| Paper | Title | Page |
|---|---|---|
| THPC001 | Synthesis of Optimal Nanoprobe (Linear Approximation) | 2969 |
|
||
| High energy focused ion (proton) micro- and nanoprobes are intensively integrated to powerful analytical tool for different scientific and technological aims. Requirements for beam characteristics of similar focusing systems are extremely rigid. The value of demagnification for micro- and nanoprobes is the main optimality criteria, and as desirable value are in the range from 50 to 100 or even more. In the paper, we reconsider the basic properties of first order focusing systems from an optimal viewpoint. The matrix formalism allows us to formulate a nonlinear programming problem for all parameters of guiding elements. For this purpose there are used computer algebra methods and tools as the first step, and then some combination of special numerical methods. As a starting point for nanoprobe we consider so called “russian quadruplet”. On the next steps, we also investigate other types of nanoprobes. Some graphical and tabular data for nanoprobe parameters are cited as an example. | ||
| THPC002 | Synthesis of Optimal Nanoprobe (Nonlinear Approximation) | 2972 |
|
||
| This paper is a continuation of the paper devoted to synthesis of optimal nanoprobe in linear approximation. Here the main goal is the optimization of nanoprobe including nonlinear aberrations of different nature up to third order. The matrix formalism for Lie algebraic methods is used to account for nonlinear aberrations. This method gives a possibility to consider nonlinear effects separately. Here we mean that a researcher can start or remove different kind of nonlinearities. This problem is separated into several parts. On the first step, we consider possibilities of additional optimization for some structures, selected on the step of linear approximation. The most of aberrations have harmful character, and their effect must be maximally decreased. Therefore, on the next steps, some we use analytical and numerical methods for generation of nonlinear corrected elements. The matrix formalism allows reducing the correction procedure to linear algebraic equations for aberration coefficients. Some examples of corresponding results are given. | ||
| THPC003 | Sum of Emittance in the Presence of a Linear Coupling | 2975 |
|
||
|
In this article, the influence of linear coupling due to skew quadrupoles on the transverse equations of motion and emittances in accelerators is studied*. We first introduce the definition of the transverse single particle emittances using the Floquet transformation in alternating gradient as well as the constant focusing rings, then in the presence of the linear coupling, due to skew quadrupoles we introduce the coupled differential equations governing the particles motion and try to solve them by a direct method and also using the normal modes of motion to find the relation between the two transverse emittances. Based on smooth approximation and using the normal modes** we solve the equations of motion of a test charged particle and derive two new formulas for the sum of the emittances, and the conditions under which this sum is invariant.
*P. J.Bryant, CERN Acclerator School, CERN, PROCEEDINGS, 94-01, Vol. I. |
||
| THPC004 | Chromatic and Wakefield Effects in PSI-XFEL Linac | 2978 |
|
||
| Detailed knowledge about the wakefield and chromatic effects on electron beam emittance is an important issue to preserve the natural emittance of the beam in linear accelerators for FEL. The study of these two effects for beam and accelerator components imperfections in PSI-XFEL S-Band linear accelerator is presented. Emittance dilution caused by the beam coherent oscillations, accelerating section and quadrupole misalignments is analysed. The residual chromatic emittance dilution of the corrected trajectory is evaluated. | ||
| THPC005 | Conceptual Design of Booster Synchrotron forTPS | 2981 |
|
||
| A six-folded concentric booster of 489.6 m with non-dispersive straights of length 5.8 m is designed for TPS storage ring of 518.4 m. The structure consists of modified FODO lattice with defocusing quadrupole fields built in bending magnets. The designed emittance is less than 10 nm-rad at 3 GeV. In this paper, the phenomenon during the ramping from 150 MeV to 3.0 GeV including the eddy current effect, the evolutions of beam emittance, energy spread, and bucket acceptance, will be discussed. In addition, closed orbit correction scheme, aperture request as well as injection and extraction schemes are described. | ||
| THPC006 | Applications of a BPM-based Technique for Measuring Real Space Distributions in the Spallation Neutron Source Ring and Transport Lines | 2984 |
|
||
|
The SNS accumulator ring and associated transport lines are designed to accumulate and transport up to 1.5·1014 ppp to a liquid mercury target for neutron spallation. Since commissioning, a dedicated effort has been put forth to characterize the lattice and beam dynamics at low intensity. Toward this goal, a BPM-based technique for measuring real space beam distributions at low beam intensities was developed*. Recently, this technique has been used to diagnose and localize a strong source of coupling in the lattice, to verify and troubleshoot complementary diagnostics devices, and to provide data for code benchmarking. Other potential applications of this technique include investigations of single particle dynamics and resonances, studies of injection painting techniques, and possibly measurement of quadrupole power supply errors in the ring. In this paper we present the results of applying this technique to various situations in the SNS ring and transport lines, including the first ORBIT benchmarks of the SNS ring and RTBT.
*T. Pelaia et al, Nucl. Instr. And Methods, in progress. |
||
| THPC007 | Permanent Magnet Skew Quadrupoles for the Low Emittance LER Lattice of PEP-II | 2987 |
|
||
| The vertical emittance of the low energy ring (LER) in the PEP-II B-Factory was reduced by using skew quadrupoles consisting of permanent magnet material. The advantages over electric quadrupoles or rotating existing normal quadrupoles are discussed. To assure a high field quality a Biot Savart calculation was used to cancel the natural 12-pole component by using different size poles over a few layers. A magnetic measurement confirmed the high quality of the magnets. After installation and adjusting the original 12 skew and 16 normal quadrupoles the emittance contribution from the region close to the interaction point, which was the biggest part in the original design, was considerably reduced. | ||
| THPC008 | Constants and Pseudo-constants of Coupled Beam Motion in the PEP-II Rings | 2990 |
|
||
| Constants of beam motion help as cross checks to analyze beam diagnostics and the modeling procedure. Pseudo-constants, like the betatron mismatch parameter or the coupling parameter det C, are constant till certain elements in the beam line change then. This can be used to visually find the non-desired changes, pinpointing errors compared with the model. | ||
| THPC010 | Trajectory Correction in the Fermi@Elettra Linac | 2993 |
|
||
|
The effect of the static magnetic field errors and misalignment of the magnetic elements and linac modules on the beam trajectory in the Fermi@elettra linac [1] has been studied. Analytical description has been used to guide simulations of the trajectory correction using three different techniques. A control over the residual R56 transfer matrix element along the linac lattice has been applied. The importance of the linac structural transverse wake field for a reliable prediction of the bunch centroid dynamics has been demonstrated. Transverse deviations of bunch slices along the electron bunch induced by the wake fields have been calculated.
[1] S. Di Mitri, ST/M–07/01 (2007) |
||
| THPC011 | The CR-RESR Storage Ring Complex of the FAIR Project | 2996 |
|
||
| In frame of the FAIR project (at GSI, Germany) the CR-RESR storage ring complex has been designed for efficient cooling, accumulation and deceleration of antiproton and rare isotopes beams. The complex consists of the Collector Ring (CR) and the accumulator / decelerator ring RESR. The large acceptance CR will be operated at three different optical modes, two of them providing fast pre-cooling of antiprotons and rare isotopes. This ring will be also used as an instrument for mass measurements of very short-lived nuclei when tuned to an isochronous mode. The RESR will be used as accumulator of the antiprotons by means of the stochastic cooling technique and as a decelerator of rare isotopes. The structure of the CR and RESR lattices and its ion optical properties are described in this contribution. The beam dynamics of these rings at different operation scenario are discussed. | ||
| THPC012 | Longitudinal Beam Dynamics Studies for the FERMI@ELETTRA Linac | 2999 |
|
||
| FERMI is a single-pass FEL project under construction at Sincrotrone Trieste Laboratory. It will be driven by the present warm S-band linac, upgraded by the addition of seven accelerating sections to bring its working energy up to 1.2 GeV. The goal of the project is to have an X-ray user facility covering the wavelength region between 100 -10 nm. The stringent constraints on the electron beam parameters required by FERMI, such as emittance, pulse to pulse energy and current stabilities, and time of arrival of the bunch at the input of the undulator chain, impose very stringent requirements on the parameters and operating conditions of the linac accelerating sections. To address the problem, i.e. evaluating the operating conditions of the machine and the flexibility of the adopted layout, beam dynamics studies with the LiTrack code have been performed. Here the results of different linac settings as well as the allowed variations in terms of RF phase and amplitude of the accelerating field are presented and discussed. | ||
| THPC013 | Start to End Simulations of Transverse to Longitudinal Emittance Exchange at the A0 Photoinjector | 3002 |
|
||
| Various schemes to exchange the transverse and longitudinal emittance have been proposed (Cornacchia and Emma, Kim et.al). One scheme involves a deflecting mode RF cavity between two doglegs to exchange the horizontal and longitudinal emittances. This will produce a complete and uncoupled emittance exchange in the thin cavity limit using first order matrix optics. Various other effects, such as a finite length cavity, can leave the emittances coupled after the exchange and dilute the final emittances. Other effects such as space charge and synchrotron radiation can only be investigated through simulations. An exchange experiment is underway at the A0 Photoinjector at Fermilab. In this paper we present start to end simulations of the experiment using various codes to account for space charge and Coherent Synchrotron Radiation effects. Astra is used to simulate all of the straight sections, including the deflecting mode RF cavity. CSR track simulates the doglegs, and the spectrometer. The results of these simulations are compared with analytical approximations and preliminary data. The effect on the exchange is also discussed. | ||
| THPC014 | Investigation of Possible CSR Induced Energy Spread Effects with the A0 Photoinjector Bunch Compressor | 3005 |
|
||
| The bunch compressor of the A0 Photoinjector at Fermilab was removed this past spring to install a transverse to longitudinal emittance exchange experiment. Prior to its removal questions arose about the possibility of observing the effects of Coherent Synchrotron Radiation on the compressed beam. The energy spread of the beam with and without compression was measured to observe any changes. Various beam charges were used to look for square law effects associated with CSR. No direct observation of CSR was attempted because the design of the vacuum chamber did not allow it. In this paper we report the results of these experiments and comparison with simulations using ASTRA and CSRTrack. The results are compared with analytical approximations. The implications for the ongoing transverse to longitudinal emittance exchange experiment are discussed. | ||
| THPC015 | Computational Beam Dynamics Studies for Improving the Ring Injection and Extraction Systems in SNS | 3008 |
|
||
| The ring injection and extraction systems must function as designed in order for the Spallation Neutron Source (SNS) to achieve its specified performance. In commissioning and early operations we have encountered problems that have been traced to these systems. We experienced high beam losses in and around the injection dump, the rectification of which has necessitated significant study and development by a multidisciplinary team. The results include a number of enhancements of existing features and the addition of new elements and diagnostics. The problem in the extraction region stems from tilted beam distributions observed in the ring-to-target beam transport line (RTBT) and on the target, thus complicating the control of the beam-on-target distribution. This indicates the inadvertant introdution of x-y beam coupling somewhere upstream of the RTBT. The present paper describes computational studies, using the ORBIT Code, addressed at the detailed understanding and solution of these problems. | ||
| THPC016 | Beam Optics of the PEFP Modified Beam Lines | 3011 |
|
||
| The 100 MeV Linac of the Proton Engineering Frontier Project (PEFP) is designed to supply 20 MeV and 100 MeV proton beams to user groups. In order to extract 20 MeV proton beams, a 45 degrees bending magnet is installed after 20 MeV DTL tank. The extracted proton beams are separated into five target rooms via a AC bending magnets. For 100 MeV beams, we use the same distribution schemes. Recently, the layout of the beam lines are modified to be short and compact. The work summaries the beam optics calculation of the modified beam lines. | ||
| THPC017 | Optimisation of a Beam Transfer FODO Line | 3014 |
|
||
| With in view the design of the CLIC long transfer lines, we developed a formal approach for the optimisation of a straight FODO line. Optimum phase advance and cell length depending on beam parameters are derived for power consumption, overall cost and sensitivity to quadrupole misalignment. | ||
| THPC018 | Beam Dynamics Issues in the CLIC Long Transfer Line | 3017 |
|
||
| Both the main beam and the drive beam of the CLIC project must be transported from the central production site to the head of the main linacs over more than twenty kilometres. Over such distances chromatic aberrations are substantial. With long distances and large beam currents, detuning and instabilities associated to ion production and multi-bunch resistive wall effects must also be considered. These effects are quantified and simulated. Based on these results, we propose a baseline design for these two lines. | ||
| THPC020 | Emittance Exchange at the Fermilab A0 Photoinjector | 3020 |
|
||
| A transverse to longitudinal emittance exchange experiment is underway at the A0 Photoinjector at Fermilab. Our scheme employs a TM110 deflecting mode RF cavity between two magnetic doglegs proposed by Kim et. al. The beamline has been installed, characterization of the beamline is complete and data taking has begun. In this paper we report on efforts to date to observe the transverse to longitudinal emittance exchange. Measurements will be compared to analytical predictions and simulations. | ||
| THPC021 | Investigations on a Q0 Doublet Optics for the LHC Luminosity Upgrade | 3023 |
|
||
