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Vahid Ranjbar

Brookhaven National Laboratory, Collider Accelerator, Physicist

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IISER, Pune

Monash University

Arizona State University

Emmanuel T Rodulfo

De La Salle University

Mohammad Mehdi Firoozabadi

The University of Birjand

Helmholtz-Zentrum Dresden Rossendorf

Umass Boston

Serkan Caliskan

Fatih University

Laurent Nadolski

Synchrotron SOLEIL

University of Majmaah

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articles by Vahid Ranjbar

Polarization Response of RHIC e-lens lattices

Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in d... more Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in depth using lattice independent spin integration. In particular we consider the effect of overlapping spin resonances in this system, to understand the impact of phase, tune, relative location and threshold strengths of the spin resonances. These results are bench-marked and compared to two dimensional direct tracking results for the RHIC e-lens lattice and the standard lattice. Finally we consider effect of longitudinal motion via chromatic scans using direct six dimensional lattice tracking.

Commissioning and Future Plans for Polarized Protons in RHIC

Fitting Helical Snake and Rotator Field Strength Measurements in RHIC

Head - tail instability at Tevatron

First polarized proton collisions at RHIC

$Research paper thumbnail of 20\% partial Siberian snake in the AGS$

20\% partial Siberian snake in the AGS

RHIC spin flipper commissioning

Preserving polarization through an intrinsic depolarizing resonance with a partial snake at the AGS

Chromaticity Head-Tail Application for the Tevatron

Status of Proof-of-principle Experiment for Coherent Electron Cooling

Optics Measurements and Corrections at RHIC

High-order modeling of an ERL for electron cooling in the RHIC Luminosity Upgrade using MaryLie/IMPACT

$Research paper thumbnail of Status of the R\&D towards electron cooling of RHIC$

Status of the R\&D towards electron cooling of RHIC

by Vahid Ranjbar, H. Hahn, R. Calaga, T. Rao, T. Tallerico, and Tom Schultheiss

Advanced accelerator control and instrumentation modules based on FPGA

Continuous transverse excitation for measuring chromaticity from the head-tail phase difference: an analytic approximation with experimental data

Chromaticity measurement using a continuous head-tail kicking technique

Multiple Tune Jumps to Overcome Horizontal Depolarizing Resonances

AGS lattice changes to eliminate weak intrinsic resonances

by Vahid Ranjbar and Andreas Lehrach

The analysis of depolarization factors in the last RHIC run

Spin coupling resonance and suppression in the AGS

Polarization Response of RHIC e-lens lattices

Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in d... more Depolarization response for a system of two orthogonal snakes at irrational tunes is studied in depth using lattice independent spin integration. In particular we consider the effect of overlapping spin resonances in this system, to understand the impact of phase, tune, relative location and threshold strengths of the spin resonances. These results are bench-marked and compared to two dimensional direct tracking results for the RHIC e-lens lattice and the standard lattice. Finally we consider effect of longitudinal motion via chromatic scans using direct six dimensional lattice tracking.

Commissioning and Future Plans for Polarized Protons in RHIC

Fitting Helical Snake and Rotator Field Strength Measurements in RHIC

Head - tail instability at Tevatron

First polarized proton collisions at RHIC

$Research paper thumbnail of 20\% partial Siberian snake in the AGS$

20\% partial Siberian snake in the AGS

RHIC spin flipper commissioning

Preserving polarization through an intrinsic depolarizing resonance with a partial snake at the AGS

Chromaticity Head-Tail Application for the Tevatron

Status of Proof-of-principle Experiment for Coherent Electron Cooling

Optics Measurements and Corrections at RHIC

High-order modeling of an ERL for electron cooling in the RHIC Luminosity Upgrade using MaryLie/IMPACT

$Research paper thumbnail of Status of the R\&D towards electron cooling of RHIC$

Status of the R\&D towards electron cooling of RHIC

by Vahid Ranjbar, H. Hahn, R. Calaga, T. Rao, T. Tallerico, and Tom Schultheiss

Advanced accelerator control and instrumentation modules based on FPGA

Continuous transverse excitation for measuring chromaticity from the head-tail phase difference: an analytic approximation with experimental data

