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

The use of remote sensing to quantify wetland loss in the Choke Mountain range, Upper Blue Nile basin, Ethiopia

Wetlands provide multiple ecosystem services such as storing and regulating water flows and water quality, providing unique habitats to flora and fauna, and regulating micro-climatic conditions. Conversion of wetlands for agricultural use is a widespread practice in Ethiopia, particularly in the southwestern part where wetlands cover large areas. Although there are many studies on land cover and land use changes in this region, comprehensive studies on wetlands are still missing. Hence, extent and rate of wetland loss at regional scales is unknown. The objective of this paper is to quantify wetland dynamics and estimate wetland loss in the Choke Mountain range (area covering 17 443 km<sup>2</sup>) in the Upper Blue Nile basin, a key headwater region of the river Nile. Therefore, satellite remote sensing imagery of the period 1986–2005 were considered. To create images of surface reflectance that are radiometrically consistent, a combination of cross-calibration and atmospheric correction (Vogelman-DOS3) methods was used. A hybrid supervised/unsupervised classification approach was used to classify the images. Overall accuracies of 94.1% and 93.5% and Kappa Coefficients of 0.908 and 0.913 for the 1986 and 2005 imageries, respectively were obtained. The results showed that 607 km<sup>2</sup> of seasonal wetland with low moisture and 22.4 km<sup>2</sup> of open water are lost in the study area during the period 1986 to 2005. The current situation in the wetlands of Choke Mountain is characterized by further degradation which calls for wetland conservation and rehabilitation efforts through incorporating wetlands into watershed management plans

Trajectory Correction in the Transfer Line TT2-TT10 for the Continuous Transfer (CT)

A new scheme for the trajectory correction in the TT2-TT10 transfer line for the Continuous Transfer (CT) extraction from the PS to the SPS has been developed together with a new software application, PS-CT-Check. In this note the algorithm, the software, and the results of the tests performed during the 2007 run are summarized. The PS-CT-Check user's manual is also provided. The scheme, with minor modifications, will be applied to the new Multi-Turn Extraction (MTE)

Protection of the LHC against Unsynchronised Beam Aborts

An unsynchronised beam abort in the LHC could damage downstream accelerator components, in particular the extraction septum magnets, the experimental low-beta triplet magnet apertures and the tertiary collimators. Although the LHC beam dumping system includes design features to minimise their frequency, such unsynchronised aborts cannot be excluded. A system of protection devices comprising fixed and moveable diluters and collimators will protect the downstream LHC aperture from the misdirected bunches in case of such a failure. The sources of unsynchronised aborts are described, together with the requirements and design of the protection devices and their expected performance. The accompanying operational requirements and envisaged solutions are discussed, in particular the problem of ensuring the local orbit at the protection devices

Commissioning of the CNGS Extraction in SPS LSS4

The CNGS project (CERN Neutrino to Gran Sasso) aims at directly detecting νμ - Î½Ï oscillations. For this purpose an intense νμ beam is generated at CERN and directed towards LNGS (Laboratori Nazionali del Gran Sasso) in Italy, about 730 km from CERN. The neutrinos are generated from the decay of pions and kaons which are produced by 400 GeV protons hitting a graphite target. The protons are extracted from the SPS straight section 4 (LSS4) in two 10.5 ï­s batches, nominally 2.4 Ñ 1013 protons each, at an interval of 50 ms. The high intensity extracted beam can cause damage to equipment if lost in an uncontrolled way, with the extraction elements particularly at risk. In addition, the beam losses at extraction must be very well controlled to avoid unacceptably high levels of radiation. To guarantee safe operation and limit radiation, the LSS4 extraction system was thoroughly commissioned with beam during the CNGS commissioning in summer 2006. The obtained results in terms of aperture in the extraction channel, longitudinal loss patterns, extraction losses and radiation during nominal operation are summarised in this note

Calibration of centre-of-mass energies at LEP 2 for a precise measurement of the W boson mass

