Fermilab, Batavia
Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-76CH03000
Steady growth of luminosity has been demonstrated during the entire Tevatron Run II culminating in a record Tevatron performance. During last two years the major contributions came from improvements in antiproton stacking and cooling as well as from numerous improvements in the Tevatron. The talk will describe these improvements as well as other unexpected problems which were encountered and resolved on the road to this success.
SLAC, Menlo Park, California
Funding: Work supported by US DOE contract DE-AC03-76SF00515.
Second-generation B-Factory proposals are being considered both by KEK in Japan (Super KEKB) and by an INFN Frascati/SLAC/CalTech collaboration in Italy (Super-B). Novel collision schemes like crab waist with crab-sextupoles and also crab cavities are being proposed to mitigate the beam-beam effects of a large crossing angle. The talk will present concepts from both proposals in the context of the experience with the present PEP-II and KEKB B-Factories, which have been successful far beyond the initial performance goals.
Fermilab, Batavia
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
We present the strategy which has been used recently to optimize integrated luminosity at the Fermilab Tevatron proton-antiproton collider. We use a relatively simple model where we keep the proton intensity fixed, use parameters from fits to the luminosity decay of recent stores as a function of initial antiproton intensity (stash size), and vary the stash size to optimize the integrated luminosity per week. The model assumes a fixed rate of antiproton production, that a store is terminated as soon as the target stash size for the next store is reached, and that the only downtime is due to store turn-around time. An optimal range of stash size is predicted. Since the start of Tevatron operations based on this procedure we have seen an improvement of approximately 35% in integrated luminosity. Other recent operational improvements have been achieved by decreasing the shot setup time and by reducing beam-beam effects by making the proton and antiproton brightnesses more compatible , for example by scraping protons to smaller emittances.
CERN, Geneva
The Large Hadron Collider beams are brought into collision by superconducting orbit corrector magnets which generate the parallel separation and crossing angles at the interaction points during the different cycle phases. Unfortunately, the magnetic field errors that result from hysteresis effects in the operation region of these magnets lead to unwanted orbit perturbations. In a previous paper, it has been shown that these effects are within the perturbations coming from beam-beam interactions for the MCBC and the MCBY magnets but are significant in the case of the MCBX magnets. This paper presents a refined model of their field in the frame of the Field Description for the LHC (FiDeL), the results obtained from new magnetic measurements in cold conditions to test the model, the powering mechanism employed to maximize their field reproducibility, and the impact the modeling error is predicted to have on the LHC orbit.
CERN, Geneva
The LHC Early Separation Scheme consists in a four 5-10 Tm dipole scheme (D0s) installed close to the two LHC high luminosity experiments. Its aim, in the framework of LHC Phase II Upgrade, is to improve the luminosity by reducing the crossing angle between the two colliding beams, mitigating and controlling at the same time their parasitic interactions. We investigate a less invasive implementation in the detectors (D0 at 14 from the IP) with respect to those already presented (D0 at 7 m from the IP). The luminosity performances are discussed and a tentative analysis on beam-beam effect impact is given. For the new D0 position, preliminary dipole design and power deposition results are shown.
CERN, Geneva
Pre-cycles for setting up the main magnets of the Large Hadron Collider are necessary for ensuring field reproducibility and low field-decay rates at injection. In this paper we propose standard pre-cycles for the main magnets of the LHC. We study the influence of the pre-cycle parameters on the field decay at injection by two different models. One already proven model is semi-empirical based on magnetic measurements of the magnets. The other is a new network based model of a Rutherford cable which directly calculates the current redistribution and associated magnetization change in the cable strands. The pre-cycle to be used may depend on the history of the machine or may have to be changed because of unforeseen phenomena in the machine. The choice of a new pre-cycle on the basis of magnetic measurements alone is a lengthy process. We confirm the usefulness of the network based model as a tool for selecting new pre-cycles, including decay-blocking degaussing pre-cycles, and compare with magnetic measurements.
Fermilab, Batavia
Funding: Department of Energy, U.S.A.
A novel prototype of SCRF cavity tuner is being designed and tested at Fermilab. This is a superconducting C-type iron dominated magnet having a 10 mm gap, axial symmetry, and a 1 Tesla field. Inside the gap is mounted a superconducting coil capable of moving ± 1 mm and producing a longitudinal force up to ± 1.5 kN. The static force applied to the RF cavity flanges provides a long- term cavity geometry tuning to a nominal frequency. The same coil powered by a fast AC current pulse delivers mechanical perturbation for fast cavity tuning. This fast mechanical perturbation could be used to compensate a dynamic RF cavity detuning caused by cavity Lorentz forces and microphonics. A special configuration of magnet system was designed and tested.
Fermilab, Batavia
Muons, Inc, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282
Magnets for the proposed muon cooling demonstration experiment MANX (Muon collider And Neutrino factory eXperiment) have to generate longitudinal solenoid and transverse helical dipole and helical quadrupole fields. This paper discusses the 0.4 M diameter 4-coil Helical Solenoid (HS) model design, manufacturing, and testing that has been done to verify the design concept, fabrication technology, and the magnet system performance. The model quench performance in the FNAL Vertical Magnet Test Facility (VMTF) will be discussed.
Muons, Inc, Batavia
NHMFL, Tallahassee, Florida
High temperature superconductors (HTS) have been shown to carry significant current density in the presence of extremely high magnetic fields when operated at low temperature. The successful design of magnets needed for high energy physics applications using such high field superconductor depends critically on the detailed wire or conductor parameters which are still under development and not yet well-defined. The HTS is being developed for accelerator use by concentrating on the design of solenoid magnet that will have a useful role in cooling muon beam phase space. A conceptual design of a high field solenoid using YBCO conductor is being analyzed. Mechanical properties of the HTS conductors will be measured along with engineering current densities (JE) as a function of temperature and strain to extend the HTS specifications to conditions needed for low temperature applications. HTS quench properties are proposed to be measured and quench protection schemes developed for the solenoid magnet.
CERN, Geneva
The LHC collider has recently started-up at CERN. It will provide colliding beams to four experiments installed in large underground caverns. A specially designed and constructed sector of the LHC beam vacuum system transports the beams though each of these collision regions, forming a primary interface between machine and experiment. ATLAS is the largest of the four LHC colliding beam experiments, being some 40 m long and 22 m in diameter. Physics performance, geometry and access imposed a large number of constraints on the design of the beam vacuum system. This paper describes the geometry and layout of the ATLAS beam vacuum system. Specific technologies developed for ATLAS, and for the alignment and installation of the vacuum chambers are described as well as the issues related to the physical interfaces with the experiment.
LBNL, Berkeley, California
Funding: Supported by the U.S.Department of Energy under Contract No. DE-AC02-05CH11231.
Insertion quadrupoles with large aperture and high gradient are required to achieve the luminosity upgrade goal of 1035 cm-2 s-1 at the Large Hadron Collider (LHC). In 2004, the US Department of Energy established the LHC Accelerator Research Program (LARP) to develop a technology base for the upgrade. The focus of the magnet program, which is a collaboration of three US laboratories, BNL, FNAL and LBNL, is on development of high gradient quadrupoles using Nb3Sn in order to operate at high field and with sufficient temperature margin. Program components address technology issues regarding coil and structure fabrication, quench performance, field quality and alignment, length scale-up, quench protection, radiation hardness, conductor and cable. This paper reports the current status of model quadrupole development and outlines the long-term goals of the program.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
USC, Los Angeles, California
Funding: Work supported in part by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
Recent progress in generating gradients in the 10's of GV/m range with beam driven plasmas has renewed interest in developing a linear collider based on this technology. This talk will explore possible configurations of such a machine, discuss the key demonstrations and the facilities needed to advance this effort and highlight possible alternative uses of this technology.
LBNL, Berkeley, California
Funding: This work was supported by the Office of Science, U. S. Department of Energy, under Contract No. DE-AC02-05CH11231.
There is considerable interest in the use of muon beams to create either an intense source of decay neutrinos aimed at a detector located 3000-7500 km away (a Neutrino Factory), or a Muon Collider that produces high-luminosity collisions at the energy frontier. R&D aimed at producing these facilities has been under way for more than 10 years. This paper will review experimental results from MuCool, MERIT, and MICE and indicate the extent to which they will provide proof-of-principle demonstrations of the key technologies required for a Neutrino Factory or Muon Collider. Progress in constructing components for the MICE experiment will be described.