Chromaticity measurement using a continuous head-tail kicking technique

Multiple Tune Jumps to Overcome Horizontal Depolarizing Resonances

AGS lattice changes to eliminate weak intrinsic resonances

by Vahid Ranjbar and Andreas Lehrach

The analysis of depolarization factors in the last RHIC run

Spin coupling resonance and suppression in the AGS

Increasing proton polarization in AGS and RHIC

Accelerating and colliding polarized protons in RHIC with Siberian snakes

We successfully injected polarized protons in both RHIC rings and maintained polarization during ... more We successfully injected polarized protons in both RHIC rings and maintained polarization during acceleration up to 100 GeV per ring using two Siberian snakes in each ring. Each snake consists of four helical superconducting dipoles which rotate the polarization by 180 • about a horizontal axis. This is the first time that polarized protons have been accelerated to 100 GeV. We report on our experiences during commissioning and operation of collider with polarized protons.

RHIC spin flipper commissioning

An ac dipole with horizontally oriented oscillating magnetic field (spin flipper) was installed i... more An ac dipole with horizontally oriented oscillating magnetic field (spin flipper) was installed in RHIC to reverse the spin direction in the presence of two full Siberian snakes, thereby reducing the systematic errors for the spin physics experiments in RHIC. With two full snakes, the spin vector completes one full precession around the vertical direction in two revolutions, and the spin depolarization resonances due to the machine imperfections and betatron oscillations are eliminated. Since the spin flipper provides an oscillating horizontal dipole field, a "spin resonance" can occur if the spin flipper frequency is placed in the neighborhood of the spin precession frequency [1, 2, 3]. By slowly sweeping the spin flipper frequency across the spin precession frequency, a full spin flip can be achieved. This paper reports the results of the RHIC spin flipper commissioned during the RHIC 2002 polarized proton run. By running the spin flipper at a slightly different configuration, one can also measure the spin precession tune.

Polarized proton acceleration at the Brookhaven AGS: An update

The RHIC spin design goal assumes 2 × 10 11 proton/bunch with 70% polarization. As the injector t... more The RHIC spin design goal assumes 2 × 10 11 proton/bunch with 70% polarization. As the injector to RHIC, polarized protons have been accelerated at the AGS for years to increase the polarization transmission efficiency. Several novel techniques have been applied in the AGS to overcome the intrinsic and imperfection resonances. The present level of accelerator performance is discussed. Progress on understanding the beam polarization behavior is presented. The outlook and future plan are also discussed.

Spin coupling resonance study in AGS

In the AGS spin resonances due to coupling may account for as much as a 50 percent loss in polari... more In the AGS spin resonances due to coupling may account for as much as a 50 percent loss in polarization at a reduced acceleration rate. The major source of coupling in the AGS is the solenoidal snake. In the past some preliminary work was done to understand this phenomena [1], and a method to overcome these resonances was attempted . However in the polarized proton run of 2002 we sought to study more thoroughly the response of these coupled spin resonances to the strength of the solenoidal snake, skew quadrupoles and vertical and horizontal betatron tune separation. In this paper we present our results and compare them with those predicted by a modified DEPOL program .

Snake calibration in RHIC

A proper understanding of the response of the spin orientation due to the currents in the four he... more A proper understanding of the response of the spin orientation due to the currents in the four helices which make up each snake is necessary to control spin tune, avoid snake resonances and facilitate the operation of the RHIC spin flipper. The effect of the helical dipole snakes in RHIC is to rotate the spin orientation an angle µ about an axis at an angle φ in the horizontal plane. With two snakes the combined effect gives rise to a spin precession frequency which is determined by the µ and φ angles at each snake. Depolarization or spin flipping can occur when this spin tune is near an external driving frequency. We employed the RHIC spin flipper in this way to determine the spin tune and thus verify spin tune predictions based upon previous field measurements of the snake. We also considered the response of snake resonances locations to spin tune as another way of verifying spin tune predictions

