Extreme Energy Densities Research Articles

Commissioning and calibration of the Zero Degree Calorimeters for the ALICE experiment

The ALICE experiment at the CERN LHC will study the properties of matter at the extreme temperature and energy density conditions produced in heavy ion collisions. The impact parameter of the collision will be estimated by means of the Zero Degree Calorimeters (ZDC), that measure the energy carried away by the non-interacting (spectator) nucleons. All the spectator nucleons have the same energy, therefore the calorimeter response is proportional to their number, providing a direct information on the centrality of the collision. Two identical sets of hadronic calorimeters are located at opposite sides with respect to the interaction point, 116 m away from it, where the two LHC beams circulate in two different pipes. Each set of detectors consists of a neutron (ZN) calorimeter, placed between the two beam pipes and a proton (ZP) calorimeter, positioned externally to the outgoing beam pipe. The ZDC are spaghetti calorimeters, which detect the Cherenkov light produced by the charged particles of the shower in the quartz fibers, acting as the active material embedded in a dense absorber matrix. In summer 2007 the ZN and ZP calorimeters have been placed on a movable platform and then installed in the LHC tunnel. The results of the commissioning studies are shown. The monitoring systems adopted to control the stability of the PMT responses, i.e. light injection with a laser diode and cosmic rays, are described in detail. The foreseen calibration with e.m. dissociation events in Pb-Pb collisions will also be discussed. Finally the first measurements carried out during the commissioning in the LHC tunnel will be presented.

From laser fusion to laser accelerators: basic studies into high power laser plasmas

High power laser beams are unique in concentrating energy both in space and time. They can convert dense matter into plasma of extreme energy density. Here I shall focus on two outstanding applications. Laser fusion relies on isentropic compression of nuclear fuel by convergent hydrodynamic flow, and I discuss the gas dynamics underlying ignition. Laser accelerators depend on relativistic laser plasma interaction, generating non-neutral plasmas and accelerating fields in the range of TV m−1. Self-organizing plasma structures such as channels and bubbles drive intense particle beams. Such beams may allow for fast ignition of inertial confinement fusion.

Preparation for heavy-flavour measurements with ALICE at the LHC

ALICE [ALICE Collaboration, JINST 0803 (2008) S08002] will study nucleus–nucleus and proton–proton collisions at the LHC. The main goal of the experiment is to investigate the properties of QCD matter at the extreme energy densities that will be reached in Pb–Pb collisions. Heavy quarks (charm and beauty) are regarded as powerful tools for this study. After briefly reviewing the ALICE heavy-flavour program, we will describe the preparation for the first measurements to be performed with pp collisions.

The trigger system of the ALICE muon spectrometer at the LHC

The ALICE experiment aims at investigating the properties of strongly interacting matter at the extreme energy density reached in heavy ion collisions at the LHC. The trigger system of the muon spectrometer consists in four planes of Resistive Plate Chamber (RPC) detectors operated in streamer mode, 21 k front-end channels and fast-decision electronics, covering an area of 140 m 2. It is designed to reconstruct (muon) tracks, in a large background environment, to provide a fast trigger signal. Indeed, a trigger decision is delivered each 25 ns (40 MHz) with a total latency of 800 ns. The hit position on the RPC is measured in two orthogonal directions with an accuracy of about 1 cm. Selected aspects of the Muon Trigger design will be described. The performances, of both detectors and electronics, measured with dedicated test tools and cosmic rays during the commissioning runs carried out in the first half of year 2008 will be reported.

The ALICE muon spectrometer and related physics

ALICE is the LHC experiment dedicated to the study of heavy-ion collisions at extreme energy density where formation of the quark–gluon plasma is expected. Among the different observables, open heavy flavors and heavy quarkonia states are especially relevant. Indeed they will be copiously produced and they will provide sensitive information on the collision. In this paper, the ALICE muon spectrometer will be described as well as the installation status. A few selected topics concerning the muon physics will be addressed and the related expected performances of the ALICE muon spectrometer will be given.

