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The Brown-Servranckx matching transformer for simultaneous RFQ to DTL H{sup +} and H{sup {minus}} matching

Description: The issue involved in simultaneous matching of H{sup +} and H{sup -} beams between an RFQ and DTL lies in the fact that both beams experience the same electric-field forces at a given position in the RFQ. Hence, the two beams are focused to the same correlation. However, matching to a DTL requires correlation of the opposite sign. The Brown-Servranckx quarter-wave ({lambda}/4) matching transformer system, which requires four quadrupoles, provides a method to simultaneously match H{sup +} and H{sup -} beams between an RFQ and a DTL. The method requires the use of a special RFQ section to obtain the Twiss parameter conditions {beta}{sup x}={beta}{sup y} and {alpha}{sub x}={alpha}{sub y}=0 at the exit of the RFQ. This matching between the RFQ and DTL is described.
Date: September 1, 1996
Creator: Wadlinger, E.A. & Garnett, R.W.
Partner: UNT Libraries Government Documents Department

The linear parameters and the decoupling matrix for linearly coupled motion in 6 dimensional phase space. Informal report

Description: It will be shown that starting from a coordinate system where the 6 phase space coordinates are linearly coupled, one can go to a new coordinate system, where the motion is uncoupled, by means of a linear transformation. The original coupled coordinates and the new uncoupled coordinates are related by a 6 {times} 6 matrix, R. R will be called the decoupling matrix. It will be shown that of the 36 elements of the 6 {times} 6 decoupling matrix R, only 12 elements are independent. This may be contrasted with the results for motion in 4-dimensional phase space, where R has 4 independent elements. A set of equations is given from which the 12 elements of R can be computed from the one period transfer matrix. This set of equations also allows the linear parameters, {beta}{sub i}, {alpha}{sub i} = 1, 3, for the uncoupled coordinates, to be computed from the one period transfer matrix. An alternative procedure for computing the linear parameters, the {beta}{sub i}, {alpha}{sub i} i = 1, 3, and the 12 independent elements of the decoupling matrix R is also given which depends on computing the eigenvectors of the one period transfer matrix. These results can be used in a tracking program, where the one period transfer matrix can be computed by multiplying the transfer matrices of all the elements in a period, to compute the linear parameters {alpha}{sub i} and {beta}{sub i}, i = 1, 3, and the elements of the decoupling matrix R. The procedure presented here for studying coupled motion in 6-dimensional phase space can also be applied to coupled motion in 4-dimensional phase space, where it may be a useful alternative procedure to the procedure presented by Edwards and Teng. In particular, it gives a simpler programming procedure for computing the beta ...
Date: March 1, 1995
Creator: Parzen, G.
Partner: UNT Libraries Government Documents Department

Linear optics correction in the CEBAF accelerator

Description: During commissioning of the CEBAF accelerator, correcting dispersion, momentum compaction and betatron beam envelopes was essential for robust operation. To speed the diagnostic process we developed a method which allows one to track and correct the machine optics on-line. The method is based on measuring the propagation of 30 Hz modulated betatron oscillations. The beam optics of the accelerator was altered to decrease lattice sensitivity at critical points and to simplify control of the betatron function match. The calculation of the Courant-Snyder invariant from signals of each pair of beam position monitors was used for a correction of the betatron functions. The experience of optics correction and the study of long and short term machine reproducibility obtained during 1996 and early 1997 are also discussed. With minor modifications this method can also be used for on-line optics measurement and correction in circular accelerators.
Date: June 1, 1997
Creator: Lebedev, V.A.; Bickley, M. & Bisognano, J.
Partner: UNT Libraries Government Documents Department

Perturbation of the periodic dispersion under beam crossing optics in LHC

Description: Beam crossing and separation schemes in the LHC interaction regions impose non-zero closed orbit in the low-{beta} triplets. The related perturbative dispersion is derived ; propagation, multi-crossing interference, perturbative effects around the ring are investigated and quantified. Horizontal and vertical compensation schemes are presented.
Date: May 1, 1997
Creator: Meot, F.
Partner: UNT Libraries Government Documents Department

Low energy ring lattice of the PEP-II asymmetric B-Factory

Description: Developing a lattice that contains a very low beta value at the interaction point (IP) and has adequate dynamic aperture is one of the major challenges in designing the PEP-II asymmetric B-factory. For the Low Energy Ring (LER) the authors have studied several different chromatic correction schemes since the conceptual design report (CDR). Based on these studies, a hybrid solution with local and semi-local chromatic sextupoles has been selected as the new baseline lattice to replace the local scheme in the CDR. The new design simplifies the interaction region (IR) and reduces the number of sextupoles in the arcs. Arc sextupoles are paired at {pi} phase difference and are not interleaved. In this paper the authors describe the baseline lattice with the emphasis on the lattice changes made since the CDR.
Date: June 1, 1995
Creator: Cai, Y.; Donald, M.; Helm, R.; Irwin, J.; Nosochkov, Y.; Ritson, D.M. et al.
Partner: UNT Libraries Government Documents Department