BNL, Upton, Long Island, New York
In the past few years, there have been a number of advances in the design and supporting R&D for a machine to cool, accelerate and collide TeV muon beams. This talk will review progress and discuss how such a machine might evolve from programs to build high intensity proton sources and neutrino factories.
Fermilab, Batavia
Muons, Inc, Batavia
We have developed a new method for capture, bunching and phase-energy rotation of secondary beams from a proton source, using high-frequency rf systems. The method is the baseline for muon capture in the International scoping study for a neutrino factory. In this method, a proton bunch on a target creates secondaries that drift into a capture transport channel. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to (nearly) equal central energies, and initiates ionization cooling. For the International Design Study the method must be optimized for performance and cost, and variations will be explored. In this paper we present results of optimization and variation studies toward obtaining the maximum number of muons for a neutrino factory, as well as for a future muon collider.
BNL, Upton, Long Island, New York
Funding: This work supported by the U.S. Department of Energy, contract no. DE-AC02-98CH10886.
Beam cooling for a future neutrino factory or muon collider requires high gradient rf cavities in the presence of strong magnetic fields. Experimental measurements suggested that the maximum accelerating gradient drops as the axial magnetic field increases. Little is known about the explicit dependence of the gradient on the strength of the magnetic field. The experimental observation of dark currents arising from local regions with enhanced surface field intensities under external magnetic fields however, suggests a new possible mechanism of breakdown based on electron field emission. A model of magnetic field breakdown is proposed. We illustrate that the field emitted electrons are focused by the external fields into small spots on the other side of the cavity and estimate the energy density they deliver to the wall. We show that this energy increases with the magnetic field, and this may lead to melting of the cavity surface. The influence of local fields at the emitter side is discussed and the extent to which space-charge affects this process is investigated. Results of our model are compared with recent experimental data from the 201 MHz and 805 MHz cavities.
Fermilab, Batavia
Muons, Inc, Batavia
CERN, Geneva
Funding: supported in part by USDOE STTR Grant DE-FG02-08ER86350
The great advantage of the helical ionization cooling channel (HCC) is its compact structure that enables the fast cooling of muon beam 6-dimensional phase space. This compact aspect requires a high average RF gradient, with few places that do not have cavities. Also, the muon beam is diffuse and requires an RF system with large transverse and longitudinal acceptance. A traveling wave system can address these requirements. First, the number of RF power coupling ports can be significantly reduced compared with our previous pillbox concept. Secondly, by adding a nose on the cell iris, the presence of thin metal foils traversed by the muons can possibly be avoided. We show simulations of the cooling performance of a traveling wave RF system in a HCC, including cavity geometries with inter-cell RF power couplers needed for power propagation.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC, under Contract No. DE-AC02- 07CH11359 with the U.S. Department of Energy.
Recently developed, the Superconducting Radio Frequency (SRF) Accelerator Test Facilities at Fermilab supports the International Linear Collider (ILC), High Intensity Neutrino Source (HINS), a new high intensity injector (Project X) and other future machines. These facilities; Meson Detector Building and New Muon Lab (NML) have very different foundations, structures, relative elevations with respect to grade level and surrounding soil composition. Also, there are differences in the operating equipment and their proximity to the primary machine. All the future machines have stringent operational stability requirements. The present study examines both near-field and ambient vibration in order to develop an understanding of the potential contribution of near-field sources (e.g. compressors, ultra-high and standard vacuum equipment, klystrons, modulators, utility fans and pumps) and distant noise sources to the overall system displacements. Facility vibration measurement results and methods of possible isolation from noise sources are presented and discussed.
Fermilab, Batavia
Run II has been ongoing since 2001. Peak luminosities in the Tevatron have increased from approximately 10×1030 cm-2ses-1 to 300×1030 cm-2ses-1 a factor of 30 improvement. A significant contributing factor in this remarkable progress is a greatly improved antiproton production capability. Since the beginning of Run II, the average antiproton accumulation rate has increased from 2×1010 p/hr to about 24×1010 p/hr. Peak antiproton stacking rates presently exceed 25×1010 p/hr. The antiproton stacking rate has nearly doubled in the last two years alone. A variety of improvements have contributed to the recent progress in antiproton production. The process of transferring antiprotons to the Recycler Ring for subsequent transfer to the collider has been significantly restructured and streamlined, allowing more time to be utilized for antiproton production. Improvements to the target station have greatly increased the antiproton yield from the production target. The performance of the Antiproton Source stochastic cooling systems has been enhanced by improvements to the cooling electronics, accelerator lattice optimization, and improved operating procedures.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Since 2005, the Recycler has become the sole storage ring for antiprotons used in the Tevatron Collider. The operational role of the Antiproton Source has shifted exclusively towards producing antiprotons for periodic transfers to the Recycler. The process of transferring the antiprotons from the Accumulator to the Recycler has been greatly improved, leading to a dramatic reduction in the transfer time. The reduction in time has been accomplished with a net improvement in transfer efficiency and an increase in average stacking rate. This paper will describe the software improvements that streamlined the transfer process and other changes that contributed to a significant increase in the number of antiprotons available to the Collider.
KEK, Ibaraki
The kicker of the damping ring for the International linear collider(ILC) requires fast rise/fall times(3 or 6ns) and high repetition rate(3 MHz). A multiple strip-line kicker system is developing to realize the specification*. We present results of the beam test at KEK-ATF by the strip-line kicker**. The multi-bunch beam, which has 5.6ns bunch spacing in the damping ring, is extracted with 308ns duration. Two units of the strip-line electrodes are used to extract the beam. The scheme of the beam extraction is same as the kicker of the ILC. A bump orbit and an auxiliary septum magnet are used with the kicker to clear the geometrical restriction.
*T. Naito et. al., Proc. of PAC07, pp2772-2274
**T. Naito et. al., Proc. of EPAC08, pp601-603
UMiss, University, Mississippi
The international Muon Ionization Cooling Experiment (MICE) is being built at the Rutherford Appleton Laboratory (RAL), to demonstrate the feasibility of ionization cooling of muon beams. This is one of the major technological steps needed towards the development of a muon collider and a "neutrino factory" based on muon decays in a storage ring. MICE will use particle detectors to measure the cooling effect with high precision, planning to achieve an absolute accuracy on the measurement of emittance of 0.1% or better. The particle i.d. detectors and tracker must work under harsh environmental conditions due to high magnetic fringe fields and RF noise. We will describe the MICE particle i.d. detector systems, and show some current performance measurements of these detectors.
Diversified Technologies, Inc., Bedford, Massachusetts
Funding: Funding by U.S. Department of Energy SBIR program.
Diversified Technologies, Inc. (DTI) has developed high power, solid-state Marx Bank modulators for a range of accelerators and colliders. We estimate the Marx topology can deliver equivalent performance to conventional designs, while reducing system costs by 25-50%. In this paper DTI will describe the application of Marx based technology to a long-pulse (140 kV, 160 A, 1.5 ms) modulator design focused on the International Linear Collider. The primary engineering challenge is minimizing the overall size and cost of the storage capacitors in the modulator. Unique choices in components and controls are needed, including the use of electrolytic capacitors. This paper will review recent progress in the development and testing of this long pulse Marx modulator built under a U.S. Department of Energy Phase II SBIR grant.
STFC/RAL, Chilton, Didcot, Oxon
Exeter University, Exeter, Devon
Gericke LTD, Ashton-under-Lyne
This paper describes the potential of fluidised powdered material for use as a particle production target in high power particle accelerator based facilities. In such facilities a multi-MW proton beam is required to interact with a dense target material in order to produce sub-atomic particles, e.g. neutrons for a neutron source or pions for a so-called conventional neutrino beam, a neutrino factory or a muon collider. Experience indicates that thermal transport, shock wave and radiation damage will limit the efficiency and reliability of facilities utilising solid targets at around 1 MW beam power. Consequently liquid mercury has been adopted as the target technology for the latest neutron facilities SNS and J-SNS at ORNL and Tokai respectively, and is the baseline for a neutrino factory and muon collider. However mercury introduces new problems such as Cavitation Damage Erosion. This paper discusses how a fluidised powder target may combine many of the advantages of a liquid metal with those of a solid, and describes an experimental programme at RAL currently underway to implement this technology.
