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| MPPE030 | Comparison of Off-Line IR Bump and Action-Angle Kick Minimization | 2116 |
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Funding: Work supported by U.S. DOE under contract No. DE-AC02-98CH10886. The interaction region bump (IR bump) nonlinear correction method has been used for the sextupole and octupole field error on-line corrections in the Relativistic Heavy Ion Collider (RHIC). Some differences were found for the sextupole and octupole corrector strengths between the on-line IR bump correction and the predictions from the action-angle kick minimization. In this report we compare the corrector strengths from these two methods based on the RHIC Blue ring lattice with the IR nonlinear modeling. The comparison confirms the differences between resulting corrector strengths. And the reason for the differences is found and discussed. It is followed by a further discussion of the operational IR bump applications to the octupole, and skew sextupole and skew quadrupole field error corrections. |
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| MPPT071 | The Lambertson Septum Magnet of the Spallation Neutron Source | 3847 |
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Funding: Work performed under contract for SNS, managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. In the Spallation Neutron Source, at Oak Ridge National Laboratory in Tennessee, multiple-stage injections to an accumulator ring increase intensity until a final extraction delivers the full proton beam to the target via transfer line. This extraction is achieved by a series of kicker elements and a thin septum Extraction Lambertson Septum Magnet. Here we discuss the lattice geometry, beam dynamics and optics, and the vacuum, electromagnetic and electromechanical design aspects of the SNS Extraction Lambertson Septum Magnet. Relevant datums are established. Beam optics is studied. Vector calculus is solved for pitch and roll angles. Fundamental magnet sections are depicted schematically. Coil, pole and yoke design calculations and electromagnetics optimization are presented. |
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| MPPT070 | Construction and Power Test of the Extraction Kicker Magnet for the Spallation Neutron Source Accumulator Ring | 3831 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. Two extraction kicker magnet assemblies that contain seven individual pulsed magnet modules each will kick the proton beam vertically out of the SNS accumulator ring into the aperture of the extraction lambertson septum magnet. The proton beam then travels to the 1.4 MW SNS target assembly. The 14 kicker magnets and major components of the kicker assembly have been fabricated in BNL. The inner surfaces of the kicker magnets were coated with TiN to reduce the secondary electron yield. All 14 PFN power supplies have been built, tested and delivered to ORNL. Before final installation, a partial assembly of the kicker system with three kicker magnets was assembled to test the functions of each critical component in the system. In this paper we report the progress of the construction of the kicker components, the TiN coating of the magnets, the installation procedure of the magnets and the full power test of the kicker with the PFN power supply. |
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| TPAT081 | Observation of Electron-Ion Effects at RHIC Transition | 4087 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. Electron cloud is found to be a serious obstacle on the upgrade path of the Relativistic Heavy Ion Collider (RHIC). At twice the design number of bunches, electron-ion interactions cause significant instability, emittance growth, and beam loss along with vacuum pressure rises when the beam is accelerated across the transition. |
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| TPAT082 | Phonon Modes and the Maintenance Condition of a Crystalline Beam | 4111 |
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Funding: * Work performed under the auspices of the U.S. Department of Energy. Previously it has been shown that the maintenance condition for a crystalline beam requires that there not be a resonance between the crystal phonon frequencies and the frequency associated with a beam moving through a lattice of N periods. This resonance can be avoided provided the phonon frequencies are all below half of the lattice frequency. Here we make a detailed study of the phonon modes of a crystalline beam. Analytic results obtained in a “smooth approximation” using the ground-state crystalline beam structure is compared with numerical evaluation employing Fourier transform of Molecular Dynamic (MD) modes. The MD also determines when a crystalline beam is stable. The maintenance condition, when combined with either the simple analytic theory or the numerical evaluation of phonon modes, is shown to be in excellent agreement with the MD calculations of crystal stability. [1] X-P. Li, A. M. Sessler, J. Wei, EPAC (1994) p. 1379 - 1381. ‘Necessary Conditions for Attaining a Crystalline Beam''}[2] J. Wei, H. Okamoto, A.M. Sessler, Phys. Rev. Lett., Vol. 80, p. 2606-2609 (1998). |
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| TPAT096 | Focusing-Free Transition Crossing in RHIC using Induction Acceleration | 4314 |
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Focusing-free transition crossing (FFTC) in RHIC is proposed. The original idea of FFTC proposed by J.Griffin was tried in the FNAL 500GeV main ring, where a gradient in the acceleration voltage was smoothed flat by introducing multi higher-harmonic RF. If the longitudinal focusing disappears during a limited time period near TC, various undesired features, such as bunch shortening and elongation in the momentum space, should be mitigated. In present RHIC operation, the slow ramping across transition leads into complications of nonlinear chromatic effects, vacuum pressure rise, instability, and transition-jump related lattice distortions. Recently, induction acceleration of a single RF bunch has been successfully demonstrated in KEK-PS,* where a proton bunch is trapped by the existing RF and accelerated with an induction step-voltage to 8 GeV. The utilized acceleration device is capable of generating a step voltage of 2 kV/cell at most at an arbitrary repetition rate up to 1 MHz. We here propose focusing-free TC in RHIC, introducing similar devices. In this scheme, the RF voltage is tuned off during an optimized time-period of several tens of ms, and the required acceleration voltage is provided as an induction flat-voltage.
