44018991
Comparison of ILC fast beam-beam feedback performance in the e-e- and e+e- modes of operation
Several feedback loops are required in the beam delivery system (BDS) of the international linear collider (ILC) to preserve the luminosity in the presence of dynamic imperfections. Realistic simulations have been carried out to study the performance of the beam-beam deflection based fast feedback system, for both e<sup>+</sup>e<sup>-</sup> and e<sup>-</sup>e<sup>-</sup> modes of operation. The beam-beam effects in the e<sup>-</sup>e<sup>-</sup> collisions make both the luminosity and the deflections more sensitive to offsets at the interaction point (IP) than in the case of the e<sup>+</sup>e<sup>-</sup> collisions. This reduces the performance of the feedback system in comparison to the standard e<sup>+</sup>e<sup>-</sup> collisions, and may require a different beam parameter optimization.
56333052
Benchmarking/Crosschecking DFS in the ILC Main Linac
In an effort to compare beam dynamics and create a ''benchmark'' for Dispersion Free Steering (DFS) a comparison was made between different ILC simulation programs while performing DFS. This study consisted of three parts. First, a simple betatron oscillation was tracked through each code. Secondly, a set of component misalignments and corrector settings generated from one program was read into the others to confirm similar emittance dilution. Thirdly, given the same set of component misalignments DFS was performed independently in each program and the resulting emittance dilution was compared. Performance was found to agree exceptionally well in all three studies.
1533964
Beam dynamics studies in the CLIC Injector LINAC
The CLIC Injector Linac has to accelerate both electron and positron main beams from 200 MeV up to 2.42 GeV prior to their injection into the pre-damping rings. Its 26 accelerating structures operate at 1.5 GHz, with a loaded gradient of 17 MV/m. A FODO lattice that wraps the accelerating structures at the beginning of the linac, followed by a succession of triplet lattices between the accelerating structures, is proposed. The large normalized transverse emittance (9200 mm.mrad rms), bunch length (5 mm rms) and energy spread (7 MeV rms) of the e+ beam set constraints on the linac, in order to reach acceptable characteristics at 2.42 GeV for the injection into the pre- damping ring. The use of a bunch compressor at the linac entrance is an option in order to achieve good performance in both the longitudinal and transverse phase spaces. Tracking studies of both electron and positron beams in the linac have been performed and are presented.
14351447
Luminosity Performance Studies of Linear Colliders with Intra-train Feedback Systems
The design luminosity for the future linear colliders is very demanding and challenging. Beam-based feedback systems will be required to achieve the necessary beam-beam stability and steer the two beams into collision. In particular we have studied the luminosity performance improvement by intra-train beam-based feedback systems for position and angle corrections at the interaction point. We have set up a simulation model which introduces different machine imperfections and can be applied to both the International Linear Collider (ILC) and the Compact Linear Collider (CLIC).
201640423
PLACET BASED START-TO-END SIMULATIONS OF THE ILC WITH INTRA-TRAIN FAST FEEDBACK SYSTEM
Integrated simulations are important to assess the reliability of the luminosity performance of the future linear colliders. In this paper we present multi-bunch tracking simulation results for the International Linear Collider (ILC) from the start of the linac to the interaction point. The tracking along the linac and the beam delivery system is done using the code PLACET. This code allows us to introduce cavity wakefield effects, element misalignment errors and ground motion. Static beam based alignment of the linac is also considered. The luminosity and beambeam parameters are calculated using the code GUINEAPIG. In the framework of the Feedback On Nano-second Timescales (FONT) project, we describe and simulate an updated fast intra-train feedback system in order to correct for luminosity degradation mainly due to high frequency ground motion.
115089069
FAILURE STUDIES AT THE COMPACT LINEAR COLLIDER : MAIN LINAC AND BEAM DELIVERY SYSTEM
The proposed Compact Linear Collider (CLIC) is based on a two-beam acceleration scheme. The energy of two high-intensity, low-energy drive beams is extracted and transferred to two low-intensity, highenergy main beams. The CERN Technology Department Machine protection and electrical integrity group has the mission to develop and maintain the systems to protect machine components from damage caused by ill controlled conditions. Various failure scenarios were studied and the potential damage these failures could cause to the machine structures was estimated. In this paper, first results of the beam response to kick induced failures in the main LINAC and in the beam delivery system (BDS) sections are presented together with possible collimator damage scenarios. Presented at: 3rd International Particle Accelerator Conference 2012, New Orleans, LA, USA, 20 25 May 2012 Geneva, Switzerland Date 20/05/2012 CLIC – Note – 980 FAILURE STUDIES AT THE COMPACT LINEAR COLLIDER: MAIN LINAC AND BEAM DELIVERY SYSTEM C. O. Maidana, A. Latina, M. Jonker, CERN, Geneva, Switzerland Abstract The proposed Compact Linear Collider (CLIC) is based on a two-beam acceleration scheme. The energy of two high-intensity, low-energy drive beams is extracted and transferred to two low-intensity, high-energy main beams. The CERN Technology Department Machine protection and electrical integrity group has the mission to develop and maintain the systems to protect machine components from damage caused by ill controlled conditions. Various failure scenarios were studied and the potential damage these failures could cause to the machine structures was estimated. In this paper, first results of the beam response to kick induced failures in the main LINAC and in the beam delivery system (BDS) sections are presented together with possible collimator damage scenarios.The proposed Compact Linear Collider (CLIC) is based on a two-beam acceleration scheme. The energy of two high-intensity, low-energy drive beams is extracted and