Soken-dai Core Curriculum, Fall, 2020 Introduction to Accelerators II - Week 1 General Introduction to Particle Accelerator Systems 2020/10/15 Nobukazu Toge (KEK) [email protected] 1 What this Lecture is for • This lecture: – Gives you a cursory overview of various accelerator systems, their subsystems and components via a short walk-through seminar in the class, – Helps you (hopefully) acquire some sense of how a real-life accelerator is like. 2 Texbooks • Introductory textbooks which might benefit you are as follows: – S.Y.Lee: Accelerator Physics, World Scientific, 2004. Many of its chapters are available for viewing online: http://bit.ly/93zVw6 – D.Edwards and M.Syphers: AIP Conf. Proc. 184, 1989, American Institute of Physics – H.Wiedemann: Particle Accelerator Physics, Springer Verlag, 1993. – OHO Lecture Series (although they are mostly in Japanese). – A.Chao and M.Tigner: Handbook of Accelerator Physics and Engineering, World Scientific, 1999. 3 Particle Accelerator • Particle beamsSituation where a group of electrically charged (or neutral) particles are moving at mostly the same velocity (momentum) in mostly the same direction. • Particle accelerators: Set of instruments which creates particle beams artificially in a controlled manner. • Use of particle beams: Particle beams may be used as they are, or may be used to create other secondary beams for - – Experimental research in particle physics, nuclear sciences, materials and life sciences, and/or – Medical and industrial application with their capacity of penetrating, imaging and processing materials 4 Particle Accelerator • Use of particle beams: Particle beams may be used as they are, or may be used to create other secondary beams for - – Experimental research in particle physics, nuclear sciences, materials and life sciences, and/or – Medical and industrial application with their capacity of penetrating, imaging and processing materials – Human control ! Allows experiments under controlled conditions (Exemplary experimental sciences, with benefits and limitations. – How many Nobel prizes where experiments with particle accelerators played decisive roles? Ans11 cases out of 139: 21 winners out of 217, as of Fall, 2020 • Particle accelerators are a subject of research and development on their own – New regimes of particle energies or particle numbers can be realized only by the efforts of accelerator builders – you have to do it yourseves. – It of course, means collaborative work with other fields and industries is essential – you have to work with other people. 5 Real Basics • Energy / Momentum 1 – Non-relativistic: E = mv2 ; p = mv 2 – Relativistic: E = m2c4 + p2c2 = mc2g ; p = mcgb b = v / c; g =1/ 1- b 2 – Speed of light: c = 2.9979 108 m/s ! ! ! ! – Forces on charged particles: F = q(E + v ´ B) – And when the B is UP, the electrons go to the LEFT. – Unit of energy: eV (electron-volt) keV (103), MeV (106), GeV (109), TeV (1012) Unit of momentum: eV/c (electron-volt/c) 6 Particle Acceleration • It means to increase the kinetic energy of a particle. • Charged particle attains an additional kinetic energy as it passes through a space with electric field • Electron Volt – 1eV = Kinetic energy attained across a potential gap of 1V Electric charge of an electron = 1.602 10^-19 C 1 eV = 1.602 10^-19 J – Velocity of an electron with kinetic energy 1eV ? E = mv^2/2, where an electron mass m = 9.1 10^-31 kg , 1 eV = 1.602 10^-19 = 9.1 10^-31 v^2 / 2 v = 5.9 10^5 m/s v/c = 5.9 10^5 / 2.9979 10^8 = 0.002 Velocify of a proton with kinetic energy 1000 eV ? 7 Mainly electrons and positrons Belle-II Detector SuperKEKB Photon Factory Slow e+ facility e-/e+ Linac 8 Linear accelerator for e- and e+ KEK Tsukuba 9 Linear accelerator for e- and e+ KEK Tsukuba 10 Accelerator System - SuperKEKB Straight Section http://www-acc.kek.jp/KEKB/index.html Detector Facility for HEP Experiment Bending Section Accelerator Cavities Positron Damping Ring Linear Accelerator (Linac) Positron Source Electron Source Linear Accelerator (Linac) Counter-travelling e- (7GeV; Blue) and e+ (4GeV; Red) beams are made to collide repeatedly at a single collision point – Goal: Max the particle collision rate. 11 Accelerator System - KEKB 12 First hadronic event that was observed at Belle-II (April 26, 2018) Belle-II detector at SuperKEKB 13 Accelerator System – Light Source Rings http://pfwww.kek.jp/outline/pf/pf1.html PF Ring (2.5 – 3GeV) AR Ring (6 – 6.5 GeV) Store only the electrons to produce SR light (X-rays) for experiments. Goal: Max support user experiments with SR of desired characteristics. Hard X-ray stations Soft X-ray stations 14 Accelerator System – Light Source Rings Exp hall at the KEK Photon Factory 15 Accelerator System – Energy Recovery Linac (ERL) http://pfwww.kek.jp/ERLoffice/ ERL is similar to light source rings in that it utilizes light emission off electron beam as