Fermilab, Batavia
CERN, Geneva
IHEP Protvino, Protvino, Moscow Region
INFN-Ferrara, Ferrara
PNPI, Gatchina, Leningrad District
BNL, Upton, Long Island, New York
Università dell'Insubria & INFN Milano Bicocca, Como
Enrico Fermi Institute, University of Chicago, Chicago, Illinois
Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
Bent-crystal channeling is a technique with a potential to increase the beam-halo collimation efficiency at high-energy colliders. First measurements at the Tevatron in 2005 have shown that using a 5-mm silicon crystal to deflect the proton beam halo onto a secondary collimator improves the system performance by reducing the machine impedance, beam losses in the collider detectors and irradiation of the superconducting magnets, all in agreement with simulations. Recent results, obtained with substantially improved goniometer and enhanced beam diagnostics, are reported showing channeling collimation of the ~1-TeV circulating proton beam halo at the Tevatron collider. Comprehensive results of computer modeling are presented which allow further developments of the T-980 experiment towards a robust system compatible with requirements to high-efficient collimation at the Tevatron and LHC hadron colliders.
SLAC, Menlo Park, California
This talk will summarize progress towards high-gradient accelerator structures for a future multi-TeV linear collider. The research summarized will include the US high gradient research collaboration and the CLIC research program, and will include recent experimental results of testing a variety of accelerator structures with different frequencies, geometries and materials, and features that allow for wake field damping. The talk also presents the results of specialized material studies geared towards the understanding of surface fatigue limits due to high magnetic fields, and progress on the theory of rf breakdown in high vacuum structures and multipactoring in dielectric loaded structures.
BINP SB RAS, Novosibirsk
The influence of resonances on the beam dynamics in storage rings is of substantial interest to accelerator physics. For example, a fast crossing of resonances occurs in the damping rings of future linear colliders during the beam damping (due to the incoherent shift) can result in a loss of particles. We have studied experimentally the crossing of resonances of different power near the working point of the VEPP-4M storage ring. Observation of the beam sizes and particle losses was performed with a single-turn time resolution. Comparison with the numerical simulation has been made and will be presented alongside the experimental results.
BNL, Upton, Long Island, New York
Fermilab, Batavia
Funding: Work supported by U.S. DOE under contract No DE-AC02-98CH1-886
Long-range and head-on beam-beam effects are expected to limit the LHC performance with design parameters. To mitigate long-range effects current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. To reduce the head-on beam-beam effect electron lenses were proposed for both the LHC and RHIC. We present the experimental long-range beam-beam program and report on head-on compensations studies at RHIC, which are primarily based on simulations.
CERN, Geneva
With the successful circulation of beams in the Large Hadron Collider (LHC), its vacuum system becomes the World’s largest vacuum system under operation. This system is composed of 54 km of UHV vacuum for the two circulating beams and about 50 km of insulation vacuum around the cryogenic magnets and the liquid helium transfer lines. The LHC complex is completed by 7 km of high vacuum transfer lines for the injection of beams from the SPS and their dumping. Over the 54 km of UHV beam vacuum, 48 km are at cryogenic temperature (1.9 K), the remaining 6 km are at ambient temperature and use extensively non-evaporable getter (NEG) coatings, a technology that was born and industrialised at CERN. The cryogenic insulation vacuums, less demanding technically, impress by their size and volume: 50 km and 15000 m3. Once cooled at 1.9 K, the cryopumping allows reaching pressure in the 10-4 Pa range. This paper describes the LHC vacuum system, its behaviour in presence of beams as well as the detailed actions undertaken to recover its integrity after the electrical short which happened in a quadrupole bus-bar on 19th of September 2008.
CERN, Geneva
The Large Hadron Collider (LHC) has been aligned using classical and non-standard techniques. The results have been seen on September 10th, 2008, the day when the beam made several turns in the machine with very few correctors activated. The paper will present the different steps of the alignment, from the metrological measurements done during the phase of the magnets assembly to the alignment itself in the tunnel as well as the techniques used to obtain the accuracy required by the physicists. The correlation of the results of this alignment with the position of the beam seen on the BPMs by the operation team during the days the beam has circulated will be presented.
LBNL, Berkeley, California
JLAB, Newport News, Virginia
UMiss, University, Mississippi
The international muon ionization cooling experiment (MICE) requires low frequency and normal conducting RF cavities to compensate for muon beams’ longitudinal energy lost in the MICE cooling channel. Eight 201-MHz normal conducting RF cavities with conventional beam irises terminate by large and thin beryllium windows are needed. The cavity design is based on a successful prototype cavity for the US MUCOOL program. The MICE RF cavity will be operated at 8-MV/m in a few Tesla magnetic fields with 1-ms pulse length and 1-Hz repetition rate. The cavity design, fabrication, post process plans and as well as integration to the MICE cooling channel will be discussed and presented in details.
Old Dominion University, Norfolk, Virginia
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported in part by USDOE STTR Grant DE-FG02-08ER86350 Supported in part by USDOE STTR Grant DE-FG02-08ER86352 and in part by FRA DOE contract number DE-AC02-07CH11359
In earlier reports, microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments were used to investigate the mechanism of RF breakdown of tungsten, molybdenum, and beryllium electrode surfaces. Plots of remnants were consistent with the breakdown events being due to field emission, due to the quantum mechanical tunnelling of electrons through a barrier as described by Fowler and Nordheim. In the work described here, these studies have been extended to include tin, aluminium, and copper. Contamination of the surfaces, discovered after the experiments concluded, have cast some doubt on the proper qualities to assign to the metallic surfaces. However, two significant results are noted. First, the maximum stable RF gradient of contaminated copper electrodes is higher than for a clean surface. Second, the addition of as little as 0.01% of SF6 to the hydrogen gas increased the maximum stable gradient, which implies that models of RF breakdown in hydrogen gas will be important to the study of metallic breakdown
SLAC, Menlo Park, California
CERN, Geneva
KEK, Ibaraki
Funding: Work supported by the DOE under contract DE-AC02-76SF00515
As part of a SLAC-CERN-KEK collaboration on high gradient X-band structure research, several prototype structures for the CLIC linear collider study have been tested using two of the high power (300 MW) X-band rf stations in the NLCTA facility at SLAC. These structures differ in terms of their manufacturing (brazed disks and clamped quadrants), gradient profile (amount by which the gradient increases along the structure which optimizes efficiency and maximizes sustainable gradient) and HOM damping (use of slots or waveguides to rapidly dissipate dipole mode energy). The CLIC goal in the next few years is to demonstrate the feasibility of a CLIC-ready baseline design and to investigate alternatives which could bring even higher efficiency. This paper summarizes the high gradient test results from the NLCTA in support of this effort.
SLAC, Menlo Park, California
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
Funding: This work was supported by DOE contract No. DE-AC02-76SF00515 NERSC
The muon cooling cavity for Muon Collider works under strong external magnetic fields. It has been observed that this external magnetic field can enhance the multipacting activities and dark current heating. As part of a broad effort to optimize external magnetic field map and cavity shape for minimal dark current and multipacting, we use SLAC’s 3D parallel code Track3P to analyze the multipacting and dark current issues of the design. Track3P has been successfully used to predict multipacting phenomena in cavity and coupler designs. It provides unprecedented capabilities for simulating large-scale accelerator structure systems, including realistic 3D details and low turn-around times. In this paper, we present the comprehensive multipacting and dark current simulations for Muon Collider cavities.
SLAC, Menlo Park, California
CERN, Geneva
KEK, Ibaraki
Funding: This work was supported by DOE Contract No. DE-AC02-76SF00515 and used resources of NERSC supported by DOE Contract No. DE-AC02-05CH11231, and of NCCS supported by DOE Contract No. DE-AC05-00OR22725.
Normal conducting accelerator structures such as the X-Band NLC structures and the CLIC structures have been found to suffer damage due to RF breakdown and/or dark current when processed to high gradients. Improved understanding of these issues is desirable for the development of structure designs and processing techniques that improve the structure high gradient performance. While vigorous experimental efforts have been put forward to explore the gradient parameter space via high power testing, comprehensive numerical multipacting and dark current simulations would complement measurements by providing an effective probe for observing interior quantities. In this paper, we present studies of multipacting, dark current, and the associated surface heating in high gradient accelerator structures using the parallel finite element simulation code Track3P. Comparisons with the high power test of the CLIC accelerator structures will be presented.
