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Copper coating specification for the RHIC arcs

Description: Copper coating specifications for the RHIC arcs are given. Various upgrade scenarios are considered and calculations of resistive wall losses in the arcs are used to constrain the necessary quality and surface thickness of a copper coating. We find that 10 {mu}m of high purity copper will suffice.
Date: December 1, 2010
Creator: Blaskiewicz, M.
Partner: UNT Libraries Government Documents Department

Cryogenic sub-system for the 56 MHz SRF storage cavity for RHIC

Description: A 56 MHz Superconducting RF Storage Cavity is being constructed for the RHIC collider. This cavity is a quarter wave resonator that will be operated in a liquid helium bath at 4.4 K. The cavity requires an extremely quiet environment to maintain its operating frequency. The cavity, besides being engineered for a mechanically quiet system, also requires a quiet cryogenic system. The helium is taken from RHIC's main helium supply header at 3.5 atm, 5.3K at a phase separator tank. The boil-off is sent back to the RHIC refrigeration system to recover the cooling. To acoustically separate the RHIC helium supply and return lines, a condenser/boiler heat exchanger condenses the helium vapor generated in the RF cavity bath. A system description and operating parameters are given about the cryogen delivery system. The 56 MHz superconducting storage RF cavity project is making progress. The cryogenic system design is in its final stage. The helium supply lines have been tapped into the RHIC helium distribution lines. The plate-and-fin heat exchanger design is near completion and specification will be sent out for bid soon. The cold helium vapor heating system design will start soon as well. A booster compressor specification is underway. The first phase separator and transfer line design work is near completion and will be sent out for bid soon.
Date: March 28, 2011
Creator: Huang, Y.; Than, R.; Orfin, P.; Lederle, D.; Tallerico, T.; L., Masi et al.
Partner: UNT Libraries Government Documents Department

Concept and architecture of the RHIC LLRF upgrade platform

Description: The goal of the RHIC LLRF upgrade has been the development of a stand alone, generic, high performance, modular LLRF control platform, which can be configured to replace existing systems and serve as a common platform for all new RF systems. The platform is also designed to integrate seamlessly into a distributed network based controls infrastructure, be easy to deploy, and to be useful in a variety of digital signal processing and data acquisition roles. Reuse of hardware, software and firmware has been emphasized to minimize development effort and maximize commonality of system components. System interconnection, synchronization and scaling are facilitated by a deterministic, high speed serial timing and data link, while standard intra and inter chassis communications utilize high speed, non-deterministic protocol based serial links. System hardware configuration is modular and flexible, based on a combination of a main carrier board which can host up to six custom or commercial daughter modules as required to implement desired functionality. This paper will provide an overview of the platform concept, architecture, features and benefits. The RHIC LLRF Upgrade Platform has been developed with the goal of providing a flexible, modular and scalable architecture which will support our current applications and satisfy new ones for the foreseeable future. The platform has been recently commissioned at both RHIC and the RHIC EBIS injector. To date the platform has demonstrated its versatility and utility, meeting the design goals as originally defined.
Date: March 28, 2011
Creator: Smith, K.S.; Hayes, T. & Severino, F.
Partner: UNT Libraries Government Documents Department

Chromatic analysis and possible local chromatic correction in RHIC

Description: In this article we will answer the following questions for the RHIC polarized proton (p-p) and Au-Au run lattices: (1) what are the sources of second order chromaticities? (2) what is the dependence of second order chromaticity on the on-momentum {beta}-beat? (3) what is the dependence of second order chromaticity on {beta}* at IP6 and IP8? To answer these questions, we use the perturbation theory to numerically calculate the contributions of each quadrupole and sextupole to the first, second, and third order chromaticities. Possible local methods to reduce chromatic effects in RHIC ring are shortly discussed.
Date: March 28, 2011
Creator: Luo, Y.; Fischer, W.; Gu, X. & Trbojevic, D.
Partner: UNT Libraries Government Documents Department

