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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

R&D ERL: Beam dynamics, parameters, and physics to be learned

Description: The R&D ERL facility at BNL aims to demonstrate CW operation of ERL with average beam current in the range of 0.1-1 ampere, combined with very high efficiency of energy recovery. The ERL is being installed in one of the spacious bays in Bldg. 912 of the RHIC/AGS complex (Fig. 1). The bay is equipped with an overhead crane. The facility has a control room, two service rooms and a shielded ERL cave. The control room is located outside of the bay in a separate building. The single story house is used for a high voltage power supply for 1 MW klystron. The two-story unit houses a laser room, the CW 1 MW klystron with its accessories, most of the power supplies and electronics. The ERL R&D program has been started by the Collider Accelerator Department (C-AD) at BNL as an important stepping-stone for 10-fold increase of the luminosity of the Relativistic Heavy Ion Collider (RHIC) using relativistic electron cooling of gold ion beams with energy of 100 GeV per nucleon. Furthermore, the ERL R&D program extends toward a possibility of using 10-20 GeV ERL for future electron-hadron/heavy ion collider, MeRHIC/eRHIC. These projects are the driving force behind the development of ampere-class ERL technology, which will find many applications including light sources and FELs. The intensive R&D program geared towards the construction of the prototype ERL is under way: from development of high efficiency photo-cathodes to the development of new merging system compatible with emittance compensation.
Date: February 1, 2010
Creator: Kayran, D.
Partner: UNT Libraries Government Documents Department

MERGER SYSTEM OPTIMIZATION IN BNL HIGH CURRENT R&D ERL

Description: A super-conducting RF R&D Energy recovery linac (ERL) is under construction at Brookhaven National Laboratory (BNL). This ERL will be used as a test facility to study issues relevant to high-current, high-brightness beams. One of the goals is to demonstrate an electron beam with high charge per bunch ({approx}5 nC) and extremely low normalized emittance ({approx}5 mm-mrad) at an energy of 20 MeV. In contrast with operational high-brightness linear electron accelerators, all presently operating ERLs have order of magnitude larger emittances for the same charge per bunch. One reason for this emittance growth is that the merger system mixes transverse and longitudinal degrees of freedom, and consequently violates emittance compensation conditions. A merger system based on zigzag scheme resolves this problem. In this paper we discuss performance of the present design of the BNL R&D ERL injector with a zigzag merger.
Date: June 25, 2007
Creator: KAYRAN,D. & LITVINENKO, V.
Partner: UNT Libraries Government Documents Department

OPTICS OF A TWO-PASS ERL AS AN ELECTRON SOURCE FOR A NON-MAGNETIZED RHIC-II ELECTRON COOLER.

Description: Non-magnetized electron cooling of RHIC requires an electron beam energy of 54.3 MeV, electron charge per bunch of 5 nC, normalized rms beam emittance of 4 mm-mrad, and rms energy spread of 4e-04 [I]. In this paper we describe a lattice of a two-pass SRF energy recovery linac (ERL) and results of a PARMELA simulation that provides electron beam parameters satisfying RHIC electron cooling requirements.
Date: June 25, 2007
Creator: KAYRAN,D.
Partner: UNT Libraries Government Documents Department

Wake fields and energy spread for the eRHIC ERL

Description: Wake fields in high-current ERLs can cause significant beam quality degradations. Here we summarize effects of coherent synchrotron radiation, resistive wall, accelerating cavities and wall roughness for ERL parameters of the eRHIC project. A possibility of compensation of such correlated energy spread is also presented. An emphasis in the discussion is made on the suppression of coherent synchrotron radiation due to shielding and a possible reduction of wall roughness effects for realistic surfaces. In this report we discuss the wake fields with a focus on their effect on the energy spread of the beam. Other effects of wake fields are addressed elsewhere. An energy spread builds up during a pass though a very long beam transport in the eRHIC ERL under design. Such energy spread become important when beam is decelerated to low energy, and needs to be corrected. Several effects, such as Coherent Synchrotron Radiation (CSR), Resistive Wall (RW), accelerating RF cavities (RF) and Wall Roughness (WR) were considered. In this paper, we briefly summarize major contributions to energy spread from the wake fields for eRHIC parameters, and present possible energy spread compensation for decelerated beam. In the rest of the report we discuss effects which we believe are suppressed for the eRHIC parameters.
Date: October 16, 2011
Creator: Fedotov, A. & Kayran, D.
Partner: UNT Libraries Government Documents Department

