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By Archana SHARMA CERN Geneva Switzerland March 2009 Troisieme Cycle EPFL Lausanne, Switzerland

Gaseous Particle Detectors. By Archana SHARMA CERN Geneva Switzerland March 2009 Troisieme Cycle EPFL Lausanne, Switzerland. Archana.Sharma@cern.ch. Who am I ?. Education D.Sc Doctorat es Sciences particle physics: University of Geneva, Geneva, Switzerland, 1996

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By Archana SHARMA CERN Geneva Switzerland March 2009 Troisieme Cycle EPFL Lausanne, Switzerland

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  1. Gaseous Particle Detectors • By Archana SHARMA • CERN Geneva Switzerland • March 2009 • Troisieme Cycle • EPFL Lausanne, Switzerland

  2. Archana.Sharma@cern.ch Who am I ? Education D.ScDoctorates Sciences particle physics: University of Geneva, Geneva, Switzerland, 1996 Ph.D. Nuclear Physics:  University of Delhi, Delhi, India 1983-89 M.Sc Master’s Science: Nuclear Physics, Benares Hindu University BHU, India 1980-1982 B.Sc Bachelor’s Science:  Benares Hindu University, India: Physics, Chemistry, Math. 1976 to 1980  ISCE Senior Cambridge: St. Francis’ Convent High School, Jhansi, India 1976 EMBA Executive Master in Business Administration: International University Geneva, Switzerland 2001 Employment: July 2001-present (Staff Physicist, CERN) 1999-2001 (Research Associate, University of Maryland,  USA, deputed to CERN) 1997-1999 (Foreign Research Scientist, GSI, Darmstadt; Germany, deputed to CERN) 1995–1996 (Associate Haute Université Mulhouse, deputed to CERN) 1992–1994 (INFN, Borsista de Studio, INFN Art 36, deputed to CERN) 1989–1992 (Detector Development Division, CERN) 1987- 1989 Student, Detector Development Division, and completion of Ph.D.

  3. Chapter I 5th March 2009 • 1.1 Introduction • 1.2 Units and Definitions, Radiation Sources • 1.3 Interaction of Radiation with Matter • Chapter II 12th March 2009 • 2.1 General Characteristics of gas detectors, Electronics for HEP detectors • 2.2: Transport Properties • 2.3: Wire-based Detectors Tool

  4. Chapter III 19th March 2009 3.1 Resistive Plate Chambers for Tracking 3.2 Aging and Long Term Operation 3.3 Micro-pattern Detectors Chapter IV 26th March 2009 4.1 Measurements of Energy, Momentum, Time of Flight 4.2 Designing a HEP Experiment 4.3 Applications Outside Particle Physics Tool

  5. The World's biggest laboratory for particle physics research You are here FRANCE Who has not been to CERN ? Who has not heard of LHC ? SWITZERLAND

  6. Every day, around 10 000 scientistsfrom all over the world perform research at CERN Truly International Methodology Flags of CERN’s Member States 20 European Member States and around 60 additional countries collaborate in our scientific projects.

  7. Landmark of CERN The Globe of Science and Innovation The LHC is a discovery machine has the potential to change our view of the Universe, continuing a tradition of human curiosity that’s as old as mankind itself. The resulting innovation may have an unimaginable impact on our lives.

  8. HIGH • ENERGY • PARTICLES • ACCELERATORS • INTERACTIONS • DETECTORS What is a TeV ?

  9. The LHC is a proton proton collider 7 TeV + 7 TeV 1 TeV = 1 Tera electron volt = 1012 electron volt Rate 40 MHz The LHC will determine the Future course of High Energy Physics

  10. What is a TeV ? An electron volt is a measure of energy.  An electron volt is the kinetic energy gained by an electron passing through a potential difference of one volt.  A volt is not a measure of energy.   An electron volt is a measure of energy.  An electron volt is very tiny. Suppose it takes a mosquito 30 seconds to travel a human body 165 cm and suppose its mass is 0.1 grams . . . What is its energy in TeV?