Feedback scheme for kink instability in ERL based electron ion collider

Description: 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 opportunity 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. The main advantage of an energy recovery linac (ERL) based electron ion collider (EIC) over a ring-ring type counterpart is the higher achievable luminosity. In ERL-based version, one electron beam collides with the opposing ion beam only once so that the beam-beam parameter can largely exceed the usual limitation in an electron collider ring, while the beam-beam parameter for the ion beam remains small values. The resulting luminosity may be enhanced by one order of magnitude. The beam dynamics related challenges also arise as the luminosity boost in ERL based EIC due to the significant beam-beam effect on the electron beam. The effects on the electron beam include the additional large beam-beam tune shift and nonlinear emittance growth, which are discussed. The ion beam may develop a head-tail type instability, referred as 'kink instability', through the interaction with the electron beam. In this paper, we discuss the feasibility of an active feedback system to mitigate the kink instability, by taking advantage of the flexibility of ERL. Throughout the paper, we will discuss the collision between proton and electron beam. Any other ion species can be scaled by its charge Z and ion mass A.
Date: March 28, 2011
Creator: Hao, Y.; Litvinenko, V.N. & Ptitsyn, V.
Partner: UNT Libraries Government Documents Department

FEL potential of eRHIC

Description: Brookhaven National Laboratory plans to build a 5-to-30 GeV energy-recovery linac (ERL) for its future electron-ion collider, eRHIC. In past few months, the Laboratory turned its attention to the potential of this unique machine for free electron lasers (FELS), which we initially assessed earlier. In this paper, we present our current vision of a possible FEL farm, and of narrow-band FEL-oscillators driven by this accelerator. eRHIC, the proposed electron-ion collider at BNL, takes advantage of the existing Relativistic Heavy Ion Collider (RHIC) complex. Plans call for adding a six-pass super-conducting (SRF) ERL to this complex to collide polarized- and unpolarized- electron beams with heavy ions (with energies up to 130 GeV per nucleon) and with polarized protons (with energies up to 325 GeV). RHIC, with a circumference of 3.834 km, has three-fold symmetry and six straight sections each {approx} 250 m long. Two of these straight sections will accommodate 703-MHz SRF linacs. The maximum energy of the electron beam in eRHIC will be reached in stages, from 5 GeV to 30 GeV, by increasing the lengths of its SRF linacs. We plan to install at the start the six-pass magnetic system with small gap magnets. The structure of the eRHIC's electron beam will be identical with that of its hadron beam, viz., 166 bunches will be filled, reserving about a one-microsecond gap for the abort kicker. With modest modifications, we can assure that eRHIC's ERL will become an excellent driver for continuous wave (CW) FELs (see Fig.1). The eRHIC's beam structure will support the operation of several such FELs in parasitic mode.
Date: August 23, 2010
Creator: Litvinenko, V.N.; Ben-Zvi, I.; Hao, Y.; Kao, C-C.; Kayran, D.; Murphy, J.B. et al.
Partner: UNT Libraries Government Documents Department

Fast BPM data distribution for global orbit feedback using commercial gigabit ethernet technology

