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The ever increasing demands placed upon machine performance have resulted in the need for more comprehensive particle accelerator modeling. Computer simulations are key to the success of particle accelerators. Many aspects of particle accelerators rely on computer modeling at some point, sometimes requiring complex simulation tools and massively parallel supercomputing. Examples include the modeling of beams at extreme intensities and densities (toward the quantum degeneracy limit), and with ultra-fine control (down to the level of individual particles). In the future, adaptively tuned models might also be relied upon to provide beam measurements beyond the resolution of existing diagnostics. Much time and effort has been put into creating accelerator software tools, some of which are highly successful. However, there are also shortcomings such as the general inability of existing software to be easily modified to meet changing simulation needs. In this paper possible mitigating strategies are discussed for issues faced by the accelerator community as it endeavors to produce better and more comprehensive modeling tools. This includes lack of coordination between code developers, lack of standards to make codes portable and/or reusable, lack of documentation, among others., 21 pages, 1 figure. To be published in JINST

The design and implementation of new beamlines featuring side-bounce (single-reflection) diamond monochromators at Cornell High Energy Synchrotron Source (CHESS) are described. Undulator radiation is monochromated using an interchangeable set of diamond crystal plates reflecting radiation in the horizontal (synchrotron) plane, where each crystal plate is set to one of the low-index Bragg reflections (111, 220, 311 and 400) in either Bragg or Laue reflection geometries. At the nominal Bragg angle of 18° these reflections deliver monochromated X-rays with photon energies of 9.7, 15.9, 18.65 and 22.5 keV, respectively. An X-ray mirror downstream of the diamond monochromator is used for rejection of higher radiation harmonics and for initial focusing of the monochromated beam. The characteristics of the X-ray beam entering the experimental station were measured experimentally and compared with the results of simulations. A reasonable agreement is demonstrated. It is shown that the use of selected high-dislocation-density `mosaic' diamond single-crystal plates produced using the chemical vapor deposition method yields a few-fold enhancement in the flux density of the monochromated beam in comparison with that delivered by perfect crystals under the same conditions. At present, the Functional Materials Beamline at CHESS, which is used for time-resolved in situ characterization of soft materials during processing, has been outfitted with the described setup.

Energy recovery has been achieved in a multipass linear accelerator, demonstrating a technology for more compact particle accelerators operating at higher currents and reduced energy consumption. Energy delivered to the beam during the first four passes through the accelerating structure was recovered during four subsequent decelerating passes. High-energy efficiency was achieved by the use of superconducting accelerating cavities and permanent magnets. The fixed-field alternating-gradient optical system used for the return loop successfully transported electron bunches of 42, 78, 114, and 150 MeV in a common vacuum chamber. This new kind of accelerator, an eight-pass energy recovery linac, has the potential to accelerate much higher current than existing linear accelerators while maintaining small beam dimensions and consuming much less energy per electron.

At high proton-beam energies, beam-induced synchrotron radiation is an important source of heating, of beam-related vacuum pressure increase, and of primary photoelectrons, which can give rise to an electron cloud. We use the Synrad3D code developed at Cornell to simulate the photon distributions in the arcs of several existing, planned, or proposed highest-energy hadron colliders to analyze the efficiency of several techniques developed, or proposed, to mitigate the negative effects of synchrotron radiation, such as a sawtooth surface and slots in the beam screen.

The Cornell Electron-positron Storage Ring (CESR) has been converted from a High Energy Physics electron-positron collider to operate as a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS) and to conduct accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Some of the specific topics that were targeted for the initial phase of operation of the storage ring in this mode, labeled CESRTA (CESR as a Test Accelerator), included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CESRTA occurred over a several year period and is described elsewhere. As a part of this conversion the CESR beam position monitoring (CBPM) system was completely upgraded to provide the needed instrumental capabilities for these studies. This paper describes the new CBPM system hardware, its function and representative measurements performed by the upgraded system.

An accurate calculation of the synchrotron radiation flux within the vacuum chamber of an accelerator is needed for a number of applications. These include simulations of electron cloud effects and the design of radiation masking systems. To properly simulate the synchrotron radiation, it is important to include the scattering of the radiation at the vacuum chamber walls. To this end, a program called synrad3d has been developed which simulates the production and propagation of synchrotron radiation using a collection of photons. Photons generated by a charged particle beam are tracked from birth until they strike the vacuum chamber wall where the photon is either absorbed or scattered. Both specular and diffuse scattering is simulated. If a photon is scattered, it is further tracked through multiple encounters with the wall until it is finally absorbed. This paper describes the synrad3d program, with a focus on the details of its scattering model, and presents some examples of the program’s use.

