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Optimization of the CLIC Baseline Collimation System

Description: Important efforts have recently been dedicated to the improvement of the design of the baseline collimation system of the Compact Linear Collider (CLIC). Different aspects of the design have been optimized: the transverse collimation depths have been recalculated in order to reduce the collimator wakefield effects while maintaining a good efficiency in cleaning the undesired beam halo; the geometric design of the spoilers have also been reviewed to minimize wakefields; in addition, the optics design have been polished to improve the collimation efficiency. This paper describes the current status of the CLIC collimation system after this optimization.
Date: July 6, 2012
Creator: Resta-Lopez, Javier; /Oxford U., JAI; Angal-Kalinin, Deepa; /Daresbury; Fernandez-Hernando, Juan; /Daresbury et al.
Partner: UNT Libraries Government Documents Department

Optimisation of An HHG-Seeded Harmonic Cascade FEL Design for the NLS Project

Description: Optimization studies of an HHG-seeded harmonic cascade FEL design for the UK's proposed New Light Source (NLS) facility are presented. Three separate FELs are planned to meet the requirements for continuous coverage of the photon energy range 50-1000 eV with variable polarization, 20 fs pulse widths and good temporal coherence. The design uses an HHG seed source tuneable from 50-100 eV to provide direct FEL seeding in this range, and one or two stage harmonic cascades to reach the higher photon energies. Studies have been carried out to optimize a harmonic cascade FEL operating at 1 keV; topics investigated include modulator configuration, seed power level and ef- fects of the HHG seed structure. FEL simulations using realistic electron beam distributions are presented and tolerance to increased emittance has been considered.
Date: June 25, 2012
Creator: Dunning, David; /Daresbury; Thompson, Neil; /Daresbury; Bartolini, Riccardo; /Oxford U., JAI et al.
Partner: UNT Libraries Government Documents Department

Polarization Analysis for Seeded FELs in a Crossed-Planar Undulator

Description: The crossed-planar undulator is a promising scheme for full polarization control in x-ray FELs. For SASE FELs, it has been shown a maximum degree of circular polarization of about 80% is achievable at fundamental wavelength just before saturation. In this paper, we study the effectiveness of a crossed undulator for a seeded x-ray FEL. The degree of circular polarization for both the fundamental and the harmonic radiation are considered. Simulations with realistic beam distributions show that a degree of circular polarization of over 90% and 80% is obtainable at the fundamental and 2nd harmonic frequencies, respectively.
Date: June 25, 2012
Creator: Geng, Huiping; /SLAC; Ding, Yuantao; /SLAC; Huang, Zhirong; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Superconducting magnet needs for the ILC

Description: The ILC Reference Design Report was completed early in February 2007. The Magnet Systems Group was formed to translate magnetic field requirements into magnet designs and cost estimates for the Reference Design. As presently configured, the ILC will have more than 13,000 magnetic elements of which more than 2300 will be based on superconducting technology. This paper will describe the major superconducting magnet needs for the ILC as presently determined by the Area Systems Groups, responsible for beam line design, working with the Magnet Systems Group. The superconducting magnet components include Main Linac quadrupoles, Positron Source undulators, Damping Ring wigglers, a complex array of Final Focus superconducting elements in the Beam Delivery System, and large superconducting solenoids in the e{sup +} and e{sup -} Sources, and the Ring to Main Linac lines.
Date: June 1, 2007
Creator: Tompkins, J.C.; Kashikhin, Vl.; /Fermilab; Parker, B.; /Brookhaven; Palmer, M.A. / et al.
Partner: UNT Libraries Government Documents Department

Beam Delivery WG Summary: Optics, Collimation & Background

Description: The presented paper partially summarizes the work of the Beam Delivery working group (WG4) at Snowmass, concentrating on status of optics, layout, collimation, and background. The strawman layout with 2 interaction regions was recommended at the first ILC workshop at KEK in November 2004. Two crossing-angle designs were included in this layout. The design of the ILC BDS has evolved since the first ILC workshop. The progress on the BDS design and extraction line design has been reviewed and the design issues were discussed during the optics and layout session at the Snowmass.
Date: January 20, 2006
Creator: Angal-Kalinin, D.; Jackson, F.; /Daresbury; Mokhov, N.V.; /Fermilab; Kuroda, S. et al.
Partner: UNT Libraries Government Documents Department

