RFQ to minimize the longitudinal beam emittance growth. The design beam energy is fixed at 12 keV/u while the beam charge state Q/A can vary from 1/3 to 1/7. The buncher operates at a fundamental frequency of 40.25 MHz. Two higher harmonics, 80.5 MHz and 120.75 MHz are used to linearize the voltage ramp. The typical accelerating voltage for a uranium beam, including the time-of-flight factor, is 1271 V, 456 V, and 150 V for 40.25 MHz, 80.5 MHz, and 120.75 MHz harmonics respectively. The voltage will be scaled with the charge state of an accelerated beam. The accelerated electrical beam current is expected to be approximately equal to 0.5 mA for all ion beams between oxygen and uranium.
Date: February 11, 2013
Creator: Pozdeyev, E; Brandon, J; Bultman, N; Rao, X; York, R & Zhao, Q
Partner: UNT Libraries Government Documents Department

Longitudinal space charge effects near transition

Description: Experimental and numerical studies of the longitudinal beam dynamics in the Small Isochronous Ring (SIR) at Michigan State University revealed a fast, space-charge driven instability that did not fit the model of the negative mass instability. This paper proposes a simple analytical model explaining these results. Also, the paper compares the model to result s of experimental and numerical studies of the longitudinal beam dynamics in SIR.
Date: May 4, 2009
Creator: Pozdeyev,E.; Rodriguez, J.A.; Marti, F. & York, R.C.
Partner: UNT Libraries Government Documents Department

Space charge effect in isochronous rings

Description: Cyclotrons, rings for precise nuclear mass spectrometry, and some light sources with extremely short bunches are operated or planned to be operated in the isochronous or almost isochronous regime. Also, many hadron synchrotrons run in the isochronous regime for a short period of time during transition crossing. The longitudinal motion is frozen in the isochronous regime that leads to accumulation of the integral of the longitudinal space charge force. In low-gamma hadron machines, this can cause a fast growth of the beam energy spread even at modest beam intensities. Additionally, the transverse component of the space charge effectively modifies the dispersion function and the slip factor shifting the isochronous (transition) point. In this paper, we discuss space charge effects in the isochronous regime and present experimental results obtained in the Small Isochronous Ring, developed at Michigan State University specifically for studies of space charge in the isochronous regime.
Date: August 25, 2008
Creator: Pozdeyev,E.; Rodriguez, J.A.; Marti, F. & York, R.
Partner: UNT Libraries Government Documents Department

STUDY OF ELECTRON -PROTON BEAM-BEAM INTERACTION IN ERHIC

Description: Beam-beam effects present one of major factors limiting the luminosity of colliders. In the linac-ring option of eRHIC design, an electron beam accelerated in a superconducting energy recovery linac collides with a proton beam circulating in the RHIC ring. There are some features of beam-beam effects, which require careful examination in linac-ring configuration. First, the beam-beam interaction can induce specific head-tail type instability of the proton beam referred to as a ''kink'' instability. Thus, beam stability conditions should be established to avoid proton beam loss. Also, the electron beam transverse disruption by collisions has to be evaluated to ensure beam quality is good enough for the energy recovery pass. In addition, fluctuations of electron beam current and/or electron beam size, as well as transverse offset, can cause proton beam emittance growth. The tolerances for those factors should be determined and possible countermeasures should be developed to mitigate the emittance growth. In this paper, a soft Gaussian strong-strong simulation is used to study all of mentioned beam-beam interaction features and possible techniques to reduce the emittance growth.
Date: June 25, 2007
Creator: HAO,Y.; LITVINENKO, V.N.; MONTAG, C.; POZDEYEV, E. & PTITSYN, V.
Partner: UNT Libraries Government Documents Department

COLLECTIVE EFFECTS IN THE RHIC-II ELECTRON COOLER

Description: Electron cooling at RHIC-I1 upgrade imposes strict requirements on the quality of the electron beam at the cooling section. Beam current dependent effects such as the space charge, wake fields, CSR in bending magnets, trapped ions, etc., will tend to spoil the beam quality and decrease the cooling efficiency. In this paper, we estimate the defocusing effect of the space charge at the cooling section and describe our plan to compensate the defocusing space charge force by focusing solenoids. We also estimate the energy and emittance growth cased by wake fields. Finally, we discuss ion trapping in the electron cooler and consider different techniques to minimize the effect of ion trapping.
Date: June 25, 2007
Creator: POZDEYEV,E.; BEN-ZVI, I.; FEDOTOV, A.; KAYRAN, D.; LITVINENKO, V. & WANG, G.
Partner: UNT Libraries Government Documents Department

