Ion Physics Research Articles

Measurement of Differential Cross Section for the 64Zn(n,α)61Ni Reaction at 2.54, 4.00, and 5.50 MeV

By using a twin-gridded ionization chamber, differential cross-section data of the 64Zn(n,α)61Ni reaction were measured at neutron energies of 2.54, 4.00, and 5.50 MeV. The experiment was performed at the 4.5-MV Van de Graaff accelerator of the Institute of Heavy Ion Physics, Peking University, China. Monoenergetic neutrons of 2.54 MeV were produced through the T(p,n)3He reaction with a solid Ti-T target, and those of 4.00 and 5.50 MeV were produced through the D(d,n)3He reaction with a deuterium gas target. The absolute neutron flux was determined through the 238U(n,f) reaction and a BF3 long counter was used as the neutron flux monitor. Results of the present work are combined with our previous data between 5.0 and 6.5 MeV and compared with other measurements and evaluations.

TPC review

The Time Projection Chamber (TPC) was invented by David Nygren 30 years ago. TPCs have been used as trackers in many particle and heavy ion physics experiments. There are also TPC projects for non-accelerator experiments such as double-beta decay and dark-matter searches. After a presentation of the original idea of the TPC, and the advantages of such a detector, the R&D for the TPC proposed for the future International Linear Collider will be reviewed. This work is being carried out by the LC-TPC collaboration formed recently by several labs from all over the world.

A new computational framework for 2D shape-enclosing contours

In this paper, a new framework for one-dimensional contour extraction from discrete two-dimensional data sets is presented. Contour extraction is important in many scientific fields such as digital image processing, computer vision, pattern recognition, etc. This novel framework includes (but is not limited to) algorithms for dilated contour extraction, contour displacement, shape skeleton extraction, contour continuation, shape feature based contour refinement and contour simplification. Many of the new techniques depend strongly on the application of a Delaunay tessellation. In order to demonstrate the versatility of this novel toolbox approach, the contour extraction techniques presented here are applied to scientific problems in material science, biology, handwritten letter recognition, astronomy and heavy ion physics.

Obituary

József Zimányi, one of the founders of high energy heavy ion physics, passed away in Budapest, Hungary on September 26, 2006. His death is a great loss for science, in particular for the heavy-ion community in Hungary.

HIRFL Today

HIRFL was upgraded from beginning 2000. Besides of researches on nuclear physics, atomic physics, irradiative material and biology, the cancer therapy by heavy ion and hadron physics are being developing. The injector system of SFC+SSC can provide all ions from proton to uranium with higher intensity. The Cooling Storage Ring (CSR) has accelerated beams successful. The ions 12C 6+, 36Ar 18+, 129Xe 27+ have been accelerated up 1000MeV/u, 235MeV/u with about 10 9 ∼ 10 8 ions per spill respectively. The beam momentum dispersion was measured from 4 × 10 −3 to 2 × 10 −4 after cooling by the electron cooler or ∼ 4 × 10 −4 after accelerated to 1000MeV/u without cooling. In order to improve the nuclear structure and heavy isotope research in SFC+SSC energy domain. A Wien filter was added in front of RIBLL and gas was filled in first section of RIBLL; a new spectrometry SHANS has being installed. Presently, there are two starting version experimental setups at CSR.

Electron ionization time‐of‐flight mass spectrometry: Historical review and current applications

This review presents an overview of electron ionization time-of-flight mass spectroscopy (EITOFMS), beginning with its early development to the employment of modern high-resolution electron ionization sources. The EITOFMS is demonstrated to be ideally suited for analytical and basic chemical physics studies. Studies of the formation of positive ions by electron ionization time-of-flight mass spectroscopy have been responsible for many of the known ionization potentials of molecules and radicals, as well as accepted bond dissociation energies for ions and neutral molecules. The application of TOFMS has been particularly important in the area of negative ion physics and chemistry. A wide variety of negative ion properties have been discovered and studied by using these methods including: autodetachment lifetimes, metastable dissociation, Rydberg electron transfer reactions and field detachment, SF(6) Scavenger method for detecting temporary negative ion states, and many others.

