NSRRC, Hsinchu
The highly stable pulsed magnets are designed for injection and extraction the electron beams operation in Taiwan Photon Source. The injection to the booster at 0.15 GeV is performed with septum and kicker devices as well as the extraction from the booster at 3 GeV. There are 5 in-vacuum septum and kicker magnets used for booster injection and extraction processes. For the storage ring, an injection of the electron beam into the storage ring is performed with a septum magnet and four identical kicker magnets. All pulsed magnets are designed for injection into the 3-GeV storage ring. The kicker magnet is excited with a 4.8-μs half-sine current waveform. A prototype of kicker magnet with 0.6 m of length is made and tested for examining the field errors. The field performances of the kicker magnet are presented. All pulsed magnets are fed with special current waveform. Both pulsed magnets are considered with the goal to achieve reliable work.
ANL, Argonne
Funding: This work was supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source is filled for five weeks per year in a special bunch (hybrid) pattern of one large 16-mA (74-nC) bunch in a gap of 3 microseconds, and the remaining 86 mA in 8 trains of 7 consecutive bunches, forming a 500-microsecond-long bunch train. We are developing variations of this bunch pattern, which might have 3 large bunches equally spaced in the 3-microsecond gap in a 4-mA, 16-mA, and 8-mA distribution. The 500-microsecond-long bunch train could be changed to 2 or 3 bunch trains of 7 bunches. We report on the difficulties in bringing these into future operations: impedance-driven injection losses, sextupoles in injection section, lifetime and topup injection limit, and beam diagnostics responses to the patterns.
BNL, Upton, Long Island, New York
The NSLS II is a state of the art 3 GeV synchrotron light source being developed at BNL. The injection system will consist of a 200 MeV linac and a 3GeV booster synchrotron. The injection system must supply 7.3nC every minute to satisfy the top off requirements. A large booster acceptance is neccessary to have a high booster injection efficiency and alleviate the requirements on linac gun. We also anticipate transverse stacking of bunches in the booster to increase the amount of charge that can be delivered. We present studies of the anticipated booster stay clear including lattice errors and the ramifications for injection efficiency and transverse stacking.
BNL, Upton, Long Island, New York
BESSY GmbH, Berlin
NSLS-II injection system contains 13 pulsed magnets and their power supplies for injection in and extraction from the booster and injection in the storage ring. Requirement of having injection process transparent for the NSLS-II users translates into challenging specifications for the pulsed magnet design. To keep the beam jitter within 10% of radiation source size, relative kicker mismatch must be kept on 10-5 level and residual vertical field must be below few gauss in amplitude. In this paper we discuss specifications for the pulsed magnets, their preliminary design and parameters' tolerances.
BNL, Upton, Long Island, New York
BESSY GmbH, Berlin
The NSLS-II is a state of the art 3 GeV synchrotron light source that is being developed at BNL. The 9.3 meter long injection straight section of NSLS-II storage ring currently fits a conventional injection set-up that consists of four kickers producing a closed bump together with a DC septum and a pulsed septum. In this paper we analyze alternative options based on: a) injection via a pulsed sextupole and b) injection with a Lambertson septum. We discuss dynamics of the injected and stored beams and, consequently, magnet specifications and tolerances. In conclusion we summarize advantages and drawbacks of each injection scheme.
HZB, Berlin
FhG, Euskirchen
PTB, Berlin
The 0.6 GeV storage ring Metrology Light Source (MLS) is in operation since April 2008. Recently, Cherenkov glass fibers have been installed for a temporal and spatial detection of electron beam losses. Based on this information the loss mechanisms can be studied in detail and the performance of the machine can be optimized. First experiments with this diagnostic tool will be presented.
JASRI/SPring-8, Hyogo-ken
SES, Hyogo-pref.
We have developed a kicker magnet system including a compact power supply to generate short pulse synchrotron radiation in the SPring-8 storage ring. One method to generate the short pulse synchrotron radiation is cutting out a synchrotron radiation coming from an tilted electron bunch with a slit. For this purpose, we induced a head-tail oscillation of an electron bunch due to non-zero vertical chromaticity excited by using a pulsed magnetic field. By using this scheme, the required specification to the magnet system is relaxed which leads to reduction of construction cost. Developed kicker magnet system can generate a short pulsed vertical field of about 3.6 mT within the 3 us to an electron bunch at 1 Hz repeat. With the kicker magnet system, we successfully observed a bunch profile which leans about 2 mm between head and tail position by a streak camera. We will report the detail setup of the kicker magnet system including compact power supply and the measurement system of beam profile, then discuss the comparisons between real beam motion and simulation results.
FEL/Duke University, Durham, North Carolina
BINP SB RAS, Novosibirsk
Funding: This work is supported by the US DoE grant #DE-FG02-01ER41175
A booster-injector synchrotron has been recently built and commissioned at Duke University to provide for the top-off injection into the storage ring in the energy range of 0.24 - 1.2 GeV. Booster injection kicker was designed with a pulse length of 18 out of 19 booster separatrixes, assuming a long train of electron bunches to be injected from the existing linac. Such scheme required a major linac upgrade from single bunch photo emission mode to a multibunch thermionic mode. A major disadvantage of the latter was much higher radiation levels in the facility. Since commissioning, the booster could only operate with one or two bunches limited by both long kicker pulse and single bunch injection from the linac. The consequent limitation of the injection rate restricted the capability of production of the Compton gamma rays in the loss mode, i.e. production of gammas with energy above 20-25 MeV, to about 5*108 photons per sec. Update of the linac for the repetition rate of up to 10 Hz, and modification of the injection kicker for 15 nS pulse length allowed us to developed an alternative multibunch injection scheme with a significant increase of the injection rate into storage ring.
Fermilab, Batavia
Funding: Work supported by Fermi Research Alliance, LLC under contract No. DE-AC02-07CH11359 with the United States Department of Energy.
Currently Main Injector delivers 330KW of beam power at 120 GeV by using multi-batch slip stacking. The beam power is expected to increase to 400KW after installing clearing gap kickers to eliminate the injection kicker gap loss. The plan to increase the beam power to 700KW for NOvA and the role of MI in Project-X (2.1MW operation) will be discussed.
Fermilab, Batavia
The multi-batch slip stacking has been used for operation since January, 2008 and effectively increased proton intensity to the NuMI target by 50% in a MI cycle. The MI accepts 11 pulses at injection energy from the Booster and sends two pulses to Anti-proton production and nine to the NuMI beam line. The total beam power on a cycle was increased to 340 KW on average. We have been doing beam studies in order to increase the beam power to 400 kW and to control the beam loss. We also discuss 12 batch slip stacking scheme which is going to be used for future Neutrino experiments.