DIAGNOSTICS OF BNL ERL

Description: The ERL Prototype project is currently under development at the Brookhaven National Laboratory. The ERL is expected to demonstrate energy recovery of high-intensity beams with a current of up to a few hundred milliamps, while preserving the emittance of bunches with a charge of a few nanocoulombs produced by a high-current SRF gun. To successfully accomplish this task the machine will include beam diagnostics that will be used for accurate characterization of the three dimensional beam phase space at the injection and recirculation energies, transverse and longitudinal beam matching, orbit alignment, beam current measurement, and machine protection. This paper outlines requirements on the ERL diagnostics and describes its setup and modes of operation.
Date: June 25, 2007
Creator: POZDEYEV,E.; BEN-ZVI, I.; CAMERON, P.; GASSNER, D.; KAYRAN, D. & AL., ET
Partner: UNT Libraries Government Documents Department

eRHIC ring-ring design with head-on beam-beam compensation

Description: The luminosity of the eRHIC ring-ring design is limited by the beam-beam effect exerted on the electron beam. Recent simulation studies have shown that the beam-beam limit can be increased by means of an electron lens that compensates the beam-beam effect experienced by the electron beam. This scheme requires proper design of the electron ring, providing the correct betatron phase advance between interaction point and electron lens. We review the performance of the eRHIC ring-ring version and discuss various parameter sets, based on different cooling schemes for the proton/ion beam.
Date: May 4, 2009
Creator: Montag,C.; Blaskiewicz, M.; Pozdeyev, E.; Fischer, W. & MacKay, W. W.
Partner: UNT Libraries Government Documents Department

The Transverse Linac Optics Design in Multi-pass ERL

Description: In this paper, we analyzed the linac optics design requirement for a multi-pass energy recovery linac (ERL) for arbitrary number of linacs. A set of general formula of constrains for the 2-D transverse matrix is derived to ensure design optics acceptance matching throughout the entire accelerating and decelerating process. Meanwhile, the rest free parameters can be adjusted for fulfilling other requirements or optimization purpose. As an example, we design the linac optics for the future MeRHIC (Medium Energy eRHIC) project and show the optimization for small {beta} function.
Date: May 23, 2010
Creator: Hao, Y.; Kewisch, J.; Litvinenko,V.; Pozdeyev, E.; Ptitsyn, V.; Trbojevic, D. et al.
Partner: UNT Libraries Government Documents Department

Studies of Beam Dynamics for eRHIC

Description: We present our studies on various aspects of the beam dynamics in 'racetrack' design of the first stage electron-ion collider at RHIC (eRHIC), including transverse beam break up instabilities, energy loss due to wakefields, electron beam emittance growth and energy loss due to synchrotron radiation, electron beam losses due to Touschek effects and residue gas scattering, beam-beam effects at the interaction region and emittance growth of ion beam due to electron bunch to bunch noises. For all effects considered above, no showstopper has been found.
Date: May 23, 2010
Creator: Wang, G.; Blaskiewicz, M.; Fedotov, A.; Hao, Y.; Kewisch, J.; Litvinenko, V. et al.
Partner: UNT Libraries Government Documents Department

UNIQUE FEATURES IN MAGNET DESIGNS FOR R AND D ENERGY RECOVERY LINAC AT BNL.

