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MOOCH01 | Beam Based Alignment at the KEK-ATF Damping Ring | simulation, damping, emittance, synchrotron | 36 | ||||||
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The damping rings for a future linear collider will have demanding alignment and stability requirements in order to achieve the low vertical emittance necessary for high luminosity. The Accelerator Test Facility (ATF) at KEK has successfully demonstrated the <5 pm vertical emittance specified for the GLC/NLC Main Damping Rings [*]. One contribution to this accomplishment has been the use of Beam Based Alignment (BBA) techniques. The mode of operation of the ATF presents particular challenges for BBA, and we describe here how we have deduced the offsets of the BPMs with respect to the quadrupoles. We also discuss a technique that allows for direct measurements of the beam-to-quad offsets.
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* "Extremely Low Vertical-Emittance Beam in the Accelerator Test Facility at KEK", K. Kubo, et al., Phys.Rev.Lett.88:194801,2002 |
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Video of talk
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MOOCH02 | First Full Beam Loading Operation with the CTF3 Linac | simulation, acceleration, emittance, linac | 39 | ||||||
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The aim of the CLIC Study is to investigate the feasibility of a high luminosity, multi-TeV linear e+e- collider. CLIC is based on a two-beam method, in which a high current drive beam is decelerated to produce 30 GHz RF power needed for high-gradient acceleration of the main beam running parallel to it. To demonstrate the outstanding feasibility issues of the scheme a new CLIC Test Facility, CTF3, is being constructed at CERN by an international collaboration. In its final configuration CTF3 will consist of a 150 MeV drive beam linac followed by a 42 m long delay loop and an 84 m combiner ring. The installation will include a 30 GHz high power test stand, a representative CLIC module and a test decelerator. The first part of the linac was installed and commissioned with beam in 2003. The first issue addressed was the generation and acceleration of a high-current drive beam in the "full beam loading" condition where RF power is converted into beam power with an efficiency of more than 90%. The full beam loading operation was successfully demonstrated with the nominal beam current of 3.5 A. A variety of beam measurements have been performed, showing good agreement with expectations.
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Video of talk
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MOOCH03 | Status of a Linac RF Unit Demonstration for the NLC/GLC X-band Linear Collider | simulation, acceleration, emittance, damping | 42 | ||||||
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Designs for a future TeV scale electron-positron X-band linear collider (NLC/GLC) require main linac units which produce and deliver 450 MW of rf power at 11.424 GHz to eight 60 cm accelerator structures. The design of this rf unit includes a SLED-II pulse compression system with a gain of approximately three at a compression ratio of four, followed by an overmoded transmission and distribution system. We have designed, constructed, and operated such a system as part of the 8-Pack project at SLAC. Four 50 MW X-band klystrons, running off a common 400 kV solid-state modulator, drive a dual-moded SLED-II pulse compression system. The compressed power is delivered to structures in the NLCTA beamline. Four 60 cm accelerator structures are currently installed and powered, with four additional structures and associated high power components available for installation late in 2004. We describe the layout of our system and the various high-power components which comprise it. We also present preliminary data on the processing and initial high-power operation of this system.
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MOPKF003 | Design of 2 T Wiggler Vacuum Chamber for the LNLS Storage Ring | acceleration, emittance, damping, simulation | 300 | ||||||
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A 2 T wiggler with 2.8 m long and a gap of 22 mm will be installed at LNLS storage ring. The main requirements of the chamber design are short conditioning time and low mechanical deformation. Two different designs in stainless steel are proposed for the prototypes, an elliptical tube and a machined sheet. A pressure profile simulation with and without a NEG coating were made for evaluating the life-time influence and the time necessary for conditioning. A simulation with finite element of mechanical deformation for both case show equivalent results. The first prototype was made with the elliptical tube and a NEG coating deposition will be made at ESRF. The second prototype with machined parts is under construction and will be TIG welded. Descriptions of mounting structure for the prototype are show and the evaluation the dimension tolerance of the chambers.
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MOPKF004 | Magnet Sorting Algorithm Applied to the LNLS EPU | acceleration, undulator, emittance, damping | 303 | ||||||
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The Brazilian Synchrotron Light Laboratory is about to begin the construction of the first Undulator for its 1.37 GeV electron storage ring. This device will be of the EPU type with a period of 50 milimeters and 22 milimeters minimum magnetic gap. In this work we report on the sorting algorithm applied in the construction of a 10-period undulator prototype.
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MOPKF005 | Preliminary Results on a Low Emittance Gun Based on Field Emission | emittance, electron, undulator, damping | 306 | ||||||
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The development of a new electron gun with the lowest possible emittance would help reducing the total length and cost of a free electron laser. Recent progresses in vacuum nanoelectronics make field emitter arrays (FEAs) an attractive technology to explore for high brightness sources. Indeed, several thousands of microscopic tips can be deposited on a 1 mm diameter area. Electrons are then extracted by a first grid layer close to tip apex and focused by a second grid layer one micrometer above the tip apex. The typical aperture diameter of this focusing layer is also in the range of one micrometer. The big challenge with FEA, is to achieve good emission homogeneity, we hope to achieve this with diverse conditioning techniques. However if we can achieve a low emittance with FEAs another challenge will be to preserve the emittance during the beam acceleration.
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MOPKF006 | Enhancements of Top-up Operation at the Swiss Light Source | emittance, linac, electron, undulator | 309 | ||||||
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Since the first experience on 2001, Top-Up is the standard mode of operation at the Swiss Light Source (SLS) for users. In order to fulfill the ongoing demands of machine experts and experiments we have had to add more functionality to the Top-Up mode thus make it more flexible. Some time-resolved experiments require a constant charge in a single isolated bucket in the gap of the normal filling of a bunch train of 80% of the circumference of the storage ring. Therefore the Hybrid application was developed that keeps the beam current distribution constant in this mode. We developed a maintenance mode too, to allow to work continuously on the Linac and booster - for example to optimize injection/extraction - without disturbing the Top-up for user operation. Even beam destructive experiments at the Linac during Top-Up or Hybrid operation are supported, where the Linac can be used synchronously at the times between successive refilling of the storage ring. The flexible control and timing systems at the SLS made these applications feasible. We describe the controls, operation and applications of each of the above functionalities in this paper.
