Synchrotron tune and beam energy at LEP2

The synchrotron tunes depend on energy loss and total accelerating voltage. This dependency can be used to extract the beam energy in a very precise way. Since the energy calibration of LEP 2 requires the highest possible accuracies detailed systematic studies of the parameters involved in the analysis are necessary. This paper presents method, systematic studies and results of the energy determination from the synchrotron

Measurements of Coherent Damping and Tune Shifts with Amplitude at LEP

The coherent damping offers the possibility to study various machine parameters such as head-tail damping, radiation damping and the horizontal detuning with amplitude. At the LEP electron-positron co llider the beam orbit system is able to store the beam positions over 1000 turns following a deflection by a horizontal kicker. A precise analysis of such data for many beam position monitors was used to study the dependance of head-tail damping on beam parameters. The tune dependance on the horizontal amplitude was determined during the decay of the beam oscillation for various LEP optics. This pa rameter turned out to be an important issue for the LEP high energy optic

Measurements of Tune Shifts with Amplitude at LEP

The beam orbit system of the LEP electron-positron collider is able to store the beam position over 1000 turns following a deflection by a horizontal kicker. A precise analysis of such 1000-turn data for many beam position monitors was used to study the dependence of the tune on the horizontal amplitude. The horizontal tune shift with amplitude was determined from the decay of the beam oscillation for various LEP optics. This parameter turned out to be an important issue for the LEP high energy optics

Energy Loss Measurements at LEP 2

The accurate measurement of the W Boson mass at LEP requires to determine the beam energy to the highest possible precision. Present schemes rely on accurate energy determination in the range of 40 to 60 GeV using resonant depolarization and on precise extrapolations to high energy. Several methods based on measurements of the energy loss due to synchroton radiation have been studied. Different approaches such as the study of the damping time of transverse oscillations, the radio frequency sawtooth and the dependence of the synchroton tune on the total accelerating voltage are described and results are discussed

Head Tail Damping and Impedance at LEP

Head tail damping rate and coherent tune shift depend on chromatically and transverse wake field. Using this dependence, the transverse impedance of LEP can be estimated from coherently damped betatron oscillations measured at different chromaticities and beam currents. We compare measurements and analytical results

Closed orbit feed-back from low-β\beta quadrupole movements at LEP

Left and right of each of the four LEP interaction points superconducting low-beta quadrupole magnets are installed to squeeze the vertical beam size at the interaction points. These magnets are the dominant source of vertical closed orbit drifts at LEP because of their strength, the large vertical beta function and their support. Hydrostatic Levelling Systems and resistor-based position sensors were installed to measure the vertical movements of these magnets continuously. The correlation between the mechanical movements and closed orbit variations has been studied. The analysis has shown that the orbit can be kept stable by acting on one correction dipole per low-beta quadrupole pair. This has led to a feed-back system which uses the mechanical measurements to correct the closed orbit and to prevent large orbit variations

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)

Beta-Beating Corrections in the SPS as a Testbed for the LHC

For several years optics measurement and correction algorithms have been developed for the LHC. During 2008 these algorithms have been tested in the SPS and RHIC. The experimental results proving the readiness of the applications are presented

Proposal to Increase the LEP Energy with Horizontal Orbit Correctors

In an e+ e- collider the beam energy depends only on the bending field integral "Bds while the synchrotron radiation power scales with "B2ds and is sensitive to the details of the field distribution. With fixed RF acceleration voltage it is thus possible to attain higher energies by increasing the effective bending magnet length. We propose to use the horizontal orbit correctors to exploit this effect. To control the orbit perturbations, 79 unused correctors in the regular arcs and 14 unused correctors in the dispersion suppressors will have to be powered. An energy increase of approximatively 0.18 GeV per beam might be obtained

Ecohydrological characterization of the Nyando wetland, Lake Victoria, Kenya: A State of System (SoS) analysis

Lake Victoria floodplain wetlands have a complex hydrological setting characterized by transition from a terrestrial to an aquatic environment. A state-of-system (SoS) analysis was carried out in a papyrus dominated wetland in the Nyando River Delta, on the eastern shores of Lake Victoria, Kenya, to characterize and provide data for detailed ecohydrological studies. The objectives of the study were to: (1) determine the spatio- temporal changes in the wetland evolution and (2) analyze the main hydrological factors that have influenced wetland evolution. Multi-temporal dry-season Landsat MSS, Landsat TM and Landsat ETM+ imagery covering Nyando Wetland and its surrounding area were processed and analyzed to generate time series polygon and polyline maps of the wetland and river. Results show that the wetland increased in size from 5,925 ha in 1950 to 9,925 ha in 1973, and declined to 4,527 ha in 2008. In the last 60 years, Nyando River has migrated in a general eastward direction. Time series hydrological data (1950-2009) were statistically tested for homogeneity  using the Spearman’s rank test for linear trends, Pettit test and Standard Normal Homogeneity test (SNHT) for change point analysis, and split-record tests performed for variance (F-test) and mean (t-test). In addition, data were analyzed using descriptive statistics and frequency analyses. Statistical test results show that the hydrological data series were homogeneous. Results of change point analyses indicate that total annual rainfall in Nyando declined in 1979, while the mean annual discharge for Nyando River and Lake Victoria levels had significant upward shifts in 1961. The decadal mean discharges varied significantly over time and increased by 80% from 11.45 m3/s observed in the 1950-1961 subset, reducing by 11.4 and 21.9% in the next two decadal sub-sets, before rising by 35.0% in 1990s and dropping by 24.0% in the last decade. The decadal mean annual lake levels increased from 1134.0 to 1135.43 m in the 1951-1961 and 1962-1972 and remained above the longterm mean of 1135.0 m for 43 years since 1962 before dropping drastically by 1.4 m to an average of 1134 m/year in 2005-2009. The highest recorded lake level at Kisumu Station was 1136.2 m in 1964 after increasing by 2.5 m from 1961. Discharge data exhibit trimodal seasonal patterns, while the lake levels had two peaks. The lake levels are more sensitive to direct lake rainfall. Changes in the Nyando wetland area are linked to the seasonal and episodic flood and drought events coupled with anthropogenic activities (regulation of lake levels, modification of river including cut-off meanders, river training and construction of dykes, drainage of wetland for cultivation, settlement and livestock grazing, abstraction of water for irrigation). A combination of these hydrological and human factors is the main cause of the Nyando Wetland evolution. If the land use trend continues unabated, then the increase in papyrus losses will pose a big challenge to the ecological functioning of the wetland and its support to sustaining community livelihoods.Key words: Nyando Wetland, River, ecohydrology, Lake Victoria