Correction of vertical crossing induced dispersion in LHC

Description: Beam crossing schemes in the LHC interaction regions impose non-zero vertical closed orbit in the low-{beta} triplets, which excite a perturbative periodic dispersion ; the phenomenon is described and quantified in detail. It is shown that this dispersion reaches values at the limit of tolerances in the nominal optics of Version 5.0 of the LHC ring, and prohibitively large values in particular in the low- {beta} quadrupoles and interaction regions in the foreseen extreme {beta}-squeeze case ({beta}{sup *} = 0.25 m). Such behaviour justifies including a local correction in the LHC design, in order to damp the effect and confine it as much as possible in the vicinity of the excitation sources (the low-{beta} triplets). An optical compensation scheme based on the use of skew quadrupoles is described in detail, as well as the entailed residual dispersion.
Date: November 1, 1997
Creator: Meot, F.
Partner: UNT Libraries Government Documents Department

How to construct a second-order achromat with a 90 degree phase advance

Description: The author shows how to construct a second order achromatic (T{sub ij6} = 0, i, j {element_of} {l_brace}1,2{r_brace}) beamline with a total phase advance of 450{degree} (360{degree} + 90{degree}). The goal is to construct a 90{degree} cell which is achromatic to second order. One possible way to do this is to construct a 360{degree} sector followed by a 90{degree} cell; put dipoles and sextupoles in the 360{degree} sector; and throw the aberrations into the 90{degree} cell such that the final transformation is achromatic. The author expresses the aberrations in the 360{degree} sector in terms of the 90{degree} cell and determine whether any combination of sextupoles gives the correct cancellation.
Date: July 5, 2000
Creator: Kobilarcik, T.
Partner: UNT Libraries Government Documents Department


Description: For the year 2001 run, a bent crystal was installed in the yellow ring of the Relativistic Heavy Ion Collider (RHIC). The crystal forms the first stage of a two stage collimation system. By aligning the crystal to the beam, halo particles are channeled through the crystal and deflected into a copper scraper. The purpose is to reduce beam halo with greater efficiency than with a scraper alone. In this paper we present the first results from the use of the crystal collimator. We compare the crystal performance under various conditions, such as different particle species, and beta functions.
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department

DIMAD Based Interactive Simulation of the CEBAF Accelerator

Description: An X-Windows^(TM) based interactive interface to the DIMAD beam optics program enables users to simulate the adjustment of magnets in tuning various segments of the CEBAF beamline.In addition, users can track the effects of random errors on the path of individual particles as magnets are adjusted.The interface sits on top of the standard DIMAD model, retaining the detailed modeling available with that code.Because X-Windows software was used, the code is portable to any system that has X-Windows and the X-Windows Toolkit available.We give results from the studies simulating the extraction portion of the CEBAF beamline.
Date: May 1, 1991
Creator: Douglas, David & Bickley, Matthew
Partner: UNT Libraries Government Documents Department

Functional dependence, broad-band fitting, and ancillary conditions

Description: The ability to make multiple passes through a charged particle optical system, as a single step in a mathematical procedure, opens up new computational capa- bilities. At the simplest level, the functional dependence of any transfer matrix of any order, or any beam phase-space parameter can be plotted as a function of any other parameter used to describe the optical con#12;guration. Secondly, broad-band #12;tting can be done on aberrations, where all orders are considered simultaneously according to their importance on the #12;nal phase-space beam distribution. Finally, ancillary conditions may be imposed in the calculation of functional dependences. For example, the dependence of a matrix element on a beam line parameter may be calculated and plotted, subject to constraints imposed on other matrix elements. The computer program TRANSPORT now has these capabilities. Additional examples will be given.
Date: November 1, 1998
Creator: Carey, David C.
Partner: UNT Libraries Government Documents Department

Equal Optical Path Beam Splitters by Use of Amplitude-Splitting and Wavefront-Splitting Methods for Pencil Beam Interferometer.

