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MOPAN081 | The LHC Collimator Controls Architecture - Design and Beam Tests | controls, beam-losses, survey, injection | 344 | |||||
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The LHC collimation system will require simultaneous management by the LHC control system of more than 500 jaw positioning mechanisms in order to ensure the required beam cleaning and machine protection performance in all machine phases, from injection at 450~GeV to collision at 7~TeV. Each jaw position is a critical parameter for the machine safety which could cause a beam dump. In this paper, the architecture of the LHC collimator controls is presented. The basic design to face the accurate and real-time control of the LHC collimators and the interfaces to the other components of LHC Software Application and control infrastructures are described. The full controls architecture has been tested off-line in dedicated test benches, and in the real accelerator environment in the CERN SPS during beam tests with a full scale collimator prototype. The results and the lessons learned are presented.
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TUOBKI01 | Experimental Characterization of the Spallation Neutron Source Accumulator Ring Collimation System | beam-losses, simulation, quadrupole, emittance | 703 | |||||
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Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract DE-AC05-00OR22725. |
The SNS ring and associated transport lines, commissioned in January 2006, are designed to accumulate and deliver up to 1.5·1014, 1 GeV protons at 60 Hz to a liquid mercury target for neutron production. In order to control activation and to allow for routine hands-on maintenance of accelerator components, beam loss in most of the ring must remain below 1 W/m . For the full 1.4 MW beam, this translates to a fractional beam loss limit of 0.01%. Accomplishing this loss limit at full beam power will require successful utilization of the ring's two-stage betatron collimation system. In this paper we present the results of initial collimation experiments. We characterize the collimation-induced beam-loss pattern and compare our results with simulations. In addition, we discuss other existing beam-loss-related challenges in the ring. |
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TUODKI06 | Observation of Proton Reflection on Bent Silicon Crystals at the CERN SPS | proton, scattering, collider, hadron | 751 | |||||
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Funding: INTAS-CERN, contract number 05-96-7525 and CARE, contract number RII3-CT-2003-506395. |
We report observations, performed by the H8-RD22 Collaboration*, of the so-called volume reflection effect with 400 GeV/c protons interacting with bent Silicon crystals in the H8 beam line at the CERN SPS. The volume reflection is closely related with particle channeling. This phenomenon occurs at the tangency point of a particle trajectory with the bent crystalline planes and consists in the reversal of the transverse component of the particle momentum. The measurements were collected with a high spatial resolution detector mainly based on Silicon strips. The proton beam was deviated in the direction opposite to that of channeling by ~12μrad, which is ~1.3 times the critical angle, with an efficiency larger than 97% in a range of the proton-to-crystal incident angle as large as the bending angle of crystallographic planes. This evidence opens new perspectives for manipulation of high-energy beams, e.g., for collimation and extraction in the new-generation of hadron colliders or as a method for high-energy experiments in the region near to the circulating beam.
* H8-RD22 collaboration: CERN, FNAL, INFN (Ferrara, Legnaro, Perugia, Roma, Milano, Trieste), IHEP, PNPI, JINR |
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TUPAN051 | Design of Dynamic Collimator for J-PARC Main Ring | target, extraction, beam-losses, injection | 1505 | |||||
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The J-PARC main ring has a beam collimator section downstream of the injection area. The allowed beam loss is about 500 W. The beam halo during injection can be scraped by a standard collimator scheme. The beam halo can grow during the acceleration. Such a halo may cause a serious beam loss for extracted beam. A collimation during acceleration (dynamic collimator) is usefull to reduce the uncontrolable beam loss at the extraction. We will report the design and simulation of the dynamic collimation.
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TUPAN085 | LHC Impedance Reduction by Nonlinear Collimation | impedance, insertion, betatron, damping | 1571 | |||||
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A nonlinear collimation system can allow larger aperture for the mechanical jaws, and it thereby can help to reduce the collimator impedance, which presently limits the LHC beam intensity. Assuming the nominal LHC beam at 7 TeV, we show how a nonlinear betatronic collimation insertion would reduce considerably the LHC coherent tune shift for the most critical coupled-bunch mode as compared with the conventional baseline linear collimation system of Phase-I. In either case, the tune shifts of the most unstable modes are compared with the stability diagrams for Landau damping.