CERN, Geneva
The Large Hadron Collider extends the present state-of-the-art in stored beam energy by 2-3 orders of magnitude. A sophisticated system of collimators is implemented along the 27 km ring and mainly in two dedicated cleaning insertions, to intercept and absorb unavoidable beam losses which could induce quenches in the superconducting magnets. 88 collimators per beam are initially installed for the so called Phase 1. An optimized strategy for the commissioning of this considerable number of collimators has been defined. This optimized strategy maximizes cleaning efficiency and tolerances available for operation, while minimizing the required beam time for collimator setup and ensuring at all times the required passive machine protection. It is shown that operational tolerances from collimation can initially significantly relaxed.
CERN, Geneva
BNL, Upton, Long Island, New York
KEK, Ibaraki
Funding: This work was supported by the European Community-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" programme (CARE, contract number RII3-CT-2003-506395).
Modern colliders bring into collision a large number of bunches per pulse or per turn to achieve a high luminosity. The long-range beam-beam effects arising from parasitic encounters at such colliders are mitigated by introducing a crossing angle. Under these conditions, crab cavities (CC) can be used to restore effective head-on collisions and thereby to increase the geometric luminosity. In this paper, we discuss the beam dynamics issues of a single global crab cavity (GCC) for both nominal LHC optics and one upgrade LHC optics.
LBNL, Berkeley, California
Funding: Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Crab cavity is proposed to compensate the geometric luminosity loss of crossing angle collision at LHC upgrade. In this paper, we report on strong-strong beam-beam simulation of crab cavity compensation at LHC using the BeamBeam3D code. Simulation results showed that using a pair of local compensation for each beam could significantly improve the beam luminosity at collision. However, this improvement could be lost with random offset errors from the RF deflection cavities.
Texas A&M University, College Station, Texas
Funding: DOE grant DE-FG02-06ER41405.
A conceptual design is presented for a 100 TeV proton-antiproton collider consisting of a single storage ring based upon 16.5 T dipoles, installed in the 83 km circumference SSC tunnel, fed using a proportionately expanded antiproton source. Provisions have been designed to intercept synchrotron light on room-temperature photon stops and to suppress electron cloud effect using a continuous clearing electrode running throughout the collider. Beams would be separated using split dipoles so that 20 ns bunch spacing should be attainable. Synchrotron damping time of half-hour would help to stabilize against mechanisms for slow emittance growth. It is reasonable to project the potential for a luminosity of 1035/cm2/s.
KEK, Ibaraki
Beam-beam tune shift parameter characterizes the strength of the nonlinear interaction due to the beam-beam collision. The tune shift has been measured in many e+e- colliders and has been an indicator for the collider performance. The record for the tune shift is known as 0.07-0.1 depending on the parameter of the collider, especially the radiation damping rate. We discuss the fundamental limit of the tune shift can be very high (>0.2) depending on the choice of collider parameter, which concerns operating point near the half integer tune, head-on collision and travel focus.
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.
Muons, Inc, Batavia
Northern Illinois University, DeKalb, Illinois
Funding: Supported in part by the Illinois Department of Commerce and Economic Opportunity
Detector designs for muon colliders have lacked coverage of the particles emerging from the collision region in the forward and backward angular regions, limiting their physics potential. These regions require massive shielding, mainly due to the intense radiation produced by the decay electrons from the muon beams. Emerging technologies for instrumentation could be used to detect particles in these regions that were filled with inert material in previous designs. New solid state photon sensors that are fine-grained, insensitive to magnetic fields, radiation-resistant, fast, and inexpensive can be used with highly segmented detectors in the regions near the beams. We are developing this new concept by investigating the properties of these new sensors and including them in numerical simulations to study interesting physics processes and backgrounds to improve the designs of the detector, the interaction region, and the collider itself.
BINP SB RAS, Novosibirsk
INFN/LNF, Frascati (Roma)
KEK, Ibaraki
A novel scheme of crab waist collisions has been successfully tested at the electron-positron collider DAΦNE, Italian Phi-factory. In this paper we compare numerical simulations of the crab waist beam-beam interaction with obtained experimental results. For this purpose we perform weak-strong and quasi strong-strong beam-beam simulations using a realistic DAΦNE lattice model that has proven to reproduce reliably both linear and nonlinear collider optics.
BNL, Upton, Long Island, New York
Funding: Work performed under the auspices of the US DOE.
In the recent years the peak luminosity of the RHIC polarized proton run has been improved. However, as a consequence, the luminosity lifetime is reduced. The beam emittance growth during the beam storage is a main contributor to the luminosity lifetime reduction, and it seems to be caused mainly by the beam-beam effect during collision. It is, therefore, important to better understand the beam-beam collision effects in RHIC with the aid of particle tracking codes. A simulation study of the emittance growth is performed with RHIC machine parameters using the LIFETRAC code*. The initial results of this study were reported in an earlier paper**. In order to achieve a better understanding and to provide guidance for future RHIC operations, we present an in depth investigation of the emittance growth for a range of RHIC operation tunes, bunch lengths and initial emittance. The simulation results are also compared to the available data from experimental measurements.
*D.Shatilov, et al.,"Lifetrac Code for the Weak-Strong Simulation of the Beam-Beam Effects in Tevatron",PAC05 proc.
**J.Beebe-Wang,“Emittance Growth due to Beam-Beam Effect in RHIC”,PAC07 Proc.
FZJ, Jülich
IKP, Mainz
ELSA, Bonn
BNL, Upton, Long Island, New York
DELTA, Dortmund
The feasibility of a polarized Electron-Nucleon Collider (ENC) with a center-of-mass energy up to 13.5 GeV for luminosities above 2·1032 cm-2 s-1 is presently under consideration. The proposed concept integrates the planned 14 GeV High-Energy Storage Ring (HESR) for protons/deuterons and an additional 3 GeV electron ring. Calculations of cooled beam equilibria including intra-beam scattering and beam-beam interaction have been performed utilizing the BetaCool code. A special design of the interaction region is required to realize back-to-back operation of the HESR storage ring together with the elaborated collider mode. For polarized proton/deuteron beams additional equipment has to be implemented in several machines of the acceleration chain and the HESR to preserve the beam’s polarization. A scheme for polarized electrons is still under investigation. In this presentation the required modifications and extensions of the HESR accelerator facility at the future International Facility for Antiproton and Ion Research (FAIR) are discussed and the proposed concept is presented.
JLAB, Newport News, Virginia
Muons, Inc, Batavia
Designers of high-luminosity energy-frontier muon colliders must provide strong beam focusing in the interaction regions. However, the construction of a strong, aberration-free beam focus is difficult and space consuming, and long straight sections generate an off-site radiation problem due to muon decay neutrinos that interact as they leave the surface of the earth. Without some way to mitigate the neutrino radiation problem, the maximum c.m. energy of a muon collider will be limited to about 3.5 TeV. A new concept for achromatic low beta design is being developed, in which the interaction region telescope and optical correction elements, are installed in the bending arcs. The concept, formulated analytically, combines space economy, a preventative approach to compensation for aberrations, and a reduction of neutrino flux concentration. An analytical theory for the aberration-free, low beta, spatially compact insertion is being developed.
JLAB, Newport News, Virginia
LBNL, Berkeley, California
Funding: (1) Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 (2) Supported by the U. S. Department of Energy under Contract no. DE-AC02-05CH11231.
The collective beam-beam effect can potentially cause a rapid growth of beam sizes and reduce the luminosity of a collider to an unacceptably low level. The ELIC, a proposed ultra high luminosity electron-ion collider based on CEBAF, employs high repetition rate crab crossing colliding beams with very small bunch transverse sizes and very short bunch lengths, and collides them at up to 4 interaction points with strong final focusing. All of these features can make the beam-beam effect challenging. In this paper, we present simulation studies of the beam-beam effect in ELIC using a self-consistent strong-strong beam-beam simulation code developed at Lawrence Berkeley National Laboratory. This simulation study is used for validating the ELIC design and for searching for an optimal parameter set.
