Subarachnoid Haemorrhage: epidemiological studies on aetiology and outcome

Subarachnoid haemorrhage (SAH) is bleeding into the subarachnoid space ‒ the area between the arachnoid membrane and the pia mater surrounding the brain. SAH occurs spontaneously or can be caused by traumatic injury of the head. Spontaneous SAH is caused by rupture of an intracranial aneurysm in 85 percent of cases. In this thesis we consider both spontaneous SAH in general and in several studies aneurysmal SAH specifi cally. Reliable knowledge about the risks of (aneurysmal) SAH in diff erent populations will help in planning, screening and prevention strategies and in predicting the prognosis of individual patients. The overall incidence of SAH is in general between 5 and 10 per 100,000 person years. However, in Japan and Finland rates are as high as 20 per 100,000 person years. This can partly be explained by genetic and environmental diff erences between these and other countries. The incidence increases with age; and from midlife onwards incidence is higher in women than in men. The reasons for this higher incidence in women are not clear, but hormonal factors (including hormonal medication) have been suggested as a possible explanation

Isochronous Optics and Related Measurements in EPA

The time structure of the CLIC (Compact Linear Collider) drive beam is obtained by the combination of electron bunch trains in rings using RF deflectors [1]. The rings must be isochronous, in order to preserve the bunch length and separation during the combination process (4-5 turns). A first isochronicity test has been performed in the CERN EPA (Electron Positron Accumulator) ring. The calculated isochronous lattice can be obtained by changing the strength of existing quadrupole families without hardware modifications. Measurements of the synchrotron frequency and of the beam's time structure have been made for both the normal and the isochronous lattices. Streak camera measurements of the bunch length have been used to tune the lattice around the isochronous point. The bunch length increases rapidly over a few turns in the normal case, while no appreciable bunch lengthening is observed over 50 turns in the isochronous case. A quantitative evaluation of the momentum compaction is obtained by measuring the bunch separation in a train when close to, and far from, the isochronous condition. Plans for future tests in the EPA ring are also outline

Momentum Cleaning in the CERN LHC

This paper describes the optimization of the optics and the collimator geometry for the momentum cleaning insertion of the LHC. To collimate the off-momentum secondary halo without disturbing the circ ulating beam, the normalized dispersion in IR3 is made as large as in the arcs. The jaw locations and orientations are numerically optimized to reduce the momentum-dependent halo amplitude. The second ary halo is kept within the available aperture for momentum deviations up to 0.44%, where the horizontal aperture is 4$\sigma\, compared to 12$\sigma\ on-momentum

Beam Dynamics for the Preliminary Phase of the New CLIC Test Facility (CTF3)

In the framework of the CLIC (Compact Linear Collider) RF power source studies, the scheme of electron pulse compression and bunch frequency mulitiplication, using injection by RF deflectors into an isochronous ring, will be tested, at low charge, during the preliminary phase of the new CLIC Test Facility (CTF3) at CERN. In this paper, we describe the beam dynamics studies made in order to assess the feasibility of the bunch combination experiment, as well as the related beam measurements performed on the LEP Pre-Injector complex (LPI) before its transformation into CTF

Beam Dynamics for the CTF3 Preliminary Phase

In the framework of the CLIC RF power source studies, the new scheme of electron pulse compression and bunch frequency multiplication, using injection by RF deflectors into an isochronous ring, will be tested at CERN during the CTF3 preliminary phase. The present LPI complex will be modified in order to allow a test of this scheme at low charge. The design of the new front-end, of the modified linac, of the matched transfer line, and of the isochronous ring lattice is presented here.The results of the related beam dynamics studies are also discussed

A Low Charge Demonstration of Electron Pulse Compression for the CLIC RF Power Source

The CLIC (Compact Linear Collider) RF power source is based on a new scheme of electron pulse compression and bunch frequency multiplication using injection by transverse RF deflectors into an isochronous ring. In this paper, we describe the modifications needed in the present LEP Pre-Injector (LPI) complex at CERN in order to perform a low-charge test of the scheme. The design of the injector (including the new thermionic gun), of the modified linac, of the matched injection line, and of the isochronous ring lattice, are presented. The results of preliminary isochronicity measurements made on the present installation are also discussed.Comment: 3 pages, 5 figures, submitted to the LINAC 2000 Conferenc

CLIC simulations from the start of the linac to the interaction point

Simulations for linear colliders are traditionally performed separately for the different sub-systems, like damping ring, bunch compressor, linac, and beam delivery. The beam properties are usually passed from one sub-system to the other via bunch charge, RMS transverse emittances, RMS bunch length, average energy and RMS energy spread. It is implicitly assumed that the detailed 6D correlations in the beam distribution are not relevant for the achievable luminosity. However, it has recently been shown that those correlations can have a strong effect on the beam-beam interaction. We present first results on CLIC simulations that integrate linac, beam delivery, and beam-beam interaction. These integrated simulations also allow a better simulation of time-dependent effects, like ground perturbations and interference between several beam-based feedbacks