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Tracking of three variants of transition-free lattices for a proton driver

Description: Transition-free lattices are favored as possible realization of proton drivers. Several variants have been proposed, some of which have considerably different behavior. One of the main quantities used to characterize this behavior is the short term dynamic aperture (DA). In this note we study three different variants of such lattices, and show that the differences in DA among the lattices essentially disappear as soon as magnet multipole errors are included in the simulation. The tracking results can be understood in terms of the normal form based amplitude dependent tune shift and resonance strength coefficients.
Date: October 14, 2002
Creator: Johnstone, Bela Erdelyi and Carol
Partner: UNT Libraries Government Documents Department

Effect of Wiggler insertions on the single-particle dynamics of the NLC main damping rings

Description: As they are expected to occupy a large portion of the lattice, wiggler insert ions will introduce significant linear and nonlinear perturbations to the single-particle dynamics in the NLC Main Damping Rings (MDR). The nonlinearities are of particular concern as a sufficiently large Dynamic Aperture (DA) is required for high injection efficiency. The main content of this report is a study of the wigglers impact on the DA of the NLC-MDR latest lattice design. The particle dynamics is modeled by transfer maps calculated by integration through the wiggler fields. For field representation we employed a 3D multipole expansion derived from the field data that were obtained with the aid of a magnet design code. Additional contents of this paper include an investigation of a simplified model of wiggler consisting of a sequence of standard magnet elements (where thin octupoles are used to represent the dominant nonlinearities) and the suggestion of a possible correction scheme to compensate the wiggler nonlinearities.
Date: July 30, 2003
Creator: Venturini, Marco
Partner: UNT Libraries Government Documents Department

First Order Perturbation Effects in Iron-Dominated Two-DimensionalSymmetrical Multipoles

Description: The effects of several perturbations are investigated. They are: modification of the shape of a pole, error excitation, displacement, and rotation of a pole. The effects are described in terms of changes of multipole coefficients. General relationships between some of these coefficients are described, and formulae are derived that allow their calculation for a model 2N-pole magnet. Numerical values of these coefficients are given for a quadrupole, sextupole, and octupole.
Date: April 1, 1969
Creator: Halbach, K.
Partner: UNT Libraries Government Documents Department

Forces and Stored Energy in Thin Cosine (n0) Accelerator Magnets

Description: We wish to compute Lorentz forces, equilibrium stress and stored energy in thin multipole magnets (Fig.1), that are proportional to cos(n{theta}) and whose strength varies purely as a Fourier sinusoidal series of the longitudinal coordinate z (say proportional to cos (2m-1){pi}z/L where L denotes the half-period and m = 1,2,3...). We shall demonstrate that in cases where the current is situated on such a surface of discontinuity at r = R (i.e. J = f({theta},z)), by computing the Lorentz force and solving the state of equilibrium on that surface, a closed form solution can be obtained for single function magnets as well as for any combination of interacting nested multi function magnets. The results that have been obtained, indicate that the total axial force on the end of a single multipole magnet n is independent (orthogonal) to any other multipole magnet i as long as n {ne} i. The same is true for the stored energy, the total energy of a nested set of multipole magnets is equal to the some of the energy of the individual magnets (of the same period length 2L). Finally we demonstrate our results on a nested set of magnets a dipole (n = 1) and a quadmpole (n=2) that have an identical single periodicity {omega}{sub 1}. We show that in the limiting 2D case (period 2L tends to infinity), the force reduces to the commonly known 2D case.
Date: March 18, 1996
Creator: Caspi, S.
Partner: UNT Libraries Government Documents Department

Preliminary study of using pipetron-type magnets for a pre-accelerator for the LHC

Description: One of the luminosity limitations of the LHC is the rather low injection energy (0.45 TeV) with respect to the collision energy (7 TeV). The magnetic multipoles in the main dipoles at low field and their dynamic behavior are considered to limit the achievable bunch intensity and emittance. We report on a preliminary study to increase the injection energy to 1.5 TeV using a two-beam pre-accelerator (LER) in the LHC tunnel. The LER is based on ''Pipetron'' magnets as originally proposed for the VLHC. The aim of the study is to assess the feasibility and to identify the critical processes or systems that need to be investigated and developed to render such a machine possible.
Date: June 1, 2006
Creator: de Rijk, G.; Rossi, L.; /CERN; Piekarz, H. & /Fermilab
Partner: UNT Libraries Government Documents Department