JAI, Oxford
ATOMKI, Debrecen
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
We present the results of beam tests of the FONT4 ILC prototype intra-train beam feedback system. The system comprises a stripline BPM, a fast analogue BPM signal processor, a custom FPGA-based digital feedback board, a high-power fast-response drive amplifier, and a stripline kicker. The hardware was deployed at the Accelerator Test Facility at KEK. Trains comprising three electron bunches were extracted from the ATF damping ring, with bunch spacing c. 150ns. The feedback loop was closed by measuring the position of bunch 1 and correcting bunches 2 and 3. We report the performance of the feedback, including gain studies, the correction dynamic range, latency measurement, and quality of the beam position correction. The system achieved micron-level bunch stabilisation with a latency of c. 140ns.
SLAC, Menlo Park, California
CERN, Geneva
Funding: Work supported by the DOE under contract DE-AC02-76SF00515.
Plasma Wake-Field Acceleration (PWFA) has demonstrated acceleration gradients above 50 GeV/m. Simulations have shown drive/witness bunch configurations that yield small energy spreads in the accelerated witness bunch and high energy transfer efficiency from the drive bunch to the witness bunch, ranging from 30% for a Gaussian drive bunch to 95% for bunch with triangular shaped longitudinal profile. These results open the opportunity for a linear collider that could be compact, efficient and more cost effective than the present microwave technologies. A concept of a PWFA-based Linear Collider (PWFA-LC) has been developed by the PWFA collaboration. Here we will describe the conceptual design and optimization of the drive beam, which includes the drive beam linac and distribution system. We apply experience of the CLIC drive beam design and demonstration in the CLIC Test Facility (CTF3) to this study. We discuss parameter optimization of the drive beam linac structure and evaluate the drive linac efficiency in terms of the drive beam distribution scheme and the klystron / modulator requirements.
SLAC, Menlo Park, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
USC, Los Angeles, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515.
Plasma Wake-Field Acceleration (PWFA) has demonstrated acceleration gradients above 50 GeV/m. Simulations have shown drive/witness bunch configurations that yield small energy spreads in the accelerated witness bunch and high energy transfer efficiency from the drive bunch to the witness bunch, ranging from 30% for a Gaussian drive bunch to 95% for shaped longitudinal profile. These results open the opportunity for a linear collider that could be compact, efficient and more cost effective that the present microwave technologies. A concept of a PWFA-based Linear Collider (PWFA-LC) has been developed and is described in this paper. The scheme of the drive beam generation and distribution, requirements on the plasma cells, and optimization of the interaction region parameters are described in detail. The research and development steps, necessary for further development of the concept, are also outlined.
SLAC, Menlo Park, California
Funding: Work supported by the DOE under contract DE-AC02-76SF00515.
Optimization of Interaction Region parameters of a TeV energy scale linear collider has to take into account constraints defined by phenomena such as beam-beam focusing forces, beamstrahlung radiation, and hour-glass effect. With those constraints, achieving a desired luminosity of about 2·1034 would require use of e+e- beams with about 10 MW average power. It is shown in this paper that application of the ‘‘travelling focus'' regime [V.Balakin, 1991] may allow reduction of required beam power by at least a factor of two, helping cost reduction of the collider, while keeping the beamstrahlung energy loss reasonably low. The technique is illustrated in application to 500 GeV CM parameters of the International Linear Collider. Application of this technique may also in principle allow recycling the e+e- beams and/or recuperation of their energy.
DESY, Hamburg
SLAC, Menlo Park, California
Funding: Work supported in part by the DOE under contract DE-AC02-76SF00515.
Different scenario of a start-up with international linear collider (ILC) are under discussion at the moment in the framework of the Global Design Effort (GDE). One of them assumes construction of the ILC in stages from some minimum CM energy up to final target of 500 GeV CM energy. Gamma-gamma collider with CM energy of 180GeV is considered as a candidate for the first stage of the facility. In this report we present conceptual design of a free electron laser as a source of primary photons for the first stage of ILC.
LLNL, Livermore, California
SLAC, Menlo Park, California
A high energy photon-photon collider can be created by the combination of electron linear accelerators with terawatt peak power lasers to create high energy photon beams through Commpton backscattering. The realization of this option requires of order 10kW of average laser power if each laser pulse is used once and discarded. Proposals for recirculating cavities to allow the laser light to be reused open the potential for laser systems with much lower required average power. We review the current status of laser technology and it's ability to realize a photon collider system.
Muons, Inc, Batavia
Fermilab, Batavia
Funding: Supported in part by DOE STTR grant DE-FG02-05ER86252
Earlier studies on the front end of a neutrino factory or muon collider have relied on a single simulation tool, ICOOL. We present here a cross-check against another simulation tool, G4beamline. We also perform a study in economizing the number of RF cavity frequencies and gradients. We conclude with a discussion of future studies.
Fermilab, Batavia
Muons, Inc, Batavia
Northern Illinois University, DeKalb, Illinois
Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86282 and by FRA under DOE Contract DE-AC02-07CH11359
MANX is a six-dimensional muon ionization cooling demonstration experiment based on the concept of a helical cooling channel in which a beam of muons loses energy in a continuous helium or hydrogen absorber while passing through a special superconducting magnet called a helical solenoid. The goals of the experiment include tests of the theory of the helical cooling channel and the helical solenoid implementation of it, verification of the simulation programs, and a demonstration of effective six-dimensional cooling of a muon beam. We report the status of the experiment and in particular, the proposal to have MANX follow MICE at the Rutherford-Appleton Laboratory (RAL) as an extension of the MICE experimental program. We describe the economies of such an approach which allow the MICE beam line and much of the MICE apparatus and expertise to be reused.
Muons, Inc, Batavia
JLAB, Newport News, Virginia
Funding: Supported in part by USDOE STTR Grant DE-FG02-05ER86253
Muon collider luminosity depends on the number of muons in the storage ring and on the transverse size of the beams in collision. Six-dimensional cooling schemes now being developed will reduce the longitudinal emittance of a muon beam so that smaller high frequency RF cavities can be used for later stages of cooling and for acceleration. However, the bunch length at collision energy is then shorter than needed to match the interaction region beta function. New ideas to shrink transverse beam dimensions by lengthening each bunch (reverse emittance exchange and bunch coalescing) will help achieve high luminosity in muon colliders with fewer muons. Analytic expressions for the reverse emittance exchange mechanism are derived, including a new resonant method of beam focusing. Correction schemes for the aberrations were explored, and a lattice to implement them was proposed. To mitigate space charge detuning and wake field effects, a scheme was invented to coalesce smaller intensity bunches after they are cooled and accelerated to high energy into intense bunches suitable for a muon collider.
Muons, Inc, Batavia
Fermilab, Batavia
Intense muon beams have many potential applications. However, muons originate from a tertiary process that produces a diffuse swarm. To make useful beams, the swarm must be rapidly collected and cooled before the muons decay. A promising new concept for the collection and cooling of muon beams to increase their intensity and reduce their emittances is investigated: the use of a nearly isochronous helical cooling channel (HCC) to facilitate capture of the muons into a few RF bunches. Such a distribution could be cooled quickly and then coalesced efficiently into a single bunch to optimize the luminosity of a muon collider. An analytical description of the method is presented followed by simulation and optimization studies. Practical design constraints and integration into a collider, neutrino factory or intense beam scenario are discussed and plans for further studies are addressed.
UCLA, Los Angeles, California
We describe the Li Lens concept for a cooler for the transverse emittance for a μ+μ- collider. Different configurations are discussed such as Linear Cooler, Ring Coolers all with Li Lens inserts. We then describe a program to study the construction of Liquid Li Lens and a possible experiment at FNAL.
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
Funding: DOE
A study of target parameters for a high-intensity, liquid mercury jet target system for a neutrino factory or muon collider is presented. Using the MARS code, we simulate particle production initiated by incoming protons with kinetic energies between 2 and 100 GeV. For each proton beam energy, we optimize the geometric parameters of the target: the mercury jet radius, the incoming proton beam angle, and the crossing angle between the mercury jet and the proton beam. The number of muons surviving through an ionization cooling channel is determined as a function of the proton beam energy
STFC/RAL, Chilton, Didcot, Oxon
Exeter University, Exeter, Devon
Gericke LTD, Ashton-under-Lyne
This paper proposes a technology based on fluidized powder which could be employed as a high power target (and beam dump), for example in a future Neutrino Factory or Muon Collider. A fluidized powder target is believed to bring together some advantages of both the solid and liquid phase whilst avoiding some of their drawbacks. The current Neutrino Factory and Muon Collider proposals require the use of a high Z target material withstanding beam ionisation heating of around 1 MW. The article proposes to use a dense tungsten powder jet as an alternative to the baseline open mercury jet for interaction with the proton beam inside the high field capture solenoid. The preliminary experimental results on the production and on the characteristics of a dense horizontal tungsten powder jet are presented. The morphology of the jet is analysed and presented as a function of the driving parameters (e.g. pneumatic supply pressure, boundary conditions of the jet, etc.). A test rig was developed to investigate the reliability of lean and dense phase pneumatic conveying of tungsten powder and the results of such experiments are discussed in the paper.
