Ion Physics Research Articles

Theoretical analysis of a new extraction system for a DUHOCAMIS operating in a high magnetic field

A new extraction system is designed for a penning ion source DUHOCAMIS (dual hollow cathode ion source for metal ion beams) being installed at the Institute of Heavy Ion Physics, Peking University. We have analyzed theoretically the central particle trajectories in the extraction region for ions having different q/m ratios and then compared our results with the simulation results of CST (Computer Simulation Technology) software. The validity of the system is verified and some analytical formulas are obtained which will be used for the optimization of the extraction system as well as the experimental setup.

Imaging key aspects of fast ion physics in the DIII-D tokamak

Visible imaging has been used to provide the 2D spatial structure and temporal evolution of the profile of high-energy neutrals introduced by neutral beam injection, the fast ion profile and a variety of plasma instabilities in DIII-D plasmas; the combination of these techniques form a comprehensive fast ion physics diagnostic suite. The injected neutral profile is imaged in Doppler shifted Dα light induced by collisional excitation. Fast ion profile information was obtained through imaging of Doppler shifted fast ion Dα light (FIDA) emitted by re-neutralized energetic ions. Imaging of FIDA emission during sawtooth events shows a large central depletion following sawtooth crashes—indicative of a broad redistribution of fast ions. Two examples of instability structure measurements are given. Measurements of the detailed 2D poloidal structure of rotating tearing modes were obtained using spectrally filtered fast imaging of broadband visible bremsstrahlung emission, a method which is capable of imaging with high resolution the structure of coherent oscillations in the core of current and next-step fusion plasma experiments and can be applied to virtually any mode with a finite perturbed bremsstrahlung emissivity and frequency in the laboratory frame. Measurements are also presented of the n = 0 energetic particle geodesic acoustic mode which were made by observing fluctuations in active emission.

Development of a preparation system for the radiocarbon analysis of organic carbon in carbonaceous aerosols in China

Carbonaceous aerosols comprising a large fraction of elemental carbon (EC) and organic carbon (OC) are considered to affect both global climate and human health. Radiocarbon measurements have been proved to be a useful isotopic tracer for distinguishing contemporary and fossil emissions. An optimized system of a two-step thermal preparation system for radiocarbon ( 14C) measurement of OC/TC is firstly established in China. In this system, OC/TC are converted into carbon dioxide under a pure oxygen flow at 340 °C/650 °C and then reduced to graphite for AMS target using the method of zinc reduction. Afterwards, radiocarbon measurements of the targets performed by the NEC Compact AMS System at the Institute of Heavy Ion Physics, Peking University. The measured results for estimated reference martial including HOx I, HOx II and IAEA-C6 are consistent with internationally accepted values. The radiocarbon-based source appointment of carbonaceous aerosols in China would be much more convenient and faster with the preparation system developed in this work.

Recording and analysis of electrically evoked compound action potentials (ECAPs) with MED-EL cochlear implants and different artifact reduction strategies in Matlab

Electrically evoked compound action potentials (ECAPs) are used in auditory research to evaluate the response of the auditory nerve to electrical stimulation. Animal preparations are typically used for the recording. With the introduction of a new generation of cochlear implants, however it is possible to record the response of the auditory nerve to electrical stimulation in humans as well, which is used in the clinic to test whether the implant works properly and whether the auditory nerve is responsive. Currently, ECAPs are used to estimate thresholds for speech processor programs. In addition, ECAPs recordings allow new research to be addressed, e.g., to evaluate enhanced electrical stimulation patterns. Research platforms are required to test user-defined stimuli and algorithms for the ECAPs analysis. Clinical fitting software that records ECAPs is not flexible enough for this purpose. To enable a larger group of scientists to pursue research in this field, we introduce a flexible setup that allows to change stimulation and recording parameters. ECAP recording and analysis software was developed in Matlab (The Mathworks, Inc.) for standard PC, using a National instruments (PCI-6533, National Instruments, Austin, TX) card and a Research Interface Box 2 (RIB2, Department of Ion Physics and Applied Physics at the University of Innsbruck, Innsbruck, Austria) for MED-EL cochlear implants. ECAP recordings of a human subject with three different artifact reduction methods (alternating, Miller modified masker-probe, triphasic pulses) are presented and compared.

