Synchronous Phase Shift at LHC

The electron cloud in vacuum pipes of accelerators of positively charged particle beams causes a beam energy loss which could be estimated from the synchronous phase. Measurements done with beams of 75 ns, 50 ns, and 25 ns bunch spacing in the LHC for some fills in 2010 and 2011 show that the average energy loss depends on the total beam intensity in the ring. Later measurements during the scrubbing run with 50 ns beams show the reduction of the electron cloud due to scrubbing. Finally, measurements of the individual bunch phase give us information about the electron cloud build-up inside the batch and from batch to batch.Comment: Presented at ECLOUD'12: Joint INFN-CERN-EuCARD-AccNet Workshop on Electron-Cloud Effects, La Biodola, Isola d'Elba, Italy, 5-9 June 201

Longitudinal beam parameters and quality checks of the LHC beam in the SPS: further results and comparisons

Controlled longitudinal emittance blow up is used, along with other measures, to stabilize the nominal LHC beam in the SPS. Two Machine Development studies (MDs) were carried out in 2007 to evaluate the effectiveness of different noise settings for the longitudinal blow up of the beam. The noise settings are affected by both the presence of the 800 MHz RF system and intensity effects which modify the synchrotron frequency distribution inside the bunch. The results for the first MD are reported in Note [1]. This Note reports on the results of the second MD, carried out on 2007-10-17, as well as the comparison between the two in order to analyse the differences between the two occasions. Figures of merit are used that allow rapid evaluation of the quality of the beam as for example stability and bunch length uniformity across batches

Study of Controlled Longitudinal Emittance Blow-Up for High Intensity LHC Beams in the CERN SPS

Preventive longitudinal emittance blow-up, in addition to a fourth harmonic Landau damping RF system, is required to keep the LHC beam in the SPS stable up to extraction. The beam is blown-up in a controlled way during the acceleration ramp by using band-limited phase noise targeted to act inside the synchrotron frequency spread, which is itself modified both by the second RF system and by intensity effects (beam loading and others). For a high intensity beam these latter effects can lead to a non-uniform emittance blow-up and even loss of stability for certain bunches in the batch. In this paper we present studies of the emittance blow-up achieved with high intensity beams under different conditions of both RF and noise parameters

Dependence of the Electron-Cloud Instability on the Beam Energy

The electron cloud (EC) can be formed in the beam pipe of a circular accelerator if the secondary emission yield (SEY) of the inner surface is larger than 1, and it can detrimentally affect the circulating beam. Understanding the underlying physics and defining the scaling laws of this effect is indispensable to steer the upgrade plans of the existing machines and the design of new ones. The single bunch EC instability (ECI) is shown to be strongly affected by the transverse beam size. Transversely, smaller beams going through an electron cloud generate higher electron peak densities and lower the intensity threshold to make the beam unstable. In particular, since higher energy beams have smaller transverse sizes (for equal normalized transverse emittances), the scaling of the ECI threshold with the beam energy turns out to be surprisingly unfavorable

Integrative analysis of SF-1 transcription factor dosage impact on genome-wide binding and gene expression regulation

Steroidogenic Factor-1 (SF-1) is a nuclear receptor that has a pivotal role in the development of adrenal glands and gonads and in the control of steroid hormone production, being also implicated in the pathogenesis of adrenocortical tumors. We have analyzed the mechanisms how SF-1 controls gene expression in adrenocortical cells and showed that it regulates different categories of genes according to its dosage. Significant correlations exist between the localization of SF-1-binding sites in chromatin under different dosage conditions and dosage-dependent regulation of gene expression. Our study revealed unexpected functional interactions between SF-1 and Neuron-Restrictive Silencer Factor/RE1-Silencing Transcription Factor (NRSF/REST), which was first characterized as a repressor of neuronal gene expression in non-neuronal tissues, in the regulation of gene expression in steroidogenic cells. When overexpressed, SF-1 reshapes the repertoire of NRSF/REST—regulated genes, relieving repression of key steroidogenic genes. These data show that NRSF/REST has a novel function in regulating gene expression in steroidogenic cells and suggest that it may have a broad role in regulating tissue-specific gene expression programs

Experimental studies on the SPS electron cloud

One of the most important limitations in the performances of the CERN-SPS is presently the Electron Cloud Instability (ECI). Hence, defining its dependence on energy with confidence is an indispensable asset to direct the efforts for all the upgrade studies. Macroparticle simulations carried out with the HEADTAIL code have shown that the ECI mechanism is subtle and the scaling laws valid for the Transverse Mode Coupling Instability cannot be applied to it . The reason lies in the fact that the electron dynamics, while a bunch is going through an electron cloud, is heavily affected by the transverse beam size. In fact, transversely smaller beams can enhance the electron pinch and lower the intensity threshold for the bunch to be unstable. Hence, higher energy beams, though more rigid, can be more unstable due to their smaller transverse size (with constant transverse normalized emittance). During the 2007 run a measurement campaign has been carried out at the CERN-SPS to prove experimentally the outcomes of macroparticle simulations

Bone sialoprotein is predictive of bone metastases in resectable non small cell lung carcinoma: A case–control study and prevalence data

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Experimental Study of the Electron Cloud Instability at the CERN SPS

The electron cloud instability limits the performance of many existing proton and positron rings. A simulation study carried out with the HEADTAIL code revealed that the threshold for its onset decreases with increasing beam energy, if the 6D emittance of the bunch is kept constant and the longitudinal matching to the bucket is preserved. Experiments have been carried out at the CERN-SPS to study the dependence of the vertical electron cloud instability on the energy and on the beam size. The reduction of the physical transverse emittance as a function of energy is considered in fact to be the main reason for the unusual dependence of this instability on energy

Characteristics of the patients referred to a Hypertension Unit between 1989 and 2003

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