Description: A beam splitter to create two separated parallel beams is a critical unit of a pencil beam interferometer, for example the long trace profiler (LTP). The operating principle of the beam splitter can be based upon either amplitude-splitting (AS) or wavefront-splitting (WS). For precision measurements with the LTP, an equal optical path system with two parallel beams is desired. Frequency drift of the light source in a non-equal optical path system will cause the interference fringes to drift. An equal optical path prism beam splitter with an amplitude-splitting (AS-EBS) beam splitter and a phase shift beam splitter with a wavefront-splitting (WS-PSBS) are introduced. These beam splitters are well suited to the stability requirement for a pencil beam interferometer due to the characteristics of monolithic structure and equal optical path. Several techniques to produce WS-PSBS by hand are presented. In addition, the WS-PSBS using double thin plates, made from microscope cover plates, has great advantages of economy, convenience, availability and ease of adjustment over other beam splitting methods. Comparison of stability measurements made with the AS-EBS, WS-PSBS, and other beam splitters is presented.
Date: August 3, 2003
Creator: Qian, S. & Takacs, P.
Partner: UNT Libraries Government Documents Department

Analyzing measurements of nonlinear transfer functions with Tschebyshev polynomials

Description: Recently, due to advances in computers and data aquisition systems, the following type of measurement has become more common: (1) Impress a given modulation on a device to be tested. (2) Acquire a data stream, usually at equally spaced sample intervals, of the response of the system to the modulation. (3) Fit the data thereby acquired to some nonlinear function set that might (or might not!) describe the response of the device. In this paper it is pointed out that by choosing to modulate the test parameter sinusoidally, and by fast-Fourier transforming the acquired data stream, one unambiguously determines the Tschebyshev expansion of the response function around the working point, potentially yielding quantitative information about high nonlinear orders in the system response. The need for data fitting is thereby eliminated. A detailed example, the analysis of the nonlinear phase-phase transfer function in the Jefferson Lab injector, is presented.
Date: June 1, 1997
Creator: Krafft, G. A.
Partner: UNT Libraries Government Documents Department

Notes on lie algebraic analysis of achromats

Description: Normal form technique is a powerful method to analyze the achromat problem. Assume the one cell map M{sub cell} = ARe{sup :h{sub 3}}:{sub e}{sup :h{sub 4}}: A{sup {minus}1}, where h{sub 3},h{sub 4} are the normal forms of the generators of the unit cell map, and A is the nonlinear transformation that brings M{sub cell} into its normal form; then the map of the whole system is M{sub N} = M{sub cell}{sup N} = AR{sup N} A{sup {minus}1} = I, provided that we can set e{sup :h{sub 3}}:, e{sup :h{sub 4}}, and R{sup N} to the identity (or only {delta} dependent) maps. Therefore, the conditions to form an achromat are h{sub 3} and h{sub 4} equal to zero (or {delta} dependent only) and the total linear map is identity. In this report, we will apply these conditions to a FODO array (a simple model system) to make it an achromat. We will start from Hamiltonians and work all the way up to obtain the analytical expressions of the required sextupole and octupole strengths.
Date: January 1, 1995
Creator: Wang, Chunxi & Chao, A.
Partner: UNT Libraries Government Documents Department

3-D electromagnetic modeling of wakefields in accelerator components

Description: We discuss the use of 3-D finite-difference time-domain (FDTD) electromagnetic codes for modeling accelerator components. Computational modeling of cylindrically symmetric structures such as induction accelerator cells has been very successful in predicting the wake potential and wake impedances of these structures, but full 3-D modeling of complex structures has been limited due to substantial computer resources required for a full 3-D model. New massively parallel 3-D time domain electromagnetic codes now under development using conforming unstructured meshes allow a substantial increase in the geometric fidelity of the structures being modeled. Development of these new codes are discussed in context of applicability to accelerator problems. Various 3-D structures are tested with an existing cubical cell FDTD code and wake impedances compared with simple analytic models for the structures; results will be used as benchmarks for testing the new time time domain codes. Structures under consideration include a stripline beam position monitor as well as circular and elliptical apertures in circular waveguides. Excellent agreement for monopole and dipole impedances with models were found for these structures below the cutoff frequency of the beam line.
Date: September 18, 1996
Creator: Poole, B.R.; Caporaso, G.J.; Ng, Wang C.; Shang, C.C. & Steich, D.
Partner: UNT Libraries Government Documents Department


Description: Beam stability up the ramp requires the appropriate sign and magnitude of the chromaticity. We developed a way to measure the chromaticity using the PLL (Phase Locked Loop) tune-meter. Since, the accuracy of the PLL tune-meter with properly adjusted loop gain is better than {approx} 0.0001 in tune units, the radial loop needs only be changed by a small amount of 0.2mm at a 1Hz rate. Thus, we can achieve fast chromaticity measurements in 1 sec. Except during the very beginning of the ramp where there are snapback effects and the gamma changes very rapidly, we can have good chromaticcity measurements along the ramp. This leads to the possibility of correcting the chromaticity during the ramp using a feedback system.
Date: June 2, 2002
Partner: UNT Libraries Government Documents Department

Compendation of SSC lattice optics in the presence of dipole field errors: Report of the Correction Element Working Group