The ALICE experiment at the CERN LHC

ALICE (A Large Ion Collider Experiment) is a general-purpose, heavy-iondetector at the CERN LHC which focuses on QCD, the strong-interactionsector of the Standard Model. It is designed to address the physics ofstrongly interacting matter and the quark-gluon plasma at extreme valuesof energy density and temperature in nucleus-nucleus collisions. Besidesrunning with Pb ions, the physics programme includes collisions withlighter ions, lower energy running and dedicated proton-nucleus runs.ALICE will also take data with proton beams at the top LHC energy tocollect reference data for the heavy-ion programme and to address severalQCD topics for which ALICE is complementary to the other LHC detectors.The ALICE detector has been built by a collaboration including currentlyover 1000 physicists and engineers from 105 Institutes in 30 countries. Its overall dimensions are 16 × 16 × 26 m3 with a total weight of approximately10 000 t. The experiment consists of 18 different detector systems eachwith its own specific technology choice and design constraints, drivenboth by the physics requirements and the experimental conditions expectedat LHC. The most stringent design constraint is to cope with the extremeparticle multiplicity anticipated in central Pb-Pb collisions. Thedifferent subsystems were optimized to provide high-momentumresolution as well as excellent Particle Identification (PID) over a broadrange in momentum, up to the highest multiplicities predicted for LHC.This will allow for comprehensive studies of hadrons, electrons, muons,and photons produced in the collision of heavy nuclei.Most detector systems are scheduled to be installed and ready for data taking by mid-2008 when the LHC is scheduled to start operation, with the exception ofparts of the Photon Spectrometer (PHOS), Transition Radiation Detector(TRD) and Electro Magnetic Calorimeter (EMCal). These detectors will becompleted for the high-luminosity ion run expected in 2010.This paper describes in detail the detector components asinstalled for the first data taking in the summer of 2008.

Laser performance operations model (LPOM): a computational system that automates the setup and performance analysis of the national ignition facility

The National Ignition Facility (NIF) is a stadium-sized facility containing a 192-beam, 1.8 MJ, 500-TW, 351-nm laser system together with a 10-m diameter target chamber with room for many target diagnostics. NIF will be the world's largest laser experimental system, providing a national center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. A computational system, the Laser Performance Operations Model (LPOM) has been developed and deployed that automates the laser setup process, and accurately predict laser energetics. LPOM determines the settings of the injection laser system required to achieve the desired main laser output, provides equipment protection, determines the diagnostic setup, and supplies post shot data analysis and reporting.

Status of the National Ignition Facility Integrated Computer Control System (ICCS) on the path to ignition

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is a stadium-sized facility under construction that will contain a 192-beam, 1.8-MJ, 500-TW, ultraviolet laser system together with a 10-m diameter target chamber with room for multiple experimental diagnostics. NIF is the world's largest and most energetic laser experimental system, providing a scientific center to study inertial confinement fusion (ICF) and matter at extreme energy densities and pressures. NIF's laser beams are designed to compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. NIF is comprised of 24 independent bundles of eight beams each using laser hardware that is modularized into more than 6000 line replaceable units such as optical assemblies, laser amplifiers, and multi-function sensor packages containing 60,000 control and diagnostic points. NIF is operated by the large-scale Integrated Computer Control System (ICCS) in an architecture partitioned by bundle and distributed among over 800 front-end processors and 50 supervisory servers. NIF's automated control subsystems are built from a common object-oriented software framework based on CORBA distribution that deploys the software across the computer network and achieves interoperation between different languages and target architectures. A shot automation framework has been deployed during the past year to orchestrate and automate shots performed at the NIF using the ICCS. In December 2006, a full cluster of 48 beams of NIF was fired simultaneously, demonstrating that the independent bundle control system will scale to full scale of 192 beams. At present, 72 beams have been commissioned and have demonstrated 1.4-MJ capability of infrared light. During the next 2 years, the control system will be expanded in preparation for project completion in 2009 to include automation of target area systems including final optics, target positioners and diagnostics. Additional capabilities to support fusion ignition shots in a National Ignition Campaign (NIC) beginning in 2010 will include a cryogenic target system, target diagnostics, and integrated experimental shot data analysis with tools for data visualization and archiving. This talk discusses the current status of the control system implementation and discusses the plan to complete the control system on the path to ignition.