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MOPKF008 | The BESSY Soft X-ray FEL User Facility | emittance, electron, undulator, damping | 312 | ||||||
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A FEL User Facility for the VUV to soft X-ray spectral range is planned at the BESSY site based on a cascaded HGHG-FEL scheme. Simultaneous operation of 3 - later 5 - FELs fed by a superconducting 2.3 GeV CW linac generates most flexible pulse structures for experiments, while the seeding scheme utilizing Ti:Sa fs-lasers results in ultrashort reproducible circular polarized FEL pulses on a shot to shot basis at a pulse-duration < 20 fs. Peak brilliances in the 1·1031 ph/(s mm2 mrad2 0.1% bw)-regime are feasible. All necessary hardware for the FEL is within existing technology. Future upgrade options, e.g. a superconducting photoinjector, seeding with short wavelength HHG lasers of about 1 fs pulse duration have been considered. A status on the design aspects is given.
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MOPKF009 | Photoinjector Studies for the BESSY Soft X-ray FEL | gun, linac, electron, undulator | 315 | ||||||
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A linac driven soft X-Ray FEL facility has been proposed at BESSY with the aim to produce high brilliance photon beams within the energy range of 20eV to 1keV. The driver linac is based on superconducting (sc) L-Band rf-technolgy to enable cw operation of the FEL. As the electron beam emittance directly influence the photon beam characteristics, transverse slice emittances of 1.5pimmmrad are envisaged as a target goal. This demands for a high brilliance laser driven photoinjector rf-gun as electron source. For the first years of operation it is intended to use well known normal conducting (nc) L-Band rf-gun technology thereby restricting the macropulse repetition rate to 1 kHz to cope with the thermal power dissipation. At a later stage the nc rf-gun shall be replaced by a sc rf-gun, which is favoured conceptually as it allows to generate outmost flexible bunch patterns according to the needs of the experiments by fully exploiting the capabilities of the sc linac. This paper details the design considerations for a high power nc rf-gun complemented by results of beam dynamic studies up to the exit of the booster linac using ASTRA. Perspectives for the use of a sc photoinjector gun cavity are addressed.
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MOPKF010 | The Output Performance of the BESSY Multi-stage HGHG-FEL | gun, damping, brilliance, photon | 318 | ||||||
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The BESSY soft X-ray FEL is planned as a High Gain Harmonic Generatio(HGHG) FEL multi-user facility covering the VUV to soft X-ray spectral range(0.02 keV - 1. keV). A photoinjector and a superconducting 2.3GeV CW linac will feed three independent HGHG-FEL-lines. As the efficiency of the interaction between the radiation and the electron beam is higher in a helical undulator, one would tend to prefer such a device for the HGHG scheme. Also a higher K-value of the modulators seems to be advantageous. This is not necessarily the case. We present simulation studies for the BESSY-HGHG-FELs and discuss the output performance for helical stages'' and increased K value of the modulators.
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MOPKF011 | Output Variability of the BESSY Soft X-ray FEL | gun, damping, brilliance, photon | 321 | ||||||
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The BESSY soft X-ray FEL is planned as a High Gain Harmonic Generation HGHG) FEL multi-user facility covering the VUV to soft X-ray spectral rang(0.02 keV - 1 keV). A photoinjector and a superconducting $2.3\,GeV$ CW linac will feed three independent HGHG-FEL-lines. Depending on the optimisation criteria, it is possible to obtain either maximum output power or pure spectrum from the same HGHG-line. We present simulation studies for the BESSY-HGHG-FELs and discuss the possible variability of the output performance.
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MOPKF012 | A 7T Multipole Wiggler in BESSY II: Implementation and Commissioning Results | gun, wiggler, radiation, damping | 324 | ||||||
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To generate hard X-ray beams for residual stress analysis and for magnetic scattering with the BESSY II SR source, a 7T wiggler with 17 poles has been implemented. Several problems had to be solved. Wake fields induced by smaller steps in the geometry of the radiation shield inside the beam chamber led to intolerable LHe consumption, which have been analysed numerically and then cured by improving the shield geometry. Much of the routine operation procedures are influenced by the unusually high radiation power level of max. 55 kW. For system protection an interlock system dumps the electron beam automatically in case of relevant error events. This wiggler is by far the strongest perturbation of the linear beam optics, breaking seriously the symmetry of the ring. Beam optical parameters including tune shift and beta beat have been measured to quantify these perturbations and develop efficient cures to limit the negative effects on beam lifetime and dynamic aperture. So far the wiggler is operated at 2.8 T and max. currents up to 250 mA in normal user shifts.
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MOPKF013 | The Influence of the Main Coupler Field on the Transverse Emittance of a Superconducting RF Gun | wiggler, radiation, damping, gun | 327 | ||||||
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For the Rossendorf superconducting RF gun project the influence of the additional RF field, created in the cavity by the RF power flow at the main coupler, is discussed. One end of the gun cavity is occupied by the cathode insert, so all flanges are concentrated on the other end. In the "flange plane" of the cavity two HOM coupler, the pic up and the main coupler are located. If we normalize the RF field in the cavity by the condition Eacc = 25MV/m and assume a beam power of 10kW (CW mode), we obtain an quality factor Qext = 2.2*10**7. A three dimensional field calculation using the MAFIA code, gives the field perturbation near the main coupler. Tracking calculation with ASTRA show,that this perturbation increases the transversel emittance between 1 and 4%, nearly independent from the bunch charge. This result shows, that for average beam powers in the vicinity of 10kW effects, connected with the assymetric input of RF power can be neglected.
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MOPKF014 | Emittance Compensation of a Superconducting RF Photoelectron Gun by a Magnetic RF Field | wiggler, radiation, damping, gun | 330 | ||||||
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For compensation of transverse emittance in normal conducting RF photoelectron guns a static magnetic field is applied. In superconducting RF guns the application of a static magnetic field is impossible. Therefore we put instead of a static field a magnetic RF field (TE - mode) together with the corresponding accelerating mode into the superconducting cavity of the RF gun. For a 3 _ cell cavity of the superconducting gun with frequencies f = 1.3GHz for the accelerating mode and f = 3.9 GHz for the magnetic mode and a bunch charge of 1 nC a transversal emittance of 0.5 mm mrad has been obtained. In this case the maximal field strength on the axis were Ez = 50 MV/m for the accelerating mode and Bz = 0.34 T for the magnetic mode.(This corresponds to Bs(max) = 0.22T on the surface of the cavity). Possibilities for the technical realization (input of RF power for the TE mode, tuning of two frequencies in one cavity, phase stability) are discussed.
