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Summary report on transverse emittance preservation

Description: During the past years, significant progress has been made in understanding the beam transverse emittance blow-up and its preservation. However, one often finds him-/herself ignorant when he/she tries to explain what was observed in an existing machine or to predict what will happen in a machine under design. There are a number of such examples given in this report. Some of them are even fundamental. These are the challenges. But they are also the directions leading to new achievements. The workshop gladly acknowledged them and promised to work on them.
Date: December 1, 1997
Creator: Chou, W. & Vos, L.
Partner: UNT Libraries Government Documents Department

Emittance growth from bend straight transitions for beams approaching thermal equilibrium

Description: In certain applications such as heavy ion fusion, intense beams with large space charge tune depressions will be transferred from linear transport sections into bent, transport, sections. In some. designs, such as recircutating induction accelerators, transport. through bends will occur over thousands of betatron periods and in some driver designs the final transports through a bend will occur over tens of betatron periods. Over such distances, non-linear space charge forces are expected to produce particle phase space distributions which are close to thermal equilibrium, especially with respect to lower order moments. Here we calculate the properties of thermal equilibrium beams in bends assuming uniform focusing, as a function of two dimensionless parameters. We also outline the calculation of the change in emittance for a beam that is initially in thermal equilibrium in a straight transport section. and that finally reaches thermal equilibrium in a bent system, using an energy conservation constrint to connect, the two states.
Date: August 19, 1998
Creator: Barnard, J. J. & Losic, B.
Partner: UNT Libraries Government Documents Department

Emittance dilution due to slow alignment drifts in the main linacs of the NLC

Description: The tight tolerances in the main linacs of the Nest Linear Collider (NLC) result in a large sensitivity of the beam emittance to slow alignment drifts. Once the accelerator is tuned, the optimized emittances must be maintained. Slow alignments drifts will make resteering and reoptimization necessary. The frequency of these linac reoptimizations is an important parameter that determines how well the linear collider can be operated. We present simulation results that address this question for the main linacs of the NLC. We will show that the effects of alignment drifts can indeed be handled.
Date: September 1, 1996
Creator: Assmann, R.; Adolphsen, C. & Bane, K.
Partner: UNT Libraries Government Documents Department

Studies of emittance growth in the ATF

Description: Several different mechanisms of emittance growth in the Accelerator Test Facility (ATF) at KEK are investigated: the author calculates rise times of the fast beam-ion instability for the damping ring (DR), and discusses the emittance growth caused by coherent synchrotron radiation in the beam-transport line (BT), the effect of quadrupole wake fields in the injector linac, and, finally, a single-bunch head-tail ion effect that can occur in both the DR and the BT. A first attempt to measure the quadrupole wake on the real machine is also reported.
Date: March 1, 1997
Creator: Zimmermann, F.
Partner: UNT Libraries Government Documents Department

Recent transition crossing results from the Fermilab Main Ring

Description: This paper outlines the known mechanisms for emittance dilution and beam loss during transition crossing. These include scraping, Johnsen`s nonlinear effect, bunch length mismatch, microwave and negative-mass instabilities, and beam loading. A recent experiment on transition crossing performed with 13 proton bunches injected into the Main Ring is discussed.
Date: March 1, 1997
Creator: Bhat, C.M. & Ng, K.Y.
Partner: UNT Libraries Government Documents Department

Beam emittance measurements on multicusp ion sources

Description: Multicusp ion sources are used for various applications. Presently, the implementation of this type of ion source planned for the development of an ion beam lithography machine, which will be used for the projection of sub-0.2 {mu}m patterns onto a wafer substrate. Since, for this application, a very good beam quality and a small ion energy spread are required, emittance measurements have been performed on a multicusp ion source for various source conditions. It is shown that the installation of proper capacitors between the extraction electrodes is necessary to avoid rf-pickup, which otherwise leads to a distortion of the beam emittance. The influence of the magnetic filter field on the beam emittance has been investigated, and the beam emittance of a dc filament-discharge plasma has also been compared to that of an rf-generated plasma.
Date: August 1, 1995
Creator: Sarstedt, M.; Lee, Y. & Leung, K.N.
Partner: UNT Libraries Government Documents Department

Accurate Iterative Analysis Solution of theKapchinskij-Vladimirskij Equations for the Case of a Matched Beam