BNL, Upton, Long Island, New York
Funding: Department Of Energy
Under certain assumptions and simplifications, we studied a few physics processes of Coherent Electron Cooling using analytical approach. In the modulation process, the effect due to merging the ion beam with the electron beam is studied under single kick approximation. In the FEL amplifier, we studied the amplification of the electron density modulation using 1D analytical approach. Both the electron charge density and the phase space density are derived in the frequency domain. The solutions are then transformed into the space domain through Fast Fourier Transformation (FFT).
Fermilab, Batavia
Run II has been ongoing since 2001. Peak luminosities in the Tevatron have increased from approximately 10×1030 cm-2ses-1 to 300×1030 cm-2ses-1 a factor of 30 improvement. A significant contributing factor in this remarkable progress is a greatly improved antiproton production capability. Since the beginning of Run II, the average antiproton accumulation rate has increased from 2×1010 p/hr to about 24×1010 p/hr. Peak antiproton stacking rates presently exceed 25×1010 p/hr. The antiproton stacking rate has nearly doubled in the last two years alone. A variety of improvements have contributed to the recent progress in antiproton production. The process of transferring antiprotons to the Recycler Ring for subsequent transfer to the collider has been significantly restructured and streamlined, allowing more time to be utilized for antiproton production. Improvements to the target station have greatly increased the antiproton yield from the production target. The performance of the Antiproton Source stochastic cooling systems has been enhanced by improvements to the cooling electronics, accelerator lattice optimization, and improved operating procedures.
FZJ, Jülich
CNS, Saitama
CERN, Geneva
The High Energy Storage Ring (HESR) of the future International Facility for Antiproton and Ion Research (FAIR) at the GSI in Darmstadt will be built as an anti-proton cooler ring in the momentum range from 1.5 to 15 GeV/c. An important and challenging feature of the new facility is the combination of phase space cooled beams with internal targets. In addition to electron cooling transverse and longitudinal stochastic cooling are envisaged to accomplish these goals. A detailed numerical analysis of the Fokker-Planck equation for longitudinal filter and time-of-flight cooling including an internal target and intrabeam scattering has been carried out to demonstrate the stochastic cooling capability. Model predictions have been compared to experimental cooling results with internal targets at the COSY facility. Experimental results at COSY to compensate the large mean energy loss induced by an internal Pellet target similar to that being used by the PANDA experiment at the HESR with a barrier bucket cavity (BB) will be presented. Experimental tests of stochastic filter cooling with internal target and BB operation as well as expected cooling properties for the HESR are discussed.
IAP, Frankfurt am Main
A chopper system for high intensity proton beams of up to 200 mA and repetition rates up to 250 kHz is under development at IAP to be tested and applied at the Frankfurt Neutron Source FRANZ. The chopper system consists of a fast kicker for transversal separation of the beams and a static septum magnet to lower the dynamic deflection angle. Multi-particle simulations and preliminary experiments are presented. The simulations were made using a Particle in Cell (PIC)-Code developed at IAP. It permits the study of collective effects of compensation and secondary electrons on the proton beam in time-dependent kicker fields. A magnetic kicker with high repetition rate would entail high power consumption while electrostatic deflection in combination with intense beams can lead to voltage breakdown. Therefore a Wien filter-type ExB configuration consisting of a static magnetic dipole field and a pulsed electric field to compensate the magnetic deflection is discussed. The 25 kV high voltage pulser (250 kHz, 100 ns) will apply fast MOSFET transistor technology in the primary circuit, while the high voltage is provided at the secondary circuit around a metglas transformer core.
NSRRC, Hsinchu
The purpose of this paper is to reduce the Electromagnetic Interference (EMI) from kicker and its pulsed power supply. Analysis of conducted and radiated EMI is the beginning mission. Different frequency range of radiated EMI was measured by different sensors. A hybrid shielding method was used to test reduction of radiated EMI. The copper and μ-metal enclosure was used on kicker magnet to prevent the radiated EMI. The reduction of electromagnetic field showed the effect of different material. Besides, the conducted EMI was also tested and eliminated by adding grounding routs. For decreasing grounding noise to other systems, the individual grounding bus was installed. The experimental results showed significant effect. In the future, TPS (Taiwan Photon Source) injection magnets will design higher performance, lower EMI than TLS (Taiwan Light Source). Therefore reducing and eliminating the interference of electromagnetic waves will be a very important issue. All the EMI prevention schemes will implement in the new project.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
Funding: ISIS
The Extracted Proton beam line for the ISIS second target station has two 10 Hz pulsed magnet systems and a DC Septum magnet system which extract the protons from the existing 50 Hz beam line. The pulsed Kicker 1 magnet system deflects the beam 12.1 mrad, pulsed Kicker 2 deflects the beam 95 mrad and the DC Septum magnet system deflects the beam 307 mrad. This paper describes the topology, installation, testing and successful operation of each of the power supplies.
CERN, Geneva
The Multi-Turn Extraction, a new type of extraction based on beam trapping inside stable islands in the horizontal phase space, has been commissioned during the 2008 run of the CERN Proton Synchrotron. Both single- and multi-bunch beams with a total intensity up to 1.4×1013 protons have been extracted with efficiencies up to 98%. Furthermore, injection tests in the CERN Super Proton Synchrotron were performed, with the beam then accelerated and extracted to produce neutrinos for the CERN Neutrino to Gran Sasso experiments. The results of the extensive measurement campaign are presented and discussed in details.
CERN, Geneva
The implementation of new Multi-turn extraction at the CERN Proton Synchrotron required major hardware changes for the nearly 50-year old accelerator. The installation of new PFNs and refurbished kicker magnets for the extraction, new sextupole and octupole magnets, new power converters, together with an in-depth review of the machine aperture leading to the design of new vacuum chambers was required. As a result, a heavy programme of interventions had to be scheduled during the winter shut-down 2007-8. The newly installed hardware and its commissioning is presented and discussed in details.
CERN, Geneva
Initial commissioning of the LHC beam dump system with beam took place in August and September 2008. The preparation, setting-up and the tests performed are described together with results of the extractions of beam into the dump lines. Analysis of the first detailed aperture measurements of extraction channels and kicker performance derived from dilution sweep shapes are presented. The performance of the other equipment subsystems is summarised, in particular that of the dedicated dump system beam instrumentation.
CERN, Geneva
For the LINAC4 project the PS Booster (PSB) injection system will be upgraded. The 160 MeV H- beam will be distributed to the 4 superimposed PSB synchrotron rings and horizontally injected by means of an H- charge-exchange system. Operational considerations for the injection system are presented, including expected beam losses from field stripping of H- and excited H0 and foil scattering, possible injection failure cases and expected stripping foil lifetimes. Loading assumptions for the internal beam dumps are discussed together with estimates of doses on various components.