More thoughts on the Aladdin experiments - experiment set 2

Description: It turns out that the theorem of corresponding motions is true only if we restrict the equations of motion to linear and sextupole terms. It is not necessary to work in a regime where the theorem holds, but it has two big advantages. It allows an easy check (see if the theorem holds) on whether there are important terms we are not keeping in the analysis. It also means we can survey the entire neighborhood of the resonance intersection by surveying a semicircle around the intersection. I will assume that we choose the intersection V{sub x} = 7 1/6, V{sub z} = 7 1/3 as suggested in Ref. 1, and that we maintain the validity of the theorem of corresponding motions.
Date: October 1, 1988
Creator: Symon, K.
Partner: UNT Libraries Government Documents Department

Magnetic design and measurement of nonlinear multipole magnets for the APT beam expander system

Description: Two prototype nonlinear multipole magnets have been designed for use in the 800-MeV beam test of the APT beam-expansion concept at LANSCE. The iron-dominated magnets each consist of three independent coils, two for producing a predominantly octupole field with a tunable duodecapole component, and one for canceling the residual quadrupole field. Two such magnets, one for shaping each transverse plane, are required to produce a rectangular, uniform beam current density distribution with sharp edges on the APT target. This report will describe the magnetic design of these magnets, along with field measurements, and a comparison to the magnetic design.
Date: October 1, 1997
Creator: Barlow, D.B.; Shafer, R.E.; Martinez, R.P.; Walstrom, P.L.; Kahn, S.; Jain, A. et al.
Partner: UNT Libraries Government Documents Department

Multipole Spill-Down Effects in the SPEAR3 Dipole Magnets

Description: The main SPEAR3 dipole magnets are 1.45 m long with a pole contour designed to horizontally deflect and vertically focus the electron beam. At the nominal beam energy (3 GeV), the field and gradient along the magnet centerline are 1.3 T and 3.3 T/m (k = {minus}0.33 m{sup {minus}2}), respectively. Due to the straight core construction, the beam passes through each dipole with up to 16.6 mm trajectory offset relative to the centerline. This paper describes a method used to characterize the spilldown effect from magnetic multipole fields as observed by the beam traversing the dipole magnets. Results of tracking studies utilizing the longitudinal variation of multipole fields are discussed.
Date: August 19, 1999
Creator: Corbett, William
Partner: UNT Libraries Government Documents Department

Probing the Structure of Nucleons in the Resonance Region with CLAS at Jefferson Lab

Description: The physics of electromagnetic excitation of nucleon resonances and of their relevance in nucleon structure studies are discussed. Preliminary data from the CLAS detector on the N-Delta(1232) transition multipoles, the helicity amplitudes of the N*(1535), and the search for so-called ''missing resonances'' at Jefferson Lab are presented.
Date: March 1, 2000
Creator: Burkert, Volker D.
Partner: UNT Libraries Government Documents Department

How to extract the P{sub 33}(1232) resonance contributions from the amplitudes M{sub 1{sup +}}{sup 3/2},E{sub 1{sup +}}{sup 3/2},S{sub 1{sup +}}{sup 3/2} of pion electroproduction on nucleons