UNIFE, Ferrara
INFN-Ferrara, Ferrara
Channeling in bent crystals is a technique with high potential to steer charged-particle beams for several applications in accelerators physics. Channeling and related techniques underwent significant progress in the last years. Distinctive features of performance increase was the availability of novel ideas other than new techniques to manufacture the crystal for channeling. We show the technology to fabricate crystals through non conventional silicon micromachining techniques. Characterization of the realized crystals highlighted that the crystals are free of lattice damage induced by the preparation. The crystals were positively tested at the external line H8 of the SPS with 400 GeV protons for investigation on planar and axial channelings as well as on single and multiple volume reflection experiments by the H8-RD22 collaboration. Selected single- and multi-crystal are candidates for the experiment UA9–an experiment on beam collimation at the CERN SPS.
IAP/RAS, Nizhny Novgorod
A new two-beam accelerating structure based on periodic chain of rectangular shape multi-mode cavities was suggested recently*. The structure is aimed to increase threshold breakdown surface field and thus to provide a high gradient. This threshold increase is to be brought about by designing cavities of the structure to operate simultaneously in several harmonically-related TMn,n,0 modes, thereby reducing the effective exposure time of the cavity surface to the peak fields. The more number of the operating modes is the more reduction of the exposure time. Unfortunately, a big amount of modes leads to limitation for cavity length and practical limitation of filling factor. In order to avoid this, it is suggested to operate with several TMn,n,l modes with non-zero longitudinal indices. These modes are able to provide the long interaction of a moving bunch with RF fields along the cavity. Such regime requires for the longitudinal index l to be strictly proportional the mode frequency. A cylindrical shape cavity design is also considered.
*S.V. Kuzikov, S.Yu. Kazakov, M.E. Plotkin, J.L. Hirshfield, High-Gradient Multi-Mode Two-Beam Accelerating Structure, Proc. of EPAC’08 Conf., Genoa, June 23-27, 2008, WEPP133.
LBNL, Berkeley, California
Funding: Supported by the Office of Science, Office of High Energy Physics, of the U.S. DOE under Contract No. DE-AC02-05CH11231.
Laser-driven plasma-based accelerators have made rapid progress in the last several years, yielding high-quality GeV electron beams accelerated over several centimeters.* Due to the ultra-high accelerating gradients, employing laser-plasma-accelerator technology has the potential to significantly reduce the linac length (and therefore cost) of a future lepton collider. The prospects and design considerations for a next-generation electron-positron linear collider based on laser-plasma accelerators are discussed. Staging of ultra-high gradient laser-plasma accelerating structures is examined, and plasma density scaling laws are derived for relevant collider parameters. Emittance growth via beam-plasma scattering is analyzed. An example of self-consistent parameters for a 1 TeV laser-plasma-based collider is presented.
*W.P. Leemans et al., ‘‘GeV electron beams from a centimetre-scale accelerator,'' Nature Physics 2, 696 (2006).
UCLA, Los Angeles, California
BNL, Upton, Long Island, New York
Particle Beam Lasers, Inc., Northridge
We describe preliminary study of the design of a Muon Collider using 20T Dipole Magnets such a collider could be constructed at FNAL.
UCLA, Los Angeles, California
SLAC, Menlo Park, California
Duke University, Durham, North Carolina
USC, Los Angeles, California
Funding: Work supported by DOE under contracts DE-FG03-92ER40727, DE-FG52-06NA26195, DE-FC02-07ER41500, DE-FG02-03ER54721.
Recent Plasma Wake-Field Acceleration (PWFA) experiments at Stanford Linear Accelerator Center has demonstrated electron acceleration from 42GeV to 84GeV in less than one meter long plasma section. The accelerating gradient is above 50GeV/m, which is three orders of magnitude higher than those in current state-of-art RF linac. Further experiments are also planned with the goal of achieving acceleration of a witness bunch with high efficiency and good quality. Such PWFA sections with 25 GeV energy gain will be the building blocks for a staged TeV electron-positron linear collider concept based on PWFA (PWFA-LC). We conduct Particle-In-Cell simulations of these PWFA sections at both the initial and final witness beam energies. Different design options, such as Gaussian and shaped bunch profiles, self-ionized and pre-ionized plasmas, optimal bunch separation and plasma density are explored. Theoretical analysis of the beam-loading* in the blow-out regime of PWFA and simulation results show that highly efficient PWFA stages are possible. The simulation needs, code developments and preliminary simulation results for future collider parameters will be discussed.
*M. Tzoufras et al, Phys. Rev. Lett. {10}1, 145002 (2008).
BNL, Upton, Long Island, New York
For his outstanding contribution to the design and construction of accelerators that has led to the realization of major machines for fundamental science on two continents, and his promotion of international collaboration.
CERN, Geneva
The path towards a multi-TeV e+e- linear collider proposed by the CLIC study is based on the Two Beam Acceleration scheme. Such a scheme is promising in term of efficiency, reliability and cost. The rationale behind the two-beam scheme is discussed in the paper, together with the special issues related to this technology and the R&D needed to demonstrate its feasibility.
Muons, Inc, Batavia
BNL, Upton, Long Island, New York
Funding: Work supported in part by USDOE STTR Grant DE-FG02-08ER86281 and DE AC02 98CH10886.
The U.S. muon collider community is mobilizing itself to produce a “Design Feasibility Study” (DFS) for a muon collider. This is happening on an aggressive schedule and must include the best possible simulations to support and validate the technical design. The DFS for a muon collider will require innovative new approaches to many aspects of accelerator design, and the simulations to support it will require tools with features and capabilities that are equally innovative and new. Two computer programs have emerged as the preferred and most commonly used simulation tools within the muon collider community: ICOOL (primary author: Dr. Fernow), and G4beamline (primary author: Dr. Roberts). We describe the ongoing development and testing of both tools for the DFS, including a common suite of tests to ensure that both tools give accurate and realistic results, as well as innovative user-friendly interfaces with emphasis on graphical user interfaces and windows.
Muons, Inc, Batavia
Illinois Institute of Technology, Chicago, Illinois
IIT, Chicago, Illinois
Funding: Supported in part by USDOE STTR Grant DE-FG02-06ER86281
Most computer programs that calculate the trajectories of particles in accelerators assume that the particles travel in an evacuated chamber. The development of muon beams, which are needed for muon colliders and neutrino factories and are usually required to pass through matter, is limited by the lack of user-friendly numerical simulation codes that accurately calculate scattering and energy loss in matter. Geant4 is an internationally supported tracking toolkit that was developed to simulate particle interactions in large detectors for high energy physics experiments, and includes most of what is known about the interactions of particles and matter. Geant4 has been partially adapted in a program called G4beamline to develop muon beam line designs. The program is now being developed and debugged by a larger number of accelerator physicists studying muon cooling channel designs and other applications. Space-charge effects and muon polarization are new features that are being implemented.
BNL, Upton, Long Island, New York
The outer circumference of a BPM button and the inner circumference of the button housing comprise a transmission line. This transmission line typically presents an impedance of a few tens of ohms to the beam, and couples very weakly to the 50 Ω coaxial transmission line that comprises the signal path out of the button. The modes which are consequently excited and trapped often have quality factors of several hundred, permitting resonant excitation by the beam. The combination of short bunches and high currents found in modern light sources and colliders can result in the deposition of tens of watts of power in the buttons. The resulting thermal distortion is potentially problematic for maintaining high precision beam position stability, and in the extreme case can result in mechanical damage. We present here a simple algorithm that uses the input parameters of beam current, bunch length, button diameter, beampipe aperture, and fill pattern to calculate a figure-of-merit for button heating. Data for many of the world’s light sources and colliders is compiled in a table.