it goes through undulator Beam Dump magnets. Differences (and advantages), however, include: + one-time use of beam, i.e like linear Accelerator Cavities accelerator (SuperconDucting) + opportunities for very bright, very short light pulses + energy recovery UnDulator magnets as light source Injector “CompactERL” prototype E ~ 35-245 MeV; I ~ 10 mA; ge ~ 0.1 – 1 mm ; st ~ 100fs rms Proposal for “Real” ERL Electron source E ~ 5GeV; I ~ 10 - 100mA ; ge ~ 10 – 100 pm; st < 100fs rms 16 Accelerators at KEK Tsukuba Facility Primary Beam Use Application SuperKEKB Electron, Collision High energy physics Positron PF Electron Synchrotron radiation Material + life sciences PF/AR Electron Synchrotron radiation Electron, Positron Electron, Delivery to SuperKEKB, PF, PF/AR Injector Positron CompactERL Electron Synchrotron radiation R&D of new SR source ATF Electron Beam studies R&D of Beam handling for ILC STF Electron SRF cavity R&D R&D for SRF beam acceleration 17 Accelerator System – J-Parc http://www.j-parc.jp 3GeV Synchrotron 50GeV Synchrotron – 15µA (0.4 ! 3GeV; 333µA 1MW, 25Hz) Hadron Exp Mat / Life-science exp Accelerator-driven Transmutation Fac. Linac (0.4-0.6GeV; Neutrino Exp Fac. 15µA, 500µs, 50Hz) To Super-Kamiokande High-power proton accelerator to concurrently support numerous user experiments spanning over material / life / nuclear and particle. Goal: Reliable delivery of high-current proton beams. 18 Accelerator System – J-Parc 19 T2K Experiment (T2K = Tokai ! Kamioka) 20 Accelerators at J-PARCKEK + JAEA of Tokai Facility Primary beam Beam usage Application Proton linac Proton delivery to RCS, MR RCS Proton Delivery to MLF to Material and life produce neutrons sciences and muons Delivery to MR MR Proton Delivery to hadron High energy physics facility (HF) to and nuclear physics produce mesons and muobns Proton Delivery to neutrino High energy physics production beamline ! SuperKamiokande 21 Accelerator System – Linear Collider https://www2.kek.jp/ilc/ja/ 250GeV e- on 250GeV e+; Rep rate = 5Hz Accelerate electron beam and positron beam with two linear accelerators, and have them collide head-on at the beam collision point at the center for experiments in HEP. Goal: Max the energy reach, max the beam interaction rate. Check the movie at http://bit.ly/dutCx0 for visual effects. 22 Basics (1) • Energy and momentum of material particles: – Non-relativistic case, where velocity v is much smaller than speed of light c - 1 E = mv2 ; p = mv 2 – Relativistic case: E = m2c4 + p2c2 = mc2g = mc2 / 1- b 2 p = mcgb = mcb / 1- b 2 Where, b = v / c; g =1/ 1- b 2 – Speed of light: c = 2.9979 108 m/s 23 Basics (2) • Simplified special relativity ! # ! = , # = " #$%! $ = %&&# Knowing 1 ! = 1 − #& %! If ) ≪ & ,γ ~ 1 + . So, & !& 1 $~%&& 1 + = %&& + %)& 2 2 24 Basics (3) • In our field the particle masses are measured in the unit of energy Rest mass energy = %&& For electrons: %&& = 9.109 2 10$'# (2.9979 2 10()& = 8.19 2 10$#) J 1eV = 1.602 10-19 J Rest mass energy of an electron is %&& = 8.19 2 10$#)/1.602 2 10$#* = 5.11 2 10) = 511 keV Velocity of an 8GeV electron? γ = 8 2 10+/511 2 10' = 1.5656 2 10) 1 1 ! = 1 − ~1 − = 1 − 2 2 10$+ #& 2#& 25 Basics (4) If the B field is “up” an electron goes LEFT Equation of circular motion. r gives the radius of curvature of the trajectory. 26 Creating a particle beam? • Electrons and protons are abundant in materials. Yet they are usually in bound states. • To create electron/proton beams means – To unbound them, and – To bring them into the state suitable for handling with particle accelerators. • Particles which don’t exist naturally (for instance, positrons) need to be artificially created. 27 Electron Source (Example) Thermionic Gun: Thermal electrons are extracted from a cathode which is set at a negative HV and is being heated. Electrons 28 29 Electron source2 30 RF electron gun for the electron/positron linac at KEK Tsukuba. Positron source Bring high energy electron or photon beams on high- intensity target (tungsten etc) and let them produce electromagnetic showers. Pick up positrons produced in e+e- pair creation (threshold energy = 2 x 511keV) 31 Flux concentrator in construction / testing 32 Positron Source • Flux Concentrator (FC) is a device which is used as OMD (Optical Matching Device) in a positron production system. FC can produce strongly focused ~solenoid field (6- 10T) out of eddy current that is induced by pulsed primary coil current on its outside. However, FC, generally is limited in its pulse length (< 30 µs). T.Kamitani • Other devices to use as OMD include: – AMD (adiabatic matching device) – a solenoid magnet with adiabatically changing field strength; – QWT (quarter-wavelength transformer) – a short strong solenoid followed by a weaker solenoid; – LL (Lithium lens). They can replace FC for longer pulses but at lower magnetic field, or require additional R&D.