Paper | Title | Other Keywords | Page | |||||
---|---|---|---|---|---|---|---|---|
MOZAKI02 | New Developments in Super B Factories | luminosity, collider, emittance, injection | 32 | |||||
|
The design of a super B factory with luminosity in the range of 1036 cm-2 sec-1, based on innovative ideas like the crabbed waist, is being studied by an international collaboration, in close contact with the ILC studies.
|
|
|
Slides
|
|
|
||
MOOAKI01 | Plans for Utilizing the Cornell Electron Storage Ring as a Test Accelerator for ILC Damping Ring Research and Development | emittance, wiggler, electron, instrumentation | 42 | |||||
|
Funding: Funding provided by NSF grant PHY-0202078 |
In April 2008, we propose to begin operation of the Cornell Electron Storage Ring (CESR) as a test accelerator, CesrTA, for International Linear Collider (ILC) damping ring research. Utilizing 12 damping wigglers, the baseline CesrTA lattice at 2.0 GeV will offer a natural geometric emittance of 2.25 nm. An experimental program has been laid out which focuses on several key areas of damping rings R&D. First we will test vacuum chamber designs to suppress electron cloud growth in the wiggler magnets. Secondly, we will develop correction, tuning and emittance monitoring strategies to achieve vertical emittances of a few picometers. As part of this effort we will validate alignment and survey techniques being developed by the Linear Collider Alignment and Survey group (LiCAS) for curved tunnel applications. After achieving ultra-low emittance, we intend to explore the impact of the electron cloud, the fast ion instability and other beam dynamics effects on ultra-low emittance beams. Finally, we plan to test various technical systems required for the ILC damping rings. This paper provides an update on conceptual design issues for CesrTA and describes the experimental program in detail. |
|
Slides
|
|
|
||
MOZBKI01 | CESR-C: A Wiggler-Dominated Collider | wiggler, optics, luminosity, electron | 48 | |||||
|
Funding: Work supported by US National Science Foundation grant PHY-0202078 |
CESR-c operates with twelve 2.1 Tesla wigglers that account for 90% of the synchrotron radiation with beam energy in the range of 1.8 to 2.1 GeV. The wigglers reduce the radiation damping time from 0.5 seconds to 50 milliseconds. The carefully designed wigglers restrict neither physical nor dynamic aperture of the storage ring, though both quadrupole and sextupole distributions must be tailored to compensate the primary optics effects of the wigglers. Colliding beam performance limits are determined by the numerous parasitic beam-beam interactions in the single ring. Several approaches taken to mitigate these limiting effects are described herein. The CESR-c wigglers are an excellent match to the requirements for future damping rings. We describe how with flexible optics, extensive infrastructure, and resource expertise, they form an effective test bed for assessment and solution of damping ring issues such as electron cloud and ion effects, and achieving ultra-low emittance beams. |
|
Slides
|
|
|
||
MOPAN009 | Transverse Feedback Development at SOLEIL | feedback, impedance, emittance, betatron | 161 | |||||
|
With reduced vertical chamber aperture adopted all around the machine, the transverse impedance for the SOLEIL ring is enhanced both in its resistive-wall and broadband content. The predicted instability threshold currents being significantly low as compared to the nominal current in multibunch and in several single bunch modes, a decision was taken to install a digital bunch by bunch feedback system, with an aim to make it operational since the beginning of the storage ring operation. The system implemented comprises components developed elsewhere, particularly the FPGA processor of SPring-8, chosen among different possible solutions. Using a BPM and a stripline in the diagonal mode, a single unit of the FPGA processor board has shown to successfully suppress resistive-wall and ion induced multibunch instabilities in either one or both transverse planes. On top of the system characteristics, the paper discusses details of the obtained performance, as well as future extensions to overcome the encountered limitations.
|
|
|
|||||
MOPAN023 | Superconductive Damping Wigglers for the CLIC Project | wiggler, emittance, radiation, undulator | 200 | |||||
|
The CLIC damping ring requires wigglers with both high on-axis fields and short periods. The present design foresees a superconductive wiggler with a period length of 5 cm, a peak on-axis field of 2.5 T and a full width aperture of 12 mm. In this paper we explore the performance improvements of the damping ring when these parameters are pushed to 2.7 T at a period length of 2 cm with the expense of a reduced aperture of 5 mm. A design for a prototype for testing the field quality of such a wiggler is presented in this paper and the possibility to test this wiggler with beam in the storage ring ANKA is described.
|
|
|
|||||
MOPAN030 | Analysis of Transverse Beam Oscillation at Photon Factory | feedback, betatron, injection, factory | 221 | |||||
|
FPGA based bunch by bunch feedback system to cure the transverse instabilities has been in operation stably since Oct. 2005. Specification and performance of the system will be introduced, transient measurement has been done to analyze the instability modes, which helps to understand the instability sources. Bunch by bunch beam oscillation, together with the digital turn-by-turn beam position measurement, injection oscillation damping is recorded and analyzed, transverse beam oscillation with and without the bunch by bunch feedback system will be shown in this paper. Precise tune measurement during this period will be presented. Turn by turn phase space monitor is also available with the data, from which the nonlinear beam dynamics can be revealed.
|
|
|
|||||
MOPAN055 | Bunch-by-Bunch Measurement and Feedback System of HLS | feedback, controls, injection, emittance | 275 | |||||
|
Funding: Supported by National Natural Science Project (10175063); National Natural Science Key Project (10535040) |
In this paper, HLS (Hefei light Source) bunch-by-bunch measurement and feedback system will be introduced. This system is integrated with longitudinal oscillation measurement system, fast vector control, fiber notch filter and bunch current detection system. The detail of the two fronts will be shown. Some experimental results by this system are also present in this paper, as phase-space tracing, mode dumping rate, and feedback experiments. |
|
|||||
MOPAN056 | Development of Digital Transverse Bunch-by-Bunch Feedback System of HLS | feedback, kicker, single-bunch, pick-up | 278 | |||||
|
Funding: Supported by "National 211 Project" |
To promote the transverse feedback system of HLS, we develop the transverse digital feedback system. The scheme of HLS digital feedback system is presented in this paper, and the primitive digital feedback experiment we have done in HLS is also included in the paper. |
|
|||||
MOPAN061 | Compact Output Filter for Switching Frequency Elimination at the PLC Linac New Magnet Power Supply | linac, power-supply, controls, feedback | 293 | |||||
|
Funding: This work is supported by the Ministry of Science and Technology, Korea. |
At 2006, PLS Linac magnet power supply (MPS) has been upgraded for the stable beam injection and 4th generation light source research. New MPS are developed new compact MPS of 16-bit resolution and 20ppm stability using four-quadrant switching scheme with 50kHz MOSFET switching device, and consists of main power board, control power board, regulator board and CPU board. Size of each board is only 100mm width and 240mm depth. Output of MPS is 10V, ±10A for the bipolar and 50V, 50A for the unipolar magnet. Main board is consisted four-quadrant FET switch, driver and output filter. Output filter must be perfectly eliminating switch frequency and compact size. In this paper, we report on development and characteristics of compact output filter of the new MPS for PAL linac. |
|
|||||
MOPAN075 | Experimental Modal Analysis of Components of the LHC Experiments | acceleration, monitoring, resonance, coupling | 329 | |||||
|
Experimental modal analysis of components of the LHC Experiments is performed with the purpose of determining their fundamental frequencies, their damping and the mode shapes of light and fragile detectors components. This process permits to confirm or replace Finite Element analysis in the case of complex structure (with cables and substructure coupling). It helps solving structural mechanics problems to improve the operational stability and determine the acceleration specifications for transport operations. This paper describes the hardware and software equipments used to perform a modal analysis on particular structures such as a particle detectors and the method of curve fitting to extract the results of the measurements. This paper exposes also the main results obtained for the LHC Experiments.
|
|
|
|||||
MOPAN094 | Operation Experiences of the Bunch-by-Bunch Feedback System for TLS | feedback, kicker, injection, controls | 383 | |||||
|
Severe multi-bunch instabilities are bothered the operation of Taiwan Light Source (TLS) during the operation during 2004 just after SRF system upgrade. FPGA-based bunch-by-bunch feedback system was commissioning during late 2005 and early 2006. Multi-bunch instability in both transverse plans and longitudinal are well control. Delivery up to 400 mA stored beam was demonstrated. Transverse feedback system make low chromaticity operation is possible; this is very helpful to improve injection efficiency which are essential for routine top-up operation. Operation experiences of the bunch-by-bunch feedback system will be summary in this report.
|
|
|
|||||
MOPAN109 | Turnaround Feed-Forward Correction at the ILC | kicker, extraction, septum, linear-collider | 419 | |||||
|
Funding: The Commission of European Communities under 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899, and by the UK Particle Physics & Astronomy Research Council. |
The RTML turnaround feed-forward correction scheme, as proposed in the ILC Baseline Configuration Document, is considered. Instabilities in the challenging Damping Ring extraction kicker system may give rise to betatron bunch-by-bunch jitter and position drift across the bunch train. A system is outlined in which the bunch trajectory is measured with an upstream pair of BPMs and corrected with a pair of downstream fast kickers. The beam turnaround time allows signal processing and calculation of the correction. A feed-forward algorithm is formulated and expressions are derived for the main system parameters and procedures: dynamic range, maximal kicker voltage, gain compression error, BPM resolution, system zero offset stability, BPM-to-kicker matrix measurement, feed-forward gain adjustment. This analysis will enable further consideration of system tolerances, and provides a basis for an engineering design. |
|
|||||
MOPAN116 | An FPGA-Based Bunch-to-Bunch Feedback System at the Advanced Photon Source | feedback, kicker, storage-ring, simulation | 440 | |||||
|
Funding: Work supported by U. S. Department of Energy, Office of Basic Energy Sciences, under Contract No. W-31-109-ENG-38. |
The Advanced Photon Source storage ring has several bunch fill patterns for user operation. The hybrids fill pattern consists of a single bunch with a charge of 16 mA and a bunch train of 56 bunches. Both horizontal and vertical instabilities are observed. Currently chromaticity correction is the only method available to overcome the instability. Beamlife time and injection efficiency suffer because of high sextupole currents. A bunch-to-bunch feedback system is designed to overcome beam instability and reduce the required chromaticity correction. The feedback system is based on an FPGA DSP processor. The signal filtering algorithm is based on the time-domain-least-square method developed at SPring-8. We have just completed the integration of the system. We report the system design and some test results. |
|
|||||
MOPAS025 | Conceptual Design of ILC Damping Ring Wiggler Straight Vacuum System | wiggler, photon, quadrupole, vacuum | 488 | |||||
|
Funding: U. S. Department of Energy, Contract No. DE-AC02-05CH11231. |
The positron and electron damping rings for the ILC (International Linear Collider) will contain long straight sections consisting of twenty wiggler/quadrupole pairs. The wigglers will be based upon the CESR-C superconducting design* . There are a number of challenges associated with the design of the wiggler straight vacuum system, in particular, the absorption of photon power generated by the wigglers. This paper will present the overall conceptual design of the wiggler straight vacuum system developed for the ILC RDR. Particular emphasis will be placed on photon power load calculations and the absorber design.
