Edinburgh University, Edinburgh
TRIUMF, Vancouver
Since the 1980s the nuclear physics community has pursued the development of intense and exotic radioactive ion beams for many areas of study including astrophysics. The myriad of radionuclides that exist fleetingly inside explosive stellar scenarios are involved in nuclear reactions which are extremely difficult to model from theory, and in these cases experimental data is crucial. The measurement problems of astrophysics often require not only the most sensitive detectors and most intense radioactive beams, but also the right combination of experimental facilities, accelerators and detectors. The community has tackled these problems in a variety of different ways, with many labs already active or coming online with new aggressive accelerator, isotope production and measurement technology ready to target the big astrophysics questions. This talk gives an overview of some experimental methods and facilities used to derive astrophysically-relevant nuclear properties and highlights the places in the world that perform these studies.
University of Pisa and INFN, Pisa
CERN, Geneva
INFN/LNF, Frascati (Roma)
SLAC, Menlo Park, California
We present an improved design of the focusing elements close to the interaction point of the SuperB accelerator. These magnets have to provide pure quadrupolar fields on each of the two beams to decrease the background rate in the detector which would be produced by the over-bend of the off-energy particles if a dipolar component were present. Very good field quality is also required to preserve the dynamic aperture of the rings. Because of the small separation of the two beams (only few centimeters) and the high gradient required by the SuperB final focus, neither a permanent magnet design nor a multi-layer configuration are viable solutions. A novel design, based on 'helical-type' windings, has therefore been investigated. In this paper we will present the improved magnetic design and its performances evaluated with a three dimensional finite element analysis.
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 completed commissioning at CERN. At four points around the 27 km ring, the beams are put into collision in the centre of the experiments ALICE, ATLAS, CMS and LHCb which are installed in large underground caverns. The ‘experimental vacuum systems’ which transport the beams through these caverns and collision points are a primary interface between machine and experiment and were developed and installed as one project at CERN. Each system has a different geometry and materials as required by the experiment. However, they all have common requirements from the machine, and use many common technologies developed for the project. In this paper we give an overview of the four systems stressing the similarities between them. We explain the technologies that were developed and applied for the installation, test, bakeout and subsequent closure of the experimental vacuum systems. We also discuss lessons learnt from the project.
IIT, Chicago, Illinois
Fermilab, Batavia
LBNL, Berkeley, California
ANL, Argonne
Funding: The United States Department of Energy
The accelerating gradient in a RF cavity is limited by many factors such as the surface material properties, RF frequency, the external magnetic field and the gas pressure inside the cavity. In the MuCool Program, RF cavities are studied with the aim of understanding these basic mechanisms and improving their maximum stable accelerating gradient. These cavities are being developed for muon ionization cooling channel for a Neutrino Factory or Muon Collider. We report studies using the 805 MHz and 201 MHz RF cavities in the MuCool Test Area (MTA) at Fermilab. New results include data from buttons of different materials mounted in the 805 MHz cavity, study of the accelerating gradient in the 201 MHz cavity and X-ray background radiation from the cavities due to Bremsstrahlung. The 201 MHz cavity has been shown to be stable at 19 MV/m at zero magnetic field, well in excess of its 16 MV/m design gradient. We will also discuss results from the 201 MHz cavity study in magnetic field and introduce the test of E × B effects with the 805 MHz box cavity.
LBNL, Berkeley, California
Funding: This work is supported by NA22 of NNSA under the Department of Energy contract No. DE-AC02-05CH11231.
Active neutron interrogation has been demonstrated to be an effective method of detecting shielded fissile material. A fast fall-time/fast pulsing neutron generator is needed primarily for differential die-away technique (DDA) interrogation systems. A compact neutron generator, currently being developed in Lawrence Berkeley National Laboratory, employs an array of 0.25-mm-dia apertures (instead of one 5-mm-dia aperture) such that gating the beamlets can be done with low voltage and a small gap to achieve sub-microsecond ion beam fall time and low background neutrons. The system will aim at both high and low beam current applications. We have designed and fabricated an array of 16 apertures (4x4) for a beam extraction experiment. Our preliminary results showed that, using a gating voltage of less than 800 V and a gap distance of 1 mm, the fall time of extracted ion beam pulses is less than 1 ms at various beam energies ranging between 200 eV to 600 eV. More experimental results with an array of 20×20 apertures will be presented.