The 2mrad horizontal crossing angle IR layout for a TeV ILC

Description: The current status of the 2mrad crossing angle layout for the ILC is reviewed. The scheme developed in the UK and France is described and the performance discussed for a TeV machine. Secondly, the scheme developed at SLAC and BNL is then studied and modified for a TeV machine. We find that both schemes can handle the higher energy beam with modifications, and share many common features.
Date: July 27, 2005
Creator: Appleby, R.; Angal-Kalinin, D.; /Daresbury; Bambade, P.; Mouton, B.; /Orsay, LAL et al.
Partner: UNT Libraries Government Documents Department

ILC Beam delivery WG summary: Optics, collimation and background

Description: The paper summarizes the work of the Beam Delivery working group (WG4) at Snowmass 2005 workshop, focusing on status of optics, layout, collimation and detector background. The strawman layout with two interaction regions was recommended at the first ILC workshop at KEK in November 2004. Two crossing-angle designs were included in this layout. The design of the ILC BDS has evolved since the first ILC workshop. The progress on the BDS design including the collimation system, and extraction line design have been reviewed and the design issues were discussed during the WG4 sessions at the Snowmass, and are described in this paper.
Date: July 1, 2006
Creator: Angal-Kalinin, D.; Jackson, F.; /Daresbury; Mokhov, N.V.; /Fermilab; Kuroda, S. et al.
Partner: UNT Libraries Government Documents Department

Power coupler for the ILC crab cavity

Description: The ILC crab cavity will require the design of an appropriate power coupler. The beam-loading in dipole mode cavities is considerably more variable than accelerating cavities, hence simulations have been performed to establish the required external Q. Simulations of a suitable coupler were then performed and were verified using a normal conducting prototype with variable coupler tips.
Date: June 1, 2007
Creator: Burt, G.; Dexter, A.; Jenkins, R.; U., /Lancaster; Beard, C.; Goudket, P. et al.
Partner: UNT Libraries Government Documents Department

Measurements of Collimator Wakefields at End Station A

Description: The angular deflection of a 28.5 GeV electron beam passing off-axis between the jaws of a collimator, generating a transverse wakefield, were measured in End Station A (ESA) at SLAC. In total, fifteen different configurations of collimator geometry and material were tested: some were chosen for compatibility with previous measurements while others served to study the effect of geometry and taper angles (geometrical contribution to the wakefield) and the effect of the material resistivity (resistive contribution) to the imparted kick. This paper summarises the last update of preliminary experimental results before they are finalised. The reconstructed kick factor is compared to analytical calculations and simulations.
Date: November 1, 2011
Creator: Fernandez-Hernando, J.L.; /Daresbury; Molloy, S.; /SLAC; Smith, J.D.A.; Tech., /Cockcroft Inst. Accel. Sci. et al.
Partner: UNT Libraries Government Documents Department

Copper Prototype Measurements of the HOM, LOM and SOM Couplers for the ILC Crab Cavity

Description: The ILC Crab Cavity is positioned close to the IP and delivered luminosity is very sensitive to the wakefields induced in it by the beam. A set of couplers were designed to couple to and damp the spurious modes of the crab cavity. As the crab cavity operates using a dipole mode, it has different damping requirements from an accelerating cavity. A separate coupler is required for the monopole modes below the operating frequency of 3.9 GHz (known as the LOMs), the opposite polarization of the operating mode (the SOM), and the modes above the operating frequency (the HOMs). Prototypes of each of these couplers have been manufactured out of copper and measured attached to an aluminum nine cell prototype of the cavity and their external Q factors were measured. The results were found to agree well with numerical simulations.
Date: June 23, 2008
Creator: Burt, G.; Ambattu, P.K.; Dexter, A.C.; U., /Lancaster; Bellantoni, L.; /Fermilab et al.
Partner: UNT Libraries Government Documents Department

Copper Prototype Measurements of the HOM, LOM And SOM Couplers for the ILC Crab Cavity

