PS-XXI, a new synchrotron for the LHC injector

The CERN PS is the oldest link in the LHC injector chain. A separate function substitute synchrotron is discussed. It would keep the versatility of the present machine and have a higher extraction energy to relax the tolerance on the microwave instability threshold at injection into the SPS. Its essential property would be an adjustable h variation near the isochronous regime to meet the requirements imposed by bunch compression at ejection. It would also be equipped with all the correction systems of a modern machine

Beams in the CERN PS complex after the RF upgrades for LHC

In preparation for the Large Hadron Collider (LHC), extensive modifications have been made to the RF equipment of the PS Booster (PSB) and of the PS during the winter shut down 97-98. Low-frequency RF systems (0.6 - 1.8 MHz and 1.2 - 3.9 MHz) have been installed in the PSB and fixed frequency (40 and 80 MHz) systems in the PS. The longitudinal characteristics of all beams are changed to make the best use of the new capabilities. This paper summarises the characteristics of the new equipment and describes the RF gymnastics used to generate the various beams. The performances achieved so far ar e reported and compared to former results. Future plans are sketched

The Influence of Large-Scale Airborne Particle Decline and Traffic-Related Exposure on Children’s Lung Function

Between 1991 and 2000, ambient air pollution in East Germany changed to resemble West German pollution levels: The concentration of total suspended particles (TSPs) decreased on a broad scale while traffic increased. During that time, we analyzed total lung capacity (TLC) and airway resistance (R(aw)) of East and West German children. We tested children 5–7 years of age (n = 2,574) with cooperation-independent body plethysmography in repeated cross sections. We used random-effect models to determine the mutually adjusted association between lung function and short-term and chronic particle exposure and its interaction with living near a busy road. Annual averages of TSPs declined from 77 to 44 μg/m(3); averages on the day of investigation declined from 133 to 30 μg/m(3). Differences in lung function between East and West German children vanished during the investigation time. The association of TSPs with R(aw) and TLC was stronger in children living > 50 m away from busy roads. East German children from this group had an R(aw) 2.5% higher [95% confidence interval (CI), 0.0–5.1%] per 40-μg/m(3) increase of daily TSP averages. TLC decreased by 6.2% (95% CI, 0.04–11.6%) per 40-μg/m(3) increase in annual mean TSPs, and this effect was equally pronounced in East and West Germany. TSP exposure decreased on a broad scale between 1991 and 2000. Lower concentrations of TSPs were associated with better measures of lung function in 6-year-old children. For children living near busy roads, this effect was diminished

Shape Changes of Self-Assembled Actin Bilayer Composite Membranes

We report the self-assembly of thin actin shells beneath the membranes of giant vesicles. Ion-carrier mediated influx of Mg2+ induces actin polymerization in the initially spherical vesicles. Buckling of the vesicles and the formation of blisters after thermally induced bilayer expansion is demonstrated. Bilayer flickering is dominated by tension generated by its coupling to the actin cortex. Quantitative flicker analysis suggests the bilayer and the actin cortex are separated by 0.4 \mum to 0.5 \mum due to undulation forces.Comment: pdf-file, has been accepted by PR

Increasing the Proton Intensity of PS and SPS

Recently, a series of meetings were organised with PS and SPS participants, to discuss the possibilities of increasing the proton intensity on the SPS targets (with particular emphasis to CNGS) as well as ISOLDE and nTOF. Increasing the brilliance of the LHC beam, as required for ultimate LHC performance, was also discussed. Several schemes were proposed, as a staged approach, i.e. starting from the most simple and cheap, though difficult, to the more advanced and expensive. After comparing the advantages and disadvantages of the various methods, three basic schemes were retained as candidates for further investigations and as good / necessary starting points for further improvements. Chapter 1 is devoted to PSB and PS issues and contains essentially a description of the three selected schemes. Chapter 2 deals with limitations in the SPS. Chapter 3 is a synthesis of basic conclusions. In the Appendix, a work-plan is presented for PSB and PS theoretical and experimental studies with a time estimate for preliminary results

Performance of the LHC Pre-Injectors

The LHC pre-injector complex, comprising Linac 2, the PS Booster (PSB) and the PS, has undergone a major upgrade in order to meet the very stringent requirements of the LHC. Whereas bunches with the nominal spacing and transverse beam brightness were already available from the PS in 1999 [1], their length proved to be outside tolerance due to a debunching procedure plagued by microwave instabilities. An alternative scenario was then proposed, based on a series of bunch-splitting steps in the PS. The entire process has recently been implemented successfully, and beams whose longitudinal characteristics are safely inside LHC specifications are now routinely available. Variants of the method also enable bunch trains with gaps of different lengths to be generated. These are of interest for the study and possible cure of electron cloud effects in both the SPS and LHC. The paper summarizes the beam dynamics issues that had to be addressed to produce beams with all the requisite qualities for the LHC

Design of a 2.2 GeV Accumulator and Compressor for a Neutrino Factory

The proton driver for a neutrino factory must provide megawatts of beam power at a few GeV, with nonosecond long bunches each containing more than 1x1012 protons. Such beam powers are within reach of a high-energy linac, but the required time structure cannot be provided without accumulation and compression. The option of a linac-based 2.2 GeV proton driver has been studied at CERN, taking into account the space charge and stability problems which make beam accumulation and bunch compression difficult at such a low-energy. A solution featuring two rings of approximately 1 km circumference has been worked out and is described in this paper. The subjects deserving further investigation are outlined

LHC Luminosity and energy upgrade: A Feasibility Study

We discuss a possible staged upgrade of the LHC and of its injectors, with a view to increasing the luminosity from the nominal 10**34 cm**-2s**-1 to 10**35 cm**-2s**-1 in each of the two high-luminosity experiments. We also consider possible scenarios for an upgrade to a proton beam energy of about 14 TeV. Starting from beam dynamics considerations and fundamental limitations of the hardware subsystems, we derive realistic requirements for the major components, such as superconducting magnets, cryogenic and RF systems, beam dump and vacuum. We also discuss a novel approach to the optimization of the collider performance, compatible with the beam-beam limit for high intensity proton bunches or long "super-bunches", and sketch a new design of the interaction regions, including an alternative beam crossing scheme. Finally we identify further studies required for an LHC performance upgrade and propose an R&D programm

Transverse Performance of the Proton Beam Delivered by the CERN PS Complex for the Future LHC

The performance of the CERN LHC will depend heavily on the high-brightness beam delivered by the injector chain. In 1999, after completion of the programme of hardware upgrades of the PS Complex, a major effort was devoted to producing a proton beam with the nominal transverse characteristics foreseen for LHC operation. This paper focuses on the different beam dynamics issues encountered during the setting up of such a beam, in the Linac2, the PS-Booster (PSB), the PS and the TT2 transfer line to the SPS. During the setting-up, single-particle issues, like stop-band compensation, correction of injection oscillations during the double-batch injection process, and the correction of the high-energy closed orbit in the PS, were addressed. Furthermore, collective effects, such as high-order head-tail instabilities induced by the resistive-wall impedance, were observed and cured. The compensation of these harmful phenomena permitted to achieve the goal, namely the generation of small transverse beam emittances and their conservation along the chain of different machines