Edouard Rossa

High-rate photomultiplier-base and precise timing calibration

Four hodoscopes with 64 channels each have been designed to run in the high intensity muon beam of the SPS (up to 10 9 muons/s). Despite a transmission at 310 m the double pulse resolution is ≤ 5 ns and a time jitter of about 100 ps is achieved. The synchronisation is done with a sharp laser pulse.

Real time single shot three‐dimensional measurement of picosecond photon bunches

A new method using a streak camera to monitor the particle density distribution in three dimensions in space was developed for the LEP (Large European Electrons Positrons collider). This paper provides a basic overview of the experiment. The synchrotron radiation emitted by the particles creates the image of the density distribution of particles in the bunches. The optical set‐up allows us to see the front view or the top and side view of the photon bunch simultaneously at successive turns. The practical limits of our set up are discussed and some examples of bunch oscillations in three dimensions are given.

Investigation of optical properties of scattering solutions by time-resolved transmittance

The optical properties of controlled size latex particles suspended in water have been investigated by using two different time-resolved transmittance set-ups. Least-mean square fitting between experimental data and analytical solution to diffusion approximation equation has given values of optical parameters in good agreement with the predictions of the Mie theory. In this way, the validity of these predictions was checked in the investigated experimental conditions and the data analysis confirms that time-resolved transmittance can be a reliable technique to measure the optical properties of scattering solutions.

Time Autocorrelation Of Short (σ = 40 Ps), Single Shot Intense X-Ray Pulses

The aim is to monitor the longitudinal distribution of electron bunches in LEP (the Large European Electron Positron collider) via the intense X-ray synchrotron radiation they emit. Very fast photoconductors inserted in an electronic circuit produce a time autocorrelation of the impinging X-ray pulses. The principle of the detector and its present status is given in this report.

Vertical bunch-size measurement at LEP using very fast x-ray detectors

Abstract Very fast X-ray detectors have been developed for beam diagnostics in the LEP machine (Large Electron-Positron Collider). Picosecond CdTe photoconductors allow the measurement of the vertical dimensions of electron and positron bunches (length 50 ps and vertical size 300 μm) during a single beam passage. Intense synchrotron X-rays emitted by the LEP beams are measured each turn by two sets of detectors. The transverse profile detector and its associated electronics are described in detail. A pulsed bias is used to gate the detector for a period of time as short as 10 ns. The profile is then digitized in 10 μs and saved in memory. Typical results obtained in real time with LEP beams are used to illustrate the performance of the detector. The linear pulse bias provides a new way of simultaneously making single-shot X-ray measurements of the longitudinal and vertical bunch centre of gravity, and the vertical profile.