Description: The ILC Crab Cavity is positioned close to the IP and delivered luminosity is very sensitive to the wakefields induced in it by the beam. A set of couplers were designed to couple to and damp the spurious modes of the crab cavity. As the crab cavity operates using a dipole mode, it has different damping requirements from an accelerating cavity. A separate coupler is required for the monopole modes below the operating frequency of 3.9 GHz (known as the LOMs), the opposite polarization of the operating mode (the SOM), and the modes above the operating frequency (the HOMs). Prototypes of each of these couplers have been manufactured out of copper and measured attached to an aluminum nine cell prototype of the cavity and their external Q factors were measured. The results were found to agree well with numerical simulations.
Date: November 4, 2011
Creator: Burt, G.; Ambattu, P.K.; Dexter, A.C.; U., /Lancaster; Bellantoni, L.; /Fermilab et al.
Partner: UNT Libraries Government Documents Department

Optics of the ILC Extraction Line for 2mrad Crossing Angle

Description: The ILC extraction line for 2 mrad crossing angle is under development by the SLAC-BNL-UK-France task force collaboration. This report describes the progress in the 2 mrad optics design which includes the changes to the final focus doublet, the complete optics for the extraction diagnostics, and the changes to the sextupole and collimation systems. The results of disrupted beam tracking simulations are presented.
Date: January 5, 2006
Creator: Nosochkov, Y.; Moffeit, K.; Seryi, A.; Spencer, C.; Woods, M.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Design of Extraction Line Optics for the ILCInteraction Regions with 20 mrad and 2 mrad Crossing Angles

Description: The studies of the ILC extraction line design have been carried out by the SLAC-BNL-UK-France task force collaboration. In this paper, we describe two options of the extraction optics for the 20 mrad horizontal crossing angle in the Interaction Region (IR), and one option of the 2 mrad extraction optics. The main functions of the extraction line are to transport the primary beam and beamstrahlung photons to dumps with acceptable beam loss, and to provide the necessary optics for beam diagnostics. The presented 20 mrad and 2 mrad optics are designed for up to 1 TeV and 0.5 TeV Center of Mass (CM) energy, respectively. The upgrade of this 2 mrad design to 1 TeV CM and a separate version of the 2 mrad design are presented in a separate report [1].
Date: July 27, 2005
Creator: Nosochkov, Y.; Moffeit, K.; Seryi, A.; Spencer, C.; Wood, M.; /SLAC et al.
Partner: UNT Libraries Government Documents Department

Shell model calculations at superdeformed shapes

Description: Spectroscopy of superdeformed nuclear states opens up an exciting possibility to probe new properties of the nuclear mean field. In particular, the unusually deformed atomic nucleus can serve as a microscopic laboratory of quantum-mechanical symmetries of a three dimensional harmonic oscillator. The classifications and coupling schemes characteristic of weakly deformed systems are expected to be modified in the superdeformed world. The superdeformed'' symmetries lead to new quantum numbers and new effective interactions that can be employed in microscopic calculations. New classification schemes can be directly related to certain geometrical properties of the nuclear shape. 63 refs., 7 figs.
Date: January 1, 1991
Creator: Nazarewicz, W. (Joint Inst. for Heavy Ion Research, Oak Ridge, TN (USA)); Dobaczewski, J. (Warsaw Univ. (Poland)) & Van Isacker, P. (Daresbury Lab. (UK))
Partner: UNT Libraries Government Documents Department

Real time visualization of Quantum Molecular Dynamics

Description: this demonstration displays results of a Quantum Molecular Dynamics (QMD) simulation of the metal cluster Li[sub 6] running on the Intel Touchstone Delta at Caltech.
Date: November 1, 1992
Creator: Harrison, R.J.; Thornton, E. (Pacific Northwest Lab., Richland, WA (United States)); Koutecky, V.; Janza, A.; Wiechert, M. (Berlin Univ. (Germany)); Fantucci, P. (Milan Univ. (Italy)) et al.
Partner: UNT Libraries Government Documents Department

Measurements of the Transverse Wakefields Due to Varying Collimator Characteristics

Description: We report on measurements of the transverse wakefields induced by collimators of differing characteristics. An apparatus allowing the insertion of different collimator jaws into the path of a beam was installed in End Station A (ESA) in SLAC. Eight comparable collimator geometries were designed, including one that would allow easy comparison with previous results, and were installed in this apparatus. Measurements of the beam kick due to the collimator wakefields were made with a beam energy of 28.5 GeV, and beam dimensions of 100 microns vertically and a range of 0.5 to 1.5 mm longitudinally. The trajectory of the beam upstream and downstream of the collimator test apparatus was determined from the outputs of ten BPMs (four upstream and six downstream), thus allowing a measurement of the angular kick imparted to the beam by the collimator under test. The transverse wakefield was inferred from the measured kick. The different aperture designs, data collection and analysis, and initial comparison to theoretical and analytic predictions are presented here.
Date: July 6, 2007
Creator: Molloy, S.; Seletskiy, Sergei; Woods, Mike; /SLAC; Smith, Jonathan David Andrew; Tech., /Cockcroft Inst. Accel. Sci. et al.
Partner: UNT Libraries Government Documents Department

