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LHC crab-cavity aspects and strategy

Description: The 3rd LHC Crab Cavity workshop (LHC-CC09) took place at CERN in October 2009. It reviewed the current status and identified a clear strategy towards a future crab-cavity implementation. Following the success of crab cavities in KEK-B and the strong potential for luminosity gain and leveling, CERN will pursue crab crossing for the LHC upgrade. We present a summary and outcome of the variousworkshop sessions which have led to the LHC crab-cavity strategy, covering topics like layout, cavity design, integration, machine protection, and a potential validation test in the SPS.
Date: May 23, 2010
Creator: Calaga, R.; Tomas, R. & Zimmermann, F.
Partner: UNT Libraries Government Documents Department

Linear and chromatic optics measurements at RHIC

Description: Measurements of chromatic beta-beating were carried out for the first time in the RHIC accelerator during Run 2009. The analysis package developed for the LHC was used to extract the off-momentum optics for injection and top energy. Results from the beam experiments and compassion to the optics model are presented. The primary goal of the RHIC experiments were execute an on-line measurement of the optics using the tools developed for the LHC. Turn-by-turn BPM trajectories (typically 1000 turns) acquired immediately after an external dipole kick are numerically analyzed to determine the optical parameters at the location of the beam position monitors (BPMs). For chromatic optics, a similar analysis, but on a beam with finite momentum offset(s). Each optical measurement typically is calculated from multiple data sets to capture statistical variations and ensure reproducibility. The procedure of measurement and analysis is detailed in ref [1, 2]. Two dedicated experiments were performed at RHIC with protons during Run 2009. The first at injection energy and optics and the other at 250 GeV and squeezed optics. The basic RHIC parameters relevant for the two experiments are listed in Table 1.
Date: May 23, 2010
Creator: Aiba, M.; Calaga, R.; Aiba, M.; Tomas, R. & Vanbavinkove, G.
Partner: UNT Libraries Government Documents Department

RHIC BBLR measurements in 2009

Description: Long range beam-beam experiments were conducted during the Run 2009 in the Yellow and the Blue beams of the RHIC accelerator with DC wires. The effects of a long-range interaction with a DC wire on colliding and non-colliding bunches with the aid of beam losses, orbits, tunes were studied. Results from distance scans and an attempt to compensate a long-range interaction with a DC wire is presented. Two DC wires in the vertical plane were installed in the RHIC accelerator in 2006 with the aim of investigating long range (LR) beam-beam effects and a potential compensation. Extensive experiments were conducted focusing mainly on the effect of a wire on single ion beams from 2006-2009. A unique opportunity to compare the effect of the wire on colliding beams and compensation of a single LR beam-beam interaction were conducted in Run2009 with protons at 100 GeV. Due to aperture considerations for decreasing {beta}*, the Blue wire was removed during the shutdown after the Run2009 and the Yellow wire is foreseen to be removed in the near future. Therefore, these experiments serve as the final set of measurements for LR beam-beam with RHIC as a test bed. The relevant RHIC beam and lattice parameters are listed in Table 1 for the experiments in Run2009.
Date: May 23, 2010
Creator: Calaga, R.; Robert-Demolaize, G. & Fischer, W.
Partner: UNT Libraries Government Documents Department

Summary of the Mini BNL/LARP/CARE-HHH Workshop on Crab Cavities for the LHC (LHC-CC08)

Description: The first mini-workshop on crab compensation for the LHC luminosity upgrade (LHC-CC08) was held February 24-25, 2008 at the Brookhaven National Laboratory. A total of 35 participants from 3 continents and 15 institutions from around the world participated to discuss the exciting prospect of a crab scheme for the LHC. If realized it will be the first demonstration in hadron colliders. The workshop is organized by joint collaboration of BNL, US-LARP and CARE-HHH. The enormous interest in the subject of crab cavities for the international linear collider and future light sources has resulted in a large international collaboration to exchange aspects of synergy and expertise. A central repository for this exchange of information documenting the latest design effort for LHC crab cavities is consolidated in a wiki page: https://twiki.cern.ch/twiki/bin/view/Main/LHCCrabCavities. The main goal of this workshop was to define a road-map for a prototype crab cavity to be installed in the LHC and to discuss the associated R&D and beam dynamics challenges. The diverse subject of implementing the crab scheme resulted in a scientific program with a wide range of subtopics which were divided into 8 sessions. Each session was given a list of fundamental questions to be addressed and used as a guideline to steer the discussions.
Date: May 1, 2008
Creator: Ben-Zvi,I.; Calaga, R. & Zimmermann, F.
Partner: UNT Libraries Government Documents Department