Description: In order to correct beam perturbations in RHIC around 10Hz, a new fast data distribution network was required to deliver BPM position data at rates several orders of magnitude above the capability of the existing system. The urgency of the project limited the amount of custom hardware that could be developed, which dictated the use of as much commercially available equipment as possible. The selected architecture uses a custom hardware interface to the existing RHIC BPM electronics together with commercially available Gigabit Ethernet switches to distribute position data to devices located around the collider ring. Using the minimum Ethernet packet size and a field programmable gate array (FPGA) based state machine logic instead of a software based driver, real-time and deterministic data delivery is possible using Ethernet. The method of adapting this protocol for low latency data delivery, bench testing of Ethernet hardware, and the logic to construct Ethernet packets using FPGA hardware will be discussed. A robust communications system using almost all commercial off-the-shelf equipment was developed in under a year which enabled retrofitting of the existing RHIC BPM system to provide 10 KHz data delivery for a global orbit feedback scheme using 72 BPMs. Total latencies from data acquisition at the BPMs to delivery at the controller modules, including very long transmission distances, were kept under 100 {micro}s, which provide very little phase error in correcting the 10 Hz oscillations. Leveraging off of the speed of Gigabit Ethernet and wide availability of Ethernet products enabled this solution to be fully implemented in a much shorter time and at lower cost than if a similar network was developed using a proprietary method.
Date: March 28, 2011
Creator: Hulsart, R.; Cerniglia, P.; Michnoff, R. & Minty, M.
Partner: UNT Libraries Government Documents Department

Polarized proton beams in RHIC

Description: The polarized beam for RHIC is produced in the optically-pumped polarized H{sup -} ion source and then accelerated in Linac to 200 MeV for strip-injection to Booster and further accelerated 24.3 GeV in AGS for injection in RHIC. In 2009 Run polarized protons was successfully accelerated to 250 GeV beam energy. The beam polarization of about 60% at 100 GeV beam energy and 36-42% at 250 GeV beam energy was measured with the H-jet and p-Carbon CNI polarimeters. The gluon contribution to the proton spin was studied in collisions of longitudinally polarized proton beams at 100 x 100 GeV. At 250 x 250 GeV an intermediate boson W production with the longitudinally polarized beams was studied for the first time.
Date: October 4, 2010
Creator: Zelenski, A.
Partner: UNT Libraries Government Documents Department

Multipacting in a grooved choke joint at SRF gun for BNL ERL prototype

Description: The 703 MHz superconducting gun for BNL ERL prototype was tested at JLab with and without choke-joint and cathode stalk. Without choke-joint and cathode stalk, the gradient reached was 25 MV/m with Q{sup 0} {approx} 6E9. The gun cathode insertion port is equipped with a grooved choke joint for multipacting suppression. We carried out tests with choke-joint and cathode stalk. The test results show that there are at least two barriers at about 3.5 MV/m and 5 MV/m. We considered several possibilities and finally found that fine details of the grooved shape are important for multipacting suppression. A triangular groove with round crest may cause strong multipacting in the choke-joint at 3.5 MV/m, 5 MV/m and 10 MV/m. This paper presents the primary test results of the gun and discusses the multipacting analysis in the choke-joint. It also suggests possible solutions for the gun and multipacting suppressing for a similar structure.
Date: March 28, 2011
Creator: Xu, W.; Ben-Zvi, I.; Belomestnykh, S.; Burrill, A.; Holmes, D.; Kayran, D. et al.
Partner: UNT Libraries Government Documents Department

Multiple error data analysis for RHIC low-energy operations

Description: In FY10, RHIC operated with gold beams at three different energies below its regular injection energy, namely at {radical}s = 5 GeV; 7.7 GeV; and 11.5 GeV: While beam lifetimes of about 10 minutes were achieved at 11.5 GeV and 7.7 GeV; leading to stable collider operation, beam lifetimes during tests at {radical}s = 5 GeV were only of the order of several seconds. Though space charge effects are a major concern in low energy operations due to the 1/{gamma}{sup 2} scaling of the space charge force, these can effectively be ruled out as the main cause of this abysmal performance because of the tiny bunch intensities of approximately 10{sub 8} Au/bunch, compared to 10{sup 9} Au/bunch at the two higher energies. During these 5 GeV tests, large betatron tune spreads were observed, but the extremely short beam lifetime prevented chromaticity measurements. Instead, chromaticities were scanned over a range of 40 units, but to no effect. It was therefore suspected at that time that the large tune spread was caused by higherorder multipole errors in the RHIC magnets.
Date: January 1, 2011
Creator: Montag, C.
Partner: UNT Libraries Government Documents Department

