Scintillation Detectors and it’s Application

1. Scintillation Detectors and it’s Application • Particle interaction in matter • Scintillation mechanism • Inorganic scintillation detector • Organic scintillation detector • Light Sensor • Application • a) Nuclear, High energy, Astroparticle physics • b) Astrophysics • c) Bio-, Medical physics 2002년 6월 24일, KNU Summer school 김 홍주, 연세대학교

2. How to detect Quark to Cosmos Cosmos-connection-Quark

3. Detectors • use characteristic effects from interaction of particle with matter to detect, identify and/or measure properties of particle; has “transducer” to translate direct effect into observable/recordable (e.g. electrical) signal • example: our eye is a photon detector; (photons = light “quanta” = packets of light) • “seeing” is performing a photon scattering experiment: • light source provides photons • photons hit object of our interest -- some absorbed, some scattered, reflected • some of scattered/reflected photons make it into eye; focused onto retina; • photons detected by sensors in retina (photoreceptors -- rods and cones) • transduced into electrical signal (nerve pulse) • amplified when needed • transmitted to brain for processing and interpretation

4. Overview of Experiment computer simulation 01011101 Physics origin analysis & control detector signal processing data handling Physics interaction

5. Particle energy loss in matter PE CS PP electron(s) scintillator X rays gamma rays dE/dx loss charged particle dE/dx loss thermal neutrons nuclear reaction energetic neutrons dE/dx loss proton

7. Interactions of photons with water and lead

8. Gamma interaction

9. Particle Detection Principle

10. Scintillation detectors and sensors Scintillators Light sensors In radiation detection in solid state physics: luminescence fast < 1 ms: fluorescence slow > 1 ms: phosphorescence inorganic crystals organic plastics/liquid glass gas Photomultiplier Microchannel plate silicon diodes CCDs Avalanch photo diode hybrid photo diode

12. Scintillator • Light emitted from ionisation in transport material( dE/dx loss) a) I(t) = I0e-t/t ; t : decay time, several component possible b) t>ms -> count rate<< MHz, t ~ns -> count rate>> MHz, c) Wavelength of emission determine photosensor • Two main material types of scintillators a) Inorganic scintillator b) Organic scintillator

13. Scintillator charasteristics • Inorganic scintillators a) Result of crystalline structure b) Large band gap, insulators c) High light output but relatively slow (~msec) • d) Rather expensive, moderate size (~kg) • Organic scintillators a) Molecular property of hidrocarbons b) Moderate light output but fast (~ns) c) Cheap, large size (~ton) d) Liquid scintillator (LSC) Plastic scintillator (PSC) Crystal (ex:anthracene, stibulene)

14. Inorganic Scintillator • Ionisation excites electron conduction band de-excitation via photoemisson or radiationless transition • Large bandgap => slow process • Impurities add centres (traps) in band gap Increase transition rate Suitable doping can also increase light output ( ex: CsI(tl), CsI(Na) Hols trapped at activate site -> recombination with e- -> emits photon

15. Inorganic Scintillator examples

16. Organic Scintillator • Based on excited states of carbon atom (benzene ring : C=C bonds) Quasi-free electrons confined to molecule Complex vibration stats gives fine structure Range of singlet and triplet stats gives both long and short time structure => neutron and gamma separation capability • Chemical Mixing Solvent : Medium for absorbing the energy of nuclear recoil Energy transferred to 1st solute moleculs 1st Solute: highly efficient fluors (efficient scintillator) Very short wavelength 2nd Solute: Wavelength shifter to match with bi-alkali photo sensor

17. Organic solvent Band gap structure Energy transfer mechanism ns ms solute 1st solvent 2nd solvent

18. Organic scintillator Solvents • Solute a) Liquid Scintillator 1,2,4-Trimethylbenzene (Pseudocumene) p-,m-,o-Xylene, Toluene, Benzene, MN… a) Plastic Scintillator Polystyrene (Polyvinylbenzene, PS) Polyvinyltolunen (PVT) • 1st Solvent PPO, p-Terphenyl, PBD, Naphthalene.. • 2nd Solvent POPOP, M2-POPOP, bis-MSB…. • Standard Liquid Scintillator : PC + PPO(1.5-4g/l) +POPOP(10-50mg) 65% of anthrecene, safe, Pulse shape discrimination of n/gamma

19. ZEUS 실험

20. Scintillator light output readout Basic principles of operation Passage of charged particle generates light in scintillator Charged particle Light guide transmits light to photodetector Photomultiplier tube (PM or PMT) generates electric signal