| The Q0 scheme of the LHC insertion region is based on the introduction of a doublet of quadrupoles at 13 meters from IP. We present here the doublet optics and the magnets layout such as gradients, lengths, positions and apertures. In this scheme we show the gain in luminosity and chromaticity, with respect to a nominal layout with β*=0.25 (i.e. LHC phase 1 upgrade) and β*=0.15 m, due to a smaller beta-max. We show the alignment tolerance and the energy deposition issues, in Q0A-Q0B. We also consider shielding the magnets with liners. The capability of Q0 optics to limit the β function could be exploited after the LHC Phase 1 upgrade in order to reduce the β* below 0.25 m, leaving the upgraded triplet unchanged. | ||
| THPC023 | Optimization of the AGS Superconducting Helical Partial Snake Strength | 3026 |
|
||
| Two helical partial snakes, one is superconducting (called cold snake) and one is normal conducting (called warm snake), have preserved the polarization of proton beam up to 65% at the AGS extraction energy with the inject 82% polarization. In order to overcome the spin resonances, stronger partial snake is required. However, the stronger partial snake, the more titled stable spin direction that results in stronger horizontal intrinsic resonance. The balance between raising the spin tune gap generated by the snakes and reducing the titled stable spin direction has to be considered to maintain the polarization. Because the magnetic field of the warm snake is constant, only the cold snake with a maximum 3T magnetic field can be varied to find out the optimized snake strength. The paper presents the simulation results from the spin tracking with different cold snake magnetic fields. Some experimental data are also analyzed. | ||
| THPC024 | Closed Orbit Correction at the LNLS UVX Storage Ring | 3029 |
|
||
| The orbit correction of stored electrons in the LNLS storage ring often needs a few iterations to converge to the smallest distortion. This is caused in part by the residual coupling between transverse planes. This coupling effect can be included in the correction algorithm leading to the best orbit in just one iteration. However, in the LNLS ring, the number of monitors equals the number of vertical correctors but surpasses the number of horizontal correctors. This means that the vertical orbit can be corrected to zero at the position monitors in the decoupled situation but the horizontal orbit cannot. For the coupled case, the incapacity of zeroing the horizontal orbit leaks into the vertical plane. This problem can be addressed by the eigenvector method with constraints. | ||
| THPC025 | Further Advances in Understanding and Optimising Beam Dynamics in the Diamond Storage Ring | 3032 |
|
||
| We report the results of recent beam dynamics studies of the Diamond storage ring. These studies were aimed at both improving our understanding of the machine operation as well as establishing a reliable, well corrected lattice with long lifetime and high injection efficiency suitable for later top-up operation. Particular attention has been given to measuring and controlling the linear optics of the lattice, to determining the various contributions to the overall beam lifetime and to optimising the sextupole strengths for good on and off momentum dynamic aperture. For each topic, detailed comparisons with model predictions are also described. | ||
| THPC026 | Measurement of Complex Coupling Driving Term of Linear Difference Resonance Using Turn-by-turn Beam Position Monitors | 3035 |
|
||
| X-Y emittance coupling is one of the important measures of beam quality in an electron storage ring for high brilliant light source. We have developed a method of measuring complex coupling driving term C of linear difference resonance using turn-by-turn beam position monitors (BPMs), assuming the perturbation theory with the single resonance approximation. Since both amplitude and phase of the driving term are derived, we can uniquely determine the strength of two-degree-of-freedom skew quadrupole magnets for correction of the linear resonance coupling. Before the correction, the driving term was measured by the developed method at the SPring-8 storage ring where small skew quadrupole components are distributed as error magnetic fields. On the other hand, the linear resonance coupling was corrected using the counter skew quadrupole magnets, the strength of which was adjusted to minimize vertical beam size near the linear difference resonance. The measured driving term C was broadly consistent with the counter term calculated from the adjusted strength of skew quadrupole magnets for the coupling correction. | ||
| THPC027 | Pulsed RF Accelerator of Electrons with Beam Recirculation | 3038 |
|
||
| We discuss the project of upgrading existent 20 MeV L-band electron linac at Argonne National Laboratory aimed at electron energy increasing. It is shown that the proposed beam recirculation will provide on the accelerator output an electron beam with a pulse current 0.5 A and energy of particles 45 MeV. Problems of stability of recirculating beam are discussed. | ||
| THPC028 | High Energy Beam Transport Line for the IFMIF-EVEDA Accelerator | 3041 |
|
||
| The IFMIF-EVEDA accelerator will be a 9 MeV, 125 mA cw deuteron accelerator which will verify the validity of the design of the future IFMIF accelerator. A transport line is necessary to handle the high current beam from the DTL exit up to the beam dump. This line must produce the beam expansion to obtain an acceptable power density at the beam dump. Therefore the design of the transport line must consider the geometry and power handling capacity of the beam dump, the space requirements for diagnostics and the restrictions on the maximum length of the line. In addition, a bending magnet is required in order to avoid excessive irradiation of the diagnostics and line elements by neutrons and gammas produced at the beam dump and to perform energy spread measurements. In this contribution, the preliminary design of the high energy beam transport line will be presented. The results of a sensitivity study to the input beam and line elements errors will also be discussed. | ||
| THPC030 | Simulation Studies of Correlated Misalignments in the ILC Main Linac and the Influence of Ground Motion | 3044 |
|
||
|
Component misalignments are an important source of emittance dilution in the main linac of the International Linear Collider (ILC). The impact of static uncorrelated alignment errors has been widely studied with various simulation codes and several beam based alignment algorithms. For a realistic scenario one has to take into account that the survey and alignment process will introduce correlations between the component errors. In the present paper we study the performance of the Dispersion Matched Steering (DMS) technique for the case of such correlated misalignments. Different models for the correlations are investigated including a proposed alignment strategy for the ILC main linac* which has been implemented into the Merlin C++ library**. In addition to the initial static errors, dynamic errors due to ground motion will produce an emittance growth with time. For this case we have also investigated the stability of DMS tuning over time.
* Kiyoshi Kubo, private communication |
||
| THPC032 | Vertical Beam Size Reduction via Compensation of Residual Transverse Coupling | 3047 |
|
||
| The Brazilian Synchrotron Light Source (LNLS) is currently constructing a beamline which will make use of the radiation produced by the EPU installed in the storage ring (SR) in 2007. Various force tasks have been triggered by this new beamline in order to achieve required beam properties and stability. One of these tasks has to do with reducing the SR's vertical beam size at the straight section where the EPU is located, hence improving the radiation brilliance from the EPU. This report will describe our recent efforts in understanding and controlling what residual effects there are in the ring that dominate the ring's vertical beam size. In particular, we study the effects of residual coupling perturbations on the beam size through the transfer matrix formalism which, we argue, is the most appropriate. A beam model including transverse linear coupling is validated with measured closed orbit response functions. By Analyzing this model we are able to propose new skew quadrupole elements to the SR that might reduce the vertical beam size at the EPU section and we can infer the validity of results with a pinhole beam imaging system which we have available in our diagnostic beamline. | ||
| THPC033 | Global Optimization of the Magnetic Lattice Using Genetic Algoritihms | 3050 |
|
||
| The traditional process of designing and tuning the magnetic lattice of a particle storage ring lattice to produce certain desired properties is not straight forward. Often solutions are found through trial and error and it is not clear that the solutions are close to optimal. In this paper we employ a technique we call GLASS (GLobal scan of All Stable Settings) that allows us to rapidly scan and find all possible stable modes and then characterize their associated properties. In this paper we illustrate how the GLASS technique gives a global and comprehensive vision of the capabilities of the lattice. In a sense, GLASS functions as a lattice observatory clearly displaying all possibilities. The power of the GLASS technique is that it is very fast and comprehensive. There is no fitting involved. It gives the lattice designer clear guidance as to where to look for interesting operational points. We demonstrate the technique by applying it to two existing storage ring lattices - the triple bend achromat of the ALS and the double bend achromat of CAMD. We extend the analysis to more complex lattices using multiobjective evolutionary analysis. | ||
| THPC034 | Correction the Round Beam Lattice of VEPP-2000 Collider Using Orbit Response Technique | 3053 |
|
||
| Round colliding beams option in VEPP-2000 puts a number of strict requirements on the collider lattice. Orbit Response Matrix (ORM) technique is a versatile tool for lattice analysis and correction. For linear optical function study and correction, the orbit response to the dipole correctors is collected and processed, while for the orbit correction the quadrupole trimming is used. Theoretical and experimental responses of closed orbit on the same perturbations are compared to determine the most probable deviations of chosen parameters from its project values. | ||
| THPC036 | Model Based Orbit Correction in a Diagnostics Deficient Region | 3056 |
|
||
| A method is presented for an orbit correction in a region where the number of beam position monitors is much less than the number of possible trajectory distortions points (quads). The method was developed for the Coupled Cavities Linac (CCL) part of the Spallation Neutron Source (SNS) linac. The orbit correction is very important in this region to minimize losses and activation, but the usual orbit correction method did not work here. The new method is based on a usage of a realistic online model. The parameters of the model were defined by multidimensional fitting procedure with a substantial array of measured trajectories in CCL. The procedure of parameters finding, model, and results are discussed. | ||
| THPC037 | Studies of Orthogonal Bumps for ILC Main Linac | 3059 |
|
||
| To preserve small vertical emittance of the beam in ILC main linac a few beam-based alignment techniques were proposed and studied in recent years. Dispersion and wakefield bumps are one of the effective tool for final tuning of the machine. One of the modifications of bumps is so called orthogonal (or SVD) bumps, proposed for CLIC. In paper we present study of orthogonal bumps performances for final alignment of the ILC main linac. | ||
| THPC038 | Beam Dynamic Simulations of the New Polarized Electron Injector of the S-DALINAC | 3062 |
|
||
| Aiming at an extension of the experimental possibilities at the Superconducting Darmstadt electron linear accelerator S-DALINAC, a polarized gun is going to be constructed at the moment. The new injector will be able to supply polarized electrons with kinetic energy in the 100 keV range and should add to the present unpolarized thermionic 250 keV source. The design requirements include a polarization degree of at least 80%, a mean current intensity of 60 μA and a 3 GHz cw time structure. The gun part is simulated in CST MAFIA whereas subsequent beam dynamics simulations are performed in V-Code. Initial conditions for the V-Code’s moment approach are extracted from the CST MAFIA simulations. The injector consists of short triplets, an alpha magnet, a Wien filter, a Mott polarimeter, a chopper/prebuncher system and beam diagnostic elements. For the simulations, the 3D electromagnetic fields of the beam line elements are used by means of a Taylor series expansion of variable order. All components except the chopper and a collimator is represented in the simulations. Recent beam dynamic results will be presented. | ||
| THPC040 | Comparative Analysis of Different Kinds of Effects in the Nanoprobe | 3065 |
|
||
| Different kinds of parasitic effects in a nanoprobe are investigated. In this paper we consider the focusing system of nanoprobe, which consists of quadrupole lenses, but some results are also discussed for solenoids as focusing elements. The results of the similar analysis make it possible to design a number of goal-seeking strategies for selecting the optimal beam line structure. The influence of different linear and nonlinear aberrations is investigated using analytical and numerical methods and tools. For this purpose we present the beam line propagator based on a matrix formalism for Lie algebraic tools. In conclusion, some results of fulfilled modeling are analyzed. | ||
| THPC041 | Closed Orbit Correction and Orbit Stabilization Control for TPS Storage Ring | 3068 |
|
||
| TPS is a 3 GeV synchrotron storage ring proposed in Taiwan. The designed natural emittance with slightly positive dispersion in the straight sections is less than 2 nm-rad. With 1% emittance coupling, the beam size in horizontal and vertical plane are 120/5 micron in the short straight sections, respectively. The beam position stability requirements are 10% of the beam sizes, i.e., 12/0.5 micron in the horizontal/vertical plane. The closed orbit distortions due to alignment displacement and magnetic field errors are simulated. The distribution of beam position monitors and the location of slow and fast correctors are proposed and the level of achievement is shown. | ||
| THPC042 | Uncoupled Achromatic Tilted S-bend | 3071 |
|
||
|
A particular section of one of the electron beam transport lines, to be used in the e-cooling project* of the Relativistic Heavy Ion Collider (RHIC), is constrained to bend the beam simultaneously in both the horizontal and vertically planes and also be achromatic in both planes. The simultaneous horizontal and vertical achromatic bend is accomplished by rotating, about the longitudinal axis of the beam, the dipole and quadrupole elements of this section of the line. However such a rotation of the magnetic elements may couple the transported beam through the first order beam transfer matrix (linear coupling). In this paper we investigate for a sufficient condition, that the first order transport matrix (R-matrix) can satisfy, under which such a section of a beam transfer line is both achromatic and also constrains the beam at the exit of the line to emerge linearly uncoupled. We also provide a complete solution for the beam optics, of this part of the beam transfer line, which satisfies achromaticity and no first order beam coupling.