The Cornell Electron-positron Storage Ring (CESR) has been converted from a High Energy Physics electron-positron collider to operate as a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS) and to conduct accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Some of the specific topics that were targeted for the initial phase of operation of the storage ring in this mode for CESR as a Test Accelerator (CesrTA) included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CesrTA occurred over a several year period, described elsewhere. In addition to instrumentation for the storage ring, which was created for CesrTA, existing instrumentation was modified to facilitate the entire range of investigations to support these studies. Procedures were developed, often requiring coordinated measurements among different instruments. This paper describes the instruments utilized for the study of beam dynamics during the operation of CesrTA. The treatment of these instruments will remain fairly general in this paper as it focusses on an overview of the instruments themselves. Their interaction and inter-relationships during sequences of observations is found in a companion paper describing the associated measurement techniques. More detailed descriptions and detailed operational performance for some of the instrumentation may be found elsewhere and these will be referenced in the related sections of this paper.

The Cornell-Brookhaven CBETA machine is a four-pass Energy Recovery Linac (ERL) with a Non-scaling Fixed-Field Alternating gradient (NS-FFA) arc. For online modeling of single particle dynamics in CBETA, a customized version of the Tao program, which is based upon the Bmad toolkit, has been developed. This online program, called CBETA-V, is interfaced to CBETA’s EPICS control system. This work describes the online modeling system and initial experience during machine running, as well as subsequent developments since its first implementation.

After operating as a High Energy Physics electron-positron collider, the Cornell Electron-positron Storage Ring (CESR) has been converted to become a dedicated synchrotron light source for the Cornell High Energy Synchrotron Source (CHESS). Over the course of several years CESR was adapted for accelerator physics research as a test accelerator, capable of studying topics relevant to future damping rings, colliders and light sources. Initially some specific topics were targeted for accelerator physic research with the storage ring in this mode, labeled CesrTA. These topics included 1) tuning techniques to produce low emittance beams, 2) the study of electron cloud (EC) development in a storage ring and 3) intra-beam scattering effects. The complete conversion of CESR to CesrTA occurred over a several year period, described elsewhere [1–3]. A number of specific instruments were developed for CesrTA. Much of the pre-existing instrumentation was modified to accommodate the scope of these studies and these are described in a companion paper [4]. To complete this research, a number of procedures were developed or modified, often requiring coordinated measurements among different instruments [5]. This paper provides an overview of types of measurements employed for the study of beam dynamics during the operation of CesrTA.

Bmad is a subroutine library for simulating relativistic charged particle beams in high-energy accelerators and storage rings. Bmad can be used to study both single and multi-particle beam dynamics using routines to track both particles and macroparticles. Bmad has various tracking algorithms including Runge–Kutta and symplectic (Lie algebraic) integration. Various effects such as wakefields, and radiation excitation and damping can be simulated. Bmad has been developed in a modular, object-oriented fashion to maximize flexibility. Interface routines allow Bmad to be called from C / C ++ as well as Fortran programs. Bmad is well documented. Every routine is individually annotated, and there is an extensive manual.

In 2008 the Cornell Electron/Positron Storage Ring (CESR) was reconfigured from an electron/positron collider to serve as a test bed for the International Linear Collider damping rings. One of the primary goals of the CESR Test Accelerator (CesrTA) project is to develop a fast low-emittance tuning method which scales well to large rings such as the ILC damping rings, and routinely achieves a vertical emittance of order 10 pm at 2.085 GeV. This paper discusses the tuning methods developed at CesrTA to achieve low-emittance conditions. One iteration of beam-based measurement and correction requires about 10 min. A minimum vertical emittance of $10.3(+3.2/\ensuremath{-}3.4{)}^{\text{sys}}(\ifmmode\pm\else\textpm\fi{}0.2{)}^{\text{stat}}\text{ }\mathrm{pm}$ has been achieved at 2.085 GeV. In various configurations and beam energies the correction technique routinely achieves vertical emittance around 10 pm after correction, with rms coupling $l0.5%$. The measured vertical dispersion is dominated by beam position monitor systematics. The propagation of uncertainties in the emittance measurement is described in detail. Simulations modeling the effects of magnet misalignments, beam position monitor errors, and the emittance correction algorithm suggest the residual vertical emittance measured at the conclusion of the tuning procedure is dominated by sources other than optics errors and misalignments.