Preliminary study for the OFFELO

Description: X-ray Optics-Free FEL Oscillator (OFFELO) has potential of becoming a choice for next generation light sources. Using electron beam for the feedback allows OFFELO to be completely tunable and to combine the peak power of high-gain SASE FELs with extremely narrow bandwidth of the oscillator. While the high-gain X-ray FELs has been studied in depth and has been successfully demonstrated, two other concepts (the transport and the feed-back) involved in OFFELO still need detail studies. In this short paper we focus on the simulation of the feedback process and the evolution of FEL spectrum in X-ray OFFELO. In our initial studies of OFFELO studied the saturation of the system and also its evolution using Genesis 2.0 code with a homemade wrapping code. While and lattice design from the modulator to the radiator, in order to minimize the feedback information loss in transporting the beam.
Date: August 23, 2010
Creator: Hao, Y. & Litvinenko, V.N.
Partner: UNT Libraries Government Documents Department

Nonlinear dynamics experiments

Description: The goal of nonlinear dynamics experiments is to improve the understanding of single particle effects that increase the particle amplitude and lead to loss. Particle motion in storage rings is nearly conservative and for transverse dynamics the Hamiltonian in action angle variables (I{sub x},I{sub y},{phi}{sub x},{phi}{sub y}) near an isolated resonance k{nu}{sub x} + l{nu}{sub y} {approx} p is H = I{sub x}{nu}{sub x0} + I{sub y}{nu}{sub y0} + g(I{sub x}, I{sub y}) + h(I{sub x}, I{sub y})cos(k{phi}{sub x} + l{phi}{sub y} - p{theta}), (1) where k, l, p are integers, {theta} = 2{pi}s/L is the azimuth, and s and L are the path length and circumference respectively. The amplitude dependent tunes are given by {nu}{sub x,y}(I{sub x},I{sub y}) = {nu}{sub x0,y0} + {partial_derivative}g(I{sub x},I{sub y})/{partial_derivative}I{sub x,y} (2) and h(I{sub x},I{sub y}) is the resonance driving term (RDT). If the motion is governed by multiple resonances, h(I{sub x},I{sub y}) has to be replace by a series of terms. The particle motion is completely determined by the terms g and h, which can be calculated from higher order multipoles (Sec. ??), or obtained from simulations. Deviations from pure Hamiltonian motion occur due to synchrotron radiation damping (Sec. ??) in lepton or very high energy hadron rings, parameter variations, and diffusion processes such as residual gas and intrabeam scattering. The time scale of the non-Hamiltonian process determines the applicability of the Hamiltonian analysis. Transverse nonlinearities are introduced through sextupoles or higher order multipoles and magnetic field errors in dipoles and quadrupoles. Sextupoles can already drive all resonances. The beam-beam interaction and space charge also introduce nonlinear fields. Intentionally introduced nonlinearities are used to extract beam on a resonance or through capture in stable islands. Localization and minimization of nonlinearities in a ring is a general strategy to decrease emittance growth and increase ...
Date: January 1, 2011
Creator: Fischer, W.
Partner: UNT Libraries Government Documents Department

Overview of recent studies and modifications being made to RHIC to mitigate the effects of a potential failure to the helium distribution system

Description: In order to cool the superconducting magnets in RHIC, its helium refrigerator distributes 4.5 K helium throughout the tunnel along with helium distribution for the magnet line recoolers, the heat shield, and the associated return lines. The worse case for failure would be a release from the magnet distribution line which operates at 3.5 to 4.5 atmospheres and contains the energized magnet but with a potential energy of 70 MJoules should the insulation system fail or an electrical connection opens. Studies were done to determine release rate of the helium and the resultant reduction in O{sub 2} concentration in the RHIC tunnel and service buildings. Equipment and components were also reviewed for design and reliability and modifications were made to reduce the likelihood of failure and to reduce the volume of helium that could be released.
Date: March 28, 2011
Creator: Tuozzolo, J.; Bruno, D.; DiLieto, A.; Heppner, G.; Karol, R.; Lessard,E. et al.
Partner: UNT Libraries Government Documents Department