The determination of the centre-of-mass energies for all LEP 2 running is presented. Accurate knowledge of these energies is of primary importance to set the absolute energy scale for the measurement of the W boson mass. The beam energy between 80 and 104 GeV is derived from continuous measurements of the magnetic bending field by 16 NMR probes situated in a number of the LEP dipoles. The relationship between the fields measured by the probes and the beam energy is defined in the NMR model, which is calibrated against precise measurements of the average beam energy between 41 and 61 GeV made using the resonant depolarisation technique. The validity of the NMR model is verified by three independent methods: the flux-loop, which is sensitive to the bending field of all the dipoles of LEP; the spectrometer, which determines the energy through measurements of the deflection of the beam in a magnet of known integrated field; and an analysis of the variation of the synchrotron tune with the total RF voltage. To obtain the centre-of-mass energies, corrections are then applied to account for sources of bending field external to the dipoles, and variations in the local beam energy at each interaction point. The relative error on the centre-of-mass energy determination for the majority of LEP 2 running is 1.2 x 10^{-4}, which is sufficiently precise so as not to introduce a dominant uncertainty on the W mass measurement.Comment: 79 pages, 45 figures, submitted to EPJ

High Intensity Commissioning of the SPS LSS4 extraction for CNGS

The SPS LSS4 fast extraction system will serve both the anti-clockwise ring of the LHC and the CERN Gran Sasso Neutrino project (CNGS). CNGS requires 2 fast extractions of 10.5 microsecond long batches, 50 milliseconds apart. Each batch will consist of 2.4 × 1013 protons at 400 GeV. These intensities are factor of 10 above the equipment damage limit in case of beam loss. Active (interlock system) and passive protection systems have to be in place to guarantee safe operation and to respect the radiation limits in zones close to the extraction region. In summer 2006 CNGS was commissioned including extraction with high intensity. A thorough setting-up of the CNGS extraction was carried out as part of the CNGS commissioning, including aperture and beam loss measurements, and defining and checking of interlock thresholds for extraction trajectory, beam loss monitors and radiation monitors. The relevant systems and risks are introduced in this paper, the commissioning results are summarised and comparisons with simulation predictions are presented

Evaluation of the LEP Centre-of-Mass Energy Above the W-Pair Production Threshold

Knowledge of the centre-of-mass energy at LEP2 is of primary importance to set the absolute energy scale for the measurement of the W-boson mass. The beam energy above 80 GeV is derived from continuous measurements of the magnetic bending field by 16 NMR probes situated in a number of the LEP dipoles. The relationship between the fields measured by the probes and the beam energy is calibrated against precise measurements of the average beam energy between 41 and 55 GeV made using the resonant depolarisation technique. The linearity of the relationship is tested by comparing the fields measured by the probes with the total bending field measured by a flux loop. This test results in the largest contribution to the systematic uncertainty. Several further corrections are applied to derive the the centre-of-mass energies at each interaction point. In addition the centre-of-mass energy spread is evaluated. The beam energy has been determined with a precision of 25 MeV for the data taken in 1997, corresponding to a relative precision of 2.7x10^{-4}. This is small in comparison to the present uncertainty on the W mass measurement at LEP. However, the ultimate statistical precision on the W mass with the full LEP2 data sample should be around 25 MeV, and a smaller uncertainty on the beam energy is desirable. Prospects for improvements are outlined.Comment: 24 pages, 10 figures, Latex, epsfig; replaced by version accepted by European Physical Journal

Luminosity and Beam Measurements used for Performance Optimisation in the LEP Collider

The vertical beam-beam parameter in LEP reached 0.083 in 1999. In order to achieve and maintain this high performance a number of different observables are continuously monitored and optimised. The beam sizes are measured using X-ray detectors and UV telescopes. The luminosity is determined directly with tungsten-silicon calorimeters and indirectly through an accurate measurement of the beam lifetime. The tune shift is measured from the tune spectrum in collision. Beam-beam deflection scans provide information about the beam sizes and separation at the interaction points. The different measurements are shortly reviewed and their resolution and time response is analysed. Their use for the optimisation of LEP is described