The quality of SiFAP (Silicon Fast Astronomical Photometer) at the TNG has already shown its ability to easily detect optical pulses from transitional millisecond pulsars and from other slower neutron stars. Up to now the photometer based on Silicon Photo Multipliers manufactured by Hamamatsu Photonics (MPPC, Multi Pixel Photon Counter) was mounted (on and manually aligned with) a MOS mask at the F/11 focal plane of the telescope. In order to have a more versatile instrument with the possibility to remotely center and point several targets during the night we have decided to build a new mechanical support for the MPPCs and mount it on the Namsyth Interface (NI), where originally OIG and later GIANO were hosted. The MPPC module devoted to observe the target will be placed at the center of the FoV (on-axis), while the reference signal will be collected from a peripheral star in the FoV (Field of view) by means of the MPPC module that will be set at this position by a combination of a linear stage movement and a derotator angle. At the same time we have introduced the option for a polarimetric mode, with a 3rd MPPC module and a polarizing cube beam-splitter that separates the states between this and the on axis MPPC. SiFAP has been developed with 3 independent custom electronic chains for data acquisition, exploiting the 3 different outputs (analog, digital, USB pre-processed) provided by the MPPCs modules. The electronic chain fed by the analog output is able to tag a single photon ToA (Time of Arrival) with a time resolution of 25 ns, while the remaining electronic chains can integrate the signal into time bins from 100 ms down to 20 μs. The absolute time is provided by a GPS unit with a time resolution of 25 ns at 50% of the rising edge of the 1PPS (1 Pulse Per Second) signal which is linked to the UTC (Universal Time Coordinated). Apart from the versatility with the remotely controlled on sky configuration of the MPPCs, the mounting of SiFAP2 at the NI allows for a permanent hosting of the instrument, readily available for observations. The new polarimetric mode will then offer other scientific opportunities that have not been explored so far in high-temporal resolution astronomy.
A high-energy photon polarimeter for astrophysics studies in the energy range from 10 to 800 MeV is considered. The proposed concept uses a stack of silicon microstrip detectors, where they play the roles of both a converter and a tracker. The purpose of this paper is to outline the parameters of such a polarimeter and to estimate the productivity of measurements. Our study, supported by a Monte Carlo simulation, shows that with a 1-year observation period the polarimeter will provide 6% accuracy of the polarization degree for photon energies above 100 MeV, which would be a significant advance relative to the currently explored energy range of a few MeV. The proposed polarimeter design could easily be adjusted to the specific photon energy range to maximize efficiency if needed.
The realization of low-cost instruments with high technical performance is a goal that deserves efforts in an epoch of fast
technological developments. Such instruments can be easily reproduced and therefore allow new research programs to be
opened in several observatories. We realized a fast optical photometer based on the SiPM (Silicon Photo Multiplier)
technology, using commercially available modules. Using low-cost components, we developed a custom electronic chain
to extract the signal produced by a commercial MPPC (Multi Pixel Photon Counter) module produced by Hamamatsu
Photonics to obtain sub-millisecond sampling of the light curve of astronomical sources (typically pulsars). We built a
compact mechanical interface to mount the MPPC at the focal plane of the TNG (Telescopio Nazionale Galileo), using
the space available for the slits of the LRS (Low Resolution Spectrograph). On February 2014 we observed the Crab
pulsar with the TNG with our prototype photometer, deriving its period and the shape of its light curve, in very good
agreement with the results obtained in the past with other much more expensive instruments. After the successful run at
the telescope we describe here the lessons learned and the ideas that burst to optimize this instrument and make it more