* A. Mihailichenko, Optimized Wiggler Magnet for CESR, Proceedings of PAC2001, Chicago, Il, June 18-22, 2001 |
|
|||||
MOPAS050 | Active Damping of the e-p Instability at the LANL PSR | feedback, electron, linac, proton | 548 | |||||
|
Funding: This work was supported by the United States Department of Energy under contracts DE-AC52-06NA25396 and W-7405-ENG-36. |
A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos National Laboratory Proton Storage Ring (PSR). This system was able to improve the instability threshold by approximately 30% (as measured by the change in RF buncher voltage at instability threshold). Evidence obtained from these tests suggests that further improvement in performance is limited by beam leakage into the gap at lower RF buncher voltage and the onset of instability in the horizontal plane, which had no feedback. Here we describe the present system configuration, system optimization, results of several recent experimental tests, and results from studies of factors limiting its performance. |
|
|||||
MOPAS062 | Analysis of the Longitudinal Low-order Mode Beam Dynamics in PEP-II Rings at High Current Beams | klystron, simulation, feedback, impedance | 575 | |||||
|
Funding: Work supported by Department of Energy (USA) under contract # DE-AC02-76SF00515 |
PEP-II operations will increase the beam currents to 4A for LER and 2.2A for HER to achieve the final goal in luminosity. These magnitudes are challenging in part because they will push toward the limit the longitudinal low-order mode (LOM) beam stability due to beam loading. To analyze the behavior of both rings at high currents and understand the limits in the longitudinal feedback systems a simulation tool has been developed at SLAC. This tool is based on a reduced model of the longitudinal LOM dynamics of the beam interacting with the effective impedance presented by RF station. Simulations and measurements of the longitudinal beam behavior in both rings have been performed to understand the ultimate limit of the system. These studies have defined the impact of control loop parameters in the longitudinal beam dynamics, identified the poor performance of RF devices affecting the optimal performance of the RF stations and quantified the behavior of the longitudinal LOM beam dynamics. Results of sensitivity to parameter variations in the beam dynamics and limits in the maximum current that LER/HER can achieve based on the longitudinal beam stability are reported in this paper. |
|
|||||
MOPAS067 | Control and Measurements of Longitudinal Coupled-bunch Instabilities in the ATF Damping Ring | feedback, single-bunch, injection, extraction | 584 | |||||
|
Funding: Work supported by U. S. Department of Energy contract DE-AC02-76SF00515 and by the US-Japan collaboration in High Energy Physics |
Damping ring at the Accelerator Test Facility (ATF) is a storage ring with 714 MHz RF frequency and harmonic number of 330. The ring is used in both single and multibunch regimes. In both cases significant longitudinal dipole motion has been observed in the ring. A prototype longitudinal feedback channel using a Gproto baseband processing channel and a set of horizontal striplines has been constructed for the machine. The prototype allowed both suppression of the longitudinal motion and studies of the motion sources. In this paper we present the results of these studies including measurements of steady-state oscillation amplitudes, eigenmodal patterns, and growth and damping rates. Using measured growth rates we estimate the driving impedances. We also present the effect of the longitudinal stabilization on the energy spread of the extracted beam as documented by a screen monitor. |
|
|||||
MOPAS080 | A Digital Ring Transverse Feedback Low-Level RF Control System | feedback, pick-up, controls, simulation | 617 | |||||
|
A digital wide-band system for damping ring instabilities in an accelerator is presented. With increased beam intensity, the losses of an accumulator ring tend to increase due to the onset of various instabilities in the beam. An analog feedback damper system has been implemented at Los Alamos National Laboratory. This analog system, while functional, has certain limitations and a lack of programmability, which can be overcome by a digital solution. A digital feedback damper system is being designed through a collaborative effort by researchers at Oakridge National Laboratory, Los Alamos National Laboratory, and the University of Wisconsin. This system, which includes analog-to-digital converters, field programmable gate arrays and digital-to-analog converters can equalize errors inherent to analog systems, such as dispersion due to amplifiers/cables, gain mismatches, and timing adjustments. The digital system features programmable gains and delays, and programmable equalizers that are implemented using digital FIR and comb filters. The flexibility of the digital system allows it to be customized to implement different configurations and extended to address other diagnostic problems.
|
|
|
|||||
MOPAS104 | Large Scale Distributed Parameter Model of Main Magnet System and Frequency Decomposition Analysis | coupling, dipole, simulation, power-supply | 670 | |||||
|
Funding: Work performed under auspices of U. S. Department of Energy. |
Large accelerator main magnet system consists of hundreds, even thousands, of dipole magnets. They are linked together under selected configurations to provide highly uniform dipole fields when powered. Distributed capacitance, insulation resistance, coil resistance, magnet inductance, and coupling inductance of upper and lower pancakes make each magnet a complex network. When all dipole magnets are chained together in a circle, they become a coupled pair of very high order complex ladder networks. In this study, a network of more than thousand inductive, capacitive or resistive elements are used to model an actual system. The circuit is a large scale network. Its equivalent polynomial form has several hundred degrees. Analysis of this high order circuit and simulation of the response of any or all components is often computationally infeasible. We present methods to use frequency decomposition approach to effectively simulate and analyze magnet configuration and power supply topologies. |
|
|||||
TUZAAB01 | Equilibrium Beam Distribution in Electron Storage Rings near Synchrobetatron Coupling Resonances | resonance, coupling, emittance, scattering | 789 | |||||
|
Linear dynamics in a storage ring can be described by the one-turn map matrix. In the case of a resonance where two of the eigenvalues of this matrix are degenerate, a coupling perturbation causes a mixing of the uncoupled eigenvectors. A perturbation formalism is developed to find eigenvalues and eigenvectors of the one-turn map near such a linear resonance. Damping and diffusion due to synchrotron radiation can be obtained by integrating their effects over one turn, and the coupled eigenvectors can be used to find the coupled damping and diffusion coefficients. Expressions for the coupled equilibrium emittances and beam distribution moments are then derived. In addition to the conventional instabilities at the sum, integer, and half-integer resonances, it is found that the coupling can cause an instability through antidamping near a sum resonance even when the symplectic dynamics are stable. E. G., the case of linear synchrobetatron coupling is analyzed where the coupling is caused by dispersion in the rf cavity, or by a crab cavity. Explicit closed-form expressions for the sum/difference resonances are given along with the integer/half-integer resonances.
|
|
|
Slides
|
|
|
||
TUODAB01 | Variations of Betatron Tune Spectrum due to Electron Cloud Observed in KEKB | electron, impedance, focusing, positron | 825 | |||||
|
In order to investigate the characteristics of electron clouds, the wake effects were measured at KEKB using a test bunch placed behind a bunch-train, where there was a rapid decay in the electron cloud density. The current-dependent tune-shift of the test bunch exhibited nonlinear behaviour in the vertical plane [1]. By observing the tune spectrum, we found that the spectrum width expanded and this was accompanied with a large negative tune slope at a low cloud density and at a low bunch current. However, as the cloud density increased, the spectrum width shrunk and this was accompanied with a positive tune slope. These experimental results suggested that a high electron cloud density caused an anti-damping effect in the tune spectrum. We believe that the variations in the tune slope and spectrum width might be related to the wake field in the resonator model, where the wavelength is comparable to the bunch length.
|
[1] T. Ieiri et al., Proc. of EPAC06, Edinburgh, Scotland, 2101 (2006). |
|
Slides
|
|
|
||
TUOAC01 | Design and Measurements of a Damping Ring Kicker for the ILC | kicker, impedance, pulsed-power, optics | 846 | |||||
|
Funding: Work supported by a contribution from the National Research Council of Canada. |
The International Linear Collider (ILC) requires ultra fast kickers for the damping ring. One option requires kickers which must produce pulses of 5 kV magnitude, with 6 ns rise and 6 ns fall time into a 50 Ohm, terminated, matched stripline deflector. The pulse must rise and fall within 12 ns. The pulse magnitude must be repeatable to a high accuracy. This paper describes a novel design for a suitable pulse generator for the damping ring kicker, in which 2 stacks of 1kV FETS are combined to generate the fast pulses. The design concept uses 2 parallel 100 Ω drivers combined to provide a 50 Ω driver. The need for 3 MHz burst mode operation for 1 ms at 5 Hz (or 10 Hz) gives an average rep rate of 15 kHz (or 30 kHz). Measurements and calculations are presented on the present state of the TRIUMF prototype pulse generator. |
|
Slides
|
|
|
||
TUOBC02 | A New Type High Voltage Fast Rise/Fall Time Solid State Marx Pulse Modulator | controls, induction, power-supply, electron | 865 | |||||
|
A new type of solid state Marx modulator developed by Stangenes Industries has the capability of producing high voltage pulses with fast rise and fall time at high repetition rates. In addition it has the ability to produce dynamically flexible output amplitude and pulse width. The pulse modulator was developed for the Fermi Labs Tevatron Electron Lens Tune Compensation System. It can produce a 14kV pulse with 200 nanosecond rise time and 600 nanosecond full pulse width at a 25 kilohertz repetition rate. It has no overshot or reverse voltage, making it ideal for beam bunch manipulation. It is designed to operate into a 200 pfd, 800 Ω load. This design permits all of the sources of power including the 1kV charging power supply to be connected at the grounded end of the pulser. A second generation pulser is under development to operate at above 50 kHz repetition rate with an arbitrary voltage waveform and faster rise/fall time. The pulser can accommodate load arcing and incorporates built in redundancy to insure high availability. The paper delineates the unique design of the modulator and its performance.
|
|
|
Slides
|
|
|
||
TUZBC01 | Towards Simulation of Electromagnetics and Beam Physics at the Petascale | simulation, gun, dipole, coupling | 889 | |||||
|
Funding: Work supported by DOE contract DE-AC02-76SF00515. |
Under the support of the U. S. DOE SciDAC program, SLAC has been developing a suite of 3D parallel finite-element codes aimed at high-accuracy, high-fidelity electromagnetic and beam physics simulations for the design and optimization of next-generation particle accelerators. Running on the latest supercomputers, these codes have made great strides in advancing the state of the art in applied math and computer science at the petascale that enable the integrated modeling of electromagnetics, self-consistent Particle-In-Cell (PIC) particle dynamics as well as thermal, mechanical, and multi-physics effects. This paper will present 3D results of trapped mode calculations in an ILC cryomodule and the modeling of the ILC Sheet Beam klystron, shape determination of superconducting RF (SCRF) cavities and multipacting studies of SCRF HOM couplers, as well as 2D and preliminary 3D PIC simulation results of the LCLS RF gun. |
|
Slides
|
|
|
||
TUPMN046 | Quadrupole HOM Damping with Eccentric-fluted Beam Pipes | quadrupole, dipole, linac, ion | 1022 | |||||
|
HOM damping is important for superconducting cavities, especially for high current CW machines such as ERLs. The lower Q-values of HOMs lead to the lower requirement of a refrigerator system and the higher beam current against HOM BBU. Enlarged beam pipes, which have lower cutoff frequencies, are effective to damp HOMs of monopole and dipole, but insufficient for HOMs of quadrupole which have high cutoff frequencies. An eccentric-flute is proposed to damp the HOMs of quadrupole. The eccentric-flute is formed by displacing the flute from the center of the beam pipe and/or by jackknifing around the midpoint of the flute to couple two degenerate modes. The eccentric-flute acts as a mode converter from quadrupole to dipole of the lower cutoff frequency so that the RF power can propagate through the beam pipe. The result of calculation with MAFIA and measurement of a cold model with the eccentric-flute are presented.