*K.Takayama et al., submitted to Phys. Rev. Lett., http://www.arxiv.org/pdf/physics/0412006. |
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| TPPE007 | Energy Correction for High Power Proton/H Minus Linac Injectors | 1075 |
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| High-energy proton/H minus (> GeV) linear accelerators suffer from energy jitter due to RF amplitude and phase stability. For high-power operations, such energy jitter often results in beam losses at more than 1 W/m level required for hands-on maintenance. Depending upon the requirements for next accelerator in the chain, this energy jitter may or may not require correction. This paper discusses the sources of energy jitter and correction feasibility with specific examples of the Spallation Neutron Source linac and a higher-energy H minus linac. | ||
| WPAE035 | SNS Ring Injection Stripped Electron Collection: Design Analysis and Technical Issues | 2384 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. This paper describes the simulation studies on the motions of stripped electrons generated in the injection section of the Spallation Neutron Source (SNS) accumulator ring and the effective collection mechanism. Such studies are important for high intensity machines, in order to reduce beam loss and protect other components in the vicinity. The magnetic field is applied to guide electrons to a collector, which is located at the bottom of the beam chamber. Part of the study results with and without considering the interactions between electrons and materials are presented and discussed. The final engineering design of the electron collector (catcher) is also presented and described. |
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| TPAP043 | Electron Cooling of RHIC | 2741 |
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We report progress on the R&D program for electron-cooling of the Relativistic Heavy Ion Collider (RHIC). This electron cooler is designed to cool 100 GeV/nucleon at storage energy using 54 MeV electrons. The electron source will be a superconducting RF photocathode gun. The accelerator will be a superconducting energy recovery linac. The frequency of the accelerator is set at 703.75 MHz. The maximum electron bunch frequency is 9.38 MHz, with bunch charge of 20 nC. The R&D program has the following components: The photoinjector and its photocathode, the superconducting linac cavity, start-to-end beam dynamics with magnetized electrons, electron cooling calculations including benchmarking experiments and development of a large superconducting solenoid. The photoinjector and linac cavity are being incorporated into an energy recovery linac aimed at demonstrating ampere class current at about 20 MeV. A Zeroth Order Design Report is in an advanced draft state, and can be found on the web at http://www.agsrhichome.bnl.gov/eCool/.
Under contract with the U.S. Department of Energy, Contract Number DE-AC02-98CH10886. |
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| TPAT095 | Beam Induced Pressure Rise at RHIC | 4308 |
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Beam induced pressure rise in RHIC warm sections is currently one of the machine intensity and luminosity limits. This pressure rise is mainly due to electron cloud effects. The RHIC warm section electron cloud is associated with longer bunch spacings compared with other machines, and is distributed non-uniformly around the ring. In addition to the countermeasures for normal electron cloud, such as the NEG coated pipe, solenoids, beam scrubbing, bunch gaps, and larger bunch spacing, other studies and beam tests toward the understanding and counteracting RHIC warm electron cloud are of interest. These include the ion desorption studies and the test of anti-grazing ridges. For high bunch intensities and the shortest bunch spacings, pressure rises at certain locations in the cryogenic region have been observed during the past two runs. Beam studies are planned for the current 2005 run and the results will be reported.