Overcoming the Horizontal Depolarizing Resonance in the Brookhaven AGS

Imperfection and vertical intrinsic depolarizing resonances have been overcome by the two partial... more Imperfection and vertical intrinsic depolarizing resonances have been overcome by the two partial Siberian snakes in the Alternative Gradient Synchrotron(AGS). The relatively weak but numerous horizontal resonances are the main source of polarization loss in the AGS. A pair of horizontal quads have been used to overcome these weak resonances. This technique needs very accurate jump timing. The keys for the system are the accurate control of the jump quad timing and the elimination of any emittance growth. Fast rollover magnet cycle has been used and it improves the horizontal tune jump quads setup. Recent experimental results including jump quad timing and emittance preservation are presented in this paper. WEPRO070

RHIC Performance during the 7.5 GeV Low Energy Run in FY 2014

As the last step of phase 1 of the beam energy scan (BES-I), aimed at the search for the critical... more As the last step of phase 1 of the beam energy scan (BES-I), aimed at the search for the critical point in the QCD phase diagram, RHIC collided gold ions at a beam energy of 7.3 GeV/nucleon during the FY 2014 run. While this particular energy is close to the nominal RHIC injection energy of 9.8 GeV/nucleon, it is nevertheless challenging because it happens to be close to the AGS transition energy, which makes longitudinal beam dynamics during transfer from the AGS to RHIC difficult. We report on machine performance, obstacles and solutions during the FY 2014 low energy run.

Simulation Study of Head-on Beam-beam Compensation with Realistic RHIC Lattices

To reduce the beam-beam resonance driving terms with half head-on beam-beam compensation in the R... more To reduce the beam-beam resonance driving terms with half head-on beam-beam compensation in the RHIC polarized-proton operations, the betatron phase advances between the interaction point IP8 and the center of the electron lenses located around IP10 should be kπ, where k is an integer. Realistic beam-beam compensation lattices meeting the phase advance requirements were developed and used in the beginning of 2013 polarized proton run, although head-on beam-beam compensation was not implemented yet. In this article, with these lattices and a 6-D weak-strong beam-beam simulation model, we calculate the proton dynamic apertures with and without beam-beam compensation. Preliminary results with second order chromaticity correction are also presented. ISBN 978-3-95450-122-9 1542 Copyright c ○ 2013 by JACoW -cc Creative Commons Attribution 3.0 (CC-BY-3.0) 01 Circular and Linear Colliders A01 Hadron Colliders A01 Hadron Colliders ISBN 978-3-95450-122-9 1543 Copyright c ○ 2013 by JACoW -cc Creative Commons Attribution 3.0 (CC-BY-3.0)

AGS Model in Zgoubi. RHIC Run 13 Polarization Modeling. Status.

This paper gives a status of the AGS model in the raytracing code Zgoubi and its operation via th... more This paper gives a status of the AGS model in the raytracing code Zgoubi and its operation via the "AgsZgoubi-Model" and the "AgsModelViewer" applications available from the controls system application launcher, "StartUp". Examples of typical uses and studies performed using these are included, as optics controls, spin matching to RHIC, etc. A companion paper (MOPWA085) gives additional details, regarding especially spin dynamics and polarization studies aimed at determining optimal AGS settings for polarization during RHIC Run 13. This work is an additional step towards further combination with the already existing RHIC spin tracking model in Zgoubi, and AGS's Booster model in Zgoubi, a promising suite for detailed beam and spin dynamics studies and optimizations.