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MOPKF015 | A Superconducting Photo-Injector with 3+1/2- Cell Cavity for the ELBE Linac | wiggler, radiation, damping, gun | 333 | ||||||
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After successful tests of an SRF gun with a superconducting half-cell cavity [*], a new SRF photo-injector for CW operation at the ELBE linac has been designed. In this report the design layout of the SRF photo-injector, the parameters of the superconducting cavity and the expected electron beam parameters are presented. The SRF gun has a 31/2-cell niobium cavity working at 1.3 MHz and will be operated at 2 K. The three full cells have TESLA-like shapes. In the half-cell the photocathode is situated which will be cooled by liquid nitrogen.
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* D. Janssen et. al., First operation of a superconducting RF-gun, Nucl. Instr. and Meth. A507(2003)314 |
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MOPKF016 | S2E Simulations on Jitter for European XFEL Project | wiggler, radiation, damping, gun | 336 | ||||||
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In order to generate stable 0.1 nm wavelength SASE source at the European X-ray laser project XFEL, we should supply high quality electron beams with constant beam characteristics to a 200 m long undulator. Generally, beam parameters such as peak current and energy spread are significantly dependent on jitter or error in RF phase and RF amplitude of superconducting accelerating modules, and magnetic field error of bunch compressors. In this paper, we describe the start-to-end simulations from the cathode to the end of linac to determine the jitter and error tolerances for the European XFEL project.
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MOPKF017 | New Simulations on Microbunching Instability at TTF2 | wiggler, damping, gun, emittance | 339 | ||||||
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Microbunching instability in the FEL driver linac can be induced by collective self-fields such as longitudinal space charge, coherent synchrotron radiation, and geometric wakefields. In this paper, we describe the first start-to-end simulations including all important collective self-fields from the cathode to the end of TTF2 linac with 1.5 million macroparticles.
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MOPKF018 | Injector and Bunch Compressor for the European XFEL Project | wiggler, damping, gun, linac | 342 | ||||||
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For the proper operation of European XFEL project, we should supply high quality electron beams with low emittance, short bunch length, and low energy spread to a 200 m long undulator. In this paper, we describe the optimization and design concepts of the XFEL injector and bunch compressors to control the beam parameter dilution due to the microbunching instability and CSR.
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MOPKF021 | Properties of Cathodes Used in the Photoinjector RF Gun at the DESY VUV-FEL | laser, wiggler, electron, damping | 348 | ||||||
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The new injector of the DESY VUV-FEL is being commissioned in spring 2004. Several cathodes have been tested in the photoinjector RF Gun. We report on quantum efficiency, dark current, and the overall appearance of the cathodes after their use.
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MOPKF022 | Commissioning of the VUV-FEL Injector at TTF | laser, wiggler, electron, damping | 351 | ||||||
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The VUV-FEL at the TESLA Test Facility (TTF) at DESY is being upgraded to an FEL user facility serving high brilliance beams in the wavelength range from the VUV to soft X-rays. The photoinjector has been redesigned to meet the more demanding beam parameters in terms of transverse emittance, peak current, and energy spread. The first phase of the injector upgrade has been finished in spring 2004. We report on its commissioning, including first measurements of beam parameters.
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MOPKF025 | Planar and Planar Helical Superconductive Undulators for Storage Rings, State of the Art | laser, wiggler, electron, damping | 354 | ||||||
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Planar superconductive undulators for low beam currents were successfully tested in the past. In a next step devices suitable for small gaps in storage rings are in preparation. The tests will clarify experimentally the heat load generated by the beam in the cold bore and will allow to optimize the control system of such devices. In addition, the layout of the next generation of planar superconductive undulators with electrically variable polarization direction are introduced in this paper.
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MOPKF026 | Conditioning and High Power Test of the RF Guns at PITZ | laser, wiggler, gun, damping | 357 | ||||||
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This paper describes the recent results of conditioning and high power tests of the photocathode RF guns at the Photo Injector Test Facility at DESY Zeuthen (PITZ). For successful operation of high gain SASE FELs, high phase space density of the electron beam is required. A high gradient in the gun has to be applied to improve the quality of the space charge dominated beams. In addition, long RF pulses and high repetition rate should be achieved to provide a high average power of FEL radiation. The first PITZ RF gun has been successfully tested at a mean power of 27 kW (900μseconds, 10 Hz, and 3 MW) and has been installed at the VUV-FEL at DESY Hamburg. Another RF gun has been installed at PITZ in January 2004 and is being conditioned for high power tests. The dark current behavior for various cathodes and for all operating schemes is also presented.
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MOPKF027 | Optimizing the PITZ Electron Source for the VUV-FEL | electron, wiggler, damping, linac | 360 | ||||||
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The goal of the Photo Injector Test Facility at DESY Zeuthen (PITZ) is to test and optimize electron sources for Free Electron Lasers and future linear colliders. At the end of 2003 the first stage of PITZ (PITZ1) has been successfully completed, resulting in the installation of the PITZ RF gun at the Vacuum Ultra Violet - Free Electron Laser (VUV-FEL) at DESY Hamburg. The main results achieved during the PITZ1 extensive measurement program are discussed in this paper. A minimum normalized beam emittance of about 1.5 pi mm mrad for 1 nC electron bunch charge has been reached by optimizing numerous photo injector parameters, e.g. longitudinal and transverse profiles of the photocathode laser, RF phase, main and bucking solenoid current. The second stage of PITZ (PITZ2), being a large extension of the facility and its research program, has started now. Recent progress on the PITZ2 developments will be reported as well.
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MOPKF029 | Seeding High Gain Harmonic Generation with Laser Harmonics produced in Gases | wiggler, damping, linac, laser | 363 | ||||||
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Free electron lasers employing High Gain Harmonic Generation (HGHG) schemes are very promising coherent light sources for the soft X-ray regime. They offer both transverse and longitudinal coherence, inversely to Self Amplified Spontaneous Emission schemes, where the longitudinal coherence is limited. We propose here to seed HGHG with high harmonics produced by a Ti:Sa femtosecond laser focused on a gas jet, tuneable in the 100-10 nm spectral region. Specifities concerning the implementation of this particular laser source as a seed for HGHG are investigated. Theoretical ad numerical calculations (using PERSEO in particular) are given, for the cases of the SCSS and ARC-EN-CIEL projects.
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MOPKF030 | "ARC-EN-CIEL" a Proposal for a 4th Generation Light Source in France | wiggler, damping, laser, photon | 366 | ||||||
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An accelerator based 4th generation source is proposed to provide the user community with coherent femtosecond light pulses in the UV to X ray range. The project is based on a CW 700 MeV superconducting linac delivering high charge, subpicosecond, low emittance electron bunches with high repetition rate. This facility allows for testing High Gain Harmonic Generation seeded with high harmonics in gases, as well as the standard SASE mode, covering a spectral range down to 0.8 nm and 5 nm respectively. In addition, two beam loops are foreseen to increase the beam current in using the energy recovery technique. They will accommodate undulators for the production of femtosecond synchrotron radiation in the IR, VUV and X ray ranges together with a FEL oscillator in the 10 nm range.
