Particle Physics: Status and Perspectives Part 3: Accelerators Manfred Jeitler

2 electron microscope

3 Van-de-Graaf generator

4 Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006 Van de Graaff Accelerator: Applications Changing the Particle Energy F. Sannibale Tandem Scheme Negative ions (H - for example) are created and accelerated through the first stageNegative ions (H - for example) are created and accelerated through the first stage At the end of the first stage the electrons are ‘stripped’ out from the ions (by a gas target for example)At the end of the first stage the electrons are ‘stripped’ out from the ions (by a gas target for example) In the second stage the positive ions (protons in our example) are accelerated. The net energy gain is twice the voltage of the Van de GraaffIn the second stage the positive ions (protons in our example) are accelerated. The net energy gain is twice the voltage of the Van de Graaff st Stage 2 nd Stage

5 Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006 Electrostatic Accelerators: The Simplest Scheme Changing the Particle Energy F. Sannibale Still one of the most used schemes for electron sources Cathode Anode Budker Institute Diode Pierce Geometry

6 Cockroft-Walton accelerator

7 Cockroft-Walton accelerator at CERN

8 Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006 RF Accelerators: Wideroe and Alvarez Schemes Changing the Particle Energy F. Sannibale In 1946 Alvarez overcame to the inconvenient by including the Wideroe structure inside a large metallic tube forming an efficient cavity where the fields were confined. In Ising and Wideroe conceived the first linear accelerator (linac). The revolutionary device was based on the drift tubes scheme. Synchronicity condition: At high frequency the Wideroe scheme becomes lossy due to electromagnetic radiation. During the decelerating half period of the RF, the beam is shielded inside the conductive tubes. 200 MHz RF source from radars The Alvarez structures are still widely used as pre-accelerator for protons and ions. The particles at few hundred keV from a Cockcroft-Walton for example, are accelerated to few hundred MeV.

9 inside of an Alvarez-type accelerating structure

The cyclotron 10

11 Cyclotron r orbit radius p particle momentum e particle charge B magnetic field revolution frequency must be independent of the particle‘s momentum !

12 Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006 Cyclotron and Synchro-cyclotron Changing the Particle Energy F. Sannibale 1939 Nobel Prize Proton Source Uniform Magnetic Field Accelerated Protons Electric Field For non-relativistic particles the revolution period does not depend on energy If the RF frequency is equal to the particles revolution frequency synchronicity is obtained and acceleration is achieved. If the RF frequency is equal to the particles revolution frequency synchronicity is obtained and acceleration is achieved. The synchro-cyclotron is a variation that allows acceleration also of relativistic particles. The RF frequency is dynamically changed to match The synchro-cyclotron is a variation that allows acceleration also of relativistic particles. The RF frequency is dynamically changed to match the changing revolution frequency of the particle The first cyclotron 4.5” diameter (1929). In an uniform magnetic field: In 1946 Lawrence built in Berkeley the 184” synchro-cyclotron with an orbit radius of m and capable of 350 MeV protons. The largest cyclotron still in operation is in Gatchina and accelerates protons to up 1 GeV for nuclear physics experiments. In 1946 Lawrence built in Berkeley the 184” synchro-cyclotron with an orbit radius of m and capable of 350 MeV protons. The largest cyclotron still in operation is in Gatchina and accelerates protons to up 1 GeV for nuclear physics experiments. E. O. Lawrence

13 Fundamental Accelerator Theory, Simulations and Measurement Lab – Arizona State University, Phoenix January 16-27, 2006 The Cyclotron: Different Points of View Changing the Particle Energy F. Sannibale By Dave Judd and Ronn MacKenzie From LBNL Image Library Collection …the operator

14 Synchrotron elements of a synchrotron quadrupole magnet: focussing dipole magnet: to keep particles on track high-frequency accelerating cavity

15 SPS Tunnel Super-Proton-Synchrotron (Geneva)

16 first electron-electron collider: Novosibirsk / Russia VEP MeV

Particle production at a collider  particles do not disintegrate and show what is inside but  the kinetic energy of the colliding particles (protons) is transformed into the mass of another particle

Fixed-target accelerators and colliders 18

19 quadrupole dipole resonator reaction products interaction zone layout of a circular collider

20 LHC dipole

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22 layout of the LHC storage ring (built into the former LEP tunnel)

23 the world‘s largest accelerators accelerator accelerated particles E beam start luminosity [ cm -2 s -1 ] TEVATRONp 2 x 900 GeV PEP IIe + e GeV KEK Be + e GeV HERAp e ± GeV LHC p 2 x 4000 GeV

24 luminosity  (instant) luminosity is rate per cross section  usual units: cm -2 s -1  e.g., cm -2 s -1 corresponds, for a reaction cross section of cm -2 ( = 1 μbarn), to a rate of 1 event per second  for a collider, the luminosity can be calculated as follows:

25 integrated luminosity  number of events collected divided by the cross section  usual units: fb -1 (“inverse femtobarn”), ab -1 (“inverse attobarn”)  an integrated luminosity of 1 fb -1 means that for a process with a cross section of 1 fb, 1 event (on average) should have been collected  or 1000 events for a cross section of 1 nb, etc.  so, 1 inverse attobarn = 1000 inverse femtobarns :  1 ab -1 = 1000 fb -1  physicists are now looking for very rare events, so it is vital to reach not only high energies (so that heavy particles can be produced) but also high luminosities  handling the resulting data rates is a challenge also for the detectors, trigger systems, and readout electronics

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“Accelerator”: do particles really get faster? 29

Years of Design, Construction and Commissioning of the LHC 30 slide

31 accelerator centers worldwide

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photon collider 34

35 layout of a muon storage ring