BNL, Upton, Long Island, New York
Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
RHIC BPM system average orbit was originally calculated by averaging positions of 10000 consecutive turns for a single selected bunch. Known perturbations in RHIC particle trajectories, with multiple frequencies around 10 Hz, contribute to observed average orbit fluctuations. In 2006, the number of turns for average orbit calculations was made programmable; this was used to explore averaging over single periods near 10 Hz. Although this has provided an average orbit signal quality improvement, an average over many periods would further improve the accuracy of the measured closed orbit. A new continuous average orbit calculation is currently under development and planned for use in the 2009 RHIC run. This paper will discuss the algorithm, performance with a simulated beam signal, and beam measurements.
INFN/LNF, Frascati (Roma)
Università degli Studi di Firenze, Firenze
INOA, Firenze
VIGO System S.A., Ozarow Maz.
At the LNF (Laboratori Nazionali di Frascati) of the INFN a novel diagnostics experiment has been set-up to monitor the real time bunch behavior in the positron ring of the DAΦNE collider. The experiment has been installed on a bending magnet exit port of the e+ ring. The front-end consists of a UHV chamber where a gold-coated plane mirror deflects the radiation through a ZnSe window. After the window, a compact optical layout in air focuses the radiation on an IR detector. Compact mid-IR fast uncooled HgCdTe photodiodes are used to measure the bunch by bunch emission. A preliminary alignment of the mirrors and a first characterization of the radiation emitted have been performed. Longitudinal measurements of the bunch behavior, both in time and in frequency domain, obtained with fast IR detectors are presented. This novel diagnostics now available is ready to allow monitoring in real time of the bunch-by-bunch positron emission. It has been designed to improve the DAΦNE diagnostics with the main aim to identify and characterize positron bunch instabilities in the longitudinal plane. Developments for extending detection capability in the transverse planes are in progress.
Kyungpook National University, Daegu
Royal Holloway, University of London, Surrey
KEK, Ibaraki
PAL, Pohang, Kyungbuk
UCL, London
SLAC, Menlo Park, California
Fermilab, Batavia
CHEP, Daegu
University of Cambridge, Cambridge
The ATF2 international collaboration is intending to demonstrate nanometer beam sizes required for the future Linear Colliders. The position of the electron beam focused down at the end of the ATF2 extraction line to a size as small as 35 nm has to be measured with nanometer resolution. For that purpose a special Interaction Point(IP) beam position monitor (BPM) was designed. In this paper we report on the features of the BPM and electronics design providing the required resolution. We also consider the results obtained with BPM triplet which was installed in the ATF beamline and the first data from ATF2 commissioning runs.
Muons, Inc, Batavia
Northern Illinois University, DeKalb, Illinois
Funding: Supported in part by the Illinois Department of Commerce and Economic Opportunity
The multi-pixel photon counter (MPPC), or Geiger-mode avalanche photo-diode (GM-APD), also known as silicon photomultiplier (SiPM) is of great interest as a photon detector for high-energy physics scintillation counters, and other applications. In this paper we discuss some of the performance characteristics of MPPCs, and several applications, namely for muon cooling experiments, rare muon decay modes, and collider detectors. In addition we will discuss advances in signal processing electronics for MPPCs, which further enhance their use for large-scale applications.
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
KEK, Ibaraki
LAL, Orsay
SLAC, Menlo Park, California
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).
CLIC is one of the current projects of linear colliders. Achieving a vertical beam size of 1 nm at the Interaction Point (IP) with several nanometers of fast ground motion imposes an active stabilization of final doublet magnets (FD) at a tenth of nm above 4Hz. ATF2 is a test facility for linear colliders whose first aim is to have a vertical beam size of 37nm. Relative motion tolerance between FD and the IP is of 7nm above 0.1Hz. Because ground motion is coherent between these two elements, they were fixed to the floor so that they move in a coherent way. Investigations are going on to have in 2011 a useful active stabilization for ATF2 in order to use it as a CLIC prototype. Parameters of a 2D ground motion generator were fitted on measurements to reproduce spatial and temporal spectra, so it can be used for ATF2 simulations. Thus, we evaluated the ideal response function that an active stabilization FD system would need to have to improve on the present ATF2 system. Because ground motion coherence is lost with upstream magnets, we simulated the integrated vibrations at the IP to evaluate the usefulness of their stabilization. These results were validated with measurements.
JAI, Oxford
OXFORDphysics, Oxford, Oxon
Funding: Work supported by the STFC LC-ABD collaboration and the Commission of the European Communities under the 6th Framework Programme Structuring the European Research Area, contract RIDS-011899
We present the latest results on the development of a high power fibre laser system for the laser-wire project on ILC-like laser based beam diagnostics. The laser consists of a crystal oscillator at ~ 1um that can be synchronised to an external frequency reference followed by chirped pulse amplification in ytterbium doped double clad fibre. This system produces 1uJ pulses in an adjustable burst envelope at a chosen frequency. These pulses are further amplified in a large mode area rod type photonic crystal fibre, allowing amplification to high pulses energies whilst maintaining a single spatial mode. The fibre is pumped in pulsed mode by a specially commissioned 400W diode laser fixed at the absorption peak of ytterbium at 976nm, independent of pumping regime. Pumping in a pulsed mode allows the high energies required for laser-wire at MHz repetition rates to be created without the need for active cooling of the laser. The light is frequency doubled to ~500nm to achieve higher laser-wire resolution.
Fermilab, Batavia
Funding: Work supported by Fermilab, operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Recent advances in the HTS magnet technology and ionization cooling theory have re-launched the interest of the physics community in the realization of a high energy, high luminosity Muon Collider (MC). The large muon energy spread requires large momentum acceptance and the required luminosity calls for beta* in the mm range. To avoid luminosity degradation due to the hour-glass effect, the bunch length must be comparatively small. To keep the needed RF voltage inside feasible limits the momentum compaction factor must be as small as possible. Under these circumstances chromatic effects correction, energy acceptance, dynamic aperture and longitudinal motion stability are main issues of a MC design. In this paper we give an overview of various lattice designs toward a high luminosity, large energy acceptance MC currently under study at Fermilab.
Fermilab, Batavia
Funding: Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Muon collider is a promising candidate for the next energy frontier machine. In order to obtain peak luminosity of the order of 1035/cm2/s in the TeV energy range the beta function at the interaction point should be smaller than 1cm. To obtain correspondingly small bunch length with a reasonable RF voltage (within 1GV) the momentum compaction factor should be smaller than 10-4 in the momentum range ~1%. The lattice design must also provide sufficient dynamic aperture for ~20 microns normalized beam emittance and minimum possible circumference. Together these requirements present a challenge which has never been met before. We offer a solution to this problem which has the following distinctive features: i) chromatic compensation achieved with sextupoles and dispersion generating dipoles placed near the IR quadrupoles (not in a special section), ii) low value of momentum compaction factor obtained by balancing positive contribution from the arcs with negative contribution from the suppressors of the generated in the IR dispersion. Theoretical aspects and various options will be discussed.
JAI, Oxford
ATOMKI, Debrecen
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
We present the design of prototype fast beam position monitor (BPM) signal processors for use in inter-bunch beam-based feedbacks for linear colliders and electron linacs. We describe the FONT4 intra-train beam-based digital position feedback system prototype deployed at the Accelerator test facility (ATF) extraction line at KEK, Japan. The system incorporates a fast analogue beam position monitor front-end signal processor, a digital feedback board, and a fast kicker-driver amplifier. The total feedback system latency is less than 150ns, of which less than 10ns is used for the BPM processor. We report preliminary results of beam tests using electron bunches separated by c. 150ns. Position resolution of order 1 micron is obtained.
CERN, Geneva
The CLIC study is exploring the scheme for an electron-positron collider with a centre-of-mass energy of 3 TeV in order to make the multi-TeV range accessible for physics. The current goal of the project is to demonstrate the feasibility of the technology by the year 2010. Recently, important progress has has been made concerning the high-gradient accelerating structure tests and the experiments with beam in the CLIC test facility, CTF3. On the organizational side, the CLIC international collaborations have significantly gained momentum considerably boosting the CLIC study.
MIT, Middleton, Massachusetts
There are presently three initiatives for a hadron-lepton collider in the world: eRHIC at BNL, ELIC at JLab (both part of the EIC collaboration), and LHeC at CERN. This talk presents the status of these initiatives and compares their different thrusts in physics research as well as in their approach to the facility design, pointing out the strengths and limits of each particular proposal.