|
|
|
|||||
TUPMN058 | The Operation Status of HLS (Hefei Light Source) | radiation, synchrotron, synchrotron-radiation, feedback | 1058 | |||||
|
National Synchrotron Radiation Lab, University of Science and Technology of China, P. R.China HLS(Hefei Light Source) is a dedicated synchrotron radiation research facility, spectrally strongest in Vacuum Ultra Violet and Soft X-ray. Designed and constructed in 1980's, accepted to regular service in 1991. From 1999 to 2004, the National Synchrotron Radiation Lab carried out its Phase II Project, in which quite a few sub-systems of HLS storage ring were upgraded and 8 new beamline were constructed. After the project, the performance of HLS is improved considerably. In this paper, the operation status and performance of storage ring in recent years were presented. With some measures, the operation beam intensity is about 300mA, beam lifetime is higher than before, orbit stability is met requirement of users, and the capability to provide synchrotron radiation exceeds the design value.
|
|
|
|||||
TUPMN059 | The Nonlinear Effects of Fringe Fields in HLS | dipole, quadrupole, storage-ring, sextupole | 1061 | |||||
|
As a small low energy electron storage ring, the fringe field effects on linear and nonlinear properties maybe can not be ignored. In this paper, the fringe field of dipole magnets and quadrupole magnets on linear optics parameters and nonlinear driving terms of general purpose operation mode in HLS storage ring were analyzed and calculated. The results showed that, for GPLS mode, the fringe field of dipole and quadrupole is the main source of tune shift with amplitude. The fringe field of dipole contributes non-ignorable part to vertical chromaticity. Similar behavour is also displayed in non linear driving terms.
|
|
|
|||||
TUPMN090 | Evaluation of the Possibility of Using Damping Wigglers in the Advanced Photon Source | wiggler, emittance, lattice, storage-ring | 1124 | |||||
|
Funding: Work supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
The Advanced Photon Source (APS) is a 7-GeV storage ring light source that has been in operation for over a decade. Over time, the performance of the APS has been increased by reduction of the emittance from 8 nm to 3.1 nm and by the use of top-up mode. We continue to explore options for improving the performance further. This paper discusses the possible improvements in emittance that could result from the use of damping wigglers. We also discuss rf and space requirements. |
|
|||||
TUPMN091 | Planned Use of Pulsed Crab Cavities for Short X-ray Pulse Generation at the Advanced Photon Source | impedance, storage-ring, photon, single-bunch | 1127 | |||||
|
Funding: Work supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
In recent years, we have explored application to the Advanced Photon Source (APS) of Zholents'* crab-cavity-based scheme for production of short x-ray pulses. Work concentrated on using superconducting (SC) cavities in order to have a continuous stream of crabbed bunches and flexibility of operating modes. The challenges of the SC approach are related to the size, cost, and development time of the cavities and associated systems. A good case can be made for a pulsed system** using room-temperature cavities. APS has elected to pursue such a system in the near term, with the SC-based system planned for a later date. This paper describes the motivation for the pulsed system and gives an overview of the planned implementation and issues. Among these are overall configuration options and constraints, cavity design options, frequency choice, cavity design challenges, tolerances, instability issues, and diagnostics plans.
*A. Zholents et al., NIM A 425, 385 (1999).**P. Anfinrud, private communication. |
|
|||||
TUPMN093 | A Kilohertz Picosecond X-Ray Pulse Generation Scheme | synchrotron, kicker, storage-ring, photon | 1133 | |||||
|
The duration of the x-ray pulse generated at a synchrotron light source is typically tens of picoseconds. Shorter pulses are highly desired by the users. In electron storage rings, the vertical beam size is usually orders of magnitude less than the bunch length due to radiation damping; therefore, a shorter pulse can be obtained by slitting the vertically tilted bunch. Zholents proposed tilting the bunch using rf deflection. We found that tilted bunches can also be generated by a dipole magnet kick. A vertical tilt is developed after the kick in the presence of non-zero chromaticity. The tilt was successfully observed and a 4.2-ps pulse was obtained fom a 27-ps electron bunch at the Advanced Photon Source. Based on this principle we propose a short-pulse generation scheme that produces picosecond x-ray pulses at a repetition rate of 1~2 kHz, which can be used for pump-probe experiments. The tilt phenomenon can also be utilized for machine parameter measurement.
|
|
|
|||||
TUPMN108 | Particle-in-Cell Calculations of the Electron Cloud in the ILC Positron Damping Ring Wigglers | electron, wiggler, positron, simulation | 1164 | |||||
|
Funding: This work was supported by the Office of High Energy Physics of the U. S. Department of Energy under contract number No. DE-AC02-05CH11231. |
Due to copious synchrotron radiation from the beam, electron cloud effects are predicted to be important in the wiggler sections of the ILC positron damping ring. In this area of the ring, the physics is inherently 3D. Moreover, a self-consistent calculation of the physics of the electron cloud/beam system is necessary for examining such phenomena as emittance growth in the beam. We present the first calculations of this system with the self-consistent 3D particle-in-cell code WARP/POSINST. The code includes self-consistent space charge for both species, mesh refinement, and detailed models of primary and secondary electron production. Interaction with electrons is assumed to occur only in the wigglers in this model the beam is moved using maps between wiggler sections. |
|
|||||
TUPMS073 | Dispersion Tolerance Calculation for NSLS-II | emittance, insertion, insertion-device, wiggler | 1341 | |||||
|
The approach for the proposed National Synchrotron Light Source II to reach small transverse emittances is to deploy damping wigglers. In the ideal lattice the dispersion is zero in the straight sections, therefore the damping wigglers supply only damping effect. In reality the residual dispersion can be generated by the lattice errors, trim dipoles, and the insertion devices. We will discuss dispersion introduced by different sources and calculate the tolerances. Possible correction schemes will also be presented.
|
|
|
|||||
TUPMS074 | Collective Effects in the NSLS-II Storage Ring | emittance, impedance, storage-ring, single-bunch | 1344 | |||||
|
Funding: This work was supported by Department of Energy contract DE-AC02-98CH10886. |
A new high-brightness synchrotron light source (NSLS-II) is under design at BNL. The 3-GeV NSLS-II storage ring has a double-bend achromatic lattice with damping wigglers installed in zero-dispersion straights to reduce the emittance below 1nm. In this note, we present an overview of the impact of collective effects upon the performance of the storage ring. Subjects discussed include Touschek lifetime, intra-beam scattering, instability thresholds due to ring impedance, and use of a third-harmonic Landau cavity. |
|
|||||
TUPMS078 | IBS Effects in a Wiggler Dominated Light Source | emittance, radiation, lattice, coupling | 1353 | |||||
|
Intra-beam scattering (IBS) is often thought of as a fundamental limitation to achieving lower emittance and hence higher brightness in modern storage ring light sources. However, as we show in this paper analytically and by simulations using SAD code, this limitation may no longer be relevant in a wiggler dominated 3rd generation light source. Instead, lowering the emittance by increasing the amount of wiggler radiation does not result in significant IBS induced emittance blow-up, as higher beam density (and IBS rates) is compensated by faster radiation damping. We show that under some practical assumptions the relative ratio of the emittance including the IBS effect to the emittance at zero current is emittance independent.
|
|
|
|||||
TUPAN085 | LHC Impedance Reduction by Nonlinear Collimation | impedance, collimation, insertion, betatron | 1571 | |||||
|
A nonlinear collimation system can allow larger aperture for the mechanical jaws, and it thereby can help to reduce the collimator impedance, which presently limits the LHC beam intensity. Assuming the nominal LHC beam at 7 TeV, we show how a nonlinear betatronic collimation insertion would reduce considerably the LHC coherent tune shift for the most critical coupled-bunch mode as compared with the conventional baseline linear collimation system of Phase-I. In either case, the tune shifts of the most unstable modes are compared with the stability diagrams for Landau damping.
|
|
|
|||||
TUPAS067 | Electron Cloud in the Wigglers of The Positron Damping Ring of the International Linear Collider | electron, wiggler, dipole, simulation | 1808 | |||||
|
Funding: Work supported by the U. S. Department of Energy under contract DE-AC02-76SF00515 |
The ILC positron damping ring comprises hundreds of meters of wiggler sections, where many more photons than in the arcs are emitted, and with the smallest beam-pipe aperture of the ring. A significant electron-cloud density can therefore be accumulated via photo-emission and via beam-induced multipacting. In field-free regions the electron-cloud build up may be suppressed by adding weak solenoid fields, but the electron cloud remaining in the wigglers as well as in the arc dipole magnets can still drive single-bunch and multi-bunch beam instabilities. This paper studies the electron-cloud formation in an ILC wiggler section for various scenarios, as well as its character, and possible mitigation schemes. |
|
|||||
TUPAS089 | Small Angle Crab Compensation for LHC IR Upgrade | emittance, coupling, luminosity, simulation | 1853 | |||||
|
Funding: This work is partially supported by the U. S. DOE |
A small angle (< 1mrad) crab scheme is an attractive option for the LHC luminosity upgrade to recover the geometric luminosity loss from the finite crossing angle, which steeply increases to unacceptable levels as the IP beta function is reduced below its nominal value. The crab compensation in the LHC can be accomplished using only two sets of deflecting rf cavities, placed in collision-free straight sections of LHC to nullify the crossing angles at IP1 & IP5. We present IR optics configurations with low-angle crab crossing, study the beam-beam performance and proton-beam emittance growth in the presence of crab compensation, lattice errors, crab RF noise sources. We also explore a 400MHz superconducting cavity design and discuss the pertinent RF challenges. |
|
|||||
TUPAS094 | Transverse Beam Transfer Functions of Colliding Beams in RHIC | simulation, proton, coupling, luminosity | 1856 | |||||
|
Funding: Work supported by U. S. DOE under contract No DE-AC02-98CH1-886. |
We use transverse beam transfer functions to measure tune distributions of colliding beams in RHIC. The tune has a distribution due to the beam-beam interaction, nonlinear magnetic fields particularly in the interaction region magnets, and non-zero chromaticity in conjunction with momentum spread. The measured tune distributions are compared with calculations. |
|
|||||
WEOAKI01 | Optical Stochastic Cooling Proof-of-Principle Experiment | electron, radiation, undulator, scattering | 1904 | |||||
|
Cooling of charged particle beams plays a key role in achieving peak luminosity in high-energy colliders. The presently undemonstrated technique of optical stochastic cooling (OSC)* holds promise for fast cooling of high energy protons and heavy ions. A proof-of-principle experiment with electrons is proposed at relatively modest cost using the MIT-Bates South Hall Ring, which is well suited for such a test due to its energy range, layout, and RF system, as well as its present availability. An overview of the experiment will be presented. The design of key systems for the achievement of OSC will be disucussed along with beam requirements and cooling projections.
