OSCAR

OSCAR (Observation System using Cosmic Ray Muon Flux for Underground Surveillance)

Monitoring natural events such as earthquakes, volcanic eruptions and landslides has immense importance, both scientific and social. When produced in the vicinity of populated areas, those events may affect traffic safety on inland transportation or of the mining activities by altering the structure and stability of access tunnels or galleries. If those effects are not spotted in time, this could lead to tragedy. These events illustrate the major risks which civilians and mining workers are exposed to when cavities above underground structures are not discovered and properly secured. If spotted in time, measures can be taken to avoid future collapse risk. Therefore, imaging the inner part of large geological targets is important and should be integrated in the safety procedures for mining industry or in the maintenance of access tunnels.

The main goal of the “Observation System using Cosmic Ray Muon Flux for Underground Surveillance” (OSCAR) project is to improve the security of underground civilian and industrial infrastructures, by starting the development of a new, innovative detection system that can be used to identify potentially dangerous conditions using a non-invasive, totally safe method. A validated small scale model will be delivered at the end of the project, accompanied with a patent proposal.
The method proposed uses information provided by a device placed in the underground that measures directional cosmic muon flux and identifies anomalies produced by irregularities in the geological layers above. Correlated with accurate simulations based on the known configuration of the area scanned, the data provided by the detection system will provide the location and dimensions of undiscovered cavities.

 

The Research Team

Dr. Denis Stanca – Project Leader

Dr. Habil. Bogdan Mitrica – Senior Researcher

Dr. Romul-Mircea Margineanu – Senior Researcher

Toma Stefan Mosu – Ph.D Student

Dr. Dana-Elena Dumitriu – Senior Researcher

Dr. Iliana-Magdalena Brancus – Senior Researcher

Dr. Alexandra Saftoiu – Senior Researcher

Alexandru Gherghel-Lascu – Ph.D. Student

Alexandru Balaceanu – Ph.D. Student

Mihai Niculescu-Oglinzanu – Ph.D. Student

Andreea Munteanu – Tehnician

Gherghina Stan – Tehnician

 

Technical details

The method of project implementation is comprised of two main stages, each with its related activities:

Stage 1. Simulation of the detector response

Activity 1.1: Simulation of detector response and efficiency

 

 

Stage 2. Laboratory tests and development of the experimental configuration, testing and validation of the device

Activity 2.1. Development and testing of the electronics and DAQ

Activity 2.2. Design of the detection system

Activity 2.3. Testing and validation of the device


We finished Stage 1 of the project:

[Romana]

Activitatea intreprinsa in prima etapa a proiectului a umarit trei directii:

A fost simulat raspunsul a doua configuratii ale detectorului la interactia cu miuonii pozitivi si negativi. Pentru asta, fotonii rezultati in urma interactiei au fost simulati in volumul barelor de plastic scintilator. Colectarea acestora prin fibra optica a fost analizata, iar fotonii absorbiti de SiPM au fost numarati. Pentru a observa cum este afectata eficienta de detectie a detectorului cu variatia latimii barelor scintilatoare, doua latimi diferite au fost folosite: de 2.5 cm si 4 cm.
Urmatorul pas a fost simularea a doua cavitati sferice de cu diametrele de 0.6 m respectiv 1m si materiale diferite deasupra detectorului pentru a testa cum este influentat fluxul miuonilor incidenti de acestea. Obiectele au fost plasate deasupra detectorilor pentru a vedea cum este afectata reconstructia de diametrul obiectului observat.
Un cod de reconstructie a fost implementat avand la baza pachetul de analiza ROOT. Acesta construieste imaginea generata de detector in urma informatiilor generate de simulari, tinand cont si de parametrii de intrare, cum ar fi distanta la care se afla obiectul, dimensiunile acestuia,etc. Acest cod a fost dezvoltat astfel incat sa poata fi folosit atat pentru interpretarea datelor provenite din simulari cat si pentru analiza rezultatelor experimentale. Acest cod urmeaza sa fie imbunatit prin o mai buna reconstructie a traiectoriei miuonilor incidenti pentru formarea unor imagini de rezolutie mai buna.