*htpp://www.bnl.gov/cad/eRhic/Documents/AD_Position_Paper_2007.pdf |
||
| THPC044 | Accurate Calculation of Higher Order Momentum Compaction Factor in a Small Ring | 3074 |
|
||
| The key issues to obtain short beam bunch in storage ring is to lowering momentum compaction factor. When the linear momentum compaction factor is small, higher order momentum compaction factor can produce significant effects in the longitudinal beam dynamics. In the small storage ring, higher order momentum comaction factor is determined not only by sextupoles, and also by the fringe field of main magnets. In this paper, the higher order momentum factor formula including the effects of fringe field is deduced. As a example, the momentum compaction factor of HLS storage ring was calculated. | ||
| THPC045 | Beam Uniformization System Using Multipole Magnets at the JAEA AVF Cyclotron | 3077 |
|
||
|
It has been known that uniformization of a beam with a Gaussian profile is possible utilizing odd-order nonlinear forces*. Here, we investigate uniformization of the transverse beam profile using nonlinear-focusing forces produced by multipole magnets in detail. We show that it is possible to uniformize an asymmetric beam as well as a Gaussian beam utilizing the odd and even-order nonlinear forces in combination**. It enables us to perform high-uniformity irradiation at a constant particle fluence rate over the whole area of a large target. A research and development study of the beam uniformization system composed of sextupole and octupole magnets is now in progress at the JAEA AVF cyclotron facility. Some results of preliminary experiments on beam uniformization are also reported.
*P. F. Meads, Jr., IEEE Trans. Nucl. Sci. 30, 2838 (1983). |
||
| THPC046 | Heating Rate of Highly Space-charge-dominated Ion Beams in a Storage Ring | 3080 |
|
||
|
We investigate the heating process of highly space-charge-dominated ion beams in a storage ring, using the molecular dynamics simulation technique. To evaluate the heating rate over the whole temperature range, we start from an ultra-low-emittance state where the beam is Coulomb crystallized, apply perturbation to it, and follow the emittance evolution. When the ring lattice is properly designed, the heating rate is quite low at ultralow temperature because random Coulomb collisions are suppressed*. It gradually increases after the ordered state is destroyed by perturbation, and comes to a peak when the beam reaches a liquid phase. The dependence of the heating behavior on the beam line density and betatron tune is explored systematically. The effect of lattice imperfection on the stability of crystalline beams is also confirmed.
*J. Wei and A. M. Sessler, EPAC'96, p.1179. |
||
| THPC047 | Studies of Losses During Continuous Transfer Extraction at the CERN proton Synchrotron | 3083 |
|
||
| Proton beams can be extracted from the CERN-PS at 14 GeV/c on five turns, using a technique called Continuous Transfer (CT). In this case, large losses due to particles scattered by an electrostatic septum used to slice the beam on five turns are observed in straight sections where the machine aperture is large enough to accommodate the circulating beam without any loss. These losses limit the maximum intensity deliverable to the SPS, like for the CERN to Gran Sasso (CNGS) neutrino program, because of the large irradiation of the site outside the PS tunnel and at the CERN fence. New simulation tools for a parametric study have been developed to improve the understanding of the observed loss pattern. A proposed solution to displace the losses in less critical section of the machine has been simulated and implemented in the CERN-PS. Simulations and experimental results of the loss study and reduction are presented. | ||
| THPC048 | Study of Beam Losses at Transition Crossing at the CERN PS | 3086 |
|
||
| A series of studies has been carried out to understand and alleviate the beam losses in the CERN PS proton Synchrotron. In particular, losses appear at transition crossing during the pulsing of special quadrupoles used to create a gamma jump scheme and which causes a large optics and orbit distortion. After a brief summary of the gamma jump scheme at the PS, experimental and simulation results about the loss studies and reduction are presented. | ||
| THPC049 | Progress in the Beam Preparation for the Multi-turn Extraction at the CERN Proton Synchrotron | 3089 |
|
||
| A new type of extraction based on beam trapping inside stable islands in the horizontal phase space will become operational during 2008 at the CERN Proton Synchrotron. A series of beam experiments was carried out to prove loss-less capture with high intensity and multi-bunched beams, up to 1500·1010 protons per pulse, in preparation of the extraction commissioning. These fundamental steps for the new Multi-turn Extraction are presented and discussed in details. | ||
| THPC050 | Experimental Evidence of Beam Trapping with One-third and One-fifth Resonance Crossing | 3092 |
|
||
| Beam trapping in stable islands of the horizontal phase space generated by non-linear magnetic fields is realized by means of a given tune variation so to cross a resonance of order n. Whenever the resonance is stable, n+1 beamlets are created whereas if the resonance is unstable, the beam is split in n parts. Experiments at the CERN Proton Synchrotron showed protons trapped in stable islands while crossing the one-third and one-fifth resonance with the creation of 3 and 6 stable beamlets, respectively. The results are presented and discussed in details. | ||
| THPC051 | Adiabaticity and Reversibility Studies for Beam Splitting Using Stable Resonances | 3095 |
|
||
| At the CERN Proton Synchrotron, a series of beam experiments proved beam splitting by crossing the one-fourth resonance. Depending on the speed at which the horizontal resonance is crossed, the splitting process is more or less adiabatic, and a different fraction of the initial beam is trapped in the islands. Experiments prove that when the trapping process is reversed and the islands merged together, the final distribution features thick tails. The beam population in such tails is correlated to the speed of the resonance crossing and to the fraction of the beam trapped in the stable islands. Experiments, simulations, and possible theoretical explanations are discussed. | ||
| THPC052 | Beam Losses and Collimation Considerations for PS2 | 3098 |
|
||
| The high intensity beams with different emittances foreseen to be delivered by the PS2, an upgraded version of the actual CERN Proton Synchrotron, require strict control of beam losses in order to protect the machine components and enable their hands-on maintenance. Beam loss simulations based on dedicated numerical tools are undertaken for a variety of PS2 beams and for different loss mechanisms, along the whole accelerating cycle. In this respect, the design of a collimation system is presented and its performance is compared within different lattice options. | ||
| THPC053 | Turn-by-turn Data Analysis at the Diamond Storage Ring | 3101 |
|
||
| The Diamond Storage Ring has been recently equipped with a set of two pinger magnets that can excite betatron oscillations to large amplitudes in both planes of motion. In conjunction with the turn-by-turn capabilities available at all BPMs, the system provides a powerful diagnostic tools for the characterisation of the linear and non-linear beam dynamics of the electron beam in the storage ring. We report the first results on the application of the Frequency Map Analysis and the measurement of the resonant driving terms at the Diamond Storage Ring. | ||
| THPC054 | Transportation of Decay Products in the Beta-beam Decay Ring | 3104 |
|
||
| The principle of the neutrino production in the beta-beams relies on the beta-decay of the radioactive ions Neon 18 and Helium 6 in a storage ring. After decaying, the daughter particles have their magnetic rigidity significantly changed (-33% for Helium and +11% for Neon). Therefore, the decay products will be quickly lost on the walls of the decay ring after entering a dipole. Absorbers have been inserted in the decay ring in order to collect most decay products. Their optimization implies to calculate the trajectories of the decay products in the dipoles for very large momentum differences with a good accuracy. For pure dipoles without fringe field as in the decay ring, an analytic treatment can be used to simulate the transportation. It is then possible to obtain the equivalent dipole which gives the beam sizes of the daughter particles. In a first part, we will describe the analytic treatment of the central trajectory and the motion of the ions around. In a second part, we will compare this treatment with the one with matrices for different orders in the case of the beta-beam decay ring. | ||
| THPC055 | Dynamic Aperture Studies for PETRA III Including Magnet Imperfections | 3107 |
|
||
| PETRA III is a 3rd generation synchrotron radiation light source. Efficient injection in the top up mode requires a dynamic aperture of 30 mmmrad or larger, while a 2 hour Touschek lifetime needs an average momentum aperture of around 1.5 %. We present studies on the impact of recently measured magnet imperfections on the available dynamic aperture. To this end, tracking simulations have been performed including the effects of measured multipole errors of lattice magnets and of 20 four-meters-long damping wigglers. | ||
| THPC056 | Stability Change of Fourth-order Resonance with Application to Multi-turn Extraction Schemes | 3110 |
|
||
| Recently, a novel multi-turn extraction scheme was proposed, based on particle trapping inside stable resonances. Numerical simulations and experimental tests confirmed the feasibility of such a scheme for low order resonances. While the 3rd order resonance is generically unstable and those higher than 4th order are generically stable, the 4th order resonance can be either stable or unstable depending on the details of the system under consideration. By means of the normal form approach a general formula to control the stability of the 4th order resonance is derived. Numerical simulations confirm the analytical results and show that by crossing the unstable 4th order resonance the region around the centre of phase space is depleted and particles are trapped only in the four stable islands. This indicates that a four-turn extraction could be envisaged based on this technique. | ||
| THPC057 | Field Interference of Magnets in the Large Acceptance Storage Ring CR of the Fair Project | 3113 |
|
||
| The large acceptance storage ring CR is planned to be used for accumulation and cooling of rare isotope and antiproton beams at the future FAIR accelerator facility. The huge apertures as well as the close arrangement of the dipoles and quadrupoles make overlapping between the end fields of the magnets unavoidable. In addition, corrector magnets are planned to be installed in the drift sections between the dipoles and quadrupoles for closed orbit corrections. The presence of additional iron can have a significant influence on the magnetic field distribution. This interference can lead to a reduction of the integral field quality decline that is undesirable since it can affect the beam dynamics. In this contribution we present the results of 3D magnetic field simulations performed using the OPERA computer code. The field maps were derived and further analyzed. The corresponding sets of multipole components were calculated and were then implemented into one of the codes for the beam dynamics calculations. The MAD code was used to calculate the dynamic aperture and to estimate the effect of the field interference on the beam dynamics of the ring. | ||
| THPC058 | High Order Super-periodic Structural Resonances | 3116 |
|
||
| High order super-periodic structural resonances, which arise from the study of SSRF lattice optimization, are found to have large effects on beam dynamics. The mechanism and feature of this kind of resonances are described in the text. The limit to beam dynamics of other light sources are also found from these resonances. | ||
| THPC059 | Studies of Wire Compensation and Beam-beam Interaction in RHIC | 3119 |
|
||
| Beam-beam interaction is one of the dominant source of emittance growth and luminosity lifetime deterioration. A current carrying wire has been proposed to compensate long-range beam-beam effects in the LHC and the principle is now being experimentally investigated at RHIC. In this paper, we use simulations to study the effectiveness of wire compensation based on tune footprints, diffusive apertures, and beam loss rates using a parallel weak-strong beam simulation code (BBSIM). In addition we extensively study the diffusion properties of RHIC beams for different beam and wire parameters. Beam-beam effects on emittance growth are investigated through the solution of the diffusion equation for the transverse action variables. | ||
| THPC060 | Spin Flip of Deuterons in COSY - Spink Tracking | 3122 |
|
||
|
The spin tracking code Spink, as recently overhauled*, has been used to study the deuteron spin resonances and spin flipping induced by a RF dipole and a RF solenoid. The modifications of the code followed extended discussions on the formalism used to model spin evolution in a synchrotron. The simulation shows a good agreement with published results of the measurements**.