|
*M. Zolotorev and A. Zholents, Phys Rev. E 50 (1994) 3087. |
|
Slides
|
|
|
||
WEXAB02 | Critical R&D Issues for the ILC Damping Rings and New Test Facilities | emittance, electron, wiggler, kicker | 1945 | |||||
|
The damping rings for the International Linear Collider will be required to accept large beams from the electron and positron sources, and produce highly stable, very low emittance beams for tuning and operation of downstream systems. While many of the parameters for the damping rings are within range of storage rings presently operating, beams meeting the full quality and stability specifications have not been demonstrated. In addition, the requirements for some of the subsystems (for example, the injection and extraction kickers) push the limits of available technology. We discuss the principal goals and challenges of the damping rings research and development program, and the role that could be played by some proposed future damping rings test facilities.
|
|
|
Slides
|
|
|
||
WEXAB03 | ATF Results and ATF-II Plans | extraction, emittance, kicker, laser | 1950 | |||||
|
The ATF (Accelerator Test Facility at KEK) International collaboration has been launched formally under the MoU (Memorandum of Understanding) from August 1, 2005, so as to maximally contribute to the world design and development efforts in the areas of particle sources, damping rings, beam focusing and beam instrumentation towards the International Linear Collider (ILC) project. I will give a talk on the recent ATF results and future plans of ATF2 project. I am sure that ATF International collaboration group will give a right direction regarding the development of fast kicker for ILC damping ring and clear experimental results on fast ion instability with very flat beam. Several considerations for ATF-II beam commissioning strategy will be discussed with the explanation of the beam instrumentation.
|
|
|
Slides
|
|
|
||
WEOAAB02 | The Optimized Bunch Compressor for the International Linear Collider | wiggler, linac, emittance, linear-collider | 1958 | |||||
|
The International Linear Collider (ILC) utilizes a two stage Bunch Compressor (BC) that compresses the RMS bunch length from 9 mm to 200 to 300 micrometers before sending the electron beam to the Main Linac. This paper reports on the new design of the optimized BC wiggler. It was reduced in length by more than 30 %. The introduction of nonzero dispersion slope in the BC wigglers enabled them to generate the required compression while having a small SR emittance growth, a tunability range of over a factor of 2 in each wiggler, and less than 3 % RMS energy spread throughout the entire system.
|
|
|
Slides
|
|
|
||
WEXC01 | Experimental Tests of a Prototype System for Active Damping of the E-P Instability at the LANL PSR | feedback, proton, electron, pick-up | 1991 | |||||
|
Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U. S. Department of Energy under contract DE-AC05-00OR22725. |
A prototype of an analog, transverse (vertical) feedback system for active damping of the two-stream (e-p) instability has been developed and successfully tested at the Los Alamos Proton Storage Ring (PSR). This talk describes the system configuration, results of several experimental tests and studies of system optimization along with studies of the factors limiting its performance. |
|
Slides
|
|
|
||
WEYC01 | Instabilities of Cooled Antiproton Beam in Recycler | antiproton, coupling, electron, resonance | 2009 | |||||
|
Funding: Work supported by the US DoE under contract DE-AC02-07CH11359 |
The more beam is cooled, the less stable it is. In the Recycler Ring, antiprotons are cooled both with stochastic and electron cooling. To stabilize it against the resistive wall instability, a digital damper is successfully used. Digital dampers can be described as linear operators with explicit time dependence, and that makes a principle difference with analogous dampers. Theoretical description of the digital dampers is presented. Electron cooling makes possible a two-beam instability of the cooled beam with the electron beam. Special features of this instability are described, and the remedy is discussed. |
|
Slides
|
|
|
||
WEPMN009 | Vibration Stability Studies of a Superconducting Accelerating Module Quadrupole Operating at 4.5K | quadrupole, cryogenics, vacuum, linac | 2065 | |||||
|
Funding: Work supported by the Commission of the European Communities under the 6th Framework Program Structuring the European Research Area, contract number RIDS-011899. |
The European X-ray Free Electron Laser (XFEL) and the International Linear Collider (ILC) superconducting accelerating modules, containing a string of Niobium (Nb) cavities and a quadrupole, will operate at 2K. In this paper, we will report on the vibration stability studies of a high gradient XFEL/ILC type III superconducting accelerating module quadrupole operating at 4.5K. Measurements are performed via geophones affixed on the cold mass in both horizontal and vertical directions. This data will be compared with piezoelectric accelerometers for the same module. The goal is to study the stability of the cold quadrupole and to compare the results with room temperature conditions. |
|
|||||
WEPMN026 | Test Operation of Ball-Screw-Type Tuner for Low-Loss High-Gradient Superconducting Cavity in a Cryomodule | resonance, controls, linac, linear-collider | 2104 | |||||
|
We are constructing a Superconducting RF Test Facility (STF) at KEK as an R&D for ILC accelerator. In STF, four Low-Loss (LL) type 9-cell cavities will be installed into a cryomodule. We are developing ball-screw-type tuner for these cavities aiming at the accelerating gradient of 45 MV/m. At the end of 2006, we installed one LL 9-cell cavity dressed with the ball-screw tuner into the cryomodule. It will be operated without beam in 2007. This paper describes the results of the first operation of the ball-screw tuner for LL 9-cell cavity in the cryomodule of STF.
|
|
|
|||||
WEPMN055 | PEFP HOM Coupler Design | linac, simulation, controls, coupling | 2161 | |||||
|
Funding: This work was supported by the 21C Frontier R&D program of Korea Ministry of Science and Technology. |
A new type of coaxial higher-order mode (HOM) coupler with one hook and two stubs has been designed for PEFP SRF cavities to satisfy the HOM damping requirements of the superconducting RF (SRF) linac of the Proton Engineering Frontier Project (PEFP), and to overcome the notch frequency shift and feed-through tip melting issues. This paper has presents details on the PEFP HOM coupler?s structure, structure optimization, filter characteristics, electro-magnetic field distribution and a coupler installation tool. |
|
|||||
WEPMN068 | Design of the Modulator for the CTF3 Tail Clipper Kicker | kicker, impedance, beam-losses, cathode | 2185 | |||||
|
The goal of the present CLIC test facility (CTF3) is to demonstrate the technical feasibility of specific key issues in the CLIC scheme. The extracted beam from the combiner ring (CR), of 35 A in magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX) facility. A Tail Clipper (TC) is required, in the CR to CLEX transfer line, to allow the duration of the extracted beam pulse to be adjusted. It is proposed to use a stripline kicker for the tail clipper, with each of the deflector plates driven to equal but opposite potential. The tail clipper kick must have a fast rise-time, of not more than 5 ns, in order to minimize uncontrolled beam loss and operate at a rate of up to 50 Hz. Several different options are being investigated to meet the demanding specifications for the modulator of the tail clipper. This paper discusses options considered for the fast, high voltage, semiconductor switches and shows results of initial tests on the switches.
|
|
|
|||||
WEPMN070 | High Power Test of an X-band Slotted-Iris Accelerator Structure at NLCTA | vacuum, controls, linac, higher-order-mode | 2191 | |||||
|
The CLIC study group at CERN has built two X-band HDS (Hybrid Damped Structure) accelerating structures for high-power testing in NLCTA at SLAC. These accelerating structures are novel with respect to their rf-design and their fabrication technique. The eleven-cell constant impedance structures, one made out of copper and one out of molybdenum, are assembled from clamped high-speed milled quadrants. They feature the same heavy higher-order-mode damping as nominal CLIC structures achieved by slotted irises and radial damping waveguides for each cell. The X-band accelerators are exactly scaled versions of structures tested at 30 GHz in the CLIC test facility, CTF3. The results of the X-band tests are presented and compared to those at 30 GHz to determine frequency scaling, and are compared to the extensive copper data from the NLC structure development program to determine material dependence and make a basic validation of the HDS design.
|
|
|
|||||
WEPMN071 | High RF Power Production for CLIC | impedance, linac, extraction, simulation | 2194 | |||||
|
The CLIC Power Extraction and Transfer Structure (PETS) is a passive microwave device in which bunches of the drive beam interact with the impedance of the periodically loaded waveguide and excite preferentially the synchronous mode. The RF power produced (several hundred MW) is collected at the downstream end of the structure by means of the Power Extractor and delivered to the main linac structure. The PETS geometry is a result of multiple compromises between beam stability and main linac RF power needs. Another requirement is to provide local RF power termination in case of accelerating structure failure (ON/OFF capability). Surface electric and magnetic fields, power extraction method, HOM damping, ON/OFF capability and fabrication technology were all evaluated to provide a reliable design.
|
|
|
|||||
WEPMN098 | New HOM Coupler Design for 3.9 GHz Superconducting Cavities at FNAL | coupling, resonance, simulation, dipole | 2259 | |||||
|
Last few years Fermilab is developing the superconducting third harmonic section for the FLASH (TTF/DESY) upgrade. The results of vertical tests of 9-cell Nb cavities didn't reached the designed accelerating gradient. The main gradient limitation is multipacting in HOM coupler. In this paper we present the results of vertical tests accompanied with 3D Analyst simulations of multipacting. Also we discuss the RF design of a new HOM couplers. The goal of a new design is to eliminate multipacting and to increase the frequency of second resonance of the HOM. Increasing the frequency will decrease the electric and magnetic fields having the goal to decrease the thermal load on antenna.
|
|
|
|||||
WEPMN120 | Photonic Band Gap Higher Order Mode Coupler for the International Linear Collider | simulation, lattice, higher-order-mode, collider | 2319 | |||||
|
Funding: Research supported by US Department of Energy, Office of High-Energy Physics, Grant No. DE-FG02-95ER40919 and Air Force Office of Scientific Research, Grant No. FA9550-06-1-0269. |
A photonic band gap (PBG) higher-order-mode (HOM) coupler is proposed as an Alternative Configuration Design (ACD) for the HOM coupler for the International Linear Collider (ILC). The PBG HOM coupler uses a two-dimensional triangular PBG structure with good axial symmetry. Simulation studies of a PBG HOM coupler show that it maintains the operating mode at 1.3 GHz with . While a PBG HOM coupler provides superior damping for all the higher order modes in principle, detailed studies of the effectiveness of HOM damping are being carried out, and results will be discussed. |
|
|||||
WEPMS037 | RF Distribution Optimization in the Main Linacs of the ILC | linac, controls, coupling, linear-collider | 2424 | |||||
|
Funding: Work supported by the U. S. Department of Energy under contract DE-AC02-76SF00515. |
The nominal design gradient for the ILC is 31.5 MV/m, but the L-band superconducting cavities built to date have demonstrated a range in sustainable gradient extending below this goal, limited by Q-dropoff and quenching. An economically feasible cavity acceptance rate will include in the linacs a certain percentage of sub-performing cavities. We examine how, with a customizable RF distribution scheme, one can most efficiently distribute power from one klystron amongst 24 nine-cell cavities. The nominal cavity fills to the design gradient at the time the beam arrives, after which the beamloading voltage exactly cancels any further rise, yielding constant gradient during the bunch train. Along with adjustable RF power, we assume adjustable cavity coupling, or loaded quality factor, so that the gradient can be leveled in non-nominal cavities, to avoid quench-inducing overshoots. We explore these and related issues for the ILC linac high-power RF. |
|
|||||
WEPMS038 | RF Design of Normal Conducting Deflecting Structures for the Advanced Photon Source | impedance, photon, electron, gun | 2427 | |||||
|
Use of normal conducting deflecting structures for production of short x-ray pulses is now being implemented at the Advanced Photon Source (APS). The structures have to produce up to 6 MV maximum deflection per structure at a 1kHz repetition rate. At the same time, the nominal beam quality must be maintained throughout the APS ring. Following these requirements, we proposed 2815 MHz standing wave deflecting structure with heavy wakefield damping. In this paper, we discuss the design considerations and present our current results.
