Nucl. Instrum. Methods Phys. Res., A Nucl. Instrum. Methods Phys. Res., A 0167-5087 THGEM based photon detector for Cherenkov imaging applications Alexeev M INFN, Turin Piemonte Orientale U., Alessandria Birsa R INFN, Trieste Bradamante F INFN, Turin Bressan A INFN, Turin Chiosso M INFN, Turin Turin U. Ciliberti P INFN, Trieste Trieste U. Croci G CERN Colantoni M L INFN, Turin Dalla Torre S INFN, Trieste Duarte Pinto S CERN Denisov O INFN, Turin Diaz V INFN, Trieste Ferrero A INFN, Turin Turin U. Finger M Charles U. Finger M Jr Charles U. Fischer H Freiburg U. Giacomini G INFN, Trieste Bari U. Giorgi M INFN, Trieste Trieste U. Gobbo B INFN, Trieste Heinsius F H Freiburg U. Herrmann F Freiburg U. Jahodova V Liberec Tech. U. Königsmann K Freiburg U. Lauser L Freiburg U. Levorato S INFN, Trieste Trieste U. Maggiora A INFN, Turin Martin A INFN, Trieste Trieste U. Menon G INFN, Trieste Nerling F Freiburg U. Panzieri D INFN, Turin Piemonte Orientale U., Alessandria Pesaro G INFN, Turin Polak J Liberec Tech. U. INFN, Trieste Rocco E INFN, Turin Turin U. Ropelewski L CERN Sauli F TERA, Novara Sbrizzai G INFN, Trieste Trieste U. Schiavon P INFN, Trieste Trieste U. Schill C Freiburg U. Schopferer S Freiburg U. Slunecka M Charles U. Sozzi F INFN, Trieste Trieste U. Steiger L Liberec Tech. U. Sulc M Liberec Tech. U. Takekawa S INFN, Trieste Trieste U. Tessarotto F INFN, Trieste Wollny H Freiburg U. 2010 617 396 397 We are developing a single photon detector for Cherenkov imaging counters. This detector is based on the use of THGEM electron multipliers in a multilayer design. The major goals of our project are ion feedback suppression down to a few per cent, large gain, fast response, insensitivity to magnetic fields, and a large detector size. We report about the project status and perspectives. In particular, we present a systematic study of the THGEM response as a function of geometrical parameters, production techniques and the gas mixture composition. The first figures obtained from measuring the response of a CsI coated THGEM to single photons are presented. research-article