  11. What is a TeV ? The Mosquito’s Kinetic Energy is E = ½ m v2 If it moves across 165 cms in 30 seconds Its velocity is 5.5 cm/sec So E=½ (0.1 gm)(5.5 cm/sec)2 = 1.51 ergs Convert ergs to eV by dividing by 1.602 x 10-12 E = 0.944 x 1012 eV or 0.944 TeV 1 joule is exactly 107 ergs 1 joule is approximately equal to: 6.2415 ×1018 eV (electronvolts)

  12. Introduction • HEP experiments study the interactions of particles by observing collisions of particles • Result: change in direction / energy / momentum of original particles • And production of new particles

  13. Detector elements p1 = -p2 1 2 p2 = 0 1 2 Experiments • These interactions are produced in • WHAT : measure as many as possible of the resulting particles from the interaction • HOW: put detector “around” the interaction point

  14. Interaction of particles in detector components Fixed Target Collider 1 Tracking Detectors: Pixel, Silicon Strip, Gas Microstrip, Drift Cells, Tubes, Drift Chambers 2 Electromagnetic Calorimeters: Plastic Scintillator / Lead Sandwich, Liquid Argon, Crystals 3 Hadronic Calorimeters: Plastic Scintillator / Iron or Copper Sandwich, Liquid Argon 4 Muon Detectors: Drift - Tubes, Cathode Strip Chambers, Resistive Plate Chambers

  15. See http://pdg.lbl.gov/atlas/index.html TOTALGaseous Detectors In ATLAS~ 10,000 m2 ATLAS

  16. See http://cmsinfo.cern.ch/Welcome.html/ TOTALGaseous Detectors In CMS~ 10,000 m2

  17. Just in case you wonder why? Knownparticles thatdisappeared after the Big Bang HighlyExpectedParticles Methodology E=mc2 Hypothetical Or totallyunsuspected ? SUSY

  18. A Higgs Event in CMS Methodology 2 muons 2 electrons

  19. Tools of the trade 1. Accelerators : powerful machines capable of accelerating particles up to extremely high energies and bringing them into collision with other particles. 2. Detectors : gigantic instruments recording the particles spraying out from the collisions. 3. Computers : collecting, stocking, distributing and analysing the enormous amounts of data produced by the detectors. 4. People : Only a collaboration of thousands of scientists, engineers, technicians and support staff can design, build and operate these amazing machines

  20. SIZE OF THE DETECTORS

  21. The ideal detector With an “ideal” detector, we can reconstruct the interaction, i.e. obtain all possible information on it. This is then compared to theoretical predictions and ultimately leads to a better understanding of the interaction and properties of particles For all particles produced, the “ideal detector” measures energy, momentum, type by : mass, charge, life time, spin, decays

  22. Negative charge Magnetic field, pointing out of the plane Positive charge Measure and derive • The mass, velocity, energy and charge (sign) • from ‘tracking’ curvature in a magnetic field • The lifetimet • from flight path before decay t

  23. Different type of particles to be detected • Charged particles • e-, e+, p (protons), p, K (mesons), m (muons) • Neutral particles • g (photons), n (neutrons), K0 (mesons), • n (neutrinos, very difficult) Different particle types interact differently with matter (detector) (for example, photons do not interact with a magnetic field) Need different types of detectors to measure different types of particles

  24. e- p p p g e- p Principles of detection • Interaction of a particle with detector Sensitive Material Measureable Signal • Ionization • Excitation • Particle trajectory is changed due to • Bending in a magnetic field, energy loss • Scattering, change of direction, absorption

  25. Ionization signals by using • Gaseous detectors: • MWPC and its derivatives • (Multi-Wire Proportional Chambers) • Drift Chambers (DCs) • TPC (Time Projection Chamber)

  26. Key Points: Lecture 1-1 • Requirements for response from (gaseous) detectors • Fast • Light • Hermetic • Radiation Tolerant

  27. Exercise: Lecture 1-1 • Make a list of five - light yet strong materials that can be used as mechanical support and can withstand high radiation: • Insulators • Conductors • Sheets

  28. Chapter I 5th March 2009 • 1.1 Introduction • 1.2 Units and Definitions, Radiation Sources • 1.3 Interaction of Radiation with Matter • Chapter II 12th March 2009 • 2.1 General Characteristics of gas detectors, Electronics for HEP detectors • 2.2: Transport Properties • 2.3: Wire-based Detectors Tool

  29. Gaseous Particle Detectors: • By Archana SHARMA • CERN Geneva Switzerland • March 2009 • Troisieme Cycle • EPFL Lausanne, Switzerland

  30. Chapter I 5th March 2009 • 1.1 Introduction • 1.2 Units and Definitions, Radiation Sources • 1.3 Interaction of Radiation with Matter • Chapter II 12th March 2009 • 2.1 General Characteristics of gas detectors, Electronics for HEP detectors • 2.2: Transport Properties • 2.3: Wire-based Detectors Tool

  31. Different types of tools and equipment are neededto observe different sizesof objects Only particle accelerators and detectorscan explore the tiniestobjects in the Universe Methodology

  32. Ionizing Radiation • One Gray is the absorption of one joule of energy, in the form of ionizing radiation, by one kilogram of matter • For X-rays and gamma rays, these are the same units as the Sievert (Sv).