|
|
|
|||||
WEPMS042 | Optimization of the Low-Loss SRF Cavity for the ILC | coupling, dipole, simulation, superconductivity | 2439 | |||||
|
Funding: Work supported by DOE contract DE-AC02-76SF00515. |
The Low-Loss shape cavity design has been proposed as a possible alternative to the baseline TESLA cavity design for the ILC. The advantages of this design over the TESLA cavity are its lower cryogenic loss, and higher achievable gradient due to lower surface fields. High gradient prototypes for such designs have been tested at KEK (ICHIRO) and JLab (LL). However, issues related to HOM damping and multipacting (MP) still need to be addressed. Preliminary numerical studies of the prototype cavities have shown unacceptable damping for some higher-order dipole modes if the typical TESLA HOM couplers are directly adapted to the design. The resulting wakefield will dilute the beam emittance thus reduces the machine luminosity. Furthermore, high gradient tests on a 9-cell prototype at KEK have experienced MP barriers although a single LL cell had achieved a high gradient. From simulations, MP activities are found to occur in the end-groups of the cavity. In this paper, we will present the optimization results of the end-groups for the Low-Loss shape for effective HOM damping and alleviation of multipacting. Comparisons of simulation results with measurements will also be presented. |
|
|||||
WEPMS048 | Modelling Imperfection Effects on Dipole Modes in TESLA Cavity | dipole, coupling, polarization, pick-up | 2454 | |||||
|
Funding: Work supported by DOE contract DE-AC02-76SF00515 |
The actual cell shape of the TESLA cavities differ from the ideal due to fabrication errors, the addition of stiffening rings and the frequency tuning process. Cavity imperfection shift the dipole mode frequencies and alter the Qext's from those computed for the idea cavity. A Qext increase could be problematic if its value exceeds the limit required for ILC beam stability. To study these effects, a cavity imperfection model was established using a mesh distortion method. The eigensolver Omega3P was then used to find the critical dimensions that contribute to the Qext spread and frequency shift by comparing predictions to TESLA cavity measurement data. Using the imperfection parameters obtained from these studies, artificial imperfection models were generated and the resulting wakefields were used as input to the beam tracking code Lucretia to study the effect on beam emittance. In this paper, we present the results of these studies and suggest tolerances for the cavity dimensions. |
|
|||||
WEPMS050 | HOM and LOM Coupler Optimizations for the ILC Crab Cavity | dipole, coupling, pick-up, simulation | 2457 | |||||
|
Funding: Work supported by DOE contract DE-AC02-76SF00515 |
The FNAL 9-cell 3.9GHz deflecting cavity designed for the CKM experiment was chosen as the baseline design for the ILC BDS crab cavity. Effective damping is required for the lower-order TM01 modes (LOM), the same-order TM11 modes (SOM) as well as the HOM modes to minimize the beam loading and beam centroid steering due to wakefields. Simulation results of the original CKM design using the eigensolver Omega3P showed that both the notch filters of the HOM/LOM couplers are very sensitive to the notch gap, and the damping of the unwanted modes is suboptimal for the ILC. To meet the ILC requirements, the couplers were redesigned to improve the damping and tuning sensitivity. With the new design, the damping of the LOM/SOM/HOM modes is significantly improved, the sensitivity of the notch filter for the HOM coupler is reduced by one order of magnitude and appears mechanically feasible, and the LOM coupler is simplified by aligning it on the same plane as the SOM coupler and by eliminating the notch filter. In this paper, we will present the coupler optimization and tolerance studies for the crab cavity. |
|
|||||
WEPMS056 | High Current, Large Aperture, Low HOM, Single Crystal Nb 2.85GHz Superconducting Cavity | simulation, electron, higher-order-mode, synchrotron | 2472 | |||||
|
Funding: Footnotes: The project was funded by the US Department of Energy under contract DE-FG02-05ER84346 |
There is an increasing demand for High beam Current, high Radio-Frequency (RF) power S-band cavities in existing and new accelerator projects to produce a very brilliant, broadband, teraherz coherent synchrotron radiation source (CRS). To achieve this goal, the RF cavities must be upgraded to a gap voltage of 1.5 MV in the limited space available in the machine with a high gradient superconducting cavity. At the present time there are no cavities and accessories designed to support the high beam currents of up to 100 mA and at the same time provide a high gap voltage at such a high S-band frequency. AMAC proposed a High Current, Large Aperture, Low HOM, Single Crystal Nb 2.85GHz Superconducting Cavity with high RF Power Coupler and HOM absorber device. Comprehensive simulation and optimization to determine the SRF cavity parameters to meet the requirements, provided two alternate designs for the RF input couplers, performed a detailed Higher Order Modes (HOM) analysis, and proposed an HOM absorber concept to dampen the modes exited in the cavity due to the high beam current and high bunch intensity. |
|
|||||
WEPMS063 | Preliminary Results from Prototype Niobium Cavities for the JLab Ampere-Class FEL | vacuum, coupling, cryogenics, electron | 2487 | |||||
|
Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177, and by the office of Naval Research under contract to the Department of Energy. |
In a previous paper the cavity* design for an Ampere-class cryomodule was introduced. We have since fabricated a 1500 MHz version of a single cell cavity with waveguide couplers for HOM and fundamental power, attached to one end of the cavity, a 5-cell cavity made from large grain niobium without couplers and a complete 5-cell cavity from polycrystalline niobium featuring waveguide couplers on both ends. A 750 MHz single cell cavity without endgroups has also been manufactured to get some information about obtainable Q-values, gradients and multipacting behavior at lower frequency. This contribution reports on the various tests of these cavities.
* R. A.Rimmer et al.; EPAC 2006, paper MOPCH182 |
|
|||||
WEPMS068 | JLab High-Current CW Cryomodules for ERL and FEL Applications | simulation, vacuum, insertion, linac | 2493 | |||||
|
Funding: Authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177, and by The Office of Naval Research under contract to the Dept. of Energy. |
We describe the developments underway at JLab to develop new CW cryomodules capable of transporting up to Ampere-levels of beam currents for use in ERLs and FELs. Goals include an efficient cell shape, high packing factor for efficient real-estate gradient and very strong HOM damping to push BBU thresholds up by two or more orders of magnitude compared to existing designs. Cavity shape, HOM damping and ancillary components are optimized for this application. Designs are being developed for low-frequency (750 MHz), Ampere-class compact FELs and for high-frequency (1.5 GHz), 100 mA configurations. These designs and concepts can easily be scaled to other frequencies. We present the results of conceptual design studies, simulations and prototype measurements. These modules are being developed for the next generation ERL based high power FELs but may be useful for other applications such as high energy light sources, electron cooling, electron-ion colliders, industrial processing etc. |
|
|||||
WEPMS070 | Simulation and Measurements of a Heavily HOM-Damped Multi-cell SRF Cavity Prototype | simulation, dipole, impedance, coupling | 2496 | |||||
|
Funding: This manuscript has been authored by Jefferson Science Associates, LLC under U. S. DOE Contract No. DE-AC05-06OR23177, and by The Office of Naval Research under contract to the Dept. of Energy. |
After initial cavity shape optimization* and cryomodule development** for an Ampere-class FEL, we have simulated the whole 5-cell high-current (HC) cavity structure with six waveguide couplers for HOM damping and fundamental power coupling. The time-domain wakefield method using MAFIA is primarily used for calculation of the broadband impedance. Microwave Studio and Omega-3P are also used for the calculation of external Q (Qext) of individual HOMs. A half scale (1497MHz) single-cell model and a 5-cell copper cavity including dummy HOM waveguide loads were fabricated. Details of measurement results on these prototypes including HOM Qext spectrum, bead-pull data, data analysis technique and comparison to the simulations will be presented.
* H. Wang et. al., "Elliptical Cavity Shape Optimization for Acceleration and HOM Damping," Proc. PAC 05, Knoxville TN, USA, 2005* R. A.Rimmer et al.; EPAC 2006, paper MOPCH182 |
|
|||||
WEPMS091 | Conceptual Design of the NSLS-II RF Systems | lattice, wiggler, booster, injection | 2550 | |||||
|
RF system requirements are derived from machine parameters and beam stability specifications. The conceptual design of the RF system for NSLS-II to meet these requirements is presented, consisting of 500 MHz superconducting main cavities, 1500 MHz SCRF harmonic cavities for bunch lengthening, and the RF power and cryogenic systems.
|
|
|
|||||
THOAKI02 | The Cornell ERL Superconducting 2-Cell Injector Cavity String and Test Cryomodule | alignment, emittance, linac, cryogenics | 2572 | |||||
|
Funding: Work supported by NSF. |
Cornell University is developing and fabricating a SRF injector cryomodule for the acceleration of the high current (100 mA) beam in the Cornell ERL prototype and ERL light source. Major challenges include emittance preservation of the low energy, ultra low emittance beam, cw cavity operation, and strong HOM damping with efficient HOM power extraction. Prototypes have been completed for the 2-cell niobium cavity with helium vessel, coaxial blade tuner with piezo fine tuners, twin high power input couplers, and beam line HOM absorbers loaded with ferrites and ceramics. Axial symmetry of HOM absorbers, together with two symmetrically placed input couplers per cavity, avoids transverse on-axis fields, which would cause emittance growth. A one-cavity cryostat has been designed following concepts of the TTF cryostat, and is presently under fabrication and assembly. The cryostat design has been optimized for precise cavity alignment, good magnetic shielding, and high dynamic cryogenic loads from the RF cavities, input couplers, and HOM loads. In this paper we report on the status of the assembly and first test of the one-cavity test cryostat. |
|
Slides
|
|
|
||
THOAKI03 | Revision of Accelerating and Damping Structures for KEK STF 45 MV/m Accelerator Modules | coupling, simulation, linac, higher-order-mode | 2575 | |||||
|
KEK is constructing its superconducting RF test facility and installing 1.3 GHz superconducting accelerator structures. Learning from experience with our first 45MV/m 9-cell structures, we have revised accelerating structures as well as higher order mode dampers for improved performance. Problems found in the earlier structures are discussed and solutions are presented. New experimental results will be also reported.