 

[English]

The activity for the first stage of the project was organized following 3 directions:

It was simulated the response of two configurations of the detector for the interaction with positive and negative muons. Regarding this, the resulted photons from the interaction were simulated in the plastic scintillator bars volume. It was analyzed their collection through the optic fiber, while the photons absorbed by the SiPM were counted. In order to observe how the detection efficiency is affected by the width variation of the scintillator bars, two different widths were used: 2.5 cm and 4 cm. The next step was the simulation of two spherical cavities with the diameter of 0.6 m and 1 m respectively and with different materials over the detector, in order to test how the incident muon flux is influenced by these. The objects were placed on top of the detector to see how the reconstruction is affected by the observed object diameter.

A reconstruction code was implemented, based on the ROOT analysis package. It builds the detector generated image by following the information from the simulations, in the same time taking into account also the entry parameters, like object distance, its dimensions etc. This code was developed in such way that it can be used for the simulation-based interpreted data, but also for the experimental results analysis. This code will be further improved in order to have a better incident muon trajectory reconstructions and also to have a better resolution.

 

 

 

 

Currently, we just finished phase 2 of the project.

 

 

Stage 2 (final stage) of the project [Romana]:

Activitatea intreprinsa a umarit trei directii:
In prima instanta a fost proiectat sistemul de detectie. Tinand cont de cerintele tehnice
necesare unui asemenea dispozitiv in vederea detectatii de cavitati in spatii subterane, cum ar fi
consum scazut, componente ieftine, greutate scazuta, dar si de rezultatele obtinute in urma
simularilor Monte Carlo dezvoltate in etapa 1 a proiectului, s-a decis ca detectorul final sa fie
alcatuit din 2 plane de detectie a cate 4 straturi, fiecare strat fiind compus din 40 de bare de
plastic scintilator (100×2.5×1 cm) izolate optic, fiecare avand insertie cu fibra optica/schimbator
de unda. Cele 40 de canale ale fiecarui strat de detectie vor fi citite independent de cate o
fotodioda de tip SiPM (SiliconPhotomultiplier). Cele 4 straturi for fi grupate 2 cate 2, cu
directiile date de lungimile barelor asezate perpendicular, creandu-se astfel 2 plane de detectie ce
fac posibila reconstructia traiectoriei particulei incidente in x-y-z.
Dupa care a fost testate si optimizata electronica de achizitie, mai exact au fost testate
dispozitivele de tip SiPM folosite, in acest sens fiind dezvoltata o electronica de tip front end
specifica fiecarui dispozitiv testat. Au fost dezvoltate doua tipuri de semnale, unul rapid si unul
lent, din analiza efectuata cu osciloscopul hotarandu-se ca pentru configuratia finala a
detectorului sa se foloseasca exclusiv semnalul rapid.
In final, sistemul de detectie a fost testat prin asamblarea unui banc de test alcatuit din 4
bare de plastic scintillator, doua cate doua suprapuse, formand astfel 2 straturi avand suprafata
activa de detectie per strat de 500 cm2. Cele doua fibre folosite pentru culegerea semnalului
luminous de la stratul de sus au fost directionate catre o fotodioda iar cele de jos directionate
catre o alta. Facand coincidenta intre cele 2 straturi, s-a pus in evidenta faptul ca particula ce
interactioneaza cu ambele suprafetele active este miuon. Castigul in semnal a foost masurat,
concluzionandu-se ca sistemul de achizitie final poate raspunde cu acuratete la fluxul de fotoni
dat de un singur canal. Pentru prelucrarea semnalelor date de electronica front end si executarea
coincidentelor intre cele 2 straturi intr-o fereastra de timp de 30nS, un modulul Saturn – Spartan
6 FPGA Development Board with DDR SDRAM a fost programat.
Metoda a fost validata prin masurarea fluxului de miuoni in laborator si compararea acestuia cu
rezultatele obtinute in urma simularilor, cele doua fiind compatibile.

De asemenea, au fost identificate cateva posibile locatii subterane pentru testarea prototipului si
au fost caracterizate din punctul de vedere al concentratiei de Rn, in vederea asigurarii sigurantei
personalului implicat in masuratorile pe termen lung ale fluxului directional de miuoni.

 

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