Study of losses during Continuous Transfer Extraction at CERN Proton Synchrotron

The proton beams used for the fixed target physics at the SPS are extracted from the PS at 14 GeV/c in five turns, using a technique called Continuous Transfer (CT). During this extraction, large losses are observed in straight sections were the machine aperture should be large enough to accommodate the circulating beam without any loss. These losses are due to particles scattered by the electrostatic septum used to slice the beam and defocused by a quadrupole used during the extraction. Simulations and experimental results are presented

Beam losses in the PS during CT extraction

The proton beams used for the fixed target physics at the SPS are extracted from the PS at 14 GeV/c in five turns, using a technique called Continuous Transfer (CT). During this extraction, large losses are observed in straight sections were the machine aperture should be large enough to accommodate the circulating beam without any loss. These losses are due to particles scattered by the electrostatic septum used to slice the beam and defocused by a quadrupole used during the extraction. Simulations and experimental results are presented

Study of Beam Losses at Transition Crossing at the CERN PS

A series of studies has been carried out to understand and alleviate the beam losses in the CERN PS Proton Synchrotron. Losses appear especially at transition crossing during the pulsing of special quadrupoles used to create a gamma jump scheme. However, this causes a large optics and orbit distortion. After a brief summary of the gamma jump scheme at the PS, experimental and simulation results of the loss and reduction studies are presented

GEANT4 simulation of phase rotation for neutrino factory

We discuss a GEANT4 simulation of the phase rotation system for a neutrino factory. The comparison with the beam transport code PATH shows a good agreement. Preliminary results for the energy disposition in the cryostat of the superconducting 1.8 T solenoid are briefly presented

Experimental Evidence of Beam Trapping with one-third and one-fifth Resonance Crossing

Beam trapping in stable islands of the horizontal phase space generated by non-linear magnetic fields is realized by means of a given tune variation so to cross a resonance of order n. Whenever the resonance is stable, n + 1 beamlets are created whereas if the resonance is unstable, the beam is split in n parts. Experiments at the CERN Proton Synchrotron showed protons trapped in stable islands while crossing the one-third and one-fifth resonance with the creation of 3 and 6 stable beamlets, respectively. The results are presented and discussed

Using measurements for evaluation of black carbon modeling

The ever increasing use of air quality and climate model assessments to underpin economic, public health, and environmental policy decisions makes effective model evaluation critical. This paper discusses the properties of black carbon and light attenuation and absorption observations that are the key to a reliable evaluation of black carbon model and compares parametric and nonparametric statistical tools for the quantification of the agreement between models and observations. Black carbon concentrations are simulated with TM5/M7 global model from July 2002 to June 2003 at four remote sites (Alert, Jungfraujoch, Mace Head, and Trinidad Head) and two regional background sites (Bondville and Ispra). Equivalent black carbon (EBC) concentrations are calculated using light attenuation measurements from January 2000 to December 2005. Seasonal trends in the measurements are determined by fitting sinusoidal functions and the representativeness of the period simulated by the model is verified based on the scatter of the experimental values relative to the fit curves. When the resolution of the model grid is larger than 1° × 1°, it is recommended to verify that the measurement site is representative of the grid cell. For this purpose, equivalent black carbon measurements at Alert, Bondville and Trinidad Head are compared to light absorption and elemental carbon measurements performed at different sites inside the same model grid cells. Comparison of these equivalent black carbon and elemental carbon measurements indicates that uncertainties in black carbon optical properties can compromise the comparison between model and observations. During model evaluation it is important to examine the extent to which a model is able to simulate the variability in the observations over different integration periods as this will help to identify the most appropriate timescales. The agreement between model and observation is accurately described by the overlap of probability distribution (PD) curves. Simple monthly median comparisons, the Student's t-test, and the Mann-Whitney test are discussed as alternative statistical tools to evaluate the model performance. The agreement measured by the Student's t-test, when applied to the logarithm of EBC concentrations, overestimates the higher PD agreements and underestimates the lower PD agreements; the Mann-Whitney test can be employed to evaluate model performance on a relative scale when the shape of model and experimental distributions are similar

Adiabaticity and Reversibility Studies for Beam Splitting using Stable Resonances

At the CERN Proton Synchrotron, a series of beam experiments proved beam splitting by crossing the one-fourth resonance. Depending on the speed at which the horizontal resonance is crossed, the splitting process is more or less adiabatic, and a different fraction of the initial beam is trapped in the islands. Experiments prove that when the trapping process is reversed and the islands merged together, the final distribution features thick tails. The beam population in such tails is correlated to the speed of the resonance crossing and to the fraction of the beam trapped in the stable islands. Experiments and possible theoretical explanations are discussed