Heavy Ion Physics with the CMS Detector at LHC

CMS is a unique detector with large acceptance, nearly hermetic fine granularity hadronic and electromagnetic calorimetry and good muon and tracking systems. Therefore it is an exellent device for the study of quark-gluon plasma by means of hard probes: the quarkonium production and the medium-induced energy loss by light and heavy quarks (“jet quenching”) in various reaction channels of heavy ion collisions at LHC. The CMS apparatus allows adequate dimuon and jet reconstruction, high transverse momentum particle tracking (esp. for isolated muons and tracks in jets), as well as determination of the global characteristics of an event in the high multiplicity environment. One of important tools for studying the properties of nuclear matter under extreme conditions is the QCD jet production: jet quenching is very different in cold and hot medium, and hence results in many specific observable phenomena. At LHC, a new regime of heavy ion physics will be reached wherein hard and semi-hard particle production should dominate the background of soft processes and the higher gluon densities imply stronger energy loss to be observable in new channels.

Rutherford backscattering using electrons as projectiles: Underlying principles and possible applications

Ion beam analysis is the method of choice for studying the composition of layers with a thickness exceeding several tens of Å. Recently it has become clear that elastic scattering of keV electrons can be used to determine the surface composition of relatively thick layers (up to 1000Å) in a way very similar to ion scattering experiments. These electron-scattering experiments share much of the underlying physics of electron spectroscopy and ion scattering. In this paper we systematically describe the similarities and differences between the electron-scattering experiments and the ion-beam experiments and illustrate this description with relevant electron-scattering examples.

Afterglow mode and the new micropulsed beam mode applied to an electron cyclotron resonance ion source

An increasing number of experiments in the field of low energy ion physics (<25 keV/charge) requires pulsed beams of highly charged ions. Whereas for high-intensity beams (greater than microampere) a pulsed beam chopper, installed downstream to the analyzing dipole, is used. For low-intensity beams (<100 nA) the ion intensity delivered during the pulse may be increased by operating the electron cyclotron resonance discharge in the afterglow mode. This method gives satisfactory results (i.e., average current during the beam pulse is higher than the current in the cw mode) for high charge state ions. In this paper, we report on results of the afterglow mode for beams of (22)Ne(q+), (36)Ar(q+), and (84)Kr(q+) ions. Furthermore, a new promising "micropulsed beam" mode will be described with encouraging preliminary results for (84)Kr(27+) and (36)Ar(17+) ions.

Heavy Quark Diffusion in AdS/CFT

The purpose of this short note is to clarify how thermal noise arises within the context of AdS/CFT.∗) Recently the AdS/CFT correspondence has been used to calculate several items of great interest to the heavy ion physics community. This list includes: the drag of heavy quarks,1)–3) higher order hydrodynamics,4),5) and radiative processes.6) All of these processes are intrinsically related to noise in thermal field theory. However, noise does not appear naturally within the AdS/CFT context. This is essentially manifest since it is difficult to acquire stochastic terms by solving linearized classical equations of motion. However it turns out that the quantum mechanics of AdS5 produces the required thermal noise. To address the question of noise we will consider the simplest stochastic process — Brownian motion. General considerations of heavy quarks would indicate that the heavy quark should obey a Langevin equation of motion

Lattice QCD at finite temperature and density

QCD at finite temperature and density is becoming increasingly important for various experimental programmes, ranging from heavy ion physics to astro-particle physics. The non-perturbative nature of non-abelian quantum field theories at finite temperature leaves lattice QCD as the only tool by which we may hope to come to reliable predictions from first principles. This requires careful extrapolations to the thermodynamic, chiral and continuum limits in order to eliminate systematic effects introduced by the discretization procedure. After an introduction to lattice QCD at finite temperature and density, its possibilities and current systematic limitations, a review of present numerical results is given. In particular, plasma properties such as the equation of state, screening masses, static quark free energies and spectral functions are discussed, as well as the critical temperature and the QCD phase structure at zero and finite density.