In storage rings, horizontal dispersion in the rf cavities introduces horizontal-longitudinal (xz) coupling, contributing to beam tilt in the xz plane. This coupling can be characterized by a "crabbing" dispersion term {\zeta}a that appears in the normal mode decomposition of the 1-turn transfer matrix. {\zeta}a is proportional to the rf cavity voltage and the horizontal dispersion in the cavity. We report experiments at the Cornell Electron Storage Ring Test Accelerator (CesrTA) where xz coupling was explored using three lattices with distinct crabbing properties. We characterize the xz coupling for each case by measuring the horizontal projection of the beam with a beam size monitor. The three lattice configurations correspond to a) 16 mrad xz tilt at the beam size monitor source point, b) compensation of the {\zeta}a introduced by one of two pairs of RF cavities with the second, and c) zero dispersion in RF cavities, eliminating {\zeta}a entirely. Additionally, intrabeam scattering (IBS) is evident in our measurements of beam size vs. rf voltage., Comment: 5 figures, 10 pages

Intrabeam scattering (IBS) limits the emittance and single-bunch current that can be achieved in electron or positron storage ring colliders, damping rings, and light sources. Much theoretical work on IBS exists, and while the theories have been validated in hadron and ion machines, the presence of strong damping makes IBS in lepton machines a different phenomenon. We present the results of measurements at CesrTA of IBS-dominated beams, and compare the data with theory. The beams we study have parameters typical of those specified for the next generation of wiggler-dominated storage rings: low emittance, small bunch length, and an energy of a few GeV. Our measurements are in good agreement with IBS theory, provided a tail-cut procedure is applied.

The coherent interaction between the electron beam and trapped ions in the Cornell Electron/positron Storage Ring (CESR) has been seen by shaking the beam and observing the resulting beam oscillation amplitude. A linear theory is developed which enables the calculation of ion densities from the experimental measurements. Nonlinearities in the beam-ion force are shown to be important in understanding the ion trapping effects including frequency shifts of the betatron sideband resonances.

We describe the creation and trapping of ions by an electron beam and the coherent and incoherent instabilities that the trapped ions can cause. The transverse oscillations and longitudinal motion of the ions and the different methods of beam shaking are discussed. The movement of the ions are simulated with and without shaking. We explore the effect of shaking on the stability of ions, as well as the dependence of the size of the effect on the amplitude and frequency of shaking. The effect of neglecting the longitudinal and/or horizontal motion of the ions is studied. A short review is given of experimental work by others on the effects of shaking.

The open source Bmad software library, developed at Cornell University, has proved to be a useful tool for accelerator simulations owing to its modular, object-oriented design. Bmad has been used to simulate the storage ring CESR for many years, and to design and analyze the proposed Cornell Energy Recovery Linac. Work is ongoing to expand Bmad in a number of directions. In particular, the ability to be able to do a combined simulation of accelerated charged-particle beams and the x-ray beams they create is being developed. Ultimately a complete framework for simulations from the gun cathode (including space-charge) to x-ray generation, to x-ray tracking through to the experimental end-stations is envisioned. The flexibility of Bmad is such that multiple propagation algorithms can be accommodated with the user selecting the appropriate algorithm for each individual element. To this end, the integration of Bmad with the SHADOW tracking code is in development.

We describe a new technique for low-emittance tuning of electron and positron storage rings. This technique is based on calibration of the beam position monitors (BPMs) using excitation of the normal modes of the beam motion, and has benefits over conventional methods. It is relatively fast and straightforward to apply, it can be as easily applied to a large ring as to a small ring, and the tuning for low emittance becomes completely insensitive to BPM gain and alignment errors that can be difficult to determine accurately. We discuss the theory behind the technique, present some simulation results illustrating that it is highly effective and robust for low-emittance tuning, and describe the results of some initial experimental tests on the CesrTA storage ring.

