HIT, Heidelberg, Germany
Fermilab, Batavia, USA
One of the key systems of a Muon Collider (MC)- seen as the most exciting options for the energy frontier machine in the post-LHC era - is its interaction region (IR). Designs of its optics, magnets and machine-detector interface are strongly interlaced and iterative. As a result of recent comprehensive studies, consistent solutions for the 1.5 TeV c.o.m. MC IR have been found and are described here. To provide the required momentum acceptance, dynamic aperture and chromaticity, innovative approach was used for the IR optics. Conceptual designs of large-aperture high-field dipole and high-gradient quadrupole magnets based on Nb3Sn superconductor were developed and analyzed in terms of the operation margin, field quality, mechanics, coil cooling and quench protection. Shadow masks in the interconnect regions and liners inside the magnets are used to mitigate unprecedented dynamic heat deposition due to muon decays (~1 kW/m). It is shown that an appropriately designed machine-detector interface with sophisticated shielding in the detector has a potential to substantially suppress the background rates in the MC detector.
SLAC, Menlo Park, California, USA
CERN, Geneva, Switzerland
Radio Frequency noise induced bunch lengthening can strongly affect the Large Hadron Collider performance through luminosity reduction, particle loss, and other effects. Models and theoretical formalisms demonstrating the dependence of the LHC longitudinal bunch length on the RF station noise spectral content have been presented*,**. Initial measurements validated these studies and determined the performance limiting RF components. For the existing LHC LLRF implementation the bunch length increases with a rate of 1 mm/hr, which is higher than the intrabeam scattering diffusion and leads to a 27% bunch length increase over a 20 hour store. This work presents measurements from the LHC that better quantify the relationship between the RF noise and longitudinal emittance blowup. Noise was injected at specific frequency bands and with varying amplitudes at the LHC accelerating cavities. The experiments presented in this paper confirmed the predicted effects on the LHC bunch length due to both the noise around the synchrotron frequency resonance and the noise in other frequency bands aliased down to the synchrotron frequency by the periodic beam sampling of the accelerating voltage.
*T. Mastorides et.al., "RF system models for the LHC with Application to Longitudinal Dynamics,"
**T. Mastorides et.al., "RF Noise Effects on Large Hadron Collider Beam Diffusion"
MPI-P, München, Germany
UCR, Riverside, California, USA
The Muon Ionization Cooling Experiment (MICE) is being built at the ISIS proton synchrotron at Rutherford Appleton Laboratory (RAL) to test ionization cooling of a muon beam. Production of particles in the MICE beamline begins with a titanium target dipping into the ISIS proton beam. The resulting pions are captured, momentum-selected, and fed into a 5T superconducting solenoid. This magnet contains the pions and their decay muons which are then sent through the rest of the MICE beamline toward the cooling channel. During recent data-taking, it was determined that there is a significant background contamination of neutral particles populating the MICE muon beam. This contamination creates unwanted triggers in MICE, thus reducing the percentage of useful data taken during running. This paper describes the analysis done with time-of-flight detectors, used to identify particle type, in order to understand the level of contamination in both positive and negative polarity muon beams.
The University of Texas at Austin, Austin, Texas, USA
Fermilab, Batavia, USA
For future experiments at the intensity frontier, precise and accurate knowledge of beam time structure will be critical to understanding backgrounds. The proposed Mu2e experiment will utilize ~150nsec (FWHM) bunches of 107 protons at 8 GeV with a bunch-to-bunch period of 1.7 microseconds. The out-of-bunch beam must be suppressed by a factor of 10-9 relative to in-bunch beam and continuously monitored. I propose a Cerenkov based particle telescope to measure secondary production from beam interactions in a several tens of microns thick foil. Correlating timing information with beam passage allows the determination of relative beam intensity to arbitrary precision given a sufficiently long integration time. The goal is to verify out-of-bunch extinction to the level 10-6 in the span of several seconds. This allows near real-time monitoring of the initial extinction of the beam slow extracted from Fermilab's Debuncher before a system of AC dipoles and collimators, which will provide the final extinction. The effect on beam emittance is minimal, allowing the necessary continuous measurement. I will present the detector design and results of a test in Fermilab's MI-12 beamline.