Fermilab, Batavia
Funding: Work supported by the United States Department of Energy under Contract No. DE-AC02-07CH11359
Over the past year Tevatron has been routinely operating at initial luminosity over 3·1032. The high luminosity regime highlighted several issues that became the focus for operational improvements. In this report we summarize the experience in such areas as mitigation of particle losses, maintaining orbit and optics stability, and identification of aperture restrictions.
Fermilab, Batavia
Funding: Work supported by the Fermi Research Alliance, under contract to the U. S. Department of Energy
As the Fermilab Collider program draws to a close, a vision has emerged of an experimental program built around the high intensity frontier. The centerpiece of this program will be a new 8 GeV superconducting H- linac which will support world leading programs in long baseline neutrino experimentation and the study of rare processes. Based on technology shared with the International Linear Collider, Project X will support the generation of multi-MW beams at 60-120 GeV from the Main Injector, simultaneous with several hundred kilowatts at 8 GeV from the Recycler. Project X will also open the possibility of a future energy frontier facility based on utilization as the front end of a muon storage ring based facility.
Fermilab, Batavia
Funding: This work was supported by the Fermi National Accelerator Laboratory, which is operated by Universities Research Association, under contract No.DE-AC02-76CH03000 with the U.S. Department of Energy
This talk will present arguments that the Neutrino Factory - an extremely intense source of flavor-tagged neutrinos from muon decays in a storage ring - gives the best physics reach for CP violation, as well as virtually all parameters in the neutrino oscillation parameter space. It will describe the physics capabilities of a baseline Neutrino Factory as compared to other possible future facilities (beta-beam and super-beam facilities), give an overview of the accelerator complex, describe the current international R&D program and present a potential time line for the design and construction of the facility. Although the baseline study focuses on a facility with muon energy of 25 GeV, a concept for a Low-Energy (~ 4 GeV) Neutrino Factory has also been developed and its physics reach will also be discussed. Finally, it will be shown that a facility of this type is unique in that it can present a physics program that can be staged, addressing exciting new physics at each step. Eventually it can lead to an energy-frontier muon collider. A muon accelerator facility is a natural extension that can exploit the high intensity potential at FNAL starting with Project X.
UCR, Riverside, California
Funding: Work supported by the United States Department of Energy under Grant No. DE-FG02-07ER41487.
The RFOFO ring is considered to be one of the most promising six-dimensional cooling channels proposed for the future Muon Collider. It has a number of advantages over other cooling channels, but also certain drawbacks. The injection and extraction, the absorber overheating, and the bunch train length are among the main issues. A number of simulations of a possible solution to these problems, the RFOFO helix, commonly referred to as the Guggenheim channel, were carried out and their results are summarized. The issue of the RF breakdown in the magnetic field is addressed, and the preliminary results of the simulation of the lattice with magnetic coils in the irises of the RF cavities are presented.
TRIUMF, Vancouver
CERN, Geneva
The simulation code COMBI has been developed to enable the study of coherent beam-beam effects in the full collision scenario of the LHC, with multiple bunches interacting at multiple crossing points over many turns. The parallel version of COMBI was first implemented using a soft-Gaussian collision model which entails minimal communication between worker processes. Recently we have extended the code to a fully self-consistent collision model using a Grid-Multipole method, which allows worker processes to exchange charge and field information in a compact form which minimizes communication overhead. In this paper we describe the Grid-Multipole technique used and its adaptation to the parallel environment through pre- and post-processing of charge and grid data. Performance measurements in multi-core and Myrinet-cluster environments will be given. We will also present our estimates of the potential for very large-scale simulations on massively-parallel hardware, in which the number of simulated bunches ultimately approaches the actual LHC bunch population.
Tech-X, Boulder, Colorado
Fermilab, Batavia
CIPS, Boulder, Colorado
Funding: US DOE, COMPASS SciDAC-2, Grant Number DE-FC02-07ER41499
We have applied the Werner-Cary method* for extracting modes and mode frequencies from time-domain simulations of crab cavities, as are needed for the ILC and the beam delivery system of the LHC. This method for frequency extraction relies on a small number of simulations and post-processing using the SVD algorithm with Tikhonov regularization. The time domain simulations were carried out using the VORPAL computational framework, which is based on the eminently scalable finite-difference time-domain algorithm. A validation study was performed on an aluminum model of the 3.9 GHz RF separators built originally at Fermi National Accelerator Laboratory in the US. Comparisons with measurements of the A15 cavity show that this method can provide accuracy to within 0.01% of experimental results after accounting for manufacturing imperfections. To capture the near degeneracies two simulations requiring in total a few hours on 600 processors were employed. This method has applications across many areas including obtaining MHD spectra from time-domain simulations.
*J. Comp. Phys. 227, 5200-5214 (2008)
USC, Los Angeles, California
UCLA, Los Angeles, California
Duke University, Durham, North Carolina
Funding: Work supported by US Department of Energy.
Plasma Wakefield Accelerator has been proven to be a promising technique to lower the cost of the future high energy colliders by offering orders of magnitude higher gradients than the conventional accelerators. However, it has been shown that ion motion is an important issue to account for in the extreme regime of ultra high intensities and ultra low emittances, characteristics of future high energy colliders. In this regime, the transverse electric field of the beam is so high that the plasma ions cannot be considered immobile at the time scale of electron plasma oscillations, thereby leading to a nonlinear focusing force. Therefore, the transverse emittance of a beam matched to the initial linear focusing will not be preserved under these circumstances. However, Vlasov equation predicts a matching profile even in the nonlinear regime. Furthermore, we extend the idea and introduce a plasma section that can match the entire beam to the mobile-ion regime of plasma. We also find the analytic solution for the optimal matching section. Simulation results will be presented.
Cockcroft Institute, Warrington, Cheshire
The prototype collimator of the ILC is simulated, to address potential issues with trapped modes and heating. A number of codes are benchmarked, and the interplay between resistive and geometric wakefields is carefully considered.
CERN, Geneva
The core task of the commissioning of the LHC technical systems was the individual test of the 1572 superconducting circuits of the collider, the powering tests. The two objectives of these tests were the validation of the different sub-systems making each superconducting circuit as well as the validation of the superconducting elements of the circuits in their final configuration in the tunnel. A wide set of software applications were developed by the team in charge of coordinating the powering activities (Hardware Commissioning Coordination) in order to manage the amount of information required for the preparation, execution and traceability of the tests. In all the cases special care was taken in order to keep the tools consistent with the LHC quality assurance policy, avoid redundancies between applications, ensure integrity and coherence of the test results and optimise their usability within an accelerator operation environment. This paper describes the main characteristics of these tools; it details their positive impact on the completion on time of the LHC Hardware Commissioning Project and presents usage being envisaged during the coming years of operation of the LHC.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
Since the start of Fermilab Collider Run II in 2001, the maximum weekly antiproton accumulation rate has increased from 400·1010 Pbars/week to approximately 3,700·1010 Pbars/week. There are many factors contributing to this increase, one of which involves changes to operational procedures that have streamlined and automated antiproton source production. Automation has been added to our beam line orbit control, stochastic cooling power level management, and RF settings. In addition, daily tuning efforts have been streamlined by implementing sequencer driven aggregates.
GSI, Darmstadt
IPCP, Chernogolovka, Moscow region
TU Darmstadt, Darmstadt
Universidad de Castilla-La Mancha, Ciudad Real
CERN, Geneva
When the LHC will work at full capacity, two counter rotating beams of 7 TeV/c protons will be generated. Each beam will consist of 2808 bunches while each bunch will comprise of 1.15x1011 protons. Bunch length will be 0.5 ns whereas two neighboring bunches will be separated by 25 ns . Intensity in the transverse direction will be Gaussian with σ = 0.2 mm. Each beam will carry 362 MJ energy, sufficient to melt 500 kg of Cu. Safety is an extremely important issue in case of such powerful beams. We report two–dimensional numerical simulations of hydrodynamic and thermodynamic response of a solid copper cylinder that is facially irradiated by one of the LHC beams in axial direction. The energy loss of protons in copper is calculated employing the FLUKA code and this data is used as input to a hydrodynamic code, BIG2. Our simulations show that the beam will penetrate up to 35 m into the solid copper target. Since the target is strongly heated by the beam, a sample of High Energy Density (HED) matter is generated. An additional application of the LHC, therefore will be, to study HED matte. This is an improvement of our previous work [Tahir et al., PRL 94 (2005) 135004].