Energy Particle Beams Research Articles

NATALIE: A 32 detector integrated acquisition system to characterize laser produced energetic particles with nuclear techniques

We present a stand-alone system to characterize the high-energy particles emitted in the interaction of ultrahigh intensity laser pulses with matter. According to the laser and target characteristics, electrons or protons are produced with energies higher than a few mega electron volts. Selected material samples can, therefore, be activated via nuclear reactions. A multidetector, named NATALIE, has been developed to count the β(+) activity of these irradiated samples. The coincidence technique used, designed in an integrated system, results in very low background in the data, which is required for low activity measurements. It, therefore, allows a good precision on the nuclear activation yields of the produced radionuclides. The system allows high counting rates and online correction of the dead time. It also provides, online, a quick control of the experiment. Geant4 simulations are used at different steps of the data analysis to deduce, from the measured activities, the energy and angular distributions of the laser-induced particle beams. Two applications are presented to illustrate the characterization of electrons and protons.

New micro-cones targets can efficiently produce higher energy and lower divergence particle beams

AbstractSmall conical targets have been used in high intensity laser target interaction mostly in the context of fast ignition. We demonstrate that when cone targets are shaped appropriately and used with specific interaction conditions, they can produce particle beams of higher maximum energy and number in a lower angular divergence than flat targets. This is relevant to fast ignition, small compact particle beams, medical applications, focused ion and/or electron beam microscopes. This fact carries the potential to produce particle beams that are no longer limited by the characteristics of the laser. Note that for fast ignition, reducing the divergence of the beam lowers the energy requirement and enhances the energy deposition into the compressed fuel.

Modeling of Solar Flare Plasma and Its Radiation

We present a modular and highly versatile test particle-radiative hydrodynamic code which simultaneously models the particle beam energy transport and deposition, the corresponding explosive response of the flare atmosphere and the NLTE (NLTE, plasma and radiation out of the local thermodynamic equilibrium) radiative transfer for partly ionized hydrogen in the chromosphere and photosphere. The computational domain covers the photosphere, the chromosphere, the transition region, and the corona with the initial hydrostatic preflare atmosphere. To demonstrate the potential of the code, we calculate the time evolution of the Balmer line profiles corresponding to the time variation of the electron beam flux derived from the observed flare hard X-ray emission.

Examination of the species and beam energy dependence of particle spectra using Tsallis statistics

Tsallis statistics was used to investigate the non-Boltzmann distribution of particle spectra and their dependence on particle species and beam energy in the relativistic heavy-ion collisions at SPS and RHIC. Produced particles are assumed to acquire radial flow and be of non-extensive statistics at freeze-out. J/ψ, and the particles containing strangeness were examined separately to study their radial flow and freeze-out. We found that the strange hadrons approach equilibrium quickly from peripheral to central A+A collisions and they tend to decouple earlier from the system than the light hadrons but with the same final radial flow. These results provide an alternative picture of freeze-outs: a thermalized system is produced at the partonic phase; the hadronic scattering at a later stage is not enough to maintain the system in equilibrium and does not increase the radial flow of the copiously produced light hadrons. The J/ψ in Pb+Pb collisions at SPS is consistent with early decoupling and obtains little radial flow. The J/ψ spectra at RHIC are also inconsistent with the bulk flow profile.

Energy dissipation in insulators induced by swift heavy ions: A parameter study

AbstractThe irradiation of solids with high energy laser or particle beams has led to a deeper understanding of the relaxation processes inside the target material. However, a lot of open questions remain. In the present paper, we will examine the irradiation of the model system Xe23+ @ 93 MeV → SrTiO3 within the framework of the two-temperature-model and study the electron-phonon-coupling g and the electron diffusivity De as well as the lattice diffusivity Dp. These are crucial parameters for which no experimental data is available. Experimentally, g is very difficult to measure and therefore theoretical predictions are of great importance. With the approach presented here it is possible to determine the coupling-constant by one order of magnitude.

