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CSR in the SuperKEKB Damping Ring

Description: Coherent synchrotron radiation (CSR) is generated when a bunched beam traverses a dipole magnet or a wiggler/undulator. It can degrade the beam quality in both storage rings and linacs through enhancing the beam energy spread and lengthening the bunch length, even cause single-bunch microwave instabilities. Using several methods, CSR impedances in the positron damping ring (DR) of the SuperKEKB which is under design were calculated. From the impedances due to CSR, resistive wall and various vacuum components, quasi-Green function wake potentials were constructed and used in simulations of Particle-In-Cell (PIC) tracking. We present the CSR related results in this paper.
Date: July 6, 2012
Creator: Zhou, Demin; /KEK, Tsukuba; Abe, Tetsuo; /KEK, Tsukuba; Ikeda, Hitomi; /KEK, Tsukuba et al.
Partner: UNT Libraries Government Documents Department

Coupling Measurements in ATF2 Extraction Line

Description: The purpose of ATF2 is to deliver a beam with stable very small spotsizes as required for future linear colliders such as ILC or CLIC. To achieve that, precise controls of aberrations such as dispersion and coupling are necessary. Theoretically, the complete reconstruction of the beam matrix is possible from the measurements of horizontal, vertical and tilted beam sizes, combining skew quadrupole scans at several wire-scanner positions. Such measurements were performed in the extraction line (EXT) of ATF2 in May 2009. We present analysis results attempting to resolve the 4 x 4 beam matrix. We aimed to reconstruct the full beam matrix using only skew quadrupole scans at different EXT wire-scanner locations, with measurements of horizontal, vertical and two tilted beam size projections. Checking the coherence of the {sigma}{sub 13} reconstruction from the {sigma}{sub 80{sup o}} and the {sigma}{sub 100{sup o}} measurements was essential to perform this analysis. We have shown that reconstruction of the coupling element can not be performed independantly of the 4 x 4 diagonal ones since it leads to unphysical results. A more accurate and automatisable method was find, leading to physical beam matrix reconstruction, compatible with the measurements. Another analysis should be performed based on a larger number of data sets to minimise statistical errors.
Date: June 29, 2012
Creator: Rimbault, Cecile; /Orsay, LAL; Kuroda, Shigeru; /KEK, Tsukuba; Tauchi, Toshiaki; /KEK, Tsukuba et al.
Partner: UNT Libraries Government Documents Department

A Superconducting Magnet Upgrade of the ATF2 Final Focus

Description: The ATF2 facility at KEK is a proving ground for linear collider technology with a well instrumented extracted beam line and Final Focus (FF). The primary ATF2 goal is to demonstrate the extreme beam demagnification and spot stability needed for a linear collider FF. But the ATF2 FF uses water cooled magnets and the ILC baseline has a superconducting (SC) FF. We plan to upgrade ATF2 and replace some of the warm FF magnets with SC FF magnets. The ATF2 SC magnets, like the ILC FF, will made via direct wind construction. ATF2 coil winding is in progress at BNL and warm magnetic measurements indicate we have achieved good field quality. Studies indicate that having ATF2 FF magnets with larger aperture and better field quality should allow reducing the ATF2 FF beta function for study of focusing regimes relevant to CLIC. The ATF2 magnet cryostat will have laser view ports for directly monitoring cold mass movement. We plan to make stability measurements at BNL and KEK to relate ATF2 FF magnet performance to that of a full length ILC QD0 R&D FF prototype under construction at BNL.
Date: July 5, 2012
Creator: Parker, Brett; /Brookhaven; Anerella, Michael; /Brookhaven; Escallier, John; /Brookhaven et al.
Partner: UNT Libraries Government Documents Department

Scenarios for the ATF2 Ultra-Low Betas Proposal

Description: The current ATF2 Ultra-Low beta proposal was designed to achieve 20nm vertical IP beam size without considering the multipolar components of the FD magnets. In this paper we describe different scenarios that avoid the detrimental effect of these multipolar errors to the beam size at the interaction point (IP). The simplest approach consists in modifying the optics, but other solutions are studied as the introduction of super-conducting wigglers to reduce the emittance or the replacement of the normal-conducting focusing quadrupole in the Final Doublet (NC-QF1FF) with a super-conducting quadrupole one (SC-QF1FF). These are fully addressed in the paper.
Date: June 29, 2012
Creator: Marin, Eduardo; /CERN; Tomas, Rogelio; /CERN; Bambade, Philip; /Orsay, LAL et al.
Partner: UNT Libraries Government Documents Department

