The C.I.E.L. experiment was first introduced by Michel Lavollée (France) in the middle of the 90's to study molecular photo-fragmentation after inner-shell excitation. At that time, the main idea was to improve the traditional coincidence experiments between electrons and ions (usually called PEPICO, PEPIPICO, PE(PI)nCO...) because they were suffering of a lake of information to understand easily the photo-physical mechanisms, especially when the size of the molecules increazes and/or molecular rearrangement takes place. Since the first generation of experiments were giving just the projection of the momentum of each particle along the spectrometer axis, it was straight foward that one should aim to get a complete set of data to reconstruct the momenta of each particle. This was done simply by adding a Position Sensitive Detector (PSD) in order to know the position of each hit on the detector. Therefore, the new generation of experiment was called C.I.E.L. where the acronym stands for Coincidence-Ions-Electrons-Localisés. The official web site can be found at Michel Lavollée. Simultaneoulsy, or a little earlier, Horst Schmidt-Böking (Germany) had also started the developement of new PSD, a little different than the one of Michel Lavollée aimed to do. The official German web site can be found at Roentdek .

In both cases the specification of this new PSDs where extremelly demanding on the time and spatial resolutions. As a matter of fact, it is easy to get an extremelly good spatial resolution with a rather poor timing issue, or a good time resolution with a poor localisation of particles. Originately, the key point of the C.I.E.L's detectors were to achieve (with moderate resolution) a very good timing issue, and especially a extremelly good multi-hit resolution to not loose particles which hit the detector together. The other type of detectors were actually based on the opposite trend, i.e. good spatial resolution but a (rather) poor multi-hit capability. It is clear nowadays with the recent development of fast computers, fast electronic devices that these two kind of detector will partially fusion (hybrid-detector) within 10 years and other detectors will emerge.

Last edited by Mathieu Gisselbrecht at Oct 7, 2008 10:47 AM - Edit content