PPPL, Princeton, New Jersey
Funding: Research supported by the U. S. Department of Energy.
This paper presents a survey of the present theoretical understanding based on advanced analytical and numerical studies of collective interactions and instabilities for intense one-component ion beams, and for intense ion beams propagating through background plasma. The topics include: discussion of the condition for quiescent beam propagation over long distances; the electrostatic Harris instability and the transverse electromagnetic Weibel instability in highly anisotropic, one-component ion beams; and the dipole-mode, electron-ion two-stream instability (electron cloud instability) driven by an unwanted component of background electrons. For an intense ion beam propagating through a charge-neutralizing background plasma, the topics include: the electrostatic electron-ion two-stream instability; the multispecies electromagnetic Weibel instability; and the effects of a velocity tilt on reducing two-stream instability growth rates. Operating regimes are identified where the possible deleterious effects of collective processes on beam quality are minimized.
NSRRC, Hsinchu
The purpose of this paper is to reduce the Electromagnetic Interference (EMI) from kicker and its pulsed power supply. Analysis of conducted and radiated EMI is the beginning mission. Different frequency range of radiated EMI was measured by different sensors. A hybrid shielding method was used to test reduction of radiated EMI. The copper and μ-metal enclosure was used on kicker magnet to prevent the radiated EMI. The reduction of electromagnetic field showed the effect of different material. Besides, the conducted EMI was also tested and eliminated by adding grounding routs. For decreasing grounding noise to other systems, the individual grounding bus was installed. The experimental results showed significant effect. In the future, TPS (Taiwan Photon Source) injection magnets will design higher performance, lower EMI than TLS (Taiwan Light Source). Therefore reducing and eliminating the interference of electromagnetic waves will be a very important issue. All the EMI prevention schemes will implement in the new project.
BNL, Upton, Long Island, New York
Funding: Work performed under Contract Number DE-AC02-98CH10886 under the auspices of the US Department of Energy.
Using the Vernier Scan (or Van der Meer Scan technique), where one beam is swept stepwise across the other while measuring the collision rate as a function of beam displacement, the transverse beam profiles, the luminosity and the effective cross section of the collision monitoring processes can be measured. Data and results from the 2005, 2006 and 2008 polarizded proton runs using different collision detectors are presented and compared.
CERN, Geneva
We discuss luminosity monitoring, optimization and absolute calibration in the LHC. Interaction rates will be continuously monitored both by detectors on the machine side as well as by the four large LHC experiments. Horizontal and vertical separation scans will be used to optimize luminosity and to measure the beam sizes in the interaction region. An application software has been developed for this purpose. We describe the procedures which have been prepared and discuss expected systematic effects which may limit the accuracy of the measurement.
Fermilab, Batavia
Funding: Work supported by Fermi Research Alliance, LLC, under contract No. DE-AC02-07CH11359 with the U.S. Department of Energy.
With a fully-operational high-efficient collimation system in the LHC, nuclear interactions of circulating protons with residual gas in the machine beam pipe can be a major sources of beam losses in the vicinity of the collider detectors, responsible for the machine-induced backgrounds. Realistic modeling of elastic and inelastic interactions of 7-TeV protons with nuclei in the vacuum chamber of the cold and warm sections of the LHC ring - with an appropriate pressure profile - is performed with the STRUCT and MARS15 codes. Multi-turn tracking of the primary beams, propagation of secondaries through the lattice, their interception by the tertiary collimators TCT as well as properties of corresponding particle distributions at the CMS and ATLAS detectors are studied in great detail and results presented in this paper.