STIM evaluation in GeoPIXE to complement the quantitative dynamic analysis

The GeoPIXE software for quantitative PIXE trace element imaging and analysis is a well established package for evaluation of characteristic X-ray data for both PIXE and SXRF. For the case of microbeam applications on semi-thick samples knowledge of the local areal density distribution is important for precise quantification. A technique is reported to achieve this using the measurement of beam particle energy loss as it traverses the sample, as in scanning transmission ion microscopy (STIM). New functionality is added to the GeoPIXE code through integration of routines for STIM sorting of event-by-event data to create elemental maps of the mean energy after traversing the sample. Integration of stopping powers for a given sample matrix then permits the measured energy loss to be related to the local areal density. In a further step, this information is used for X-ray absorption corrections made directly to the PIXE analysis results. As a complement, user-written plugins operating on single STIM spectra have been used to compare the estimated areal density from chosen spots with the corresponding values calculated with the new GeoPIXE routines. The additions made to the code allow a more precise quantification to be done on inhomogeneous, semi-thick samples.

Energy conversion of the flare due to direct electric fields from the sheared reconnection

In this paper we present a new mechanism of the main energy conversion of the solar flare. Since a flare inducing prominence (flux tube) rises V z ⩽ 300 km s −1, the plasmas below it cannot continuously eject with Alfvén speeds of V A = 3000 km s −1 but probably with V z ≈ ±100 km s −1. Plasma up and downflows with V A will within a short duration be blocked between the chromosphere where reconnected flux tubes are piling up, and the slowly rising flux rope. Hence the Petschek slow shock mechanism is difficult to be realized as a major energy converting mechanism. Adopting a conventional reconnecting morphology, we assume a magnetic component parallel to the photospheric neutral line, i.e. sheared fields of B y ≠ 0. Then Gauss’s law leads to non-vanishing electric charges σ; 4π σ = −div( V × B / c) ≈ B y ∂ V z / c∂ x where the horizontal inflow velocity V x changes to vertical down-flow V z (e.g. B y ≈ B z = 40G and Δ x ≈ 10 4 km). Then the electric field parallel to the magnetic fields E ∥ calculated from Coulomb’s law from this σ is found to be far greater than the Dreicer field, and accelerates electrons and protons. Thus the horizontally inflowing Poynting energy flux in area S x is immediately converted to the kinetic energy of electron beams along the magnetic field in area S z ; B 2 V x S x / 4 π = 1 2 m e n beam V beam 3 S z with S x / S z ≈ 4. The particle beam energy flux cannot exceed the Poynting energy flux however large E ∥ may be. The total energy can be supplied by 10 keV electrons and n beam = 2 × 10 7 cm −3 for V x = 40 km s −1. This inflow velocity V x , though restricted by the rising prominence speed, explains the short flare duration consistent to observations. The electron beam flux n beam V beam will be simultaneously and co-spatially compensated by the slowly back-flowing bulk electrons, avoiding possible enormous charge pile-up. Instead of the conventional diffusion region, which contains serious difficulties if there is the shear as one should normally expect, we propose a reconnecting small region in the potential magnetic fields. The latter may be created by unwinding motions to erase the shear and to minimize energy, and the time scale is given only from the outside condition free from any diffusive processes such as the anomalous resistivity, because no electric currents may exist.

Measurement of Ion Energy Distribution in a Cylindrical Inertial Electrostatic Confinement Fusion (C-IECF) Device

In recent researches, an assisted glow discharge experiment using an external ion source has been tried to reduce operation gas pressure. As results, operating gas pressure has been successfully reduced from 1.5 Pa to 0.3 Pa, and the neutron production rate has increased.These results are considered to be due to an increase of ion energy. However, it is necessary to measure the ion energy distribution of the Cylindrical Inertial Electrostatic Confinement Fusion (C-IECF) device in order to confirm this. To do this, we have measured the distribution of the neutral particle beam energy (relative to ion energy distribution). These experimental results demonstrate that a decrease of operation gas pressure (from 1.7 Pa to 0.3 Pa) contributes to the increase in ion energy.

Characteristics of Charged Particle Production in Relativistic Heavy-Ion Collisions

Inclusive spectra of charged particles at midrapidity in Au+Au collisions at sqrt(s_NN) = 130 GeV and 200 GeV were measured with the STAR detector at RHIC. The measured mean transverse momentum shows a characteristic dependence on charged particle multiplicity and beam energy in Au+Au collisions that is distinctly different from pp, pbarp and ee collisions. A comparison with model predictions is discussed.

