580 research outputs found
Reference Measurements of the Longitudinal Impedance in the CERN SPS
First reference measurements of the longitudinal impedance were made with beam in the SPS machine in 1999 to quantify the results of the impedance reduction programme, completed in 2001. The 2001 data showed that the low-frequency inductive impedance had been reduced by a factor 2.5 and that bunch lengthening due to the microwave instability was absent up to the ultimate LHC bunch intensity. Measurements of the quadrupole frequency shift with intensity in the following years suggest a significant increase in impedance (which nevertheless remains below the 1999 level) due to the installation of eight extraction kickers for beam transfer to the LHC. The experimental results are compared with expectations based on the known longitudinal impedance of the SPS
Progress with the Upgrade of the SPS for the HL-LHC Era
The demanding beam performance requirements of the High Luminosity (HL-) LHC
project translate into a set of requirements and upgrade paths for the LHC
injector complex. In this paper the performance requirements for the SPS and
the known limitations are reviewed in the light of the 2012 operational
experience. The various SPS upgrades in progress and still under consideration
are described, in addition to the machine studies and simulations performed in
2012. The expected machine performance reach is estimated on the basis of the
present knowledge, and the remaining decisions that still need to be made
concerning upgrade options are detailed.Comment: 3 p. Presented at 4th International Particle Accelerator Conference
(IPAC 2013
SPS Impedance
For many years several measurements of the beam coupling impedance have been performed each year in both longitudinal and transverse planes of the CERN Super Proton Synchrotron to keep track of the evolution of its hardware. Copious types of equipments had to be modified or added in the past to allow the SPS to produce the nominal LHC beam. The next challenge would be the operation of the SPS with higher intensity for the LHC luminosity upgrade, which requires a good knowledge of the machine impedance and in particular of its major contributors. The current understanding of the measurements performed over the last few years is presented in this paper. In particular, this analysis reveals that the longitudinal impedance is reasonably well understood, while the situation is less satisfactory in the transverse planes, where about half of the measured impedance still needs to be identified
CERN SPS Impedance in 2007
Each year several measurements of the beam coupling impedance are performed in both longitudinal and transverse planes of the CERN Super Proton Synchrotron to keep track of its evolution. In parallel, after the extensive and successful campaign of identification, classification and cure of the possible sources of (mainly longitudinal) impedance between 1998 and 2001, a new campaign (essentially for the transverse impedance this time) has started few years ago, in view of the operation of the SPS with higher intensity for the LHC luminosity upgrade. The present paper summarizes the results obtained from the measurements performed over the last few years and compares them to our predictions. In particular, it reveals that the longitudinal impedance is reasonably well understood and the main contributors have already been identified. However, the situation is quite different in the transverse plane: albeit the relative evolution of the transverse impedance over the last few years can be well explained by the introduction of the nine MKE kickers necessary for beam extraction towards the LHC, significant contributors to the SPS transverse impedance have not been identified yet
Curvature-direction measures of self-similar sets
We obtain fractal Lipschitz-Killing curvature-direction measures for a large
class of self-similar sets F in R^d. Such measures jointly describe the
distribution of normal vectors and localize curvature by analogues of the
higher order mean curvatures of differentiable submanifolds. They decouple as
independent products of the unit Hausdorff measure on F and a self-similar
fibre measure on the sphere, which can be computed by an integral formula. The
corresponding local density approach uses an ergodic dynamical system formed by
extending the code space shift by a subgroup of the orthogonal group. We then
give a remarkably simple proof for the resulting measure version under minimal
assumptions.Comment: 17 pages, 2 figures. Update for author's name chang
A Comparative Research on the Parliamentary Power of Special Criminal Prosecution
议会特别刑事追究权,是指议会通过弹劾、追诉等手段对以政府首脑或其他高级政治和行政官员为主的公职人员因其实施违法行为或失职行为予以追究特别刑事责任,从而保证高级官员依法并合理地行使公权力,从而维护国家政治和法律秩序的良好运转。在近现代宪政国家,宪法通常创设特别刑事追究权并将其授予议会,这构成议会监督和制衡其他国家机构的重要手段。在宪政实践中,议会特别刑事追究权的正常行使为维护宪法体制的正常运转发挥了重要作用。我国宪法虽规定了人大的质询权和罢免权,但对特别刑事追究权却未作规定。事实上,特别刑事追究权不仅有利于加强代表机关的宪法地位,而且对于我国的人大监督制度也有重要参考价值。因此,本文将从比较法的...The system of parliamentary power of special criminal prosecution aims at the constitutional exercise of administrative powers by accusing the state head and leader on their failure to fulfill their duty. In modern constitutional state, the Constitution created Parliamentary Power of Special Criminal Prosecution to supervise other state organs such as administrative and judicial organs. In the con...学位:法学博士院系专业:法学院法律系_宪法学和行政法学学号:1292006015298
Proton acceleration by irradiation of isolated spheres with an intense laser pulse
We report on experiments irradiating isolated plastic spheres with a peak laser intensity of 2-3 x 10(20) W cm(-2). With a laser focal spot size of 10 mu m full width half maximum (FWHM) the sphere diameter was varied between 520 nm and 19.3 mu m. Maximum proton energies of similar to 25 MeV are achieved for targets matching the focal spot size of 10 mu m in diameter or being slightly smaller. For smaller spheres the kinetic energy distributions of protons become nonmonotonic, indicating a change in the accelerating mechanism from ambipolar expansion towards a regime dominated by effects caused by Coulomb repulsion of ions. The energy conversion efficiency from laser energy to proton kinetic energy is optimized when the target diameter matches the laser focal spot size with efficiencies reaching the percent level. The change of proton acceleration efficiency with target size can be attributed to the reduced cross-sectional overlap of subfocus targets with the laser. Reported experimental observations are in line with 3D3V particle in cell simulations. They make use of well-defined targets and point out pathways for future applications and experiments.DFG via the Cluster of Excellence Munich-Centre for Advanced Photonics (MAP) Transregio SFB TR18NNSA DE-NA0002008Super-MUC pr48meIvo CermakCGC Instruments in design and realization of the Paul trap systemIMPRS-APSLMUexcellent Junior Research FundDAAD|ToIFEEuropean Union's Horizon research and innovation programme 633053Physic
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