First results and analysis of collective Thomson scattering (CTS) fast ion distribution measurements on ASDEX Upgrade

Experimental knowledge of the fast ion physics in magnetically confined plasmas is essential. The collective Thomson scattering (CTS) diagnostic is capable of measuring localized 1D ion velocity distributions and anisotropies dependent on the angle to the magnetic field. The CTS installed at ASDEX-Upgrade (AUG) uses mm-waves generated by the 1 MW dual frequency gyrotron. The successful commissioning the CTS at AUG enabled first scattering experiments and the consequent milestone of first fast ion distribution measurements on AUG presented in this paper. The first fast ion distribution results have already uncovered some physics of confined fast ions at the plasma centre with off-axis neutral beam heating. However, CTS experiments on AUG H-mode plasmas have also uncovered some unexpected signals not related to scattering that required additional analysis and treatment of the data. These secondary emission signals are generated from the plasma-gyrotron interaction therefore contain additional physics. Despite their existence that complicate the fast ion analysis, they do not prevent the diagnostic's capability to infer the fast ion distribution function on AUG.

Heavy ion physics for high density QCD with the CMS detector at the LHC

The main goal of the heavy ion physics programs at high energy colliders is to produce hot and dense partonic matter for studying quantum chromodynamics (QCD) under extreme conditions. The Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider (LHC) can measure various soft and hard probes with high accuracy. We present various unique features of the CMS detector as they relate to the exploration of high density QCD in heavy ion collisions.

DIRAC: A new version of computer algebra tools for studying the properties and behavior of hydrogen-like ions

During recent years, the Dirac package has proved to be an efficient tool for studying the structural properties and dynamic behavior of hydrogen-like ions. Originally designed as a set of Maple procedures, this package provides interactive access to the wave and Green's functions in the non-relativistic and relativistic frameworks and supports analytical evaluation of a large number of radial integrals that are required for the construction of transition amplitudes and interaction cross sections. We provide here a new version of the Dirac program which is developed within the framework of Mathematica (version 6.0). This new version aims to cater to a wider community of researchers that use the Mathematica platform and to take advantage of the generally faster processing times therein. Moreover, the addition of new procedures, a more convenient and detailed help system, as well as source code revisions to overcome identified shortcomings should ensure expanded use of the new Dirac program over its predecessor.

Gyrokinetic simulations of spherical tokamaks

This paper reviews transport and confinement in spherical tokamaks (STs) and our current physics understanding of this that is partly based on gyrokinetic simulations. Equilibrium flow shear plays an important role, and we show how this is consistently included in the gyrokinetic framework for flows that greatly exceed the diamagnetic velocity. The key geometry factors that influence the effectiveness of turbulence suppression by flow shear are discussed, and we show that toroidal equilibrium flow shear can sometimes entirely suppress ion scale turbulence in today's STs. Advanced nonlinear simulations of electron temperature gradient (ETG) driven turbulence, including kinetic ion physics, collisions and equilibrium flow shear, support the model that ETG turbulence can explain electron heat transport in many ST discharges.

Puzzles, Progress, Prospects: pre-Summary for the Quark Matter 2009 Conference

The new millennium's qualitative advances in relativistic heavy ion physics are in part due to, and are in part causing, a new appreciation for quantitative rigor in both experimental and theoretical work in the field. In these proceedings for the conference-opening “pre-Summary” talk I present an annotated guide to the figures and points made in my talk [ http://qm09.phys.utk.edu/indico/getFile.py/access?contribId=491&sessionId=25&resId=0&materialId=slides&confId=1].

Heavy Ion Physics with CMS

We present the capabilities of the CMS experiment to explore the heavy-ion physics program offered by the CERN Large Hadron Collider (LHC). The prime goal of this research is to test the fundamental theory of the strong interaction (QCD) in extreme conditions of temperature, density and parton momentum fraction by colliding nuclei at energies of s N N = 5.5 TeV . This presentation will give the overview of the potential of the CMS to carry out a full set of representative Pb-Pb measurements both in “soft” and “hard” regimes. Measurements include “bulk” observables – charged hadron multiplicity, low p T inclusive hadron identified spectra and elliptic flow – which provide information on the collective properties of the system; as well as perturbative processes – such as quarkonia, heavy-quarks, jets, γ-jet, and high p T hadrons — which yield “tomographic” information of the hottest and densest phases of the reaction.

Shock Treatment: Heavy Quark Energy Loss in a Novel AdS/CFT Geometry

We first note the failures of traditional pQCD techniques as applied to high- p T heavy ion physics and the suggestion of examining the double ratio of charm to bottom nuclear modification factors to generically distinguish between these weak coupling ideas and the strong coupling ideas of AdS/CFT. In order to gain confidence in the use of AdS/CFT (and to increase the likelihood of falsifying it and/or pQCD) we extend its application to heavy quark energy loss in both thermal and nonthermal media by calculating the string drag in a shock metric.