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.
SLAC, Menlo Park, California
CERN, Geneva
INFN/LNF, Frascati (Roma)
University of Pisa and INFN, Pisa
Funding: Work supported by the Department of Energy under contract number DE-AC03-76SF00515.
We present an improved design for a Super-B interaction region. The new design minimizes local bending of the two colliding beams by separating all beam magnetic elements near the Interaction Point (IP). The total crossing angle at the IP is increased from 50 mrad to 60 mrad. The first magnetic element is a six slice Permanent Magnet (PM) quadrupole with an elliptical aperture allowing us to increase the vertical space for the beam. This magnet starts 36 cm from the Interaction Point (IP). This magnet is only seen by the Low-Energy Beam (LEB), the High-Energy Beam (HEB) has a drift space at this location. This allows the preliminary focusing of the LEB which has a smaller beta y* at the IP than the HEB. The rest of the final focusing for both beams is achieved by two super-conducting side-by-side quadrupoles (QD0 and QF1). These sets of magnets are enclosed in a warm bore cryostat located behind the PM quadrupole for the LEB. We describe this new design for the interaction region.
SLAC, Menlo Park, California
Funding: Work supported by the Department of Energy under contract number DE-AC03-76SF00515.
The PEP-II B-Factory was designed and optimized to run at the Upsilon 4S resonance (10.580 GeV with a 9 GeV e- beam and a 3.1 GeV e+ beam). The interaction region (IR) used permanent magnet dipoles to bring the beams into a head-on collision. The first focusing element for both beams was also a permanent magnet. The IR geometry, masking, beam orbits and beam pipe apertures were designed for 4S running. Even though PEP-II was optimized for the 4S, we successfully changed the center-of-mass energy (Ecm) down to the Upsilon 2S resonance and completed an Ecm scan from the 4S resonance up to 11.2 GeV. The luminosity throughout these changes remained near 1x1034 cm-2s-1 . The Ecm was changed by moving the energy of the high-energy beam (HEB). The beam energy differed by more than 20% which produced significantly different running conditions for the RF system. The energy loss per turn changed 2.5 times over this range. We describe how the beam energy was changed and discuss some of the consequences for the beam orbit in the interaction region. We also describe some of the RF issues that arose and how we solved them as the high-current HEB energy changed.
UMAN, Manchester
CERN, Geneva
Uppsala University, Uppsala
The CLIC beam delivery system focuses 1.5 TeV electron and positron beams to a nanometre-sized cross section when colliding them at the interaction point (IP). The intense focusing leads to large beam-beam effects, causing the production of beamstrahlung photons, coherent and incoherent electron-positron pairs, as well as a significant disruption of the main beam. The transport of the post-collision beams requires a minimal loss extraction line, with high acceptance for energy deviation and divergence. The current design includes vertical bends close to the IP in order to separate the charged particles with a sign opposite to the main beam into a diagnostic-equipped intermediate dump, whilst transporting the photons and the main beam to the main dump. Photon and charged particle losses on the collimators and dumps result in a complex radiation field and IP background particle fluxes. In this paper, the electromagnetic backgrounds at the IP, which arise from these losses, are calculated, and the potential impact on the detector is discussed.
CERN, Geneva
The UA9 experiment intends to assess the possibility of using bent silicon crystals as primary collimators to direct the beam halo onto a secondary absorber, thus reducing outscattering, beam losses in critical regions and radiation load. The experiment will be performed in the CERN-SPS in storage mode with a low intensity 120 GeV/c proton beam. The beam will be perturbed to create a diffusive halo as in the RD22 experiment. The setup consists of four stations. The crystal station contains two goniometers for crystals. The first tracking station houses silicon strip detectors for single particle tracking. The second tracking station contains the same kind of detectors for tracking. The two stations will allow to measure x-x' densities and collimation efficiencies with high precision. The TAL station, at 90 degrees phase advance,is a 600 mm long tungsten secondary collimator. The observables of the experiment are the collimation efficiencies, the measurement of the phase space and the cleaning efficiency deduced from the losses along the ring. We present here the layout of the experiment and the way we expect to collect data in 2009.
