1. 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

2. 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

3. Extensive Air Shower (EAS)

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

5. 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

6. 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
p/s
18.5%
3D representation for the first set of data (no lead)
3D representation for the second set of data (with lead)

7. 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
p/s
L1 and L2 and L3 and L4 and L5 and L6
21 p/s
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

8. 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 ).

9. 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.

10. Thank You!