Description: In this paper we describe the unique features and analysis techniques used on the magnets for a R&D Energy Recovery Linac (ERL) [1] under construction at the Collider Accelerator Department at BNL. The R&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&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&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&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&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 ...
Date: June 25, 2007
Creator: MENG,W.; JAIN, A.; GANETIS, G.; KAYRAN, D.; LITVINENKO, V.N.; LONGO, C. et al.
Partner: UNT Libraries Government Documents Department

High gain FEL amplification of charge modulation caused by a hadron

Description: In scheme of coherent electron cooling (CeC) [1,2], a modulation of electron beam density induced by a copropagation hadron is amplified in high gain FEL. The resulting amplified modulation of electron beam, its shape, form and its lethargy determine number of important properties of the coherent electron cooling. In this talk we present both analytical and numerical (using codes RON [3] and Genesis [4]) evaluations of the corresponding Green functions. We also discuss influence of electron beam parameters on the FEL response.
Date: August 24, 2008
Creator: Litvinenko,V.; Ben-Zvi, I.; Hao, Y.; Kayran, D.; Pozdeyev, E.; Wang, G. et al.
Partner: UNT Libraries Government Documents Department

Beam dynamics limits for low-energy RHIC operation

Description: There is a strong interest in low-energy RHIC operations in the single-beam total energy range of 2.5-25 GeV/nucleon [1-3]. Collisions in this energy range, much of which is below nominal RHIC injection energy, will help to answer one of the key questions in the field of QCD about the existence and location of a critical point on the QCD phase diagram [4]. There have been several short test runs during 2006-2008 RHIC operations to evaluate RHIC operational challenges at these low energies [5]. Beam lifetimes observed during the test runs were limited by machine nonlinearities. This performance limit can be improved with sufficient machine tuning. The next luminosity limitation comes from transverse and longitudinal Intra-beam Scattering (IBS), and ultimately from the space-charge limit. Here we summarize dynamic effects limiting beam lifetime and possible improvement with electron cooling.
Date: August 25, 2008
Creator: Fedotov,A.V.; Ben-Zvi, I.; Chang, X.; Kayran, D.; Litvinenko, V.N.; Pozdeyev, E. et al.
Partner: UNT Libraries Government Documents Department

Feasibility of Electron Cooling for Low-Energy RHIC Operation

Description: A concrete interest in running RHIC at low energies in a range of 2.5-25 GeV/nucleon total energy of a single beam has recently emerged. Providing collisions in this energy range, which in the RHIC case is termed 'low-energy' operation, will help to answer one of the key questions in the field of QCD about existence and location of a critical point on the QCD phase diagram. However, luminosity projections are relatively low for the lowest energy points of interest. Luminosity improvement can be provided with electron cooling applied directly in RHIC at low energies. This report summarizes the expected luminosity improvement with electron cooling, possible technical approaches and various limitations.
Date: April 1, 2008
Creator: Fedotov,A.; Ben-Zvi, I.; Chang, X.; Kayran, D.; Litvinenko, V.; Pozdeyev, E. et al.
Partner: UNT Libraries Government Documents Department

FEL POTENTIAL OF THE HIGH CURRENT ERLs AT BNL.

Description: An ampere class 20 MeV superconducting Energy Recovery Linac (ERL) is under construction at Brookhaven National Laboratory (BNL) for testing concepts for high-energy electron cooling and electron-ion colliders. This ERL prototype will be used as a test bed to study issues relevant for very high current ERLs. High average current and high performance of electron beam with some additional components make this ERL an excellent driver for high power far infrared Free Electron Laser (FEL). A possibility for future up-grade to a two-pass ERL is considered. We present the status and our plans for construction and commissioning of the ERL. We discus a FEL potential based on electron beam provided by BNL ERL.
Date: August 26, 2007
Creator: KAYRAN,D.; BEN-ZVI, I.; LITVINENKO, V.; POZDEYEV, E.; MATVEENKO, A.; SHEVCHENKO, O. et al.
Partner: UNT Libraries Government Documents Department

Lattice design for the ERL electron ion collider in RHIC

Description: We present electron ion collider lattice design for the Relativistic Heavy Ion Collider (eRHIC) where the electrons have multi-passes through recirculating linacs (ERL) and arcs placed in the existing RHIC tunnel. The present RHIC interaction regions (IR's), where the electron ion collisions will occur, are modified to allow for the large luminosity. Staging of eRHIC will bring the electron energy from 4 up to 20 (30) GeV as the superconducting cavities are built and installed sequentially. The synchrotron radiation from electrons at the IR is reduced as they arrive straight to the collision while ions and protons come with 10 mrad crossing angle using the crab cavities.
Date: May 23, 2010
Creator: Trbojevic, D.; Beebe-Wang, J.; Tsoupas, N.; Chang, X.; Kayran, D.; Ptitsyn, V. et al.
Partner: UNT Libraries Government Documents Department