New cross-sections and intercomparison of proton monitor reactions on Ti, Ni and Cu

The excitation functions of proton induced reactions on Ti, Ni and Cu were studied using activation method on stacks made of thin metallic foil targets with natural isotopic composition. Since titanium, nickel and copper are ideal target material with respect to their availability, physical, mechanical and chemical properties the use of the nat Ti(p,x) 48 V, nat Ni(p,x) 57 Ni, nat Cu(p,x) 62 Zn, nat Cu(p,x) 63 Zn and nat Cu(p,x) 65 Zn processes are suitable for monitoring the intensity and/or energy of charged particle beams. These processes are recommended under 40 MeV bombarding proton energy as monitor reaction. The new data sets of these five processes were cross-checked with each other to provide reliable consistent numerical cross-sections. Results were compared to the recommended cross-section values reported recently by the International Atomic Energy Agency [IAEA TECDOC-1211, 2001].

Magnetization as a critical defining parameter for strand in precision dipole applications implications for field error and F-J stability

In hadron accelerators, between low energy particle injection and beam accumulation, the guiding dipoles are ramped at some rate dB/dt. Both at injection and during ramping the static and dynamic magnetizations of the magnet windings introduce multipolar distortions into the beam-line field. Dynamic magnetization, controllable by cable design, is estimated and used to provide a criterion against which to evaluate the allowable magnitude of static (persistent-current) magnetization, M, from a field-quality standpoint. The it is of NbTi and advanced Nb/sub 3/Sn conductors are compared and with regard to the latter the question of flux-jump stability is explored. A magnetization criterion for such stability is presented and compared to experiment. It is noted that since /spl Delta/M is proportional to critical current density, J/sub c/, and the strand's effective filament diameter, d/sub eff/, the latter has frequently been specified as a critical parameter, although it will need to be re-specified with every increase in J/sub c/. It is pointed out that although in the manufacture of MF Nb/sub 3/Sn composites d/sub eff/ will continue to be useful as a processing parameter in that it gauges the extent to which changes of processing conditions change the degree of interfilamentary bridging, and is measured by comparing the magnetic and transport-measured J/sub c/s, the most useful information is embodied in the results of the magnetization measurement alone.

Initial dual-sweep streak camera measurements on the Duke storage ring OK-4 UV/visible FEL

Initial measurements at the Duke storage ring free electron laser (FEL) of both spontaneous emission radiation (SER) from the OK-4 and FEL radiation outcoupled from the oscillator cavity have been done with a dual-sweep streak camera. In the SER case, ANL's Hamamatsu C5680 streak camera was used to characterize stored electron-beam bunch lengths versus rf gap voltage and single-bunch current. Electron-beam bunch lengths were observed in a range from 50 to 300 ps (FWHM). Particle beam energies of 270 and 500 MeV in the storage ring (SR) were used with the OK-4 to generate SER from 500 nm to less than 200 nm. Sensitivity to single-bunch, single-turn SER was shown down to ∼4 μA beam current at λ=450 nm. By operating in the synchroscan mode and at bunch currents less than 1 mA, beam orbit length vs. the resonator round-trip time was investigated by detecting the relative arrival time of the second pass outcoupled from the resonator at λ≈200 nm. These measurements were used in support of first lasing in the UV-visible regime in November 1996. The dual-sweep streak mode was then used to monitor lasing intensity variations on the 1 and 50 ms time scales, to measure a lasing pulse length as short as ∼3 ps ( σ) at λ=388 nm at low beam current, and to track the orbit length detuning curve.

Optical beam-energy modulators

Four devices are discussed. In each of these, electromagnetic waves of wavelength /spl lambda/ (which may be in the optical range) are to be used to modulate the energy of extreme relativistic charged particle beams on a scale of /spl gsim//spl lambda//2. The devices are: (1) two-wave modulators; the well-known optical klystron is a special case and has been used in the past for energy modulation. The other three are proposed as appropriate alternatives, depending on the circumstances: (2) vacuum modulator; it is the simplest in construction, and its energy modulation amplitude is essentially the function of only the power carried by the wave (e.g., laser power) and not the geometry nor /spl lambda/; (3) Cherenkov modulator; and (4) resonator energy modulator. Their capabilities, including the energy modulation amplitude, and efficiency, are compared.

Determination of the external beam energy of a variable energy. Multiparticle cyclotron

Optimization of commercial production of GBq batches of radioisotopes by threshold nuclear reactions needs an accurate knowledge of the particle beam energy. We present three independent techniques allowing energy determination with 2% accuracy for external beams of a multiparticle cyclotron with a positionable deflector used in isotope production. Stopping power analysis, activation analysis followed by comparison with monitor reaction cross-sections and direct time-of-flight (ToF) study of the particle velocity using a double beam pick-up set up allows us to conclude that only at the high energy end a discrepancy exists between real and calculated energy (maximal 4.5% for α-particles).

