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A free interactive matching program

Description: For physicists and engineers involved in the design and analysis of beamlines (transfer lines or insertions) the lattice function matching problem is central and can be time-consuming because it involves constrained nonlinear optimization. For such problems convergence can be difficult to obtain in general without expert human intervention. Over the years, powerful codes have been developed to assist beamline designers. The canonical example is MAD (Methodical Accelerator Design) developed at CERN by Christophe Iselin. MAD, through a specialized command language, allows one to solve a wide variety of problems, including matching problems. Although in principle, the MAD command interpreter can be run interactively, in practice the solution of a matching problem involves a sequence of independent trial runs. Unfortunately, but perhaps not surprisingly, there still exists relatively few tools exploiting the resources offered by modern environments to assist lattice designer with this routine and repetitive task. In this paper, we describe a fully interactive lattice matching program, written in C++ and assembled using freely available software components. An important feature of the code is that the evolution of the lattice functions during the nonlinear iterative process can be graphically monitored in real time; the user can dynamically interrupt the iterations at will to introduce new variables, freeze existing ones into their current state and/or modify constraints. The program runs under both UNIX and Windows NT.
Date: April 16, 1999
Creator: Ostiguy, J.-F.
Partner: UNT Libraries Government Documents Department

CHEF: a status report

Description: CHEF refers both to a framework and to an interactive application emphasizing accelerator optics calculations. The framework supports multiple domains of applications: e.g. nonlinear analysis, perturbation theory, and tracking. Its underlying philosophy is to provide an infrastructure with minimum hidden implicit assumptions, general enough to facilitate both routine and specialized computational tasks, and to minimize the duplication of necessary, complex bookkeeping tasks. CHEF was already described in recent conferences. This paper is a status report on recent developments, including issues related to applications to high energy linacs.
Date: June 1, 2007
Creator: Ostiguy, J.-F. & Michelotti, L.
Partner: UNT Libraries Government Documents Department

Enhancements to the longitudinal dynamics code ESME

Description: ESME is a program developed at Fermilab for simulating both single particle and multi-particle dynamics in proton synchrotrons. The code has evolved incrementally for more than fifteen years, accumulating many useful features and some internal inconsistency in the process. In the latest revision (8.2), a significant effort has been made to eliminate inconsistency and ambiguity in the determination of phases for multiple RF systems. The use of frequency and phase curves is now more transparent. Other additions or improvements include additional features for time domain calculation, low noise distributions to extend multi-particle capability, run-time memory allocation and portable graphics. A Web page has been established to facilitate the distribution of the source code and documentation. Further information, bug reports and fixes will be made available through this resource.
Date: May 1, 1997
Creator: MacLachlan, J. & Ostiguy, J.F.
Partner: UNT Libraries Government Documents Department

The Fermilab lattice information repository

Description: Over the years, it has become increasingly obvious that a centralized lattice and machine information repository with the capability of keeping track of revision information could be of great value. This is especially true in the context of a large accelerator laboratory like Fermilab with six rings and sixteen beamlines operating in various modes and configurations, constantly subject to modifications, improvements and even major redesign. While there exist a handful of potentially suitable revision systems--both freely available and commercial--our experience has shown that expecting beam physicists to become fully conversant with complex revision system software used on an occasional basis is neither realistic nor practical. In this paper, we discuss technical aspects of the FNAL lattice repository, whose fully web-based interface hides the complexity of Subversion, a comprehensive open source revision system. The FNAL repository has been operational since September 2004; the unique architecture of ''Subversion'' has been a key ingredient of the technical success of its implementation.
Date: May 1, 2005
Creator: Ostiguy, J.-F.; Michelotti, L.; McCusker-Whiting, M.; Kriss, M. & /Fermilab
Partner: UNT Libraries Government Documents Department