Status of the ILC Crab Cavity Development

Description: The International Linear Collider (ILC) will require two dipole cavities to 'crab' the electron and positron bunches prior to their collision. It is proposed to use two 9 cell SCRF dipole cavities operating at a frequency of 3.9 GHz, with a transverse gradient of 3.8MV/m in order to provide the required transverse kick. Extensive numerical modelling of this cavity and its couplers has been performed. Aluminium prototypes have been manufactured and tested to measure the RF properties of the cavity and couplers. In addition single cell niobium prototypes have been manufactured and tested in a vertical cryostat. The International Collider (ILC) [1] collides bunches of electrons and positrons at a crossing angle of 14 mrad. The angle between these bunches causes a loss in luminosity due to geometric effects [2]. The luminosity lost from this geometric effect can be recovered by rotating the bunches into alignment prior to collision. One possible method of rotating the bunches is to use a crab cavity [3]. A crab cavity is a transverse defecting cavity, where the phase of the cavity is such that the head and tail of the bunch receive equal and opposite kicks. As the bunches are only 500 nm wide in the horizontal plane, the cavity phase must be strictly controlled to avoid the bunch centre being deflected too much. In order to keep the phase stability within the required limits it is required that the cavity be superconducting to avoid thermal effects in both the cavity and its RF source. At the location of the crab cavity in the ILC there is only 23 cm separation between the centre of the cavity and the extraction line, hence the cavity must be small enough to fit in this space. This, along with the difficulty of making high frequency SRF components, ...
Date: October 20, 2011
Creator: Burt, G.; Dexter, A.; Tech., /Cockcroft Inst. Accel. Sci.; Beard, C.; Goudket, P.; McIntosh, P. et al.
Partner: UNT Libraries Government Documents Department

A Study of Emittance Measurement at the ILC

Description: The measurement of the International Linear Collider (ILC) emittance in the ILC beam delivery system (BDS) is simulated. Estimates of statistical and machine-related errors are discussed and the implications for related diagnostics R&D are inferred. A simulation of the extraction of the laser-wire Compton signal is also presented.
Date: April 16, 2007
Creator: Blair, G.A.; Agapov, I.V.; Carter, J.; Deacon, L.; /Royal Holloway, U. of London; Angal-Kalinin, D.A.K. et al.
Partner: UNT Libraries Government Documents Department

Material Damage Test for ILC Collimators

Description: Simulations were completed to determine the energy deposition of an ILC bunch using FLUKA, Geant4 and EGS4 to a set of different spoiler designs. These shower simulations were used as inputs to thermal and mechanical studies using ANSYS. This paper presents a proposal to optimize the material choice and mechanical design of ILC spoilers jaws using ATF and benchmark the energy deposition simulations and the ANSYS studies giving the researchers valuable data which will help achieve a definitive ILC spoiler design.
Date: August 14, 2007
Creator: Fernandez Hernando, J.L.; /Daresbury; Blair, G.A.; Boogert, S.T.; /Royal Holloway, U. of London; Ellwood, G.E. et al.
Partner: UNT Libraries Government Documents Department

