Lecture 2 - Overview of Accelerators II ACCELERATOR PHYSICS MT 2009 E. J. N. Wilson

Lecture 2 – Overview II- Contents Weak focusing in a synchrotron Strong focusing The “n-value” Cosmotron people Strong focusing CERN at BNL CERN 25 GeV PS CERN’s rings SPS Center of mass v. Fixed target The first collider -AdA ISR AND PS Luminosity Physics of electrons v protons LEP Superconducting magnets

Weak focusing in a synchrotron The Cosmotron magnet Vertical focussing comes from the curvature of the field lines when the field falls off with radius ( positive n-value) Horizontal focussing from the curvature of the path The negative field gradient defocuses horizontally and must not be so strong as to cancel the path curvature effect

The “n-value” As the C magnet saturates the n value – which is the rate of droop – increases

Cosmotron people E.Courant -Lattice Designer Stan Livingston - Boss Snyder -theorist Christofilos - inventor FOURGUYS.pct

Strong focussing

CERN at BNL Odd Dahl, Frank Goward, and Rolf Widerö (right hand trio) Fig.3(CERNVISITORS).pct

CERN 25 GeV PS

CERNS RINGS

SPS

Center of mass v. Fixed target

AdA - The first collider e-plus-minus

ISR AND PS ISR+PS.pct

Luminosity Imagine a blue particle colliding with a beam of cross section area - A Probability of collision is For N particles in both beams Suppose they meet f times per second at the revolution frequency Event rate Make big Make small LUMINOSITY

SPS

Physics of the electron v. protons When we collide Protons we collide complex assemblies of three quarks Only two quarks interact Their available energy is on average only 10% of the total centre of mass energy We do not know which quarks they are Hence in some ways 100 GeV LEP is as good as 1000 GeV TEVATRON HENCE THE RETURN TO LEP AFTER SPS AND THEN LHC AFTER LEP

LEP LEP(small).pct

Inside LEP

The Tevatron at FNAL Fermilab’s superconducting Tevatron can just be seen below the red and blue room temperature magnets of the 400 GeV main ring.

The Large Hadron Collider (LHC) The project was first proposed in 1982 at a Snowmass Study, organised by the APS. At a cost of $2.9B to $3.2B, it was supposed to re-establish US supremacy in the field of high-energy particle physics following the discovery in Europe of the W and Z. The next step was carried out. By 1986 a detailed design study, by a Central Design Group set up under Maury Tigner at Lawrence Berkeley Laboratory, was complete and in 1987 President Reagan set in motion the search for a site. In 1988 Waxahatchie, Texas was announced as the successful candidate and construction commenced. This decision was, perhaps, influenced by then Vice-President George Bush (senior) of Texas, Jim Wright of Fort Worth, then Speaker of the House of Representatives, and a powerful Senator, Lloyd Bentsen, also from Texas. Meanwhile the cost, taking into account the more realistic estimates of the Central Design Group, and including the proposed experimental facilities, had risen from the initial estimate of 2.9 B$ to 3.2 B$ and then to 5.3 B$ in 1986. The DOE took over the management of the project from the CDG and determined that the traditions of technical and cost control that had been built up in large laboratories, like Fermilab, were to be abandoned in favour of methods judged more appropriate for a project of this size. Contracts were placed and subsystems procured in a manner that had hitherto been used for large defense projects. This led to further escalation, first to 5.9 B$ and then, as review teams included into account “site-specific” costs, to 7.2 B$ and then 8.2 B$ (DOE, 1991). The final straw came when an Independent Cost Estimating Team of the DOE (1993) added 2.5 B$ for “peripheral expenses which would not have been incurred if the SSC had not been there”. The SSC was given a year’s reprieve but by 1994 when the US Congress saw fit to cut their losses and terminate the project the estimate was 11.8 B$. The reasons for cancellation were not entirely budgetary. There was a rival project – the Space Station – that many in the House of Representatives preferred.

Superconducting magnets

Summary Strong focusing CERN at BNL CERN 25 GeV PS Center of mass v. Fixed target The first collider -AdA ISR AND PS Luminosity SPS Antiproton production and cooling CERN Antiproton Accumulator LEP Superconducting magnets