Stability of Flat Bunches in the Recycler Barrier Bucket

Description: We examine the stability of intense flat bunches in barrier buckets used in the Fermilab Recycler. We consider some common stationary distributions and show that they would be unstable against rigid dipole oscillations. We discuss the measurements which identify stable distributions. We also report on experimental studies on the impact of creating a local extremum of the incoherent frequency within the rf bucket. We considered two typical stationary distributions and found they were not adequate descriptions of the Recycler bunches. From the measured line density distribution we find (a) the tanh function is a good fit to the line density, and (b) the coherent frequency of the rigid dipole mode for this distribution is within the incoherent spread at nominal intensities. Stability diagrams when the beam couples to space charge and external impedances will be discussed elsewhere. Our initial experimental investigations indicate that longitudinal stability in the Recycler is, consistent with expectations, influenced by the ratio T{sub 2}/(4T{sub 1}) which determines the location of the extremum of the incoherent tune. The coherent tune depends strongly on the distribution in the bunch tails which is difficult to measure. Numerical studies using both a conventional tracking code and a Vlasov solver are in progress and should provide more insight into conditions that may lead to unstable behavior.
Date: May 1, 2009
Creator: Sen, T.; Bhat, C.; Ostiguy, J.-F. & /Fermilab
Partner: UNT Libraries Government Documents Department

Conceptual design of the Project-X 1.3 GHz 3-8 GeV pulsed linac

Description: Project-X, a multi-MW proton source, is under development at Fermilab. It enables a Long Baseline Neutrino Experiment via a new beam line pointed to DUSEL in Lead, South Dakota, and a broad suite of rare decay experiments. The initial acceleration is provided by a 3-GeV 1-mA CW superconducting linac. In a second stage, about 5% of the H{sup -} beam is accelerated up to 8 GeV in a 1.3 GHz SRF pulsed linac and injected into the Recycler/Main Injector complex. In order to mitigate problems with stripping foil heating during injection, higher current pulses are accelerated in the CW linac in conjunction with the 1 mA beam which is separated and further accelerated in the pulsed linac. The optimal current in the pulsed linac is discussed as well as the constraints that led to its selection. A conceptual design which covers optics and RF stability analysis is presented. Finally, the need for HOM damping is discussed.
Date: March 1, 2011
Creator: Solyak, N.; Eidelman, Y.; Nagaitsev, S.; Ostiguy, J.-F.; Vostrikov, A.; Yakovlev, V. et al.
Partner: UNT Libraries Government Documents Department

Analysis of beam loss mechanism in the Project X linac

Description: Minimization of the beam losses in a multi-MW H{sup -} linac such as ProjectX to a level below 1 W/m is a challenging task. The impact of different mechanism of beam stripping, including stripping in electric and magnetic fields, residual gas, blackbody radiation and intra-beam stripping, is analyzed. Other sources of beam losses are misalignements of beamline elements and errors in RF fields and phases. We present in this paper requirements for dynamic errors and correction schemes to keep beam losses under control.
Date: March 1, 2011
Creator: Carneiro, J.-P.; Lebedev, V.; Nagaitsev, S.; Ostiguy, J.-F.; Solyak, N. & /Fermilab
Partner: UNT Libraries Government Documents Department

Hybrid permanent quadrupoles for the 8 GeV transfer line at Fermilab

Description: Hybrid Permanent Magnet Quadrupoles for specialized portions of the 8 GeV transfer line from the Fermilab Booster to the new Main Injector have been built, tested and installed. These magnets use a 0.635 m long iron shell and provide an integrated gradient of 1.48 T-m/m with an iron pole tip radius of 0.0416 m. and pole length of 0.508 m. Bricks of 0.0254 m thick strontium ferrite supply the flux to the back of the pole to produce the desired 2.91 T/m gradient. For temperature compensation, Ni-Fe alloy strips are interspersed between ferrite bricks to subtract flux in a temperature dependent fashion. Adjustments of the permeance of each pole using iron from between the pole and the flux return shell permits the matching of pole potentials. Magnetic potentials of the poles are measured with a Rogowski coil and adjusted to the desired value to achieve the prescribed strength and field uniformity. After these adjustments, the magnets are measured using a rotating coil to determine the integral gradient and the harmonics. These measurements are used to calibrate the production Rogowski coil measurements. Similar quadrupoles are included in the design of the Fermilab Recycler.
Date: June 1, 1997
Creator: Pruss, S. M.; Foster, G. W.; Glass, H. D.; Harding, D. J.; Jackson, G. P.; May, M. P. et al.
Partner: UNT Libraries Government Documents Department

Physics goals for the planned next linear collider engineering test facility.