  33. Types of Radiation Neutral Particles Charged Particles Fast electrons Heavy charged particles Electro-magnetic Radiation Neutrons

  34. Charged Particle Radiation Fast Electrons b-particles emitted in nuclear decay energetic electrons produced by any process Heavy Charged Particles Energetic ions: alpha particles, protons Fission products Products of nuclear reactions

  35. Neutral Particles Electromagnetic Radiation X-rays emitted by re-arrangement of electron shells in atoms Gamma rays from transitions in the nucleus Neutrons Generated in various nuclear processes Often subdivided into slow and fast neutron sources

  36. Radiation Properties Energy range spans six orders of magnitude: from 10 eV to 20 MeV Radiations differ in hardness: ability to penetrate thickness of material. Soft: alpha particles or low-energy X-rays Medium: Beta particles Hard: Gamma rays and neutrons Soft radiations penetrate only small material thickness: Sources need to consist of very thin layers to prevent self-absorption.

  37. Units of Radioactivity dN dt = −λN # Radioactive Nuclei Activity Decay constant Curie The Curie (Ci) is the historical unit: activity of 1 gram of pure 226Ra Bequerel The Bequerel (Bq) is the SI unit: one disintegration per second Activity measures the source disintegration ≠ emission rate of radiation

  38. How many Bequerels make a Curie?

  39. Specific Activity Specific activity is the activity per unit mass of the source Avogadro’s Number Radioisotope decay constant (ln2/half-life) For mixed samples the specific activity is more complex: self-absorption or chemical combination with other stable nuclei Sample molecular weight

  40. Energy Energy is traditionally measured in electron volts: Kinetic energy gained by an electron by its acceleration through a potential difference of 1 volt. Remember an eV is very tiny! Typically measure radiation in keV, MeV or GeV Energy of a photon is related to the radiation frequency and hence the wavelength

  41. Other Units encountered when working with gaseous detectors Ohm’s Law and associated units Electron charge and its multiples Equivalent electronic current Flux of radiation particles / unit area of detector Or unit length of wire

  42. 1. Fast Electron Sources Beta Decay Internal Conversion Auger Electrons

  43. Beta Decay The name is historical: beta rays are really electrons and positrons e Z protons A neutrons + protons p n p n p n p n p n p n p n n (Z + 1) protons (A) neutrons + protons p n p n p n p n p p n n p n What really happens n n p Two flavors of Beta Decay:β+: proton to neutron β- : neutron to proton e 

  44. Beta Decay Each beta decay is characterized by a fixed decay energy (Q-value) 36Cl (3.08 x 105 y) - Beta Particle Energy Spectrum 36Ar Shared between beta particle and the invisible neutrino Q: endpoint energy

  45. Internal Conversion Energy transferred to one of the orbital electrons Source of monoenergetic electrons range high keV-MeV e Excited nuclear state

  46. Auger Electrons Analogous to internal conversion but excitation energy originates in the atom not the nucleus e e e e e e e A process (say electron capture) leaves a vacancy in a shell e e Usually the vacancy is filled by one of the outer electrons accompanied by emission of an X-ray photon e e e e e e e Sometimes the atom’s excitation energy is transferred directly to an outer electron which is ejected e e

  47. 2. Heavy Charged Particle Sources Alpha Decay Spontaneous Fission

  48. Alpha Decay • particle He Nucleus Z protons A neutrons + protons p n p n - p n p n p n p n p n p n p n n (Z -2) protons (A - 2) neutrons + protons p n p n p n p n p n p n p n n + -  Pu 238: powerful α emitter

  49. Spontaneous Fission All heavy nuclei are unstable against spontaneous fission into lighter fragments but this is inhibited by the large potential barrier from the distortion of the nucleus from its spherical state 252Cf fission fragments Mass distribution Only a significant process from some transuranic isotopes (large mass number) Fission fragments are medium-weight positive ions. Often asymmetric: clustered into light and heavy groups Kinetic energy

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