transferred to two low-intensity, high-energy main beams. The CERN Technology Department Machine protection and electrical integrity group has the mission to develop and maintain the systems to protect machine components from damage caused by ill controlled conditions. Various failure scenarios were studied and the potential damage these failures could cause to the machine structures was estimated. In this paper, first results of the beam response to kick induced failures in the main LINAC and in the beam delivery system (BDS) sections are presented together with possible collimator damage scenarios. CLIC AND THE TWO-BEAM CONCEPT The Compact Linear Collider (CLIC) is a 50 km long high energy e/e accelerator concept working with 12 Ghz (X-band) room temperature radiofrequency cavities. To accomplish the desired 3 TeV collision energy, an accelerating gradient of 100 MV/m will be used. Using the two-beam accelerating concept, a high current electron beam (drive beam) runs parallel to the main beam line. The drive beam is decelerated in power extraction and transfer structures (PETS) which generate the RF power for the lower current high energy main beam. The two main LINACs, one for positrons and one for electrons, accelerate the beams from an initial energy of 9 GeV to the final value of 1.5 TeV over a length of ~21 km. The main LINAC optics consists of twelve FODO lattice sectors with a phase advance of 72 degrees per cell throughout the main LINACs. There are four different types of quadrupole magnets of different length (0.35 m, 0.85 m, 1.35 and 1.85 m), same aperture (0.004 m beam pipe) and same field gradient (200 T/m) [1]. A layout of the two-beam module is presented in Fig. 1. The quadrupole spacing is constant in any particular sector but varies from sector to sector [1]. Other main LINAC specifications can be found on Table 1. The Beam Delivery Systems (BDS) start at the exit of the Main LINACs. Each BDS consists of 206 dipoles, 70 quadrupoles and 18 sextupoles (while higher order n-pole magnets are considered) [1]. The BDS is responsible for transporting the beams, protecting the beam line and detector against mis-steered beams, removing the beam halo, focusing them to the required sizes ( x = 45 nm, y = 1 nm) and bringing them into collision. The BDS can be divided in three regions, named: the diagnostics region, the energy and betatron collimation region and the final focus region. The BDS layout can be seen in Fig. 2. Table 1: Main LINAC Specifications Parameter Symbol Value Energy at injection Einj 9 GeV Energy at extraction Eext,linac 1.5 TeV Particles/bunch N 3.72 10 Bunch length inj 44 m
122984783
Fusion suppression in mass-asymmetric reactions leading to Ra compound nuclei
Near-barrier excitation functions have been measured for evaporation-residue production and fission in the 12C + 204,206,208Pb and 48Ca + 168,170Er systems that lead to the compound nuclei 216,218,220Ra*. A Pronounced suppression of evaporation-residue production is observed for the more symmetric combinations, 48Ca + 168,170Er. We relate this to the significant quasifission components already observed for these systems.
54666701
Multinucleon transfer reactions in closed-shell nuclei
Multinucleon transfer reactions in $^{40}$Ca+$^{96}$Zr and $^{90}$Zr+$^{208}$Pb have been measured at energies close to the Coulomb barrier in a high resolution gamma-particle coincidence experiment. The large solid angle magnetic spectrometer PRISMA coupled to the CLARA gamma-array has been employed. Trajectory reconstruction has been applied for the complete identification of transfer products. Mass and charge yields, total kinetic energy losses, gamma transitions of the binary reaction partners, and comparison of data with semiclassical calculations are reported. Specific transitions in $^{95}$Zr populated in one particle transfer channels are discussed in terms of particle-phonon couplings. The gamma decays from states in $^{42}$Ca in the excitation energy region expected from pairing vibrations are also observed.
124130898
Study of the neutron-rich nucleus Si-36
Excited states of N=22 Si-36, populated in deep-inelastic processes produced by the interaction of a 215 MeV beam of S-36 ions with a Pb-208 target, were studied in the present work. gamma rays from the binary fragments detected using CLARA, an array of 25 Ge Clover detectors, were measured in coincidence with projectile-like fragments detected by PRISMA, a large solid angle magnetic spectrometer. Two new gamma-ray photopeaks at energies of 1442 and 842 keV were observed and tentatively assigned to the 4(+)-> 2(+) and 6(+)-> 4(+) transitions, respectively. The systematics of the level structures of N=22 isotones are presented, and a comparison is made of the behavior of Si, Mg, and S isotopes. The level structure of Si-36 is also compared with the results of sdpf shell model calculations.
123570790
Intruder configurations in neutron-rich P and S isotopes
Neutron-rich sdf-shell nuclei have attracted a great deal of international interest, both theoretically and experimentally. There is an increasing interest in using deep-inelastic reactions to obtain spectroscopic information about these exotic nuclei. New results obtained from two such experiments are presented here. The highly sensitive GASP array was used to measure the γ decays of previously unobserved yrast and near yrast states of 34P which were populated when 230 MeV 36S ions were incident on a thick target of 176Yb. In addition, a recent investigation of the spectroscopy of neutron-rich P and S isotopes has been undertaken with 215 MeV 36S ions incident on a thin target of 208Pb using the CLARA Ge detector array in conjunction with the PRISMA magnetic spectrometer. Preliminary results from this experiment are presented here.
27335793
Intruder negative-parity states of neutron-rich Si-33
This work was supported in part by the EPSRC (UK) and by the European Union under Contract No. RII3-CT-2004-506065. Five of us (D.O., M.B., A.H., K.K., and A.P.)acknowledge financial support from the EPSRC. Z.M.W acknowledges support from ORSAS and from the University of the West of Scotland. A.J. acknowledges financial supportfrom the Spanish Ministerio de Ciencia e Innovacion under Contract Nos. FPA2007-66069 and FPA2009-13377-C02-02. Zs.D. acknowledges the financial support from OTKA Project No. K68801.