The Straightness Monitor System at ATF2

Description: The demonstration of absolute stability of the position of the focused beam is the primary goal of the ATF2 commissioning effort. We have installed a laser interferometer system that will eventually correct the measurement of high-precision Beam Position Monitors used in the ATF2Final Focus Steering Feedback for mechanical motion or vibrations. Here, we describe the installed system and present preliminary data on the short- and long-term mechanical stability of the BPM system.
Date: July 6, 2012
Creator: Hildreth, Michael; U., /Notre Dame; Aryshev, Alexander; /Royal Holloway, U. of London; Boogert, Stewart; /Oxford U., JAI et al.
Partner: UNT Libraries Government Documents Department

Present Status of the ILC Project and Development

Description: The Technical Design of the International Linear Collider (ILC) Project will be finished in late 2012. The Technical Design Report (TDR) will include a description of the updated design, with a cost estimate and a project plan, and the results of research and development (R & D) done in support of the ILC. Results from directed ILC R & D are used to reduce the cost and risk associated with the ILC design. We present a summary of key challenges and show how the global R & D effort has addressed them. The most important activity has been in pursuit of very high gradient superconducting RF linac technology. There has been excellent progress toward the goal of practical industrial production of niobium sheet-metal cavities with gradient performance in excess of 35 MV/m. In addition, three purpose-built beam test facilities have been constructed and used to study and demonstrate high current linac performance, electron-cloud beam dynamics and precision beam control. The report also includes a summary of component design studies and conventional facilities cost optimization design studies.
Date: September 1, 2011
Creator: Ross, M.; /Fermilab; Walker, N.; /DESY; Yamamoto, A. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Advances in X-Band TW Accelerator Structures Operating in the 100 MV/M Regime

Description: A CERN-SLAC-KEK collaboration on high gradient X-band accelerator structure development for CLIC has been ongoing for three years. The major outcome has been the demonstration of stable 100 MV/m gradient operation of a number of CLIC prototype structures. These structures were fabricated using the technology developed from 1994 to 2004 for the GLC/NLC linear collider initiative. One of the goals has been to refine the essential parameters and fabrication procedures needed to realize such a high gradient routinely. Another goal has been to develop structures with stronger dipole mode damping than those for GLC/NLC. The latter requires that the surface temperature rise during the pulse be higher, which may increase the breakdown rate. One structure with heavy damping has been RF processed and another is nearly finished. The breakdown rates of these structures were found to be higher by two orders of magnitude compared to those with equivalent acceleration mode parameters but without the damping features. This paper presents these results together with some of the earlier results from non-damped structures.
Date: July 5, 2012
Creator: Higo, Toshiyasu; /KEK, Tsukuba; Higashi, Yasuo; /KEK, Tsukuba; Matsumoto, Shuji; /KEK, Tsukuba et al.
Partner: UNT Libraries Government Documents Department

High-Energy Laser Ponderomotive Acceleration

Description: A new concept of TeV-range laser ponderomotive acceleration in a plasma is proposed. Particles are accelerated in the point-like scattering by the leading front of the laser pulse, propagating at the group velocity less than the vacuum speed of light. In this scheme, the gain in particle energy is determined by the group velocity and does not depend on laser intensity, which determines the quantum probability of acceleration. The quantum and classical analysis of the scheme proposed is presented. Estimates show that the concept proposed is a promising technique for compact laser acceleration of TeV energy range.
Date: March 10, 2006
Creator: Smetanin, I.V.; Inst., /Lebedev; Barnes, C.; /SLAC; Nakajima, K. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Induction barrier RF and applications in Main Injector