Comments on momentum aperture of 100 GeV/n Au runs in RHIC

Description: In RHIC 2010 100 GeV/n Au run, the momentum aperture has been an issue in the re-bucketing and the beam intensity lifetime in store. Both Blue and Yellow beams with comparable storage RF voltage and peak current have suffered more beam loss than in Run 2007. In this note, some comments are made for the momentum aperture of the lattices used from the Au runs in 2007, 2008 and 2010. From the wigglings and the beam decays of each lattice, information regarding the machine momentum aperture is presented. Several directions in further improvement are discussed.
Date: November 1, 2011
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

Commissioning results from the recently upgraded RHIC LLRF system

Description: During RHIC Run 10, the first phase of the LLRF Upgrade was successfully completed. This involved replacing the aging VME based system with a modern digital system based on the recently developed RHIC LLRF Upgrade Platform, and commissioning the system as part of the normal RHIC start up process. At the start of Run 11, the second phase of the upgrade is underway, involving a significant expansion of both hardware and functionality. This paper will review the commissioning effort and provide examples of improvements in system performance, flexibility and scalability afforded by the new platform. The RHIC LLRF upgrade is based on the recently developed RHIC LLRF Upgrade Platform. The major design goals of the platform are: (1) Design a stand alone, generic, digital, modular control architecture which can be configured to satisfy all of the application demands we currently have, and which will be supportable and upgradeable into the foreseeable future; and (2) It should integrate seamlessly into existing controls infrastructure, be easy to deploy, provide access to all relevant control parameters (eliminate knobs), provide vastly improved diagnostic data capabilities, and permit remote reconfiguration. Although the system is still in its infancy, we think the initial commissioning results from RHIC indicate that these goals have been achieved, and that we've only begun to realize the benefits the platform provides.
Date: March 28, 2011
Creator: Smith, K.S.; Harvey, M.; Hayes, T.; Narayan, G.; Severino, F.; Yuan, S. et al.
Partner: UNT Libraries Government Documents Department

Compact, energy EFFICIENT neutron source: enabling technology for various applications

Description: A novel neutron source comprising of a deuterium beam (energy of about 100 KeV) injected into a tube filled with tritium gas and/or tritium plasma that generates D-T fusion reactions, whose products are 14.06 MeV neutrons and 3.52 MeV alpha particles, is described. At the opposite end of the tube, the energy of deuterium ions that did not interact is recovered. Beryllium walls of proper thickness can be utilized to absorb 14 MeV neutrons and release 2-3 low energy neutrons. Each ion source and tube forms a module. Larger systems can be formed from multiple units. Unlike currently proposed methods, where accelerator-based neutron sources are very expensive, large, and require large amounts of power for operation, this neutron source is compact, inexpensive, easy to test and to scale up. Among possible applications for this neutron source concept are sub-critical nuclear breeder reactors and transmutation of radioactive waste.
Date: December 1, 2009
Creator: Hershcovitch, A. & Roser, T.
Partner: UNT Libraries Government Documents Department

Compare 100 GeV/n Au Run 2010 with Run 2007

Description: With the very successful commissioning of the vertical stochastic cooling in 100 GeV/n Au Run 2010, the IBS (intra-beam scattering) is no longer the dominant factor in terms of the integrated luminosity. A new luminosity model is needed, where the beam intensity lifetime is more important and the burn-off needs to be accounted for. Toward this goal, a brief review of the Run 2010, compared with Run 2007, is presented.
Date: January 1, 2011
Creator: Zhang, S.Y.
Partner: UNT Libraries Government Documents Department

A Comparison between a Minijet Model and a Glasma Flux Tube Model for Central Au-Au Collisions at sqrt NN=200 GeV

