CERN, Geneva
The understanding of electrical breakdowns has a critical role in the design of the RF accelerating cavities for the CLIC linear collider. In this context a new statistical model of the conditioning process and breakdown rate evolution is presented for a DC spark system with tip-plane electrode geometry charged from a capacitance. The approach requires a small amount of assumptions, but can still make several interesting predictions. Electrode gap distance dependence on the saturated breakdown field and spitfest (grouped breakdowns) are among the phenomena that could be explained from this simple model.
Far-Tech, Inc., San Diego, California
We describe the design and construction status of a compact, 830 kW multi-beam klystron (MBK) for driving 1300 MHz cryomodules. The applications for this tube range from ILC and ILC test facilites to Project X. The use of low gun voltage (36 kV) simplifies the modulator and gun socket requirements. A high efficiency, predicted to be > 65%, will allow the klystron to be used in applications requiring low overall site power and high wallplug efficiency.
DESY Zeuthen, Zeuthen
DESY, Hamburg
The European XFEL, an X-ray free electron laser, is planned as an European project with a strong connection to the DESY research center in Hamburg. The LINAC of the XFEL incorporates 27 RF stations, which supply the RF power required by the superconducting cavities. In order to generate the RF power (1.3 GHz, 10MW pulses) HV pulse modulators are required. Each modulator has to supply 12kV pulses at 1.6kA for 1.5ms pulse duration and at 10Hz nominal repetition rate. The repetition rate can be increased to 30Hz at shorter pulse duration. Although extensive experience exists from the test facilities FLASH and PITZ (DESY Hamburg and Zeuthen sites) a dedicated modulator test stand has been setup to test and investigate additional new modulator prototypes developed by different companies. The results of these tests and the experience gained with the RF-stations at PITZ and FLASH will be an important criterium for the decision on the final layout and choice of vendor. An overview of the Modulator Test Facility at DESY will be presented. The first of two prototypes was delivered in July 2008 and started its operation in October. First test results of this prototype will be presented.
Thomson Broadcast & Multimedia AG, Turgi
DESY, Hamburg
DESY Zeuthen, Zeuthen
The European XFEL project at DESY in Germany requires 27 RF stations capable of 10 MW RF power each. Each RF station needs one high voltage modulator that generates pulses up to 12 kV and 2 kA with a duration of 1.7 ms and a nominal repetition rate of 10 Hz. DESY decided to investigate new modulator prototypes and Thomson has been awarded to design and build one of these prototype modulators. The Thomson modulator is based on the pulse step modulator (PSM) principle. This technology allows the regulation of the pulse voltage during the pulses and by this achieving a good flatness. In addition to the common PSM technology this modulator design includes additional features. The first one is a constant power regulation system in order to prevent a 10 Hz loading of the mains. The second one is the extension of a part of the system to allow 2-quadrant mode in order to demagnetise the core of the pulse transformer between the pulses. The modulator has been delivered to DESY in July 2008 and is under testing at the modulator test facility in Zeuthen. The paper will give a detailed overview on the system and shows the results of the factory testing and of the testing at DESY.
BNL, Upton, Long Island, New York
Vibration stability in third generation light sources such as the 3 GeV NSLS II under construction at BNL and which are aiming at high brightness and extremely small photon beam sizes is paramount. Movement of the magnetic elements of the accelerator lattice, and in particular when uncorrelated, will induce jitter in the beam and degrade the machine performance. The accelerator lattice response is coupled with the ring structure which in turn interacts with the site and the ground vibration field that characterizes it. Therefore, understanding this dynamic coupling between the accelerator ring structure and the site and the “filtering” effect of the interaction on both the amplitude and the spectral characteristics of the ground vibration is central towards establishing the response of the lattice. In this study, the site-ring dynamic interaction is evaluated based on the NSLS II design and site conditions using a state-of-the-art 3-D wave propagation and scattering analysis model. The study is augmented with an extensive array of measurements at the selected site as well as field studies at similar operating light source facilities.
BNL, Upton, Long Island, New York
Cultural noise generated within or in the proximity of a light source facility aiming to achieve stability levels of just tens of nanometers in the electron beam and extremely small photon beams in special experimental lines could be a limiting factor towards achieving the performance goals. While operating systems within the facility are more readily identifiable as sources of vibration and cause of instabilities and they tend to be of deterministic nature so appropriate action can be taken to minimize their impact, moving-type loads such as traffic in the general vicinity or within the bounds of the accelerator facility are more of a stochastic nature and require a different approach in assessing its impact on the synchrotron facility. In this study the effect of such loads which poses both stochastic elements and a complex spectrum on the stability performance goals of the NSLS II synchrotron and its vibration-sensitive experimental lines is addressed prior to the construction of the facility. This is achieved through the synergy of a comprehensive numerical model and an array of recorded field data.