Heavy-quark and electromagnetic probes

The study of heavy-flavour production and electromagnetic probes in nuclear collisions provides unique access to the properties of strongly interacting matter at extreme energy densities. Highlights of experimental results presented at the Quark Matter 2006 conference are reviewed and open issues are discussed.

HADRON FORMATION IN HIGH ENERGY ELEMENTARY AND NUCLEAR COLLISIONS

We consider the dynamical origin of the apparent statistical equilibrium that governs the yields, and yield ratios, of all hadron and resonance species (consisting of the three light quark flavours) produced in nucleus-nucleus collisions from AGS via SPS to RHIC energies [Formula: see text]. This hadro-chemical equilibrium state is well described, overall, by the grand canonical, quasi-classical Gibbs ensemble of all corresponding hadrons and resonances. In order to pin down the stochastic elements, featured by the dynamical evolution prior to hadron formation and hadronic "chemical" (i.e. species) freeze-out, and determining the eventual equilibrium state, we concentrate on the high energy domain, [Formula: see text], where a model of primordial perturbative QCD partonic shower evolution appears plausible. For guidance concerning a hadronization model we revisit the QCD description of jet-induced hadron formation in e+e- annihilation at LEP energy. At the end of the pQCD partonic shower evolution a stage of color neutralization and flavour recombination leads to transition into non perturbative QCD clusters or strings, that decay to hadrons/resonances under phase space dominance. The combination of stochastic shower multiplication and cluster decay to the phase space defined by the hadron/resonancemass and spin spectrum results in a hadronization output featuring statistical equilibrium of the species, which is well described by the canonical Gibbs ensemble. We then assume that hadronization in A + A collisions occurs from a similar stage of singlet cluster formation. However, owing to the extreme overall energy density these clusters should overlap spatially, giving rise to extended super-cluster formation, increasing with [Formula: see text], A and collision centrality. In the limit of an extended volume decaying coherently, hadronization is free of local quantum number conservation constraints. This leads to strangeness enhancement and explains the success of a grand canonical description.

VUV-heating of plasma layers and their use as ultrafast switches

We report on new possibilities to generate solid-density plasma at extreme energy density by intense VUV beams. Here we consider 100 fs pulses of 30 eV photons focused to 1016 and 1018 W/cm2. The temperature evolution in 50 nm thick aluminum foils is discussed on the basis of simulations, performed with the one-dimensional radiation hydrodynamics code MULTI-fs. For 30 eV photons, the foil is shown to switch from transmission to reflection mode on a femto-second time-scale; this is due to the rapid change of the plasma frequency during laser heating which may turn an initially transparent Al-foil into an opaque one. The switching-time depends on the intensity of the laser pulse. Also layered heating structures inside the foil are discussed which occur due to reflection at the rear surface.

The National Ignition Facility: Laser Performance and First Experiments

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. NIF will be the world’s largest and most energetic laser experimental system, providing a scientific center to study inertial confinement fusion (ICF) and matter at extreme energy densities and pressures. NIF’s energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures approaching 108 K and 1011 bar, conditions that exist naturally only in the interior of stars, planets and in nuclear weapons. NIF has successfully activated, commissioned, and utilized the first four beams of the laser system to conduct over 300 shots between November 2002 and August 2004. NIF laser scientists have established that the laser meets nearly all performance requirements on a per beam basis for energy, uniformity, timing, and pulse shape. Using these four beams, ICF and high-energy-density physics researchers have conducted a number of experimental campaigns resulting in high quality data that could not be reached on any other laser system. We discuss the successful NIF Early Light Program including details of laser performance, examples of experiments performed to date, and recent advances in the ICF Program that enhance prospects for successful achievement of fusion ignition on NIF.