Description: Within the dispersion relation approach, solutions of integral equations for the multipoles M{sub 1{sup +}}{sup 3/2},E{sub 1{sup +}}{sup 3/2},S{sub 1{sup +}}{sup 3/2} are found at 0 < Q{sup 2} < 3 GeV{sup 2}. These solutions should be used as input for the resonance and nonresonance contributions in the analyses of pion electroproduction data in the P{sub 33}(1232) resonance region. It is shown that the traditional identification of the amplitude M{sub 1{sup +}}{sup 3/2} (as well of the amplitudes E{sub 1{sup +}}{sup 3/2},S{sub 1{sup +}}{sup 3/2}) with the P{sub 33}(1232) resonance contribution is not right; there is a contribution in these amplitudes which has a nonresonance nature and is produced by rescattering effects in the diagrams corresponding to the nucleon and pion poles. This contribution is reproduced by the dispersion relations. Taking into account nonresonance contributions in the amplitudes M{sub 1{sup +}}{sup 3/2},E{sub 1{sup +}}{sup 3/2}, the helicity amplitudes A{sub p}{sup 1/2}, A{sub p}{sup 3/2} and the ratio E2/M1 for the {gamma}N {r_arrow} P{sub 33}(1232) transition are extracted from experiment at Q{sup 2}=0. They are in good agreement with quark model predictions.
Date: August 1997
Creator: Aznauryan, I. G.
Partner: UNT Libraries Government Documents Department

Specification of multipole tolerances for the APS quadrupole magnet

Description: This note will address a proposed method for specifying the multipole tolerance for the design and production of APS quadrupole magnets. The tolerances for the multipole components for the quadrupole magnets will be set to that level which reduces the dynamic aperture by about 10--15% from the ideal machine dynamic aperture (as specified in CDR-87). This level may appear rather stringent, especially compared to the 50--60% reduction resulting from quad placement errors. However, when all tolerances are taken together, the residual dynamic aperture would be prohibitively small and commissioning would be difficult if these tolerances were at twice this level. The dynamic aperture was determined using the numerical tracking program RACETRACK.
Date: August 1, 1988
Creator: Kramer, S. L.
Partner: UNT Libraries Government Documents Department

Results of magnetic measurements and field integral compensation for the Elliptical Multipole Wiggler

Description: A prototype of the Elliptical Multipole Wiggler (EMW) has been assembled, tested and tuned at the APS. This prototype has a period of 160 mm with 7 poles for the hybrid structure and 10 poles for the electromagnet part of the EMW. The hybrid structure of the EMW produces a vertical maenetic field of 0.83 T with K{sub y}= 12 for a cap of 27 mm, and the electromagnetic structure provides a horizontal field chancre up to 100 Hz with a maximum field of 0.12 T (I= 0.6 kA, K{sub x}= 1.6). The current pulse has a trapezium-type shape with a switching time to chancre the current polarity of about 2 ms. The measurements and tuning, were done for direct current (DC) mode and alternating current (AC) mode. Fine adjustment during the test at the NSLS X-ray ring, using the BPMs and active correction system allowed to achieve about 1 {mu}m of beam distortion. It corresponds to the peak-to-peak variations during, the time less than {plus_minus}0.5 G-cm and {plus_minus}100 G-cm{sup 2} of the first and second horizontal field integrals respectively.
Date: June 1, 1995
Creator: Frachon, D.; Ivanov, P.M.; Medvedko, E.A.; Vasserman, I.; Despe, O. & Kang, Y.G.
Partner: UNT Libraries Government Documents Department

Concerning effects of low-beta region fringe fields and multipole error distribution on dynamics in LHC.

Description: Effects of fringe fields in separation dipoles D1/D2 and low-{beta} quadrupoles Q1-Q3 of LHC interaction regions in collision optics are investigated by means of stepwise ray-tracing in terms of aberrations, beam envelopes and other detunings. Effects of the longitudinal distribution of b{sub 10} error coefficient are next investigated in a similar way for assessment and comparison.
Date: August 1, 1997
Creator: Meot, F. & Paris, A.
Partner: UNT Libraries Government Documents Department

The main injector chromaticity correction sextupole magnets: Measurements and operating schemes

