High sensitivity beam intensity and profile monitors for the SPS extracted beams

Secondary emission monitors using caesium iodide coated thin aluminium foils have been installed in the SPS transfer channels to monitor the intensity of the extracted heavy ion beams. Tests have shown an increase by a factor twenty of their sensitivity with respect to bare aluminium foils. Luminescent screens viewed with TV cameras are used to monitor the position and the profiles of the extracted beams. Various luminescent screen materials have been tested. Results on chromium doped alumina, thallium doped caesium iodide and quartz are reported. A dynamic range of 10³ in beam intensities can be achieved by using these three materials in turn in the usual three screen tanks. Intensifiers used together with CCD cameras and video frame grabbers with incorporated projection calculations are used in conjunction with these screens. Results with heavy ions in the transfer channels and with protons extracted from circulating beams in the SPS are given. Detection sensitivities down to a few tens of protons per video frame have been observed