|
|
|
Slides
|
|
|
||
THICKI05 | European Industries Potential Capabilities on Cryogenics for the Future IlC | cryogenics, linac, positron, collider | 2704 | |||||
|
Following the construction of LHC, the European industries have demonstrated there ability to construct complete helium and nitrogen refrigeration systems both for the needs of the huge accelerator and the associated detectors. Eight 18 kW at 4.5 K and 2.4 kW at 1.8 K helium refrigeration systems have been constructed. Each refrigeration system is connected to 3 km of the 27 km long accelerator thanks to interconnecting valve boxes and high performances helium transfer lines. This is the biggest refrigeration system ever constructed in the world. The demand for cryogenics for the future ILC project is comparable in terms of equipment sizes but even bigger in terms of number of units required. The present refrigeration system scenario of ILC includes ten 22 kW at 4.5 K refrigerators and twelve 4.1 kW at 2 K refrigerators. In the present paper, this scenario will be presented and compared to the realizations done by the European Cryogenic Industries. Contact : Pascale.dauguet@airliquide.com
|
|
|
Slides
|
|
|
||
THPMN016 | Study of Fill Patterns for the ILC Electron Damping Ring | ion, electron, simulation, ion-effects | 2739 | |||||
|
Funding: This work is supported by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899 |
Ion effects are detrimental to the performance of the electron damping ring for the International Linear Collider (ILC). Irregular bunch patterns, e.g. short bunch trains with interleaved gaps, are an effective way to alleviate ion effects. In this paper, we discuss the fill patterns and their impact on the ion effects for the ILC electron damping ring. |
|
|||||
THPMN028 | Development of the Strip-line Kicker System for ILC Damping Ring | kicker, extraction, power-supply, electromagnetic-fields | 2772 | |||||
|
The performance of the kicker system for the International Linear collider(ILC) is the one of the key component to determine the damping ring(DR) circumference and the train structure. The parameters are discussing at the baseline configuration design for the ILC. The bunch trains in the linac are 2820(5640) bunches with 308(154) ns spacing and the repetition rate is 5Hz. The bunch spacing in the DR is 6(3) ns. The kicker has to have fast rise and fall times of 6(3) ns and the repetition rate of 3.25(6.5) MHz. The development work of the kicker system using multiple strip-lines is carried out at KEK-ATF. The beam test result of the single unit is described. Also Experimental results on new scheme to improve the rise and fall times will be presented.
|
|
|
|||||
THPMN074 | The Status of the HeLiCal Contribution to the Polarised Positron Source for the International Linear Collider | undulator, positron, simulation, electron | 2874 | |||||
|
The positron source for the International Linear Collider is a helical undulator-based design, which can generate unprecedented quantities of polarised positrons. The HeLiCal collaboration takes responsibility for the design and prototyping of the superconducting helical undulator, which is a highly demanding short period device with very small aperture, and also leads the start to end simulations of the polarised electrons and positrons to ensure that the high polarisation levels generated survive from the source up to the collision point. This paper will provide an update on the work of the collaboration, focusing on these two topic areas, and will also discuss future plans.
|
|
|
|||||
THPMN075 | Alignment Sensitivities in the ILC Damping Rings | alignment, emittance, lattice, quadrupole | 2877 | |||||
|
For the International Linear Collider to reach its design luminosity, the damping rings must achieve a vertical emittance that is a factor of two below that achieved in any operating storage ring so far. Magnet alignment, orbit control and coupling correction are therefore critical issues for the ILC damping rings. We compare alignment sensitivities in some recent designs for the ILC damping ring lattices, and discuss the results of tuning simulations using different algorithms for correcting the vertical dispersion and the coupling.
|
|
|
|||||
THPMN083 | Spin Tracking at the International Linear Collider | polarization, linac, positron, simulation | 2901 | |||||
|
Funding: This work is supported in part by the Commission of the European Communities under the 6th Framework Programme "Structuring the European Research Area", contract number RIDS-011899. |
Polarized electron and positron beams are foreseen for the future International Linear Collider (ILC), with polarized electrons already included in the baseline design and polarized positrons seen as a highly-desirable upgrade. High precision physics requires the polarization of both beams to be known with a relative uncertainty of approximately 0.5% or better. Therefore all possible depolarization effects that could operate between the polarized sources and the interaction regions have to be carefully modelled. The "heLiCal" collaboration aims to provide a full "cradle-to-grave" analysis of all depolarization effects at the ILC, and to develop software tools to carry out appropriate computer simulations. In this paper we report on the first phase of our work which includes extensive simulations of the ILC spin-dynamics and a detailed study of beam-beam depolarization effects at the interaction point(s). |
|
|||||
THPMN111 | A Kicker Driver for the International Linear Collider | kicker, linear-collider, collider, positron | 2972 | |||||
|
Diversified Technologies, Inc. (DTI), under a SBIR grant from the U. S. Department of Energy, is developing a driver for a kicker strip-line deflector which inserts and extracts charge bunches to and from the electron and positron damping rings of the International Linear Collider. The deflector requires a driver capable of 10 kV, 200 A pulses of 2 ns duration, after-pulse clamping of the deflector voltage to less than one volt within six nanoseconds, and must function at burst rates of 3 to 6 MHz. The driver must also effectively absorb high-order mode signals emerging from the deflector itself. In this paper, DTI will describe a promising approach to the design of the kicker driver involving high voltage DSRDs (Drift Step Recovery Diodes) and high voltage MOSFETs. In addition, our design approach to meeting the challenges posed by the ILC requirements will be discussed.
|
|
|
|||||
THPMN115 | Injection and Extraction Lines for the ILC Damping Rings | quadrupole, extraction, kicker, injection | 2984 | |||||
|
Funding: This work was supported by the U. S. Department of Energy under Contract No. DE-AC02-05CH11231. |
The current design for the injection and extraction lines into and out of the ILC Damping Rings is presented as well as the design for the abort line. Due to changes of the geometric boundary conditions by other subsystems of the ILC a modular approach has been used to be able to respond to recurring layout changes while reusing previously designed parts. Available beam dynamics studies for those lines are discussed. |
|
|||||
THPMS005 | Observation of Wakefields in a 17 GHz Metallic Photonic Bandgap (PBG) Structure | higher-order-mode, vacuum, radiation, linac | 3002 | |||||
|
Funding: Work supported by the Department of Energy, High Energy Physics, under contract DE-FG02-91ER40648. |
Results are reported on experimental wakefield measurements made on a 6 cell, 17 GHz metallic PBG accelerator structure. Wakefields were observed using a variety of detectors and methods. The PBG structure is open, containing no outer wall, and radiation has been observed through a window in the surrounding vacuum vessel. The input and output ports have also been used with windows to observe radiation coupling out of the ports. Estimations of radiation are made using HFSS and an EFIE code. Measurements have been made using video diode detectors, wavemeters, heterodyne receivers, and a bolometer. Plans are discussed for future experiments with injected power and longer structures. |
|
|||||
THPMS006 | Photonic Bandgap (PBG) Accelerator Structure Design | simulation, higher-order-mode, lattice, acceleration | 3005 | |||||
|
Funding: Work supported by the Department of Energy, High Energy Physics, under contract DE-FG02-91ER40648. |
High gradient structure design entails optimization of the gradient, while minimizing surface electric fields (associated with breakdown) and surface magnetic fields (associated with pulsed heating). Design studies are reported comparing metallic and dielectric PBG structures and standard disk-loaded waveguide. Operation in a higher order mode is considered. A variety of codes; HFSS, CST MWS, and Superfish have been used to compare and refine designs. Final design work is in preparation for a structure to be cold tested, tuned, and then processed to high gradient operation at the MIT HRC 17 GHz accelerator facility. |
|
|||||
THPMS011 | Design Considerations and Modeling Results for ILC Damping Ring Wigglers Based on the CESR-c Superconducting Wiggler | wiggler, linear-collider, electron, collider | 3014 | |||||
|
Funding: Funding provided by NSF grant PHY-0202078 |
The ILC damping rings require wiggler magnets with large physical aperture and with excellent field quality to maintain the dynamic aperture of the rings. We consider two possible designs derived from the wigglers presently in operation at the Cornell Electron Storage Ring. Design optimization has been performed based on detailed tracking calculations of dynamic aperture and tune footprint in a full model of the damping ring. Results of finite-element modeling, transfer functions, and the accuracy of analytic models of the wiggler field will be discussed. |
|
|||||
THPAN011 | Non Linear Space Charge Effects on Transverse Beam Stability | simulation, space-charge, betatron, impedance | 3247 | |||||
|
Funding: This work is funded by DINAIN, Division Nacional de Investigacion, Universidad Nacional de Colombia, Bogota - Colombia. |
Simbad code is used to study the combined effect of external non linearities and space charge non linearities on the beam stability using a simple FODO lattice. Gaussian and parabolic particle distribution are used for these simulations and results are compared with Mohl and Metral theoretical results. |
|
|||||
THPAN018 | Stability Thresholds for Transverse Dipole Modes with Nonlinear Space Charge, Chromaticity and Octupoles | space-charge, octupole, simulation, impedance | 3262 | |||||
|
Funding: Work supported by EU design study (contract 515873 -DIRACsecondary-Beams) |
Transverse stability due to combinations of chromaticity effect, nonlinear space charge and octupoles of different polarities plays an important role in the determination of the impedance budget for the FAIR synchrotrons. Different analytic approaches [*,**,etc.] have been suggested, for which no direct comparison has been made so far. In order to clarify this issue we perform numerical investigations employing the particle tracking code PATRIC and compare results of simulation scans with predictions of a dispersion relation. Space charge effects within self-consistent and 'frozen' models are used for comparisons, connection to beam transfer function studies is addressed.