Tutorial: Exact Solutions for the Populations of the n-level Ion

ABSTRACTThis tutorial presents a review of the analytical approach to obtain exact solutions for the populations of n-level ions, and summarizes the ideas behind detailed balance and the statistical physics of collisionally-excited ions. Seaton’s analytical solution for the populations of the 3-level ion has been supplanted by matrix methods such as the master equation approach, which are now central to astronomy since there is a need to maintain a parity between improvements in quantum-mechanically calculated values for collision strengths and transition probabilities on the one hand, and three-dimensional (3D) photoionization codes used by astrophysicists for producing nebular diagnostics on the other. We show that the analytical method of solution to the problem using matrices and symbolic mathematics is straightforward, and we illustrate through theoretical, numerical, and empirical checks the validity of its results. First, we recast the equations of thermal statistical equilibrium for the energy level populations of collisionally-excited ions in the form of a well-defined matrix equation. We then show how symbolic mathematics is efficient in the inversion of equations and is able to provide the exact analytical solutions for the sought-after level populations. We present the matrices for the 5-level ion as an example of how to extend the exact solution for the 3-level ion to illustrate the general technique. We then show how the analytical results faithfully reduce to the Seaton solution when appropriate limits are taken. Spectrophotometric observations of a real ionized gas (the planetary nebula A39) are then used to obtain empirical values of forbidden line ratios and level populations for the 5-level [O III] ion. These values are compared with: (1) a best-fit 3D Monte Carlo photoionization model, and (2) the exact solution for the 5-level ion, using the symbolic mathematics approach, the exact Seaton 3-level ion solution, and a numerical approximation for the 5-level ion. It is shown that in every case, the analytical solution agrees with results obtained using observed nebular conditions to within the standard error. We provide a MATLAB code that can be adapted and tailored by astrophysicists to calculations of other n-level ions.

Antenna design for fast ion collective Thomson scattering diagnostic for the international thermonuclear experimental reactor

Fast ion physics will play an important role for the international thermonuclear experimental reactor (ITER), where confined alpha particles will affect and be affected by plasma dynamics and thereby have impacts on the overall confinement. A fast ion collective Thomson scattering (CTS) diagnostic using gyrotrons operated at 60 GHz will meet the requirements for spatially and temporally resolved measurements of the velocity distributions of confined fast alphas in ITER by evaluating the scattered radiation (CTS signal). While a receiver antenna on the low field side of the tokamak, resolving near perpendicular (to the magnetic field) velocity components, has been enabled, an additional antenna on the high field side (HFS) would enable measurements of near parallel (to the magnetic field) velocity components. A compact design solution for the proposed mirror system on the HFS is presented. The HFS CTS antenna is located behind the blankets and views the plasma through the gap between two blanket modules. The viewing gap has been modified to dimensions 30x500 mm(2) to optimize the CTS signal. A 1:1 mock-up of the HFS mirror system was built. Measurements of the beam characteristics for millimeter-waves at 60 GHz used in the mock-up agree well with the modeling.

From nuclear physics to semiconductor manufacturing: the making of ion implantation

This article examines the emergence of ion implantation as a major semiconductor manufacturing process from the early 1960s through the late 1970s. Ion implantation techniques originated in nuclear physics research and were first employed to make solar cells for military satellites at the Ion Physics Corporation (IPC). This work at IPC inspired a research group at Sprague Electric to use ion implantation techniques to make transistors. Sprague's process development work, and its key finding that ion implantation enabled the control of critical transistor characteristics, were both exploited by Mostek, a semiconductor start‐up funded by Sprague. Mostek's engineers incorporated ion implantation into their manufacturing process to produce a string of integrated circuits that other firms could not make. Mostek's market success encouraged semiconductor firms to embrace ion implantation in the early and mid 1970s. By the end of the decade, ion implantation was used in the manufacture of virtually all advanced integrated circuits. This article improves our understanding of the development and adoption of semiconductor, and more generally high technology, manufacturing processes. It also advances our knowledge of the ways in which new technologies developed in the Cold War context made their way into the manufacturing economy.

Highlights of strangeness physics at FAIR

The project of the international Facility for Antiproton and Ion Research (FAIR), co-located to the GSI facility in Darmstadt, has been officially started on November 7, 2007. An investment of about 1 billion Euros will permit new physics programs in the areas of low and medium energy antiproton research, heavy ion physics complementary to LHC, as well as in nuclear structure and astrophysics. The facility will comprise about a dozen accelerators and storage rings, which will enable simultaneous operations of up to four different beams. Some experiments concerning strangeness will be highlighted in this report.

Hot and dense matter: from RHIC to LHC – Theoretical overview

Relativistic heavy ion physics studies the phenomena that occur when a very large amount of energy (in units of QCD scale Λ QCD ) is deposited into a large volume (in units of Λ QCD − 3 ), creating an extended in space and time domain with an energy density that is large in units of Λ QCD 4 . This includes the mechanism by which the energy is deposited (likely a transformation of the colliding Lorentz-contracted “gluon walls” into the strong longitudinal color fields); approach to thermalization; and the static and dynamical properties of the created quark-gluon plasma. Of particular interest is the fate of symmetries (e.g. chiral SU L ( 3 ) × SU R ( 3 ) , scale, and discrete P and CP invariances) in hot and dense QCD matter. At present, the program at RHIC has entered a stage where new discoveries are enabled by high precision of the measurements; moreover, an array of new capabilities will soon be available due to the numerous and significant upgrades. Very importantly, we will soon have access to unprecedented energies of colliding ions at the LHC. In addition, future RHIC runs at low energies, FAIR at GSI and NICA at JINR will make possible the studies of QCD matter at high baryon density. I will describe the current status of theoretical knowledge about hot QCD, and the ways in which it may be expected to improve in the near future.

