436 research outputs found
COLLIMATION OPTIMISATION IN THE BEAM DELIVERY SYSTEM OF THE INTERNATIONAL LINEAR COLLIDER*
Abstract The collimation systems of the International Linear Collider (ILC) Beam Delivery System (BDS) must perform efficient removal of halo particles which lie outside the acceptable ranges of energy and spatial spread. An optimisation strategy based on earlier work is applied to the latest version of the BDS lattice. The resulting improvement in collimation performance is studied by halo tracking simulations, and the luminosity performance of the optimised lattice is also examined
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Material Damage Test for ILC Collimators
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
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Measurements of the Transverse Wakefields Due to Varying Collimator Characteristics
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
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Performance of the FONT3 Fast Analogue Intra-Train Beam-Based Feedback System at ATF
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
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Design of the ILC Prototype FONT4 Digital Intra-Train Beam-Based Feedback System
We present the design of the FONT4 digital intra-train beam position feedback system prototype and preliminary results of initial beam tests at the Accelerator Test Facility (ATF) at KEK. The feedback system incorporates a fast analogue beam position monitor (BPM) front-end signal processor, a digital feedback board, and a kicker driver amplifier. The short bunchtrain, comprising 3 electron bunches separated by c. 150ns, in the ATF extraction line was used to test components of the prototype feedback system
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Design of an Interaction Region with Head-On Collisions for the ILC
An interaction region (IR) with head-on collisions is considered as an alternative to the baseline configuration of the International Linear Collider (ILC) which includes two IRs with finite crossing-angles (2 and 20 mrad). Although more challenging for the beam extraction, the head-on scheme is favored by the experiments because it allows a more convenient detector configuration, particularly in the forward region. The optics of the head-on extraction is revisited by separating the e+ and e- beams horizontally, first by electrostatic separators operated at their LEP nominal field and then using a defocusing quadrupole of the final focus beam line. In this way the septum magnet is protected from the beamstrahlung power. Newly optimized final focus and extraction optics are presented, including a first look at post-collision diagnostics. The influence of parasitic collisions is shown to lead to a region of stable collision parameters. Disrupted beam and beamstrahlung photon losses are calculated along the extraction elements
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Technical Challenges for the Head-on Collisions and Extraction at the ILC
An interaction region with head-on collisions is considered as an alternative to the baseline ILC configuration. Progress in the final focus optics design includes engineered large bore superconducting final doublet magnets and their 3D magnetic integration in the detector solenoids. Progress on the beam separation optics is based on technical designs of electrostatic separator and special extraction quadrupoles. The spent beam extraction is realized by a staged collimation scheme relying on realistic collimators
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Observation of Polarized Positrons from an Undulator-Based Source
An experiment (E166) at the Stanford Linear Accelerator Center (SLAC) has demonstrated a scheme in which a multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with Geant4 simulations that include the dominant polarization-dependent interactions of electrons, positrons and photons in matter
RECENT DEVELOPMENTS ON ALICE (ACCELERATORS AND LASERS IN COMBINED EXPERIMENTS) AT DARESBURY LABORATORY
Abstract Progress made in ALICE (Accelerators and Lasers In Combined Experiments) commissioning and a summary of the latest experimental results are presented in this paper. After an extensive work on beam loading effects in SC RF booster and linac cavities' conditioning, ALICE can now operate in full energy recovery mode at a bunch charge of 40pC, a beam energy of 27.5MeV and train lengths of up to 100µs. This improved operation of the machine has resulted in generation of coherentlyenhanced broadband terahertz radiation with an energy of several tens of microjoules per pulse and in successful demonstration of the Compton Back-Scattering x-ray source experiment. Experiments on the exposure of living cells to terahertz radiation have been started. These and other developments on ALICE are reported. MACHINE STATUS ALICE, an energy-recovery superconducting linac GaAs photocathode lifetime is now sufficiently long for routine ALICE operation at 40pC. Normally cathode recaesiation is performed once a month, when the quantum efficiency decreases from initial ~3% to below ~0.5%. Over the past year, a number of changes in gradient settings of SC cavities (booster and main linac) were made with the aim of optimising the RF set up and to accommodate limitations presented by the RF system. Each of these variations required significant changes in the overall machine set up. It can now be routinely operated at 27.5MeV with the total beam losses not exceeding 5 to 7%. The energy spectrum of the beam exiting the first cavity of the booster (BC1) with the second cavity (BC2) switched off (resulting in a beam energy of 3.9MeV, compared to the nominal injector energy of 6.5MeV) is shown i
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Proposal of the Next Incarnation of Accelerator Test Facility at KEK for the International Linear Collider
To reach design luminosity, the International Linear Collider (ILC) must be able to create and reliably maintain nanometer size beams. The ATF damping ring is the unique facility where ILC emittances are possible. In this paper we present and evaluate the proposal to create a final focus facility at the ATF which, using compact final focus optics and an ILC-like bunch train, would be capable of achieving 37 nm beam size. Such a facility would enable the development of beam diagnostics and tuning methods, as well as the training of young accelerator physicists
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