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TUPAN087 | Scenarios for Beam Commissioning of the LHC Collimation System | optics, proton, injection, simulation | 1577 | |||||
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A complex system of collimators has been designed to protect the superconducting LHC magnets against quench and damage from the high intensity proton beams. The considerable number of collimators and the resulting number of degrees of freedom for their set-up requires a well prepared commissioning strategy. Efficiency studies for various implementations of the LHC collimation system have been performed, taking into account the evolution in optics and beam intensity according to the LHC commissioning schedule. This paper explains the present plans for the set-up sequence of collimators and discusses the relevant tolerances induced from the collimation system for the first years of the LHC operation.
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TUPAN100 | Performance Reach of the | proton, injection, insertion, simulation | 1613 | |||||
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State-of-the-art tracking tools have been developed for detailed LHC collimation and beam loss studies. This includes full chromatic treatment of both beam lines and error models. This paper reviews the main results on the performance reach of the multi-stage LHC collimation system that is being installed in the LHC. Limitations on the allowed proton loss rates and the stored intensity can be derived from the comparison of local losses with estimated quench limits for the superconducting magnets. The origins of the cleaning-related performance limitations are presented and possible improvements are discussed.
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TUPAN107 | Beam Loss Response Measurements with an LHC Prototype Collimator in the SPS | beam-losses, controls, alignment, impedance | 1622 | |||||
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Beam tests with an LHC prototype collimator were performed at the SPS in autumn 2006. Applying a new collimator control system many new beam measurements were performed. This contribution presents results on collimator-induced beam loss measurements and their applications to beam-based alignment of collimators and measurements of the beam size and position. Interesting features of the recorded beam loss signals are illustrated and possible impacts for LHC operation are discussed. The measured loss distributions around the full SPS ring are analyzed and compared with simulations.
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TUPAN108 | LHC Collimation System Hardware Commissioning | vacuum, alignment, collider, proton | 1625 | |||||
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The stored energy and intensity of the LHC beam exceed the damage level of the machine and the quench level of the magnets by far. Therefore a robust and reliable collimation system is required which prevents the quenching of the magnets during regular operation and protects the accelerator components from damage in the event of beam loss. To assure that the installed collimators will protect the machine and permit the required performance of the collider, an appropriate hardware commissioning has to be implemented. In this contribution we describe the procedures for the hardware commissioning of the LHC collimation system. These procedures will establish the required precision and reliability of collimator movements and settings before the start of beam operation.
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TUPAS010 | Studies of Beam Properties and Main Injector Loss Control using Collimators in the Fermilab Booster to Main Injector Transfer Line | booster, proton, beam-losses, radiation | 1670 | |||||
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Funding: Work supported by the U. S. Department of Energy under Contract No. DE-AC02-76CH03000. |
High intensity operation of the Fermilab Main Injector has resulted in increased activation of machine components. Efforts to permit operation at high power include creation of collimation systems to localize losses away from locations which require maintenance. As a first step, a collimation system to remove halo from the incoming beam was installed in the Spring 2006 Facility Shutdown*. We report on commissioning studies and operational experience including observations of Booster beam properties, effects on Main Injector loss and activation, and operational results.
* B. C. Brown, et al., "Collimation System for the Fermilab Booster to Main Injector Transfer Line", this conference. |
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TUPAS011 | Collimation System for the Fermilab Booster to Main Injector Transfer Line | booster, controls, radiation, vacuum | 1673 | |||||
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Funding: Work supported by the U. S. Department of Energy under Contract No. DE-AC02-76CH03000. |
A collimation system has been created for removing proton beam halo in the 8 GeV transfer line from the Fermilab Booster to Main Injector. A pair of 1.14 meter collimators with 5.08 cm rectangular apertures are installed in a 5 meter straight section. Horizontal and vertical motion systems allow them to be positioned such that halo can be scraped from four sides. An additional pair of collimators, placed one cell (90 degrees) downstream scrape halo which is of opposite phase. Each collimator pair can scrape about 600 Watts of beam power, limited by long term activation of materials outside of the beam line tunnel. Personnel exposure is reduced by surrounding the iron absorber with a layer of marble. Design features,radiation calculations and instrumentation considerations will be described. |
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TUPAS012 | Start-to-End Simulations for the Proposed Fermilab High Intensity Proton Source | simulation, quadrupole, emittance, lattice | 1676 | |||||
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A High Intensity Proton Source consisting in an 8 GeV superconducting H-minus linac and transfer line to the Main Injector has been proposed. The primary mission is to increase the intensity of the Fermilab Main Injector for the production of neutrino superbeams. Start-to-end simulations from the RFQ to the stripping foil using the simulation code TRACK (ANL) will be presented in this paper. In particular, we will study the impact of errors (jitters and alignments) on the H- phase space at the entrance of the stripping foil.