CERN, Geneva
The LHC injection tests and first turn beam commissioning took place in late summer 2008, after detailed and thorough preparation. The beam commissioning of the downstream sections of the SPS-to-LHC transfer lines and the LHC injection systems is described. The details of the aperture measurements in the injection regions are presented together with the performance of the injection related equipment. The measured injection stability is compared to the expectations. The operational issues encountered are discussed.
CERN, Geneva
After each beam dump in the LHC automatic post-operational checks are made to guarantee that the last beam dump has been executed correctly and that the system can be declared to be 'as good as new' before the next injection is allowed. The analysis scope comprises the kicker waveforms, redundancy in kicker generator signal paths and different beam instrumentation measurements. This paper describes the implementation and the operational experience of the internal and external post-operational checks of the LHC beam dumping system during the commissioning of the LHC without beam and during the first days of beam operation.
CERN, Geneva
The conceptual considerations of a fast injection system for protons and ions in the proposed PS2 accelerator are presented. Initial design parameters of the injection septum and kicker systems are derived, taking into account rise and fall times, apertures and machine optics. The requirements for an injection dump used for failures are described. Possible limitations and technical issues are outlined.
CERN, Geneva
The LHC beam dump system is one of the most critical systems concerning machine protection and safe operation. It is used to dispose of high intensity beams between 450 GeV and 7 TeV. Studies into the consequences of abnormal beam dump actions have been performed. Different error scenarios have been evaluated using particle tracking in MAD-X, including an asynchronous dump action, and the impact of different orbit and collimator settings. Losses at locations in the ring and the beam dump transfer lines have been quantified as a function of different settings of the dump system protection elements. The implications for the setting up and operation of these protection elements are discussed.
KEK, Ibaraki
The kicker of the damping ring for the International linear collider(ILC) requires fast rise/fall times(3 or 6ns) and high repetition rate(3 MHz). A multiple strip-line kicker system is developing to realize the specification*. We present results of the beam test at KEK-ATF by the strip-line kicker**. The multi-bunch beam, which has 5.6ns bunch spacing in the damping ring, is extracted with 308ns duration. Two units of the strip-line electrodes are used to extract the beam. The scheme of the beam extraction is same as the kicker of the ILC. A bump orbit and an auxiliary septum magnet are used with the kicker to clear the geometrical restriction.
*T. Naito et. al., Proc. of PAC07, pp2772-2274
**T. Naito et. al., Proc. of EPAC08, pp601-603
NSRRC, Hsinchu
National Tsing Hua University, Hsinchu
The Taiwan Photon Source (TPS) is a new 3 GeV synchrotron light source to be built at the National Synchrotron Radiation Research Center (NSRRC) in Taiwan. The design of TPS is aimed to provide a low-emittance and high-brilliance beam with operation in the top-up mode. In this paper we present the design of the TPS injection section and the transport line from booster to storage ring. The specifications and parameters of the septa, kickers, and ceramic chambers are also described.
Fermilab, Batavia
Funding: Operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
We have designed and commissioned a system which blows up the transverse emittance of the anti-proton beam without affecting the proton beam. It consists of a bandwidth limited noise source centered around the betatron tune, a power amplifier and a directional stripline kicker. The amount of blow up is controlled by the amount of energy delivered to the anti-protons betatron bands.
IHEP Beijing, Beijing
China Spallation Neutron Source is a high intensity beam facility planed to build in future in China. It is composed of Linac, RCS and target station. The beam extraction from the RCS will be realized by ten vertical kicker magnet and one Lambertson magnet. One prototype kicker magnet has been successfully designed and developed in Institute of High Energy Physics. In this paper, the physical and structural design of the prototype kicker magnet are presented, and issues of the magnet development, construction and test are discussed.
CERN, Geneva
The goal of the present CLIC Test Facility (CTF3) is to demonstrate the technical feasibility of specific key issues in the CLIC scheme. The extracted drive beam from the combiner ring (CR), of 35 A in magnitude and 140 ns duration, is sent to the new CLic EXperimental area (CLEX) facility. A Tail Clipper (TC) is required, in the CR to CLEX transfer line, to allow the duration of the extracted beam pulse to be adjusted. Fours sets of striplines are used for the tail clipper, each consisting of a pair of deflector plates driven to equal but opposite potential. The tail clipper kick must have a fast field rise-time, of not more than 5 ns, in order to minimize uncontrolled beam loss. High voltage MOSFET switches have been chosen to meet the demanding specifications for the semiconductor switches for the modulator of the tail clipper. This paper discusses the design of the modulator; measurement data obtained during testing and operation of the tail clipper is presented and analyzed.
CERN, Geneva
Fast kicker magnets are used to inject beam into and eject beam out of the CERN SPS accelerator ring. These kickers are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the ferrite yoke can provoke significant beam induced heating, even above the Curie temperature of ferrite. In addition the impedance can contribute to beam instabilities. In this paper different variants of the coaxial wire method, both for measuring longitudinal and transverse impedance, are briefly discussed in a tutorial manner and do's and don'ts are shown on practical examples. In addition we present the results of several impedance measurements for SPS kickers using the wire method and compare those results with theoretical models.
Fermilab, Batavia
Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A fast kicker magnet has been designed for use in Main Injector at Fermilab. The magnet will be used for controlled removal of unbunched beam created in the slip stacking process. The strength of each of the six magnets is 75 G·m at 500 A. The aperture is 11.4 cm wide x 5.3 cm high x 64 cm long. The field rise time from 3% to 97% of less than 57 ns has been achieved along with a flattop variation of less than ±3% variation. Results of simulation and measurements will be presented. The pulser is described in a companion paper.
Fermilab, Batavia
Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
A fast kicker power supply has been designed for use in the Main Injector at Fermilab. The system will be used for controlled removal of unbunched beam created in the slip stacking process. A switch operating at 50 kV with a 3% to 97% rise time of less than 25 ns into a 50 Ω load is required. A thyratron and enclosure have been designed. A pulse length of 1.6 us is required so a cable pulse forming line is used. Results with and without a ferrite pulse sharpening line will be presented. The magnet is described in a companion paper.
FEL/Duke University, Durham, North Carolina
BINP SB RAS, Novosibirsk
Funding: Supported by US DoE grant #DE-FG02-01ER41175
The Duke FEL/HIGS (Free electron laser/High Intensity Gamma-ray source) facility has recently undergone through a series of major upgrade. As a part of this upgrade, a kicker system was designed to provide reliable injection from the booster into the storage ring at any energy chosen from the range of 240 MeV to 1.2 GeV. Relatively new and not sufficiently studied switching device has been selected as a basic component to build a set of nanosecond resolution high-voltage generators. So called Pseudo-Spark Switch (PSS), also known as a cold cathode thyratron, has the same or slightly better jitter, reasonable range of switched high voltages and significantly lower heater power as compared to the traditional “hot” thyratrons. Despite of the fact that it requires more complicated triggering system, this device still seems very attractive as a driver for short pulse kickers. Almost three years of operation of the Duke FEL facility has revealed number of advantages and challenges related to the thyratrons of this type. In this paper we depict design features of the kicker system, discuss some accomplished improvements and summarize our three year experience.