Description: In this paper we compare two models with central Au-Au collisions at sqrtsNN=200 GeV. The first model is a minijet model which assumes that around ~50 minijets are produced in back-to-back pairs and have an altered fragmentation functions. It is also assumed that the fragments are transparent and escape the collision zone and are detected. The second model is a glasma flux tube model which leads to flux tubes on the surface of a radial expanding fireball driven by interacting flux tubes near the center of the fireball through plasma instabilities. This internal fireball becomes an opaque hydro fluid which pushes the surface flux tubes outward. Around ~12 surfaceflux tubes remain and fragment with ~1/2 the produced particles escaping the collision zone and are detected. Both models can reproduce two particle angular correlations in the different pt1 pt2 bins. We also compare the two models for three additional effects: meson baryon ratios; the long range nearside correlation called the ridge; and the so-called mach cone effect when applied to three particle angular correlations.
Date: May 17, 2011
Creator: Longacre, R.S.
Partner: UNT Libraries Government Documents Department

Comparison of the dynamic apertures in the RHIC 100 GeV and 250 GeV polarized proton runs

Description: In this note we carry out dynamic aperture calcuations to understand the lifetime difference between the 2009 RHIC 100 GeV and 250 GeV polarized proton (p-p) runs. In these two runs the {beta}*s at the interatcion points (IPs) IP6 and IP8 are 0.7 m. We also compare the impacts of interaction region (IR) multipole errors with 2000 A and 5000 A triplet currents on the dynamic aperture. We calculated the dynamic apertures for RHIC 100 GeV and 250 GeV run lattices with same {beta}* = 0.7 m. We found that the dynamic apertures in units of mm are 12.5% and 4.3% smaller at 250 GeV than those at 100 GeV for particles with ({Delta}p/p0) = 3 x 0.0002828 and 3 x 0.0001414 respectively. However, in units of {sigma}, the dynamic apertures at 250 GeV are 36.4% and 51.7% bigger than those at 100 GeV. For particles with the same 3 x ({Delta}p/p0){sub rms}, the dynamic aperture at 250 GeV is almost twice of that at 100 GeV. We conclude that the lifetime difference for the 100 GeV and 250 GeV p-p runs with same {beta}* = 0.7 m lattices is mainly due to the fact that the relative rms momentum spread and rms transverse beam size are smaller than those at 100 GeV. If we install IR multipole errors of 5000 A triplet current to 100 GeV run, the dynamic apertures are reduced by 12.5% and 7% for particles with ({Delta}p/p0) = 3 x 0.0002828 and 3 x 0.0001414 particles, compared to that with IR multipole errors of 2000 A.
Date: January 1, 2011
Creator: Luo, Y.; Gu, X.; Fischer, W. & Trbojevic, D.
Partner: UNT Libraries Government Documents Department

Amplification of current density modulation in a FEL with an infinite electron beam

Description: We show that the paraxial field equation for a free electron laser (FEL) in an infinitely wide electron beam with {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. In developing an analytical model for a FEL-based coherent electron cooling system, an infinite electron beam has been assumed for the modulation and correction processes. While the assumption has its limitation, it allows for an analytical close form solution to be obtained, which is essential for investigating the underlying scaling law, benchmarking the simulation codes and understanding the fundamental physics. 1D theory was previously applied to model a CeC FEL amplifier. However, the theory ignores diffraction effects and does not provide the transverse profile of the amplified electron density modulation. On the other hand, 3D theories developed for a finite electron beam usually have solutions expanded over infinite number of modes determined by the specific transverse boundary conditions. Unless the mode with the largest growth rate substantially dominates other modes, both evaluation and extracting scaling laws can be complicated. Furthermore, it is also preferable to have an analytical FEL model with assumptions consistent with the other two sections of a CeC system. Recently, we developed the FEL theory in an infinitely wide electron beam with {kappa}-1 (Lorentzian) energy distribution. Close form solutions have been obtained for the amplified current modulation initiated by an external electric field with various spatial-profiles. In this work, we extend the theory into {kappa}-2 energy distribution and study the evolution of current density induced by an initial density modulation.
Date: March 28, 2011
Creator: Wang, G.; Litvinenko, V.N. & Webb, S.D.
Partner: UNT Libraries Government Documents Department

