Particle accelerators. Dr. Alessandro Cianchi

Transcription

1 Particle accelerators Dr. Alessandro Cianchi

2 Particle accelerators: instructions 48 hrs lectures (Wednesday 6, Friday 6 9:00) All the documentation is available via web in Acceleratori-Di-Particelle Point of view: Physics We will face all the fundamental principles of particle accelerators But we ll focus also on the ingoing activities at the next door

3 LNF: the next door A tour of the is included in the course (May 26 th 14:30) Staff = 350 Associates = 181 Visitors = 463 TOTAL 994

4 Final test Oral examination Any problem? People interested in update please send me an to make an address book

5 Basic Syllabus I Introduction to the importance of the accelerators The history line: Electrostatic accelerators Electrodynamics accelerators: Cyclotron Betatron Microtron Synchrotron Colliders Linear optics in the accelerators Equation of motion Transverse dynamics Betatron oscillation Emittance: definition, meaning, measurement The beam envelope equation Resonance and instabilities

6 Basic Syllabus II Longitudinal dynamics Phase stability Equation of motion The Synchrotron radiation The physics of Synchrotron radiation Transverse and longitudinal dynamics with radiation Light sources FEL Accelerating structures RF Cavity Principal parameter The future: the plasma acceleration

7 Background requested Basic Electromagnetism, Maxwell equations Did you like Electromagnetism? Good! Did you experience problems? It s time to make peace! Special relativity

8 Melting pot

9 What is an accelerator? Source Accelerator Target T i T f It is a device that transfers energy to charged particle by electromagnetic or electrostatic fields. The particles are injected at initial energy of T i and they arrive to final energy T f.

10 What are accelerators used for? Understanding the fundamental building blocks of nature and the forces that act upon them (nuclear and particle physics)

11 Investigate the matter Understanding the structure and dynamics of materials and their properties (physics, chemistry, biology, medicine) via neutron spallation source o Synchrotron and FEL light sources

12 X radiation with fs pulse length Investigation of the molecular dynamics, chemical reaction time resolved. Wide range of applications from physics to pharmacy

13 Sorgenti Compton inverso per la produzione di gamma

14 Medical application of ions Medical treatment of tumors and cancers, using the properties of the Bragg peak

15 Big machines for medical treatment CNAO is the first center in Italy for tumor treatment using ions produced in a particle accelerator

16 Production of medical isotopes Small size machine devoted to the production of short half-life radioactive isotopes

17 And also Sterilization Ion Implantation to modify the surface of materials Industrial applications can be Transmutation of nuclear waste The everyone s accelerator is

18 Worldwide inventory of accelerators Category Number Ion implanters and surface modification 7000 Radiotherapy 5000 Accelerators in industry 1500 Accelerators in non-nuclear research 1000 Medical isotopes production 200 Nuclear and particle physics research 110 Synchrotron radiation source 70 Hadron therapy 20 U. Amaldi Europhysics News, June 31, 2000

19 Units 1 ev: energy of a particle di charge e, initially at rest, after the acceleration by a potential of 1 V 1 ev= J 1 kev = 10 3 ev ; 1 MeV = 10 6 ev 1 GeV = 10 9 ev; 1 TeV = ev Energy of a proton in the LHC: 7 TeV = 1.12 x 10-6 J the same energy of a body of mass = 1 mg moving at speed = 1.5 m /s (a mosquito!)

20 Energy and momentum Protons are accelerated to a kinetic energy of 200 MeV Calculate their total energy, their momentum and their velocity in our units

21 The needs of high energy particles An accelerator is nothing else than a microscopy h p Wavelength of the particles used by Rutherford (1911) in the discovery of the atomic nucleus: h m v J s 27 ( kg ) ( m s -1 ) m particle mass 0.05 c ~ resolving power of Rutherford s experiment

22 Probe for micro cosmos Resolving power Optical microscopes Visible Light ~ m Electron microscopes Low energy electron ~ m Radioactive sources particles ~ m Accelerators High energy electron, protons ~ m Another key point is the production of new particles at even higher energy

23 Time machine

24 Energy Stationary target Colliding beam

25 Problem At LHC there are two colliding beams of 7 TeV If we consider a fixed target experiment how much must be the energy of the moving beam to achieve the same energy in the center of mass?

26 Magnetic and electric rigidity B orthogonal to the particle trajectory y x

27 Only magnetic field to bend the beam Electron 1 GeV moving on y=0, B=1 T Calculate the magnetic rigidity, the radius of curvature and the electric field needed to have the same radius of curvature

28 Energy scale Starting from the 1930s, the energy has increased-- by about a factor of 10 every six to eight years this spectacular achievement has resulted from a succession of technologies rather than from construction of bigger and better machines of a given type. W. K. H. Panofsky, 1997.

29 Accelerator history

30 Particle Accelerators The Electrostatic Accelerators

31 References K. Wille The Physics of Particle Accelerator, Oxford University press pag 1-29 H. Wiedeman Particle accelerator physics volume 1, chapter 3 Just for your knowledge: A. Sessler, E. Wilson, ENGINES OF DISCOVERY, World Scientific

32 Principle of operation

33 Current in electrostatic accelerators Ohmic: proportional to voltage Residual ion current: saturates rapidly (also beam) Corona: negligible for small voltages Current grows exponentially for high voltages causing spark discharge and voltage breakdown

34 Paschen s law When the pressure increases, the collision probability increases, but the path between two collisions decreases, so also the energy transferred to an electron is decreased. When the pressure us very low, the path between two collision is quite large, but the probability of a collision is relatively smaller.