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MOPKF032 | Status of the ESRF Insertion Devices | undulator, wiggler, radiation, damping | 372 | ||||||
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The ESRF insertion devices are the object of a continuous refurbishment in order to follow the changing needs of the beamlines and increase their performances. The successful development of the narrow aperture aluminum chambers pumped by non evaporable getter has resulted in the reduction of the minimum gap from 16 mm to 11 mm . A new set of undulator magnetic assemblies with shorter magnetic periods are being prepared that make use of the lower gap. .A prototype of a new type of revolver undulator support has been completed and successfully tested. Such a structure allows the beamline user to switch between two different undulator periods in less than a minute. Three additional devices will be constructed in 2004. Three new in-vacuum undulators have been installed on the ring. One of them is based on an hybrid magnetic structure and achieves a peak field 20% higher than a pure permanent magnet undulator of identical period. Their main magnetic measurements results and interactions with the stored beam are presented.
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MOPKF043 | An Ultra-high Brightness, High Duty Factor, Superconducting RF Photoinjector | injection, booster, vacuum, damping | 402 | ||||||
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Recent advances in superconducting rf technology, and an improved understanding of rf photoinjector design optimization make if possible to propose a specific design for a superconducting rf gun which can simultaneously produce both ultra-high peak brightness, and high average current. Such a device may prove to be a critical component of next generation x-ray sources such as self-amplified spontaneous emission free-electron lasers (SASE FEL) and energy recovery linac (ERL) based systems. The design presented is scaled from the present state-of-the-art normal conducting rf photoinjector that has been studied in the context of the LCLS SASE FEL. Issues specific to the superconducing rf photoinjector, such as accelerating gradient limit, rf cavity design, and compatibility with magnetic focusing and laser excitation of a photocathode, are discussed.
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MOPKF044 | Wake Fields Effects in the Photoinjector of the SPARC Project | injection, booster, vacuum, damping | 405 | ||||||
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When a bunch travels off axis across structures whose shape is not uniform, such as RF cavity or bellows, generates longitudinal and transverse wake fields. In addition transverse time dependent fields (like transverse RF components and wake fields ) may induce correlated slice centroids displacement, so that each slice centroid motion become affected also by space charge forces generated by the next slices. An evaluation of the emittance degradation and induced energy spread in the SPARC injector is performed with an improved version of the code Homdyn and the results are discussed. A comparison with other codes (ABCI, PARMELA 3D) to validate our model is also presented.
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WEPKF015 | The Design of Cold to Warm Transitions of the LHC | focusing, ion, kicker, bunching | 1624 | ||||||
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The Large Hadron Collider (LHC) is the next accelerator being constructed on the CERN site to be operational in 2007. It will accelerate and collide 7 TeV protons and heavier ions up to lead. More than 2000 cryomagnets working at 1.9 or 4.5 k will form part of the magnetic lattice of the LHC. The transitions from cryogenic temperatures to room temperature zones will be achieved by 200 cold to warm transitions (CWTs). The CWTs will compensate for longitudinal and transversal displacements between beam screens and cold bores, ensuring vacuum continuity without limiting the aperture for the beam. The transverse impedance contribution is kept below the assigned total budget of 1 MΩ/m by means of a 5 μm thick Cu coating that also minimises the dynamic heat load through image currents. Tests have been performed that confirm that the static heat load per CWT to the cryomagnets remains below 2.5 W, hence validating the design.
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WEPKF016 | Instrumental Uncertainty in Measuring the Geometry of the LHC Main Dipoles. | focusing, ion, kicker, bunching | 1627 | ||||||
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In the Large Hadron Collider 1232 superconducting dipoles will bend the two 7 TeV energy beams along a 27 km-circumference trajectory. The series production (assigned to three European firms) will require a well-defined procedure to check, in every magnet, the respect of the dimensional specifications. To verify the tolerances of few tenths of millimeter over the 15-meter length in each cold mass, a laser tracker is necessarily used. To access the two beam apertures and to increase the measurement accuracies, the laser tracker is placed in different stations around the dipole defining a 'multi-station measuring procedure'. The noise affecting all the data taken so far suggested a careful analysis of the procedure itself. Through the computer modeling (based on a Monte Carlo algorithm), the statistical error was quantified and compared to the experimental error. From this comparison the critical aspects of low accuracy rooted in the multi-station procedure were better understood, allowing the optimization of the procedure itself for the forthcoming series production.
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WEPKF017 | The 5 T Superconducting Undulator for the LHC Synchrotron Radiation Profile Monitor | focusing, kicker, undulator, bunching | 1630 | ||||||
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A Synchrotron Radiation Profile Monitor will be used in the LHC to measure the beam profiles from the injection energy of 450 GeV to the nominal energy of 7 TeV. The radiation will be provided by a sequence of two separate magnets: a two-periods 5 T superconducting undulator and the beam separation dipole D3. After a short description of the profile monitor layout, the paper reviews the electromagnetic and mechanical design of the undulator, and reports on the fabrication and cold test results of a first half period prototype.Finally, for the LHC operation with lead ion beams,a proposal for a monitor sensitivity upgrade by using a 12 T. superconducting undulator is presented and discussed.
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WEPKF022 | Electro-mechanical Aspects of the Interconnection of the LHC Superconducting Corrector Magnets | kicker, undulator, bunching, vacuum | 1645 | ||||||
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In addition to the main 1232 bending dipoles and 474 focusing and defocusing quadrupoles, more than 6800 superconducting corrector magnets are included in the LHC machine. They are housed in the superfluid helium enclosures of the main cryomagnets. Among them, the closed orbit correctors (sextupole and octupole) are integrated in the main quadrupole helium vessel and they are powered via an externally routed cryogenic line (line N). During the assembly, these corrector magnets have to be connected according to a complex electrical scheme based on the optical requirements of the LHC machine. Along the 27-km long LHC machine, 440 interconnection boxes are installed and will allow the powering of the correctors by means of a 42-wires auxiliary bus-bar cable, of which the corresponding wires have to be routed to the SSS from the interconnection box. Stringent requirements in terms of volume, mechanical resistance, electrical conductance and insulation, reliability, and respect of the electrical schematics apply during the assembly and splicing of the junctions inside the line-N box. The activities and their sequence, aiming at ensuring the fulfilment of these requirements are presented. The planned activities (assembly, ultrasonic welding, general and electrical inspection, and electrical qualification) and the interactions between the various intervening teams are described.