BINP SB RAS, Novosibirsk, Russia
ANL, Argonne, USA
Recently, a grazing-incidence insertion device x-ray beam position monitor (GRID-XBPM) was proposed for the intense x-ray beam from the future APS undulators [*]. By combining the function of limiting aperture with the XBPM, it increases the power-bearing capacity of the XBPM and, at the same time, eliminates the problem of relative alignment of the two critical components in the beamline. Furthermore, by imaging the hard x-ray fluorescence footprint on the collimator, the XBPM is immune to the soft x-ray background, and its accuracy is improved at larger gap settings. In addition to these advantages, the GRID-XBPM can also be implemented to measure center-of-mass of the x-ray fluorescence footprint when pinhole-camera-like optics are used for position readout*. This offers a solution for long-standing XBPM design issues for elliptical undulators, which have a donut-shaped power distribution. In this work, we report design progress for the GRID-XBPM for the high-power elliptically polarized undulator planned for the APS intermediate energy x-ray (IEX) beamline. Computer simulation of its performance and experimental tests from a scale model system will also be presented.
* B.X. Yang, G. Decker, S. H. Lee, and P. Den Hartog, Beam Instrumentation Workshop, Santa Fe, 2010, to be published.
BNL, Upton, Long Island, New York, USA
The use of fluorescent screens for beam profile monitors provides a simple and widely used way to obtain detailed two dimensional intensity maps. For high precision measurements many possible error contributions need to be considered that have to do with properties of the fluorescent screens and of the CCDs. Saturation effects, reflections within and outside the screen, non-linearities, radiation damage, etc are often mentioned. Here we concentrate on an error source less commonly described, namely erroneous baseline subtraction, which is particularly important when fitting projected images. We show computer simulations as well as measurement results having remarkable sensitivity of the fitted profile widths to even partial suppression of the profile baseline data, which often arises from large pixel-to-pixel variations at low intensity levels. Such inadvertent baseline data suppression is very easy to miss as it is usually not obvious when inspecting projected profiles. In this report we illustrate this effect and discuss possible algorithms to automate the detection of this problem as well as some possible corrective measures.
Fermilab, Batavia, USA
The Fermilab A0 Photoinjector is a 16MeV high intensity, high brightness electron Linac developed for advanced accelerator R&D. One of the key parameters for the electron beam is the transverse beam emittance. Here we report on a newly developed MATLAB based GUI program used for transverse emittance measurements using the multi-slit technique. This program combines the image acquisition and post-processing tools for determining the transverse phase space parameters with uncertainties.
LANL, Los Alamos, New Mexico, USA
URS, Albuquerque, New Mexico, USA
The Beam Diagnostics and Instrumentation Team at Los Alamos National Laboratory’s LANSCE facility is presently developing a new and improved wire scanner diagnostics system controlled by National Instrument’s cRIO platform. This report describes the current state of development of the control system along with the results gathered from the latest actuator motion performance and accelerator beam data acquisition tests.
ORNL, Oak Ridge, Tennessee, USA
Beam profile diagnostics with large dynamic range is an important tool for understanding origin and evolution of the beam halo in accelerators. Typical dynamic range for conventional wire scanners has been in the range of 100. In high power machines like SNS fractional losses of 1 to 100 part per million is of concern and, therefore, higher dynamic range of profile measurements is desirable. Our near term goal was set to achieve a dynamic range of at least 10000 for all profile measurements in the SNS linac and transport lines. We will discuss present status of this program, challenges, and solutions.