Description: Two induction barrier rf systems have been designed and fabricated at Fermilab and installed in the Main Injector. They use the nanocrystal magnetic alloy called Finemet for the cavities and high voltage fast MOSFET switches for the modulators. Each system delivers {+-}10 kV square pulses at 90 kHz. They have been used for adiabatic beam stacking (beam compression), machine acceptance measurement and gap cleaning in the injection area for magnet protection, and will be tested for fast beam stacking for doubling the proton flux on the NuMI production target. The systems work reliably and cost much less than a resistive barrier rf system. Comparison with a similar system built at KEK reveals many similarities and also some important differences. This work is partially funded by the US-Japan collaborative agreement.
Date: July 1, 2006
Creator: Chou, W.; Wildman, D.; /Fermilab; Takagi, A. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Summary of the Optics, IR, Injection, Operations, Reliability and Instrumentation Working Group

Description: The facilities reported on are all in a fairly mature state of operation, as evidenced by the very detailed studies and correction schemes that all groups are working on. First- and higher-order aberrations are diagnosed and planned to be corrected. Very detailed beam measurements are done to get a global picture of the beam dynamics. More than other facilities the high-luminosity colliders are struggling with experimental background issues, mitigation of which is a permanent challenge. The working group dealt with a very wide rage of practical issues which limit performance of the machines and compared their techniques of operations and their performance. We anticipate this to be a first attempt. In a future workshop in this series, we propose to attempt more fundamental comparisons of each machine, including design parameters. For example, DAPHNE and KEKB employ a finite crossing angle. The minimum value of {beta}*{sub y} attainable at KEKB seems to relate to this scheme. Effectiveness of compensation solenoids and turn-by-turn BPMs etc. should be examined in more detail. In the near future, CESR-C and VEPP-2000 will start their operation. We expect to hear important new experiences from these machines; in particular VEPP-2000 will be the first machine to have adopted round beams. At SLAC and KEK, next generation B Factories are being considered. It will be worthwhile to discuss the design issues of these machines based on the experiences of the existing factory machines.
Date: April 20, 2012
Creator: Wienands, U.; /SLAC; Funakoshi, Y. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Suppression of Beam-Ion Instability in Electron Rings with Multi-Bunch Train Beam Fillings

Description: The ion-caused beam instability in the future light sources and electron damping rings can be serious due to the high beam current and ultra-small emittance of picometer level. One simple and effective mitigation of the instability is a multi-bunch train beam filling pattern which can significantly reduce the ion density near the beam, and therefore reduce the instability growth rate up to two orders of magnitude. The suppression is more effective for high intensity beams with low emittance. The distribution and the field of trapped ions are benchmarked to validate the model used in the paper. The wake field of ion-cloud and the beam-ion instability is investigated both analytically and numerically. We derived a simple formula for the build-up of ion-cloud and instability growth rate with the multi-bunch-train filling pattern. The ion instabilities in ILC damping ring, SuperKEKB and SPEAR3 are used to compare with our analyses. The analyses in this paper agree well with simulations.
Date: August 18, 2011
Creator: Wang, L.; Cai, Y.; Raubenheimer, T.O.; /SLAC; Fukuma, H. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Three dimensional FEM quench simulations of superconducting strands

Description: The detailed phenomena in quench starting of Nb{sub 3}Sn strands are simulated in 3-D and in time using ANSYS and FEMLAB programs. The current sharing between the superconductor and copper stabilizer in strands at the beginning of a quench was studied and displayed in time. The differences in copper configuration and RRR value of copper were found to have large effect to the stability and quench propagation velocity. The MPZ theory was found to be effective for 3D multifilament situation.
Date: September 1, 2005
Creator: Yamada, Ryuji; /Fermilab; Wake, Masayoshi & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Magnetization anomaly of Nb3Al strands and instability of Nb3Al Rutherford cables

Description: Using a Cu stabilized Nb{sub 3}Al strand with Nb matrix, a 30 meter long Nb{sub 3}Al Rutherford cable was made by a collaboration of Fermilab and NIMS. Recently the strand and cable were tested. In both cases instability was observed at around 1.5 Tesla. The magnetization of this Nb{sub 3}Al strand was measured first using a balanced coil magnetometer at 4.2 K. Strands showed an anomalously large magnetization behavior around at 1.6 T, which is much higher than the usual B{sub c2} {approx} 0.5 Tesla (4.2 K) of Nb matrix. This result is compared with the magnetization data of short strand samples using a SQUID magnetometer, in which a flux-jump signal was observed at 0.5 Tesla, but not at higher field. As a possible explanation for this magnetization anomaly, the interfilament coupling through the thin Nb films in the strands is suggested. The instability problem observed in low field tests of the Nb{sub 3}Al Rutherford cables is attributed to this effect.
Date: August 1, 2006
Creator: Yamada, Ryuji; /Fermilab; Kikuchi, Akihiro; Lab, /Tsukuba Magnet; Wake, Masayoshi & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