INFN/LNF, Frascati (Roma)
New injection stripline kickers are operating since December 2007 at the DAΦNE collider. They are designed to operate with very short pulse generators to perturb only the injected bunch and the two stored adjacent ones at 2.7 ns and are a test for the design of the fast kickers of the damping ring of the International Linear Collider (ILC). Stripline frequency response and impedance measurements have been performed to characterize the structure and are compared to the simulation results. Operational performances are also described, pointing out the problems occured and the flexibility of the stripline structure that worked with both the short and the old pulse generators and has been used as an additional damping kicker to improve the efficiency of the horizontal multibunch feedback system.
PSI, Villigen
At PSI, a new and very intensive Ultra-Cold Neutron (UCN) source based on the spallation principle will start operation at the end of 2009. From then on, two neutron spallation sources - the continuous wave SINQ and the macro-pulsed UCN source will be running concurrently at PSI. The 590 MeV, 1.2 MW proton beam will be switched towards the new spallation target for about 8 s every 800 s. This operation can be accomplished by means of a fast kicker magnet with a rise-time shorter than 1 ms. A beam dump capable of absorbing the full-intensity beam for a few milliseconds has been installed after the last bending magnet so that the kicking process and the beam diagnostic can be checked well before the UCN facility will be ready for operation. Recent tests have demonstrated the capability of switching the 1.2 MW beam with negligible losses and to center it through the beam line by using fast beam position monitors. Much longer beam pulses (up to 6 seconds) with reduced beam intensity have also been performed successfully.
SLAC, Menlo Park, California
Funding: Work supported by the Department of Energy under contract No. DE-AC02-76SF00515.
The design and installation of the Linac Coherent Light Source* at SLAC National Accelerator Laboratory has included the development of a kicker system for selective beam bunch dumping. The kicker is based on an LC resonant topology formed by the 50 uF energy storage capacitor and the 64 uH air core magnet load and has a sinusoidal pulse period of 400us. The maximum magnet current is 500 A. The circuit is weakly damped, allowing most of the magnet energy to be recovered in the energy storage capacitor. The kicker runs at a repetition rate of 120Hz. A PLC-based control system provides remote control and monitoring of the kicker via EPICS protocol. Fast timing and interlock signals are converted by discrete peak-detect and sample-hold circuits into DC signals that can be processed by the PLC. The design and experimental characterization of the systems is presented.
*http://ssrl.slac.stanford.edu/lcls/
SLAC, Menlo Park, California
Funding: Work supported by the Department of Energy under contract No. DE-AC02-76SF00515
The injection and extraction kickers (50 Ω) for the ILC damping rings will require highly reliable modulators to deliver ±5 kV, 2 ns flattop (~1 ns rise and fall time) electrical pulses at up to 6 MHz*. An effort is underway at SLAC National Accelerator Laboratory to meet these requirements using a transmission line adder topology to combine the output of an array of ~1 kV modules. The modules employ an ultra-fast hybrid driver/MOSFET that can switch 33 A in 1.2 ns. Experimental results for a scale adder structure will be presented.
*ILC Reference Design Report, http://www.linearcollider.org/cms/?pid=1000437
Tsukuba University, Ibaraki
A new concept of a fast magnetic kicker system - the bridged-T network lumped kicker - is proposed. The rise time is as fast as that of a transmission line kicker, while the input-impedance can be matched with a characteristic impedance of the pulse power supply. The proposed scheme is compared with several conventional schemes. The demonstration of this proposed scheme is also performed. The results show expected performances.
USTC/NSRL, Hefei, Anhui
Funding: Work supported by National Natural Science Foundation of China (No.10175062 & 10575100).
The light pulse interval adjustment at Hefei Light Source (HLS) can be realized by using pulsed orbit bump technique, which requires for high-frequency repetitive, high magnetic flux density, short pulse kicker magnet system of which the power supply modulator should be specially designed. The technique of solid state modulator based on MOSFET is being developed in National synchrotron Radiation Laboratory (NSRL). In this paper, the design of a prototype of solid-state modulator with 20 MOSFETs in parallel is introduced, including triggering system, drive circuit, transformer configuration. The oscillation induced by parasitic capacitance and inductance is discussed. This prototype with four stage adder can achieve 100ns width power pulse output with 112A, 2.4 kV to the kicker.
CERN, Geneva
The PS2 will replace the present CERN-PS as the LHC pre-injector. It will have twice the PS energy and twice the circumference. Extensive design optimization is presently ongoing with the aim of starting the PS2 construction around 2011 and delivering beams for physics in 2017. The talk describes the various PS2 design constraints, the optimization steps, and the path towards the final design.
BNL, Upton, Long Island, New York
After the success of longitudinal stochastic cooling of bunched heavy ion beam in RHIC, transverse stochastic cooling was installed and commissioned with proton beam. The talk presents the status of this effort and gives an estimate, based on simulation, of the RHIC luminosity with stochastic cooling in all planes.
NSRRC, Hsinchu
National Tsing Hua University, Hsinchu
The Taiwan Light Source (TLS), a third generation accelerator, has been operated successfully since 1993. It has been upgraded to increase the beam energy from 1.3 GeV to 1.5 GeV and the consequent capability of full energy injection afterwards. While the beam current has been increased from 200 mA to 300 mA after replacement of RF cavities with superconducting one. The vacuum pressure tends to decrease continuously after installations of 3 undulators and 4 wigglers as well as the new front ends. The accumulated beam dose increased faster up to > 14500 Ah after the routine operational top-up mode since 2006 with average pressure has been maintained below 0.13 nPa/mA. The beam life time of 6 hours at 300 mA has been kept with a limitation of Touschek life time at a stable beam with variation of photon flux < 0.05%. However, the photon absorbers of front ends have been replaced with new ones for subjecting the higher irradiation power after upgrading. The good dynamic pressure reflects the effective pumping performance. The experiences of components failures will be summarized in this paper.
SESAME, Amman
The SESAME booster, with a circumference of 38 m, has several bending magnets, focussing quadrupoles and defocussing quadrupoles and also the injection and extraction septums and kickers. There wil be one ramping power converter which supplies a series of 12 dipole magnets. Also 12 focussing magnets family and 6 defocussing magnets family are supplied separately with two ramping power converters. Technical issues of all the ramping and pulsed power supplies needed for the SESAME booster are disussed in this paper.