* D. Moehl, CERN/PS 95-08 (DI), (1995)** M. Blaskiewicz, Phys. Rev. ST Accel. Beams 4, 044202, (2001) |
|
|||||
THPAN051 | Update on the ILC DR Alternative Lattice Design | lattice, dynamic-aperture, sextupole, wiggler | 3342 | |||||
|
In order to reduce the cost for ILC damping rings, an alternative lattice which is different from the baseline configuration design has been designed previously with modified FODO arc cells, and the total quadrupole and sextupole number has been reduced largely, compared with the baseline design. At the same time, to decrease the total cost involved in constructing access shafts needed to supply power, cryogenics etc. for the wigglers and other systems, the number of wiggler sections is decreased from 8 to 4, and further to 2. However, the momentum compaction of this lattice can not be tuned freely. In this paper, a new ILC damping ring lattice design with a variable momentum compaction will be presented, followed by the single particle dynamics associated studies.
|
*ypsun@ihep.ac.cn |
|
|||||
THPAN054 | Experiment on a Cold Test Model of a 2-Cell SC Deflecting Cavity for ALS at LBNL | simulation, coupling, electron, RF-structure | 3348 | |||||
|
Deflecting Cavities can be used to generate sub-pico-second X-ray pulse and are proposed at ALS at LBNL. A 2-cell structure has been simulated earlier to achieve the required deflecting voltage with damping waveguide to get low impedance. An aluminum cold test model has been made to demonstrate the simulation and the idea for damping LOM with waveguide. Field distribution as well as (R/Q)s are measured using 'bead-pull' method. Qs with/without waveguide loaded are measured and compared with simulation. Detailed configuration and experiment progress is presented.
|
|
|
|||||
THPAN066 | Improvements in FAKTOR2, a Code to Simulate Collective Effect of Electrons and Ions | electron, wiggler, dipole, vacuum | 3375 | |||||
|
Funding: Supported by the European Community under the 6th Framework Programme "Structuring the European Research Area". |
The electrostatic Particle in Cell code 'Faktor2' is extended to 3D, and is parallelised. Results for electron cloud buildup in end regions of damping ring dipoles for next generation linear colliders are presented. |
|
|||||
THPAN078 | An Elementary Analysis of Coupled-Bunch Instabilities | simulation, coupling, impedance, storage-ring | 3399 | |||||
|
We reconsider the equations of motion of wakefield coupled bunches in the light of recent developments in Delay Differential Equations. In the case of uniform resistive wall in a circular accelerator, we demonstrate an alternative way to obtain the growth rates. For each Fourier mode of bunch displacements, we show that multiple time domain modes can arise from an exact solution of the equation of motion. The growth rate as it is commonly defined corresponds to only one of them. The amplitude of each Fourier mode can therefore evolve with time in a way is not simply exponential. This is a result that has been observed in simulations of wakefield coupled bunches.
|
|
|
|||||
THPAN081 | Collimator Wakefields: Formulae and Simulation | simulation, electromagnetic-fields, collimation | 3405 | |||||
|
The effect of a leading particle on a trailing particle due to resistive and geometric wakefields in collimators can be described by expanding in a series of angular mode potentials Wm(s). Several formulae for these are given in the literature. We compare these formulae with numerical predictions from codes that solve the EM field equations, and explore the claimed regions of validity. We also explore how the EM code results can be used to numerically obtain angular mode potentials suitable for use in tracking codes.
|
|
|
|||||
THPAN095 | Implementation and Performance of Parallelized Elegant | simulation, collective-effects, space-charge, linac | 3444 | |||||
|
Funding: Work supported by the U. S. Department of Energy, Office of Science, Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
The program Elegant* is widely used for design and modeling of linacs for free-electron lasers and energy recovery linacs, as well as storage rings and other applications. As part of a multi-year effort, we have parallelized many aspects of the code, including single-particle dynamics, wakefields, and coherent synchrotron radiation. We report on the approach used for gradual parallelization, which proved very beneficial in getting parallel features into the hands of users quickly. We also report details of parallelization of collective effects. Finally, we discuss performance of the parallelized code in various applications.
*M. Borland, APS Light Source Note LS-287, September 2000. |
|
|||||
THPAN096 | A 1-nm Emittance Lattice for the Advanced Photon Source Storage Ring | lattice, dynamic-aperture, emittance, undulator | 3447 | |||||
|
Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
We present a triple-bend lattice design that uses the current APS tunnel. The new lattice has a 1 nm-rad effective emittance at 7 GeV. A forty-period symmetric optics is presented. For the benefit of some X-ray user experiments, an optics with four special straight sections of one-third the beam size of normal sections was investigated as well. The associated nonlinear optical difficulties are addressed and simulation results are presented. |
|
|||||
THPAN097 | International Linear Collider Damping Ring Lattice Design | lattice, injection, dynamic-aperture, emittance | 3450 | |||||
|
Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
We present a lattice design based on the theoretical-minimum-emittance (TME) cell for the International Linear Collider (ILC0 6.6-km 5-GeV damping ring. Several areas are discussed: momentum compaction, lattice layout, injection and extraction, circumference adjusters, phase adjuster, and dynamic aperture calculation with multipole errors. |
|
|||||
THPAN099 | Direct Space-Charge Calculation in Elegant and Its Application to the ILC Damping Ring | space-charge, simulation, emittance, electron | 3456 | |||||
|
Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
A direct space-charge force model has been implemented in the tracking code elegant. The user can simulate transverse space-charge effects by inserting space-charge elements in the beamline at any desired position. Application to the International Linear Collider damping ring is presented in this paper. We simulated beam under equilibrium conditions, as well as the entire damping cycle from injection to extraction. Results show that beam halo is generated due to space charge effects. This would be a significant concern for the ILC damping ring and a detailed follow-up study is needed. |
|
|||||
THPAN106 | 6D Ionization Cooling Channel with Resonant Dispersion Generation | emittance, scattering, focusing, resonance | 3477 | |||||
|
Funding: Work supported by the Universities Research Assoc., Inc., under contract DE-AC02-76CH03000 with the U. S. Dept. of Energy |
For muons with preferable for ionization cooling momentum <300MeV/c the longitudinal motion is naturally undamped. In order to provide the longitudinal damping a correlation between muon momentum and transverse position - described in terms of the dispersion function - should be introduced. In the present report we consider the possibility of dispersion generation in a periodic sequence of alternating solenoids (FOFO channel) by choosing the tune in the second passband (i.e. above half-integer per cell) and tilting the solenoids in adjacent cells in the opposite direction. Analytical estimates as well as simulation results for equilibrium emittances and cooling rates are presented. |
|
|||||
THPAS066 | CMAD: A New Self-consistent Parallel Code to Simulate the Electron Cloud Build-up and Instabilities | electron, simulation, lattice, storage-ring | 3636 | |||||
|
Funding: Work supported by the Director, Office of Science, High Energy Physics, U. S. DOE under Contract No. DE-AC02-76SF00515. |
We present the features of CMAD, a newly developed self-consistent code which simulates both the electron cloud build-up and related beam instabilities. By means of parallel (Message Passing Interface - MPI) computation, the code tracks the beam in an existing (MAD-type) lattice and continuously resolve the interaction between the beam and the cloud at each element location, with different cloud distributions at each magnet location. CMAD simulates single-and coupled-bunch instability, allows tune shift, dynamic aperture and frequency map analysis and the determination of the secondary electron yield instability threshold. Preliminary results are presented. |
|
|||||
THPAS090 | A Multipurpose Coherent Instability Simulation Code | radiation, simulation, synchrotron, dipole | 3690 | |||||
|
Funding: Work performed under the United States Department of Energy Contract No. DE-AC02-98CH1-886 |
A multipurpose coherent instability simulation code has been written, documented, and released for use. TRANFT (tran-eff-tee) uses fast Fourier transforms to model transverse wakefields, transverse detuning wakes and longitudinal wakefields in a computationally efficient way. Dual harmonic RF allows for the study of enhanced synchrotron frequency spread. When coupled with chromaticity, the theoretically challenging but highly practical post head-tail regime is open to study. Detuning wakes allow for transverse space charge forces in low energy hadron beams, and a switch allowing for radiation damping makes the code useful for electrons. |
|
|||||
THPAS095 | Ferrite-lined HOM Absorber for the e-Cool ERL | simulation, dipole, resonance, electron | 3705 | |||||
|
Funding: Work performed under Contract No. DE-AC02-98CH1-886 with the U. S. Department of Energy. |
An R&D facility for an Energy Recovery Linac (ERL) intended as part of the 'Electron-Cooling Xperiment' for RHIC is being constructed at this laboratory. The center piece of the project is the experimental 5-cell 703.75 MHz superconducting ECX cavity. Successful operation will depend on effective HOM suppression, and it is planned to achieve HOM damping exclusively with room temperature ferrite absorbers. A ferrite-lined pillbox model with dimensions reflecting the operational unit was assembled, and the cavity resonances and quality factors were determined from scattering coefficient measurements and were interpreted as surface impedance. Results from a 5-cell copper cavity with an attached ferrite absorber prototype are used for the prediction of the ECX cavity HOM damping. A rotational symmetric ferrite-lined pillbox was analyzed theoretically and compared with the simulation codesμWave Studio, GdfidL, and Superfish. Discrepancies of the resonance frequencies and Q-values were found, and steps to reach agreement are discussed. |
|
|||||
THPAS104 | Simulations of RHIC Coherent Stabilities Due To Wakefield and Electron Cooling | electron, simulation, ion, impedance | 3726 | |||||
|
A circulating ion beam in the presence of electron cooling can experience varies instabilities if the electron beam intensity is above a certain threshold. Firstly the electric field generated by the electron beam can introduce two stream instabilities of varies modes; this has already been observed in the Fermilab Recycler ring. Secondly, longitudinal cooling of the momentum spread will reduce the Landau damping efficiency and thus may make the overcooled ion beam unstable. The thresholds and growth rates of varies two stream instability modes are discussed for the existing RHIC electron cooler design. Both simulation and theoretical results are shown for the thresholds of the instabilities caused by overcooling.
|
|
|
|||||
FRPMN014 | 3D Simulation of Coherent Instabilities in Long Bunches Induced by the Kicker Impedances in the FAIR Synchrotrons | impedance, space-charge, simulation, kicker | 3919 | |||||
|
Funding: Work supported by the European Community under the FP6 programme: Structuring the European Research Area - Specific Support Action - DESIGN STUDY (contract 515873 - DIRACsecondary-Beams). |
3D simulation studies of the transverse impedance budget for long bunches in the FAIR synchrotrons have been started. Important transverse instability driving sources are the thin resistive wall and the kicker impedances. Major concerns are the required low momentum spreads and the additional loss of Landau damping due to the space charge tune shift. The simulation code PATRIC has been extended in order to predict coherent instability thresholds with space charge and for broadband impedance sources. Examples of code benchmarking using the numerical Schottky noise, analytical stability boundaries and comparisons with other codes will be discussed. The improvement of transverse stability in long bunches relative to a coasting beam is analyzed for different rf wave forms. Conclusions for the impedance budget in the FAIR synchrotrons are drawn. |
|
|||||
FRPMN022 | Analysis of Multi-Turn Beam Position Measurements in the ANKA Storage Ring | kicker, sextupole, storage-ring, electron | 3964 | |||||
|
The observation of betatron oscillations following a deflection by a kicker pulse offers the possibility to study various machine parameters. The damping of the centre-of-charge signal's amplitude for one bunch, for example, depends chromaticity, energy loss, momentum compaction factor and impedance. A new multi-turn acquisition system based on LIBERA ELECTRON units (http://www.i-tech.si) has been installed in the ANKA storage ring. First analyses of the thus acquired data for different machine conditions reveal systematic limitations in the current ANKA multi-turn setup. Measurements preformed under varying conditions are presented and discussed with respect to the influence on future analysis.
|
* http://www.i-tech.si |
|
|||||
FRPMN033 | Adiabatic Damping During Acceleration in the Induction Synchrotron | acceleration, synchrotron, induction, beam-losses | 4009 | |||||
|
Damping in a bunch length during the acceleration in the induction synchrotron experiment *, where a single proton bunch injected from the KEK 500 MeV Booster and trapped by the barrier voltages is accelerated to 6 GeV, has been observed. Such a damping may be regarded as the adiabatic damping, as found in a conventional RF synchrotron. A technique to analytically deal with this phenomenon is well established in the RF synchrotron. A WKB solution is employed for the small amplitude synchrotron oscillation. However, a simple WKB approach is not available for the present barrier bucket acceleration, because longitudinal motion always depends on the oscillation amplitude. This paper discusses a novel technique capable of quantitatively predicting the adiabatic phenomenon which has been newly developed. The analytical results were worked out and verified using simulations for ideal conditions. Theoretical approach tells us that a bunch length in the barrier bucket acceleration never continues to shrink but achieves a constant value corresponding to the time duration between the barrier voltage pulses.
