A. Bay Beijing October Accelerators We want to study submicroscopic structure of particles. Spatial resolution of a probe ~de Broglie wavelength = 1/p => increase energy of probes. target r p probe The collider is the most efficient way to get the max usable energy: collider with fixed target of mass m 2 (E cm ) 2 =

A. Bay Beijing October General structure RF from Klystrons In addition: sophisticated instrumentation for the control of the orbit

A. Bay Beijing October A cavity 

A. Bay Beijing October Energies of Colliders vs time LHC: starting date 2007

A. Bay Beijing October Max Energy limiting factors * Need powerful magnets to curb the orbit * Synchrotron radiation in a machine of radius r and energy E goes like E 4 : Suppose you want an energy of 500 GeV. With electrons you must increase the klystron power by ~ (500/50) 4 ! Consider like baseline design the LEP machine with a radius of 4.3 km. At 50 GeV/beam the power dissipated is of the order of W per electron. There are ~ electrons in the LEP => 10 5 W needed from the klystrons. 2 possibilities: use protons (m p =2000m e ) or increase r.

A. Bay Beijing October The proton collider Because the p is a composite particle the total beam E cannot be completely exploited. The elementary collisions are between quarks or gluons which pick up only a fraction x of the momentum: proton quarks spectators quarks spectators p2p2 p1p1 x1p1x1p1 x2p2x2p2 momentum available is only x 1 p 1 + x 2 p 2

A. Bay Beijing October Luminosity Interaction rate for a process of cross-section  rate [s  ] =  L The luminosity of a collider is proportional to the currents of the 2 beams I 1, I 2, and inversely proportional to their section A, n i are the number of particles per bunch, b the number of bunches, f the frequency of the orbit. For gaussian bunch profiles: yy xx

A. Bay Beijing October Example: LEP

A. Bay Beijing October Example of L calculation for LEP I= 1.38 and 1.52 mA e=  C b = 8... close to the real (measured) value of ~

A. Bay Beijing October Example of rate calculation for LEP Cross sections for processes at the Z peak: where from rate [s  ] =  L assuming we obtain an hadronic rate of 0.3 s  In one year 3x10 7 s, assuming that the system is on duty for 1/3 of the time, we have an "integrated luminosity" of 10 7 x = cm   10 5  nb  The number of hadronic events/year is ~

A. Bay Beijing October Luminosity vs time

A. Bay Beijing October The Large Hadron Collider Build a 7 GeV/beam machine in the LEP tunnel.

A. Bay Beijing October LHC LHCb point 8 LHCb Pb Geneva jet d'eau Alps Leman lake

A. Bay Beijing October viewed from the sky on July 13, 2005 Jet d’eau ALTAS surface buildings CERN Genève Salève new wood building

A. Bay Beijing October LHC magnets ~1650 main magnets (~1000 produced) + a lot more other magnets 1232 cryogenic dipole magnets (~800 produced, 70 installed): –each 15-m long, will occupy together ~70% of LHC’s circumference ! Lowering of 1st dipole into the tunnel (March 2005) B fields of 8.3 T in opposite directions for each proton beam Cold mass (1.9 K) Joining things up Cryogenic services line

A. Bay Beijing October LHC schedule —Beam commissioning starting in Summer 2007 —Short very-low luminosity “pilot run” in 2007 used to debug/calibrate detectors, no (significant) physics —First physics run in 2008, at low luminosity (10 32 –10 33 cm –2 s –1 ) —Reaching the design luminosity of cm –2 s –1 will take until 2010

A. Bay Beijing October LHC parameters —Ecm = 14 TeV —Luminosity ~ cm -2 s -1 generated with — protons/bunch —  t = 25 ns bunch crossing —bunch transverse size ~15  m —bunch longitudinal size ~ 8cm — crossing angle  =200 mrad The proton current is ~1A, ~500 Mjoules/beam (100kg TNT) 25 ns  detector

A. Bay Beijing October CLIC The Compact LInear Collider CLIC is the name of a novel technique to produce the RF required for acceleration, based on a Two Beam Acceleration (TBA) system. The goal is to have a gradient of acceleration of the order of 150 MeV/m. Aa GeV machine would be 5 km long sub-nanometer beam !!!!!!!!! 30 GHz

A. Bay Beijing October CLIC electron beam to be accelerated Low E, very high intensity beam used to produce RF

A. Bay Beijing October The CLIC idea A gradient of 150 MeV/m requires a RF of ~30 GHz. Klystrons are limited at ~10 GHz => go to TBA: 1) create a beam of ~ 1 GeV electrons made of bunches 64 cm apart 2) reorganize in time the bunches so that they are 2 cm apart: this corresponds to 0.67 ns at the speed of light 3) send the bunches into passive microwave devices (Power Extraction and Transfer Structure, PETS) where a 30 GHz radio-wave is excited and then transferred by short waveguides to the main accelerator.

A. Bay Beijing October CLIC Test Facility 3 CTF3 Produce a bunched 35 A electron beam to excite 30 GHz PETS. Accelerate a 150 MeV electron beam up to 0.51 GeV

A. Bay Beijing October CTF3 first phase has proven the possibility to reduce the pulse spacing to the nominal value of 0.67 ps.

A. Bay Beijing October Nanometer size beam Requires a nanometric stability of all the components, in particular the last quadrupole. geophone Need to fight (hard) against several possible sources of vibrations (ex.: cooling liquid), ground motion, etc.

A. Bay Beijing October ground motion Stabilization Use a combination of active and passive stabilization techniques quadrupole motion 1

A. Bay Beijing October Luminosity gain w/wo stabilization ~70% of the nominal luminosity has been obtained Simulation of the beam collision behaviour

A. Bay Beijing October The experiments e + e  collisions and  collisions