UCLA, Los Angeles, California
Funding: Work supported by DOE.
We report experimental observation of narrow-bandwidth pulses of coherent Cherenkov radiation produced when a sub-picosecond electron bunch travels along the axis of a hollow circular cylindrical dielectric-loaded waveguide. For an appropriate choice of dielectric structure properties and driving electron beam parameters, the device operates in a single-mode regime, producing radiation in the THz range. We present measurements showing the emission of a narrowly-peaked spectrum from a fused silica tube 1 centimeter long with sub-millimeter transverse dimensions. We discuss the agreement of this data with theoretical and computational predictions, as well as possibilities for future study and application.
CERN, Geneva
IHEP Protvino, Protvino, Moscow Region
We report on background studies for the LHC with detailed simulations. The simulations now include generation of beam-gas scattering in combination with multiturn tracking of protons. Low beta optics and available aperture files for this configuration have been used to generate loss maps according to the pressure distribution in the LHC.
KEK, Ibaraki
Osaka University, Osaka
Proton beam extinction, defined as a ratio of the residual and the pulse beam intensity, should be less than 10-9, which is one of the key requirements to realize the future muon electron conversion experiment (COMET) proposed at J-PARC. Measurement of the pulse timing structure with enough sensitivity is the first step to achieve the required extinction level. We have developed two methods for the measurements; one by using fast-extracted beam and the other by using slow-resonant-extracted beam. This paper describes the schemes and the results of the measurements*. These measurements would provide important information on the beam pulse structure to understand not only for MR beam but also the whole accelelator complex, including LINAC and booster RCS.
*Submitted on behalf of the muon working group
LANL, Los Alamos, New Mexico
NSTec, Los Alamos, New Mexico
Funding: Work supported by the United States Department of Energy, DOE contract Number: W-7405-ENG-36
Accurate and reliable beam position measurements are required to commission and operate the DARHT II Accelerator. The Beam Position Monitor (BPM) system developed for use on the DARHT II accelerator consists of 31 electro-magnetic detector assemblies, a computer network based data acquisition system, and custom analysis software. During an accelerator “shot”, each BPM uses arrays of b-dot detectors to intercept the electron beam’s changing magnetic field. Post shot analysis of the BPM data provides the beam current and position information used for steering and tuning subsequent shots. This paper will analyze the performance of the BPM system, now that several thousand beam shots have been achieved.
ORNL, Oak Ridge, Tennessee
BINP SB RAS, Novosibirsk
Funding: SNS is managed by UT-Battelle, LLC, under contract DE-AC05-00OR22725 for the U.S. Department of Energy.
A transverse phase space emittance scanner is proposed and under development for the 1-GeV H- SNS linac, using a laser beam as a slit. For a 1 GeV H- beam, it is difficult to build a slit because the stopping distance is more than 50 cm in copper. We propose to use a laser beam as an effective slit by stripping off the outer electron of the H- (making it neutral) upstream of a bend magnet and measuring the stripped component downstream of the bend magnet. The design and modeling of the system will be discussed. We are expecting to make a preliminary measurement in 2009.
ANL, Argonne
Northern Illinois University, DeKalb, Illinois
An exotic beam facility for the production of rare isotopes such as the Facility for Rare Isotope Beams (FRIB) at Michigan State University will require a high resolution fragment separator to separate isotopes of varying mass and charge. The goal of the fragment separator is to produce a high-purity beam of one rare isotope. Sources of contamination in a beam such as this are isotopes with a similar magnetic rigidity to the separated isotope and those which are produced by fragmentation in the energy degrader. This can be particularly detrimental when a contaminating isotope has a large cross section. Here we investigate beam purity as a function of the separated isotope and the type of fragment separator setup used, i.e. one stage, two stage, or one stage with gas cell branch.