The Silicon Detector (SiD) And Linear Collider Detector R&D in Asia And North America

Description: In Asia and North America research and development on a linear collider detector has followed complementary paths to that in Europe. Among the developments in the US has been the conception of a detector built around silicon tracking, which relies heavily on a pixel (CCD) vertex detector, and employs a silicon tungsten calorimeter. Since this detector is quite different from the TESLA detector, we describe it here, along with some of the sub-system specific R&D in these regions.
Date: August 11, 2005
Creator: Brau, J.E.; U., /Oregon; Breidenbach, M.; /SLAC; Fujii, Y. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Fabrication Technologies of the High Gradient Accelerator Structures at 100MV/M Range

Description: A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of < 5 x 10{sup -7}/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed.
Date: July 3, 2012
Creator: Wang, Juwen; /SLAC; Lewandowski, James; /SLAC; Van Pelt, John; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Emittance Preservation in the International Linear Collider Ring to Main Linac Transfer Line

Description: The very small vertical beam emittance in the International Linear Collider (ILC) can be degraded by dispersion, xy coupling, transverse wakefields, and time-varying transverse fields introduced by elements with misalignments, strength errors, xy rotation errors, or yz rotation errors in the Ring to Main Linac (RTML) transfer line. We present a plan for emittance preservation in this beamline which uses local, quasi-local, and global correction schemes. Results of simulations of the emittance preservation algorithm are also presented and discussed.
Date: June 27, 2007
Creator: Tenenbaum, P.; /SLAC; Latina, A.; /CERN; Smith, J.C.; /Cornell U., CLASSE et al.
Partner: UNT Libraries Government Documents Department

Bunch Length Measurements at the ATF Damping Ring in April 2000

Description: We want to accurately know the energy spread and bunch length dependence on current in the ATF damping ring. One reason is to know the strength of the impedance: From the energy spread measurements we know whether or not we are above the threshold to the microwave instability, and from the energy spread and bunch length measurements we find out the extent of potential-well bunch lengthening (PWBL). Another reason for these measurements is to help in our understanding of the intra-beam scattering (IBS) effect in the ATF. The ATF as it is now, running below design energy and with the wigglers turned off, is strongly affected by IBS. To check for consistency with IBS theory of, for example, the measured vertical beam size, we need to know all dimensions of the beam, including the longitudinal one. But beyond this practical reason for studying IBS, IBS is currently a hot research topic at many accelerators around the world (see e.g. Ref. [1]), and the effect in actual machines is not well understood. Typically, when comparing theory with measurements fudge factors are needed to get agreement (see e.g. Ref. [1]). With its strong IBS effect, the ATF is an ideal machine for studying IBS, and an indispensable ingredient for this study is a knowledge of the longitudinal phase space of the beam. The results of earlier bunch lengthening measurements in the ATF can be found in Refs. [2]-[4]. Measurements of current dependent effects, especially bunch length measurements using a streak camera, can be difficult to perform accurately. For example, space charge in the camera itself can lead to systematic errors in the measurement results. It is important the results be accurate and reproducible. In the measurements of both December 1998[3] and December 1999[4], by using light filters, the authors first checked that ...
Date: December 19, 2005
Creator: Bane, K.L.F.; /SLAC; Naito, T.; Okugi, T.; Urakawa, J. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

