Paper | Title | Page |
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MOOHC2 | The US Electron Ion Collider Accelerator Designs | 1 |
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With the completion of the National Academies of Sciences Assessment of a US Electron-Ion Collider, the prospects for construction of such a facility have taken a step forward. This paper provides an overview of the two site-specific EIC designs: JLEIC (Jefferson Lab) and eRHIC (BNL) as well as brief overview of ongoing EIC R&D. | ||
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Slides MOOHC2 [14.774 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOOHC2 | |
About • | paper received ※ 29 August 2019 paper accepted ※ 04 September 2019 issue date ※ 08 October 2019 | |
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MOYBA4 | eRHIC Design Update | 18 |
TUPLO11 | use link to see paper's listing under its alternate paper code | |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The future electron-ion collider (EIC) aims at an electron-proton luminosity of 1033 to 1034 cm-2 sec-1 and a center-of-mass energy range from 20 to 140 GeV. The eRHIC design has been continuously evolving over a couple of years and has reached a considerable level of maturity. The concept is generally conservative with very few risk items which are mitigated in various ways. |
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Slides MOYBA4 [5.466 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA4 | |
About • | paper received ※ 24 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019 | |
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MOYBA6 | Accelerator Performance During the Beam Energy Scan II at RHIC in 2019 | 26 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. RHIC provided Au-Au collisions at beam energies of 9.8, 7.3, 4.59 and 3.85 GeV/nucleon during the first year of the Beam Energy Scan II in 2019. The physics goals at the first two higher beam energies were achieved. At the two lower beam energies, bunched electron beam cooling has been demonstrated successfully. The accelerator performance was improved compared to when RHIC was operated at these energies in earlier years. This article will introduce the challenges to operate RHIC at low energies and the corresponding countermeasures, and review the improvement of accelerator performance during the operation in 2019. |
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Slides MOYBA6 [6.579 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-MOYBA6 | |
About • | paper received ※ 21 August 2019 paper accepted ※ 06 September 2019 issue date ※ 08 October 2019 | |
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TUZBB3 | Precise Beam Velocity Matching for the Experimental Demonstration of Ion Cooling With a Bunched Electron Beam | 356 |
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The first ever electron cooling based on the RF acceleration of electron bunches was experimentally demonstrated on April 5, 2019 at the Low Energy RHIC Electron Cooler (LEReC) at BNL. The critical step in obtaining successful cooling of the Au ion bunches in the RHIC cooling sections was the accurate matching of average longitudinal velocities of electron and ion beams corresponding to a relative error of less than 5·10-4 in the e-beam momentum. Since the electron beam kinetic energy is just 1.6 MeV, measuring the absolute e-beam energy with sufficient accuracy and eventually achieving the electron-ion velocity matching was a nontrivial task. In this paper we describe our experience with measuring and setting the e-beam energy at LEReC. | ||
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Slides TUZBB3 [1.340 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUZBB3 | |
About • | paper received ※ 26 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019 | |
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TUPLM11 | Beam-Beam Damping of the Ion Instability | 391 |
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Funding: Work Supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Beam-Beam damping of the Ion Instability The electron storage ring of the proposed electron ion collider at BNL has bunch charges as large as 50 nC and bunch spacings as small as 10 ns. For molecules like CO a dangerous buildup of positive ions is possible and a significant fraction of these ions can survive allowable clearing gaps. The instability is thus multi-turn and the weak damping required to stop the ion instabilty with an ideal clearing gap is ineffective here. The beam-beam force is highly nonlinear and a potent source of tune spread. Simulations employing several macro-particles per electron bunch and several ion macroparticles are used to estimate maximum gas densities for some common molecules. A simplified model is introduced and compared with simulations. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM11 | |
About • | paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019 | |
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TUPLM12 | Method for a Multiple Square Well Model to Study Transverse Mode Coupling Instability | 395 |
SUPLM18 | use link to see paper's listing under its alternate paper code | |
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In the high intensity limit it can become difficult to simulate intense beams sufficiently within a short time scale due to collective effects. Semi-Analytic methods such as the Square Well Model*/AirBag Square Well** (SWM/ABS) exist to estimate collective effects within a short time scale. SWM/ABS discretizes the longitudinal confining potential into a single square well enforcing linearity for the case of linear transverse optics. A method is proposed here to extend the Square Well Method multiple square wells. This method preserves linearity properties that make it easily solvable within a short time scale as well as including nonlinear effects from the longitudinal potential shape.
*M. Blaskiewicz PRSTAB 1, 044201. 1998 **A. Burov PRAB 22, 034202. 2019 |
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Poster TUPLM12 [1.818 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM12 | |
About • | paper received ※ 27 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019 | |
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TUPLM24 | Electron Heating by Ions in Cooling Rings | 426 |
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Hadron beam cooling at high energy is a critical technique for Electron-Ion Colliders (EIC). We consider using an electron storage ring for the EIC at BNL. For such a cooler, the electron beam quality plays an important role since it directly determines the cooling rate. Besides the effects of IBS, space charge and synchrotron damping, which are calculable with well known methods, the heating effect by ions also needs to be carefully considered in electron beam dynamics. In this paper, we present an analytical model to calculate the heating rate by ions and give some example calculations. In addition, this model was benchmarked by applying it on the IBS calculation.
