Improvement of the MAGIC LIDAR data analysis
Abstract:
The MAGIC Cherenkov telescopes detect photons from the extensive air showers created by high energy particles and gamma rays at the upper atmosphere. The Cherenkov radiation emitted in the extensive air showers is scattered by aerosols and for improving energy estimations in MAGIC an aerosol profile is needed. The LIDAR system for the MAGIC telescope provides a tool to obtain the aerosol transmission profile of the atmosphere. We improve the method that is used to retrieve the transmission profile focusing on two aspects of the LIDAR system. After shooting the laser at the sky and receiving the backscattered light, first we focus on the photon counting algorithm which returns the spatial profile of the backscattered light. Besides the implemented single photon counting and integration for the short range where an overlap of single photons occurs, we also take into account the different errors that could emerge within this process, like the variable pedestal for the single photon counting or the charge integration for each type of single photon signal. We estimate the contribution of each error. Secondly, we focus on the data analysis and we improve it with the GDAS atmospheric pro les. We improve the algorithm at long ranges taking into account the signal statistical deviation and using a different binning for the data points. We find that the GDAS profile fits correctly the data for near and long ranges. However, the retrieved value of the aerosol transmission depends heavily on the parameter which defines the type of aerosol (LIDAR Ratio) used in the computation, and so can only be used in certain assumptions. Finally we evaluate the goodness of the method and we comment some further improvements that could be applied.
Keywords:
MAGIC LIDAR