IR upgrade with quadrupoles first and dipoles first

Spin Dynamics Simulations and Horizontal Intrinsic Resonance Studies in the AGS using the Zgoubi Code

A critical point for the polarized proton program of RHIC 1 is the polarization transmission duri... more A critical point for the polarized proton program of RHIC 1 is the polarization transmission during the AGS 2 acceleration cycle. Recent developments in the Zgoubi model of the AGS[1] allow multi-particle tracking with realistic beam and machine conditions on a large scale computing system. This gives the opportunity to simulate the influence of many beam and machine conditions on the polarization transmission and leads to a better understanding of the depolarization processes, for instance the horizontal intrinsic resonances, that cannot be accurately explored by the conventional simulation approaches or by the experiments with beam. This paper introduces the developments realized on the Zgoubi code to run these simulations and shows some of the latest results. *

GPU-accelerated Spin Dynamics and Analysis for RHIC

The elucidation of nucleon spin structure benefits from highly polarized beams in storage rings. ... more The elucidation of nucleon spin structure benefits from highly polarized beams in storage rings. Accurate and fast spin dynamics simulations are a valuable tool for optimizing beam polarization. We describe the integrators and the performance of a new spin-orbit tracking code. These integrators use quaternions and Romberg quadratures to accelerate both the computation and the convergence of spin rotations. We exploit the inherently data-parallel nature of spin tracking to accelerate our algorithms on graphics processing units.

Status and Plans for the Polarized Hadron Collider at RHIC

As the world's only high energy polarized proton collider, the Relativistic Heavy Ion Collider (R... more As the world's only high energy polarized proton collider, the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL) has been providing collisions of polarized proton beams at beam energy from 100 GeV to 255 GeV for the past decade to explore the proton spin structure as well as other spin dependent measurements. With the help of two Siberian Snakes per accelerator plus outstanding beam control, beam polarization is preserved up to 100 GeV. About 10% polarization loss has been observed during the acceleration between 100 GeV and 255 GeV due to several strong depolarizing resonances. Moderate polarization loss was also observed during a typical 8 hour physics store.

First RHIC Collider Test Operation at 2.5GeV Beam Energy

To search for the critical point in the QCD phase diagram, RHIC needs to operate at a set of low ... more To search for the critical point in the QCD phase diagram, RHIC needs to operate at a set of low gold beam energies between 2.5 and 20 GeV per nucleon. During run 12, first successful collider operation at the lowest energy of 2.5 GeV per nucleon was achieved. We present the challenges and achieved results, and discuss possible future upgrades and improvements.

RHIC Polarized Proton Operation for 2013

The 2013 operation of the Relativistic Heavy Ion Collider (RHIC) marks the second year of running... more The 2013 operation of the Relativistic Heavy Ion Collider (RHIC) marks the second year of running under the RHIC II era. This year saw the implementation of several important upgrades designed to push the intensity frontier. Two new electron lenses to compensate beam-beam effects (e-lenses) have been partially installed, along with a new lattice designed for the e-lens operation. A new polarized proton source which generates about factor of 2 more intensity was commissioned as well as a host of RF upgrades ranging from a new longitudinal damper a new Landau cavity in RHIC to a new low level RF system and new beam bunching structure in AGS. We present an overview of the challenges and results from this years run.

Reducing Spin Tune Spread by Matching DX Prime at Snakes in RHIC

At the Relativistic Heavy Ion Collider (RHIC) at BNL the physics program includes collisions betw... more At the Relativistic Heavy Ion Collider (RHIC) at BNL the physics program includes collisions between beams of polarized protons at high beam energies. Maintaining the proton's polarization is vital and preserved primarily by application of a pair of Siberian snakes . Measurements from recent high-energy physics runs indicate polarization loss during acceleration between 100 and 250 GeV [2]. Based on analytic estimations for off-momentum particles and/or beams, a nonzero difference in DX prime -the dispersion function angle -between the snakes can result in a spread in the spin tune , or equivalently, the conditions of snake resonances in close proximity to the beam during acceleration. Requiring that DX prime at the two Siberian snakes in RHIC be equal would reduce the spin tune shift for off-energy particles so helping to maintain polarization during the energy ramp. Preservation of half-integer spin tune is also important for future operation of the spin flipper [5] at store. In this report, the matching scheme and simulations using MAD-X will be presented together with a newly applied method based on response matrices to take power supply limitations into account in the minimization procedure.