|
* K. Takayama et al., "Experimental Result of the Induction Synchrotron", appear in Phys. Rev. Lett. (2007) and in this conference. |
|
|||||
FRPMN037 | Ion Instability in the ILC Damping Ring | ion, simulation, feedback, electron | 4030 | |||||
|
Ions created by electron beam trapped in a bunch oscillate with a certain frequency, with the result that the beam oscillate with the same frequency. Recent high intensity and low emittance rings, the growth rate of this ion instability is very rapid. Super B factory and ILC damping ring, which are similar design parameter, are extremely low emittance. We discuss the ion instability for these rings.
|
|
|
|||||
FRPMN041 | Study on the Longitudinal Impedance of BPM for KEKB and Super KEKB | impedance, resonance, simulation, luminosity | 4048 | |||||
|
The longitudinal impedance of the KEK B-factory (KEKB) button-type beam position monitors (BPMs) was recalculated by MAFIA in preparation for a future plan to increase the beam current. The diameter and the gap of the button electrode were 12 mm and 1 mm, respectively. For High Energy Ring (HER), an asymmetric structure was applied to extract the TE110 mode into the coaxial cable. The Q-value and shunt impedance were estimated at 91 and 17 Ω (at 7.6 GHz) respectively, and the beam current limit for longitudinal multi-bunch instability was 2.6 A. On the other hand, the electrode of Low Energy Ring (LER) BPM had a symmetric structure and the Q-value and shunt impedance were estimated at 133 and 8 Ω (at 7.6 GHz). In this case, the current limit was 1.7 A. Based on the experiences at the KEKB, the new BPM was designed for the Super KEKB, a future high-intensity B-factory at KEK. In order to reduce the impedance the electrode diameter was cut down to 6 mm from 12 mm. The Q-value and shunt impedance were estimated at 23 and 2 Ω (at 13 GHz). The current limit was expected to be about 7 A in full bucket operation (5120 bunches), and more than 10 kA in 4-bucket spacing operation.
|
|
|
|||||
FRPMN091 | Simulation of HOM Wakefields in the Main ILC Cavities | linac, simulation, dipole, emittance | 4288 | |||||
|
We investigate the electromagnetic field (e.m.) excited by a train of multiple bunches in the main superconducting linacs of the ILC. These e.m. fields are represented as a wake-field. Detailed simulations are made for the modes which constitute the long-range wake-field in new high gradient cavity structures. In particular, we focus our study on the modes in re-entrant and low loss Ichiro cavities. Modes trapped within a limited number of cells can give rise to a significant diminution in the emittance of the beam and we pay particular attention to these modes. Beam tracking simulations on the resulting emittance dilution over the entire length of the linac are made in order to provide details on the damping which is necessary for modes with particularly large kick factors.
|
|
|
|||||
FRPMN108 | Coupled-Bunch Instability Study of Multi-cell Deflecting Mode Cavities for the Advanced Photon Source | dipole, impedance, photon, feedback | 4348 | |||||
|
Funding: Work supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
The short-pulse X-ray project at the Advanced Photon Source (APS) uses three room-temperature nine-cell 2.815 GHz deflecting-mode cavities in a straight section. Undamped, these cavities' higher-order and lower-order resonator modes will cause multi-bunch instabilities in longitudinal and transverse planes for any bunch pattern of a 1'000mA store. Damping of these modes must be part of the design of the cavities. We report calculations of instability growth rates and tracking simulations that were essential in specifying the rf design of the damping structures. We used various operating bunch patterns and scanned levels of damping of the cavities. Because one of the operating bunch patterns is not symmetric, we used a normal mode analysis * implemented in the APS code clinchor. Our calculation included random sampling of resonator frequencies in a reasonable range. We found that staggering of frequencies is only effective for modes that could not be heavily damped.
* K. Thompson and R. Ruth, PAC 1989 |
|
|||||
FRPMN110 | Transverse Multibunch Bursting Instability in the APS Storage Ring | single-bunch, coupling, vacuum, emittance | 4360 | |||||
|
Funding: Work supported by U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. |
The horizontal bursting instability was first observed in a single bunch in the APS in 1998, soon after operation began. Above the instability threshold, the bursting is characterized by exponentially growing bunch centroid oscillations that saturate, then decay, repeating quasi-periodically. More recently, bursting was also observed with multiple bunches in both the horizontal and vertical planes, showing that this is not purely a single-bunch phenomenon. On the other hand, the multibunch instability threshold is strongly dependent on bunch spacing, and the dependence is markedly different for the two transverse planes. Depending on the bunch spacing, the bunch-to-bunch oscillations are sometimes coupled, sometimes not. In this paper, we discuss the threshold in terms of the chromaticity required to stabilize the beam. We present instability imaging data using a streak camera that shows the bunch-to-bunch oscillation phase, and turn-by-turn beam position histories that give the bursting time dependence for different bunch spacings. Finally, we discuss the machine impedance and measured tune shift with current. |
|
|||||
FRPMS009 | Calculating the Nonlinear Tune Shifts with Amplitude using Measured BPM Data | lattice, optics, synchrotron, resonance | 3889 | |||||
|
An algorithm is proposed to calculate the approximate tune shifts with amplitude using only the linear transfer map of a circular accelerator and with little or no information on higher order nonlinearities. To extract information about the nonlinear dynamics, the decay rate of the average amplitude of the particle distribution after an instantaneous transversal horizontal or vertical kick is used. This method works when strong low-order resonances are not present, that is where the linear lattice rather than the nonlinear driving terms dominates the machine dynamics. Nonlinear normal form transformation and differential algebra methods are employed to establish the connection between measurement results and the nonlinear tune shifts with amplitude. Proposed algorithm is applicable to a wide range of circular accelerators.
|
|
|
|||||
FRPMS039 | Growth Time of Longitudinal Coupled Bunch Mode Instability in the Duke FEL Facility | storage-ring, kicker, feedback, electron | 4036 | |||||
|
To determine the required power of an RF amplifier for the longitudinal feedback system (LFS), the growth time of the longitudinal coupled bunch mode instability (CBMI) in the Duke storage ring should be known in advance. In 2005, we measured the longitudinal beam instability with four and eight symmetrically filled buckets in the Duke storage ring. By analyzing measured data, the growth time of the longitudinal CBMI can be estimated. At a beam energy of 274 MeV, the projected growth time is about 0.37 ms for a total stored current of 160 mA. To damp harmful longitudinal CBMI with a relative energy deviation of 0.1% (rms) within the growth time, a sufficient RF power of 135 W (rms) should be delivered to an LFS kicker at a central frequency of 758.8375 MHz. In this paper, we describe measurements of the growth time and the estimation of the RF power requirement for the LFS.
|
|
|
|||||
FRPMS061 | Impedance and Single Bunch Instability Calculations for the ILC Damping Rings | impedance, lattice, single-bunch, simulation | 4141 | |||||
|
Funding: Work supported by US Department of Energy contract DE-AC02-76SF00515 |
One of the action items for the damping rings of the International Linear Collider (ILC) is to compute the broad-band impedance and, from it, the threshold to the microwave instability. For the ILC it is essential that the operating current be below threshold. Operating above threshold would mean that the longitudinal emittance of the beam would be increased. More seriously, above threshold there is the possibility of time dependent variation in beam properties (e.g. the "sawtooth" effect) that can greatly degrade collider performance. In this report, we present the status of our study including calculations of: an impedance budget, a pseudo-Green's function suitable for Haissinski equation and instability calculations, and instability calculations themselves. |
|
|||||
FRPMS078 | Numerical Study of RF-Focusing Using Fokker-Plank Equation | simulation, focusing, electron, synchrotron | 4228 | |||||
|
Funding: Work supported by US DOE contract DE-AC02-76SF00515 |
Based on numerical solution of the Fokker-Plank Equation we study the effect of longitudinal damping on the modulation of the bunch length in a storage ring with high RF voltage and momentum compaction |
|
|||||
FRPMS080 | Simulation of the Beam-Ion Instability in the Electron Damping Ring of the International Linear Collider | ion, emittance, simulation, electron | 4240 | |||||
|
Funding: Work supported by the U. S. Department of Energy under contract DE-AC02-76SF00515 |
Ion induced beam instability is one critical issue for the electron damping ring of the International Linear Collider (ILC) due to its ultra small emittance of 2pm. Bunch train filling pattern is proposed to mitigate the instability and bunch-by-bunch feedback is applied to suppress it. Multi-bunch train fill pattern is introduced in the electron beam to reduce the number of trapped ions. Our study shows that the ion effects can be significantly mitigated by using multiple gaps. However, the beam can still suffer from the beam-ion instability driven by the accumulated ions that cannot escape from the beam during the gaps. The effects of beam fill pattern, emittance, vacuum and various damping mechanism are studied using self-consistent program, which includes the optics of the ring. |
|
|||||
FRPMS088 | Intrabeam Scattering and Touschek Lifetime for the Optical Stochastic Cooling experiment at the MIT-Bates South Hall Ring | emittance, undulator, insertion, synchrotron | 4279 | |||||
|
A proof-of-principal experiment of Optical Stochastic Cooling (OSC) at the MIT-Bates South Hall electron storage ring (SHR) has been proposed. To produce convincing cooling results, the ring will be run near 300 MeV. Beam emittances growth caused by Intrabeam scattering (IBS) is a major concern for the design of experiment. Touschek scattering imposes a dominant limit on beam lifetime. Evaluation of these effects is part of the design optimization process. Simulation analyses of cooling for a viable OSC experiment are presented.
|
|
|
|||||
FRPMS103 | Coupling Impedance of the CESR-B RF Cavities for the NSLS-II Storage Ring | impedance, storage-ring, coupling, vacuum | 4327 | |||||
|
CESR-B type superconducting cavities are under discussion for acceleration of the electron beam in the 3-GeV NSLS-II storage ring. In this paper we present a detailed investigation of longitudinal and transverse impedances of the cavity and transition assembly. Ferrite material is included in impedance analysis. Its effect on the short range wakepotential has been studied using the GdfidL code. Results of loss factors and kick factors are presented for a 3mm rms bunch length.
|
|
|
|||||
FRPMS113 | Touschek Lifetime Calculations and Simulations for NSLS-II | emittance, insertion, insertion-device, controls | 4375 | |||||
|
Funding: Work performed under the auspices of the US Department of Energy. |
The beam lifetime in most medium-energy synchrotron radiation sources is limited by the Touschek effect, which describes the momentum transfer from the transverse into the longitudinal direction due to binary collisions between electrons. While an analytical formula exists to calculate the resulting lifetime, the actual momentum acceptance necessary to perform this calculation can only be determined by tracking. This is especially the case in the presence of small vertical apertures at insertion devices. In this case, nonlinear betatron coupling leads to beam losses at these vertical aperture restrictions. In addition, a realistic model of the storage ring is necessary for calculation of the equilibrium beam sizes (particularly in the vertical direction) which are important for a self-consistent lifetime calculation. |
|