K Hübner

The Large Hadron Collider (LHC) in the LEP tunnel

After the remarkable start-up of LEP, the installation of a Large Hadron Collider, LHC, in the LEP tunnel will open a new era for the High Energy Physics. This report summarizes the main LHC parameters and subsytems and describes the more recent studies and developments.

Effects of Space Charge and Reactive Wall Impedance on Bunched Beams

Space charge and reactive wall impedance create longitudinal forces inside the bunch which change the incoherent phase oscillation frequency, the bunch length and the size of the RF-bucket. These effects have been investigated with bunched beams in the ISR. By measuring the shift of the quadrupole mode phase oscillation frequency, the strength of the self-forces was determined. The inductive wall is dominant and its impedance (divided by the mode number) was measured to be |Z|/n z 26 Ohms. An increase of bunch length with current was measured. It can be explained by the inductive impedance up to a certain current; beyond that an excessive, unexplained bunch lengthening occurs. The reduction of the bucket size affects the stacking process. By correcting for it, an increased density of the stacked beam was achieved. Ez = -e az [4 g0 dz (1)

A Computer Code for the Calculation of Beam Stability in Circular Electron Machines

A computer program is presented which assists the designer of a circular electron accelerator or storage ring in finding out the limits of beam stability. The most prominent longitudinal and transverse instabilities are taken into account with emphasis on coherent bunch oscillations.

Improvement in Luminosity, Background and Chamber Protection with Beam Scrapers in the ISR

The Intersecting Storage Rings (ISR) are equipped with beam scrapers used for various purposes such as improving luminosity, reducing background, beam diagnostics and for protection of machine components. A description is given of the different types of scrapers and of the results in the various applications obtained during the last year. In particular, the substantial improvements in luminosity and background by scraping are described.

An E-P Facility in the CERN SPS

A 25 GeV electron (or positron) storage ring installed in the SPS tunnel above the proton synchrotron would provide e-p collisions with a luminosity in the range of 10/sup 31/ to 10/sup 32/ cm/sup -2/ s/sup -1/. The collisions would normally take place at an intermediate plateau of the SPS-cycle up to 270 GeV, and could be followed by acceleration and extraction of the proton beam for fixed target experiments. The feasibility of such a facility is demonstrated and the essential features presented.

Fifty years of the CERN Proton Synchrotron : Volume 2

This report sums up in two volumes the first 50 years of operation of the CERN Proton Synchrotron. After an introduction on the genesis of the machine, and a description of its magnet and powering systems, the first volume focuses on some of the many innovations in accelerator physics and instrumentation that it has pioneered, such as transition crossing, RF gymnastics, extractions, phase space tomography, or transverse emittance measurement by wire scanners. The second volume describes the other machines in the PS complex: the proton linear accelerators, the PS Booster, the LEP pre-injector, the heavy-ion linac and accumulator, and the antiproton rings.

Electron Beam Dynamics in the CERN PS

The 28 GeV proton synchrotron (PS) forms part of the chain of LEP injectors with the rôle to accelerate positrons and electrons from 0.6 GeV, the operating energy of the Electron/Positron Accumulator (EPA), to 3.5 GeV, the positron/electron injection energy of CERNs 400 GeV proton synchrotron (SPS) which then accelerates the particles to 20 GeV. The PS used as an electron synchrotron has to supply the SPS with 8 bunches at an intensity of Nb = 8 × 109 particles per bunch. Bunch length and energy spread must be chosen carefully to avoid transverse and longitudinal single-bunch instabilities (turbulence) associated with high peak currents in the SPS. Analysis of the beam dynamics in the combined function lattice of the PS shows that this requirement can be fulfilled if the damning-partition numbers are changed. A Robinson Wiggler is proposed for this purpose and a new additional RF system is needed to produce the required bunch dimensions in longitudinal phase space.

Design and construction of the ISR

The emergence of the ISR project at CERN is described in the light of the situation at CERN at the end of the 1950s when the CERN Proton Synchrotron (PS) was still under construction. The discussions leading to the project are put into context with world-wide efforts to build larger and more powerful accelerators at that time; the evolution of the project before approval is sketched. The basic design considerations and the most significant technological choices are explained. The construction period is summarized by highlighting important milestones and the performance achieved during commissioning in 1971, the first year of running, is given.The emergence of the ISR project at CERN is described in the light of the situation at CERN at the end of the 1950s when the CERN Proton Synchrotron (PS) was still under construction. The discussions leading to the project are put into context with world-wide efforts to build larger and more powerful accelerators at that time; the evolution of the project before approval is sketched. The basic design considerations and the most significant technological choices are explained. The construction period is summarized by highlighting important milestones and the performance achieved during commissioning in 1971, the first year of running, is given.

Studies of 400 GeV superconducting proton storage rings

A study has been made of the feasibility of building Large Storage Rings (LSR) at CERN using superconducting dipoles and quadrupoles with the 400 GeV proton synchrotron, SPS, serving as injector. Proton-proton collisions at centre-of-mass energies of up to 800 GeV can be obtained in six interaction regions. Two of these provide luminosities exceeding 1033 cm−2 s−1 and would be dedicated to large-transverse-momentum physics. The other four p-p intersections offer much experimental flexibility at somewhat lower luminosity. Provision is made to add an electron storage ring of 20–25 GeV to obtain e-p collisions at up to 200 GeV centre-of-mass energy with a luminosity of 1032 cm−2 s−1 in each of two special e-p interaction regions. Antiproton-proton collisions could be obtained by a minor rearrangement of some elements in two of the interaction regions.

Measurement of Intra-Beam Scattering in the ISR

The growth of proton beams coasting for a long time with very low loss-rate has been measured. A comparison with the growth-rate expected from intrabeam scattering is presented. At lower energy measured and calculated growth agree. At higher energy the measured growth tends to exceed the calculated one by about a factor of 3. The growth in momentum spread is in accordance with theory.