New Diffusion Analysis Tools for Beam Beam Simulations

A new set of tools for BBSIM[1] has recently been developed to analyze the nature of the diffusio... more A new set of tools for BBSIM[1] has recently been developed to analyze the nature of the diffusion in multiparticle simulations. The diffusion subroutines are currently used to accelerate beam lifetime calculations by estimating the diffusion coefficient at various actions and integrating the diffusion equation. However it is possible that there may be regimes where anomalous diffusion dominates and normal diffusion estimates are incorrect. The tools we have developed estimate the deviation from normal diffusion and can fit the coefficients of a jump diffusion model in the event that this type of diffusion dominates.

BTF Simulations for Tevatron and RHIC with Resistive Wall Wake Field

Recent improvements to BBSIM[1] permit detailed simulations of collective effects due to resistiv... more Recent improvements to BBSIM[1] permit detailed simulations of collective effects due to resistive wall wake fields. We compare results of beam transfer measurements (BTF) in the Tevatron and RHIC with and without the effects of resistive wall wake fields. These are then compared to actual BTF measurements made in both machines and the impact of intensity on our measurements.

Spin Resonance Strength Calculation Through Single Particle Tracking for RHIC

The strengths of spin resonances for the polarized-proton operation in the Relativistic Heavy Ion... more The strengths of spin resonances for the polarized-proton operation in the Relativistic Heavy Ion Collider are currently calculated with the code DEPOL, which numerically integrates through the ring based on an analytical approximate formula. In this article, we test a new way to calculate the spin resonance strengths by performing Fouier transformation to the actual transverse magnetic fields seen by a single particle traveling through the ring. Comparison of calculated spin resonance strengths is made between this method and DEPOL.

Proton Spin Tracking with Symplectic Integration of Orbit Motion

Symplectic integration had been adopted for orbital motion tracking in code SimTrack. SimTrack ha... more Symplectic integration had been adopted for orbital motion tracking in code SimTrack. SimTrack has been extensively used for dynamic aperture calculation with beambeam interaction for the Relativistic Heavy Ion Collider (RHIC). Recently proton spin tracking has been implemented on top of symplectic orbital motion in this code. In this article, we will explain the implementation of spin motion based on Thomas-BMT equation, and the benchmarking with other spin tracking codes currently used for RHIC. Examples to calculate spin closed orbit and spin tunes are presented too.

Spin coupling resonance and suppression in the AGS

Physical Review Special Topics - Accelerators and Beams, 2004

Spin depolarizing resonances due to coupling may account for as much as a 30 percent loss in pola... more

Spin resonance free electron ring injector

Physical Review Accelerators and Beams

We have developed an intrinsic resonance free circular electron accelerator. This lattice could b... more

Towards the modeling of ICRH using the delta-f particle-in-cell method in RZ geometry

The delta-f particle-in-cell (DFPIC) method is a PIC method with a high signal-to-noise ratio whi... more The delta-f particle-in-cell (DFPIC) method is a PIC method with a high signal-to-noise ratio which has been used for modeling electron Bernstein waves and ion cyclotron fast waves. It offers the capacity to model particle behavior such as multiple pass resonance, banana orbits, and superadiabaticity. It presents an alternative to linear wave codes like AORSA and TORIC which include only first-order parallel and perpendicular gradient variations of cyclotron frequency. Here we explore the use of the DFPIC method in the VORPAL computational framework for ion cyclotron resonance heating in RZ geometries based on eqdisk fusion data. We also consider the coupling to the bounce-averaged nonlinear Fokker-Planck code, CQL3D, through the generation of quasi-linear diffusion coefficients using a novel approach based on the DFPIC method. A benchmarking of the quasi-linear diffusion coefficients generated with the DFPIC method will be presented in 1D.

Accelerated Particle Tracking Using Gpulib

A 4D version of BNL's spin tracking code SPINK [1] with limited elements has been successfull... more A 4D version of BNL's spin tracking code SPINK [1] with limited elements has been successfully ported to a C++/GPU platform using GPULib [2]. This prototype used only quadrupoles, simple snakes, dipoles and drifts. We present the approach used to track spin and orbit degrees of freedom of polarized proton beams simultaneously. We also present recent results of prototyping a general-purpose particle tracking on GPUs, discussing our CUDA im-plementation of maps for single-particle dynamics in the Argonne National Lab's accelerator code ELEGANT [3] where a 40x speedup was achieved for single-particle-dynamics elements.