BPM CALIBRATION INDEPENDENT LHC OPTICS CORRECTION

Description: The tight mechanical aperture for the LHC imposes severe constraints on both the beta and dispersion beating. Robust techniques to compensate these errors are critical for operation of high intensity beams in the LHC. We present simulations using realistic errors from magnet measurements and alignment tolerances in the presence of BPM noise. Correction reveals that the use of BPM calibration and model independent observables are key ingredients to accomplish optics correction. Experiments at RHIC to verify the algorithms for optics correction are also presented.
Date: June 25, 2007
Creator: CALAGA,R.; TOMAS, R.; GIOVANNOZZI, M. & ZIMMERMANN, F.
Partner: UNT Libraries Government Documents Department

Synchro-betatron effects in the presence of large Piwinski angle and crab cavities at the HL-LHC

Description: The reduction of {beta}* at the collision points for the high luminosity LHC (HL-LHC) requires an increment in the crossing angle to maintain the normalized beam separation to suppress the effects of long-range beam-beam interactions. However, an increase in the crossing angle may give rise to synchro-betatron resonances which may negatively affect the beam emittance and lifetime. 6D weak-strong and strong-strong simulations were performed to study the effect of synchro-betatron resonances in the context of the HL-LHC layout and its suppression via crab crossing.
Date: May 20, 2012
Creator: S., White; Calaga, R. & Miyamoto, R.
Partner: UNT Libraries Government Documents Department

HOM damping and multipacting analysis of the quarter-wave crab cavity

Description: The quarter-wave crab cavity design has been analyzed further to accommodate LHC requirements. The goal for the design is to provide strong deflecting voltage to the proton bunches at the IP, while keeping the effective length as short as possible. We will evaluate the higher order mode damping with two or four magnetic coupling dampers installed in different configuration. In this paper, we also show possible multipacting locations which are simulated by 2D and 3D codes.
Date: May 20, 2012
Creator: Q., Wu; Belomestnykh, S.; Ben-Zvi, I. & Calaga, R.
Partner: UNT Libraries Government Documents Department

PROCEDURES AND ACCURACY ESTIMATES FOR BETA-BEAT CORRECTION IN THE LHC.

Description: The LHC aperture imposes a tight tolerance of 20% on the maximum acceptable beta-beat in the machine. An accurate knowledge of the transfer functions for the individually powered insertion quadrupoles and techniques to compensate beta-beat are key prerequisites for successful operation with high intensity beams. They perform realistic simulations to identify quadrupole errors in LHC and explore possible ways of correction to minimize beta-beat below the 20% level.
Date: June 26, 2006
Creator: TOMAS, R.; BRUNING, O. (CERN); CALAGA, R. & PEGGS, S.
Partner: UNT Libraries Government Documents Department

FAST COMPENSATION OF GLOBAL LINEAR COUPLING IN RHIC USING AC DIPOLES.

Description: Global linear coupling has been extensively studied in accelerators and several methods have been developed to compensate the coupling coefficient C using skew quadrupole families scans. However, scanning techniques can become very time consuming especially during the commissioning of an energy ramp. In this paper they illustrate a new technique to measure and compensate, in a single machine cycle, global linear coupling from turn-by-turn BPM data without the need of a skew quadrupole scan. The algorithm is applied to RHIC BPM data using AC dipoles and compared with traditional methods.
Date: June 26, 2006
Creator: CALAGA, R. & FRANCHI, A. (GSI), TOMAS, R.(CERN)
Partner: UNT Libraries Government Documents Department

GLOBAL AND LOCAL COUPLING COMPENSATION EXPERIMENTS IN RHIC USING AC DIPOLES.