The trapping of dust particles with an attendant reduction in beam lifetime and/or increased radiation rates is aperiodically observed in the Cornell Electron/positron Storage Ring CESR. A measurement of the stability of the trapped dust as a function of bunch current with a single bunch of electrons confirmed directly that the dust particles are heavier than any normal constituent of the residual gas in the vacuum chamber. The removal of individual dust particles from the beam via image charge forces were observed and the change in beam lifetime together with the current at which the dust left the beam permitted calculation of the dust mass and charge. The surface electric field of the dust particle as calculated from the experimental data agrees well with a theoretical calculation based upon an equilibrium between charging and discharging rates.

We report measurements of the dependence of luminosity and beam-beam tune-shift parameter on horizontal crossing angle at a single interaction point in the Cornell Electron Storage Ring. The report is based on data collected between September 1991 and January 1992 at CESR. For head-on collisions (zero crossing angle) the achieved tune-shift parameter is ξ v = 0.03 ± 0.002 at 11 mA/bunch. For a crossing half-angle of θ c = ± 2.4 mrad, we achieve ξ v = 0.024 ± 0.002 at similar bunch currents. The data suggest some degradation of performance if the trajectory through the interaction region is distorted magnetically even while head-on collisions are preserved. Therefore at least some of the observed dependence of tune-shift parameter on crossing angle may be due to the associated large displacement of the beam trajectories in the interaction region optics. Furthermore, with the introduction of the crossing angle, the algorithm for optimizing luminosity is significantly complicated due to linear optical errors and the solenoid compensation. We interpret the measured tune-shift parameter at θ c = 2.4 mrad as a lower limit to what can ultimately be achieved.

Laboratory of Elementary Particle Physics, Cornell University, Ithaca, New York 14853, USA(Received 27 April 2010; published 9 September 2010)Low emittance tuning at the Cornell Electron Storage Ring (CESR) test accelerator depends onprecision measurement of vertical dispersion and transverse coupling. The CESR beam position monitors(BPMs) consist of four button electrodes, instrumented with electronics that allow acquisition of turn-by-turn data. The response to the beam will vary among the four electrodes due to differences in electronicgain and/or misalignment. This variation in the response of the BPM electrodes will couple real horizontaloffset to apparent vertical position, and introduce spurious measurements of coupling and verticaldispersion. To alleviate this systematic effect, a beam based technique to measure the relative responseof the four electrodes has been developed. With typical CESR parameters, simulations show that turn-by-turn BPM data can be used to determine electrode gains to within 0:1%.

Coherent synchrotron radiation can severely limit the performance of accelerators designed for high brightness and short bunch length. Examples include light sources based on energy recovery LINAC or free-electron lasers, and bunch compressors for linear colliders. In order to better simulate coherent synchrotron radiation, a one-dimensional formalism due to Saldin, Schneidmiller, and Yurkov has been implemented in the general beam dynamics code Bmad. Wide vacuum chambers are simulated by means of vertical image charges. Results from Bmad are here compared to analytical approximations, to numerical solutions of the Maxwell equations, and to the simulation code ELEGANT and the code of Agoh and Yokoya.

Equations for the longitudinal component of the beam—ion kick are derived and it is shown that this component can play an important part in the longitudinal transport process. By combining the expression for the longitudinal kick with conservation of energy and conservation of horizontal action, one obtains an expression for the variation of the longitudinal velocity. This result is applied to the case of an ion traversing a dipole fringe field and to the case of an ion moving in a field free region. The analytical results agree well with simulation.

The goal of this project was to perform simulations of beam transport in linear colliders, with an emphasis on emittance dilution, spin polarization transport, and development and testing of beam based tuning algorithms. Our simulations are based on an existing object-oriented particle-tracking library, Bmad. To facilitate the efficient development of simulations, an accelerator design and analysis program based on Bmad has been developed called Tao (Tool for Accelerator Optics). The three beam-based alignment algorithms, Dispersion Free Steering, Ballistic Alignment (BA), and the Kubo Method have been implemented in Tao. We have studied the effects of magnet misalignments, BPM resolution, beam jitter, stray fields, BPM and steering magnet failure and the effects of various cavity shape wakefields. A parametric study has been conducted in the presence of the above types of errors for all three alignment algorithms. We find that BPM resolution has only modest impact on the effectiveness of beam based alignment. The DFS correction algorithm was found to be very robust in situations where there were BPM and/or steering magnet failures. The wakefields in the main linac are very weak and cause negligible emittance growth. Spin tracking was extended to study all accelerator components between the damping ring andmore » the interaction point, including RF cavities and the helical undulator. We find that there is no significant depolarization in the RTML, main linac or beam delivery system and that the polarization is relatively insensitive to misalignment. We have developed an effective spin rotator. During the final year of the grant we exploited the computing power of our new linux cluster, along with the modeling codes that we had developed, to investigate damping ring physics and design, specifically as it relates to the CESR Test Accelerator project.« less