Phase transitions in a ferromagnetic-antiferromagnetic-ferromagnetic trilayer

The phase diagram of a magnetic trilayer system consisting of four AFM planes sandwiched between ... more The phase diagram of a magnetic trilayer system consisting of four AFM planes sandwiched between three FM planes on the top and bottom was examined using a Monte Carlo numerical simulation. The magnetic spins were represented by an eight-state clock model on a bcc lattice with free surfaces on the top and bottom. Next-nearest-neighbor interactions were included, but no anisotropy fields were considered. The behavior of the trilayer was studied as a function of both temperature and external field. Four phases were observed: antiferromagnetic, spin flop, layer flop, and paramagnetic. abstract.

Observation of Long-Range Beam-Beam Effect in RHI;IC And Plans For Compensation

At large distances the electromagnetic field of a wire is the same as the field produced by a bun... more At large distances the electromagnetic field of a wire is the same as the field produced by a bunch. Such a longrange beam-beam wire compensator was proposed for the LHC, and single beam tests with wire compensators were successfully done in the SPS. RHIC offers the possibility to test the compensation scheme with colliding beams. We report on measurements of beam losses as a function of transverse separation in RHIC at 1 OOGeV, and comparisons with simulations. We present a design for a long-range wire compensator in RHIC.

Predictive design and interpretation of colliding pulse injected laser wakefield experiments

Simulation

The use of colliding laser pulses to control the injection of plasma electrons into the plasma wa... more The use of colliding laser pulses to control the injection of plasma electrons into the plasma wake of a laser plasma accelerator is a promising approach to obtaining stable, tunable electron bunches with reduced emittance and energy spread. Colliding Pulse Injection (CPI) experiments are being performed by groups around the world. We will present recent particle-in-cell simulations, using the parallel VORPAL framework, of CPI for physical parameters relevant to ongoing experiments of the LOASIS program at LBNL. We evaluate the effect of laser and plasma tuning, on the trapped electron bunch and perform parameter scans in order to optimize the quality of the bunch. Impact of non-ideal effects such as imperfect laser modes and laser self focusing are also evaluated. Simulation data are validated against current experimental results, and are used to design future experiments.

Design and Interpretation of Colliding Pulse Injected Laser-Plasma Acceleration Experiments

The use of colliding laser pulses to control the injection of plasma electrons into the plasma wa... more The use of colliding laser pulses to control the injection of plasma electrons into the plasma wake of a laser-plasma accelerator is a promising approach to obtaining GeV scale electron bunches with reduced emittance and energy spread. Colliding Pulse Injection (CPI) experiments are being performed by groups around the world. We present recent particlein-cell simulations, using the parallel VORPAL framework, of CPI for physical parameters relevant to ongoing experiments of the LOASIS program at LBNL. We perform parameter scans in order to optimize the quality of the bunch, and compare the results with experimental data. Effect of non-ideal gaussian pulses and laser self-focusing in the plasma channel on the trapped bunch are evaluated. For optimized parameters accessible in the experiment, a 20 pC electron beam can be accelerated to 300 MeV with percent level energy spread.

Towards the modeling of ICRH using the delta-f particle-in-cell method in RZ geometry

Bulletin of the American Physical …, 2009

The delta-f particle-in-cell (DFPIC) method is a PIC method with a high signal-to-noise ratio whi... more

Report of the eRHIC Ring-Ring Working Group

RHIC operation with asymmetric collisions in 2015

High-order modeling of an ERL for electron cooling

2007 IEEE Particle Accelerator Conference (PAC), 2007

Plans for the RHIC luminosity upgrade call for an electron cooling system that will place substan... more Plans for the RHIC luminosity upgrade call for an electron cooling system that will place substantial demands on the energy, current, brightness, and beam quality of the electron beam. In particular, the requirements demand a new level of fidelity in beam dynamics simulations. New developments in MARYLIE/IMPACT have improved both the space-charge computations for beams with large aspect ratios and the beam dynamic computations for rf cavities. We present the results of beam dynamics simulations that include the effects of space charge and nonlinearities, and aim to assess the tolerance for errors and nonlinearities on current designs for a super-conducting ERL.