*A. U. Luccio et al. See another contribution to this Conference. |
||
| THPC062 | Multi-Particle Weak-Strong Simulations of RHIC Head-on Beam-Beam Compensation | 3125 |
|
||
| An electron beam has been proposed in the Relativistic Heavy Ion Collider (RHIC) to compensate beam-beam effects in polarized proton collisions. This electron beam will collide head-on with the proton beam. Using the weak-strong beam-beam interaction model, we have carried out six-dimensional multiparticle simulations to investigate the effects of head-on beam-beam compensation. Beam lifetime, transverse emittances, and luminosity are calculated for cases with and without beam-beam compensation for up to 10 million turns. The migrations of particles between different actions and the beam spectrum are also calculated. | ||
| THPC063 | First Frequency Maps for Probing the Non-linear Dynamics of SOLEIL | 3128 |
|
||
| SOLEIL is a 2.75 GeV third generation synchrotron light source delivering photons to beam-lines since January 2007. With a 3.7 nm.rad horizontal emittance, its optics is based on a strong focusing lattice. Large on- and off-momentum apertures are required in order to provide good injection efficiency and as large as possible beam lifetime. It is then fundamental to be able to understand the limitations of these key figures. In order to probe the transverse non linear dynamics two pinger magnets have been installed into the injection straight section during last summer shutdown period. In this paper, their calibration will be described. Then first comparisons between modeled and real machine will be given for betatron tune shifts with amplitudes, and frequency maps. To end the non linear impact of insertion devices on beam dynamics will be discussed. | ||
| THPC064 | Use of LOCO at Synchrotron SOLEIL | 3131 |
|
||
| SOLEIL is a 354 m long 2.75 GeV third generation synchrotron light source delivering photons to beam-lines since January 2007. This paper will discuss in details the first attempts using LOCO code and problems encountered due to the storage ring lattice compactness. The introduction into the code of constraints on the quadrupole gradient variations gave tremendous improvements. The convergence is satisfactory, beta –beatings are reduced from 5% to below 1% RMS in both planes. Restoring the symmetry of the lattice enhanced the performances of the storage ring. In the last part, different ways of using LOCO as a powerful diagnostics tool will be given. | ||
| THPC065 | Orbit Stability Status and Improvement at SOLEIL | 3134 |
|
||
| SOLEIL is a 2.75 GeV third generation synchrotron light source delivering photons to beam-lines since January 2007. Stability of the beam-line source points is crucial for the user experiments. Typically this stability has to be below one tenth of the transverse beam sizes. This is challenging especially in the vertical plane leading to sub-micrometer values. This paper will describe the position stability achieved today without and with the slow orbit feedback. Impact of different noise sources and present limitations will be described. To end an improvement strategy will be given for short and medium terms. | ||
| THPC066 | Measuring Ring Nonlinear Components via Induced Linear "Feed-down" | 3137 |
|
||
| The knowledge of the distribution in a ring of the non-linear components is important for the resonance compensation. We present a method to measure the lattice nonlinear components based on the non-linear tune response to a locally controlled closed orbit deformation. A test of this concept in the SIS18 synchrotron is presented and discussed. | ||
| THPC067 | ALBA Dynamic Aperture Optimization | 3140 |
|
||
| The lattice of ALBA, the 3 GeV synchrotron light source in Spain, provides extremely low emittance of the beam. It is known that such lattices require strong sextupole magnets to compensate natural chromaticities. The paper describes strategy and results of the ALBA dynamic aperture optimization including both tune point selecting and sextupoles arrangement to increase the DA size. | ||
| THPC068 | Effect of Magnetic Multipoles on the ALBA Dynamic | 3143 |
|
||
| For modern synchrotron light sources the main limitation of dynamic aperture is due to the strong chromatic sextupoles. However, small multipole errors in magnetic elements can reduce the original dynamic aperture by generating high order resonances at the aperture boundary. For the ALBA synchrotron light source a dynamic aperture in the presence of magnetic multipoles in the main magnets was simulated by tracking code. Both systematic and random magnetic errors were taken into account. In this paper we report on the results of our considerations. | ||
| THPC069 | Impact of Magnet Misalignment in an ERL for Electron Cooling in RHIC | 3146 |
|
||
| The MaryLie/IMPACT code was recently upgraded to include magnet errors. We have used the code to assess the sensitivity of final emittance of an ERL injector for the proposed RHIC electron cooler to up-stream magnetic element misalignments. This calculation will help determine the error tolerance for the construction of the ERL. | ||
| THPC070 | Symmetry Restoration of the SPring-8 Storage Ring by Counter-sextupole Magnets | 3149 |
|
||
| In the SPring-8 storage ring there are four magnet-free long straight sections of about 30m. These were realized in 2000 by locally rearranging quadrupole and sextupole magnets. In modifying the optics we took care of the periodicity of cell structure, especially of sextupole field distribution along the ring. To keep the periodicity high and hence the dynamic aperture large, we adopted a scheme in which "betatron phase matching" and "local chromaticity correction" are combined. In this scheme the dynamic aperture for on-momentum electrons is kept by the phase matching and that for off-momentum electrons is enlarged by the local chromaticity correction with weak sextupoles (SL). After modifying the lattice, we tried to recover the symmetry of the ring further and found that a harmful effect of nonlinear kick due to SL can be minimized by additional "counter-sextupole magnets" placed 180 degrees apart in horizontal betatron phase from SL. We installed such counter-sextupoles in every long straight sections and confirmed that the aperture was improved. In the paper we discuss these topics showing experimental data of injection efficiency, momentum acceptance, etc. | ||
| THPC072 | Impact of Betatron Motion on Path Lengthening and Momentum Aperture in a Storage Ring | 3152 |
|
||
| The amplitude of the betatron motion in an electron storage ring becomes large in some cases, e.g. Touschek scattered electrons or injected beam. Then we cannot ignore the effect of a finite amplitude of betatron motion on the beam dynamics. The path lengthening of the central trajectory of betatron motion is one of the most serious manifestations of such an influence. Due to the synchrotron motion, the variation of the path length is converted into the energy deviation, so that the betatron motion gives the impact on the momentum aperture in the storage ring. In this paper the path lengthening by a finite amplitude betatron motion is calculated by means of the canonical perturbation method. The derived formula for the path lengthening is simply represented by the product of the chromaticity and the invariant amplitude. Using the formula, we discuss the impact of the betatron motion on momentum aperture in a Touschek effect. | ||
| THPC073 | Measurement of Resonance Driving Terms in the ATF Damping Ring | 3155 |
|
||
| The measurement of resonance driving terms in the Damping Ring of the Accelerator Test Facility in KEK could help finding possible machine imperfections and even to optimize single particle stability through the minimization of non-linearities. The first experimental attempts of this enterprise are reported in this note. | ||
| THPC074 | Observation of Coherent Oscillations of Colliding Bunches at the Tevatron | 3158 |
|
||
| Commissioning of the new digital tune monitor (DTM) at the Tevatron made it possible to observe vertical dipole oscillations of individual bunches at any time during an HEP store. Since all the bunches have significantly different collision conditions, this device provides vast possibilities for investigation of coherent beam-beam effects. We present theoretical model and experimental observations of coherent beam-beam modes. Analysis of the DTM data and its agreement with theory are discussed. | ||
| THPC076 | Closed Orbit Correction and Sextupole Compensation Schemes for Normal-conducting HESR | 3161 |
|
||
| The High Energy Storage Ring (HESR) will be part of the future Facility for Antiproton and Ion Research (FAIR) located at GSI in Darmstadt, Germany. The HESR will be operated with antiprotons in the momentum range from 1.5 to 15 GeV/c, which makes a long beam life time and a minimum of particle losses crucial. This and the demanding requirements of the PANDA experiment lead to the necessity of a good orbit correction and an effective multipole compensation. We developed a closed orbit correction scheme and tested it with Monte Carlo simulations. We assigned different sets of angular and spatial errors to all elements (magnets, bpms, etc.) within the lattice of the HESR. For correction we applied the orbit response matrix method. We carried out investigations concerning higher-order multipoles and created a scheme for chromaticity correction and compensation of arising resonances utilising analytic formulae and dynamic aperture calculations. In this presentation we give an overview of the correction and compensation schemes and of the corresponding results. | ||
| THPC077 | Transportation Channel with Uniform Electron Distribution for the Kharkov Neutron Source based on Subcritical Assembly Driven with Linear Accelerator | 3164 |
|
||
| Electron beam transportation channel from linear accelerator to the neutron target of NSC KIPT neutron source should provide uniform distribution of electrons on target surface to prevent overheating of the target and reduce thermal stress. In the presented channel the method of uniform beam distribution formation with linear focusing elements and nonlinear focusing elements (octupole magnets) we used. Linear focusing elements were used to provide particle transportation through the channel without losses and to form required beam sizes at the target. Nonlinear focusing elements were used to modulate transverse velocity of peripheral particles. As a result the uniform electron beam of rectangular shape can be formed at the target. In the report the main principles of transportation channel design and results of calculations for NSC KIPT neutron source based on subcritical assembly driven by electron accelerator are presented. Lattice and parameters of focusing elements are presented. Calculation results show that proposed transportation channel lattice can provide uniform beam of rectangular shape with sizes 66x66 mm. | ||
| THPC078 | Injection Scheme of X-rays Source NESTOR | 3167 |
|
||
| In the paper the injection scheme of the X-ray source NESTOR based on the compact storage ring and Compton scattering is described. It is supposed to inject electron beam through fringe fields of a bending magnet. For final beam deflection electrical inflector on the running wave will be used. The layout of the injection scheme and elements characteristics are presented. The results of simulations of electron beam motion through 3-d fields of electro-magnetic devices of the injection channel are presented. | ||
| THPC080 | The VEPP-4M Dynamic Aperture Determination with Beam-beam Effects | 3170 |
|
||
| To determine experimentally the particle stable area under the influence of beam-beam effects in the electron-positron collider VEPP-4M we measure the beam lifetime with high accuracy as a function of moving aperture. The measurement is performed by a photodiode installed in the collider diagnostic beam line. The experimental setup and the measurement results are described. Comparison with the tracking simulation is presented. | ||
| THPC081 | RF Wire Compensator of Long-range Beam-beam Effects | 3173 |
|
||
| The dynamic aperture of the proton beam circulating in the Large Hadron Collider (LHC) is expected to be limited by up to 120 long-range beam-beam encounters. In order to perfectly compensate the LHC long-range beam-beam effect for nominal as well as for so-called 'PACMAN' bunches, i.e. bunches at the start or end of a bunch train, the wire compensator strength should be adjusted for each bunch individually. Here an RF-based compensator is proposed as a practical solution for the PACMAN compensation. We show that this approach also allows relaxing the power and precision requirements compared with those of a pulsed DC device, to a level within the state-of-the-art of RF technology. Furthermore it allows the use of a passive circulator in the tunnel close to the beam and thus a significantly reduction of the transmission line length and of the resulting multiple reflection issues. Simulations, issues related to RF phase noise and first experimental results from laboratory models as well as from a wire-compensator prototype installed in the CERN Super Proton Synchrotron (SPS) are presented. | ||
| THPC082 | Wire Excitation Experiments in the CERN SPS | 3176 |
|
||
| In order to study the effect of long range interaction and its wire compensation experimentally, current carrying wires are installed in the CERN Super Proton Synchrotron (SPS). In this paper we summarize the main results of the 2007 wire excitation results at 26, 37 and 55 GeV including wire-current-, beam-wire distance and chromaticity scans. A strong dependence on the chromaticity and indications of a threshold effect at 37 and 55 GeV was found. The results are compared to simulation, to a simple analytic scaling law and to experimental results from RHIC. Wire-driven resonances have been observed through the Fourier spectrum of experimental BPM data and compared to simulations. | ||
| THPC083 | Simulation Studies of Space-charge Effects in the LENS Nonlinear Transport Lines | 3179 |
|
||
| The upgraded IUCF LENS beamline is designed to deliver a square shaped 13 MeV proton beam at 25 mA with a relatively uniform density using two octupole magnets for nonlinear focusing in both transverse directions. The space-charge effects in the LENS beamline (without nonlinear focusing) can vary the beam profile by roughly 8%-13% compared to a zero current beam. In this paper, we show the results of simulation studies of the LENS beamline which incorporate the effects of space-charge, as well as, nonlinear focusing from the octupole magnets. The simulations utilize self-consistent methods for computing the space-charge fields, since the beam density distribution can be nonlinear. We also show simulation results for beam currents in excess of 25 mA, which may be useful for future upgrades of LENS. | ||
| THPC084 | Studies of Electromagnetic Space-charge Fields in RF Photocathode Guns | 3182 |
|
||
|
In high-brightness rf photocathode guns, the effects of space-charge can be important. In an effort to accurately simulate the effects of these space-charge fields without the presence of numerical grid dispersion, a Green’s function based code called IRPSS (Indiana Rf Photocathode Source Simulator) was developed*. In this paper, we show the results of numerical simulations of the Argonne Wakefield Accelerator photocathode gun using IRPSS, and compare them with the results of an electrostatic based simulation code. In addition, we show how electromagnetic space-charge fields can affect the designs of photocathode gun magnetic focusing schemes, such as emittance compensation. We will also show how a multipole moment method can be effectively utilized to compute the reflections of electromagnetic space-charge fields due to irises in photocathode guns.
