The X-HPD—A modern implementation of a SMART concept

✍ Scribed by André Braem; Christian Joram; Jacques Séguinot; Paola Solevi; Léo Pierre

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 481 KB
• Volume: 602
• Category: Article
• ISSN: 0168-9002
• DOI: 10.1016/j.nima.2008.12.058

✦ Synopsis

The concept of hybrid photodetectors which combine a large area photocathode with a crystal scintillator anode in the centre of a hemispherical vacuum tube was demonstrated first with the Philips SMART tubes and, more recently, with the QUASAR tubes of the Lake Baikal experiment. Photoelectrons from the cathode are accelerated by a potential difference of 20-30 kV and deposit their kinetic energy in the scintillator (or Phosphor). The generated scintillation light is detected by a small and low cost photodetector, e.g. a conventional PMT. The X-HPD study is a variation of this concept aiming at improved performance and maximum simplicity. The glass envelope is essentially spherical and a spatial scintillator crystal is mounted in its centre. The spherical symmetry leads to a uniform collection efficiency and very small intrinsic time spread over the full viewing angle of 1201 (3p solid angle). We report about test results of a the first X-HPD prototypes of 208 mm diameter with cylindrical and conical LYSO crystal anodes.