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WEPKF038 | The Alignment Jacks of the LHC Cryomagnets | kicker, bunching, beamloading, antiproton | 1687 | ||||||
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The precise alignment of the some 1700 cryomagnets of the LHC collider, requires the use of some 7000 jacks. The specific requirements and the need for an cost-effective solution for this large production, justified the development and industrialisation of a dedicated mechanical jack which was developed, and is now being produced, in the framework of a collaboration between CERN and the Center for Advanced Technology in India. Three jacks support each of the 32-ton heavy, 15-meter long cryo-dipoles of LHC, and provide the required alignment features. The main requirements are a setting resolution of 0.05 mm, and a range of movement of 20 mm in the horizontal and 40 mm in the vertical direction. Each jack has two degrees of controlled movement in the horizontal and vertical direction, whereas the remaining horizontal movement is left free. By a suitable choice of the layout of the three jacks, the full range of alignment of a cryo-magnet can be obtained. The design of the jacks evolved from a preliminary value analysis between various concepts, towards the complete engineering of the retained concept, selection of the most appropriate and cost-effective industrial production processes and setting-up of an effective quality assurance policy. Building and testing of 36 prototype jacks allowed an extensive experimental validation of their performance at CERN, where they were operated in the String 2 facility, and yielded an improved understanding for cost-effective steering of the production processes before launching the series production. Presently, the mass production of the jacks is in progress with two Indian manufacturers, and some 1500 jacks have already been delivered to CERN. Considering the successful performance of the jacks, it is now envisaged to extend the use of the same type of jacks to provide the even higher-demanding alignment of the low-beta quadrupoles of LHC.
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WEPKF039 | The Vacuum System of Super SOR | kicker, bunching, beamloading, antiproton | 1690 | ||||||
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The Super-SOR light source is a Japanese VUV and soft X-ray third-generation synchrotron radiation source, which consists of 1.8GeV storage ring and injector. The beam current is circulated up to 400mA. These accelerators are designed so as to fully meet requirements for top-up injection. In order to realize these operation modes, our vacuum system are required on following conditions. One is to obtain the long lifetime. The other is not to melt the vacuum chamber by irradiating the high flux synchrotron radiation. Finally beam instability is not occurred by large wake fields. We describe the design of the vaccum chamber of Super-SOR and present the recent R&D concerning this system.
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WEPKF040 | Magnetic Field Measurement of Quadrupole Magnets for S-LSR | kicker, bunching, beamloading, antiproton | 1693 | ||||||
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S-LSR is a low energy ion storage/cooler ring. It has 12-quadrupole magnets (QM) with a bore radius of 70 mm and a maximum field gradient of 5 T/m. To suppress and control a magnetic flux in a fringing field of a bending magnet (BM), a field clamp with a thickness of 25 mm was installed in between BM and QM. The distance between the field clamp and QM is 80 mm. 3D calculation represented that the QM field is strongly influenced by the field clamp. Therefore, QMs were designed and optimized in considering the influence of the field clamp. Magnetic field measurements were performed by means of a Hall probe and a long search coil. A magnet field measurement by a Hall probe was carried out together with the field clamp and BM for S-LSR. For 12-quadrupole magnets, the measurement by the long search coil which moves in horizontal direction was carried out. The results for each measurements will be discussed.
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WEPKF041 | Permanent Magnet Generating High and Variable Septum Magnetic Field and its Deterioration by Radiation | kicker, bunching, radiation, septum | 1696 | ||||||
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Conventional high field septum magnet is fed by DC current or pulse current. In the case of DC, the problem of coil support is not very important, but the cooling of the coil is serious problem. While, in the case of pulse, the problem of support is much important than that of cooling. However, if the septum magnet is made of permanent magnet, those problems are dissolved. And the cost for electricity and cooling water can be exceedingly decreased. Therefore, we made the model septum magnet which has 1/4 scale of the real size and generates 1[T] with the variable range of ± 10%. The magnetic field distribution in the gap by changing the representative field is reported. When this permanent magnet is set in an accelerator, the deterioration of the permanent magnet by radiation will be serious problem. We also report the dependence of the magnetic fields generated by permanent magnet samples on accumulated radiation by various types of radiation source.
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WEPKF042 | Installation and Operation of New Klystron Power Supply with Fast Solid-State Switch for Klystron Protection at the Photon Factory Storage Ring | kicker, bunching, radiation, septum | 1699 | ||||||
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In the 2.5-GeV Photon Factory storage ring at KEK, there are four klystron power supplies which typically operate at an output voltage of -40 kV with 8 A. We replaced one of these power supplies during 2003 and the new power supply is in operation. This power supply is equipped with a solid-state high-voltage (HV) switch for klystron protection. This HV switch is made up of eighty insulated gate bipolar transistors (IGBT), and it can turn the high-voltage off within a few tens of microseconds in cases of any discharges in the klystrons. We report the performance of this new power supply.
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WEPKF043 | Measurement of the Vertical Quadrupolar Tune Shift in the Photon Factory Storage Ring | kicker, bunching, radiation, quadrupole | 1702 | ||||||
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We measured the frequencies of vertical quadrupole oscillations in the 2.5-GeV Photon Factory storage ring at KEK. The measured vertical quadrupole tunes showed remarkable dependence of about -7.5E-5/mA on the bunch current. This contrasts with our previous result of about +4.8E-5/mA (presented in PAC2003) for the horizontal quadrupole tune shift. These results will suggest that the transverse wake forces in a quadrupolar mode contribute significantly to the transverse motions of particles in the Photon Factory storage ring.
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WEPKF046 | Gradient Field Generation in a Uniform Gapped Magnet | kicker, bunching, radiation, quadrupole | 1705 | ||||||
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Magnets with gradient field (indexed magnets) usually have different gap distances with the different entrance positions. This situation will break a uniformity of the effective length. Trim coils, which are usually used in Cyclotron, are not practical to modify a field distribution when a large gradient is required such as FFAG. In order to generate a gradient field in a constant gapped magnet, a novel method with use of inter-pole is devised. This magnet has not only constant gap but also smaller fringing field compared with a conventional one. This technique should widen the recipe to design a magnet with such a complex magnetic field.