Description: The Fermilab Main Injector (FMI) is a high intensity proton synchrotron which will be used to accelerate protons and antiprotons from 8.9 GeV/c to 150 GeV/c. The natural chromaticities of the machine for the horizontal and the vertical Planes are {minus}33.6 and {minus}33.9 respectively. The {Delta}p/p of the beam at injection is about 0.002. The chromaticity requirements of the FMI, are primarily decided by the {Delta}p/p = 0.002 of the beam at injection. This limits the final chromaticity of the FMI to be {plus_minus}5 units. To correct the chromaticity in the FMI two families of sextupole magnets will be installed in the lattice, one for each plane. A sextupole magnet suitable for the FMI needs has been designed and a number of them are being built. New chromaticity compensation schemes have been worked out in the light of recently proposed faster acceleration ramps. On an R/D sextupole magnet the low current measurements have been carried out to determine the electrical properties. Also, using a Morgan coil, measurements have been performed to determine the higher ordered multipole components up to 18-poles. An overview of these result are presented here.
Date: May 1, 1995
Creator: Bhat, C.M.; Bogacz, A.; Brown, B.C.; Harding, D.J.; Fang, S.J.; Martin, P.S. et al.
Partner: UNT Libraries Government Documents Department

A Compact High Gradient Pulsed Magnetic Quadpole

Description: A design for a high gradient, low inductance pulsed quadrupole magnet is presented. The magnet is a circular current dominated design with a circular iron return yoke. Conductor angles are determined by a method of direct multipole elimination which theoretically eliminates the first four higher order multipole field components. Coils are fabricated from solid round film-insulated conductor, wound as a single layer ''non-spiral bedstead'' coil having a diagonal leadout entirely within one upturned end. The coils are wound and stretched straight in a special winder, then bent in simple fixtures to form the upturned ends.
Date: July 5, 2005
Creator: Shuman, D.; Faltens, A.; Kajiyama, Y.; Kireeff-Covo, M. & Seidl, P.
Partner: UNT Libraries Government Documents Department

Correction of aberrations - past, present and future.

Description: The performance of static rotationally symmetric electron lenses is limited by unavoidable chromatic and spherical aberrations. In 1936, Scherzer demonstrated that the integrands of the integral expressions for the coefficients of these aberrations can be written as a sum of positive quadratic terms. Hence these coefficients can never change sign. This important result is called the Scherzer theorem, the only theorem existing in electron optics. Employing variational methods, Tretner determined the field of magnetic and electrostatic round lenses, which yields the smallest spherical aberration coefficient for particular constraints [2]. Unfortunately, these coefficients are still too large for realistic boundaries to enable sub-Angstrom resolution at medium voltages of about 200 to 300 kV. Therefore, the only possibility to directly reach this limit is the correction of the troublesome aberrations. It was again Scherzer who showed different procedures for canceling these aberrations [3]. The most promising is the incorporation of a corrector consisting of multipole elements or of a tetrode mirror in the case of low voltages. Although the mirror is rotationally symmetric, a non-rotationally symmetric beam splitter is needed to separate the incident beam from the reflected beam.
Date: February 21, 2002
Creator: Rose, H.
Partner: UNT Libraries Government Documents Department

Construction of block-coil high-field model dipoles for future hadron colliders

Description: A family of high-field dipoles is being developed at Texas A&M University, as part of the program to improve the cost-effectiveness of superconducting magnet technology for future hadron colliders. The TAMU technology employs stress management, flux-plate control of persistent-current multipoles, conductor optimization using mixed-strand cable, and metal-filled bladders to provide pre-load and surface compliance. Construction details and status of the latest model dipole will be presented.
Date: August 4, 2002
Creator: Blackburn, Raymond; Elliott, Tim; Henchel, William; McInturff, Al; McIntyre, Peter & Sattarov, Akhdior
Partner: UNT Libraries Government Documents Department

Magnetic design of trim excitations for the advanced light source storage ring sextupole

Description: The Advanced Light Source (ALS) storage ring sextupole is a unique multi-purpose magnet. It is designed to operate as a sextupole with three auxiliary trim modes: horizontal steering, vertical steering, and skew quadrupole. A perturbation theory for iron-dominated magnets developed by Klaus Halbach provides the basis for this design. The three trim excitations are produced by violating sextupole symmetry and are thus perturbations of the normal sextupole excitation. The magnet was designed such that all four modes are decoupled and can be excited independently. This paper discusses the use of Halbach`s perturbation theory to design the trim functions and to evaluate the primary asymmetry in the sextupole mode, namely, a gap in the return yoke to accommodate the vacuum chamber.
Date: June 1, 1995
Creator: Marks, S.
Partner: UNT Libraries Government Documents Department

Eddy-current-induced multipole field calculations.

