CERN Large Hadron Research Articles

Design and testing of a high voltage coil for the kicker magnets of CERN's Large Hadron Collider

A prototype LHC magnet has been built and tested at voltages of up to 35 kV. This paper describes the design of the high voltage excitation coil of the magnet, the different options for the coil insulation material and the adopted manufacturing process. It discusses the loss-factor measurements that have been carried out as part of the acceptance tests. Finally, it reports on endurance tests of the coil when it is mounted in the yoke and operated in a pulsed mode. The two dumping systems are furthermore used to remove the counter-rotating beams safely during the setting up of the accelerator and in case of emergencies. Reliable and accurate dumping is of prime importance. Uncontrolled beam losses will cause damage or destruction of adjacent superconducting magnets and will induce unacceptable heat losses in the cryogenic cooling system.

Proton irradiation of various resistivity silicon detectors

Future high energy physics experiments at CERN's Large Hadron Collider will use high precision silicon detectors for tracking purposes. The hadronic component of the radiation received threatens the lifetime of these detectors and it is vital to choose the silicon starting material to maximise the performance and lifetime. Ion-implanted silicon detectors with various initial resistivities and germanium concentrations have been irradiated with high energy protons up to a fluence of 10/sup 14/ cm/sup -2/. The change in leakage current and full depletion voltage have been studied both as a function of fluence and of time after irradiation. Measurements were made up to 100 days post-irradiation at room temperature and then using heating techniques to accelerate processes up to the equivalent of over 10 years at room temperature. The leakage-current damage constant is shown to be independent of the starting material while the conduction type inversion point and the long-term annealing of the depletion voltage are sensitive to the initial resistivity and impurity concentrations.

High rate operation and lifetime studies with micro-strip gas chambers

Micro-Strip Gas Chambers manufactured on supports with low resistivity, 109 to 1012 Ω cm, can withstand without gain loss due to charging-up the very high rates expected in tracking detectors at CERN's Large Hadron Collider. Several technologies allowing to realize supports in this range of resistivity are described, namely electron-conducting glass and thin-layer conductive coatings.At very high radiation fluxes, the formation and deposit on electrodes of thin insulating layers cause premature deterioration of the detector. The ageing rate is found to be extremely sensitive to the purity and nature of the filling gas, and can be kept small only by a careful selection of the manufacturing materials. Experimental results on ageing are presented for several types of detectors.

Calibration of dosimeters for the cryogenic irradiation of composite materials using an electron beam

In order to evaluate materials such as superconducting magnet components for use in the high-dose radiation environment of the large recirculating charged-particle accelerators such as CERN's Large Hadron Collider (Switzerland/France), CEBAF (Virginia), HERA (Hamburg, Germany), Fermilab's Tevatron (Illinois), and the recently cancelled Superconducting Super Collider (Texas), a study of the radiation resistance of these materials was carried out. These materials must withstand absorbed doses as large as 10 7Gy at a temperature of 4 K and were tested under these conditions using an electron beam from a 20 MeV linear accelerator. This paper describes the dosimetry at such very large doses and how the dose was delivered to the samples.

Optical timing, trigger and control distribution for LHC detectors

At CERN's future Large Hadron Collider, timing, trigger-accept and control signals must be distributed from a small number of sources to many thousands of front-end electronics destinations located on the ATLAS and CMS detectors. The LHC timing reference must be delivered with sub-nanosecond jitter and programmable phase. First-level trigger decisions must be broadcast from the central trigger processor to all the front-end pipeline controllers and delivered synchronously with the appropriate bunch identification, compensated for particle flight times and detector, electronics and propagation delays. In addition, broadcast control signals and individually-addressed controls and parameters such as calibration data have to be distributed. This paper describes how it is planned to broadcast all the signals over entirely passive multichannel optical fiber networks with uncontrolled path lengths. It reviews some of the technology options which are currently available and those which are likely to mature within the time frame of LHC preparation. It discusses how synchronization can be established over the system and describes how different distribution network configurations, laser transmitters and encoding methods can be used to deliver the signals using optoelectronic receivers which are becoming affordable for extensive deployment. >

Crystal Detectors in Particle Physics

ABSTRACTWe review the principal characteristics driving the design of precision calorimeters composed of inorganic crystal scintillators now in operation (L3, CLEO II) or developed for the next generation of particle physics experiments. The unique discovery potential of these detectors (1.5 to 50 m3of crystals; 104to > 105elements) is the result of their high electron and photon energy resolution over a wide energy range, uniform hermetic acceptance and fine granularity.Experiments at CERN's multi-TeV Large Hadron Collider (LHC) will search for the Higgs particles thought to be responsible for mass, and for many other new physics processes. In order to exploit the intrinsically high resolution of crystal detectors, exceptionally high speed (1 to 30 ns decay time) and radiation resistance are required. BaF2and CeF3are currently the preferred choices, and higher density alternatives such as PbWO4are under investigation.Lower energy, high luminosity experiments that will measure rare particle decays, and explore the violation of the fundamental “CP” symmetry that may be related to the predominance of matter over antimatter in our universe, have chosen Cesium Iodide for its combination of high light output, speed, and radiation resistance.Recent developments by Caltech include the use of photons generated by anH−beam from an RFQ accelerator to calibrate and provide sub-percent resolution in the L3 BGO calorimeter, and anin situoptical bleaching technique that renders large BaF2crystals now mass produced in China radiation hard up to dose levels ≳l 10 MegaRads.

Signals of quark-gluon plasma

Production and observation of a quark-gluon plasma (QGP) is one of the most ambitious goals of the ultrarelativistic heavy ion experiments being carried out at CERN's super proton synchrotron (SPS) and at Brookhaven's Alternating Gradient Synchrotron (AGS). Future experiments at Brookhaven's Relativistic Heavy Ion Collider (RHIC) and at CERN's Large Hadron Collider (LHC) will give a new dimension to this search. In this review, the physics of QGP is presented with particular emphasis on its promising signatures existing in the literature. We hope that the present survey will lead us to identify some unambiguous signatures of QGP before the advent of RHIC and LHC experiments.

Nucleons as Skyrmions

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Delayed Fission

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Order- alpha s calculation of hadronic ZZ production.

An order-{alpha}{sub {ital s}} calculation of {ital pp}{sup ({minus})}{r arrow}{ital ZZ}+{ital X} is presented. Results are given for the total cross section and differential distributions for Fermilab Tevatron, CERN Large Hadron and Collider, and Superconducting Super Collider energies. The calculation utilizes a combination of analytic and Monte Carlo integration methods which makes it easy to calculate a variety of observables and to impose experimental cuts.

Electric Dipole Moment Of The Neutron

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Deep Inelastic Lepton-Nucleon Scattering

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Aspects Of Chaos In Nuclear Physics

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Electroweak Symmetry Breaking: Unitarity, Dynamics, And Experimental Prospects

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Nuclear Techniques For Subsurface Geology

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Giant Resonances in Excited Nuclei

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Observatory for Ultra High-Energy Processes: The Fly's Eye

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Nuclear Processes at Neutron Star Surfaces

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

The Distribution of Charge in the Nucleus

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More

Nuclear Radiation Shielding

This article is devoted to the status of the electroweak theory on the eve of experimentation at CERN's Large Hadron Collider (LHC). A compact summary of the logic and structure of the electroweak theory precedes an examination of what experimental tests ... Read More