The status of plans for an energy-recovery linac (ERL) X-ray facility at Cornell University are described. Cornell currently operates the Cornell high energy synchrotron source (CHESS) at the CESR ring. The ERL is planned to be an extension to that ring by a 5-GeV superconducting c.w. linac. The very small electron-beam emittances would produce an X-ray source that is considerably better than any existing storage-ring light source. The ERL design that is presented has to allow for non-destructive transport of these small emittances. It includes up to 18 X-ray beamlines for specific areas of research that are currently being defined by an international community. Special attention is given to reuse of many of the existing ring components. Here it is described which subjects are being investigated or will have to be studied at Cornell to prepare for the construction of this new hard X-ray source; references to other contributions to this conference (PAC07) demonstrate this effort. This project illustrates how existing storage rings could be upgraded as ERL light sources with vastly improved beam qualities and with limited dark time for X-ray users. The presented list of research topics shows R&D issues for any such upgrade project.

The main linac of the International Linear Collider (ILC) requires more sophisticated alignment techniques than those provided by survey alone. Various Beam-Based Alignment (BBA) algorithms have been proposed to achieve the desired low emittance preservation. Dispersion Free Steering, Ballistic Alignment and the Kubo method are compared. Alignment algorithms are also tested in the presence of an Earth-like stray field.

Bmad is a subroutine library for modeling relativistic charged-particle dynamics. It has been used extensively as a diagnostic tool at the Cornell Electron Storage Ring (CESR). The Bmad libraries have recently been extended to include modeling of the dynamics of linear accelerators. Calculations of emittance dilution due to orbit offsets and misalignments have been compared with LIAR, Merlin and PLACET. Good agreement is found with both particle and macroparticle tracking through the NLC and TESLA lattices for the bunch compressor, main linac and final focus regions.

A new accelerator design and analysis simulation program based on the Bmad relativistic charged particle dynamics library has been developed at Cornell University. Called Tao (Tool for Accelerator Optics), it implements the essential ingredients needed to solve many simulation problems. This includes the ability to design lattices subject to constraints, simulate errors and changes in machine parameters, and simulate machine commissioning including simulating data measurement and correction. Tao is designed to be easily customizable so that extending it to solve new and different problems is relatively straight forward. The capability to simultaneously model multiple accelerator lattices, both LINACs and storage rings, along with the ability to inject from one lattice to another allows for the design and commissioning of large multi stage accelerators.

In the Cornell Electron Storage Ring (CESR) multibunch beams of electrons and positrons share a common vacuum chamber and guide field. A new precision beam position monitor system, with bunch-by-bunch measurement capability, is now in operation in one sector of the CESR ring including the interaction region (IR). Two of our position monitors are located 67 cm on either side of the interaction point (IP) within the IT experimental solenoid. By measuring the relative positions of electron and positron bunches at these detectors we can obtain information about the displacement of the beams at the collision point with an anticipated resolution on the order of the vertical beam size. The measurement of the dependence of beam trajectories at these IR beam position monitors (IRBPMs) on changes in the ring steering elements provides a powerful diagnostic of guide field errors in the interaction region.

Recent interest in applications of wiggler magnets in storage rings has motivated efforts to incorporate their effects in calculations of beam dynamics. This paper presents an analytic model of wiggler fields that can be used with symplectic integration to evaluate such effects. Coefficients needed by the model are generated by fitting to the results of a finite-element field calculation. The model has been used successfully in the CESR-c project, which imposes tolerances of a few parts in 10/sup 4/ on the modeling of 2-Tesla superconducting wigglers. In contrast to models based on Fourier transforms, the model presented here uses a relatively small number of terms, leading to correspondingly fast integration times. Fringe fields are included and no assumption about the periodicity of the field is made.