Description: The well-known Kapchinskij-Vladimirskij (KV) equations are difficult to solve in general, but the problem is simplified for the matched-beam case with sufficient symmetry. They show that the interdependence of the two KV equations is eliminated, so that only one needs to be solved--a great simplification. They present an iterative method of solution which can potentially yield any desired level of accuracy. The lowest level, the well-known smooth approximation, yields simple, explicit results with good accuracy for weak or moderate focusing fields. The next level improves the accuracy for high fields; they previously showed [Part. Accel. 52, 133 (1996)] how to maintain a simple explicit format for the results. That paper used expansion in a small parameter to obtain results of second-level accuracy. The present paper, using straightforward iteration, obtains equations of first, second, and third levels of accuracy. For a periodic lattice with beam matched to lattice, they use the lattice and beam parameters as input and solve for phase advances and envelope functions. They find excellent agreement with numerical solutions over a wide range of beam emittances and intensities.
Date: January 31, 2007
Creator: Anderson, O.A.
Partner: UNT Libraries Government Documents Department

IMPACT simulation and the SNS linac beam

Description: Multi-particle tracking simulations for the SNS linac beam dynamics studies are performed with the IMPACT code. Beam measurement results are compared with the computer simulations, including beam longitudinal halo and beam losses in the superconducting linac, transverse beam Courant-Snyder parameters and the longitudinal beam emittance in the linac. In most cases, the simulations show good agreement with the measured results.
Date: September 3, 2008
Creator: Zhang, Y. & Qiang, J.
Partner: UNT Libraries Government Documents Department

Emittance measurements in the ALS booster synchrotron

Description: Beam emittance measurements in the Advanced Light Source Booster Synchrotron are presented. Electrons are injected at 50 MeV and extracted at various energies ranging from 150 MeV to 1,520 MeV. The extracted beam is then transported in the Booster-to-Storage-Ring beam transfer line where the emittances are measured. Beam sizes are measured at 7 locations using scintillators and CCD cameras. The measured emittances are then compared with the theory based on intra- beam scattering, betatron coupling, radiation damping, and radiation excitation.
Date: May 1, 1995
Creator: Massoletti, D.; Kim, C.H. & Jackson, A.
Partner: UNT Libraries Government Documents Department

Entropy and emittance of particle and photon beams

Description: The emittance as the available phase space area is defined as the product of the elementary cell area {delta}{Omega} and exp(S), where S is the normalized entropy of a particle beam. The definition is based on the fact that the factor exp(S) can be interpreted as the number of the occupied cells. For particle beams, a closed expression for the emittance in terms of the phase space distribution function is obtained which is independent of {delta}{Omega}. To compute the emittance of the radiation beam, it is necessary to find the eigenvalues of the correlation operator. An explicit solution is found for the case of a partially coherent radiation beam which is a stochastic superposition of coherent Gaussian beams with a Gaussian probability distribution. Such a beam is a reasonable model for undulator radiation by beam of electrons. From the requirement that the radiation emittance reproduces the particle beam emittance in the incoherent limit, the elementary cell area {delta}{Omega} is determined unambiguously to be {lambda}, the radiation wavelength. The emittance in the incoherent limit then becomes {lambda}.
Date: April 1, 1995
Creator: Kim, K.J. & Littlejohn, R.G.
Partner: UNT Libraries Government Documents Department

Apiary B Factory Lattice Design

Description: The Apiary B Factory is a proposed high-intensity electron-positron collider. This paper presents the lattice design for this facility, which envisions two rings with unequal energies in the PEP tunnel. The design has many interesting optical and geometrical features due to the needs to conform to the existing tunnel, and to achieve the necessary emittances, damping times and vacuum. Existing hardware is used to a maximum extent.
Date: May 3, 1991
Creator: Donald, M.H.R. & Garren, A.A.
Partner: UNT Libraries Government Documents Department

A program to research emittance growth in bends

Description: A research program to explore the phenomenon of emittance growth in bends due to noninertial space-charge effects has been defined and initiated. The program combines theoretical, numerical, and experimental investigations. This paper summarizes the motivation of the work and highlights CEBAF`s need for immediate results. The program`s key elements, some of which qualitatively differ from the standard approach used to investigate the production and effects of coherent synchrotron radiation in synchrotrons and storage rings, are enumerated and discussed. 1 fig.
Date: December 31, 1995
Creator: Bohn, C.L.
Partner: UNT Libraries Government Documents Department

Location and correction of 60 hz in the CEBAF injector

Description: CEBAF produces a continuous electron beam with an emittance of 2-3 nm-rad. Transverse low frequency magnetic oscillations act to dilute this emittance. These fields are typically associated with AC line conductors. The CEBAF injector is approximately 40 m long. To locate the source(s) of the beam motion, measured offsets were back propagated along the beamline using the DIMAD model. Field measurements were then made at the calculated field source positions and correlated with the measured effects. Corrections and final beam measurements were made to verify the corrections. 2 refs., 4 tabs.
Date: August 1, 1996
Creator: Legg, R.; Douglas, D.; Krafft, G.A. & Saulter, Q.
Partner: UNT Libraries Government Documents Department