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WEPKF047 | A Super Strong Adjustable Permanent Magnet for the Final Focus Quadrupole in a Linear Collider | kicker, bunching, radiation, quadrupole | 1708 | ||||||
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A super strong magnet, which utilizes permanent magnet material and saturated iron, is considered as a candidate for the final focus quadrupole in a linear collider beamline. This modified Halbach magnet configuration can have a higher magnetic field gradient than a normal permanent magnet quadrupole (PMQ) or electromagnet. There are some issues to be solved if a PMQ is to be used as a final focus quadrupole: the variation of its strength with temperature and the need for the field strength to be deliberately changed. One can use special temperature compensation material to improve the temperature dependence with just a small decrease in field gradient compared to a magnet without temperature compensation. The required field variability can be obtained by slicing the magnet into pieces along the beamline direction and rotating these slices. Results of performance measurements on the PMQ with variable strength will be reported including the realization of the temperature compensation technique.
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WEPKF048 | Characteristics of Ground Motion at KEK and SPring-8 | kicker, bunching, site, radiation | 1711 | ||||||
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Authors Y. Nakayama, T. Ito, (JPOWER); R. Sugahara, S. Takeda, H.Yamaoka, M.Yoshioka (KEK); S.Matsui, C.Zhang (SPring-8); S. Yamashita (ICEPP): Abstract Stability of ground is preferable for accelerator beam operation. We have measured ground motion of ground at the KEKB and SPring-8 site, where the ground has quite different characteristics each other. In this paper, some of analysis results are shown, and the characteristics of the ground motion at the KEKB site and those at the Spring-8 site are compared.
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WEPKF049 | Stretched Wire Flip Coil System for Magnetic Field Measurements | kicker, bunching, site, radiation | 1714 | ||||||
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A flip-coil system using a stretched wire measuring the magnetic field properties of accelerator magnets is described. This system is similar to the conventional rotating coil system except that the stretched wires are used instead of wires wound on the machined surface. This system has advantage of simple fabrication and flexible operation so that different length and bore magnets can be easily measured using the same system. The system also has two loop coils to buck the dominant fundamental field so as to increase the measurement accuracy. This kind of system has issues related to the reproducibility, accuracy of the measured results. The system is evaluated to verify its performances and its results were discussed. The analyzing methods and various efforts to keep the system in high accuracy are presented. Measurement results with this loop coil system were compared with that of the other system.
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WEPKF050 | Measurement of Fast High Voltage Pulse and High Noisy DC Siganla for Modulator at the PLS Linac | kicker, bunching, site, radiation | 1717 | ||||||
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The 2.5-GeV electron linac at Pohang accelerator laboratory (PAL) has been operated continuously as a full energy injector for the Pohang Light Source (PLS) since Dec. 1994. There have been continuous efforts to improve the klystron-modulator system more stable and reliable. At pulse operated modulator system, important pulse and DC signals are beam voltage, beam current, EOLC current HVDC voltage and HVDC current. Pulse signals are fast high voltage pulse 30 Hz, 5ms. These signals are adequate level down from modulator but including high level switching noisy. To amplitude measure of these signals for every trigger signal, we developed special module sampling hold, A/D, calculating and D/A. The output signals of these modules are 0 ~ 10 V DC signal and not include any noise signal. These output signals are connected interlock interface module of the modulator controller. Therefore computer system (PC) of the modulator controller is free to noise of these signals and can precise monitor pulse & noise DC signal. In these paper, we are described itself characteristics pulse and high noisy DC signals of the modulator, signal conditioning technique after noise elimination and operation status of the modulator controller.
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WEPKF051 | Operational Analysis of PLS 2-GeV Electron Linac Klystron-modulator System | klystron, kicker, bunching, site | 1720 | ||||||
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The klystron-modulator(K&M) system of the Pohang Light Source(PLS) had been supplying high power microwaves for the acceleration of 2 GeV electron beams. There are 11 sets of K&M systems to accelerate electron beams to 2 GeV nominal beam energy without operating one klystron-modulator. One module of the K&M system consists of an 80 MW S-band (2856 MHZ) klystron tube and the matching 200 MW modulator. The total accumulated high-voltage run-time of the oldest unit among the 12 K&M systems has reached nearly 68,000 hours as of Dec. 2003 and the summation of all the units' high voltage run-time is approximately 820,000 hours. The overall system availability is well over 95%. There have been continuous efforts to improve the klystron-modulator system more stable and reliable. To improve self-diagnostic, operation, monitoring, and remote communication, we developed a new modulator controller based on an industrial PC platform in 2002. In this paper, we are able to review overall system performance of the high-power K&M system and the operational characteristics of the klystrons and thyratrons, and overall system's availability analysis from Jan. to Dec. 2003.
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WEPKF053 | Status and Development for the JAERI ERL-FEL for High-Power and Long-Pulse Operation | klystron, kicker, bunching, site | 1723 | ||||||
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After the success of energy recovery linac (ERL) for the superconducting free-electron laser (FEL) in the Japan Atomic Energy Research Institute (JAERI), the JAERI ERL-FEL has been upgrading for high-power and long-pulse operation. The new grid pulser for the thermoionic cathode gun is under development and test to increase the beam current by increasing the repetition rate of 10MHz to 20MHz. The new RF sources of CW mode for higher power for non-energy-recovery parts have been installed and tested for long-pulse operation. The properties of the superconducting linac required for the long-pulse operation were also measured such as pressure in the cryomodule, vibration of frequency and piezo tuner response. The RF control systems have been also upgraded to reduce the fluctuation to less than 0.1% for amplitude and 0.1 deg for phase.
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WEPKF054 | Auto-filling Cryogenic System for Superconducting Wiggler | klystron, kicker, bunching, site | 1726 | ||||||
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A 3.2 Tesla superconducting wiggler with period length of 6.0 cm (SW6) was installed in January of 2004 at the National Synchrotron Radiation Research Center (NSRRC). A cryogenic plant for superconducting rf cavity will also provide liquid helium and liquid nitrogen for SW6 by using an independent automatic filling system. To facilitate a stable and precise auto-filling process, a PID controller, the kernel of the auto-filling system, will control the valves of liquid helium and liquid nitrogen, respectively. The authors shall present the control algorithm of different operation modes, namely the pre-cooling mode and normal auto-filling mode. The boil off rate of liquid helium and liquid nitrogen will be discussed.
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WEPKF055 | Design and Implementation of a Switching Mode Bipolar Power Stage of the Correction Power Supply | klystron, kicker, bunching, site | 1729 | ||||||
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In order to enhance efficiency of the correction power supply, the switching mode bipolar power stage was to implement and to substitute for the original power stage of the correction power supply. To ensure higher efficiency, the programming dc bus voltage of the power stage of the correction power supply must be working in accordance with the output current state and load. A new power conversion stage was constructed and employs power MOSFET operating at higher switching frequency then old 60 Hz energy conversion mode system. This will not only improve the efficiency but also decrease the weight of the correction power supply. The new switching mode power stage supply a bipolar power dc bus power and automatic turning working voltage by the feedback balance circuit. Results and working performance will be presented in this paper.