*M. Hess, C. S. Park, and D. Bolton. Phys. Rev. ST Accel. Beams 10, 054201 (2007). |
||
| THPC085 | VORPAL Simulations Relevant to Coherent Electron Cooling | 3185 |
|
||
|
Coherent electron cooling (CEC)* combines the best features of electron cooling and stochastic cooling, via free-electron laser technology**, to offer the possibility of cooling high-energy hadron beams with order-of-magnitude shorter cooling times. Many technical difficulties must be resolved via full-scale 3D simulations, before the CEC concept can be validated experimentally. VORPAL is the ideal code for simulating the “modulator” and “kicker” regions, where the electron and hadron beams will co-propagate as in a conventional electron cooling section. Unlike previous VORPAL simulations*** of electron cooling physics, where dynamical friction on the ions was the key metric, it is the details of the electron density wake driven by each ion in the modulator section that must be understood, followed by strong amplification in the FEL. We present some initial simulation results. In particular, we compare the semi-analytic binary collision model with electrostatic particle-in-cell (PIC).
*Ya. S. Derbenev, COOL ’07 Proc. (2007). |
||
| THPC086 | Transverse Mismatch Oscillations of a Bunched Beam in Presence of Space Charge and External Nonlinearities | 3188 |
|
||
| The damping of transverse mismatch oscillations depends on the combined effect of space charge as well as external nonlinearities. Previous studies of this problem for high intensity beams in a synchrotron have not included the combined effect of synchrotron oscillation and external nonlinearities on mismatch. In this paper we explore by 2.5D particle in cell simulations the effect on emittance growth, halo and beam loss caused by space charge, synchrotron oscillation and external nonlinearities. Different tunes are considered in order to understand the importance of external nonlinearities as function of the distance of the working point from the resonance condition. | ||
| THPC087 | Electron Traps and Advanced Turbulence Diagnostic | 3191 |
|
||
| In the electron trap Eltrap both trapped and propagating beam (along the magnetic field axis z) up to 20 kV can be studied. Beam structures in x and y (transverse plane) were successfully detected. Main diagnostic and axial control of instabilities was based on electrostatic. The addition of an external electron source, controlled by a laser, makes ns electron bunches now possible. A system to dump the electron beam off axis is also described. Faster diagnostic and control methods can be tested. In particular, Thompson scattering diagnostic of beam structures can be tested, considering that a wavelength shift (even if modest) is present. Nonlinear dynamics modeling of injection process is also described. | ||
| THPC088 | Beam Dynamics Simulation of Superconducting HWR Option for the IFMIF Linac | 3194 |
|
||
| One of the requirements of the International Fusion Materials Irradiation Facility (IFMIF) is a 250 mA, 40 MeV cw deuteron beam provided by two 125 mA linacs. In this paper, a design based on superconducting half-wave resonators (HWR) for the 5 to 40 MeV section of the IFMIF driver accelerator is presented. Multi particle beam dynamics simulations have been performed in order to validate the linac design in such a high charge space regime. A Monte Carlo error analysis has been carried out to study the effects of misalignments or field variations. The results of the simulations are presented and the final specifications of the HWR linac are summarized. | ||
| THPC089 | Electron-cloud Intrabunch Density Modulation | 3197 |
|
||
| During the passage of a proton bunch through an electron cloud a complicated electron density modulation arises, with characteristic ring and stripe patterns of high density regions that move radially outward along the bunch. We present simulation results as well as a simple analytical model to reveal the morphology and main features of this phenomenon as well as its dependence on key parameters like bunch length, beam size, and bunch charge. | ||
| THPC091 | Experimental Study of an Intense Relativistic Helical Electron Beam Formed with Interception of the Electrons Reflected from the Magnetic Mirror | 3200 |
|
||
| A new method of formation of pulsed intense relativistic helical electron beams (HEBs) for gyroresonant devices has been presented. The method is aimed at the increase of pitch-factor and the reduction of HEB velocity spread and is intended for use in the formation systems of laminar HEBs characterized by low influence of space charge on their parameters. The method is based on the operation of a special diaphragm located at one of minima of trajectories at the beginning of the transportation channel. The diaphragm diameter is chosen so that the electrons with the lowest oscillatory velocities cannot bend round the diaphragm and settle on it. The rest electrons pass by moving in the increasing magnetic field. Then, the electrons with the greatest oscillatory velocities are adiabatically reflected from the magnetic mirror between the electron gun and the transportation channel and settle on the back of the same diaphragm. Reduction of space charge of the reflected electrons has led to the increase of HEB pitch-factor (HEBs have been formed with the record of pitch-factors exceeding 2), while the accumulation of space charge worsens the HEB provoking modulation of formed HEB current. | ||
| THPC097 | A Full Analytical Method to Determine Equilibrium Quantities of Mismatched Charged Particle Beams evolving in Linear Channels | 3203 |
|
||
| The focus of this work is to show a full analytical expression to determine relevant equilibrium quantities of a magnetically focused and high-intensity charged particle beam when evolving in a linear channel. Through the current approach, some intermediate steps of our original hybrid model which have to be solved numerically now can be eliminated, leading to the obtainment of a full analytical expression. This expression relates initial beam parameters with those obtained at equilibrium, allowing that the fraction of halo particles f can be evaluated. As a consequence, through the developed model, beam quantities like the envelope and emittance can be naturally determined. This is important in the accelerator engineering, since halo characteristics is a factor to be considered in the design of its confinement structure. For validation, full self-consistent N-particle beam numerical simulations have been carried out and its results compared with the predictions supplied by the full analytical model. The agreement is shown to be nice as with the simulations as with the hybrid numerical-analytical version of the model. | ||
| THPC098 | Halo characterization of initially mismatched beams through phase-space modeling | 3206 |
|
||
| This work discusses a method of characterizing the beam particles with just some assumptions about the entire beam phase-space topology. At equilibrium, the beam phase-space can be recognized as composed by almost two distinct regions: a thin horizontal branch over the r axis that is populated by the core particles and a curve branch in the dr/ds x r plane, which is populated by the halo particles. Since these regions have a regular shape, then it is readily possible to convert them to an analytical expression. Two distinct shapes have been employed (circular and elliptical) to model the beam halo branch. With this, all usual initial beam mismatch values are covered with accuracy to determine the beam envelope and emittance at equilibrium. Full self-consistent N-particle beam simulations have been carried out and its results compared with the ones obtained with the model. Results agreed nice for all analyzed mismatch cases. | ||
| THPC100 | Collisionless Relaxation in the Transport of Space Charge Dominated Beams | 3209 |
|
||
|
Relaxation to a final stationary state of particles interacting through long-range forces, such as Coulomb, is intrinsically different than that of systems with short-range interactions. While in the latter case it is known that the interparticle collisions drive the system to an equilibrium Maxwell-Boltzmann distribution, in the former case, the collision duration time diverges and the state of thermodynamic equilibrium is never reached. In this paper, a theory is presented which allows to quantitatively predict the final stationary state achieved by a transported space-charge dominated beam during a process of collisionless relaxation*. It is shown that a fully matched beam relaxes to a Fermi-Dirac distribution. However, when a mismatch is present and the beam oscillates, halo formation leads to a phase separation. The theory developed allows to quantitatively predict both the density and the velocity distributions in the final stationary state, including the halo.
* Y. Levin, R. Pakter, and T. N. Teles, Phys. Rev. Lett., 100, 040604 (2008). |
||
| THPC101 | Transverse Schottky Noise and Beam Transfer Functions with Space Charge | 3212 |
|
||
| The heavy ion synchrotron SIS18 will serve as booster for the synchrotron SIS100 to be built as part of the Facility for Antiproton and Ion Research (FAIR). As such the SIS18 should accelerate ion beams with a factor of 10-100 higher intensity, compared to the present performance. Beams of such intensities may suffer instabilities due to collective effects. Particularly at injection-energy space charge and the resistive wall impedance will affect the beam remarkably. Experiments for the investigation of direct space charge were performed in SIS18. Transverse Schottky signals and beam transfer functions (BTF) of coasting ion beams affected by space charge were measured. A distortion of the Schottky bands and BTF was observed and compared to a simple model allowing for linear space charge. The model reproduced the deformation and yielded parameters of the beam. | ||
| THPC102 | Image Simulations on the ISIS Synchrotron | 3215 |
|
||
| ISIS is the spallation neutron source at the Rutherford Appleton Laboratory in the UK. Operation centres on a loss-limited 50 Hz proton synchrotron, which accelerates ~3·1013 ppp from 70 to 800 MeV, corresponding to mean beam powers of 0.2 MW. A significant proportion of beam loss is attributable to space charge effects. One such effect is the image field which forms in the beam pipe. Off-centre beams resulting from closed orbit errors generate fields, which can perturb the beam and cause loss. Of particular interest on ISIS is the rectangular, varying aperture, vacuum vessel, as compared with the more usual constant aperture circular or elliptical geometries. A new 2D space charge code, Set, was developed to study these effects. The code simulates the effects of space charge using a 2D particle-in-cell model of the beam distribution, including an appropriate treatment of the rectangular beam pipe, and details of the ISIS lattice. The effects of images on closed orbits, driving terms, and the evolution of beam distributions at ISIS operational intensities were explored. | ||
| THPC103 | Wave Breaking and Test Particle Dynamics in Inhomogeneous Beams | 3218 |
|
||
| This work analyzes the dynamics of inhomogeneous, magnetically focused high-intensity beams of charged particles. While for homogeneous beams the whole system oscillates with a single frequency, any inhomogeneity leads to propagating transverse density waves which eventually result in a singular density build up, causing wave breaking and jet formation. Wave breaking is shown to relax the mismatched beam and we make use of Lynden-Bell's theory of violent relaxation to estimate characteristics of the relaxed state. | ||
| THPC104 | Optical Diagnostic on Gabor Plasma Lenses | 3221 |
|
||
| Gabor lenses have been built and successfully been used for the focussing of particle beams. In the case of a positive ion beam the space charge of the confined electron cloud may cause an over compensation of the ion beam space charge force and consequently focus the beam. The nonneutral plasma (NNP) is influenced by the external fields and its current state can be determined by the beam emittance growth. Experiments using a high field Gabor lens have shown a correlation between the thermalization of the enclosed electron cloud and the focussing quality. A three segmented Gabor lens was constructed recently for a more detailed investigation of the plasma parameters as a function of the external fields. The commissioning of the lens has been finished successfully and the light emitted by the interaction between the electron cloud and the residual gas has been observed. In a next step the experiments will concentrate on the spectral analyses of the emitted light to evaluate the temperature and density distribution of the confined NNP. Experimental results will be presented in comparison with numerical simulation. | ||
| THPC105 | Self-consistent Transverse Dynamics and Interbunch Energy Exchange in Dielectric Loaded Wakefield Accelerating Structures | 3224 |
|
||
| The self-consistent transverse dynamics of high current relativistic electron beams used for generating wakefields in dielectric loaded structures is investigated. The primary application of this work is to multi-bunch wakefield acceleration. The maximum distance the high current beam can travel through the structure in the absence of focusing without experiencing beam breakup and the energy transferred to the accelerated electron bunch will be presented. We consider both ramped and uniform charge distributions in the sequence of high current drive bunches. The ramped drive charge distribution is compared to the case of a uniform charge distribution in terms of the requirements for the beam focusing system and the effectiveness of the energy transfer to the accelerated electron bunch. | ||
| THPC107 | Beam Dynamical Issues of the KEK All-ion Accelerator | 3227 |
|
||
|
R&D works to realize an all-ion accelerator (AIA)* capable of accelerating all species of ions with any possible charge state, based on the induction synchrotron concept, which was demonstrated using the KEK 12 GeV-PS in 2006**, are going on at KEK. The KEK AIA, which is a modification of the existing KEK 500 MeV Booster Ring of a rapid cycle synchrotron, may be an injector-free accelerator. An ion beam from the high-voltage terminal of 200 kV is directly injected into the accelerator ring. Several key issues associated with the low energy injection must be addressed. Space-charge limited current due to a small relativistic b and a short life-time due to scattering with the residual molecules and eddy-current induced magnetic fields associated with guide-fields ramping from a low field level are among them. Careful considerations on them suggest that there are significant constrains on the operational performance and gives achievable beam parameters assuming the present parameters of the KEK AIA.