BNL, Upton, Long Island, New York
The extremely small photon beam dimensions of NSLS II impose challenging requirements on the e-beam orbital stability in the 6-D phase space. The electron beam orbit at the photon source locations must remain within a few hundred nanometer window for a wide frequency band. The beam orbit movement is coupled to the movement of the magnetic elements in the lattice which are itself coupled to the ring-building structure. While the vibration exciting the ring structure consists of deterministic and stochastic noise, it is the high frequency random, uncorrelated part that has the largest impact on the residual beam orbit movement as it is most difficult to control by fast orbit feedback. In this study, an analytical model is employed to quantify lattice displacement and beam orbit jitter for the expected conditions of NSLS II. The dynamic interaction of the ring supporting the lattice with the stationary ground vibration is addressed using a 3-D model of wave-structure interaction. Cross transfer functions linking ground vibration with the ring and magnetic lattice for various stochastic parameters are deduced leading to a multi-degree of freedom cross-spectral density of the lattice.
DESY, Hamburg
WTM, Hamburg
This poster describes the organizational structures and processes which were established for coordinating civil construction at the European XFEL. Local managements supervise the different construction sites in cooperation with a central team which manages the overall effort and provides general services (e.g. coordination, communication, safety, legal). Communication processes, workflows for reviewing, approving and distributing construction drawings and formalized change management have been defined and established. Reporting, cost management and controlling procedures have been put in place, as well as procedures for maintaining good public relations. All the processes are documented in a project handbook, and they are supported and optimized by IT systems, in particular the DESY Engineering Data Management System, DESY EDMS.
DESY Zeuthen, Zeuthen
DESY, Hamburg
A first prototype of a switching mirror has been designed, built and tested. With a repetition rate of up to 2.5 Hz the mirror is used to provide different beam lines with the Laser light produced by FLASH. The repetition accuracy is in the order of 1 um whereas the yawing is about 1 arcsec.
ORNL, Oak Ridge, Tennessee
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy
Latest technologies promise new control systems user interface features and greater interoperability of applications. New developments using Java and Eclipse aim to unify diverse control systems and make communication between applications seamless. Web based user interfaces can improve portability and remote access. Modern programming tool improve efficiency, support testing and facilitate shared code. This talk will discuss new developments aimed at improving control system interfaces and their development environment.
Cosylab, Ljubljana
Accelerators are designed to be in operation for several decades, and frequently even their construction alone takes a decade or more. Given the rapid rate of obsolescence of information technologies, it becomes a challenge how to choose the technologies that would stand the test of time, or at least make long-term support manageable. In this article, we focus on middleware: the glue that keeps inherently heterogeneous control system platforms able to interoperate with each another. Modern and less-modern middlewares, such as Internet Communication Environment (ICE), Common Object Request Broker Architecture (CORBA), Microsoft Windows Communications Foundation (WCF) are presented, and contrasted with more domain-specific middleware, such as the Experimental Physics and Industrial Control System (EPICS). We argue that whichever middleware technology is used, it is advisable to abstract it with simple, domain-specific APIs, whose implementation can change as the evolving performance requirements push the initial middleware choice beyond its limits of applicability.
Imperial College of Science and Technology, London
Imperial College of Science and Technology, Department of Physics, London
Cockcroft Institute, Lancaster University, Lancaster
The proposed Muon Cooling System for the Neutrino Factory operates with high accelerating gradient in the presence of magnetic field. This can significantly increase the risk of RF breakdown. Field Emission is the most frequently encountered RF breakdown that occurs at sites with local electromagnetic field enhancement. Surface defects can be considered as possible emission sites. Upon Impact, generally the majority of electron’s energy is converted into stress and heat. In return, the damage inflicted can create additional emission sites. This paper presents the work under way, which aims to model certain physical phenomena during both emission and impact of electrons. The three-dimensional field profile of an 805 MHz pill-box cavity is modelled by Comsol Multuphysics. A tracking code written in-house is employed to track particles, providing sufficient data such as energy and speed at small time steps. This would allow the study of local heat transfer, applied surface stresses and secondary electron yield upon impact with the RF surface. In addition, the effects of externally applied magnetic field on electron’s behaviour are to be investigated.