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WEPKF056 | Reducing Output Current Ripple of Power Supply with Component Replacement | klystron, kicker, bunching, site | 1732 | ||||||
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Correction magnets of synchrotron storage ring are served with linear power supplies (correction power supply) with 100 ppm output current ripple in National Synchrotron Radiation Research Center. Reducing output current ripple of correction power supply might reduce perturbation of beam position of storage ring. Replace correction power supplies with lower output current ripple ones is straightforward but costs lots of money. Without adding any other circuit and electronic component, some components of correction power supply are replaced by ones with more precious and lower output fluctuation; so that the same circuitry structure of correction power supply is kept without increasing its complexity and could reach 25 ppm output current ripple.
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WEPKF057 | Design and Study of a Superferric Model Dipole and Quadrupole Magnets for the GSI Fast-pulsed Synchrotron SIS100. | klystron, kicker, bunching, site | 1735 | ||||||
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New experimental results from the investigation of a model superferric Nuclotron-type dipole and quadrupole magnets are presented. The magnets operate at pulse repetition rate f = 1Hz, providing peak magnetic field B = 2 T and the field gradient G = 34 T/m in the dipoles and quadrupoles respectively. The superconducting coil is made from a hollow multi-filamentary NbTi cable cooled with two phase helium flow. Different possibilities were investigated to reduce AC power losses in the case of a cold iron yoke (T=4.5K). The achieved results are discussed. The value of 9W/m has been obtained for dipole magnet with the yoke at T=50K. The first 50 K yoke quadrupole was designed and tested. Other problems, connected with the magnetic field quality, mechanical and cryogenic stability of the magnets under SIS100 operating conditions are also discussed.
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WEPKF060 | Bending Magnets for the SAGA Storage Ring: Manufacturing and Magnetic Measurements | klystron, kicker, bunching, site | 1738 | ||||||
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The paper describes the design, the manufacture and the magnetic measurement of the dipole bending magnets (BM) for SR Source storage ring (prefecture SAGA, Japan) carried out in BINP, Novosibirsk, Russia. The requirement was to create the laminated C-shape BMs with the 3.2 m radius and parallel edges. The magnetic field homogeneity must be not worth than ±2? 10-4 inside the working area: H = 30+40mm and V = ±20mm at 0.26T (250 MeV), and H = ± 28mm and V = ±20mm at 1.46 T (1.4GeV). The BMs were designed on the basis of the 2-D 3-D modeling taking into account the laminated core. The BMs yokes were produced with the help of the technology of the high temperature gluing. The computer simulations are in a good agreement with the magnetic measurements. The main parameters of the magnetic fields satisfy to the requirements and are presented. The features of the design, manufacturing and precise magnetic measurements of SAGA BMs are discussed.
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WEPKF061 | Study of Electrical Steel Magnetic Properties for Fast Cycling Magnets of SIS100 and SIS300 Rings | klystron, kicker, bunching, site | 1741 | ||||||
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The operation conditions of yoke steels in superconducting magnets of the SIS100 and SIS300 are at 4.2 K and unipolar cycles with high magnetic induction. The results of measurements of different classes of electrical steels, both isotropic and anisotropic, in the operating conditions of superconducting dipoles are presented. The measurements are carried out on ring samples in quasistatic mode. Dependence of B(H) as well as values of Hc and hysteresis losses in bipolar and unipolar cycles are determined from hysteresis loops at different temperatures. The anisotropy of steels is measured at room temperature on the strip samples, cut along the rolling direction and across one. The comparison of results on ring and strip samples is carried out. The results of calculations of hysteresis and eddy current losses in iron yoke of fast-cycling dipole for the SIS300 are presented. The recommendations on choice of grade steels for fast cycle superconducting magnets are given.
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WEPKF062 | Study of the Quench Process in Fast-cycling Dipole for the SIS300 Ring | klystron, kicker, bunching, site | 1744 | ||||||
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The results of numerical quench process simulation in the coil of superconducting dipole with magnetic field of 6 T and 100-mm aperture for high-energy ion and proton synchrotron facility SIS300 are presented. The peculiarities of quench process developed in dipole are discussed for several variants of quench conditions. The coil quench behavior determines the features, scopes, and limitations in possible quench protection scheme. Main design characteristics of the preferable protection system are considered.
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WEPKF063 | Comparison of Three Designs of Wide Aperture Dipole for SIS300 Ring | klystron, kicker, bunching, site | 1747 | ||||||
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The GSI Fast-Pulsed Synchrotron Project is found now under development. The last stage of this machine is the SIS300 ring, which will use superconducting dipoles with 100-mm aperture, 6-T magnetic field amplitude and 1-T/s field ramp rate. This dipole has to posses minimal heat losses both in the coil and in the iron yoke. This article considers three designs of such dipole. The main distinction of these designs is the different thickness of stainless steel collars, which are supported the coil. The collars in the first design hold all forces arisen in the magnet. The second design needs collars only for assembly of the coil and cooling down of the magnet. An iron yoke in this design will withstand ponderomotive forces. The third design has no collars and the iron yoke will hold all forces, including preload, forces originated during cooling down and ponderomotive forces. The different mechanical, magnetic and thermal characteristics are presented and comparative analysis of these designs is carried out.
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WEPKF064 | Methods for Reducing Cable Losses in Fast-Cycling Dipoles for the SIS300 Ring | klystron, kicker, bunching, site | 1750 | ||||||
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A new synchrotron facility is being designed for the acceleration of high intensity and high-energy ion and proton beams at GSI, Darmstadt. The main magnetic elements of the second stage (SIS300) are superconducting dipoles with 100 mm aperture, 6-T magnetic field amplitude, and 1 T/s field ramp rate. The main requirements for these magnets, in addition to high field quality, are minimal heat losses, both in the coil and in the iron yoke, at an acceptable temperature margin. An increase of the temperature margin can be achieved by increasing the volume of superconductor in the cable. However, increasing the number of strands in the cable results in a growth of the cable width. Since coupling losses in the cable are proportional to the fourth power of cable width, these losses rise dramatically. This presentation considers and analyses different ways of reducing these cable heat losses. The calculated results of heat losses for different geometries, based on various cable designs, as well as the parameters of optimal cable designs, based on computer simulations, are presented.