Calibration of the ERL cavity FPC and PU couplers

Description: The performance parameters of a superconducting cavity, notably accelerating field and quality factor, are first obtained in a cryogenic vertical test Dewar, and again after the final assembly in its cryostat. The tests involve Network Analyzer (NA) measurements in which the cavity is excited through an input coupler and the properties are obtained from the reflected signal at the input and the transmitted signal from the output coupler. The interpretation of the scattering coefficients in terms of field strength requires the knowledge of the Fundamental Power Coupler (FPC) and Pick-Up (PU) coupler strength, as expressed by their 'external' and Q{sub FPC} Q{sub PU}. The coupler strength is independent of the field level or cavity losses and thus can be determined at low levels with the scattering coefficients S{sub 11} and S{sub 21}, assuming standard 50 {Omega} terminations in the network analyzer. Also needed is the intrinsic cavity parameter, R{sub a} /Q{sub 0} {triple_bond} {l_brace}R/Q{r_brace}, a quantity independent of field or losses which must be obtained from simulation programs, such as the Microwave Studio.
Date: April 5, 2010
Creator: Hahn, H.; Johnson, E. & Kayran, D.
Partner: UNT Libraries Government Documents Department

Design of an achromatic and uncoupled medical gantry for radiation therapy

Description: 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. A medical gantry, as it is used in the radiation treatment of cancer patients, is the last part of the beam optical system, of the accelerator complex, which delivers and focuses the beam on the tumor. The curved line shown in figure 1 is a schematic diagram of a gantry which can rotate about a horizontal axis. The particle beam (green arrow in fig. 1) enters the gantry, and is guided by the gantry on the tumor (red spot in fig. 1). As the gantry rotates about the axis shown in figure 1, the beam exiting the gantry always lies on a plane normal to the rotation axis at the point of the icocenter. Thus the gantry facilitates the ability of the beam delivery system, to deliver the beam at the tumor, which is placed at the icocenter, from any angle on this vertical plane, which is normal to the rotation angle of the gantry as stated earlier. The gantry consists of dipoles and quadrupoles elements whose median symmetry plane lies on a plane which contains the rotation axis of the gantry. In this paper we define this plane as the 'plane of the gantry'. As the beam is transported along ...
Date: March 28, 2011
Creator: Tsoupas, N.; Kayran, D.; Litvinenko, V. & MacKay, W.W.
Partner: UNT Libraries Government Documents Department

Optics-free x-ray FEL oscillator

Description: 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 X-ray range, the spectra of SASE FELs remains rather wide ({approx}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.
Date: March 28, 2011
Creator: Litvinenko, V.N.; Hao, Y.; Kayran, D. & Trbojevic, D.
Partner: UNT Libraries Government Documents Department

Uncoupled achromatic tilted S-bend

Description: A particular section of the electron beam transport line, to be used in the e-cooling project [l] of the Relativistic Heavy Ion Collider (RHIC), is constrained to displace the trajectory with both horizontal and vertical offsets so that the outgoing beamline is parallel to the incoming beamline. We also require that section be achromatic in both planes. This mixed horizontal and vertical achromatic Sbend is accomplished by rotating the two dipoles and the quadrupoles of the line, about the longitudinal axis of the incoming beam. However such a rotation of the magnetic elements may couple the transported beam through the first order beam transfer matrix (linear coupling). In this paper we study a sufficient condition, that the first order transport matrix (R-matrix) can satisfy, so that this section of beam transfer line is both achromatic and linearly uncoupled. We provide a complete solution for the beam optics which satisfies both conditions.
Date: June 23, 2008
Creator: Tsoupas,N.; Kayran, D.; Litvinenko, V. & MacKay, W.W.
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

The machine protection system for the R&D energy recovery LINAC

Description: The Machine Protection System (MPS) is a device-safety system that is designed to prevent damage to hardware by generating interlocks, based upon the state of input signals generated by selected sub-systems. It protects all the key machinery in the R&D Project called the Energy Recovery LINAC (ERL) against the high beam current. The MPS is capable of responding to a fault with an interlock signal within several microseconds. The ERL MPS is based on a National Instruments CompactRIO platform, and is programmed by utilizing National Instruments' development environment for a visual programming language. The system also transfers data (interlock status, time of fault, etc.) to the main server. Transferred data is integrated into the pre-existing software architecture which is accessible by the operators. This paper will provide an overview of the hardware used, its configuration and operation, as well as the software written both on the device and the server side.
Date: March 28, 2011
Creator: Altinbas, Z.; Kayran, D.; Jamilkowski, J.; Lee, R.C. & Oerter, B.
Partner: UNT Libraries Government Documents Department