INFN/LNF, Frascati (Roma)
University of Pisa and INFN, Pisa
SLAC, Menlo Park, California
The novel crab waist collision scheme under test at the DAΦNE Frascati phi-factory finds its natural application to the SuperB project, the asymmetric e+e- flavour factory at very high luminosity with low beam currents and reduced background possibly located at Tor Vergata University. The SuperB accelerator design requires a careful choice of beam parameters to reach a good trade-off between different effects. We present here simulation results for the Touschek backgrounds and lifetime obtained for the latest machine design. Distributions of the Touschek particle losses at the at the interaction region have been tracked into the detectors for further investigations. A set of collimators is foreseen to stop Touschek particles. Their position along the rings has also been studied, together with their shape optimization.
RadiaBeam, Marina del Rey
UCLA, Los Angeles, California
A Coherent Optical Transition Radiation (COTR) arising from the photo-injector electron beams spontaneous microbunching at optical frequencies has been recently observed in a number of experiments. This effect can lead to an undesirable optical background for OTR beam profile measurements at these facilities. A method to resolve this problem is proposed, based on selectively suppressing the back-scattered COTR using multiple scattering in the insertion foil. An analytical treatment of COTR dependence on the angular divergence in the radiating beam is presented, and the efficacy of the approach is illustrated with the numerical examples.
TRIUMF, Vancouver
SFU, Burnaby, BC
UBC, Vancouver, B.C.
Funding: TRIUMF receives funding via a contribution agreement through the National Research Council of Canada.
For ISAC at TRIUMF, radioactive isotopes are generated with a 500MeV proton beam. The beam power is up to 40kW and can easily melt the delicate target if too tightly focused. We protect this target by closely monitoring the distribution of the incident proton beam. There is a 3-wire scanner monitor installed near the target; these give the vertical profile and the +45 and -45 degree profiles. Our objective is to use these 3 measured projections to find the 2-D density distribution. By implementing the maximum entropy (MENT) algorithm, we have developed a computer program to realize tomographic reconstruction of the beam density distribution. Of particular concern is to make the calculation sufficiently efficient that an operator can obtain the distribution within a few seconds of the scan. As well, we have developed the technique to perform phase space reconstruction, using many wire scans and the calculated transfer matrices between them. In this paper we present details of the computer code and the techniques used to improve noise tolerance and compute efficiency.
University of Tokyo, Tokyo
KEK, Ibaraki
ICEPP, Tokyo
Commissioning of the ATF/ATF2 project will start in the winter of 2008 to 2009, with the aim of studying beam optics, diagnostic instrumentations, and tuning processes for around 35 nm beam size. The project is the realistic scaled down model of the ILC final focus system, and also, studies in the project offered important findings for future accelerator physics. In this presentation, we will present about the status of the first commissioning of the Shintake monitor for ATF2. The monitor is located at the virtual interaction point of the ATF2 (the focus point) to measure beam size. A measurable ranges as a design are from 6 micron down to 20 nm in vertical and down to several microns in horizontal. That wide range allows us to used the detector from the beginning of the beam tuning process. The monitor scheme was originally proposed by T. Shintake and verified using around 60 nm beam at FFTB project. We upgraded the detector system for ATF2 of smaller beam size and implemented a laser wire scheme for horizontal beam size measurement. These additional capabilities are also presented.
Uni HH, Hamburg
PSI, Villigen
DESY, Hamburg
CLASSE, Ithaca, New York
ITER, St Paul lez Durance
The free-electron laser FLASH and the planned European XFEL generate X-ray light pulses on the femtosecond time-scale. The feasibility of time-resolved pump-probe experiments, special diagnostic measurements and future operation modes by means of laser seeding crucially depend on the long-term stability of the synchronization of various laser systems across the facility. For this purpose an optical synchronization system is being installed and tested at FLASH. In this paper, we report on the development and the performance of a background-free optical cross-correlation scheme to synchronize two individual mode-locked lasers of different center wavelengths and repetition rates with an accuracy of better than 10 fs. The scheme can be tested by linking a Ti:sapphire oscillator, used for electro-optical diagnostics at FLASH, to both a locally installed erbium-doped fiber laser and the end-point of an actively length-stabilized fiber link distributing the pulses from a master laser oscillator. After the commissioning of this fiber link, the diagnostics laser can be synchronized to the electron beam and first accelerator based measurements on the performance of the system will be carried out.