CERN, Geneva
Since 1999 the PS has been operated without active transverse damping thanks to an increase of the coupling between the transverse planes and the reduction of injection steering errors. Although the LHC requirements are met by these means, a new transverse feedback system has been commissioned to reinforce the robustness of operation and avoid the blow-up generated by residual injection steering errors. This system could also allow the reduction of the chromaticity and reduce the slow incoherent losses during the long PS injection plateau. It could also stabilize the high energy instabilities that appear occasionally with the LHC nominal beam and may be a limiting factor for ultimate LHC beam. Highlights include a signal processing with an automatic delay adapting itself to the varying revolution frequency, a programmable betatron phase adjustment along the cycle, pick-ups that have been re-furbished with electronics covering the very low frequency of the first betatron line and a compact wideband high-power solid state amplifier that drives the strip-line kicker via an impedance matching transformer. The overall system is described together with experimental results.
USTC/NSRL, Hefei, Anhui
Funding: supported by National Natural Science Foundation of China (10705027)
Hefei Advanced Light Source(HALS) is a super low emittance storage ring and has a very poor beam life time. In order to run the ring stablely, Top-up injection will be necessary. Injection system will greatly affect the quality of beam. This article first give a physics design of injecting system. Then the injecting system is tracked under different errors. The responses of storage beam and injecting beam is given in the article.
Fermilab, Batavia
CERN, Geneva
ETH, Zurich
Funding: Work partly supported by Fermilab, operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy
In the Large Hadron Collider LHC, particles not captured by the RF system at injection or leaking out of the RF bucket may quench the superconducting magnets during beam abort. The problem, common to other superconducting machines, is particularly serious for the LHC due to the very large stored energy in the beam. For the LHC a way of removing the unbunched beam has been studied and it uses the existing damper kickers to excite resonantly the particles travelling along the abort gap. In this paper we describe the results of simulations performed with MAD-X for various LHC optics configurations, including the estimated multipolar errors.
JAI, Oxford
ATOMKI, Debrecen
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
We present the results of beam tests of the FONT4 ILC prototype intra-train beam feedback system. The system comprises a stripline BPM, a fast analogue BPM signal processor, a custom FPGA-based digital feedback board, a high-power fast-response drive amplifier, and a stripline kicker. The hardware was deployed at the Accelerator Test Facility at KEK. Trains comprising three electron bunches were extracted from the ATF damping ring, with bunch spacing c. 150ns. The feedback loop was closed by measuring the position of bunch 1 and correcting bunches 2 and 3. We report the performance of the feedback, including gain studies, the correction dynamic range, latency measurement, and quality of the beam position correction. The system achieved micron-level bunch stabilisation with a latency of c. 140ns.
Imperial College of Science and Technology, Department of Physics, London
BNL, Upton, Long Island, New York
STFC/RAL/ASTeC, Chilton, Didcot, Oxon
STFC/RAL, Chilton, Didcot, Oxon
Non-scaling FFAG rings have been proposed as a solution for muon acceleration in the Neutrino Factory. In order to achieve small orbit excursion and small time of flight variation, lattices with a very compact cell structure and short straight sections are required. The resulting geometry dictates very difficult constraints on injection/extraction systems. The feasibility of injection/extraction is discussed and various implementations focusing on minimization of kicker/septum strength are presented.
EPFL, Lausanne
CERN, Geneva
KIT, Karlsruhe
Due to the known limitations of Phase I LHC collimators in stable physics conditions, the LHC collimation system will be complemented by additional 30 Phase II collimators. The Phase II collimation system is designed to improve cleaning efficiency and to minimize the collimator-induced impedance with the main function of protecting the Super Conducting (SC) magnets from quenching due to beam particle losses. To fulfil these requirements, different possible innovative collimation designs were taken in consideration. Advanced jaw materials, including new composite materials (e.g. CuDiamond), jaw SiC insertions, coating foil, in-jaw instrumentation (e.g. BPM) and improved mechanical robustness of the jaw are the main features of these new promising Phase II collimator designs developed at CERN. The FLUKA Monte Carlo code is extensively used to evaluate the behavior of these collimators in the most radioactive areas of LHC, supporting the mechanical integration. These studies aim to identify the possible critical points along the IR7 line.
UPC, Barcelona
CERN, Geneva
A main concern in high intensity rings is the evaluation of uncontrolled losses and their minimization using collimation systems. A two-stage systemis foreseen for the PS2. The fundamental design strategy for the collimation design is presented, including machine apertures and collimator materials. The dependence of the collimator system efficiency on the primary scraper length and the impact parameter of the particle is evaluated for different collimator locations. Beam loss maps are finally produced displaying the detailed power load deposited around the ring.
BNL, Upton, Long Island, New York
ANL, Argonne
Funding: Work supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contracts DE-AC02-98CH10886 and DE-AC02-06CH11357.
The NSLS-II Light Source being built at Brookhaven National Laboratory requires submicron stability of the electron orbit in the storage ring in order to utilize fully very small emittances and electron beam sizes. This sets high stability requirements for beam position monitors and a program has been initiated for the purpose of characterizing RF beam position monitor (BPM) receivers in use at other light sources. Present state-of-the-art performance will be contrasted with more recently available technologies. The details of the program and preliminary results are presented.
KEK, Ibaraki
Osaka University, Osaka
Proton beam extinction, defined as a ratio of the residual and the pulse beam intensity, should be less than 10-9, which is one of the key requirements to realize the future muon electron conversion experiment (COMET) proposed at J-PARC. Measurement of the pulse timing structure with enough sensitivity is the first step to achieve the required extinction level. We have developed two methods for the measurements; one by using fast-extracted beam and the other by using slow-resonant-extracted beam. This paper describes the schemes and the results of the measurements*. These measurements would provide important information on the beam pulse structure to understand not only for MR beam but also the whole accelelator complex, including LINAC and booster RCS.
*Submitted on behalf of the muon working group
LANL, Los Alamos, New Mexico
NSTec, Los Alamos, New Mexico
Funding: Work supported by the United States Department of Energy, DOE contract Number: W-7405-ENG-36
Accurate and reliable beam position measurements are required to commission and operate the DARHT II Accelerator. The Beam Position Monitor (BPM) system developed for use on the DARHT II accelerator consists of 31 electro-magnetic detector assemblies, a computer network based data acquisition system, and custom analysis software. During an accelerator “shot”, each BPM uses arrays of b-dot detectors to intercept the electron beam’s changing magnetic field. Post shot analysis of the BPM data provides the beam current and position information used for steering and tuning subsequent shots. This paper will analyze the performance of the BPM system, now that several thousand beam shots have been achieved.