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TUPAS016 | Collimation System Design for Beam Loss Localization with Slipstacking Injection in the Fermilab Main Injector | injection, beam-losses, simulation, proton | 1688 | |||||
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Results of modeling with the STRUCT and MARS15 codes of beam loss localization and related radiation effects are presented for the slipstacking injection to the Fermilab Main Injector. Simulations of proton beam loss are done using multi-turn tracking with realistic accelerator apertures, nonlinear fields in the accelerator magnets and time function of the RF manipulations to explain the results of beam loss measurements. The collimation system consists of one primary and four secondary collimators. It intercepts a beam power of 1.6 kW at a total scraping rate of 5%, with a beam loss rate in the ring outside the collimation region of 1 W/m or less. Based on thorough energy deposition and radiation modeling, a corresponding collimator design was developed that satisfies all the radiation and engineering constraints.
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TUPAS019 | A Dynamic Dispersion Insert for the Fermilab Main Injector for Momentum Collimation | lattice, closed-orbit, beam-losses, collider | 1697 | |||||
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The Fermilab Main Injector accelerator is designed as a FODO lattice with zero dispersion straight sections. A scheme will be presented that can dynamically alter the dispersion of one of the long straight sections to create a non-zero dispersion straight section suitable for momentum collimation. During the process of slip stacking DC beam is generated which is lost during the first few milliseconds of the ramp. A stationary massive primary collimator/absorber with optional secondary masks could be utilized to isolate beam loss due to uncaptured beam.
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TUPAS106 | Observation of Experimental Background in RHIC Polarized Proton Run 2006 | background, proton, vacuum, interaction-region | 1883 | |||||
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Funding: * Work supported by U. S. DOE under contract No DE-AC02-98CH1-886 |
There are three main sources of the experimental background at RHIC. The beam-gas induced background is associated with the vacuum pressure, the beam-chamber-interaction induced background can be improved by collimations, and the beam-beam induced background is somewhat inherent, and probably harmless for the experimental data taking. The zero degree calorimeter (ZDC) is an essential luminosity detector for heavy ion operations in RHIC. It is shown that, however, the ratio of ZDC singles (background) and coincident rate is also useful in proton runs for background evaluations. In this article, the experimental background problem in RHIC polarized proton runs is reported. |
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WEOCAB01 | Design of the Beam Delivery System for the International Linear Collider | linac, extraction, diagnostics, betatron | 1985 | |||||
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The beam delivery system for the linear collider focuses beams to nanometer sizes at the interaction point, collimates the beam halo to provide acceptable background in the detector and has a provision for state-of-the art beam instrumentation in order to reach the physics goals. The beam delivery system of the International Linear Collider has undergone several configuration changes recently. This paper describes the design details and status of the baseline configuration considered for the reference design.
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WEOAC03 | Transverse Impedance of LHC Collimators | impedance, injection, octupole, insertion | 2003 | |||||
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The transverse impedance in the LHC is expected to be dominated by the numerous collimators, most of which are made of Fibre-Reinforced-Carbon to withstand the impacts of high intensity proton beams in case of failures, and which will be moved very close to the beam, with full gaps of few millimetres, in order to protect surrounding super-conducting equipments. We present an estimate of the transverse resistive-wall impedance of the LHC collimators, the total impedance in the LHC at injection and top energy, the induced coupled-bunch growth rates and tune shifts, and finally the result of the comparison of the theoretical predictions with measurements performed in 2004 and 2006 on a prototype collimator installed in the SPS.
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THPMN005 | Technical Challenges for Head-On Collisions and Extraction at the ILC | extraction, quadrupole, luminosity, optics | 2716 | |||||
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Funding: EUROTeV Project Contract no.011899 RIDS |
An interaction region with head-on collisions is considered as an alternative to the baseline ILC configuration. Progress in the final focus optics design includes engineered large bore superconducting final doublet magnets and their 3D magnetic integration in the detector solenoids. Progress on the beam separation optics is based on technical designs of electrostatic separator and special extraction quadripoles. The spent beam extraction is realized by a staged collimation scheme relying on realistic collimators. The impact on the detector background is estimated. The possibility of technical tests of the most challenging components is investigated. |
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THPMN065 | Laser Collimation for Linear Colliders | laser, electron, linear-collider, collider | 2856 | |||||
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We explore the possibility of laser-based postlinac beam collimation in future linear colliders. A laser employed as a spoiler can neither be 'destroyed' by the beam impact and nor generate collimator wake fields. In addition, the postlinac collimation section, presently the longest part of linear-collider beam delivery systems, can be shortened. In this paper, we investigate different types of laser modes for use as spoiler. Suitable laser beam parameters and modes are discussed for collimation in both CLIC and ILC.