Cavity BPM with Dipole-Mode-Selective Coupler

Description: In this paper, we present a novel position sensitive signal pickup scheme for a cavity BPM. The scheme utilizes the H-plane of the waveguide to couple magnetically to the side of the cavity, which results in a selective coupling to the dipole mode and a total rejection of the monopole mode. This scheme greatly simplifies the BPM geometry and relaxes machining tolerances. We will present detailed numerical studies on such a cavity BPM, analyze its resolution limit and tolerance requirements for a nanometer resolution. Finally present the measurement results of a X-band prototype.
Date: June 21, 2006
Creator: Li, Zenghai; Johnson, Ronald; Smith, Stephen R.; /SLAC; Naito, Takashi; /KEK, Tsukuba et al.
Partner: UNT Libraries Government Documents Department

Disruption of Particle Detector Electronics by Beam Generated EMI

Description: The possibility that radio frequency beam generated electromagnetic interference (EMI) could disrupt the operation of particle detector electronics has been of some concern since the inception of short pulse electron colliders more than 30 years ago [1]. Some instances have been reported where this may have occurred but convincing evidence has not been available. This possibility is of concern for the International Linear Collider (ILC). We have conducted test beam studies demonstrating that electronics disruption does occur using the vertex detector electronics (VXD) from the SLD detector which took data at the SLC at SLAC. We present the results of those tests, and we describe the need for EMI standards for beam and detector instrumentation in the IR region at the ILC.
Date: June 27, 2007
Creator: Bower, G.; /SLAC; Sugimoto, Y.; /KEK, Tsukuba; Sinev, N.; U., /Oregon et al.
Partner: UNT Libraries Government Documents Department

Status of High Power Tests of Normal Conducting Single-Cell Structures

Description: We report the results of ongoing high power tests of single-cell standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the maximum gradient possibilities for normal-conducting rf powered particle beam accelerators. The test setup consists of reusable mode launchers and short test structures powered by SLACs XL-4 klystron. The mode launchers and structures were manufactured at SLAC and KEK and tested at the SLAC klystron test laboratory.
Date: November 4, 2011
Creator: Dolgashev, V.A.; Tantawi, S.G.; /SLAC; Higashi, Y.; Higo, T. & /KEK, Tsukuba
Partner: UNT Libraries Government Documents Department

A Perfect Electrode to Suppress Secondary Electrons inside the Magnets

Description: An electron cloud due to multipacting in the positron ring of B-factories and the damping ring of the International Linear Collider (ILC) is one of the main concerns. The electron cloud in the drift region can be suppressed by a solenoid. However, the solenoid doesn't work inside a magnet. Numerical studies show that there is strong multipacting in a dipole magnet of a B-factory positron ring. Electrons also can be trapped inside quadrupole and sextupole magnets. The electron cloud from dipole magnets and wigglers in the positron damping ring of the ILC gives a critical limitation on the choice of a circumference of the damping ring, which directly results in a choice of two 6 km rings as the baseline for the positron damping ring. Various electrodes have been studied using the program CLOUDLAND. Our studies show that a wire type of the electrode with a few hundred voltages works perfectly to kill the secondary electrons inside various magnets.
Date: July 19, 2006
Creator: Wang, L.; /SLAC; Fukuma, H.; Kurokawa, S.; /KEK, Tsukuba; Pivi, M. et al.
Partner: UNT Libraries Government Documents Department

Progress towards of a superconducting traveling wave accelerating structure

Description: In the ILC project the required accelerating gradient is higher than 30 MeV/m. For current technology the maximum acceleration gradient in SC structures is determined mainly by the value of the surface RF magnetic field. In order to increase the gradient, the RF magnetic field is distributed homogeneously over the cavity surface (low-loss structure), and coupling to the beam is improved by introducing aperture 'noses' (reentrant structure). These features allow gradients in excess of 50 MeV/m to be obtained for a singe-cell cavity. Further improvement of the coupling to the beam may be achieved by using a TW SC structure with small phase advance per cell. We have demonstrated that an additional gradient increase by up to 46% may be possible if a {pi}/2 TW SC structure is employed. However, a TW SC structure requires a SC feedback waveguide to return the few GW of circulating RF power from the structure output back to the structure input. The test cavity with the feedback is designed to demonstrate the possibility of achieving a significantly higher gradient than existing SC structures.
Date: June 1, 2007
Creator: Yakovlev, V.; U., /Yale; Avrakhov, P.; Kanareykin, A.; Kazakov, S.; /KEK, Tsukuba et al.
Partner: UNT Libraries Government Documents Department