BNL, Upton, Long Island, New York
Funding: Work Supported by the United States Department of Energy, Contract No. DE-AC02-98CH10886.
EMMA is an experiment to study beam dynamics in a linear non-scaling fixed-field alternating gradient accelerator (FFAG). It accelerates an electron beam from 10 to 20 MeV kinetic energy. To optimally perform these studies, one must be able to inject the beam at any energy within the machine's energy range. Furthermore, because we wish to study the behavior of large-emittance beams in such a machine, the injection systems must be able to inject the beam anywhere within a transverse phase space ellipse with a normalized acceptance of 3 mm, and the extraction systems must be able to extract from that same ellipse. I describe a computation of kicker and septum fields to achieve all of these requirements, and discuss how this interacts with the hardware constraints.
BNL, Upton, Long Island, New York
Fermilab, Batavia
The use of single stage bunch compressor (BC) in the International Linear Collider (ILC)* Damping Ring to the Main Linac beamline (RTML) requires new design for the extraction line (EL). The EL located downstream of the BC will be used for both an emergency abort dumping of the beam and the tune-up continuous train-by-train extraction. It must accept both compressed and uncompressed beam with energy spread of 3.54% and 0.15% respectively. In this paper we report design that allowed minimizing the length of such extraction line while offsetting the beam dumps from the main line by 5m distance required for acceptable radiation level in the service tunnel. Proposed extraction line can accommodate beams with different energy spreads at the same time providing the beam size suitable for the aluminum ball dump window.
*N. Phinney et al., “International Linear Collider Reference Design Report: Accelerator”, SLAC-R-857C
SLAC, Menlo Park, California
Funding: Work supported by the US Department of Energy, Office of Basic Energy Sciences.
We present nonlinear dynamics measurements and tracking for the SPEAR3 storage ring. SPEAR3 does not have a vertical pinger magnet, so we have developed a method of measuring (x, y) frequency maps by exciting vertical oscillations using a strip line driven with a swept frequency. When the vertical oscillations reach the desired amplitude, the drive is cut, and an injection kicker excites horizontal oscillations. The subsequent free horizontal and vertical betatron oscillations are digitized turn-by-turn. We have used measured and tracked frequency maps in (x, y) and (x, energy) to characterize and optimize the dynamic aperture, injection and lifetime of the SPEAR3 low emittance optics.
NSRRC, Hsinchu
Since the diagnostic system built with the new BPM system upgrade in TLS, we can observe and analyze the orbit stability more clearly and systematically. The disturbances to cause orbit fluctuation mainly come from power supply ripple, ground vibration, ID effects and etc. Removing the disturbed source is a straight, effective but inactive solution. Orbit feedback system is therefore adopted to suppress the remaining noise. In this report, we will evaluate the orbit stability in TLS and present the efforts we have done to improve the orbit stability.
NSRRC, Hsinchu
Beam qualities include orbit stability and multi-bunch instability plays a crucial role for the operation of a synchrotron light source. To improve and to keep high beam quality, intensive correlation analysis is performed between data taken by electron BPMs and photon monitors. Efforts of this study will be summary in this report.
NSRRC, Hsinchu
Commissioning of new digital BPM system for TLS is done recently. The new BPM system could support functionalities of turn by turn data, post-mortem and 10Hz slow data acquisition. 10 kHz fast data translation through Liberas grouping mechanism also succeeded to acquire all bpm data and integrate into the orbit feedback system. Various tests are performed systematically to confirm its performance and reliability and will be discussed in this report. We also present the functionalities and infrastructure of the related diagnostic tools. It could record 10 sec orbit data simultaneously via hardware and software event trigger at 10 kHz. Turn by turn and post mortem are also supported through embedded EPICS IOC. More integrated software tools and environment will continue to be developed for future operation.
BINP SB RAS, Novosibirsk
The VEPP-4M electron-positron collider is now operating with the KEDR detector for high-energy physics experiments in the 1.5−2.0 GeV beam energy range. Parallel with these experiments, the VEPP-4M scientific team carries out a number of accelerator physics investigations. A new registration system for the Touschek polarimeter has been put into operation. A new NMR-based system for suppression of the guide field ripples has been developed. The counting rate of the Touschek particles has been measured as a function of the beam energy in the range from 1.85 to 4 GeV. The measurement results can be claimed at the future super B and C-Tau factories. For simultaneous measurement of the transverse beam position and inclination angle an X-ray multi-pinhole camera has been designed, manufactured and installed at the VEPP-4M. To suppress the longitudinal instability caused by high-order modes of the RF cavities, a feedback system has been developed.
SLAC, Menlo Park, California
Life Imaging Technology, Palo Alto, California
Funding: Work sponsored by U.S. Department of Energy Contract DE-AC03-76SF00515 and Office of Basic Energy Sciences, Division of Chemical Sciences.
An intensified, fast-gated CCD camera was recently installed on the visible diagnostic beam line in SPEAR3. The ~2nS electronic gate capability, ability to make multiple-exposure images and to acquire sequences of images provides good diagnostic potential. Furthermore, the addition of a rotating mirror just upstream of the photocathode provides the ability to optically ‘streak’ multiple images across the photocathode. In this paper, we report on several fast-gated camera studies including (1) resonant excitation of vertical bunch motion, (2) imaging of the injected beam with and without emittance-spoiling windows in the upstream transfer line, (3) injection kicker tuning to minimize perturbations to the stored beam and (4) images of short-bunch ‘bursting’ in the low momentum-compaction mode of operation.
LNLS, Campinas
The main facility of the Brazilian Synchrotron Light Laboratory is a 1.37 GeV Synchrotron Light Source. The accelerator ring can be filled with up to 148 electron bunches and the initial current of 250 mA decreases down to 150 mA at the end of the user’s shifts. The beam energy is ramped down to 500 MeV, the current is refilled and the energy is ramped up again to 1.37 GeV for a new shift. Coupled-bunch instabilities excited by different sources can negatively impact the light source performance either lowering the brilliance of the beam or causing beam losses in the energy ramps. The upcoming new insertion devices and beamlines are pushing up the beam stability requirements even more. We present the current status of a digital feedback system that is being designed for controlling transversal and longitudinal beam instabilities.
CLS, Saskatoon, Saskatchewan
I-Tech, Solkan
A high-purity single-bunch operating mode, required for time-resolved experiments, has been introduced into the CLS Storage Ring. The newly deployed Transverse Feedback System, which uses the Libera Bunch-by-Bunch system as the feedback processor, has added features that inherently enable bunch cleaning. The bunch purification mechanism is based on a frequency modulated signal that drives the unwanted bunches into betatron oscillations to remove them from the Storage Ring. Bunch purities of 10-6 are achieved, limited only by the leakage rate from adjacent bunches.
