[en] The betatronic motion of a particle in a circular accelerator is analysed using the transfer map description of the magnetic lattice. In the linear case the transfer matrix approach is shown to be equivalent to the Courant-Snyder theory: In the normal coordinates' representation the transfer matrix is a pure rotation. When the nonlinear effects due to the multipolar components of the magnetic field are taken into account, a similar procedure is used: a nonlinear change of coordinates provides a normal form representation of the map, which exhibits explicit symmetry properties depending on the absence or presence of resonance relations among the linear tunes. The use of normal forms is illustrated in the simplest but significant model of a cell with a sextupolar nonlinearity which is described by the quadratic Henon map. After recalling the basic theoretical results in Hamiltonian dynamics, we show how the normal forms describe the different topological structures of phase space such as KAM tori, chains of islands and chaotic regions; a critical comparison with the usual perturbation theory for Hamilton equations is given. The normal form theory is applied to compute the tune shift and deformation of the orbits for the lattices of the SPS and LHC accelerators, and scaling laws are obtained. Finally, the correction procedure of the multipolar errors of the LHC, based on the analytic minimization of the tune shift computed via the normal forms, is described and the results for a model of the LHC are presented. This application, relevant for the lattice design, focuses on the advantages of normal forms with respect to tracking when parametric dependences have to be explored. (orig.)

[en] This Report summarizes the results of 12 months' activities of the Working Group on Precision Calculations for the Z Resonance, run at CERN in 1994. The main goal of the Working Group was to present a update of studies on radiative corrections for Z-resonance processes, integrating all new results that had appeared since the previous Workshop on ''Z Physics at LEP 1'', held in 1989. The Report is, however, more than a mere collection of the proceedings of the three general meetings held on January 14, March 31 and June 13, 1994. Three subgroups have been working in three related fields: electroweak physics, QCD at the Z resonance and Bhabha scattering in the luminosity region. An attempt has been made to present the final reports from these subgroups in a complete and homogeneous form. The subgroups' contributions in the three fields correspondingly comprise the three main parts of the Report. (orig.)

[en] Secondary Emission Monitors (SEMs) are used at the SPS for measurements of the absolute proton beam intensity. As an accurate measurement was recently required by the NA56 (SPY) experiment, the responses of all the SEMs used in the SPS North Area, including those used for NA56, were calibrated. The independent measurement of the absolute proton intensity needed for this calibration was obtained by an activation method, where the radioactivity induced in a thin aluminium foil is measured with a gamma counter immediately after a short exposure of the foil to the proton beam. The foil activity was in turn calibrated using the absolute proton intensity measurements provided by the Beam Current Transformers (BCTs) available in the West Area Neutrino Facility. A description of the experimental method and results of the calibration are given. SEM calibration factors were determined with an error that, even in the worst case, does not exceed 3%. The response per unit proton intensity of the new titanium SEMs installed in 1995 is about 9% smaller than that of the traditional aluminium SEMs. The measured calibration factor of the titanium monitor used by NA56 has been shown to be stable within ±1% over a period of almost one month. By combining this additional uncertainty to the error on the determination of the calibration factor from the activation measurement, the absolute proton intensity delivered to NA56 could be measured with an uncertainty of 1.7%. (orig.)

[en] This catalogue summarizes radiation damage test data on thermoplastic and thermoset resins and composites. Most of them are epoxy resins used as insulator for magnet coils. Many results are also given for new engineering thermoplastics which can be used either for their electrical properties or for their mechanical properties. The materials have been irradiated either in a ⁶⁰Co source, up to integrated absorbed doses between 200 kGy and a few megagrays, at dose rates of the order of 1 Gy/s, or in a nuclear reactor at dose rates of the order of 50 Gy/s, up to doses of 100 MGy. The flexural strength, the deformation and the modulus of elasticity have been measured on irradiated and non-irradiated samples, according to the recommendations of the International Electrotechnical Commissions. The results are presented in the form of tables and graphs to show the effect of the absorbed dose on the measured properties. (orig.)