The National Ignition Facility

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is a stadium-sized facility that, when completed in 2008, will contain a 192-beam, 1.8-megajoule, 500-terawatt, ultraviolet laser system together with a 10-m-diam target chamber and room for 100 diagnostics. NIF is the world's largest and most energetic laser ex- perimental system and will provide a scientific center to study inertial confinement fusion and matter at extreme energy densities and pres- sures. NIF's energetic laser beams will compress fusion targets to con- ditions required for thermonuclear burn, liberating more energy than re- quired to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures approaching 10 8 K and 10 11 bar, conditions that exist naturally only in the interior of stars and planets. NIF has completed the first phases of its laser commissioning program. The first four beams of NIF have generated 106 kJ in 23-ns pulses of infrared light and over 16 kJ in 3.5-ns pulses at the third harmonic (351 nm). NIF's target experimental systems are being commissioned and experi- ments have begun. This work provides a detailed look at the NIF laser systems, laser and optical performance, and results from recent laser commissioning shots. We follow this with a discussion of NIF's high- energy-density and inertial fusion experimental capabilities, the first ex- periments on NIF, and plans for future capabilities of this unique facility. © 2004 Society of Photo-Optical Instrumentation Engineers. (DOI: 10.1117/1.1814767) Subject terms: high-energy-density physics; inertial confinement fusion; labora- tory astrophysics; solid-state lasers.

National Ignition Facility wavefront requirements and optical architecture

With the first four of its eventual 192 beams now executing shots and generating more than 100 kJ of laser energy at its primary wavelength of 1.06 µm, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is already the world's largest and most energetic laser. The optical system performance requirements that are in place for NIF are derived from the goals of the missions it is designed to serve. These missions include inertial confinement fusion (ICF) research and the study of matter at extreme energy densities and pressures. These mission requirements have led to a design strategy for achieving high-quality focusable energy and power from the laser and to specifications on optics that are important for an ICF laser. The design of NIF utilizes a multipass architecture with a single large amplifier type that provides high gain, high extraction efficiency, and high packing density. We have taken a systems engineering approach to the practical implementation of this design that specifies the wavefront parameters of individual optics to achieve the desired cumulative performance of the laser beamline. This paper provides a detailed look at the causes and effects of performance degradation in large laser systems and how NIF has been designed to overcome these effects. We also present results of spot size performance measurements that have validated many of the early design decisions that have been incorporated in the NIF laser architecture.

The National Ignition Facility: enabling fusion ignition for the 21st century

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, when completed in 2008, will contain a 192-beam, 1.8 MJ, 500 TW, ultraviolet laser system together with a 10 m diameter target chamber and room for 100 diagnostics. NIF is housed in a 26 000 m2 environmentally controlled building and is the world's largest and most energetic laser experimental system. NIF provides a scientific centre for the study of inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF's energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will study physical processes at temperatures and pressures approaching 108 K and 1011 bar, respectively, conditions that exist naturally only in the interior of stars and planets. NIF is currently configured with four laser beams activated in late 2002. These beams are being regularly used for laser performance and physics experiments, and to date nearly 250 system shots have been conducted. NIF's laser beams have generated 106 kJ in 23 ns pulses of infrared light and over 16 kJ in 3.5 ns pulses at the third harmonic (351 nm). A number of target experimental systems are being commissioned in support of experimental campaigns. This paper provides a detailed look at the NIF laser systems, laser and optical performance, and results from laser commissioning shots. We also discuss NIF's high-energy density and inertial fusion experimental capabilities, the first experiments on NIF, and plans for future capabilities of this unique facility.

The national ignition facility high-energy ultraviolet laser system

The National Ignition Facility (NIF), currently under construction at the Lawrence Livermore National Laboratory, is a stadium-sized facility containing a 192-beam, 1 .&Megajoule, 500-Terawatt, ultraviolet laser system together with a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. When completed, NIF will be the world's largest and most energetic laser experimental system, providing an international center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF's 192 energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will allow the study of physical processes at temperatures approaching 10{sup 8} K and 10{sup 11} Bar, conditions that exist naturally only in the interior of stars, planets and in nuclear weapons. NIF is now entering the first phases of its laser commissioning program. The first four beams of the NIF laser system have generated 106 kilojoules of infrared light and over 10 kJ at the third harmonic (351 nm). NIF's target experimental systems are also being installed in preparation for experiments to begin in late 2003. This paper provides a detailed look the NIF laser systems,more » the significant laser and optical systems breakthroughs that were developed, the results of recent laser commissioning shots, and plans for commissioning diagnostics for experiments on NIF.« less