Description: The Next Linear Collider (NLC) Collaboration is planning to construct an Engineering Test Facility (ETF) at Fermilab. As presently envisioned, the ETF would comprise a fundamental unit of the NLC main linac to include X-band klystrons and modulators, a delay-line power-distribution system (DLDS), and NLC accelerating structures that serve as loads. The principal purpose of the ETF is to validate stable operation of the power-distribution system, first without beam, then with a beam having the NLC pulse structure. This paper concerns the possibility of configuring and using the ETF to accelerate beam with an NLC pulse structure, as well as of doing experiments to measure beam-induced wakefields in the rf structures and their influence back on the beam.
Date: July 17, 2001
Creator: Bohn, C.; Michelotti, L.; Ostiguy, J.-F.; Syphers, M.; Bluem, H.; Todd, A. et al.
Partner: UNT Libraries Government Documents Department

PXIE Optics and Layout

Description: The Project X Injector Experiment (PXIE) will serve as a prototype for the Project X front end. The aim is to validate the Project-X design and to decrease technical risks mainly related to the front end. The paper discusses the main requirements and constraints motivating the facility layout and optics. Final adjustments to the Project X front end design, if needed, will be based on operational experience gained with PXIE.
Date: May 1, 2012
Creator: Lebedev, V.A.; Nagaitsev, S.; Ostiguy, J.-F.; Shemyakin, A.V.; Shteynas, B.G.; Solyak, N. et al.
Partner: UNT Libraries Government Documents Department

Status of the Project-X CW Linac Design

Description: Project-X is a proposed proton accelerator complex at Fermilab that would provide particle beams to support a diversified experimental program at the intensity frontier. As currently envisioned, the complex would employ a CW superconducting linac to accelerate a 1 mA average, 5 mA peak H{sup -} beam from 2.1 MeV to 3 GeV. A second superconducting linac, operating in pulsed mode would ultimately accelerate a small fraction of this beam up to 8 GeV. The CW linac is based on five families of resonators operating at three frequencies: half-wave (1 family at 162.5 MHz), spoke (2 families at 325 MHz) and elliptical (2 families at 650 MHz). Accelerating and focusing elements are assembled in cryomodules separated by short warm sections. A long open region ({approx} 15 m) allows beam extraction at 1 GeV in support of a nuclear experimental program. In this paper, we present the latest iteration of the CW linac baseline lattice. We also briefly compare it to an alternative where the 162.5 half-wave resonators are replaced with 325 MHz spoke resonators.
Date: May 1, 2012
Creator: Ostiguy, J-F.; Solyak, N.; Berrutti, P.; Carneiro, J.P.; Lebedev, V.; Nagaitsev, S. et al.
Partner: UNT Libraries Government Documents Department

ORBIT: A CODE FOR COLLECTIVE BEAM DYNAMICS IN HIGH INTENSITY RINGS.

Description: We are developing a computer code, ORBIT, specifically for beam dynamics calculations in high-intensity rings. Our approach allows detailed simulation of realistic accelerator problems. ORBIT is a particle-in-cell tracking code that transports bunches of interacting particles through a series of nodes representing elements, effects, or diagnostics that occur in the accelerator lattice. At present, ORBIT contains detailed models for strip-foil injection, including painting and foil scattering; rf focusing and acceleration; transport through various magnetic elements; longitudinal and transverse impedances; longitudinal, transverse, and three-dimensional space charge forces; collimation and limiting apertures; and the calculation of many useful diagnostic quantities. ORBIT is an object-oriented code, written in C++ and utilizing a scripting interface for the convenience of the user. Ongoing improvements include the addition of a library of accelerator maps, BEAMLINE/MXYZPTLK, the introduction of a treatment of magnet errors and fringe fields; the conversion of the scripting interface to the standard scripting language, Python; and the parallelization of the computations using MPI. The ORBIT code is an open source, powerful, and convenient tool for studying beam dynamics in high-intensity rings.
Date: April 8, 2002
Creator: HOLMES,J.A.; DANILOV,V.; GALAMBOS,J.; SHISHLO,A.; COUSINEAU,S.; CHOU,W. et al.
Partner: UNT Libraries Government Documents Department