JLAB, Newport News, Virginia
Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
SRF cavities are observed to be limited by non-linear localized effects. The variation of local material parameters between "hot" and "cold" spots is thus of intense interest. Such locations were identified in a BCP etched large-grain single-cell cavity and removed for examination by high resolution electron microscopy (SEM), electron-back scattering diffraction microscopy (EBSD), and scanning Auger electron spectroscopy (SAM). Pits with clear crystal facets were observed on both "Hotspot" and "Coldspot" specimens. The pits were found in-grain and on "Y"-shaped junction of three crystals. They are interpreted as etch pits induced by surface crystal defects (e.g., dislocations). All "Coldspots" examined had obvious low density of etching pits or very shallow tri-crystal boundary junction. EBSD revealed crystal structure surrounding the pits via crystal phase orientation mapping. This study suggests a mechanism by which BCP etching creates pits on large-grain Nb cavity surfaces and sharp-edged topography in fine-grain Nb. Field enhancements at very deep, sharp and densely populated etching pits may then cause distributed hotspots and limit cavity performance.
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
The SuperB collider project aims at the construction of an asymmetric high luminosity B-Factory in the Tor Vergata University campus in Rome (Italy). The engineering aspects of the SuperB design and construction with the aim to reuse at maximum the PEP II components will be presented. Sinergies with the Italian FEL project SPARX, which will start civil construction this year, will be discussed. The two projects can share the Linac tunnel and other facilities. A study of ground motion will also be presented.
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
The goal of a Neutrino Factory is to generate intense beams of neutrinos from muon decay inorder to study CP violation in the Standard Model, the mass hierarchy, and the neutrino mixing angle θ13. Intense muon beams are created and accelerated in a system of particle accelerators to energies of 20-50 GeV. They are then allowed to decay in dedicated storage rings with long straight sections aligned on suitably chosen long-range detectors. A variety of geometries are possible, and their design and construction present demanding challenges for accelerator R & D, covering not only beam optics but touching on geological and engineering aspects of constructing almost vertical storage rings several hundred metres below the Earth's surface. The basic ideas are described in this paper and are demonstrated by three possible models developed in recent years.
Sheffield University, Sheffield
University of Warwick, Coventry
STFC/RAL/ISIS, Chilton, Didcot, Oxon
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
Funding: Science and Technology Facilities Council (United Kingdom)
The UK programme of high power target developments for a Neutrino Factory is centred on the study of high-Z materials (tungsten, tantalum). A description of lifetime shock tests on candidate materials is given as a part of the research into a solid target solution. A fast high current pulse is applied to a thin wire of the sample material and the lifetime measured from the number of pulses before failure. These measurements are made at temperatures up to ~2000 K. The stress on the wire is calculated using the LS-DYNA code and compared to the stress expected in the real Neutrino Factory target. It has been found that tantalum is too weak at these temperatures but a tungsten wire has reached over 26 million pulses (equivalent to more than ten years of operation at the Neutrino Factory). Measurements of the surface velocity of the wire using a laser interferometry system (VISAR) are in progress, which, combined with LS-DYNA modelling, will allow the evaluation of the constitutive equations of the material. An account is given of the optimisation of secondary pion production and capture in a Neutrino Factory and of the latest solid target engineering ideas.
NSRRC, Hsinchu
The TPS (Taiwan Photon Source) of NSRRC is in the design stage now. The grounding system is crucial to the safety issue, the electrical reference level, the electrical noise and the EMI problems. In order to provide a high quality electrical environment, the grounding system should be designed carefully. The soil resistivity of the construction site was investigated first. Many different configurations of the ground grid layouts were simulated and compared. Beside the horizontal ground-conductors, the vertical ground-electrodes of 30 m are considered to be installed below the ground surface and they will reach the ground water level in hopes of minimizing the resistance of ground grid. The main goal is to obtain a ground grid with resistance lower than 0.2 ohm. A rectangular ground grid will also be installed under the new utility building. It will be connected to the ground grid of TPS to further reduce the resistance of whole grounding system, and also to eliminate the potential difference between them.
ORNL, Oak Ridge, Tennessee
There are many planned or nascent particle-accelerator-based projects world-wide. Often these are large and complex projects that can benefit from strong project management. Following the premise that it is better to learn from the community’s successes rather than its mistakes, this talk will draw on successful experiences from the Oak Ridge SNS project in elaborating strategies and techniques for successful project management.
