Speaker
joao veloso
(university of aveiro)
Description
A new VUV single-photon gaseous photomultiplier with position capability will be presented. It is based on a triple cascade of two THGEM followed by a 2D-THCOBRA with a CsI photocathode deposited on the top electrode of the first structure. To allow high gain at low voltage a mixture of Ne/CH4 at atmospheric pressure was used. The gas mixture also provide excellent photoeletron extraction from the CsI photocatothe as well as full electron collection efficiency. The photomultiplier uses a spectrosil B window to allow the etection of photons in the VUV range (> 165 nm). For the experimental studies a Ar(Hg) lamp to generate the single VUV photons was used. Gains above 10⁶ were achieved at stable operation. The 2D-THCOBRA, in addition to an extra gain, also provides the position sensitivity through two orthogonal resistive lines connecting the electrodes strips in both sides of the structure. The image capability allows to “see” the shape of the first structure of the cascade from where the photoelectrons are emitted and focused into the oles. This indicate that position resolutions bellow 400 μm (FWHM) for single photons can be achieved with the proposed photomultiplier.
