W. Udo Schröder, 2011 Nuclear Experiment 1

W. Udo Schröder, 2011 Nuclear Experiment Elements of a Generic Nuclear Experiment A: Study natural radioactivity (cosmic rays, terrestrial active samples) B: Induce nuclear reactions in accelerator experiments Particle Accelerator  produces fast projectile nuclei Projectile nuclei interact with target nuclei Reaction products are a) collected and measured off line, b) measured on line with radiation detectors Detector signals are electronically processed Ion Source Accelerator Target Detectors Vacuum Chamber Vacuum Beam Transport 2

W. Udo Schröder, 2011 Nuclear Experiment Ionization Process 1. e - impact (gaseous ionization) hot cathode arc discharge in axial magnetic field (duo- plasmatron) electron oscillation discharge (PIG) radio-frequency electrode-less discharge (ECR) electron beam induced discharge (EBIS) 2. ion impact charge exchange sputtering e - /ion beam - + q-q- discharge - + q+q+ Acceleration possible for charged particles  ionize neutral atoms 3

W. Udo Schröder, 2011 Nuclear Experiment Electron Cyclotron Resonance (ECR) Source “Venus” Making an e - /ion plasma 4

W. Udo Schröder, 2011 Nuclear Experiment 5 Overview Accelerator Types Electrostatic Accelerators CascadeVan de GraaffV.d.G. Single &Tandem generatorAccelerator2-3 stages  steady (DC) beam, high quality focusing, energy, currents; but low energies Electrodynamic Accelerators Cyclotrons SynchrotonsLinacs conventional,Wideröe, Alvarez sector-focusing  pulsed (AC) beam, high energies but lower quality focusing, energy definition, lower currents Advanced Technology Accelerators New principles: Collective acceleration, wake-field acceleration conceptual stage

W. Udo Schröder, 2011 Nuclear Experiment Principle of Electrostatic Accelerators Van de Graaff, 1929 Operating limitations: 2 MV terminal voltage in air, MV in pressure tank with insulating gas (SF 6 or gas mixture N 2, CO 2 ) Acceleration tube has equipotential plates connected by resistor chain (R), ramping field down. Typical for a CN: 7-8 MV terminal voltage + - R R R R R R R q+q+ Charger C/m 2 Corona Points 20kV + HV Terminal Ion Source Insulating Acceleration Tube/w EP plates Charging Belt/ Pelletron - Ground Plate Conducting Sphere q+q+ 6

W. Udo Schröder, 2011 Nuclear Experiment “Emperor” (MP) Tandem MP Tandem 15 MV 90 o Deflection/ Analyzing Magnet Vacuum Beam Line Ion BNL, TUNL, Florida, Seattle,…, Geneseo (small),… many around the world. Munich University Tandem Quadrupole Magnet Pumping Station 7

W. Udo Schröder, 2011 Nuclear Experiment Electrodynamic Accelerators: Cyclotron Radio Frequency  field -+ E Principle of operation of electrodynamic (cyclic) accelerators: Short pulses of low accelerating voltage, apply many times. Cyclotrons at MIT, Berkeley, MSU, Texas A&M, …., many around the world (Catania, GANIL). Linacs mostly for electrons or protons. Synchrotons and variations for high energy particle physics. Cyclotron technique: Magnetic holding field, contain particles on circular orbits, apply RF voltage across gaps of 2 half Faraday cages (“D”) shielding most of the orbits. 8

W. Udo Schröder, 2011 Nuclear Experiment Charged Particles in Electromagnetic Fields B: Magnetic guiding field v r Charged particles in electromagnetic fields follow curvilinear trajectories  used to guide particles “optically” with magnetic beam transport system q B Independent of velocity or energy 9

W. Udo Schröder, 2011 Nuclear Experiment Electrodynamic Accelerators: Cyclotron Relativistic effects: m  W =  + m o c 2 Q: Is there technical compensation ? -+ E Electrodynamic linear (LINAC) or cyclic accelerators (cyclotrons, synchrotons) Cyclotrons at MIT, Berkeley, MSU, Texas A&M, …., many around the world (Catania, GANIL) Acceleration, if  field  =  0 Equilibrium orbit r: p = qBr  maximum p max = qBR 10 Radio Frequency  field R

W. Udo Schröder, 2011 Nuclear Experiment Injection and Acceleration Transfer to accelerator Acceleration Injection (axial) Ion trajectory (cyclic) 11

W. Udo Schröder, 2011 Nuclear Experiment 12 Linear Accelerators Wideröe 1928, Alvarez 1946 Linear trajectory, no deflection magnet, no radiative losses Hollow drift tubes, E-field-free interior, contain magn. focusing elements. Accelerating gap between 2 drift tubes on different el. potential U(t) = U 0.sin (  t) 10MHz-3GHz on all gaps  alternating E field switch polarity while particle is hidden. Phase conditions may change during acceleration, particle speed. Q: Is continuous operation possible without loss of particles? q+q+ RF Power Supply L n-1 L n L n+1

W. Udo Schröder, 2011 Nuclear Experiment 13 Phase Stability ideally synchronous particle passes gaps at t n =t s +nT Passage time (at gaps): t=  encountering U(t) ~ U 0 sin(  t) Phase angle of particle:  =  s +  ·(t-t s ), force F=qU 0 /(gap length L) Stability analysis: Stable oscillations about synchronous phase occur for cos  s > 0,   s < 90 0 inject during first quarter cycle! U(t)  E t Nominal t s =  s 

W. Udo Schröder, 2011 Nuclear Experiment CERN PS Proton Linac 14

W. Udo Schröder, 2011 Nuclear Experiment Secondary-Beam Facilities 2 principles: A) Isotope Separator On Line Dump intense beam into very thick production target, extract volatile reaction products, study radiochemistry or reaccelerate to induce reactions in 2 nd target (requires long life times: ms) GANIL-SPIRAL, EURISOL, RIA, TAMU,…. B) Fragmentation in Flight Induce fragmentation/spallation reactions in thick production target, select reaction products for experimentation: reactions in 2 nd target GSI, RIKEN, MSU, Catania, (RIA) G. Raciti,

W. Udo Schröder, 2011 Nuclear Experiment ISOLDE Facility at CERN Primary proton beam CERN-SPS 16

W. Udo Schröder, 2011 Nuclear Experiment Secondary-Beam Accelerator Radiochemical goal (high-T chemistry, surface physics, metallurgy): produce ion beam with isotopes of only one element Ion Source Low-energy LINAC Mass Separator X 1+ High Charge Primary target: oven at C – C, bombarded with beams from 2 CERN accelerators (SC, PS). 17

W. Udo Schröder, 2011 Nuclear Experiment RIA: A New Secondary-Beam Facility One of 2 draft designs : MSU/NSCL proposal 18 Superconducting-RF driver linear accelerator ( 400 kW) All beams up to uranium 200 MeV/nucleon, lighter ions with increasing energy (protons at 600 MeV/nucleon)

W. Udo Schröder, 2011 Nuclear Experiment Secondary Beam Production Bombard a Be target with 1.6-GeV 58 Ni projectiles from SCC LNS Catania Particle Identification Matrix  E x E EE EE E Particle Target 19

W. Udo Schröder, 2011 Nuclear Experiment ISOLDE Mass Separators General Purpose Separator calculated 20

W. Udo Schröder, 2011 Nuclear Experiment Secondary ISOLDE Beams Yellow: produced by ISOLDE n-rich, n-rich Sn: A = low energy O: A = low energy Source: CERN/ISOLDE ISOLDE accepts beams from several CERN accelerators (SC, PS) 21