JLAB, Newport News, Virginia, USA
With inauguration of the CEBAF Element Database(CED) in Fall 2010, Jefferson Lab computer scientists have taken a first step toward the eventual goal of a model-driven accelerator. Once fully populated, the database will be the primary repository of information used for everything from generating lattice decks to booting iocs to building controls screens. A requirement influencing the CED design is that it provide access to not only present, but also future, and eventually past, configurations of the accelerator. To accomplish this, an introspective database schema was designed that allows new elements, types, and properties to be defined on-the-fly with no changes to table structure. Used in conjunction with Oracle Workspace Manager, it allows users to query data from any time in the database history with the same tools used to query the present configuration. Users can also check-out workspaces to use as staging areas for upcoming machine configurations. All Access to the CED is through a well-documented API that is translated automatically from original C++ into native libraries for script languages such as perl, php, and TCL making access to the CED easy and ubiquitous.
The U.S. Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce this manuscript for U.S. Government purposes.
University of Iowa, Iowa City, Iowa, USA
ANL, Argonne, USA
Currently, power to the APS storage ring and Booster cavities is provided from klystrons with a eventual goal to move to a solid state RF system. A modular design centered around a 1 kW amplifier has been decided on. The driver amplifier was created for this module system using Agilent’s ADS circuit simulation software and then built and tested.
BNL, Upton, Long Island, New York, USA
ORNL, Oak Ridge, Tennessee, USA
Taking advantage of modern graphical editor software technology, a new Operator Interface (OPI) editor and runtime - Best OPI, Yet (BOY) - was developed by the Control System Studio (CSS) collaboration. It uses the Eclipse Graphical Editor Framework (GEF) to provide modern graphical editor functions, which makes it easy and intuitive to edit OPIs. Combined with Javascript and configurable rules, it is also easy to create powerful OPIs with complicated client-side logic. By simply providing the name of a Process Variable (PV), it will automatically handle the network connections. The graphical layer is decoupled from the data connection layer, conceptually allowing BOY to connect to arbitrary data sources, with current support including EPICS Channel Access and simulation PVs. BOY is integrated with the CSS platform, which provides inter-operability with other CSS tools. Fundamentally, it could also be integrated with other Eclipse Rich Client Platform (RCP) applications due to its plugin mechanism. We have several screens deployed at the Spallation Neutron Source (SNS), where BOY has proven to be stable in support of SNS operation.
IHEP Beijing, Beijing, People's Republic of China
Muons, Inc, Batavia, USA
Hampton University, Hampton, Virginia, USA
Fermilab, Batavia, USA
A compact tunable gamma ray source has many potential uses in medical and industrial applications. One novel scheme to produce an intense beam of gammas relies on the ability to create a high flux of positrons, which are produced by an electron beam on a high Z target. We present an innovative system which allows for a nearly arbitrary targeting geometry that supports multiple targets, whose optimal design is allowed to be driven by the physics of the positron production processes, while naturally supporting cooling of the targets.
BNL, Upton, Long Island, New York, USA
RHIC operated at energies below the nominal ion injection energy of E=9.8 GeV/u in 2010. Earlier test runs and magnet measurements indicated that all defocusing sextupole unipolar power supplies should be reversed to provide the proper sign of chromaticity. However, vertical chromaticity at E=3.85 GeV/u with this power supply configuration was still not optimal. This uncertainty inspired a new machine configuration where only half of the defocusing sextupole power supplies were reversed, taking advantage of the flexibility of the RHIC nonlinear chromaticity correction system to mimic bipolar sextupoles. This configuration resulted in a 30 percent luminosity gain and eliminated the need for further polarity changes for later 2010 low energy physics operations. Here we describe the background to this problem, operational experience, and RHIC online model changes to implement this solution.
