  Many of the characteristics of Silicon Photomultipliers (SiPMs), such as high
Photon Detection Efficiency (PDE), are well matched to the requirements of the
cameras of the Small-Sized Telescopes (SSTs) proposed for the Cherenkov
Telescope Array. In fact, compared to a single mirror, the double mirror
Schwarzschild Couder configuration provides a much better Point Spread Function
over a large field of view. It allows better correction of aberrations at large
off axis angles and facilitates the construction of compact telescopes.
Moreover, the small plate scale of the dual-mirror SSTs allows the use of SiPM
detectors despite their small pixel sizes. These sensors have two further
advantages compared to the Photo Multipliers Tubes: the low cost and the
possibility to observe in very high Night Sky Background (NSB) light level
without any damage. However, one area in which SiPM performance has required
improvement is Optical CrossTalk (OCT), where multiple avalanches are induced
by a single impinging photon. OCT, coupled with the typical NSB rate of 25
MCnts/s per pixel during Cherenkov observations, can place severe constraints
on the triggering capability of the cameras. This paper describes the
performance of novel Low Voltage Reverse (LVR) 2nd and 3rd generation Multi
Pixel Photon Counters manufactured by Hamamatsu Photonics. These are designed
to have both enhanced PDE and reduced OCT. Two 7 x 7 mm2 S14520 LVR2 MPPCs with
75 um microcells are tested and compared with detectors of the same pixel size
with 50 um microcells. A comparative analysis of a 3 x 3 mm2 S14520 LVR2 device
and an S14520 LVR3 device is also carried out, demonstrating that the LVR3
gives better photon detection in the 240 380 nm wavelength range. Finally, the
effect of an infrared filter on the OCT is analysed.