Computing quasi-linear diffusion coefficients using the delta-f particle-in-cell method

ABSTRACT Linear wave codes AORSA and TORIC couple to the bounce-averaged nonlinear Fokker-Planck ... more ABSTRACT Linear wave codes AORSA and TORIC couple to the bounce-averaged nonlinear Fokker-Planck code CQL3D through quasi-linear diffusion coefficients. Both linear wave codes rely on the quasi-local approximation that includes only first-order parallel and perpendicular gradient variations of cyclotron frequency and ignores field line curvature along with temperature and density gradient effects. The delta-f particle-in-cell (DFPIC) method has been successfully used for simulating ion-cyclotron fast wave behavior. This method also permits particle behavior such as multiple pass resonance, banana orbits, and superadiabaticity. We present new work on generating quasi-linear diffusion coefficients using the DFPIC method that will permit the electromagnetic particle-in-cell (EMPIC) code, VORPAL, to couple to CQL3D and to compare to AORSA and TORIC. A new multiple weight delta-f approach will be presented that converts velocity derivatives to action derivatives and yields a full tensor quasi-linear diffusion coefficient.

Mapping out the full spin resonance structure of RHIC

Particle Accelerator, IEEE Conference, 2001

We extended the ability of DEPOL to calculate coupled spin resonances and used it to determine th... more We extended the ability of DEPOL to calculate coupled spin resonances and used it to determine the location and strength of both intrinsic and coupled spin resonances in RHIC. In particular we are interested in the full resonance structure with solenoidal elements turned on and with quadrupole rolls

Possible Depolarization Mechanism due to Low Beta Squeeze

Simulations reveal a potential depolarization mechanism during low beta squeeze.This depolarizati... more Simulations reveal a potential depolarization mechanism during low beta squeeze.This depolarization appears to be driven by a spin tune modulation caused by spin precession through the strong low beta quads due to the vertical fields. The modulation of the spin tune introduces an additional snake resonance condition at νs0 ± nνx − νzl = integer which while the same numerology as the well known sextupole resonance, can operate in the absence of sextupole elements.

Suppressing intrinsic spin harmonics in the AGS

Over the last decade several improvements have been made to increase the polarization of the prot... more Over the last decade several improvements have been made to increase the polarization of the proton beam at the Brookhaven Alternating Gradient Synchrotron (AGS) [1]. A partial snake was installed to overcome all imperfection resonances in the energy range of the AGS [2]. The rf dipole concept to preserve polarization at strong intrinsic resonances has been demonstrated at the AGS for the first time [3]. Polarization losses have been observed at weak intrinsic resonances. One method to preserve polarization at weak intrinsic resonances is to change the betatron tune rapidly before crossing the resonance. Due to the non-adiabatic nature of this tune jump, the beam emittance will increase [4]. More efficient is a method called suppressing intrinsic spin harmonics, first successfully applied at the Cooler Synchrotron COSY [5]. In this presentation we describe how to use this method at the AGS [6]. .

Proof-of-principle experiment for FEL-based coherent electron cooling

Coherent electron cooling (CEC) has a potential to significantly boost luminosity of high-energy,... more Coherent electron cooling (CEC) has a potential to significantly boost luminosity of high-energy, highintensity hadron-hadron and electron-hadron colliders. In a CEC system, a hadron beam interacts with a cooling electron beam. A perturbation of the electron density caused by ions is amplified and fed back to the ions to reduce the energy spread and the emittance of the ion beam. To demonstrate the feasibility of CEC we propose a proof-of-principle experiment at RHIC using SRF linac. In this paper, we describe the setup for CeC installed into one of RHIC's interaction regions. We present results of analytical estimates and results of initial simulations of cooling a gold-ion beam at 40 GeV/u energy via CeC.