Insight of 3D imaging using SiRO Horia Hulubei National Institute for Physics and Nuclear Engineering, Bucharest-Magurele, Romania Insight of 3D imaging using SiRO M. Niculescu-Oglinzanu DFN - Astroparticle Physics Group

The SiRO (Silicone Read-Out) Detector The SiRO detector is designed to perform cosmic muons flux measurements and can reconstruct each event incident trajectory. The detector is based on plastic scintillators, optical fibers (wavelength shifters) and readout by SiPM(MPPC-Multi Pixel Photon counter) devices. Is consisting of a stack of 6 active modules, grouped in 3 layers for determining the muon trajectories through 3 planes. One module has 24 plastic scintillators stripes with 2 fiber mounted on each stripe, read by 24 MPPC devices. Active surface is 1m x 1m . The schematic view of the Muon Detector

Extensive Air Shower (EAS)

The SiRO (Silicone Read-Out) Detector The final configuration of the detector

The positioning of lead bricks on detector Testing detector sensitivity in 3D imaging for tomographic reconstruction Two sets of measurements were taken at ground level, in two consecutive days with the same weather conditions, each set with 20 hours of continuous data acquisition. In the first day, measurements were done with the detector in final setup and in the next day, in the middle of each layer were installed a group of 8 lead bricks (each brick with 10x10x5 cm) to act as a shield for incident muons. To make analysis easy, for trajectory reconstruction, event validation and 3D imaging the whole detection surfaces will be split in 576x3 virtual pixels. The positioning of lead bricks on detector

Results of the measurements First Set – no lead Muon Flux (pulses/second) Second Set – lead installed Flux reduction with lead Experimental data 21.4 p/s 18.1 p/s 15.42% Theoretical data 29 p/s 23.635 p/s 18.5% 3D representation for the first set of data (no lead) 3D representation for the second set of data (with lead)

Measurements performed underground Coincidence Ground level Muon flux (pulses/second) Underground level Muon flux (pulses/second) L1 and L2 and L3 and L4 58.5 p/s 0.0478 p/s L1 and L2 and L3 and L4 and L5 and L6 21 p/s 0.0384 p/s Flux reduction between coincidence of 4 to 6 layers 64% 19.6% Further analysing acquired data we observe that roughly 2% of recorded events are like in the figure and we can conclude that a local secondary muon shower is induced from a muon passing the physical layers of the detector. Because of the high sensitivity and spatial accuracy of SiRO we can study and determine with precision information about such events (direction of incident particle and even can estimate the energy of the particle). secondary induced muon shower

Future Analysis, tomographic reconstruction Tomographic reconstruction is a type of multidimensional inverse problem where the challenge is to yield an estimate of a specific system from a finite number of projections. The mathematical basis for tomographic imaging was laid down by Johann Radon (Radon transform - 1917).

Conclusions After the results of the last tests and partial analysis of measured data we can conclude that SiRO detector, with an unique design and a considerable practical flexibility, can meet the requirements set in the beginning: * Measurements of the directional variation of the muon flux at ground level, or in the underground (low radiation background). * Tomographic reconstruction for detecting unknown cavities in old mining sites * Explore variations in the rock density and composition above the observation level for non-invasive geological studies.

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