Kinetic-ion simulations addressing whether ion trapping inflates stimulated Brillouin backscattering reflectivities

An investigation of the possible inflation of stimulated Brillouin backscattering (SBS) due to ion kinetic effects is presented using electromagnetic particle simulations and integrations of three-wave coupled-mode equations with linear and nonlinear models of the nonlinear ion physics. Electrostatic simulations of linear ion Landau damping in an ion acoustic wave, nonlinear reduction of damping due to ion trapping, and nonlinear frequency shifts due to ion trapping establish a baseline for modeling the electromagnetic SBS simulations. Systematic scans of the laser intensity have been undertaken with both one-dimensional particle simulations and coupled-mode-equations integrations, and two values of the electron-to-ion temperature ratio (to vary the linear ion Landau damping) are considered. Three of the four intensity scans have evidence of SBS inflation as determined by observing more reflectivity in the particle simulations than in the corresponding three-wave mode-coupling integrations with a linear ion-wave model, and the particle simulations show evidence of ion trapping.

The future of quark matter at RHIC

The planned collider upgrade and ongoing detector upgrades at RHICH will allow new access and statistical reach to physical observables in heavy ion collisions. We discuss the importance of these improved capabilities on the advancement of heavy ion physics. The RHIC II upgrade will provide a ten-fold luminosity improvement. The upgrades will allow more extensive beam species and energy scan studies. Calculations of the expected annual yields associated with measurements of heavy quark and jet production are presented. These calculations demonstrate a promising future in heavy quarkonia, high-pt direct photon, and jet studies at RHIC. Also shown is that through a combination of higher luminosities, longer running times, and lower backgrounds, RHIC II will be competitive with the LHC in many heavy ion measurements of interest.

Heavy ion physics at the LHC with the ATLAS detector

The ATLAS detector at CERN will provide a high-resolution longitudinally segmented calorimeter and precision tracking for the upcoming study of heavy ion collisions at the LHC ( GeV). The calorimeter covers |η| < 5 with both electromagnetic and hadronic sections, while the inner detector spectrometer covers |η| < 2.5. ATLAS will study a full range of observables necessary to characterize the hot and dense matter formed at the LHC. Global measurements (particle multiplicities, collective flow) will provide access into its thermodynamic and hydrodynamic properties. Measuring complete jets out to 100's of GeV will allow detailed studies of energy loss and its effect on jets. Quarkonia will provide a handle on deconfinement mechanisms. ATLAS will also study the structure of the nucleon and nucleus using forward physics probes and ultraperipheral collisions, both enabled by segmented zero degree calorimeters.

Plasma microturbulence simulation of instabilities at highly disparate scales

This work reports on studies of the multi-scale interaction between small-scale electron turbulence and large-scale ion turbulence in tokamak plasmas. Traditionally, the long-wavelength, low-frequency turbulence driven by ion-scale instabilities (ion-temperature-gradient and trapped-electron modes) is studied separately from the short-wavelength, high-frequency turbulence driven by electron-scale instabilities (electron-temperature-gradient modes). High-resolution, massively-parallel simulations have uncovered a number of physically-important discoveries. First, we find that a popular simplified model of ion physics previously used in studies of electron-scale turbulence can lead to nonphysical runaway of electron heat transport. We have shown that this nonphysical runaway is eliminated when correct long-wavelength ion physics is self-consistently included. We have also found that under normal conditions most of the electron heat transport arises from large-scale instabilities. However, when these large-scale instabilities are suppressed by plasma rotation or other processes, the electron instabilities survive and may dominate the loss of electron heat from the plasma. A further remarkable finding is that strong turbulence at long scales can act to reduce the intensity of turbulence at short scales. Simulations were carried out on the Cray X1E computer at ORNL, with the largest runs taking about a week on 720 multi-streaming processors.