IF-UFRGS, Porto Alegre
Non-homogeneity is a characteristic naturally present in non-neutral beams. Recently, a set of works has been developed by us for the case of beams initially homogeneous, making possible that relevant macroscopic quantities such as the RMS radius and emittance could be determined at equilibrium as functions of characteristic parameters of beam phase-space and of initial conditions. The present work intends to investigate the influences of the initial inhomogeneity in the beam route to equilibrium. Through the same methodology introduced in the studies for the homogeneous beams, both emittance and beam envelope have been obtained as functions of the magnitude of the inhomogeneity and some additional parameters associated with geometry of beam phase-space. The results obtained with this investigation have proven to be useful not only to better understand the effects of inhomogeneity over beam dynamics but also to provide physical background to the investigations previously carried out for homogeneous beams.
IF-UFRGS, Porto Alegre
Funding: This work has received financial support from AFOSR, Arlington, VA (under Grant FA9550-06-1-0345) and from CNPq, Brazil.
In the present analysis we study the self consistent propagation of intense laser pulses in a cold relativistic ideal-fluid underdense plasma, with particular interest in how the envelope dynamics is affected by the plasma frequency. Analysis of the linear system associated with the chosen model shows the existence of thresholds that can led propagating pulses to distinct modulational instabilities, according to the relation between its transversal wave vector and the plasma frequency.
USTC/NSRL, Hefei, Anhui
USTC, Hefei, Anhui
Photonic crystals have been suggested for use as laser driven particle accelerator structures with higher accelerating gradients and effective damping of unwanted higher order modes. Here we selected Photonic band gap (PBG) fibers with hollow core defects to design such an accelerating structure. To achieve this design, Out-plane-wave mode in photonic crystal fiber was selected for longitudinal electric field. The out-plane-wave plane wave expansion method was deduced for confinement and the dispersive curve versus variation of kz and speed of line for synchronization. Then super cell approximation was also introduced for calculating the defected photonic crystal structure. After the design of appropriate geometry and the dimensions of photonic crystal fiber accelerating structure, the field distribution was simulated with RSOFT Bandsolve software for this structure.
LBNL, Berkeley, California
BNL, Upton, Long Island, New York
SLAC, Menlo Park, California
CERN, Geneva
Funding: Supported by the US-DOE under Contract DE-AC02-05CH11231 and the US-LHC LARP. Used resources of NERSC, supported by the US-DOE under Contract DE-AC02-05CH11231.
Electron clouds impose limitations on current accelerators that may be more severe for future machines, unless adequate measures of mitigation are taken. Recently, it has been proposed to use feedback systems operating at high frequency (in the GHz range) to damp single-bunch transverse coherent oscillations that may otherwise be amplified during the interaction of the beam with ambient electron clouds. We have used the simulation package WARP-POSINST to study the growth rate and frequency patterns in space-time of the electron cloud driven beam breakup instability in the CERN SPS accelerator with, or without, an idealized feedback model for damping the instability. We will present our latest results and discuss their implications for the design of the actual feedback system.
TU Darmstadt, Darmstadt
CERN, Geneva
The REX-ISOLDE radioactive ion beam facility at CERN makes great demands also on the experimentalists due to its specific duty cycle and the time structure with short beam pulses and large intensities. This paper describes the experimentalist's point of view, how to obtain sufficient and correct statistics under the special circumstances arising from the beam time structure. In particular, the case of Coulomb excitation experiments, where a large total cross section is ultimately desired, is studied in greater detail.