Progress with FEL-based coherent electron cooling

Description: Cooling intense high-energy hadron beams remains a major challenge for accelerator physics. Synchrotron radiation is too feeble, while efficiency of two other cooling methods falls rapidly either at high bunch intensities (i.e. stochastic cooling of protons) or at high energies (i.e. e-cooling). The possibility of coherent electron cooling, based on high-gain FEL and ERL, was presented at last FEL conference [1]. This scheme promises significant increases in luminosities of modern high-energy hadron and electron-hadron colliders, such as LHC and eRHIC. In this paper we report progress made in the past year on the development of this scheme of coherent electron cooling (CeC), results of analytical and numerical evaluation of the concept as well our prediction for LHC and RHIC. We also present layout for proof-of-principle experiment at RHIC using our R&D ERL which is under construction.
Date: August 24, 2008
Creator: Litvinenko,V.; Ben-Zvi, I.; Blaskiewicz, M.; Hao, Y.; Kayran, D.; Pozdeyev, E. et al.
Partner: UNT Libraries Government Documents Department

MeRHIC - staging approach to eRHIC

Description: Design of a medium energy electron-ion collider (MeRHIC) is under development at the Collider-Accelerator Department at BNL. The design envisions construction of a 4 GeV electron accelerator in a local area inside and near the RHIC tunnel. Electrons will be produced by a polarized electron source and accelerated in energy recovery linacs. 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 the 10{sup 32} cm{sup -2}s{sup -1} level will be achieved with 50 mA CW electron current and presently available proton beam parameters. Efficient proton beam cooling at collision energy may bring the luminosity to 10{sup 33} cm{sup -2}s{sup -1}. An important feature of MeRHIC is that it serves as a first stage of eRHIC, a future electron-ion collider at BNL with both higher luminosity and energy reach. The majority of MeRHIC accelerator components will be used in eRHIC.
Date: May 4, 2009
Creator: Ptitsyn,V.; Beebe-Wang, J.; Ben-Zvi, I.; Deshpande, A.; Fedotov, A.; Hao, Y. et al.
Partner: UNT Libraries Government Documents Department

ERHIC Conceptual Design

Description: The conceptual design of the high luminosity electron-ion collider, eRHIC, is presented. The goal of eRHIC is to provide collisions of electrons (and possibly positrons) with ions and protons at the center-of-mass energy range from 25 to 140 GeV, and with luminosities exceeding 10{sup 33} cm{sup -2} s{sup -1}. A considerable part of the physics program is based on polarized electrons, protons and He3 ions with high degree of polarization. In eRHIC electron beam will be accelerated in an energy recovery linac. Major R&D items for eRHIC include the development of a high intensity polarized electron source, studies of various aspects of energy recovery technology for high power beams and the development of compact magnets for recirculating passes. In eRHIC scheme the beam-beam interaction has several specific features, which have to be thoroughly studied. In order to maximize the collider luminosity, several upgrades of the existing RHIC accelerator are required. Those upgrades may include the increase of intensity as well as transverse and longitudinal cooling of ion and proton beams.
Date: August 25, 2008
Creator: Ptitsyn,V.; Beebe-Wang,J.; Ben-Zvi,I.; Fedotov, A.; Fischer, W.; Hao, Y. et al.
Partner: UNT Libraries Government Documents Department

SUPERCONDUCTING PHOTOINJECTOR

Description: One of the frontiers in FEL science is that of high power. In order to reach power in the megawatt range, one requires a current of the order of one ampere with a reasonably good emittance. The superconducting laser-photocathode RF gun with a high quantum efficiency photocathode is the most natural candidate to provide this performance. The development of a 1/2 cell superconducting photoinjector designed to operate at up to a current of 0.5 amperes and beam energy of 2 MeV and its photocathode system are the subjects covered in this paper. The main issues are the photocathode and its insertion mechanism, the power coupling and High Order Mode damping. This technology is being developed at BNL for DOE nuclear physics applications such as electron cooling at high energy and electron ion colliders..
Date: August 26, 2007
Creator: BEN-ZVI,I.; BURRILL, A.; CALAGA, R.; CHANG, X.; GROVER, R.; GUPTA, R. et al.
Partner: UNT Libraries Government Documents Department