Muons, Inc, Batavia, USA
Northern Illinois University, DeKalb, Illinois, USA
Lewis University, Romeoville, Illinois, USA
Technological innovations in recent years have revived interest in muon colliders as the next generation energy frontier machine. The biggest challenge for muon colliders is that muons decay. Advances in muon cooling technology will make the focussing and acceleration of muons to TeV energies possible. The challenge for the detectors in such machines is overcoming the large backgrounds from muon decays in the colliding ring lattice that will inundate the interaction region (IR) and will make triggering and data reconstruction a challenge. Developing simulation tools that can reliably model the environment of the muon collider IR will be critical to physics analyses. We will need to expand the capabilities of current programs and use them to benchmark and verify results against each other. Here we are comparing an emerging capabiligy of G4beamline, an interface for physicists to GEANT4 code, with MARS, a mature program for particle fluences, in developing code for muon collider background studies
Muons, Inc, Batavia, USA
Northern Illinois University, DeKalb, Illinois, USA
Lewis University, Romeoville, Illinois, USA
Muon colliders are considered to be an important future energy frontier accelerator. It is possible to build a large muon collider as a circular machine, even at multi-TeV energies, due to the greatly reduced synchrotron radiation expected from muons. In addition to the same physics processes present in an electron collider, a muon collider will have the potential to produce s-channel resonances such as the various Higgs states at an enhanced rate. For a muon collider with 750 GeV/c mu+ and mu- with 1012 mu per bunch we would expect 4.3x105 muon decays per meter. These muon decays will produce very energetic off momentum electrons that can produce detector backgrounds that can affect the physics. These backgrounds include electrons from muon decays, synchrotron radiation from the decay electrons, hadrons produced by photo-nuclear interactions, coherent and incoherent beam-beam pair production and Bethe-Heitler muon production. In this paper we will discuss these processes and calculate particle fluxes into the detector volume from these background processes.
Northern Illinois University, DeKalb, Illinois, USA
Muons, Inc, Batavia, USA
Lewis University, Romeoville, Illinois, USA
NRL, Washington, DC, USA
SAIC, Billerica, Massachusetts, USA
A diamond current amplifier concept can reduce demands made of photocathodes under development for high performance Free Electron Lasers (FELs) by augmenting the charge per bunch (i.e., increasing the apparent QE of the photocathode) by employing secondary emission amplification in a diamond flake*. The characteristics of the bunch that emerges from the diamond flake is dependent on properties of the diamond (e.g., impurity concentrations) and the conditions under which it is operated (e.g., voltage drop, space charge, temperature)**. A study of the electron bunches produced by an incident 3-5 keV beam striking a very thin diamond and its transport under bias subject to scattering and space charge forces is considered. The quantities of greatest interest are then the yield, the transit time, emittance, and the rise/fall characteristics of the emerging bunch. These are simulated using Monte Carlo techniques, the application of which shall be described as it applies to the initial generation of the secondary electrons followed by their scattering and transport in the presence of band bending and space charge.
*J.E. Yater, et al., IEEE IVNC (2009); J. L. Shaw, et al., ibid.
**K.L. Jensen, et al. J. Appl. Phys. 108, 044509 (2010).
NSCL, East Lansing, Michigan, USA
Notre Dame University, Notre Dame, Iowa, USA
LBNL, Berkeley, California, USA
FRIB, East Lansing, Michigan, USA
DIANA (Dakota Ion Accelerators for Nuclear Astrophysics) is a next generation nuclear astrophysics accelerator facility proposed to be built as part of the US DUSEL (Deep Underground Science and Engineering Laboratory) project. The scientific goals of DIANA are focused on experiments related to nucleosynthesis processes. Reaction cross-sections at stellar temperature are extremely low, which makes these experiments challenging. Small signal rates are overwhelmed by large background rates associated with cosmic ray-induced reactions, background from natural radioactivity in the laboratory environment, and the beam-induced background on target impurities. By placing the DIANA facility deep underground (1.4 km) the cosmic ray induced background can be eliminated. In addition, the DIANA accelerator is being designed to achieve large laboratory reaction rates by delivering high ion beam currents (up to 100 mA) to a high density super-sonic jet-gas target (up to 1018 atoms/cm2). Two accelerators are coupled to enable measurements over a wide energy range from 30 keV to 3 MeVin a consistent manner. The accelerators design and its technical challenges are presented.