[en] Irradiation tests of a number of essential components for use in the service electronics of the Leading Proton Spectrometer (LPS) have been undertaken. The components are simple medium-scale integrated circuits such as Transistor Transistor Logic (TTL) buffers from the Advanced Low-power Schottky (ALS), Low-power Schottky (LS), and Fast (F) families, optocouplers, and balanced line drivers and receivers. More complex circuits, such as a Fuse Programmable Array Logic chip, programmed as a 6-bit counter, and a complete switched-mode power supply unit were also tested. Further, monolithic voltage regulators with an output potential of 5 V, and 10 MHz quartz oscillator hybrids were tested. The different radiation fields were X-rays (80 keV), ⁶⁰Co gamma rays, electrons (2.5 MeV), and a high-energy proton accelerator environment. Depending on the device degradation, the maximum dose was up to 0.8 MGy. It is shown that the simple choice of circuit family can achieve a hardness level of nearly 1 MGy(Si), provided that one is prepared to make some sacrifices in power consumption, and in speed. It has been found that this radiation hardness can be reached with LS technology. The maximum level of about 1 MGy(Si) was obtained with 2.5 MeV electrons, which is equivalent to a 1 MeV neutron fluence of the order of 6x10¹³ n/cm². (orig.)

[en] This paper describes the alignment (completed in the spring of 1995) of the rebuilt CERN West Area neutrino beam line which is directed to the two neutrino experiments CHORUS and NOMAD. The neutrino target (T9)and the magnetic horn were aligned with respect to the proton beam using the intensity of the secondary particles produced and the intensity and profile of the muons detected in the pits in the beam line shielding. The improved geometry provides a better-centred neutrino beam (within 5 cm of the nominal centre) and a significant increase in the neutrino flux of 8% at the experiments. (orig.)

[en] Future multi-TeV particle accelerators like the CERN Large Hadron Collider (LHC) will use superconducting magnets where organic materials will be exposed to high radiation levels at temperatures as low as 2 K. A representative selection of organic materials comprising insulating films, cable insulations, and epoxy-type impregnated resins were exposed to neutron and gamma radiation of a nuclear reactor. Depending on the type of materials, the integrated radiation doses varied between 180 kGy and 155 MGy. During irradiation, the samples were kept close to the boiling temperature of liquid nitrogen i.e. ∼ 80 K and thereafter stored in liquid nitrogen and transferred at the same temperature into the testing device for measurement of tensile and flexural strength. Tests were carried out on the same materials at similar dose rates at room temperature, and the results were compared with those obtained at cryogenic temperature. They show that, within the selected dose range, a number of organic materials are suitable for use in the radiation field of the LHC at cryogenic temperature. (orig.)

[en] In these lectures the concept of a high-energy, high-luminosity μ⁺-μ^- collider is developed. A μ⁺-μ^- collider would provide heavy lepton collisions, with unique capabilities in the exploration of Higgs bosons at 100-180 GeV energies, and it could be extended to multi-TeV energies. A μ⁺-μ^- collider requires a high-intensity proton source for pion production, a high-acceptance decay channel to collect muons from pion decay, a muon cooling system, a rapid acceleration system, and a high-luminosity collider ring for the collisions of short, intense μ⁺-μ^- bunches. Critical problems exist in each of the collider concept components, and in the interaction-region detectors needed to analyse the collisions. These problems and the search for solutions within the current μ⁺-μ^- collider research programme are described. (orig.)

[en] In the past decade, calorimetry based on scintillating plastic fibres as active elements was developed from a conceptual idea to a mature detector technology, which is nowadays widely applied in particle physics experiments. This development and the performance characteristics of representative calorimeters, both for the detection of electromagnetic and hadronic showers, are reviewed. We also discuss new information on shower development processes in dense matter and its application to calorimetric principles that has emerged from some very thorough studies that were performed in the framework of this development. (orig.)

[en] In the two decades since the introduction of the X-ray scanner into radiology, medical imaging techniques have become widely established as essential tools in the diagnosis of disease. As a consequence of recent technological and mathematical advances, the non-invasive, three-dimensional imaging of internal organs such as the brain and the heart is now possible, not only for anatomical investigations using X-ray but also for studies which explore the functional status of the body using positron-emitting radioisotopes. This report reviews the historical and physical basis of medical imaging techniques using positron-emitting radioisotopes. Mathematical methods which enable three-dimensional distributions of radioisotopes to be reconstructed from projection data (sinograms) acquired by detectors suitably positioned around the patient are discussed. The extension of conventional two-dimensional tomographic reconstruction algorithms to fully three-dimensional reconstruction is described in detail. (orig.)