*K. Takayama, Y. Arakida, T. Iwashita, Y. S himosaki, T. Dixit, K. Torikai, J. of Appl. Phys. 101, 063304 (2007). |
||
| THPC108 | Observation of Bound States of Particles in the Storage Ring | 3230 |
|
||
| The deviation of n-particle state lifetime from the law T1/n, where T1 is a mean lifetime of one particle, in the storage ring was experimentally observed. Authors relate this deviation to interaction between the particles, conditioned by the fields directed in passive resonant devices of vacuum chamber of the storage ring. Depending on type of connection of the beam with passive resonant device, the interaction can be repulsive or attracting. The binding energy of a pair of particles for a case of their effective attraction is calculated. | ||
| THPC110 | Investigation of Helical Cooling Channel | 3233 |
|
||
|
A helical cooling channel (HCC) has been proposed to quickly reduce phase space of muon beams*. It is composed of solenoidal and helical coils to provide focusing and dispersion needed for the six-dimension cooling. A comprehensive investigation of the HCC is performed in presented work including theoretical analysis, particle tracking and Monte Carlo simulation. These results are also compared with the past simulation results** to confirm the helical cooling theory. Optimization of the channel and estimation of its ultimate performances are presented.
*Y. Derbenev and R. P. Johnson. PRSTAB 8, 041002 (2005). |
||
| THPC111 | Simulation ofμBunching Instability Regimes in the FLASH Bunch Compressors | 3236 |
|
||
| The bunch compression scheme for the European XFEL will operate in a regime in which, at least without additional energy spread introduced by a laser heater, theμbunching effect proposed in the literature may severely degrade the performance of the FEL. However, clear, unambiguous signals of theμbunching effect have not yet been seen neither in simulation nor experiment. The proposedμbunching effect amplifies initial current modulations by interleaved application of longitudinal collective energy kicks and transformations of energy modulation into current modulation in magnetic chicanes. In order to establish a parameter regime for experimental verification ofμbunching at the FLASH VUV-FEL at DESY, we have scanned the relevant part of the parameter space using a linear, quasi-analytic, noise-free gain-model and complemented this with particle tracking simulations. The tracking was performed using interleaved runs of ASTRA for acceleration modules and CSRTrack for the chicanes, automatically linked by the start-to-end simulation tool box Gluetrack. | ||
| THPC112 | KONUS Dynamics and H-mode DTL Structures for EUROTRANS and IFMIF | 3239 |
|
||
| During the last two decades, the combination of the KONUS beam dynamics and H-mode DTL structures has been developed as an efficient solution for accelerating low- and medium-energy proton and ion beams. EUROTRANS is a EUROpean Research Programme for the TRANSmutation of High Level Nuclear Waste in an Accelerator Driven System. IFMIF is a planned International Fusion Material Irradiation Facility to test materials for fusion reactors. For the driver linacs of both projects, two H-DTLs have been proposed to cover the energy ranges of 3–17MeV and 5–40MeV, respectively. The beam dynamics designs as well as the error studies of the H-DTLs are presented in this paper. | ||
| THPC113 | Feedback Damper System for Quadrupole Oscillations after Transition at RHIC | 3242 |
|
||
| The heavy ion beam at RHIC undergoes a strong quadrupole oscillations just after it crosses transition, which in turn leads to an increase in bunch length making rebucketing less effective. A feedback system was built to damp these quadrupole oscillations and in this paper the characteristics of the system and the results obtained are presented and discussed. | ||
| THPC114 | Design and Performance of a Prototype Digital Feedback System for the International Linear Collider Interaction Point | 3245 |
|
||
| We present the design and preliminary results of a prototype beam-based digital feedback system for the Interaction Point of the International Linear Collider. A custom analogue front-end processor, FPGA-based digital signal processing board, and kicker drive amplifier have been designed, built, and tested on the extraction line of the KEK Accelerator Test Facility (ATF). The system was measured to have a base latency of approximately 140 ns, increasing to approximately 148 ns with the inclusion of real-time charge normalisation. | ||
| THPC115 | Commissioning of SOLEIL Fast Orbit Feedback system | 3248 |
|
||
| The Fast Orbit Feedback system at SOLEIL is fully integrated into the BPM system equipped with Libera modules. Indeed, the correction algorithm has been embedded into the Libera FPGA which directly drives the power supplies of dedicated air coil correctors. The beam position measurements of the 120 BPMs are distributed around the storage ring by a dedicated network. Then, the correction is computed and applied at a rate of 10 kHz to 48 correctors installed over stainless-steel bellows, on each side of every straight section. The BPM system has been operational for some time. The fast orbit feedback system is in its commissioning phase. The design and first results of the latter are reported. | ||
| THPC116 | Commissioning of the iGp Feedback System at DAΦNE | 3251 |
|
||
| The iGp (Integrated Gigasample Processor) is an innovative digital bunch-by-bunch feedback system developed by a KEK/SLAC/INFN-LNF joint collaboration. The processing unit can sample at 500 MHz and compute the bunch-by-bunch output signal for up to 5000 bunches. The feedback firmware code is implemented inside just one FPGA (Field Programmable Gate Array) chip, a Xilinx Virtex-II. The FPGA implements two 16 taps FIR (Finite Impulse Response) filter that are realtime programmable through the operator interface. At DAΦNE, the Frascati PHI-Factory, two iGp units have been commissioned in the April 2007. The iGp systems have plugged in the previous betatron feedback systems. This insertion has been very fast and has shown no problems involving just a substitution of the old, less flexible, digital unit, letting unchanged the baseband analog frontend and the analog backend. The commissioning has been very simple, due to the complete and powerful EPICS operator interface, working well in local and remote operations. The software includes also tools for analyzing post processor data. A description of the commissioning with the operations done to find the best feedback setup are reported. | ||
| THPC117 | Measurements and Analysis of Beam Transfer Functions in the Fermilab Recycler Ring Using the Transverse Digital Damper System | 3254 |
|
||
| The Fermilab Recycler Ring Transverse Digital Damper System was designed to facilitate Beam Transfer Function measurements using a Network Analyzer connected to auxiliary system ports for timing and diagnostic purposes. The Digital Damper System has the capability for both open and closed loop measurements. The Beam Transfer Function measurements provide direct measurements of the machine impedance, beam stability, and beam parameters such as betatron tune and chromaticity. An overview of the technique is presented along with analysis and results from open and closed loop measurements in the Fermilab Recycler Ring. | ||
| THPC118 | Performance and Future Developments of the Diamond Fast Orbit Feedback System | 3257 |
|
||
| The electron beam in the Diamond Synchrotron Light Source is stabilised in two planes using a Global Beam Orbit Feedback system. This feedback system takes the beam position from 168 Libera electron beam position monitors, for both planes, and calculates offsets to 336 corrector power supplies at a rate ~10kHz. The design and implementation will be summarised, and system performance and first operational experience presented. Current and potential future developments of the system will be considered. | ||
| THPC119 | Progress of TLS Fast Orbit Feedback System and Orbit Stability Studies | 3260 |
|
||
| The orbit feedback system of the TLS has been deployed for a decade and continuously upgraded. However, due to limitation of the existing hardware, the system cannot remove orbit excursion caused by the perturbation due to fast operation of insertion devices. The newly proposed orbit feedback system with the upgraded digital BPM system and switching corrector power supply system is planned to be installed and commissioned in late 2008. The preliminary calculation on the stability performance for the orbit feedback system is presented in the report. New fast orbit feedback system can be expected to achieve a submicron stability of the electron beam working at a bandwidth of at least 60 Hz. | ||
| THPC120 | Conceptual Design and Performance Estimation of The TPS Fast Orbit Feedback System | 3263 |
|
||
| A 3 GeV Synchrotron (TPS) is proposed in Taiwan. Its storage ring consists of 24 double-bend cells with 6-fold symmetry and the circumference is 518.4m. The report presents the initial design of the fast orbit feedback system (FOFB) for TPS. The system uses 168 BPMs and 168 correct magnets to stabilize global closed orbit at 10 kHz updated rate. The different subsystems are modeled: the BPM systems, the corrector magnet, vacuum chamber, and etc. The latency of the communication and computation is also studied. The preliminary calculation on the stability performance for the orbit feedback system is presented in the report. The FOFB is expected to achieve a submicron stability of the electron beam working at a bandwidth of at least 100 Hz. | ||
| THPC121 | LHC Transverse Feedback System and its Hardware Commissioning | 3266 |
|
||
| A powerful transverse feedback system ('damper') has been installed in LHC. It will stabilise coupled bunch instabilities in a frequency range from 3 kHz to 20 MHz and at the same time damp injection oscillations originating from steering errors and injection kicker ripple. The transverse damper can also be used as an exciter for purposes of abort gap cleaning or tune measurement. The power and low-level systems layout are described along with results from the hardware commissioning. The achieved performance is compared with earlier predictions and requirements for injection damping and instability control. Requirements and first measurements of the performance of the low-level system are summarized. The chosen approach for the low-level system using advanced FPGA technology is very flexible allowing implementation of future upgrades of the signal processing without changing the hardware. | ||
| THPC122 | Digital Signal Processing for the Multi-bunch LHC Transverse Feedback System | 3269 |
|
||
| For the LHC a VME card has been developed that contains all functionalities for transverse damping, diagnostics and controlled bunch by bunch excitation. It receives the normalized bunch by bunch position from two pick-ups via Gigabit Serial Links (SERDES). A Stratix II FPGA is responsible for resynchronising the two data streams to the bunch-synchronous clock domain (40.08 MHz) and then applying all the digital signal processing: In addition to the classic functionalities (gain balance, rejection of closed orbit, pick-up combinations, one-turn delay) it contains 3-turn Hilbert filters for phase adjustment with a single pick-up scheme, a phase equalizer to correct for the non-linear phase response of the power amplifier and an interpolator to double the processing frequency followed by a low-pass filter to precisely control the bandwidth. Using two clock domains in the FPGA the phase of the feedback loop can be adjusted with a resolution of 10 ps. Built-in diagnostic memory (observation and post-mortem) and excitation memory for setting-up are also included. The card receives functions to continuously adjust its parameters as required during injection, ramping and physics. | ||
| THPC123 | The PSI DSP Carrier (PDC) Board - a Digital Back-end for Bunch-to-bunch and Global Orbit Feedbacks in Linear Accelerators and Storage Rings | 3272 |
|
||
| PSI has developed a signal processing VXS/VME64x board for accelerator applications like low-latency bunch-to-bunch feedbacks, global orbit feedbacks or low-level RF systems. The board is a joint development of PSI/SLS staff and staff working on the contribution of PSI for the European X-ray FEL (E-XFEL). Future applications of the board include the Intra-Bunchtrain Feedback (IBFB) of the E-XFEL as well as the upgrade of the SLS Fast Orbit Feedback (FOFB) and Multibunch Feedback (MBFB). The PDC board has four Virtex-4 FPGAs, two TS201 Tiger Sharc DSPs, VXS and VME64x 2eSST interfaces, and two front panel SFP multi-gigabit fibre optic links. Two 500-pin LVDS/multi-gigabit mezzanine connectors allow to interface the FPGAs to two application-dependent mezzanine modules each containing e.g. four 500 Msps 12-bit ADCs and two 14-bit DACs for the IBFB and MBFB, or four multi-gigabit SFP fibre optic transceivers for the FOFB. This paper reports on hardware and firmware concepts, system topologies and synergies of future applications. | ||
| THPC124 | The Manufacturing and Tests of The New Vertical Feedback Stripline at Soleil | 3275 |
|
||
| This paper describes the development of the kicker striplines for the bunch-by-bunch transverse instability feedback system at Soleil. A careful design of the striplines and of their vacuum feedthroughs was aimed at maximizing the effectiveness of the excitation power and minimizing the power taken from the beam. The excitation effectiveness improves with the shunt impedance. But, simultaneously, the beam impedance should be made as small as possible. We also found useful to estimate the temperature of the feedthroughs at high beam currents, especially on the ceramic-to-metal seals. We also report on the difficulties encountered with obtaining good feedthroughs. | ||
| THPC125 | Modeling and Simulation of the Longitudinal Beam Dynamics-RF Station Interaction in the LHC Rings | 3278 |
|
||
| A non-linear time-domain simulation has been developed to study the interaction between longitudinal beam dynamics and RF stations in the LHC rings. The motivation for this tool is to study the effect of RF station noise, impedance, and perturbations on the beam life and longitudinal emittance. It will be also used to determine optimal LLRF configurations, to study system sensitivity on various parameters, and to define the operational and technology limits. It allows the study of alternative LLRF implementations and control algorithms. The insight and experience gained from our PEP-II simulation is important for this work. In this paper we discuss properties of the simulation tool that will be helpful in analyzing the LHC RF system and its initial results. Partial verification of the model with data taken during the LHC RF station commissioning is presented. | ||
| THPC126 | Performance and Features of the Diamond TMBF System | 3281 |
|
||
| The Diamond Transverse Multibunch Feedback System (TMBF) comprises an in-house designed and built analogue frontend to select and condition the position signals for each bunch. This is combined with the Libera Bunch-by-Bunch system to digitise the signal and perform the relevant calculations before driving the output stripline kickers. As the electronics are based on an FPGA this has allowed us to implement several features in addition to the basic feedback calculations. We report on improvements to both the analogue and digital parts of the TMBF system, along with recent achievements in using the system for instability mode stabilisation and for tune measurement. Also we discuss the potential of the system and additional functionality we plan on introducing in the near future. | ||
| THPC127 | Filling of High Current Singlet and Train of Low Bunch Current in SPring-8 Storage Ring | 3284 |
|
||
| We performed the storage of high current singlet of 10mA/bunch and a train of bunches of 0.3mA/bunch under the bunch by bunch feedback systems with newly developed bunch current sensitive automatic attenuators with FPGA. The automatic attenuator reduces the signal level of the high current bunch by factor three to five to avoid the saturation of the feedback systems. With this system, the feedback systems suppress horizontal and vertical mode-coupling instabilities and raise the bunch current limit from 3.5mA/bunch to 12mA/bunch, and simultaneously the systems suppress the multi-bunch instabilities by resistive-wall and cavity higher order mode impedances. The improvement of the automatic attenuation system to fit to the final target of the bunch current in the train, 0.06mA/bunch, are being performed. The other problems which limit the filling patterns, such as saturation of the readout electronics of the beam position monitor system and the heating of vacuum components by high current bunches, will be briefly presented. | ||
| THPC128 | Bunch by Bunch Feedback by RF Direct Sampling | 3287 |
|
||
|
Recent ADCs have wide analog band-width which is enough for direct sampling of the RF signal from a beam position monitor without down conversion. We employed such ADCs for our bunch-by-bunch signal processor* and performed the feedback with the direct RF sampling of the signal from a beam position monitor to detect the position of bunches. With RF direct sampling, the down conversion stage which is used in usual RF front-end circuits and is composed of mixers, filters, delays and base-band amplifiers is not necessary. This simplifies the systems, and reduces the costs and the number of the tuning parameters. The feedback system with RF direct sampling is now in operation at user mode in SPring-8.