Analysis and correction of vertical dispersion in RHIC

Description: In the context of preserving the polarization of proton beams, the source of vertical dispersion in RHIC is analyzed. Contributions to dispersion from non-coupling sources and coupling sources are compared. Based on the analysis of sources for dispersion, the right actuator for correcting dispersion is determined and a corresponding algorithm is developed.
Date: September 14, 2011
Creator: Liu, C. & Minty, M.
Partner: UNT Libraries Government Documents Department

Advances in high-order interaction region nonlinear optics correction at RHIC

Description: A method to indirectly measure and deterministically correct the higher order magnetic errors of the final focusing magnets in the Relativistic Heavy Ion Collider has been in place for several years at BNL. This method yields control over the effects of multi-pole errors through application of closed orbit bumps followed by analysis and correction of the resulting betatron tune shifts using multi-pole correctors. The process has recently been automated in order to provide more efficient and effective corrections. The tune resolution along with the reliability of measurements has also been improved significantly due to advances/upgrades in the betatron tune measurement system employed at RHIC (BBQ). Here we describe the foundation of the IR bump method, followed by recent improvements along with experimental data.
Date: March 28, 2011
Creator: Zimmer, C.; Binello, S.; Minty, M. & Pilat, F.
Partner: UNT Libraries Government Documents Department

ERL R&D: Laser and Laser Light Transport

Description: Operation of the photocathode gun in the ERL requires that a tightly controlled optical pulse train, consisting of temporally and spatially shaped pulses, be delivered at the photocathode in synchrony with the RF field in the gun cavity. The pulse train must also be dynamically variable, in order to tune or ramp up the current in the ERL. A laser was developed especially for this task by Lumera Laser GmbH, of Kaiserslautern Germany, under design supervision and review of the ERL project. Following the final design review, the laser was delivered in August 2009. Preliminary tests certifying its compliance with design specifications have been performed, with further tests planned following the final certification of the ERL laser room in January 2010. The development of the necessary spatial and temporal shaping techniques is an ongoing project: proof of principle experiments have been successfully carried out with a laser of similar pulse width, operating at 532 nm and 81.5 MHz. The next stage is to evaluate the application of these techniques and alternatives, using the operations laser. A transport line has been designed and the propagation of a shaped pulse through it to the photocathode simulated and tested experimentally. As the performance of the complete photocathode drive system is critical for ERL operation, an extensive set of diagnostics will be in place to monitor and maintain its performance. The block diagram in Fig. 1 breaks the optical system down into its basic components, which are discussed.
Date: January 1, 2010
Creator: Sheehy, B.
Partner: UNT Libraries Government Documents Department

Evaluating the dynamic aperture evaluation for the new RHIC 250 GeV polarized proton lattice

Description: To increase luminosity in the Relativistic Heavy Ion Collider's (RHIC's) polarized proton 250 GeV operations, we are considering reducing {beta}* to 0.65 m at the interaction points (IPs), and increasing bunch intensity. The new working point near the 2/3 integer will used on the ramp to preserve polarization. In addition, we plan to adjust the betatron-phase advances between IP6 and IP8 to (k+1/2)*{pi} so to lower the dynamic beta-beat from the beam-beam interaction. The effects of all these changes will impact the dynamic aperture, and hence, it must be evaluated carefully. In this article, we present the results of tracking the dynamic aperture with the proposed lattices.
Date: March 28, 2011
Creator: Gu, X.; Luo, Y.; Fischer, W.; Huang, H. & Tepikian, S.
Partner: UNT Libraries Government Documents Department