ELECTRON COOLING SIMULATION FOR ARBITRARY DISTRIBUTION OF ELECTRONS

Description: Typically, several approximations are being used in simulation of electron cooling process, for example, density distribution of electrons is calculated using an analytical expression and distribution in the velocity space is assumed to be Maxwellian in all degrees of freedom. However, in many applications, accurate description of the cooling process based on realistic distribution of electrons is very useful. This is especially true for a high-energy electron cooling system which requires bunched electron beam produced by an Energy Recovery Linac (Em). Such systems are proposed, for instance, for RHIC and electron - ion collider. To address unique features of the RHIC-I1 cooler, new algorithms were introduced in BETACOOL code which allow us to take into account local properties of electron distribution as well as calculate friction force for an arbitrary velocity distribution. Here, we describe these new numerical models. Results based on these numerical models are compared with typical approximations using electron distribution produced by simulations of electron bunch through ERL of RHIC-II cooler.
Date: September 10, 2007
Creator: SIDORIN,A.; SMIRNOV, A.; FEDOTOV, A.; BEN-ZVI, I. & KAYRAN, D.
Partner: UNT Libraries Government Documents Department

ELECTRON COOLING SIMULATIONS FOR LOW-ENERGY RHIC OPERATION.

Description: Recently, a strong interest emerged in running the Relativistic Heavy Ion Collider (RHIC) at low beam total energies of 2.5-25 GeV/nucleon, substantially lower than the nominal beam total energy of 100 GeV/nucleon. Collisions in this low energy range are motivated by one of the key questions of quantum chromodynamics (QCD) about the existence and location of critical point on the QCD phase diagram. Applying electron cooling directly at these low energies in RHIC would result in significant luminosity increase and long beam stores for physics. Without direct cooling in RHIC at these low energies, beam lifetime and store times are very short, limited by strong transverse and longitudinal intrabeam scattering (IBS). In addition, for the lowest energies of the proposed energy scan, the longitudinal emittance of ions injected from the AGS into RHIC may be too big to fit into the RHIC RF bucket. An improvement in the longitudinal emittance of the ion beam can be provided by an electron cooling system at the AGS injection energy. Simulations of electron cooling both for direct cooling at low energies in RHIC and for injection energy cooling in the AGS were performed and are summarized in this report.
Date: September 10, 2007
Creator: FEDOTOV,A.V.; BEN-ZVI, I.; CHANG, X.; KAYRAN, D. & SATOGATA, T.
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

Wake fields effects for the eRHIC project

Description: An Energy Recovery Linac (ERL) with a high peak electron bunch current is proposed for the Electron-Ion collider (eRHIC) project at the Brookhaven National Laboratory. The present design is based on the multi-pass electron beam transport in existing tunnel of the Relativistic Heavy Ion Collider (RHIC). As a result of a high peak current and a very long beam transport, consideration of various collective beam dynamics effects becomes important. Here we summarize effects of the coherent synchrotron radiation, resistive wall, accelerating cavities and wall roughness on the resulting energy spread and energy loss for several scenarios of the eRHIC project.
Date: May 20, 2012
Creator: V., Fedotov A.; Belomestnykh, S.; Kayran, D.; Litvinenko, V. & Ptitsyn, V.
Partner: UNT Libraries Government Documents Department

Design Construction and Test Results of a HTS Solenoid For Energy Recovery Linac

Description: An innovative feature of the proposed Energy Recovery Linac (ERL) is the use of a solenoid made with High Temperature Superconductor (HTS) with the Superconducting RF cavity. The use of HTS allows solenoid to be placed in close proximity to the cavity and thus provides early focusing of the electron beam. In addition, cryogenic testing at {approx}77 K is simpler and cheaper than 4 K testing. This paper will present the design, construction and test results of this HTS solenoid. The HTS solenoid in the proposed ERL will be situated in the transition region between the superconducting cavity at {approx}4 K and the cryostat at the room temperature. Solenoid inside the cryogenic structure provides an early focusing and hence low emittance beam. The temperature in the transition region will be too high for a conventional low temperature superconductor and resistive heat load from copper coils will be too high on cryogenic system. HTS coils also allow much higher current density and significant reduction in size as compared to copper coils. Hence HTS solenoid provide a unique and technically superior solution. The use of a HTS solenoid with superconducting cavity offers a unique option as it can be placed in a cold to warm transition region to provide early focussing without using additional space. Construction and test results so far are very encouraging for its use in the ERL project.
Date: March 28, 2011
Creator: Anerella, M; Ben-Zvi, I; Kayran, D; McIntyre, G; Muratore, J; Plate, S et al.
Partner: UNT Libraries Government Documents Department