21. Light transmission • Total reflection sin q> next/n, sin q> 1/n, next = air • Light guide • Optical grease (optical cement) • Light reflector Teflon, Al, white paint

22. PMT Photomultiplier Tube Light detection PMT reflector photo cathode  dynodes 2 N  Nel 1 3 n electron multiplication scintillator optical coupling ideal case: Nel =  N

23. Light Quantum efficiency of PMT photocathode

24. PMTS PMT types Venetian blind (old) Box-and-grid Focused linear structure Gains - 107 Circular grid

25. Detection principle

26. Detected Energy

27. Oscilloscope signal 660 keV g Typical signals from CsI(Tl) 10 keV g 660 keV a

28. CsI crystal R&D Co57 source Am alpha source

29. Neutron gamma separation with BC501A

30. Neutron gamma seperation with BC501A Partial Total

31. Energy spectrum in LSC with gamma, n Cs137 in LSC 2.24MeV neutron in LSC

32. Difference between Crystal & LSC Cs137 source(661 keV) to detector (GEANT4 simulation) CsI crystal BC501A LSC Quiz : Why different response?

33. Scintillator Application • High energy physics BELLE, BES, CDF, L3, Phenix, CMS, LC, Focus … Many more! • Astro-particle physics Neutrino ( LSND, Super-K, Kamland..), Underground( Darkmatter, neutrino, double beta), Ground array ( HE neutrino, UHE cosmic ray, HE gamma) • Nuclear Physics, Nuclear engineering. Neutron, Radioactive decay, heavy ion, radioactive beam. ; Power reactor monitoring • Astrophysics, Astronomy Balloon (ATIC, IMAX..), Satellite (GLAST, INTEGRAL..), Space station (AMS..) • Bio-science: Track radioisotopes in biology sample, Quantifying DNA and RNA • Medical science: PET, CT, Track radioisotopes in human body, medicine • Environmental science: Monitoring of radioactivity, nuclear waste, Radon • More :Safety inspection, Military …..

34. Identifying particles

35. What is happening in detector (Simulation) 1GeV gamma

36. ZEUS detector at HERA(ep)

37. The BELLE Detector (B physics) • Charged particle tracking and vertexing • SVD: 3 layer DSSD silicon microstrip • CDC: 50 layer drift chamber (50/50 He-C2H2) • sp = 0.46 % @ pt = 1.0 GeV/c • Particle identification • Hadron ID • CDC: dE/dx in central drift chamber • TOF: Time-of-flight system • ACC: Cherenkov light threshold counters • Electrons • ECL : E&M calorimeter E/p • CDC: dE/dx • Muons • KLM: RPCs in magnetic return yoke • Neutral particle detection • Photons: E&M calorimeter • 8800 CsI(tl) : 40ton • KL : direction in the KLM

38. AGASA ( UHE cosmic shower)

39. LSND (neutrino oscillation) Mineral Oil + LSC

40. R&D of mineral oil loading

41. KAMLAND (neutrino osc.)

42. DAMA experiment DAMA NaI(Tl) crystal ~100 kg Gran sasso underground lab. Low threshold ~ 2keV Low background ~ 1/kg/kev/day Annual modulation method Found a evidence of WIMP

43. KIMS experiment Detector & Shielding Design (Dark matter Search experiment) 100kg 5 ton

44. ATIC Ballon (HE cosmic ray)

45. GLAST Sattelate (HE gamma)

46. Radiation in Medical science Radioisotope imaging: Planar scintigraphy 2D position sensitive detector: Gamma camera + motion Multihole collimator crucial for image formation emission Radiopharmaceutical

47. PET Scans (Positron Emission Tomography) 3-D image Scintillating crystal detector and photomultiplier Cross Section

48. Radiation Technology Radioisotope imaging: Planar scintigraphy Phosphonate tagged with 99mTc, injected into the blood stream, is mainly transported to bones, producing a view of the skeletal system The method is e.g. used to determine whether or not cancer has metastized From: National Geographic 171/1(1987)2-41

49. Radiation in Aviation SecurityX-ray Application X-ray tube point source transmission Fan beam 1D position sensitive X-ray detector Conveyor 1D + motion  2D

50. Radiation in Aviation SecurityX-ray Application Advanced Multi X-ray Energy Method From: Heimann Systems, Wiesbaden, Germany