Description: Compensation of transverse coupling during the RHIC energy ramp has been proven to be non-trivial and tedious. The lack of accurate knowledge of the coupling sources has initiated several efforts to develop fast techniques using turn-by-turn BPM data to identify and compensate these sources. This paper aims to summarize the beam experiments performed to measure the coupling, matrix and resonance driving terms with the aid of RHIC ac dipoles at injection energy.
Date: June 26, 2006
Creator: CALAGA, R. & FRANCHI, A. (GSI), TOMAS, R.(CERN)
Partner: UNT Libraries Government Documents Department

R&D ERL: HOM Absorbers

Description: Several future accelerator projects at the Relativistic Heavy Ion Collider (RHIC) are based on Energy Recovery Linacs (ERL) with high-charge high-current electron beams. Their stable operation mandates effective higher-order-mode (HOM) damping. The development of HOM dampers for these projects is pursued actively at this laboratory. A strong HOM damping was experimentally demonstrated both at room- and at superconducting- (SC) temperatures in a prototype R&D five-cell niobium SRF cavity with ferrite dampers. A novel type of ferrite damper over a ceramic break for a R&D SRF electron gun also was developed. For future SRF linacs longer cryomodules comprising of multiple superconducting cavities with reasonably short transitions between them are planned. In such a configuration, the dampers, located closer to the cavities, will be at cryogenic temperatures; this will impose additional constraints and complications. Two room-temperature mock-up five-cell copper cavities were used to study various damper configurations. This paper presents results of simulations and measurements for several configurations.
Date: January 1, 2010
Creator: Hahn, H.; Ben-Zvi, I.; Calaga, R.; Hammons, L.; Litvinenko, V.N. & Xu, W.
Partner: UNT Libraries Government Documents Department

Beam losses due to abrupt crab cavity failures in the LHC

Description: A major concern for the implementation of crab crossing in a future High-Luminosity LHC (HL-LHC) is machine protection in an event of a fast crab-cavity failure. Certain types of abrupt crab-cavity amplitude and phase changes are simulated to characterize the effect of failures on the beam and the resulting particle-loss signatures. The time-dependent beam loss distributions around the ring and particle trajectories obtained from the simulations allow for a first assessment of the resulting beam impact on LHC collimators and on sensitive components around the ring. Results for the nominal LHC lattice is presented.
Date: March 28, 2011
Creator: Baer, T.; Barranco, J.; Calaga, R.; Tomas, R.; Wenninger, B.; Yee, B. et al.
Partner: UNT Libraries Government Documents Department

MEASUREMENT AND CORRECTION OF THIRD RESONANCE DRIVING TERM IN THE RHIC

Description: To further improve the luminosity in polarized proton operation of the Relativistic Heavy Ion Collider, correction of the horizontal two-third resonance at store is desirable. The long-lasting coherent beam oscillations, produced by the AC dipole, are used to measure 3Q,'s resonance driving term h{sub 30000} through the analysis of turn-by-turn beam position data with the algorithm outlined by J. Bengtsson. The resonance driving term h30000 can be compensated with the 12 arc chromatic sextupole families. In this article, we will review the technique of h{sub 30000} resonance driving term's measurement and correction with AC dipole excitation in the RHIC, followed by the preliminary beam experiment results from the RHIC 2006 polarized proton run.
Date: June 25, 2007
Creator: LUO,Y.; BAI, M.; BENGTSSON, J.; CALAGA, R.; FISCHER, W. & AL., ET
Partner: UNT Libraries Government Documents Department

SMALL ANGLE CRAB COMPENSATION FOR LHC IR UPGRADE

Description: A small angle (< 1 mrad) crab scheme is an attractive option for the LHC luminosity upgrade to recover the geometric luminosity loss from the finite crossing angle [I]. The luminosity loss increases steeply to unacceptable levels as the IP beta function is reduced below its nominal value (see Fig. 1 in Ref. [2]). The crab compensation in the LHC can be accomplished using only two sets of deflecting RF cavities, placed in collision-free straight sections of the LHC to nullify the effective crossing angles at IPI & IP5. We also explore a 400 MHz superconducting cavity design and discuss the pertinent RF challenges. We present IR optics configurations with low-angle crab crossing, study the beam-beam performance and proton-beam emittance growth in the presence of crab compensation, lattice errors, and crab RF noise sources.
Date: June 25, 2007
Creator: CALAGA,R.; DORDA, U.; OHMI, D.; OIDE, K.; TOMAS, R. & ZIMMERMANN, F.
Partner: UNT Libraries Government Documents Department