Dimtel, San Jose
LBNL, Berkeley, California
IHEP Beijing, Beijing
BEPC-II is a two ring electron-positron collider designed to operate at 1 A beam currents. Longitudinal and transverse coupled-bunch instabilities have been observed in both electron and positron rings. In this paper we present measurements of both transverse and longitudinal instabilities with the identification of active eigenmodes, measurements of growth and damping rates, as well as of the residual beam motion levels. The measurements will then be used to estimate the growth rates at the design beam currents (yet to be achieved). We will also demonstrate how such data is used for specifying power amplifier and kicker parameters.
FEL/Duke University, Durham, North Carolina
PAL, Pohang, Kyungbuk
Dimtel, San Jose
Funding: work supported by US Air Force Office of Scientific Research medical FEL grant FA9550-04-01-0086
The coupled bunch mode instabilities (CBMIs) caused by vacuum chamber impedance limit and degrade the performance of the storage ring based light sources. A bunch-by-bunch longitudinal feedback (LFB) system has been developed to stabilize beams for the operation of a storage ring based Free Electron Laser (FEL) and the High Intensity Gamma-ray Source (HIGS) at the Duke storage ring. Employing a Giga-sample FPGA based processor (iGP), the LFB is capable of damping out the dipole mode oscillation for all 64 bunches. As a critical subsystem of the LFB system, kicker cavity is developed with a center frequency of 938 MHz, a wide bandwidth (> 90 MHz), and a high shunt impedance (> {10}00 Ω). First commissioned in summer 2008, the LFB has been operated to stabilize high current multi-bunch operation. More recently, the LFB system is demonstrated as a critical instrument to ensure stable operation of the HIGS with a high intensity gamma beam above 20 MeV with a frequent top-off injection to compensate for the substantial and continuous electron beam loss in the Compton scattering process. In the future, we will perform detailed studies of the impedance effects using the LFB system.
INFN/LNF, Frascati (Roma)
In this paper the horizontal feedback upgrade for the positron DAΦNE ring is presented. After having completed the analysis of the e+ current limit behavior, a feedback upgrade has been turned out necessary. For the success of the crab waist experiment in the 2008 year, a fast solution to implement the upgrade has been necessary. It has been considered if a simple power increase would be the best solution. The lack of power combiners and of space for other two power amplifiers has brought to a different approach, doubling the entire feedback system. The advantages of this implementation respect to a more traditional power amplifier doubling are evident: two feedback kicks every revolution turns, better use of the power amplifiers, greater reliability, and less coherent noise in the system. Measurements of the two feedbacks have shown a perfect equivalence of the new and the old system: in fact the resulting damping rate is exactly the double of each system taken individually. A description of the implementation is presented together with the performance of the system.
JAI, Oxford
The major goals of the final focus test beam line facility ATF2 are to provide electron beams with a few tens nanometer beam sizes and beam stability control at the nanometer level. In order to achieve such a level of stability beam based feedback systems are necessary at different timescales to correct static and dynamic effects. In particular, we present the design of intra-train feedback systems to correct the impact of fast jitter sources. We study a bunch-to-bunch feedback system to be installed at the extraction line to combat the ring extraction transverse jitters. In addition, we design a bunch-to-bunch feedback system at the interaction point for correction of position jitter due to the fast vibration of the magnets in the final focus. Optimum feedback software algorithms are discussed and simulation results are presented.
USTC/NSRL, Hefei, Anhui
A bunch-by-bunch analogue transverse feedback system at the Hefei Light Source (HLS) is to cure the resistive wall instability and the transverse coupled bunch instabilities. The kicker of the feedback system has four 21-cm-long electrodes of stripline type mounted in a skew 45°. Calculation and Simulation of the transverse kicker are shown.
UW-Madison, Madison, Wisconsin
ORNL, Oak Ridge, Tennessee
Funding: *Work performed under the auspices of ORNL/SNS, ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725
An electron-proton (e-p) instability is observed with increased beam intensity at the Spallation Neutron Source (SNS) in Oak Ridge National Laboratory (ORNL). This paper presents a wide-band, mixed-signal system for active damping of the e-p instability. It describes techniques used for feedback damping, data acquisition, and analysis. The paper also describes analysis strategies to monitor system performance. The mixed-signal feedback damper system includes anti-aliasing low-pass filters, power amplifiers (PAs), analog-to-digital converters (ADCs), reconfigurable field programmable gate array (FPGA) hardware and digital-to-analog converters (DACs). The system will provide feedback damping, system monitoring, and offline analysis capabilities. The digital portion of the system features programmable gains and delays, and equalizers that are implemented using parallel comb filters and finite impulse response (FIR) filters. These components perform timing adjustments, compensate for gain mismatches, correct for ring harmonics, and equalize magnitude and phase dispersions from cables and amplifiers.
BNL, Upton, Long Island, New York
Cooling intense high-energy hadron beams remains a major challenge in modern accelerator physics. Synchrotron radiation is still too feeble, while the efficiency of two other cooling methods, stochastic and electron, falls rapidly either at high bunch intensities (i.e. stochastic of protons) or at high energies (e-cooling). In this talk a specific scheme of a unique cooling technique, Coherent Electron Cooling, will be discussed. The idea of coherent electron cooling using electron beam instabilities was suggested by Derbenev in the early 1980s, but the scheme presented in this talk, with cooling times under an hour for 7 TeV protons in the LHC, would be possible only with present-day accelerator technology. This talk will discuss the principles and the main limitations of the Coherent Electron Cooling process. The talk will describe the main system components, based on a high-gain free electron laser driven by an energy recovery linac, and will present some numerical examples for ions and protons in RHIC and the LHC and for electron-hadron options for these colliders. BNL plans a demonstration of the idea in the near future.
CERN, Geneva
Fast kicker magnets are used to inject beam into and eject beam out of the CERN SPS accelerator ring. These kickers are generally ferrite loaded transmission line type magnets with a rectangular shaped aperture through which the beam passes. Unless special precautions are taken the impedance of the ferrite yoke can provoke significant beam induced heating, over several hours, even above the Curie temperature of the ferrite. At present the nominal bunch spacing in the SPS is 25 ns, however for an early stage of LHC operation it is preferable to have 50 ns bunch spacing. Machine Development (MD) studies have been carried out with an inter-bunch spacing of 25 ns, 50 ns or 75 ns. For some of the SPS kicker magnets the 75 ns bunch spacing resulted in considerable beam induced heating. In addition the MDs showed that 50 ns bunch spacing could result in a very rapid pressure rise in the kicker magnet and thus cause an interlock. This paper discusses the MD observations of the SPS kickers and analyses the available data to provide explanations for the phenomena: possible remedies are also discussed.