The National Ignition Facility: Status and Plans for the Experimental Program

The National Ignition Facility (NIF), currently under construction at the University of California’s Lawrence Livermore National Laboratory, is a stadium-sized facility containing a 192-beam, 1.8-Megajoule, 500-Terawatt, 351-nm laser system and a 10-meter diameter target chamber with room for nearly 100 experimental diagnostics. NIF is being built by the National Nuclear Security Administration and when completed will be the world’s largest laser experimental system, providing a national center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF’s 192 energetic laser beams will compress fusion targets to conditions where they will ignite and burn, liberating more energy than required to initiate the fusion reactions. NIF experiments will allow the study of physical processes at temperatures approaching 100 million K and 100 billion times atmospheric pressure. These conditions exist naturally only in the interior of stars and in nuclear weapons explosions. In the course of designing the world’s most energetic laser system, a number of significant technology breakthroughs have been achieved. NIF is now entering the first phases of its laser commissioning program. Low-energy preamplifier rod laser shots have been successfully propagated through the entire laser chain. Higher energy shots are planned through the end of 2002. NIF’s target experimental systems are also being installed in preparation for laser performance and experimental capability commissioning starting in 2003.

The National Ignition Facility: Status and Plans for Laser Fusion and High-Energy-Density Experimental Studies

The National Ignition Facility (NIF), currently under construction at the University of California’s Lawrence Livermore National Laboratory, is a stadium-sized facility containing a 192-beam, 1.8-MJ, 500-TW, 351-nm laser system and a 10-m-diam target chamber with room for nearly 100 experimental diagnostics. NIF is being built by the National Nuclear Security Administration and when completed will be the world’s largest laser experimental system, providing a national center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF will provide 192 energetic laser beams that will compress small fusion targets to conditions where they will ignite and burn, liberating more energy than is required to initiate the fusion reactions. NIF experiments will allow the study of physical processes at temperatures approaching 100 million K and 100 billion times atmospheric pressure. These conditions exist naturally only in the interior of stars and in nuclear weapons explosions. In the course of designing the world’s most energetic laser system, a number of significant technology breakthroughs have been achieved. Research is also underway to develop a shorter pulse capability on NIF for very high power and extreme electromagnetic field research and applications. We discuss here the technology challenges and solutions that have made NIF possible, along with enhancements to NIF’s design that could lead to near-exawatt power levels.

High energy atomic physics of astrophysical relevance

The rapid progress in acceleration techniques, notably those of accelerating ions of any desired charge to relativistic energies and of storing them in cooling rings, has brought within the experimental reach a number of atomic processes at high (relativistic) energies. Several of these are of direct astrophysical relevance. This concerns phenomena at extreme energy densities and at extreme electromagnetic fields as well as the dynamics of interaction of relativistic ions with electrons, atoms and intense laser beams. A review of these processes is given, separately for the heavy and for the light ions. The astrophysical interest of this information is indicated whenever applicable.

Production of Nanostructures Under Ultraturbulent Collision Reaction Conditions - Application to Catalysts, Superconductors, CMP Abrasives, Ceramics, and Other Nanoparticles

AbstractThe development, operation and applications of a novel continuous chemical reactor system are described. The system, known as a Multiple Stream Mixer/Reactor (or MMR), produces nanoparticles by direct precipitation from two or more reactant solution streams in an extreme energy density, ultraturbulent, collision reaction region. Sensors and a control system are employed to assure constant mixing conditions and desired stoichiometry in the reaction region. The interaction chamber is designed to allow macro-, meso- and micromixing during processing. This allows control of product purity, yield, size, size distribution, and phase purity. Typical nanoparticle diameters in the one to ten nanometer range are often achievable, with tight size distribution. The MMR can be scaled from development quantities to tons/hour for production applications.