142 research outputs found
Chromaticity Dependence of the Transverse Effective Impedance in the CERN Proton Synchrotron
No full textThe current knowledge of the transverse impedance of the Proton Synchrotron (PS) has been established with beam-based measurements at different energies. The transverse coherent tune shift as a function of the beam intensity has been measured in order to evaluate the total effective imaginary part of the transverse impedance and its localization in the accelerator at the energies of 2, 7, 13 and 25 GeV. Measurements have been performed changing the chromaticity for every tune shift scan with intensity. The data analysis revealed an increase of impedance with chromaticity for all the energies considered. That transverse impedance can be compared with the previously evaluated theoretical impedance budget taking into account the individual contribution of several machine devices. The missing impedance is finally highlighted
Simulation and optimization of beam losses during continuous transfer extraction at the CERN Proton Synchrotron
No full textThe proton beams used for the fixed target physics at the Super Proton Synchrotron (SPS) are extracted from the Proton Synchrotron ( PS) by a multiturn technique called continuous transfer (CT). During the CT extraction, large losses are observed in locations where the machine aperture should be large enough to accommodate the circulating beam. This limits the maximum intensity deliverable due to the induced stray radiation outside the PS tunnel. Scattered particles from the interaction with the electrostatic septum are identified as the possible source of these losses. This article presents a detailed study aiming to understand the origin of losses and propose possible cures. The simulations could reproduce accurately the beam loss pattern measured in real machine operation and determine the beam shaving, intrinsic to the extraction process, as the cause for the unexpected losses. Since these losses are unavoidable, the proposed solution implies a new optics scheme displacing the losses to a region with better shielding. New simulations demonstrate the satisfactory performance of the new extraction optics and its suitability to be implemented in the machine. Finally, beam loss measurements in these new operation conditions confirmed the previous simulation results
Los límites de la ausencia. Un ensayo sobre historia de las ideas: José Aricó, Leopoldo Zea y Carlos Real de Azúa
No full textI propose reading José Aricó’s “Marx y América Latina” as a work in which the author discusses Leopoldo Zea´s proposals to study the history of ideas in such a way that it also relates to Carlos Real de Azúa´s approaches: the obsessions and terms of a possible “esoteric history” or a “philosophical research”
Comparison of the performance of different instruments in the stray neutron field around the CERN Proton Synchrotron
No full textThis paper discusses an intercomparison campaign carried out in several locations around the CERN Proton Synchrotron. The locations were selected in order to perform the measurements in different stray field conditions. Various neutron detectors were employed: ionisation chambers, conventional and extended range rem counters, both commercial and prototype ones, including a novel instrument called LUPIN, specifically conceived to work in pulsed fields. The attention was focused on the potential differences in the instrument readings due to dead-time losses that are expected to affect most commercial units. The results show that the ionisation chambers and LUPIN agree well with the expected H*(10) values, as derived from FLUKA simulations, showing no relevant underestimations even in strongly pulsed fields. On the contrary, the dead-time losses of the other rem counters induced an underestimation in pulsed fields that was more important for instruments characterised by a higher dead time
First observations of intensity-dependent effects for transversely split beams during multi-turn extraction studies at the CERN proton synchrotron
No full textDuring the commissioning of the CERN PS Multi-Turn Extraction (MTE), tests with different beam intensities were performed in order to probe the behaviour of resonance crossing in the presence of possible space charge effects. The initial beam intensity before transverse splitting was varied and the properties of the five beamlets obtained by crossing the fourth-order horizontal resonance were studied. A clear dependence of the beamlets’ parameters on the total beam intensity was found, which is the first direct observation of intensity-dependent effects for such a peculiar beam type. The experimental results are presented and discussed in detail in this paper
Septum shadowing by means of a bent crystal to reduce slow extraction beam loss
No full textThe flux of high-energy protons slow-extracted from the CERN Super Proton Synchrotron (SPS) is limited by the induced radioactivity caused by the beam loss intrinsic to the extraction process. Methods to substantially increase the efficiency of the extraction process are of great interest to fulfill requests for an increasing flux of 400 GeV protons to the present experiments, located in the North Area of the SPS, and also for potential future experiments with very high demanded protons on target. A crystal shadowing technique to significantly reduce the beam scattered and lost on the electrostatic extraction septum during the third-integer resonant slow extraction process has been developed and a prototype system tested with beam. The technique is based on the use of a thin, bent silicon crystal to coherently channel or volume reflect the portion of beam that would otherwise impinge the wire array of the electrostatic septum and instead eject it into the transfer line toward the production targets of the experiments. In this paper, the concept is described and applied to the SPS machine in order to specify the requirements of the prototype crystal shadowing system. Beam dynamics simulations of the prototype system are compared and benchmarked to the results obtained through beam tests, before being exploited to understand the characteristics of the present system and the potential performance reach of an optimized, future operational configuration. The remaining challenges faced to bring the system into operation, the optimization possibilities and other potential applications are discussed
Preliminary magnetic horn studies in the collection scheme for a neutrino factory
No full textNeutrino factories rely on efficient targeting for a primary proton beam in the 2-16 GeV range and a collection scheme with very large acceptance for the pions produced from the target. A shaped solenoid with a peak field of 20 T tapered to 1.25 T has been suggested. In this note, some initial studies are presented on the use of a magnetic horn at the beginning of the collection scheme: this produces a toroidal magnetic field between the co-axial conductors which can be shaped by designing the form of the inner conductor. Magnetic horns are known to withstand high radiation doses. Preliminary results show that the flux of the pions after a horn could be comparable to that obtained with the suggested solenoid. (6 refs)
Data for the s Process from n_TOF
No full textA considerable amount of (n) reactions has been studied, so far, at the neutron time-of-flight facility n_TOF at CERN. The experimental program aims at determining and improving cross sections for a number of isotopes relevant to s-process nucleosynthesis. A brief summary of some physical cases related to the s-process nucleosyntheis is presented in this work together with ongoing experiments and challenging future programs
Recent developments with the new tools for collimation simulations in Xsuite
No full textSimulations of single-particle tracking involving collimation systems need dedicated tools to perform the different tasks needed. These include the accurate description of particle-matter interactions when a tracked particle impacts a collimator jaw; a detailed aperture model to identify the longitudinal location of losses; and others. One such tool is the K2 code in SixTrack, which describes the scattering of high-energy protons in matter. This code has recently been ported into the Xsuite tracking code that is being developed at CERN. Another approach is to couple the tracking with existing tools, such as FLUKA or Geant4, that offer better descriptions of particle-matter interactions and can treat lepton and ion beams. This includes the generation of secondary particles and fragmentation when tracking ions. In addition to the development of coupling with Geant4, the SixTrack-FLUKA coupling has recently been translated and integrated into the Xsuite environment as well. In this paper, we present the ongoing development of these tools. A thorough testing of the new implementation was performed, using as case studies various collimation layout configurations for the LHC Run 3
Corrigendum to: Observation of focusing of 400 GeV/c proton beam with the help of bent crystals [Phys. Lett. B 733 (2014) 366–372]
No full textThe author list is incomplete because Enrico Bagli (INFN Sezione di Ferrara, Dipartimento di Fisica, Università di Ferrara, Ferrara, Italy) was erroneously missed
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