Description: The assignment of the Correction Element Working Group (CEWG) is to advance the designs of various candidate correction schemes to a point where they can be compared and distilled down to a single plan. Choosing among, the options often involves consideration of incommensurate factors such as cost, practicality, and theoretical performance. Except for minor issues, the CEWG purpose is to gather and array the facts in a form from which these decisions can be rationally made, but not to make the decisions. The present report analyses various schemes for compensating nonlinear multipole errors in the main arc dipoles of the Superconducting Super Collider. Emphasis is on comparing lumped and distributed compensation, on minimizing the total number of correction elements, and on reducing the sensitivity to closed-orbit errors.
Date: February 1, 1989
Creator: Bintinger, D.; Chao, A. & Forest, E.
Partner: UNT Libraries Government Documents Department

Expanded studies of linear collider final focus systems at the Final Focus Test Beam

Description: In order to meet their luminosity goals, linear colliders operating in the center-of-mass energy range from 3,50 to 1,500 GeV will need to deliver beams which are as small as a few Manometers tall, with x:y aspect ratios as large as 100. The Final Focus Test Beam (FFTB) is a prototype for the final focus demanded by these colliders: its purpose is to provide demagnification equivalent to those in the future linear collider, which corresponds to a focused spot size in the FFTB of 1.7 microns (horizontal) by 60 manometers (vertical). In order to achieve the desired spot sizes, the FFTB beam optics must be tuned to eliminate aberrations and other errors, and to ensure that the optics conform to the desired final conditions and the measured initial conditions of the beam. Using a combination of incoming-beam diagnostics. beam-based local diagnostics, and global tuning algorithms, the FFTB beam size has been reduced to a stable final size of 1.7 microns by 70 manometers. In addition, the chromatic properties of the FFTB have been studied using two techniques and found to be acceptable. Descriptions of the hardware and techniques used in these studies are presented, along with results and suggestions for future research.
Date: December 1, 1995
Creator: Tenenbaum, P.G.
Partner: UNT Libraries Government Documents Department

Observations of collective effects at the Advanced Light Source

Description: We present a summary of measurements of single beam collective effects in the Advanced Light Source (ALS). We describe measurements of coupled-bunch instabilities, including some recent results using the newly commissioned feedback systems and the results of an initial search for the fast ion instability. Single bunch effects include bunch lengthening, energy spread increase, HOM loss measurements, head-tail damping rates, current dependent tune shifts, and transverse mode coupling instability threshold. The longitudinal measurements are consistent with a broadband impedance {vert_bar}{Zeta}{sub {parallel}}/{eta}{vert_bar}{sub eff} = 0.22{plus_minus}0.07 {Omega} and transverse measurements indicate broadband impedances of {Zeta}{sub y,eff} = 155 k{Omega}/m and Z{sub x,eff} = 58 k{Omega}/m.
Date: October 1, 1995
Creator: Byrd, J.M.; Barry, W.; Corlett, J.N.; Fox, J. & Teytelman, D.
Partner: UNT Libraries Government Documents Department

Modified Aladdin lattice N30

Description: By offsetting the quadrupole doublets after the dipoles, access to the photon beam lines was made more convenient, but destroys the symmetry of the element placement. The common bussing of the quadrupole doublets and the triplets make the Twiss functions asymmetric through the long straight section and a large negative dispersion in this region. The large value of dispersion around the period, although not by itself bad, limits the natural emittance of this lattice and makes resonance corrections difficult without influencing the chromatic properties of this lattice.
Date: April 1, 1985
Creator: Kramer, S. & Cho, Y.
Partner: UNT Libraries Government Documents Department

A multi-wire beam profile monitor in the AGS

Description: A multi-wire beam profile monitor which can be used to directly monitor and control the optical matching between the Booster and AGS rings has been installed and tested in the AGS. Placement of a multi-wire monitor directly in the AGS provides profile measurements taken upon injection and the first two or more revolutions of the beam. The data from such measurements can be used to determine the optical properties of the beam transport line leading into the AGS.
Date: July 1, 1997
Creator: Huang, H.; Buxton, W.; Castillo, V. & Glenn, J.W.
Partner: UNT Libraries Government Documents Department

Preliminary thoughts on the Aladdin experiments

Description: The author suggests three sets of experiments for comparing tracking results with experimental data on the dynamic aperture in Aladdin. They are: (1) aperture determined by a single dominant resonance; (2) dominance by a group of intersecting resonances; and (3) many non-intersecting resonances. Note that one advantage of the suggested experiments is that one can inject, accelerate, and get set for the experiment, and then excite the driving terms slowly, watching the aperture.
Date: November 1, 1987
Creator: Symon, K.
Partner: UNT Libraries Government Documents Department