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THPMN073 | Collimation Optimisation in the Beam Delivery System of the International Linear Collider | lattice, luminosity, betatron, quadrupole | 2871 | |||||
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The collimation systems of the International Linear Collider (ILC) Beam Delivery System (BDS) must perform efficient removal of halo particles which lie outside the acceptable ranges of energy and spatial spread. An optimisation strategy based on earlier work is applied to the latest version of the BDS lattice. The resulting improvement in collimation performance is studied by halo tracking simulations, and the luminosity performance of the optimised lattice is also examined.
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THPAN065 | Beam Loss Map Simulations and Measurements in the CERN PS | beam-losses, simulation, septum, extraction | 3372 | |||||
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Numerical tools providing detailed beam loss maps, recently developed for the design of the LHC collimation system, were adapted to the CERN Proton Synchrotron in order to reproduce the observed beam loss patterns. Using a MADX optics sequence model, these tools are able to track a large number of particles with Sixtrack and interact with a realistic aperture model to simulate particle losses all around the ring. The modeled loss maps were finally compared with beam loss measurements at several energies and for a variety of beams accelerated in the synchrotron.
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THPAN072 | A Concept for the LHC Luminosity Upgrade Based on Strong Beta* Reduction Combined with a Minimized Geometrical Luminosity Loss Factor | luminosity, separation-scheme, quadrupole, dipole | 3387 | |||||
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A significant increase of the LHC beam current touches physics limits as collective effects, electron-cloud, heat load, collimation and machine protection. We propose an upgrade scheme mainly based on a stronger focusing, with a beta* of 10 cm, requiring a triplet quadrupole aperture of around 130 mm. The performance is further improved if the triplet is based on the Nb3Sn technology. In the present baseline, this beta* reduction provides a negligible luminosity increase: this approach requires a drastic action to minimize the crossing angle, while the beam separation at the long-range encounters has to be increased. This is provided by an early separation scheme made of small dipoles inside the detectors. Optionally, a small angle crab cavity scheme may totally suppress the residual crossing angle. The quadrupole aperture is calculated to allow a larger gap for the collimator, suppressing their impedance limitation. This concept offers high performance while significantly reducing the risks associated to a beam current increase; it opens as well new issues that deserve further studies, such as the dipole integration in the detector, and the correction of the triplet aberrations.
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THPAN081 | Collimator Wakefields: Formulae and Simulation | simulation, damping, electromagnetic-fields | 3405 | |||||
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The effect of a leading particle on a trailing particle due to resistive and geometric wakefields in collimators can be described by expanding in a series of angular mode potentials Wm(s). Several formulae for these are given in the literature. We compare these formulae with numerical predictions from codes that solve the EM field equations, and explore the claimed regions of validity. We also explore how the EM code results can be used to numerically obtain angular mode potentials suitable for use in tracking codes.
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THPAS039 | Status Report on the NSCL RF Fragment Separator | kicker, cyclotron, ion, secondary-beams | 3585 | |||||
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The RF Fragment Separator (RFFS) proposed in* is now under construction and should be operational by May 2007. The RFFS is an additional purification system for secondary beams at the National Superconducting Cyclotron Laboratory after the existing A1900 fragment separator and will primarily be used to purify beams of rare neutron deficient isotopes. The RFFS uses a transverse electric field of an rf kicker to separate unwanted particles from the desired ion beam, a pi/2 phase advance cell to rotate the beam in phase space before the beam reaches a collimating aperture for purification and a final pi phase advance cell to transport the desired beam to the experiment. The final design for the rf kicker and the focusing system is presented and a status report on the building and commissioning effort is given.
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* D. Gorelov, V. Andreev, D. Bazin, M. Doleans, T. Grimm, F. Marti, J. Vincent and X. Wu, "RF-Kicker System for Secondary Beams at NSCL/MSU" PAC2005, Knoxville, Tennessee, 16th-20th, May 2005 |
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