247 research outputs found
Is LEP beam-beam limited at its highest energy?
The operation of LEP at 45.6 GeV was limited by beam-beam effects and the vertical beam-beam parameter xy never exceeded 0.045. At the highest energy of 94.5 GeV, the increased damping allows higher beam-beam parameters xy . Values above 0.07 in the vertical plane averaged over four experiments have been obtained frequently with peak values up to 0.075 in a single experiment. Although the maximum intensity in LEP is presently limited by technical considerations, some observations indicate that the beam-beam limit is close and the question of the maximum possible values can be raised. These observations are shown in this paper and possible consequences are presented. The optimum operation of LEP in the neighbourhood of the beam-beam limit is discussed
The 4 GeV H- Beam Transfer Line from the SPL to the PS2
The proposed new CERN injector chain LINAC4, SPL, PS2 will require the construction of new beam transfer lines. A preliminary design has been performed for the 4 GeV SPL to PS2 H- transfer line. The constraints, beam parameters and geometry requirements are summarised and a possible layout proposed, together with the magnet specifications. First considerations on longitudinal beam dynamics and on beam loss limitations from H- lifetime are presented
On the integrated behaviour of non-stationary volatility in stock markets
This paper analyses the behaviour of volatility for several international
stock market indexes, namely the SP 500 (USA), the Nikkei (Japan), the PSI 20
(Portugal), the CAC 40 (France), the DAX 30 (Germany), the FTSE 100 (UK), the
IBEX 35 (Spain) and the MIB 30 (Italy), in the context of non-stationarity. Our
empirical results point to the evidence of the existence of integrated
behaviour among several of those stock market indexes of different dimensions.
It seems, therefore, that the behaviour of these markets tends to some
uniformity, which can be interpreted as the existence of a similar behaviour
facing to shocks that may affect the worldwide economy. Whether this is a cause
or a consequence of market globalization is an issue that may be stressed in
future work.Comment: 10 pages, 3 figures. Paper presented in the APFA 5 conferenc
On the integrated behaviour of non-stationary volatility in stock markets
This paper analyses the behaviour of volatility for several international
stock market indexes, namely the SP 500 (USA), the Nikkei (Japan), the PSI 20
(Portugal), the CAC 40 (France), the DAX 30 (Germany), the FTSE 100 (UK), the
IBEX 35 (Spain) and the MIB 30 (Italy), in the context of non-stationarity. Our
empirical results point to the evidence of the existence of integrated
behaviour among several of those stock market indexes of different dimensions.
It seems, therefore, that the behaviour of these markets tends to some
uniformity, which can be interpreted as the existence of a similar behaviour
facing to shocks that may affect the worldwide economy. Whether this is a cause
or a consequence of market globalization is an issue that may be stressed in
future work.Comment: 10 pages, 3 figures. Paper presented in the APFA 5 conferenc
Experience with a Low Emittance Optics in LEP
Since start-up in 1998, LEP has operated with a low emittance lattice with a phase advance of 102 deg in the horizontal and 90 deg in the vertical planes. This optics provides a horizontal detuning with amplitude which is small enough to avoid a reduced dynamic aperture in the horizontal plane, a problem experienced in other low emittance lattices. The optics is designed to operate at the highest LEP energies up to and above 100 GeV, as well as at 45.6 GeV (still required to provide Z0s for the calibration of the experiments detectors). The experience gained with this low emittance lattice after one year of operation is presented and its future potential is discussed
A Candidate Low Emittance Lattice for LEP at its Highest Energies
Several low emittance lattices have been proposed for LEP at its highest energies in order to reduce the horizontal beam size and bring the beam-beam limit within reach. However, optics with high phase advance per cell tend to have strong tune dependence on amplitude that can reduce the dynamic aperture and the beam lifetime, possibly limiting the maximum beam energy or creating operational difficulties. Recently an optics with a phase advance of 17p/30 in the horizontal and p/2 in the vertical plane was developed. This optics has a significantly smaller detuning with amplitude. The results of experiments on this optics are compared with expectations and some details of the first operational experience with this lattice are presented. The potential performance at maximum energy is discussed
Design and Performance of the CNGS Secondary Beam Line
An intense muon-neutrino beam (1017nm /day) is generated at CERN and directed towards the Gran Sasso National Laboratory, LNGS, in Italy, 732 km away from CERN. In the presently approved physics programme, it is foreseen to run the CNGS facility with 4.5.1019 protons per year for five years. During a nominal CNGS cycle, i.e. every 6s, two nominal SPS extractions of 2.4.1013 protons each at 400GeV/c are sent down the proton beam line to the target. The CNGS secondary beam line, starting with the target, has to cope with this situation, which pushes the beam line equipment and instrumentation to the limits of radiation hardness and mechanical stresses during the CNGS operation. An overview of the CNGS secondary beam line is given. Emphasis is on the target, the magnetic focusing lenses (horn and reflector) and the muon monitors. The performance of the secondary beam line during beam commissioning and physics operation is discussed and measurements are compared with simulations
Resonant Third-Integer Extraction from the PS2
For the proposed PS2 accelerator several extraction systems are needed, including a slow third-integer resonant extraction. The requirements are presented together with the conceptual considerations for the sextupole locations and strengths, the separatrices at the extraction elements and the aperture implications for the overall machine. Calculations of the phase space separatrices have been computed with a new code for the physics of slow resonant extraction, which is briefly reviewed. Implications for the extraction equipment design and for the injection-extraction straight section optics are discussed
LHC Abort Gap Cleaning with the Transverse Damper
In the Large Hadron Collider, LHC, particles not captured by the RF system at injection or leaking out of the RF bucket may quench the superconducting magnets during beam abort. The problem, common to other superconducting machines, is particularly serious for the LHC due to the very large stored energy in the beam. For the LHC a way of removing the unbunched beam has been studied and it uses the existing damper kickers to excite resonantly the particles travelling along the abort gap. In this paper we describe the results of simulations performed with MAD X for various LHC optics configurations, including the estimated multipolar errors
Low emittance lattice for LEP
In order to obtain the largest luminosity with LEP2, it is attractive to make the beam emittance as small as possible because the beam-beam effect is not a limitation at the energy of E~90 GeV for the obtained bunch currents. This can be achieved with a high tune lattice. Two possible candidates are lattices with a horizontal phase advance of 108o or 135o per cell. Both have a vertical phase advance of 60o. These lattice were developed during 1994 and the results are presented. tests to reach high intensity for the 108o lattice were performed and the bunch current achieved is compared with expectations. For this lattice the detuning v.s. intensity and several optics parameters were measured as well
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