Description: Time-varying magnetic fields of magnets in booster accelerators induce substantial eddy currents in the vacuum chambers. The eddy currents in turn act to produce various multipole fields that act on the beam. These fields must be taken into account when doing a lattice design. In the APS booster, the relatively long dipole magnets (3 meters) are linearly ramped to accelerate the injected 325 MeV beam to 7 GeV. Substantial dipole and sextupole fields are generated in the elliptical vacuum chamber from the induced eddy currents. In this note, formulas for the induced dipole and sextupole fields are derived for elliptical and rectangular vacuum chambers for a time-varying dipole field. A discussion is given on how to generalize this derivation method to include eddy-current-induced multipole fields from higher multipole magnets (quadrupole, sextupole, etc.). Finally, transient effects are considered.
Date: October 15, 2003
Creator: Sereno, N. S. & Kim, S. H.
Partner: UNT Libraries Government Documents Department

The new magnetic measurement system at the Advanced Photon Source.

Description: A new system for precise measurements of the field integrals and multipole components of the APS magnetic insertion devices is described. A stretched coil is used to measure magnetic field characteristics. The hardware includes a number of servomotors to move (translate or rotate) the coil and a fast data acquisition board to measure the coil signal. A PC under Linux is used as a control workstation. The user interface is written as a Tcl/tk script; the hardware is accessed from the script through a shared C-library. A description of the hardware system and the control program is given.
Date: March 15, 2002
Creator: Eidelman, Y.; Deriy, B.; Makarov, O. & Vasserman, I.
Partner: UNT Libraries Government Documents Department

Progress on muon parametric-resonance ionization cooling channel development

Description: Parametric-resonance Ionization Cooling (PIC) is intended as the final 6D cooling stage of a high-luminosity muon collider. To implement PIC, a continuous-field twin-helix magnetic channel was developed. A 6D cooling with stochastic effects off is demonstrated in a GEANT4/G4beamline model of a system where wedge-shaped Be absorbers are placed at the appropriate dispersion points in the twin-helix channel and are followed by short rf cavities. To proceed to cooling simulations with stochastics on, compensation of the beam aberrations from one absorber to another is required. Initial results on aberration compensation using a set of various-order continuous multipole fields are presented. As another avenue to mitigate the aberration effect, we optimize the cooling channel's period length. We observe a parasitic parametric resonance naturally occurring in the channel's horizontal plane due to the periodic beam energy modulation caused by the absorbers and rf. We discuss options for compensating this resonance and/or properly combining it with the induced half-integer parametric resonance needed for PIC.
Date: July 1, 2012
Creator: V.S. Morozov, Ya.S. Derbenev, A. Afanasev, K.B. Beard, R.P. Johnson, B. Erdelyi, J.A. Maloney
Partner: UNT Libraries Government Documents Department

Results of stretched wire field integral measurements on the mini-undulator magnet -- comparison of results obtained from circular and translational motion of the integrating wire

Description: Measurements of the multipole content of the Mini-Undulator magnet have been made with two different integrating wire techniques. Both measurements used 43 strand Litz wire stretched along the length of the magnet within the magnet gap. In the first technique, the wire motion was purely translational, while in the second technique the wire was moved along a circular path. The induced voltage in the Litz wire was input into a Walker integrator, and the integrator output was analyzed as a function of wire position for determination of the multipole content of the magnetic field. The mini-undulator magnet is a 10 period, 80 mm per period hybrid insertion device. For all the data contained herein the magnet gap was set at 49 mm. In the mini-undulator magnet, the iron poles are 18mm x 32mm x 86 mm, and the Samarium Cobalt permanent magnet blocks are 22mm x 21mm x 110mm. For this magnet, which is a shortened prototype for the NSLS Soft X-Ray Undulator Magnet, the undulator parameter K = 0.934 B (Tesla){lambda}(cm), and B(tesla) = 0.534/sinh({pi}Gap/{lambda}). At a gap of 49 mm, the magnetic field is 1590 Gauss.
Date: May 1, 1998
Creator: Solomon, L.
Partner: UNT Libraries Government Documents Department