The effect of scandium on the phase stability of Al sub 3 Nb and Al sub 3 Zr

Description: A series of Al-25 (Nb,Sc), at. %, and Al-25 (Zr,Sc), at. %, alloy buttons were arc-cast in argon and homogenized for 2 h in vacuum at temperatures ranging from 1473 to 1573K. X-ray powder-diffraction indicated that almost all the Nb in Al-25 Nb (DO{sub 22}) had to be replaced by Sc in order to obtain the L1{sub 2} structure. In the case of Al{sub 3}Zr much less Sc was required -- the single phase L1{sub 2} composition is approximately Al-16Zr-8Sc. Recent calculations show that once the tetragonality is properly included in the phase stability of the Tri-Aluminide transition-metal binary alloys can be understood in terms of their electronic density of states. The dominating feature is a deep minimum in the density of states just below the major transition metal d-band peak. The exact position of the minimum changes with structure type (i.e., L1{sub 2}, DO{sub 22}, or DO{sub 23}, and with c/a). The alignment of the Fermi energy with the minimum appears to determine the equilibrium structure. The results of linearized-muffin-tin-orbital (LMTO) electronic structure calculations are compared to the rigid band model and checked against the experimentally determined phase boundaries. 5 refs., 5 figs., 1 tab.
Date: January 1, 1990
Creator: Nicholson, D.M.; Schneibel, J.H.; Shelton, W.A. (Oak Ridge National Lab., TN (USA)); Sterne, P. (Lawrence Livermore National Lab., CA (USA)) & Temmerman, W.M. (Daresbury Lab. (UK))
Partner: UNT Libraries Government Documents Department

Performance of the FONT3 Fast Analogue Intra-Train Beam-Based Feedback System at ATF

Description: We report results of beam tests of the FONT3 intra-train position feedback system prototype at the Accelerator Test Facility (ATF) at KEK. The feedback system incorporates a novel beam position monitor (BPM) processor with latency below 5 nanoseconds, and a kicker driver amplifier with similar low latency. The 56 nanosecond-long bunchtrain in the ATF extraction line was used to test the prototype feedback system. The achieved latency of 23ns provides a demonstration of intra-train feedback on very short timescales relevant even for the CLIC Linear Collider design.
Date: April 16, 2007
Creator: Burrows, P.; /Queen Mary, U. of London; Christian, G.B.; Hartin, A.F.; Dabiri Khah, H.; White, G.R. et al.
Partner: UNT Libraries Government Documents Department

Study of Abnormal Vertical Emittance Growth in ATF Extraction Line

Description: Since several years, the vertical beam emittance measured in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, that will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line, is significantly larger than the emittance measured in the DR itself, and there are indications that it grows rapidly with increasing beam intensity. This longstanding problem has motivated studies of possible sources of this anomalous emittance growth. One possible contribution is non-linear magnetic fields in the extraction region experimented by the beam while passing off-axis through magnets of the DR during the extraction process. In this paper, simulations of the emittance growth are presented and compared to observations. These simulations include the effects of predicted non-linear field errors in the shared DR magnets and orbit displacements from the reference orbit in the extraction region. Results of recent measurements using closed orbit bumps to probe the relation between the extraction trajectory and the anomalous emittance growth are also presented.
Date: November 4, 2011
Creator: Alabau, M.; Faus-Golfe, A.; /Valencia U., IFIC; Alabau, M.; Bambade, P.; Brossard, J. et al.
Partner: UNT Libraries Government Documents Department

The SuperB Accelerator: Overview and Lattice Studies

Description: SuperB aims at the construction of a very high luminosity (10{sup 36} cm{sup -2} s{sup -1}) asymmetric e{sup +}e{sup -} Flavour Factory, with possible location at the campus of the University of Rome Tor Vergata, near the INFN Frascati National Laboratory. In this paper the basic principles of the design and details on the lattice are given. SuperB is a new machine that can exploit novel very promising design approaches: (1) large Piwinski angle scheme will allow for peak luminosity of the order of 10{sup 36} cm{sup -2} s{sup -1}, well beyond the current state-of-the-art, without a significant increase in beam currents or shorter bunch lengths; (2) 'crab waist' sextupoles will be used for suppression of dangerous resonances; (3) the low beam currents design presents reduced detector and background problems, and affordable operating costs; (4) a polarized electron beam can produce polarized {tau} leptons, opening an entirely new realm of exploration in lepton flavor physics. SuperB studies are already proving useful to the accelerator and particle physics communities. The principle of operation is being tested at DAFNE. The baseline lattice, based on the reuse of all PEP-II hardware, fits in the Tor Vergata University campus site, near Frascati. A CDR is being reviewed by an International Review Committee, chaired by J. Dainton (UK). A Technical Design Report will be prepared to be ready by beginning of 2010.
Date: November 22, 2011
Creator: Biagini, M.E.; Boni, R.; Boscolo, M.; Drago, A.; Guiducci, S.; Preger, M. et al.
Partner: UNT Libraries Government Documents Department