*T. Nakamura, K. Kobayashi. "FPGA BASED BUNCH-BY-BUNCH FEEDBACK SIGNAL PROCESSOR", Proc. of ICALEPCS 05. |
||
| THPC129 | Coupling Correction in NSLS X-ray Ring | 3290 |
|
||
| In this paper we describe MATLAB script for reduction of the transverse coupling in the NSLS X-ray storage ring. The algorithm is based on varying strength of the skew quadrupoles and observation of the vertical beam size. The details of the iterative procedure are also discussed. | ||
| THPC130 | Integrated Global Orbit Feedback with Slow and Fast Correctors | 3292 |
|
||
| The NSLS-II Light Source which is planned to be built at Brookhaven National Laboratory will provide users with ultra-bright synchrotron radiation sources and is designed for horizontal beam emittances <1 nm. Full utilization of the very small emittances and beam sizes requires sub-micron orbit stability in the storage ring. This can be provided by means of a wide bandwidth orbit feedback system. Traditional approach is to utilize a uniform set of fast correctors or use two separate systems with strong slow and weaker fast correctors. In the latter case two systems need to communicate to suppress transients associated with different update rates of corrector settings. In this paper we consider an integrated system with two types of correctors. Its main feature is that setpoints of slow correctors are updated with the same rate as fast correctors; however the bandwidth is limited in order to stay in linear regime. Possible architectures and technical solutions as well as achievable performance are discussed. | ||
| THPC131 | On the Optimal Number of Eigenvectors for Orbit Correction | 3295 |
|
||
| The singular value decomposition method is widely used for orbit correction in the storage rings. It is a powerful tool for inverting of the usually rectangular response matrices, which usually have rectangular form. Another advantage is flexibility to choose number of eigenvectors for calculation of required strengths of orbit correctors. In particular, by reduction in number of eigenvectors one can average over ensemble noise in the beam position monitors. A theoretical approach as well as experimental results on the NSLS VUV ring are presented. | ||
| THPC132 | Bunch by bunch Transverse Feedback Development at ESRF | 3297 |
|
||
| This paper describes the bunch by bunch transverse feedback implemented at ESRF. The first motivation of this project was to be able to cope with the constraint of the future operation of the ESRF with a stored current increased from 200mA to 300mA with a uniform or quasi uniform filling, but we were also interested in possible improvement of the operation with others filling patterns (16 and 4 bunches patterns for instance). Our system uses a classical scheme: The signal coming from a set of button type electrodes is demodulated in a homodyne RF front end and processed in a FPGA DSP to derive a correction signal which is applied to the beam with a wide band stripline kicker. Depending on the filling pattern of the storage ring (uniform filling or filling with a small number of high charge bunches), different kind of transverse instabilities have been observed in the past, due to the resistive wall impedance, ion trapping or mode coupling. We have tested the effect of our system in these different situation and report also the results of these tests. | ||
| THPC133 | Layout and Simulations of the FONT System at ATF2 | 3300 |
|
||
| We describe the adaptation of a Feedback On Nano-second Timescales (FONT) system for the final focus test beam line ATF2 at KEK. This system is located in the ATF2 extraction line, and is mainly conceived for cancellation of transverse jitter positions originated in the damping ring and by the extraction kickers. This jitter correction is performed by means of a combination of feed-forward (FF) and fast-feedback (FB) beam stabilisation. We define optimal positions for the kicker and BPM pairs of the FONT FF/FB system, and estimate the required kicker performance and BPM resolutions. Moreover simulation results are presented. | ||
| THPC135 | Vertical Emittance Measurements and Optimisation at the Australian Synchrotron | 3303 |
|
||
| Adjustment to the vertical emittance of the Australian Synchrotron storage ring was made using 28 skew quadrupoles. The skew quadrupole settings were calculated using the LOCO method which uses measurements of vertical dispersion as well as transverse coupling. The vertical emittance was monitored indirectly through lifetime, tune crossing, x-ray pinhole camera and calibrated model calculations. The paper outlines the results of these studies. | ||
| THPC136 | Design and Commissioning of a Bunch by Bunch Feedback System for the Australian Synchrotron | 3306 |
|
||
| A transverse bunch feedback system has been designed in order to fight the effects of coupled bunch instabilities. This system is currently in the commissioning phase. A digital system was chosen because of its flexibility and diagnostic potential. While the major components were sourced from a private company, time has also been spent on in house development of an analogue front-end and the diagnostic components of the software. | ||
| THPC138 | Bunch-by-Bunch Online Diagnostics at HLS | 3309 |
|
||
| The design goal for the bunch-by-bunch analogue transverse feedback system at the Hefei Light Source (HLS) is to cure the transverse coupled bunch instabilities. The prototype implemented bunch-by-bunch feedback in 2006. Then we changed the circuit and replaced some components by ones of higher performance in order to get better effect. Diagnostic techniques are important tools to determine instabilities and to confirm the performance of the feedback systems. In addition to transverse feedback this system can provide online beam diagnostics and analysis in transverse and longitudinal directions. The diagnostic functions can record the response of every bunch while the feedback system manipulates the beam. The experimental results are presented. | ||
| THPC139 | Properties of X-ray Beam Position Monitors at the Swiss Light Source | 3312 |
|
||
| Tungsten blade type X-ray beam position monitors (X-BPMs) are widely used at the SLS to stabilize the photon beam position at the the micron level. Various slow (~0.5 Hz) photon beam position feedbacks (SPBPFs) being an integral part of the global orbit feedback system have been in operation for several years. They are solely based on one X-BPM reading assuming that the photon beam movement is dominated by angle changes of the electron beam. This paper reports on the operation of the first SPBPF using two X-BPMs. This allows the separation of positional and angular variations of the electron beam, which is of special importance for the recently commissioned PolLux dipole beamline, as it is mostly sensitive to position changes. Correlations between the electron beam movement and the X-BPM readings are extensively analyzed in order to disentangle systematic errors of the position determination and real orbit motion. Methods are presented on how to recognize and correct or even avoid large systematic errors of the X-BPMs. With this knowledge, the demanding requirements on X-BPM accuracy in case of a SPBPF utilizing two X-BPMs could be fulfilled for the first time at the SLS. | ||
| THPC140 | The Performance of a Fast Closed Orbit Feedback System with Combined Fast and Slow Correctors | 3315 |
|
||
|
For NSLSII closed orbit feedback system, in order to reduce the noise caused by the step changes of the power supplies in the feedback system, the angular kick corresponding to the last bit of the power supplies for the fast correctors must be smaller than 3 nrad*. On the other hand, in order to carry out closed orbit alignment or orbit correction after a long term drift, we need strong correctors with 0.8 mrad kick strength*. In order to avoid the requirement of correctors with both large strength and very small minimum step size, we consider separate sets of slow correctors with large strength and fast correctors with smaller maximum strength. In order to avoid fast and slow feedback systems working in parallel, and avoid the possible interaction between two feedback systems, we consider the possibility of using only one fast feedback system with slow correctors periodically removing the DC components of the fast correctors so that the DC components in fast feedback system would not accumulate to reach saturation even after a large long term drift of the closed orbit motion. We report on simulation of the performance of this combined system for NSLSII in this paper.
