Multiturn Measurements at the CERN SPS

The CERN SPS multiturn facility, based on the new beam orbit measurement system MOPOS, enables the User to acquire the position of the beam at each beam position monitor (BPM) over a number of consecutive turns. When the multiturn acquisition is synchronised with a perturbation imposed on the beam (for instance a fast kick), useful information about the optics of the SPS and the dynamic behaviour of the beam can be extracted from the data. A measurement of the amplitude and phase of the betatron oscillation at each BPM can be used to compare the theoretical optics functions with the real ones, and possibly to detect localised errors. Differences between two such measurements can be used to study the dependence on a variable parameter (e.g. beam intensity, beam energy, etc) and therefore indirectly measure quantities, like the impedance, distributed along the ring. Finally, due to 90 degrees phase advance lattice, plotting the positions measured at two consecutive BPMs against each other gives information about the behaviour of the beam in the transverse phase space. Results of measurements performed at the CERN SPS are presente

Alternative bunch filling schemes for the LHC

The standard batches transfered from the PS to the SPS consist of 72 bunches each (in 3.6 s PS cycle). Alternative schemes with 48 bunches per batch (in 2.4 s PS cycle) have been investigated as backup solutions or in case of problems. The implications for the performance and the injector chain have been studied and are presented. Only filling schemes for proton operation are considered. Other filling schemes such as the bunch disposition for ion operation are not changed

Baseline LHC machine parameters and configuration of the 2015 proton run

This paper shows the baseline LHC machine parameters for the 2015 start-up. Many systems have been upgraded during LS1 and in 2015 the LHC will operate at a higher energy than before and with a tighter filling scheme. Therefore, the 2015 commissioning phase risks to be less smooth than in 2012. The proposed starting configuration puts the focus on feasibility rather than peak performance and includes margins for operational uncertainties. Instead, once beam experience and a better machine knowledge has been obtained, a push in $\beta^*$ and performance can be envisaged. In this paper, the focus is on collimation settings and reach in $\beta^*$---other parameters are covered in greater depth by other papers in these proceedings.Comment: submitted for publication in a CERN yellow report (Proceedings of the LHC Performance Workshop - Chamonix 2014

FIRE Cirrus on October 28, 1986: LANDSAT; ER-2; King Air; theory

A simultaneous examination was conducted of cirrus clouds in the FIRE Cirrus IFO-I on 10/28/86 using a multitude of remote sensing and in-situ measurements. The focus is cirrus cloud radiative properties and their relationship to cloud microphysics. A key element is the comparison of radiative transfer model calculations and varying measured cirrus radiative properties (emissivity, reflectance vs. wavelength, reflectance vs. viewing angle). As the number of simultaneously measured cloud radiative properties and physical properties increases, more sharply focused tests of theoretical models are possible

Analysis and Measurement of coupling effects in the transfer line from PS to SPS for the LHC proton beam

The tight emittance budget for injection into the LHC demands an accurate matching of the transfer line from the PS to the SPS to minimise blow-up at injection into the SPS. Precise two-dimensional beam profile measurements with Optical Transition Radiation (OTR) screens have recently pointed towards the presence of coupling in the LHC beam transfer. The new algorithms developed to analyse the profile data from the OTR screens and to quantify the observed coupling (in particular the determination of the complete 5?5 beam covariance matrix) are discussed. The results of the measurements and their dependence on the extraction conditions in the PS (trajectory and momentum) are presented and discussed in detail

Measurements of the SPS transverse impedance in 2000

We report on measurements of coherent tune shifts, head-tail growth rates, and current-dependent betatron phase advances at the CERN SPS in the year 2000. Comparing results obtained at two different energies shows that there is no notable contribution from space charge. Within the measurement resolution the impedance is the same as in 1999, consistent with the expected small effect from changes to ony a small number of pumping ports. In 2000, data were taken over an expanded range of chromaticities, which increases the sensitivity to the impedance frequency distribution. Measuremeents of the current-dependent phase advance around the ring help localizing the most important impedance sources

The 27-28 October 1986 FIRE IFO Cirrus case study: Comparison of radiative transfer theory with observations by satellite and aircraft

Observations of cirrus and altocumulus clouds during the First International Satellite Cloud Climatology Project Regional Experiment (FIRE) are compared to theoretical models of cloud radiative properties. Three tests are performed. First, LANDSAT radiances are used to compare the relationship between nadir reflectance ot 0.83 micron and beam emittance at 11.5 microns with that predicted for model calculations using spherical and nonspherical phase functions. Good agreement is found between observations and theory when water droplets dominate. Poor agreement is found when ice particles dominate, especially using scattering phase functions for spherical particles. Even when compared to a laboratory measured ice particle phase function, the observations show increased side scattered radiation relative to the theoretical calculations. Second, the anisotropy of conservatively scattered radiation is examined using simultaneous multiple angle views of the cirrus from LANDSAT and ER-2 aircraft radiometers. Observed anisotropy gives good agreement with theoretical calculations using the laboratory measured ice particle phase function and poor agreement with a spherical particle phase function. Third, Landsat radiances at 0.83, 1.65, and 2.21 microns are used to infer particle phase and particle size. For water droplets, good agreement is found with King Air FSSP particle probe measurements in the cloud. For ice particles, the LANDSAT radiance observations predict an effective radius of 60 microns versus aircraft observations of about 200 microns. It is suggested that this descrepancy may be explained by uncertainty in the imaginary index of ice and by inadequate measurements of small ice particles by microphysical probes

On the energy dependence of proton beam extraction with a bent crystal

Proton beam extraction from the CERN SPS by means of a bent silicon crystal is reported at three different energies, 14 GeV, 120 GeV and 270 GeV. The experimental results are compared to computer simulations which contain a sound model of the SPS accelerator as well as the channeling phenomena in bent crystals. The overall energy dependence of crystal assisted proton beam extraction is understood and provides the basis to discuss such a scheme for future accelerators

Extraction of 22 TeV/c lead ions from the CERN SPS using a bent silicon crystal

The extraction of protons from the halo of a circulating beam has been repeatedly demonstrated at the SPS. In a recent experiment a coasting lead ion beam was available at a momentum of 270 GeV/c per charge corresponding to a total momentum of 22 TeV/c per ion and the possibility to extract ultrarelativistic lead ions with a bent crystal could be demonstrated for the first time. We present the experimental challenges, the measurements performed during this experiment and the first results