Analysis of the January 2006 Pepper-Pot Experiments

Description: Between January 9-12, 2006 a series of experiments were performed on the DARHT-II injector to measure the beam's emittance. Part of these experiments were pepper-pot measurements. This note describes the analysis of the data, and our conclusions from the experiments.
Date: March 22, 2006
Creator: Westenskow, G; Chambers, F; Bieniosek, F & Henestroza, E
Partner: UNT Libraries Government Documents Department

Space charge stopband correction

Description: It is speculated that the space charge effect cause beam emittance growth through the resonant envelope oscillation. Based on this theory, we propose an approach, called space charge stopband correction, to reduce such emittance growth by compensation of the half-integer stopband width of the resonant oscillation. It is illustrated with the Fermilab Booster model.
Date: September 1, 2005
Creator: Huang, Xiaobiao; U., /Fermilab /Indiana; Lee, S.Y. & U., /Indiana
Partner: UNT Libraries Government Documents Department

Procurement history of the hybrid undulator for the U-5 Beam Line at the National Synchrotron Light Source

Description: As part of a national multi-institutional Materials Research Group (MRG), Argonne National Laboratory had the responsibility, under a prime contract with the U.S. Department of Energy, of obtaining a Permanent Magnet Hybrid undulator to be used on the U5 Beam Line on the VUV Ring at the National Synchrotron Light Source (NSLS). The procurement involved determining the technical specifications of the device as well as developing an effective procedure for evaluation of the proposals. The conceptual design of the magnetic structure including all pertinent magnetic field properties was developed before the actual procurement process was initiated. In addition, complete calculations of the expected spectral properties of the undulator were performed which included the emittance properties of the VUV ring. The results from both analysis were essential in determining the expected performance of the device and the final choice of operating parameters.
Date: May 1, 1989
Creator: James, D.C.; Bader, S.D. & Viccaro, P.J.
Partner: UNT Libraries Government Documents Department

APS undulator radiation: First results

Description: The first undulator radiation has been extracted from the Advanced Photon Source (APS). The results from the characterization of this radiation are very satisfactory. With the undulator set at a gap of 15.8 mm (K=1.61), harmonics as high as the 17th were observed using a crystal spectrometer. The angular distribution of the third-harmonic radiation was measured, and the source was imaged using a zone plate to determine the particle beam emittance. The horizontal beam emittance was found to be 6.9 {plus_minus} 1.0 nm-rad, and the vertical emittance coupling was found to be less than 3%. The absolute spectral flux was measured over a wide range of photon energies, and it agrees remarkably well with the theoretical calculations based on the measured undulator magnetic field profile and the measured beam emittance. These results indicate that both the emittance of the electron beam and the undulator magnetic field quality exceed the original specifications.
Date: December 31, 1995
Creator: Cai, Z.; Dejus, R.J. & Hartog, P.D.
Partner: UNT Libraries Government Documents Department

Injecting a Kapchinskij-Vladimirskij distribution into a proton synchrotron

Description: Recently it has been suggested that the Kapchinskij Vladimirskij (KV) distribution may be of practical interest for high intensity machines in that it may provide the maximum space charge limit for such a machine. One can be make a plausible argument that the maximum beam intensity is obtained for a distribution for which all particles have the same tune, at least when the resonance is approached. Therefore, the following steps should be taken: first, reduce the chromaticity of the accelerator ring as much as possible, and second, make the betatron frequencies independent of amplitude, i.e., make the focusing forces linear. One way to make the focusing forces linear is to start with external focusing forces which are linear, and then make the space charge forces also linear by using a K-V distribution. Sections II and III describe two injection scenarios which produce a KV distribution (if we neglect beam-beam interactions during the injection process.) Simulations of these injection scenarios verify that the resulting distribution produces a uniform circular beam in xy-space. A simulation code was written which also includes the space charge interactions between the 500 injected turns in the proposed scenarios; the results are given in section IV. The space charge forces have a substantial effect on the resulting distribution.
Date: July 1, 1995
Creator: Crosbie, E. & Symon, K.
Partner: UNT Libraries Government Documents Department

The advanced photon source

Description: The Advanced Photon Source (APS) is a 7-GeV third-generation synchrotron radiation storage ring and full-energy positron injector. Construction project funding began in 1989, and ground breaking took place on 5 May 1990. Construction of all accelerator facilities was completed in January 1995 and storage ring commissioning is underway. First observation of x-rays from a bending magnet source took place on 26 March 1995. Nearly all performance specifications of the injector have been reached, and first observations indicate that the reliability, dynamic aperture, emittance, and orbit stability in the storage ring are satisfactory. Observation of radiation from the first of 20 insertion device beamlines is scheduled for October 1995. Start of regular operations is expected to take place well before the APS Project target date of December 1996.
Date: July 1, 1995
Creator: Galayda, J.N.
Partner: UNT Libraries Government Documents Department