NEW BEAM PROFILE MONITOR BASED ON GEM DETECTOR FOR THE AD TRANSFER AND EXPERIMENTAL LINES

Many multi-wire proportional chambers, (MWPC's), are installed on the CERN Antiproton Decelerator (AD) trans- fer and experimental lines. They are used for the steer- ing and profile measurement of the low energy antipro- ton beam that is extracted at the energy of 5.3 MeV from the AD machine. At this very low energy the standard MWPC's are not only destructive for the beam but also perturb strongly the 2D profile measurement. These cham- bers are also based on technology that is outdated and in recent years have shown to be fragile and expensive to re- pair. For these reasons a new profile monitor, based on a Gas Electron Multiplier (GEM) detector is under develop- ment as a possible replacement of the MWPC's. This new profile monitor will enable high precision, true 2D profile measurements of the low energy antiproton beam. In this paper, we present the modification of the standard GEM detector required by our specific application and the first results of the profile monitor with antiproton beams.