Chapter 5: Physics of energetic ions

This chapter reviews the progress accomplished since the redaction of the first ITER Physics Basis (1999 Nucl. Fusion 39 2137–664) in the field of energetic ion physics and its possible impact on burning plasma regimes. New schemes to create energetic ions simulating the fusion-produced alphas are introduced, accessing experimental conditions of direct relevance for burning plasmas, in terms of the Alfvénic Mach number and of the normalised pressure gradient of the energetic ions, though orbit characteristics and size cannot always match those of ITER. Based on the experimental and theoretical knowledge of the effects of the toroidal magnetic field ripple on direct fast ion losses, ferritic inserts in ITER are expected to provide a significant reduction of ripple alpha losses in reversed shear configurations. The nonlinear fast ion interaction with kink and tearing modes is qualitatively understood, but quantitative predictions are missing, particularly for the stabilisation of sawteeth by fast particles that can trigger neoclassical tearing modes. A large database on the linear stability properties of the modes interacting with energetic ions, such as the Alfvén eigenmode has been constructed. Comparisons between theoretical predictions and experimental measurements of mode structures and drive/damping rates approach a satisfactory degree of consistency, though systematic measurements and theory comparisons of damping and drive of intermediate and high mode numbers, the most relevant for ITER, still need to be performed. The nonlinear behaviour of Alfvén eigenmodes close to marginal stability is well characterized theoretically and experimentally, which gives the opportunity to extract some information on the particle phase space distribution from the measured instability spectral features. Much less data exists for strongly unstable scenarios, characterised by nonlinear dynamical processes leading to energetic ion redistribution and losses, and identified in nonlinear numerical simulations of Alfvén eigenmodes and energetic particle modes. Comparisons with theoretical and numerical analyses are needed to assess the potential implications of these regimes on burning plasma scenarios, including in the presence of a large number of modes simultaneously driven unstable by the fast ions.

Differential Cross-Section Measurement for the 64Zn(n, α)61Ni Reaction at 5.03 and 5.95 MeV

Differential cross sections of the 64Zn(n,α)61Ni reaction were measured at neutron energies of 5.03 and 5.95 MeV by using a gridded ionization chamber. The experiment was performed at the 4.5-MV Van de Graaff accelerator of the Institute of Heavy Ion Physics, Peking University. Neutrons were produced through the D(d,n)3He reaction with a deuterium gas target. The absolute neutron flux was determined by the 238U(n,f) reaction and a calibrated BF3 long counter. Present results are compared with existing data.

The summary of researches on ADS in China

The conceptual study on the accelerator driven system (ADS) that lasted for about five years ended in 1999 in China. As one project of the National Basic Research Program of China (973 Program) in the energy domain, which is sponsored by the China Ministry of Science and Technology (MOST), a five-year-program of fundamental research of ADS physics and related technology was launched in 2000 and passed national review at the end of 2005. The China Institute of Atomic Energy (CIAE), the Institute of High Energy Physics (IHEP), the Institute of Heavy Ion Physics in Peking University (PKU-IHIP) and other institutions jointly carried out the research. The research activities were focused on HPPA physics and technology, reactor physics of external source driven sub-critical assembly, nuclear data base and material study. For HPPA, a high current injector consisting of an ECR ion source, LEBT and an RFQ accelerating structure of 3.5 MeV was built. In reactor physics study, a series of neutron multiplication experimental study has been carried out and still being done. The VENUS facility has been constructed as the basic experimental platform for neutronics study in ADS blanket. It’s a zero power sub-critical neutron multiplying assembly driven by external neutron produced by a pulsed neutron generator. The theoretical, experimental and simulation study on nuclear data, material properties and nuclear fuel circulation related to ADS is carrying on to provide the database for ADS system analysis. The main results on ADS related researches will be reported.

Correlated processes in negative ions

The goal of negative ion physics is to gain a better understanding of the role played by electron correlation in the structure and dynamics of many-electron systems. The talk will describe the use of accelerator-based methods to investigate the interaction between negative ions and electrons, with a focus on threshold behavior and di-anionic resonances.

Review on TPC's

The Time-Projection Chamber invented thirty years ago by David Nygren, has been used very successfully for tracking in many particle and ion physics experiments, and is now often developed for rare events physics. After a presentation of the original idea of the TPC, and of the advantages of such a detector, the problems related to its realisation will be developed, then a panorama of TPCs for particle physics will be shown, and finally a survey will be done on potentialities of TPC for rare event detection.