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WEPKF065 | Study of Thermal Stability and Quench Process of HTS Dipole | klystron, kicker, bunching, site | 1753 | ||||||
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The dipole with a coil made from HTS composite on a Bi2223 basis and placed in the ferromagnetic yoke has been developed and produced in IHEP. A designed magnetic field of the dipole in 20-mm aperture is 1 T at temperature of liquid nitrogen. The numerical analysis of factors, having influence on thermal stability of the magnet, as well as the computer simulations of dipole heating during quench was carried out. An anisotropy of voltage-current characteristics of HTS tapes in a magnetic field is taken into account in calculations of quench process. The measured results of voltage-current characteristics during powering and quench of the coil are in a good agreement with the numerical calculations
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WEPKF066 | Stability of Fast-cycling Dipole for SIS300 Ring | klystron, kicker, bunching, site | 1756 | ||||||
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Funding AgencyShould not exceed 200 charactersFootnotesFootnotes: Not exceeding 200 chaThe main requirement to the superconducting dipole with 100-mm aperture, 6-T magnetic field amplitude and 1-T/s field ramp rate for the SIS300 accelerator, developed in the GSI, Darmstadt, is a stability of the magnet influenced by various heat releases arising during operation mode. The computer simulation of the heating of superconducting dipoles and cooling helium during the SIS300 operating cycle was carried out. The analysis of stability is based on the numerical solution of the heat balance equation in the coil and in a single?phase helium flow. Temperature margin of the superconducting dipole during the SIS300 operating cycle was calculated. Possible ways to increase the temperature margin are discussed.
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WEPKF068 | Developments in Magnet Power Converters at the SRS | klystron, bunching, site, beamloading | 1759 | ||||||
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A project to upgrade the magnet power converters of the SRS has commenced to ensure its efficient operation for its remaining operational lifetime. A recent risk analysis of the facilities equipment identified that the main areas for concern were the Storage Ring magnet power converters, kicker and septum pulse power supplies and the Booster Dipole "White Circuit" and associated power converters. This report detail the development and replacement programs currently active at Daresbury Laboratory, including future work identified to support and improve SRS utilisation.
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WEPKF069 | 52 kV Power Supply for Energy Recovery Linac Prototype RF | klystron, bunching, site, beamloading | 1762 | ||||||
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Daresbury Laboratory is constructing a Radio-Frequency (RF) Test Facility to be capable of testing RF cavities for accelerator applications. Electrical power for the RF equipment will be provided from an existing -52 kV 6-pulse rectifier and transformer system capable of delivering 16A DC continuous current. A crowbar circuit will be provided to divert the large amount of stored energy in the smoothing capacitor bank in the event that a spark should occur between the cathode and the body or modulating anode. Traditionally, the crowbar has been provided by using an ignitron, but modern solid state devices have sufficient performance to meet the requirements. This paper discusses the numerous design options that were considered for the circuit parameters.
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WEPKF070 | Design Issues for the Superconducting Magnet that goes around the Liquid Hydrogen Absorber for the Muon Ionization Cooling Experiment (MICE) | vacuum, focusing, klystron, bunching | 1765 | ||||||
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This report describes the design issues that are associated with a superconducting focusing solenoid that goes around a liquid hydrogen absorber for the Muon Ionization Cooling Experiment (MICE) proposed for the Rutherford Appleton Laboratory. The solenoid consists of two superconducting coils that may operated at the same polarity or at opposite polarities. As a result, the coils and their support structure must be designed to carry a 300 ton inter-coil force that is forcing the coils apart along their axis. The basic design parameters for the focusing magnet are discussed. The magnet and its cryostat are designed so that the absorber can be assembled and tested before installation into the pre-tested focusing solenoid. A safety requirements for MICE dictate that the insulating vacuum for the superconducting magnet be separated from the insulating vacuum for the absorber and that both vacuum be separated from the experiment vacuum and the vacuum within adjacent RF cavities. The safety issues associated with the arrangement of the various vacuums in the MICE focusing modules are presented. The effect of magnet operation and magnet quench on the liquid hydrogen absorber is also discussed.
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WEPKF071 | A New Current Regulator for the APS Storage Ring Correction Magnet Bipolar Switching Mode Power Converters | vacuum, focusing, klystron, bunching | 1768 | ||||||
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The correction magnets in the Advanced Photon Source's storage ring are powered by PWM-controlled bipolar switching-mode converters. These converters are designed to operate at up to ± 150 A. The original current regulator used a polarity detection circuit, with a hysteresis, to determine which IGBT was needed to regulate the current with a given polarity. Only the required IGBT was switched while others were held on or off continuously. The overall IGBT switching losses were minimized by the design. The shortcoming of the design is that the converter's output is unstable near zero current because of the hysteresis. To improve the stability, a new current regulator, using a different PWM method, has been designed to eliminate the requirement of the polarity detection. With the new design, converters can operate smoothly in the full range of ±150 A. The new design also meets tighter specs in terms of the ripple current and dynamic response. This paper describes the design of the new regulator and the test results.
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WEPKF072 | Clearing Electrodes for Vacuum Monitoring at the Fermilab Recycler | focusing, klystron, bunching, site | 1771 | ||||||
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The Fermilab Recycler is a fixed 3.3-km 8-GeV kinetic energy storage ring located in the Fermilab Main Injector tunnel. Each split-plate beam position monitor in the Recycler is also used to generated an ion clearing field for ions trapped by the antiproton beam. Approximately 100 locations have been instrumented with pico-amp meters to measure the electron current, generated by the beam-ionized residual gas in the vacuum chamber. This electron current is found to be proportional to the beam current and to the residual gas pressure in the Recycler and may be used to monitor the Recycler vacuum.
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WEPKF073 | 2nd Generation LHC IR Quadrupoles Based on Nb3Sn Racetrack Coils | focusing, klystron, bunching, site | 1774 | ||||||
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After the LHC operates for several years at nominal parameters, it will be necessary to upgrade it for higher luminosity. Replacing the baseline NbTi low-beta quadrupoles with a higher performance magnets based on advanced superconducting materials and magnet technologies is one of the most straightforward ways in this direction. Preliminary studies show that high-performance Nb3Sn strands to be available within the next few years allow increasing the quadrupole aperture up to 110 mm using a 4-layer shell-type coil and providing the same 200 T/m field gradient with 20% margin as the baseline magnets. It will allow reduction of b* by a factor of 3. An alternative approach to the quadrupole design is based on simple flat racetrack coils. This paper discusses the possibilities and limitations of large-aperture racetrack quadrupole designs and compares them to the shell-type magnets.
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