THE NEAR-INTEGER WORKING POINT FOR POLARIZED PROTONS IN THE RELATIVISTIC HEAVY ION COLLIDER

Description: To achieve the RHIC polarized proton enhanced luminosity goal of 150.10{sup 30} cm{sup -2}sec{sup -} on average in stores at 250 GeV, the luminosity needs to be increased by a factor of 3 compared to what was achieved in 2006. Since the number of bunches is already at its maximum of 1 1 1, limited by the injection kickers and the experiments' time resolution, the luminosity can only be increased by either increasing the bunch intensity and/or reducing the beam emittance. This leads to a larger beam-beam tuneshift parameter. Operations during 2006 has shown that the beam-beam interaction is already dominating the luminosity lifetime. To overcome this limitation, a near-integer working point is under study. We will present recent results of these studies.
Date: June 25, 2007
Creator: MONTAG,C.; BAI, M.; BEEBE-WANG, J.; CALAGA, R.; BLASKIEWICZ, M. & AL., ET
Partner: UNT Libraries Government Documents Department

TRANSVERSE BEAM TRANSFER FUNCTIONS OF COLLIDING BEAMS IN RHIC

Description: We use transverse beam transfer functions to measure tune distributions of colliding beams in RHIC. The tune has a distribution due to the beam-beam interaction, nonlinear magnetic fields -- particularly in the interaction region magnets, and non-zero chromaticity in conjunction with momentum spread. The measured tune distributions are compared with calculations.
Date: June 25, 2007
Creator: FISCHER,W.; BLASKIEWICZ, M.; CALAGA, R.; CAMERON, P.; HERR, W. & PIELONI, T.
Partner: UNT Libraries Government Documents Department

EXPERIMENTS WITH A DC WIRE IN RHIC

Description: A DC wire has been installed in RHIC to explore the long-range beam-beam effect, and test its compensation. We report on experiments that measure the effect of the wire's electro-magnetic field on the beam's lifetime and tune distribution, and accompanying simulations.
Date: June 25, 2007
Creator: FISCHER,W.; CALAGA, R.; DORDA, U.; KOUTCHOUK, J.-P.; ZIMMERMANN, F. & SEN, T.
Partner: UNT Libraries Government Documents Department

HOM identification by bead pulling in the Brookhaven ERL cavity

Description: Several past measurements of the Brookhaven ERL at superconducting temperature produced a long list of higher order modes (HOMs). The Niobium 5-cell cavity is terminated with HOM ferrite dampers that successfully reduce the Q-factors to tolerable levels. However, a number of undamped resonances with Q {ge} 10{sup 6} were found at 4 K and their mode identification remained as a goal for this paper. The approach taken here consists in taking different S{sub 21} measurements on a copper cavity replica of the ERL which can be compared with the actual data and also with Microwave Studio computer simulations. Several different S{sub 21} transmission measurements are used, including those taken from the fundamental input coupler to the pick-up probe across the cavity, between probes in a single cell, and between beam-position monitor probes in the beam tubes. Mode identification is supported by bead pulling with a metallic needle or a dielectric sphere that are calibrated in the fundamental mode. This paper presents results for HOMs in the first two dipole bands with the prototypical 958 MHz trapped mode, the lowest beam tube resonances, and high-Q modes in the first quadrupole band and beyond.
Date: June 25, 2012
Creator: Hahn, H.; Calaga, R.; Jain, P.; Johnson, E.C. & Xu, W.
Partner: UNT Libraries Government Documents Department

LHC beam-beam compensation studies at RHIC

Description: Long-range and head-on beam-beam effects are expected to limit the LHC performance with design parameters. To mitigate long-range effects current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. To reduce the head-on beam-beam effect electron lenses were proposed for both the LHC and RHIC. We present the experimental long-range beam-beam program and report on head-on compensations studies at RHIC, which are based on simulations.
Date: May 4, 2009
Creator: Fischer,W.; Abreu, N.; Calaga, R.; Robert-Demolaize, G.; Luo, Y. & Montag, C.
Partner: UNT Libraries Government Documents Department