* Work supported by States Department of Energy |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM24 | |
About • | paper received ※ 26 August 2019 paper accepted ※ 02 September 2019 issue date ※ 08 October 2019 | |
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TUPLM25 | Connecting Gas-Scattering Lifetime and Ion Instabilities | 430 |
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Recently there is a renewed interest in fast ion instability (FII) which is of concern for future low-emittance electron storage rings, such as MBA light sources and colliders, i.e. eRHIC. While analytical theories and numerical codes exist to model the effect, due to various assumptions and limitations, accurate experimental verification is often desirable. Unfortunately, one of the most critical parameters for FII (as well as the classical "trapped-ion" instability), the residual ion concentration, is usually the most uncertain. Vacuum gauges and residual gas analyzers (RGAs) provide some useful data, but they are often not accurate enough, and, more importantly, they cannot directly probe the ion concentration along the beam orbit. In this paper we show how one could use gas-scattering lifetime measurements to infer the residual gas concentration suitable for ion instability experiment modelling. | ||
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLM25 | |
About • | paper received ※ 21 September 2019 paper accepted ※ 19 November 2019 issue date ※ 08 October 2019 | |
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TUPLO03 | RHIC Beam Abort System Upgrade Options | 536 |
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Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH10886 with the U.S. Department of Energy. The RHIC ion (polarized proton) beam intensity has increased to 4x (1.1x) of the original design specifications. In 2013 proton beam currents overcame the eddy current reduction design features in the RHIC beam abort system kicker magnets causing ferrite heating and resulting in a reduction of the kicker strength. In 2014, the abort kicker ferrites were changed, the eddy current reduction design was upgraded, and an active ferrite cooling loop installed to prevent heating. For ions the beam dump vacuum window was changed from stainless steel to a titanium alloy and the adjacent beam diffuser block carbon material was changed to allow for higher ion intensities. A thicker beam pipe was installed to prevent secondaries from quenching the adjacent superconducting quadrupole. With these upgrades there is at least a factor 2 of safety margin for the demonstrated intensities to date. For a further increase in the intensity for RHIC and eRHIC we evaluate upgrade options for the beam abort system. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO03 | |
About • | paper received ※ 26 August 2019 paper accepted ※ 05 September 2019 issue date ※ 08 October 2019 | |
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TUPLO05 | Fixed Target Operation at RHIC in 2019 | 542 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. RHIC operated in fixed target mode at beam energies 4.59, 7.3, and 31.2 GeV/nucleon in 2019 as a part of the Beam Energy Scan II program. To scrape beam halo effectively at the fixed target which is 2.05 m away from the center of the STAR detectors, lattice design with relative large beta function at STAR was implemented at the two lower energies. The kickers of the base-band tune (BBQ) measurement system were engaged to dilute the beam transversely to maintain the event rate except for 31.2 GeV/nucleon. In addition, beam orbit control, tune and chromaticity adjustments were used to level the event rate. This paper will review the operational experience of RHIC in fixed target mode at various energies. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO05 | |
About • | paper received ※ 21 August 2019 paper accepted ※ 15 September 2019 issue date ※ 08 October 2019 | |
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TUPLO06 | Weak-Strong Beam-Beam Simulation for eRHIC | 545 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the eRHIC, to compensate the geometric luminosity loss due to the crossing angle, crab cavities are to be installed on both sides of the interaction point. When the proton bunch length is comparable to the wavelength of its crab cavities, protons will not be perfectly tilted in the x-z plane. In the article, we employ weak-strong beam-beam interaction model to calculate the proton beam size growth rates and luminosity degradation rate with various machine and time parameters. The goal of these studies is to optimize the the beam-beam related machine and beam parameters of eRHIC. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO06 | |
About • | paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019 | |
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TUPLO07 | Calculation of Action Diffusion With Crabbed Collision in eRHIC | 549 |
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Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. In the eRHIC, to compensate the geometric luminosity loss due to the crossing angle, crab cavities are to be installed on both sides of the interaction point. When the proton bunch length is comparable to the wavelength of its crab cavities, protons will not be perfectly tilted in the x-z plane. In the article, we develop a simulation code to calculate the transverse action diffusion rate as function of the initial proton longitudinal action. The goal of this study is to identify the contributions from various protons to the overall emittance growth. Tune scan is also performed to locate optimum working points which yield less proton emittance growth. |
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DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-TUPLO07 | |
About • | paper received ※ 29 August 2019 paper accepted ※ 03 September 2019 issue date ※ 08 October 2019 | |
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THZBA5 | First Electron Cooling of Hadron Beams Using a Bunched Electron Beam | 957 |
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Funding: Work supported by the U.S. Department of Energy. The Low Energy RHIC electron Cooler (LEReC) was recently constructed and commissioned at BNL. The LEReC is the first electron cooler based on the RF acceleration of electron bunches (previous electron coolers all used DC beams). Bunched electron beams are necessary for cooling hadron beams at high energies. The challenges of such an approach include generation of electron beams suitable for cooling, delivery of electron beams of the required quality to the cooling sections without degradation of beam emittances and energy spread, achieving required small angles between electrons and ions in the cooling sections, precise energy matching between the two beams, high-current operation of the electron accelerator, as well as several physics effects related to bunched beam cooling. Following successful commissioning of the electron accelerator in 2018, the focus of the LEReC project in 2019 was on establishing electron-ion interactions and demonstration of cooling process using electron energy of 1.6MeV (ion energy of 3.85GeV/n), which is the lowest energy of interest. Here we report on the first demonstration of Au ion cooling in RHIC using this new approach. |
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Slides THZBA5 [16.417 MB] | |
DOI • | reference for this paper ※ https://doi.org/10.18429/JACoW-NAPAC2019-THZBA5 | |
About • | paper received ※ 16 August 2019 paper accepted ※ 31 August 2019 issue date ※ 08 October 2019 | |
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