COLLECTIVE FLOW IN HEAVY-ION COLLISIONS FOR Eb=0.25-1.15GeV/NUCLEON

The study of the various collective flows of nuclear matter is one of the main subjects in heavy ion physics. The interest in collective nuclear motion under extreme conditions, like high density and/or high temperature originates from the equation of state (EOS) of nuclear matter. We investigate the collective transverse flow in heavy ion collisions at incident energies of 0.25 A GeV to 1.15 A GeV for Au + Au system within the quantum molecular dynamical (QMD) model. Some preliminary results are given and discussed.

ALICE-PHOS: acceptance and efficiency correction factors p−p→π 0+X at 10 TeV

In ultra-relativistic Heavy-Ion Collisions (HIC), the properties of the quark gluon plasma (QGP) can be explored, in particular, via measurements of neutral pions. The π0 is an important probe for both proton and heavy ion physics. In the former case, π0 production provides an important mean of testing pQCD as well as useful data to constrain current and future theoretical models. In the latter case, π0 measurements will serve as a baseline for exploring the nature of the HIC hard scattering. In the ALICE experiment, π0 mesons are identified as they decay into two photons (π0→γγ) using the high-resolution photon spectrometer (PHOS). PHOS will measure π0 transverse momentum over a wide range, from hundreds of MeV/c to several tens of GeV/c. An estimation of π0 production cross-section in proton–proton collisions is calculated in a next-to-leading order (NLO) approximation and first presented. The π0 geometrical acceptance and the identification efficiency along with the analysis on the invariant mass are the two important correction factors for obtaining a realistic π0 spectrum discussed in this paper.

Applicability of causal dissipative hydrodynamics to relativistic heavy ion collisions

We utilize nonequilibrium covariant transport theory to determine the region of validity of causal Israel-Stewart (IS) dissipative hydrodynamics and Navier-Stokes (NS) theory for relativistic heavy ion physics applications. A massless ideal gas with $2\ensuremath{\rightarrow}2$ interactions is considered in a Bjorken scenario in 0 + 1 dimension (D) appropriate for the early longitudinal expansion stage of the collision. In the scale-invariant case of a constant shear viscosity to entropy density ratio $\ensuremath{\eta}/s\ensuremath{\approx}\mathrm{const}$, we find that IS theory is accurate within 10% in calculating dissipative effects if initially the expansion time scale exceeds half the transport mean free path ${\ensuremath{\tau}}_{0}/{\ensuremath{\lambda}}_{\mathrm{tr},0}\ensuremath{\gtrsim}2$. The same accuracy with NS requires three times larger ${\ensuremath{\tau}}_{0}/{\ensuremath{\lambda}}_{\mathrm{tr},0}\ensuremath{\gtrsim}6$. For dynamics driven by a constant cross section, on the other hand, about 50% larger ${\ensuremath{\tau}}_{0}/{\ensuremath{\lambda}}_{\mathrm{tr},0}\ensuremath{\gtrsim}3$ (IS) and 9 (NS) are needed. For typical applications at energies currently available at the BNL Relativistic Heavy Ion Collider (RHIC), i.e., $\sqrt{{s}_{\mathit{NN}}}~100\text{\ensuremath{-}}200$ GeV, these limits imply that even the IS approach becomes marginal when $\ensuremath{\eta}/s\ensuremath{\gtrsim}0.15$. In addition, we find that the ``naive'' approximation to IS theory, which neglects products of gradients and dissipative quantities, has an even smaller range of applicability than Navier-Stokes. We also obtain analytic IS and NS solutions in 0 + 1D, and present further tests for numerical dissipative hydrodynamics codes in 1 + 1, 2 + 1, and 3 + 1D based on generalized conservation laws.

Strangeness at the international Facility for Antiproton and Ion Research

The project of the international Facility for Antiproton and Ion Research (FAIR), co-located to the GSI facility in Darmstadt, was officially started on November 7, 2007. An investment of about 1 billion euro will permit new physics programs in the areas of low and medium energy antiproton research, heavy ion physics complementary to LHC, as well as in nuclear structure and astrophysics. The facility will comprise about a dozen accelerators and storage rings, which will enable simultaneous operations of up to four different beams.