Synchrotron light sources based on Energy Recovery Linacs (ERLs) show promise to deliver X-ray beams with both brilliance and X-ray pulse duration far superior to the values that can be achieved with storage ring technology. Cornell University, in collaboration with Jefferson Laboratory, has proposed the construction of a prototype ERL. This 100MeV, 100mA CW superconducting electron accelerator will be used to study and resolve the many accelerator physics and technology issues of this type of machine. These studies are essential before ERLs can be confidently proposed for large-scale applications such as synchrotron light sources. Key issues include the generation of high average current, high brightness electron beams; acceleration and transport of these beams while preserving their brightness; adequate damping of higher order modes (HOMs) to assure beam stability; removal of large amounts of HOM power from the cryogenic environment; stable RF control of cavities operating at very high external Q; reduction of beam losses to very low levels; and the development of precision non-intercepting diagnostics to allow beam setup, control and characterization. Our prototype design allows us to address these and other issues over a broad range of parameter space. This design, along with recent progress on understanding these issues, will be presented.

At the Cornell Electron/positron Storage Ring CESR, the measurement of the coupling between the horizontal and vertical beam motions has led to the ability to locate the position of a coupler and to calculate its strength. Once the identity of a coupler is known, steps can be taken to remove it or to nullify its effect. This coupling analysis can also be used to calibrate correction skew quadrupoles.

We present a status report on the investigation of the Mobius scheme for producing equal-emittance round beams at CESR. An insert has been constructed with six 45/spl deg/ rotated quadrupoles which interchange horizontal and vertical betatron oscillations on each passage. We describe the single-beam dynamics and the limitations introduced by the chromaticity correcting sextupoles. We also report on our two-beam experience.

The non-linear coupling due to the beam-beam interaction with crossing angle has been studied. The major effect of a small (/spl sim/12 mrad) crossing angle is to excite 5Q/sub xspl plusmn/Q/sub s/ integer coupling resonance family on large amplitude particles, which results in bad lifetime, On the CESR, a small crossing angle (/spl sim/2.4 mr) was created at the IP and a reasonable beam-beam tune-shift was achieved. The decay rate of the beam is measured as a function of horizontal tune with and without crossing angle. The theoretical analysis, simulation and experimental measurements have a good agreement. The resonance strength as a function of crossing angle is also measured. >

The Landau damping of the transverse oscillations of a relativistic bunch can be enhanced by creating an amplitude-dependent betatron tune spread in the bunch. This tune spread can be created by introducing octupole magnets into the lattice. In order to further the understanding of this mechanism, the authors conducted experiments in the Cornell Electron Storage Ring (CESR) where the tune spread of the beam has been measured via measurements of the damping of the centroid motion of the beam after the beam has been kicked. The turn-by-turn transient response of the transverse motion to excitation by injection kickers was measured as a function of octupole current and excitation amplitude. The experimental data are shown to be in good agreement with particle tracking results and the theory of octupole-induced decoherence. >

A new method of monitoring the luminosity has been developed at CESR. The method involves shaking one bunch at a specific frequency and observing the resulting oscillations of the corresponding opposing bunch. In initial tests, 1% accurate measurements have been obtained in 1 second. Measurements of different bunches in a train shows bunch to bunch differences with the optimum conditions for one bunch not coinciding with the optimum for another.

The prototype superconducting cavity system for CESR-Phase III was tested in CESR in August 1994. The performance of the system was very gratifying. The cavity operated gradients of 4.5-6 MV/m and accelerated beam currents up to 220 mA. This current is a factor of 3 above the world record 67 mA for SRF[1]. The high circulating beam current did not increase the heat load or present any danger to the cavity. No instability attributable to the SRF cavity was encountered. A maximum of 155 kW of rf power was transferred to a 120 mA beam. The window was subjected to 125 kW reflected power and processed easily. In the travelling wave mode, vacuum bursts and are trips prevented us from going above 165 kW. The maximum HOM power extracted was 2 kW. Beam stability studies were conducted for a variety of bunch configurations. In other tests a 120 mA beam was bumped horizontally and vertically by /spl plusmn/10 mm. While supporting a 100 mA beam, the cavity was axially deformed with the tuner by 0.4 mm to sweep the HOM frequencies across dangerous revolution harmonics. In all such tests, no resonant excitation of HOMs or beam instabilities were observed, which confirms that the potentially dangerous modes were damped strongly enough to be rendered harmless.

Machine performance for the running period is reviewed with an emphasis on phenomena associated with the large number of parasitic crossings peculiar to a single ring collider with multi-bunch beams.