Work performed under the auspices of the US Department of Energy. |
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| ROPB003 | Electron Cloud Dynamics in High-Intensity Rings | 245 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. Electron cloud due to beam induced multipacting is one of the main concerns for the high intensity rings because the electron multipacting becomes stronger with the increment of beam intensity. Electrons generated and accumulated inside the beam pipe form an "electron cloud" that interacts with the circulating charged particle beam. With sizeable amount of electrons, this interaction can cause beam instability, beam loss and emittance growth. At the same time, the vacuum pressure will rise due to electron desorption. This talk intends to provide an overview of the dynamics of the typical electron multipacting in various magnetic fields and mitigation measures in both long bunch and short bunch rings. |
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| RPPE048 | Physical and Electromagnetic Properties of Customized Coatings for SNS Injection Ceramic Chambers and Extraction Ferrite Kickers | 3028 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. The inner surfaces of the 248 m SNS accumulator ring vacuum chambers are coated with ~100 nm of titanium nitride (TiN) to reduce the secondary electron yield (SEY) of the chamber walls. All the ring inner surfaces are made of stainless or inconel, except those of the injection and extraction kickers. Ceramic vacuum chambers are used for the 8 injection kickers to avoid shielding of a fast-changing kicker field and to reduce eddy current heating. The internal diameter was coated with Cu to reduce the beam coupling impedance and provide passage for beam image current, and a TiN overlayer to reduce SEY. The ferrite surfaces of the 14 extraction kicker modules were coated with TiN to reduce SEY. Customized masks were used to produce coating strips of 1 cm x 5 cm with 1 to 1.5 mm separation among the strips. The masks maximized the coated area to more than 80%, while minimizing the eddy current effect to the kicker rise time. The coating method, as well as the physical and electromagnetic properties of the coatings for both types of kickers will be summarized, with emphasis on the effect to the beam and the electron cloud buildup. †Corresponding author email: hseuh@bnl.gov. |
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| RPPT065 | Beam Loss Estimates and Control for the BNL Neutrino Facility | 3647 |
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Funding: This work is performed under the auspices of the US DOE. BNL plans to upgrade the AGS proton beam from the current 0.14 MW to higher than 1.0 MW for a very long baseline neutrino oscillation experiment. This increase in beam power is mainly due to the faster repetition rate of the AGS by a new 1.5 GeV superconductiong linac as injector, replacing the existing booster. The requirement for low beam loss is very important both to protect the beam component, and to make the hands-on maintenance possible. In this report, the design considerations for achieving high intensity and low loss will be presented. We start by specifying the beam loss limit at every physical process followed by the proper design and parameters for realising the required goals. The process considered in this paper include the emittance growth in the linac, the H- injection, the transition crossing, the ecectron cloud effect, the coherent instabilities, and the extraction losses. Collimation and shielding are also presented. |
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| FPAE016 | Spallation Neutron Source Ring - Design and Construction Summary | 1499 |
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Funding: * SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. (J. Wei for the Spallation Neutron Source Collaboration) After six years, the construction of the Spallation Neutron Source (SNS) accumulator ring [1] and the transport lines is completed in March 2005. Designed to deliver 1.5 MW beam power (1.5 x 1014 protons of 1 GeV kinetic energy at a repetition rate of 60 Hz), stringent measures have been implemented in the fabrication, test, and assembly to ensure the quality of the accelerator systems. This paper summarizes the construction of the ring and transport systems with emphasis on the challenging technical issues and their solutions [2]. [1] J. Wei, et al, Phys. Rev. ST-AB, Vol. 3, 080101 (2000). [2] J. Wei, "Synchrotrons and Accumulators for High-Intensity Proton Beams", Rev. Mod. Phys., Vol. 75, 1383 – 1432 (2003). |
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| FPAP024 | Electron Cloud in the Collimator- and Injection- Region of the Spallation Neutron Source's Accumulator Ring | 1865 |
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Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy. SNS is a partnership of six national laboratories: Argonne, Brookhaven, Jefferson, Lawrence Berkeley, Los Alamos, and Oak Ridge. The beam loss along the Spallation Neutron Source’s (SNS’s) accumulator ring is mainly located at the collimator region. From the ORBIT simulation, the peak power deposition at the three collimators is about 500, 350 and 240 W/m, respectively. Therefore, a sizeable number of electrons may be accumulated at this region due to the great beam loss. This paper simulated the electron cloud at the collimator region and the possible remedy. |
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| FPAT003 | Joining the RHIC Online and Offline Models | 880 |
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Funding: Work performed under the auspices of the U.S. Department of Energy. The paper presents an interface encompassing the RHIC online ramp model and the UAL offline simulation framework. The resulting consolidated facility aims to minimize the gap between design and operational data, and to facilitate analysis of RHIC performance and future upgrades in an operational context. The interface is based on the Accelerator Description Exchange Format (ADXF), and represents a snapshot of the RHIC online model which is in turn driven by machine setpoints. This approach is also considered as an intermediate step towards integrating the AGS and RHIC modeling environments to produce a unified online and offline AGS model for operations. |