CERN, Geneva
IN2P3-LAPP, Annecy-le-Vieux
The demanding nanometer transverse beam sizes and emittances in future linear accelerators results in stringent alignment and nanometer vibration stability requirements. For more than two decades, ground vibration measurements were made by different teams for feasibility studies of linear accelerators. Recent measurements were performed in the LHC tunnel and at different CERN sites on the surface. The devices to measure nanometer sized vibrations, the analysis techniques and the results are critically discussed and compared with former measurement campaigns. The implications of the measured integrated R.M.S. displacements and coherence length for the CLIC stabilization system are mentioned.
Fermilab, Batavia
BINP SB RAS, Novosibirsk
Understanding slow and fast ground motion is important for the successful operation and design for present and future colliders. Since 2000 there have been several studies of ground motion at Fermilab. Several different types of hydro static water levels have been used to study slow ground motion (less than 1 hertz) seismometers have been used for fast (greater than 1 hertz) motions. Data have been taken at the surface and at locations 100 meters below the surface. Data and results on slow ground motion will be discussed in particular the effects of natural and cultural sources of motion. We also present estimates on the ATL-diffusion coefficients at various locations.
IN2P3-LAPP, Annecy-le-Vieux
ICEPP, Tokyo
KEK, Ibaraki
University of Tokyo, Tokyo
Funding: Work supported by the Agence Nationale de la Recherche of the French Ministry of Research (Programme Blanc, Project ATF2-IN2P3-KEK, contract ANR-06-BLAN-0027).
Future linear collider projects like ILC and CLIC will have beam sizes of a few nm. Vibration sources like ground motion can hamper the beam collisions. Relative jitter tolerance between the final focus magnets and the Interaction point (IP) is a fraction of the beam size. The ATF2 project proposes a test facility with a projected beam of 37nm. To measure the beam size with only 2% of error, vertical relative jitter tolerance (above 0.1Hz) between the final doublet magnets (FD) and the IP (with a Shintake beam Size Monitor: BSM) is of the order of 7nm while ground motion is of about 150nm. Thanks to determined adequate instrumentations, investigations were done to design supports for FD. Since ground motion measurements showed that this one is coherent up to 4m, more than the distance between FD and BSM, we chose a stiff support for FD fixed to the ground on its entire surface. Thus, FD and BSM should move in a coherent way. Vibration measurements show that relative motion between FD and BSM is only of 4.8nm and that flowing water in FD does not add any significant jitter. The FD support has been consequently validated on site at ATF2 to be within the vibration specifications.
ANL, Argonne
Funding: This work is supported by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357.
A Cf-252 fission source yields neutron-rich fission fragments. The CAlifornium Rare Ion Breeder Upgrade (CARIBU) project is an upgrade to the Argonne Tandem Linear Accelerator System (ATLAS) that provides a 37 GBq (1 Ci) source of these radioactive ions for acceleration. Fission fragments stop in a gas catcher, are extracted into an ECR ion source to increase the charge state, and then accelerated in ATLAS. The radiation fields produced by an unshielded 1 Ci 252Cf source are 46 rem/hr (neutron) and 4 R/hr (gamma) at 30 cm. A shielding system has been constructed that reduces the radiation fields to ≤ 1 mrem/hr at 30 cm from all accessible surfaces. The MCNPX code was used to model the transport of the spontaneous fission neutrons and gamma radiation, and the gamma radiation induced in the shielding materials by the neutrons. The primary neutron shielding material chosen was 5% borated polyethylene, enclosed in steel. Calculations are made for emissions of radioactive effluents, primarily noble gases, using the EPA CAP-88 computer program. The maximum credible incident scenario releases a small quantity of Cf-252. Calculated dose results and mitigation methods are presented.
Tech-X, Boulder, Colorado
Fermilab, Batavia
Funding: This work was supported by the US DOE Office of Science, Office of Nuclear Physics, under Grant No. DE-FG02-08ER85183
A new set of tools for BBSIM has recently been developed to analyze the nature of the diffusion in multi-particle simulations. The diffusion subroutines are currently used to accelerate beam lifetime calculations by estimating the diffusion coefficient at various actions and integrating the diffusion equation. However it is possible that there may be regimes where anomalous diffusion dominates and normal diffusion estimates are incorrect. The tools we have developed estimate the deviation from normal diffusion and can fit the coefficients of a jump diffusion model in the event that this type of diffusion dominates.