New software has been developed at the Cornell Electron/positron Storage Ring CESR. An object-oriented subroutine library called BMAD has simplified the writing of programs by providing modular subroutines to read in lattice files, calculate Twiss parameters, etc. Built on top of this, the lattice optimization program designs the linear lattice to minimize problems with the pretzel orbit, and uses a novel strategy to quickly design sextupole distributions that maximize the dynamic aperture.

The Long Range Beam-Beam Interaction (LRBBI) is one of major limiting factor to the performance of a pretzel collider machine like CESR in which each bunch has several tens parasitic crossing points along the ring. To investigate the effects due to LRBBI, simulation studies are done with new simulation code in weak-strong and strong-strong scenarios. The precise simulations reveal that LRBBI, in the case of CESR, has significant effects on machine parameters. Especially the bunch-by-bunch differences, which can hardly be compensated by routine adjustments of operation conditions, may affect the luminosity performance directly. In future, with possibly higher current, more bunches or higher current/energy ratio, the dedicated compensation schemes are necessary.

A method is presented for characterizing the emittance dilution and dynamic aperture for an arbitrary closed lattice that includes guide field magnet errors, multipole errors and misalignments. This method, developed and tested at the Cornell Electron Storage Ring Test Accelerator (CesrTA), has been applied to the damping ring lattice for the International Linear Collider (ILC). The effectiveness of beam based emittance tuning is limited by beam position monitor (BPM) measurement errors, number of corrector magnets and their placement, and correction algorithm. The specifications for damping ring magnet alignment, multipole errors, number of BPMs, and precision in BPM measurements are shown to be consistent with the required emittances and dynamic aperture. The methodology is then used to determine the minimum number of position monitors that is required to achieve the emittance targets, and how that minimum depends on the location of the BPMs. Similarly, the maximum tolerable multipole errors are evaluated. Finally, the robustness of each BPM configuration with respect to random failures is explored.

At the Cornell Electron/Positron Storage Ring, a fast luminosity monitor has been implemented. The monitor works by measuring the amplitude of oscillation of selected bunches while the corresponding opposing bunches are shaken. Signal-to-noise ratios of better than 100:1 have been obtained with 1 sec averaging times. A software normalization program ameliorates the unwanted dependence of the signal upon certain vertical lattice parameters such as the vertical tune.

In routine operation the Cornell electron/positron storage ring, CESR, collides 9 trains of 4 or 5 bunches of electrons and positrons. The luminosity of individual bunch pairs can suffer if the transverse positions of those bunches are displaced differentially. This paper will present the results of studies of the effect of bunch-by-bunch or train-by-train variations in the luminosity by measuring (1) the deflection from the beam-beam interaction, (2) the relative positions of the bunches, and (3) the bunch dependent luminosity from the CLEO detector. Comparisons between these three methods are discussed.

We present a detailed design for operation of the Cornell Electron Storage Ring, CESR, in the energy range covering the /spl psi/ resonances and the Charm and Tau thresholds, as well as reaching to the upper Y resonances near 11 GeV. The addition of 18 m of super-ferric wiggler magnets will partially restore low energy beam emittance and damping times. Installation of superconducting quadrupoles in the interaction region and the addition of high performance superconducting RF cavities will enhance performance at all energies. Studies of optics, beam dynamics, wiggler and vacuum system performance, beam stability, and beam-beam effects confirm operation with a luminosity of 3/spl times/ 10/sup 32/ CM/sup -2/ sec/sup -1/ at 1.88 GeV.

The presence of quadrupole errors in a storage ring will lead to errors in the Twiss parameters and/or errors in the horizontal-vertical coupling. This in turn can lead to degradation of machine performance, such as a decrease in the luminosity. At the Cornell Electron/Positron Storage Ring, the measurement of the betatron phase along with the horizontal-vertical coupling has led to the ability to locate the position of any quadrupole errors and to calculate its strength. This is analogous to using orbit data to locate the source of a kick. Once the source of the error is known, steps can be taken to remove it or to nullify its effect.

Measurement of the betatron phase in the vertical and horizontal planes as well as the transverse horizontal-vertical coupling is a standard procedure now used at the Cornell Electron/Positron Storage Ring. The measurement is made by shaking the beam and observing the phase of oscillation at detectors located around the ring. The measurements allow quadrupolar errors to be corrected.

A formalism for describing the coupled two-dimensional motion of high energy particle beams in a storage ring is developed and extended to circumstances where the coupling is very strong, such as for the M\"obius twist accelerator.