Lyndon R Evans

The Large Hadron Collider

The Large Hadron Collider (LHC), now close to completion at CERN will provide proton–proton collisions with unprecedented luminosity and energy. It will allow the Standard Model of physics to be explored in an energy range where new phenomena can be studied. This includes the validity of the Higgs mechanism, supersymmetry and CP violation. The machine presents a number of novel features discussed in detail below.

The Large Hadron Collider Project

Publisher Summary This chapter provides a brief overview of Large Hadron Collider (LHC), and discusses its technological challenges. The LHC, approved by the CERN Council in December 1994, is the premiere research tool at the energy frontier of particle physics. The LHC is a unique facility for basic research, providing the worlds highest energies to probe the mysteries of matter and the forces that control it. The machine is located in the existing 27 km circumference tunnel that presently houses the Large Electron Positron collider (LEP). It provides proton-proton collisions with a centre of mass energy of 14 TeV and an unprecedented luminosity of 1034cm -2 s-1. It is also capable of providing heavy ion collisions with a luminosity of 1027 cm -2s -1 using the existing CERN heavy ion source. Space constraints as well as cost considerations dictate a novel two-in-one design of the main magnetic elements, where the two beam channels are incorporated into a single magnetic structure with the two apertures separated by only 194 mm. The main technical challenge of the project is the exploitation of applied superconductivity and large capacity helium cryogenics on an unprecedented scale, to develop them well behind the present state of the art and to integrate them in a reliable way into an accelerator environment.

The Large Hadron Collider (LHC) in the LEP tunnel

After the remarkable start-up of LEP, the installation of a Large Hadron Collider, LHC, in the LEP tunnel will open a new era for the High Energy Physics. This report summarizes the main LHC parameters and subsytems and describes the more recent studies and developments.

The Large Hadron Collider-present status and prospects

The Large Hadron Collider (LHC), due to be commissioned in 2005, will provide particle physics with the first laboratory tool to access the energy frontier above 1 TeV, In order to achieve this, protons must be accelerated and stored at 7 TeV, colliding with an unprecedented luminosity of 10/sup 34/ cm/sup -2/ s/sup -1/. The 8.3 Tesla guide field is obtained using conventional NbTi technology cooled to below the lambda point of helium. Considerable modification of the infrastructure around the existing Large Electron Positron collider (LEP) tunnel is needed to house the LHC machine and detectors. The project is advancing according to schedule with most of the major hardware systems including cryogenics and magnets under construction, A brief status report is given and future prospects are discussed.

Transverse emittance measurement with a rapid wire scanner at the CERN SPS

Abstract A simple almost non-destructive device has been built to accurately measure the transverse emittances of the proton and antiproton beams in the CERN SPS collider. A fine wire passing rapidly through the beams acts as a target for the production of high energy secondary particles. Use is made of the strong directivity of the particle production to separately record the profiles of the two beams using scintillators and photomultipliers placed close to the beam pipe in the downstream proton and antiproton directions. The wire scanners are also used to measure the emittance of high-intensity proton beams during normal fixed-target operation using the secondary emission (depletion) current leaving the wire since in this case the directivity is not required.

Acceleration and Storage of a Dense Single Bunch in the CERN SPS

First tests of the lifetime of a normal SPS beam stored for several hours at 200 and 270 GeV were encouraging. The natural logarithmic decay time is in excess of 24 hours. However, in the proton-antiproton scheme, 200 MHz bunches containing fifty times the normal design population of particles are to be injected into the SPS above transition at 26 GeV, accelerated and stored. Lacking the hardware to inject at so high an energy, we first injected bunches of 1011 protons at 10 GeV accelerating them through transition but found it difficult to pag transitionwith more than 40% of this design population . Nevertheless we report some interesting observations on head-tail and negative-mass effects which limited intensity during these tests.

The Large Hadron Collider (LHC)

The Large Hadron Collider (LHC), now close to completion at CERN will provide proton–proton collisions with unprecedented luminosity and energy. It will allow the Standard Model of physics to be explored in an energy range where new phenomena can be studied. This includes the validity of the Higgs mechanism, supersymmetry and CP violation. The machine presents a number of novel features discussed in detail below.

Large Hadron Collider (LHC)

The Large Hadron Collider (LHC) is located at the European Laboratory for Particle Physics (CERN) ne…

Beam effects in hadron colliders

Potential limitations to machine performance in hadron colliders is considered. (AIP)Potential limitations to machine performance in hadron colliders is considered. (AIP)

Performance Limitations of the CERN SPS Collider

The SPS has now accumulated more than 10 months of operation as a proton-antiproton collider spread over 3 long physics runs. During this time the peak luminosity has been pushed up to 3.5×1029 cm-2S-1 and the luminosity lifetime to almost 30 hours. Different physical phenomena limit the machine performance at various times during injection and storage. The peak luminosity is governed by the number of bunches per beam and the emittance and intensity per bunch as well as by the horizontal and vertical beta values at the experimental insertions. Although the transverse emittances and antiproton intensity are defined by the injector chain, the proton bunch intensity is mainly limited by the microwave instability in the SPS itself. The low-beta insertions have been pushed to the limit of available quadrupole strength and chromaticity correction capability at the maximum storage momentum of 315 GeV/c (ßH = 1m, ßV = 0,5m). The luminosity lifetime in the first few hours of storage is limited by the transverse emittance growth of the dense proton bunches due to intrabeam scattering1,2. As the store progresses, the proton bunch decay rate increases due to the growth of the longitudinal emittance (also through intrabeam scattering), finally becoming the dominant contributing factor in governing the luminosity lifetime. The beam-beam interaction limits the usable area in tune space to a very small region free of 10th order resonances3. Consequently, the total tune spread must be kept below 0.025, allowing only 3 bunches per beam without separation at the unwanted crossings.