* NSLSII Preliminary Design Report (2007) |
||
| THPC142 | The Operation Event Logging System of the SLS | 3318 |
|
||
| Modern 3rd generation synchrotron light sources aim for 100% availability. No single beam interruption is acceptable and every distortion of operation should be investigated: What caused the interruption? Can it be avoided in the future? If it can't be avoided, how can the recovery be accelerated? An automated event recording system has been implemented at the Swiss Light Source (SLS) in order to simplify this investigations. The system identifies distortions of the user operation and records automatically type and duration of the event. All relevant information connected to the event, from control system archive data to shift protocols, is linked to the event and presented in web pages. Additional information can be added manually. Each event will be assigned to a failure cause and area. Means to filter the events are provided. The paper will describe the concept and implementation of the even logging system at the SLS and the experiences with the system. | ||
| THPC143 | A Wide Range Electrons, Photons, Neutrons Beam Facility | 3321 |
|
||
| The DAΦNE Beam Test Facility is in operation since the 2003 and has been continuously improved and upgraded in order to take into account the many different requests coming from the high energy and accelerator community. The facility was initially optimized to produce single electron and positron in the 25-750 MeV energy rage, manly for high energy detector calibration and testing; it can now provide beam in a wider range of intensity, up to 1010 electrons/pulse, typically needed for accelerator diagnostic tests. In the last two years the facility has also been modified in order to produce tagged photons, and the possibility to deliver tagged neutrons in the MeV energy range is under study. The main results obtained, the performance and the most significant characteristics of the facility diagnostics and operation are presented, as well as the users experience collected during these years of operation. | ||
| THPC144 | A Beam Quality Monitor for LHC Beams in the SPS | 3324 |
|
||
| The SPS Beam Quality Monitor (BQM) system monitors the longitudinal parameters of the beam before extraction to the LHC to prevent losses and degradation of the LHC luminosity by the injection of low quality beams. It is implemented in two priority levels. The highest level is related to machine protection, e.g. verifying SPS-LHC synchronization and global beam structure. If the specifications are not met, the beam is dumped in the SPS before extraction. On the second level, individual bunch position, length and stability are checked for beam quality assessment. Tolerances are adapted to the mode of operation and extraction to the LHC can also be inhibited. Beam parameters are accessed by acquiring bunch profiles with a longitudinal pick up and fast digital oscilloscope. The beam is monitored for instabilities during the acceleration cycle and thoroughly checked a few ms before extraction for a final decision on extraction interlock. Dedicated hardware and software components implementing fast algorithms are required. In this paper the fast algorithms and their possible implementations are presented. | ||
| THPC145 | Reliability Analysis of the LHC Machine Protection System: Terminology and Methodology | 3327 |
|
||
| The trade-off between LHC machine safety and beam availability is one of the main issues related to the LHC MPS. Several studies have addressed it for different subsystems. They are followed by a project aiming at the development of a methodology which combines agent-based modeling and fault-tree analysis thus allowing a global analysis of the entire MPS. During this project, the need for a clarification and specification of the terminology has become apparent. Besides involving basic terms like safety, reliability and availability, the analysis must take into account the implementation of common design principles such as redundancy, fault tolerance, 'fail-safe' and self-monitoring. These terms and in particular their interrelations easily cause confusion. Since the traceability of the analysis depends on a consistent understanding of the underlying terminology, a terminology frame is being compiled. The paper specifies the most relevant terms and their interrelations. General standard definitions are taken as basis for a specification related to the MPS and its analysis respectively. The developed analysis methodology building on this terminology frame is introduced. | ||
| THPC146 | Beam Halo Monitor Using Diamond Detectors for XFEL/SPring-8 | 3330 |
|
||
| The construction of the XFEL facility at SPring-8 has been started. We have been developing a halo monitor as an interlock device for protection of undulator permanent magnets against radiation damage. When permanent magnets are irradiated with a halo part of 8GeV electron beam, magnetic fields are degraded permanently and laser oscillation is weakened. Therefore, the interlock device is required during machine operation. Diamond detector, which operates in photoconductive mode, is good candidate for electron beam sensor. The beam test of the diamond detector head has been carried out at the beam dump of the SPring-8 booster synchrotron. Minimum number of injected electron was about 1·105 /pulse, and we observed the pulse height of 0.1V having the pulse length of 0.6nsec FWHM without a preamplifier. The linearity of output signal on injected beam was also demonstrated. The beam halo monitor equipped with the diamond detectors is under manufacturing. The design and feasibility tests will be presented in this conference. | ||
| THPC147 | Generation of 1.5 Million Beam Loss Threshold Values | 3333 |
|
||
| CERN's Large Hadron Collider will store an unprecedented amount of energy in its circulating beams. Beam-loss monitoring (BLM) is, therefore, critical for machine protection. It must protect against the consequences (equipment damage, quenches of superconducting magnets) of excessive beam loss. 4000 monitors will be installed at critical loss locations. Each monitor has 384 beam abort thresholds associated; for 12 integrated loss durations (40 us to 83 s) and 32 energies (450 GeV to 7 TeV). Depending on monitor location, the thresholds vary by orders of magnitude. For simplification, the monitors are grouped in 'families'. Monitors of one family have the same thresholds at start-up; they protect similar magnets against equivalent loss scenarios. The start-up calibration of the BLM system is required to be within a factor of five in accuracy; and the final accuracy should be a factor of two. Simulations (backed-up by control measurements) determine the relation between the BLM signal, the deposited energy and the critical energy deposition for damage or quench (temperature of the coil). The paper presents the details and systematic of determining 1.5 million threshold values. | ||
| THPC148 | Interlock – the Machine Protection Function of Libera Brilliance | 3336 |
|
||
| The basic task of Libera Brilliance is electron beam position measurement. A secondary, but no less important, task is machine protection. Libera Brilliance activates Interlock output when the beam position is outside predefined limits. The Interlock subsystem also activates when the analog-to-digital converters (AD) are saturated and the beam position is only virtually centered. AD converter saturation is detected in the multiplexed fast peak detectors using AD converter rate data. The Interlock is designed for fail-safe operation. Within the FPGA window, a comparator function is performed on the Fast Acquisition position data delivered at a 10 kHz rate. Comparison is done separately for X and Y positions. Limits and operation mode are settable through the CSPI library. To avoid manual resetting of the Interlock, logic output is designed as a monostable cell. The described circuitry has been successfully implemented and tested in both laboratory and accelerator environments. | ||
| THPC149 | Beam Scraping to Detect and Remove Halo in LHC Injection | 3339 |
|
||
| Fast scrapers are installed in the SPS to detect and remove beam halo before extraction of beams to the LHC, to minimize the probability for quenching of super-conducting magnets in the LHC. We shortly describe the current system and then focus on our recent work, which aims at providing a system which can be used as operational tool for standard LHC injection. A new control application was written and tested with the beam. We describe the current status and results and compare these with detailed simulations. | ||
| THPC150 | The Use of Software in Safety Critical Interlock Systems of the LHC | 3342 |
|
||
| This paper will provide an overview of the software development and management techniques applied to interlock systems in the CERN accelerator complex. Despite the in essence hardware based approach, software and configuration data is present in various forms and has to be treated with special care when aiming at safe, reliable and available protection systems. Several techniques and methods deployed in the LHC machine protection systems are highlighted, regarding data management and version tracking, hardware choices, commissioning procedures, testing methods and first operational experiences with the systems in CERN's accelerator complex. | ||
| THPC151 | The Post-Mortem Analysis Software Used for the Electrical Circuit Commissioning of the LHC | 3345 |
|
||
| The hardware commissioning of the LHC has started in the first quarter of 2007, with the sector 7-8. A suite of software tools has been developed to help the experts with the access, visualization and analysis of the result of the tests. Using the experience obtained during this phase and the needs to improve the parallelism and the automation of the electrical circuits commissioning, a new user interface has been defined to have an overview of all pending tests and centralise the access to the different analysis tools. This new structure has been intensely used on sector 4-5 and during this time the test procedures for different types of electrical circuits have been verified, which has also allowed the implementation of new rules and features in the associated software. The hardware commissioning of the electrical circuits enters in a more critical phase in 2008, were the number of the tests executed increases rapidly as test will be performed in parallel on different sectors. This paper presents an overview on the post mortem analysis software, from its beginning as a simple graphical interface to the actual suite of integrated analysis tools. | ||
| THPC152 | Electro-optic Bunch Arrival Time Measurement at FLASH | 3348 |
|
||
| The operation of the next generation free electron lasers such as FLASH and the planned European XFEL requires drift free synchronization and femto-second stability. For this purpose an optical synchronization system has been developed, based on a mode-locked erbium-doped fiber laser, whose pulses are distributed over length stabilized fiber links. In order to evaluate the performance of the optical distribution system and the bunch arrival time monitors (BAM) an independent reference is needed. The measurement of the electro-optic (EO) response in a GaP crystal offers such a possibility. The method is destruction free and allows simultaneous determination of the peak current and the charge center of mass arrival time with femto-second precision. The measurements are performed with a 0.175 mm thick GaP crystal using 3 ps linearly chirped pulses from a Ti:Sa oscillator. The EO signal is encoded to the chirped pulse and spectrally resolved near crossed polarizers. Comparison of the EO and BAM timings provides a check of the relative accuracy of both methods, including the accuracy of the optical timing distribution system. | ||
| THPC153 | Timing System of the New Elettra Injector | 3351 |
|
||
| A new timing system has been developed to operate the new injector for the Elettra storage ring. It implements a versatile injection system to support standard and exotic fillings as well as the top-up mode of operation. Based on an in-house developed programmable counter VME board, the system provides all the needed triggers by the pre-injector LINAC, the booster injection, the booster ramping system, the booster extraction, and the SR injection. An overview of the system architecture and functionality is described and the performance of the board is reported. All the trigger signals are distributed to the timing clients by means of optical links. | ||
| THPC156 | Performances of the SPARC Laser and RF Synchronization Systems | 3354 |
|
||
| The SPARC project consists in a 150 MeV S-band, high-brilliance linac followed by 6 undulators for FEL radiation production at 530 nm. The linac assembly has been completed and the SPARC scientific program is presently in progress. The low level RF control electronics to monitor and synchronize the RF phase of the accelerating structures along the linac and the laser shot on the photocathode has been commissioned and it is now fully operative. The laser synchronization is routinely monitored and slow drifts are automatically corrected by a dedicated shot-to-shot feedback system. A similar slow automatic regulation is implemented on each linac accelerating section acting either on low level or high power sliding lines. The phase noise in the 2 RF power stations is counteracted by fast intra-pulse phase feedback systems that have been developed and put in operation. Phase stability measurements taken over the whole synchronization system are reported, and performances of different synchronization architectures, micro-wave based or laser based, are compared. | ||
| THPC157 | A Simple Method for Timing an XFEL Source to High-power Lasers | 3357 |
|
||
| We propose a technique for timing an XFEL to a high-power laser with femtosecond accuracy. The same electron bunch is used to produce an XFEL pulse and an ultrashort optical pulse that are, thus, naturally synchronized. Cross-correlation techniques will yield the relative jitter between the optical pulse (and, thus, the XFEL pulse) and a pulse from an external pump-laser with femtosecond resolution. Technical realization will be based on an optical replica synthesizer (ORS) setup to be installed after the final bunch-compressor. The electron bunch is modulated in the ORS by an external optical laser. Travelling through the main undulator, it produces the XFEL pulse. Then, a powerful optical pulse of coherent edge radiation is generated as the bunch passes through a long straight section and a separation magnet downstream of the main undulator. Relative synchronization of these pulses is preserved using the same mechanical support for X-ray and optical elements transporting radiation to the experimental area, where single-shot cross-correlation between optical pulse and pump-laser pulse is performed. We illustrate our technique with numerical examples referring to the European XFEL. | ||
| THPC158 | Measurement and Stabilization of the Bunch Arrival Time at FLASH | 3360 |
|
||
| To fully exploit the experimental opportunities offered by the 10 - 30 fs long light pulses from FLASH, e.g. in pump-probe experiments, precise measurements and control of the electron-bunch arrival-time on the 10 fs scale are needed. A bunch arrival time monitor (BAM) which uses the optical synchronization system of FLASH as a reference has been developed for this purpose. The bunch induced signal from a GHz-bandwidth beam pick-up is guided into an electro-optical modulator in which the periodic laser pulse train of the optical synchronization system experiences an amplitude modulation. Detection of this modulation allows to determine the bunch arrival time with a resolution of better than 20 fs. The superconducting linac of FLASH generates trains of up to 800 bunches. The BAM signals can be used for an intra-bunch train feedback stabilizing the arrival time to better than 50 fs. The feedback is capable of generating well-defined arrival time patterns within a bunch train which are useful for overlap-scans in pump-probe experiments. First results from the feedback installed at FLASH will be presented. | ||
| THPC159 | Timing and Event Distribution for FERMI@ELETTRA | 3363 |
|
||
| FERMI@ELETTRA is a 4th generation light source under construction at Sincrotrone Trieste. It will be operated as a seeded FEL driven by a warm S-band Linac which places very stringent specifications on control of the amplitude and phase of the RF stations. The local clock generation and distribution system at each station will not be based on the phase reference distribution but rather on a separate frequency reference distribution which has significantly less stringent phase stability requirements. This frequency reference will be embedded in the serial data link to each station and has the further advantage of being able to broadcast synchronous machine timing signals with sub-nanosecond temporal accuracy. The phase and amplitude of the phase reference line is measured for each pulse and used to calibrate the other measurements. This paper describes the architecture used to distribute the frequency reference along with the precision machine timing and clocking signals. | ||
| THPC160 | An Optical Cross-correlation Scheme to Synchronize Distributed Laser Systems at FLASH | 3366 |
|
||
| The soft X-ray free-electron laser FLASH and the planned European XFEL generate X-ray light pulses in the femto-second range. For time-resolved pump-probe experiments, future operation modes by means of laser seeding and for special diagnostic measurements it is crucial to synchronize various laser systems to the electron beam with an accuracy better than 30 fs. For this purpose an optical synchronization system at the telecommunication wavelength of 1550 nm is currently being installed and tested at FLASH. We developed a background-free optical cross-correlation scheme to synchronize two mode-locked laser systems of different center wavelengths and repetition rates with an accuracy better than 10 fs. The scheme was tested by linking a commercial 81 MHz Ti:Sa oscillator (center wavelength 800 nm), used for electro-optical diagnostics at FLASH, to a locally installed 40.5 MHz erbium-doped fiber laser, operating at 1550 nm. Later, this laser will be replaced by an actively length-stabilized fiber-link distributing the pulses from the 216 MHz master laser oscillator of the machine to lock the diagnostics laser to the optical synchronization system. | ||
| THPC162 | The SSRF Timing System | 3369 |
|
||
| In the Shanghai Synchrotron Radiation Facility (SSRF), various equipment in the 150MeV linac, the full energy booster and the 3.5GeV storage ring need to be triggered and synchronized by a low jitter timing system. An event system based on distribution network is implemented in the SSRF timing system. In this paper, the software and hardware structure of the SSRF timing system are described and the system performance is presented. |