Stability tests of permanent magnets built with strontium ferrite

Description: Permanent magnets built using strontium ferrite bricks have been tested for stability against demagnetization. Ten test dipoles were built to monitor ferrite behavior under a variety of stressing conditions, including irradiation, mechanical shock, extreme thermal excursions, and long term magnetization stability. The test magnets were geometrically similar to, but much shorter than, the magnets built for the 8 GeV transfer line at FNAL. No loss of magnetization was observed for bricks exposed to a proton beam, and a magnet exposed to several Gigarads of Co{sup 60} gamma radiation suffered no measurable demagnetization. The magnet strength was observed to decrease logarithmically with time, consistent with the expected effect of thermal fluctuations. Irreversible demagnetization of {approx}0.1% was seen in cooling magnets to 0{degree}C, and the loss was {approx}0.2% for magnets cooled to -20{degree}C. No additional demagnetization was seen on subsequent cycling to 0{degree}C. Finally, one of the long dipoles built for the 8 GeV line was periodically tested over the course of 3 months, and showed no measurable demagnetization.
Date: June 1, 1997
Creator: Glass, H.D.; Brown, B.C.; Foster, G.W.; Fowler, W.B.; Gustafson, R.; Jackson, G.P. et al.
Partner: UNT Libraries Government Documents Department

Hybrid permanent magnet quadrupoles for the Recycler Ring at Fermilab

Description: Hybrid Permanent Magnet Quadrupoles are used in several applications for the Fermilab Recycler Ring and associated beam transfer lines. Most of these magnets use a 0.6096 m long iron shell and provide integrated gradients up to 1.4 T-m/m with an iron pole tip radius of 41.6 mm. A 58.4 mm pole radius design is also required. Bricks of 25. 4 mm thick strontium ferrite supply the flux to the back of the pole to produce the desired gradients (0.6 to 2.75 T/m). For temperature compensation, Ni-Fe alloy strips are interspersed between ferrite bricks to subtract flux in a temperature dependent fashion. Adjustments of the permeance of each pole using iron between the pole and the flux return shell permits the matching of pole potentials. Magnetic potentials of the poles are adjusted to the desired value to achieve the prescribed strength and field uniformity based on rotating coil harmonic measurements. Procurement, fabrication, pole potential adjustment, and measured fields will be reported.
Date: October 1, 1997
Creator: Brown, B.C.; Pruss, S.M.; Foster, G.W.; Glass, H.D.; Harding, D.J.; Jackson, G.R. et al.
Partner: UNT Libraries Government Documents Department

Hybrid permanent magnet gradient dipoles for the recycler ring at Fermilab

Description: Hybrid permanent magnets provide the magnetic fields for an anti- proton storage ring which is under construction at Fermilab. Using a combined function lattice, gradient magnets provide the bending, focusing and sextupole correction for the regular cells. Shorter magnets without sextupole are used in dispersion suppressor cells. These magnets use a 4.7 m ( 3 m) long iron shell for flux return, bricks of 25.4 mm thick strontium ferrite supply the flux and transversely tapered iron poles separated by aluminum spacers set the shape of the magnetic field. Central fields of 0.14 T with gradients of {approx}6%/inch ({approx}13%/inch) are required. Field errors are expected to be less than 10{sup -4} of the bend field over an aperture of {+-}40 mm (horizontal) {times} {+-}20 mm (vertical). Design, procurement, fabrication, pole potential adjustment, field shape trimming and measured fields will be reported.
Date: November 1, 1997
Creator: Brown, B.C.; Dimarco, J.; Foster, G.W.; Glass, H.D.; Haggard, J.E.; Harding, D.J. et al.
Partner: UNT Libraries Government Documents Department