Conceptual design of a charged particle beam energy spectrometer utilizing transition radiation grating

A new technique of measuring the energy spectrum of a charged particle beam using optical transition radiation is presented in this paper. The charged particle beam energy spectrum can be studied by analyzing the optical spectrum of the optical transition radiation produced in a multi-foil configuration. This type of energy spectrometer can have a very large energy acceptance which can not be matched by a simple conventional magnetic dipole spectrometer. The theory of transition radiation from a single boundary and from a foil with finite thickness are reviewed. Multi-foil transition radiation theory and its application for charged particle beam energy spectrum measurement are presented. The practical issues which may affect the performance of a multi-foil transition radiation energy spectrometer are discussed.

Particle-induced X-ray emission: thick-target analysis of inorganic materials in the determination of light elements

Particle-induced X-ray emission (PIXE) has been applied to the analysis of inorganic materials to determine some elements with Z<27: Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe, in thick-target analysis. A PIXE method has been developed for the analysis of geological materials, ceramics and pottery. Work has been carried out with an ion beam analytical system, using a low particle beam energy. Relative sensitivity, detection limits, reproducibility and accuracy of the method were calculated based on the analysis of geological standard materials (river sediments, argillaceous limestone, basalt, diorite and granite). Analysis using PIXE offers a number of advantages, such as short analysis time, multi-elemental and non-destructive determinations, and the results are similar to those obtained with other instrumental techniques of analysis.

Time-resolved hard x-ray studies using third-generation synchrotron radiation sources (abstract)

The third-generation, high-brilliance, synchrotron radiation sources currently under construction will usher in a new era of x-ray research in the physical, chemical, and biological sciences. One of the most exciting areas of experimentation will be the extension of static x-ray scattering and diffraction techniques to the study of transient or time-evolving systems. The high repetition rate, short-pulse duration, high-brilliance, variable spectral bandwidth, and large particle beam energies of these sources make them ideal for hard x-ray, time-resolved studies. The primary focus of this presentation will be on the novel instrumentation required for time-resolved studies such as optics which can increase the flux on the sample or disperse the x-ray beam, detectors and electronics for parallel data collection, and methods for altering the natural time structure of the radiation. This work is supported by the U.S. Department of Energy, BES-Materials Science, under Contract No. W-31-109-ENG-38.

Charged particle beam energies measured by twisting an aluminum foil

A new method of remotely measuring a cyclotron's proton beam energy over the range of 10–45 MeV is described. Aluminum foils are placed in front of the beam to reduce the beam energy to about 2–4 MeV; then an aluminum foil, 0.030 inches thick, and an insulated Faraday plate (0.25 inch thick) are rotated in the beam path through an angle of 45°, and the beam current on the Faraday plate is measured as a function of the angle of rotation. A graph of beam current vs thickness of aluminum, is plotted and the beam energy is then calculated from these data points using tables of range vs energy.

Spectral evolution equation for the sideband instability in a free electron laser oscillator

Assuming that the light remains in the optical system while the electrons pass through and are lost, we have derived the evolution equation for an arbitrary optical spectrum in a free electron laser oscillator. The resulting integrodifferential equation includes the effects of linear system losses (due to either mirror reflectivity or clipping), the usual small signal gain term, and a quadratic nonlinear term that includes the effects of saturation and coupling to sideband modes. The effects of detuning and particle beam current and energy variations can easily be included. Results of numerical solutions of the equations for various conditions will be presented.

Evolution of the axial electron cyclotron maser instability, with applications to solar microwave spikes

The nonlinear evolution of cyclotron radiation from streaming and gyrating electrons in an external magnetic field is analyzed. The nonlinear dynamics of both the fields and the particles are treated fully relativistically and self-consistently. The model includes a background plasma and electrostatic effects. The analytical and numerical results show that a substantial portion of the beam particle energy can be converted to electromagnetic wave energy at frequencies far above the electron cyclotron frequency. In general, the excited radiation can propagate parallel to the magnetic field and, hence, escape gyrothermal absorption at higher cyclotron harmonics. The high-frequency Doppler-shifted cyclotron instability can have saturation efficiencies far higher than those associated with well-known instabilities of the electron cyclotron maser type. Although the analysis is general, the possibility of using this model to explain the intense radio emission observed from the sun is explored in detail.