Omega-P, Inc., New Haven, Connecticut
Columbia University, New York
Yale University, Beam Physics Laboratory, New Haven, Connecticut
NSC/KIPT, Kharkov
Funding: US Department of Energy, Office of High Energy Physics, Advanced Accelerator R & D.
A rectangular two-beam dielectric wakefield accelerator (DWA) module is described which, when energized by a 14 MeV, 50 nC drive bunch moving in one channel, is shown to deflect a test bunch which originates from an independent source moving in a parallel channel. We show that such a module, 30 cm in length, can deflect transversely a 1 GeV electron by ~ 1 mrad in 1 ns, after which a following bunch can pass undeflected. Apparatus required to accomplish this task consists of a laser-cathode RF gun and an optional linac to generate the drive bunch. The associated DWA components could be used for kicker applications in a storage ring or a more energetic electron linear accelerator. An example we describe is tailored to a DWA demonstration project underway at the Argonne Wakefield Accelerator, but the design can be altered to allow for changes including a lower-energy but still relativistic drive bunch. The kicker, through appropriate design, can deflect one out of several bunches in a storage ring, leaving the remaining bunches essentially unaffected by the structure.
ORNL, Oak Ridge, Tennessee
IUCF, Bloomington, Indiana
Funding: ORNL/SNS is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725.
During one of the high beam intensity runs in SNS, a coasting beam instability was observed in the ring when the beam was stored for 10000 turns. This instability was observed at an intensity of about 12 microcoulombs and was characterized by a frequency spectrum peaking at about 6 MHz. A likely cause of the instability is the impedance of the ring extraction kickers. We carry out here a detailed benchmark of the observed instability, uniting an analysis of the experimental data, a precise ORBIT Code tracking simulation, and a theoretical estimate of the observed beam instability.
BNL, Upton, Long Island, New York
CERN, Geneva
Funding: This work has been partially performed under the auspices of US department of energy
Measurements of transverse impedance in the SPS to track the evolution over the last few years show discrepancies compared to the analytical estimates of the major contributors. Recent measurements to localize the major sources of the transverse impedance using intensity dependent optics are presented. Some simulations using HEADTAIL to understand the limitations of the reconstruction and related numerical aspects are also discussed.
EPFL, Lausanne
CERN, Geneva
BNL, Upton, Long Island, New York
The upgrade of the CERN Large Hadron Collider (LHC) would require a four- to fivefold increase of the single bunch intensity presently obtained in the Super Proton Synchrotron (SPS). Operating at such high single bunch intensities requires a detailed knowledge of the sources of SPS beam coupling impedance, so that longitudinal and transverse impedance reduction campaigns can be planned and performed effectively if needed. In this paper, the transverse impedance of the SPS is studied by injecting a single long bunch into the SPS, and observing its decay without RF. This particular setup enhances the resolution of the frequency analysis of the longitudinal and transverse bunch signals acquired with strip line couplers connected to a fast data acquisition. It also gives access to the frequency content of the transverse impedance. Results from measurements with short and long bunches in the SPS performed in 2008 are compared with simulations and theoretical predictions.
EPFL, Lausanne
CERN, Geneva
A detailed knowledge of the beam coupling impedance of the CERN synchrotrons is required in order to identify the impact on instability thresholds of potential changes of beam parameters, as well as additions, removal or modifications of hardware. To this end, an update of the impedance database was performed, so that impedance results from theoretical calculations using new multilayer models, impedance results from electromagnetic field simulations and impedance results from bench measurements can be compiled. In particular, the impedance database is now set to separately produce the dipolar and quadrupolar transverse impedance and wakes that the HEADTAIL simulation code needs to accurately simulate the effect of the impedance on the beam dynamics.
CERN, Geneva
First reference measurements of the longitudinal impedance were made with beam in the SPS machine in 1999 to quantify the results of the impedance reduction programme, completed in 2001. The 2001 data showed that the low-frequency inductive impedance had been reduced by a factor 2.5 and that bunch lengthening due to the microwave instability was absent up to the ultimate LHC bunch intensity. Measurements of the quadrupole frequency shift with intensity in the following years suggest a significant increase in impedance (which nevertheless remains below the 1999 level) due to the installation of eight extraction kickers for beam transfer to the LHC. Microwave instability is still not observed up to the maximum bunch intensities available from injector. The experimental results are compared with expectations based on the known longitudinal impedance of the different machine elements in the SPS.
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
KEK, Ibaraki
Kicker magnets are ones of dominant sources of impedances in the 3GeV Rapid Cycling Synchrotron (RCS) at Japan Proton Accelerator Research Complex (J-PARC). They may be limiting factors in achieving high intensity beams. Recently, the 300kW beam was accomplished at 3GeV RCS, while no instability was observed. In this paper, the space-charge effects are studied as beam stabilization effects.
ZTEC Instruments, Albuquerque
ORNL, Oak Ridge, Tennessee
The EPICS Oscilloscopes have been evaluated to perform simultaneous real-time pass-fail monitoring of two or four waveforms. The EPICS oscilloscopes are remotely controlled and monitored via LAN. Operators can control and query all instrument functions and settings, and monitor captured waveforms via EPICS PVs, an EDM panel, or via a “virtual front panel” application running in Linux or Windows. Upper and lower waveform masks used for pass-fail testing are automatically generated by the oscilloscope from a captured “golden waveform”. A variable-width output pulse is generated upon every captured waveform that passes (falls within the masks) or fails (falls outside the masks), depending on the operator’s requirements. Real-time pass-fail monitoring has been demonstrated on the teststand for the Spallation Neutron Source (SNS) injection and extraction kicker waveforms occurring both at 60Hz and 120Hz. We believe that the same instruments will also support SNS’s future requirements for real-time monitoring of waveforms at 120Hz.
NSCL, East Lansing, Michigan
The Facility for Rare Isotope Beams (FRIB) will provide intense beams of short-lived isotopes for fundamental research in nuclear structure and nuclear astrophysics. Operation of the facility requires intense uranium primary beams. At the present time acceleration of two simultaneous charge states of uranium from a single ion source is needed to achieve the required intensity. Three schemes are considered for funneling the beams from two sources as an alternate solution. One is the traveling wave RF kicker for merging of bunched beams extracted from ECR ion sources. Another one implements the idea of utilizing an RFQ for beam merging*, which can be used after preliminary acceleration of both beams. The third approach assumes usage of a conventional standing-wave RF kicker. Parameters of all three schemes are compared and analyzed.
*R.H.Stokes and G.N.Minerbo, AIP Conference Proceedings 139 (1985), p.79.