Beam Energy Deposition Research Articles

A transmission matrix model for ion beam energy deposition in stack detectors

The accurate reconstruction of the energy deposition of finite-divergence wide energy spectrum ion beams in multi-material stack detectors calls for substantial computing resources. A transmission matrix model has been developed that uses statistical information extracted from a series of Monte Carlo simulations to build a fast, accurate and flexible algorithm for computing the energy loss of ions in complex heterogeneous detectors. In particular, the ion range and the broadening of the Bragg peak with increasing ion energy were correctly reproduced by the model.

Irradiation-induced quantum dot synthesis in insulators: ‘beam photography’

In latter years, many studies of ion beam-induced nanocluster (NC) formation in insulators have focussed on the effects of the ion beam interaction itself: defect formation, ion beam mixing, radiation-enhanced diffusion, etc. In a recent series of papers, we have taken an alternative approach that emphasizes the consequences of the beam's energy deposition as regards charge formation (electron, holes; defects as charge reservoirs; host and impurity atom ionization…) in matter. This leads to a parallel between photon and charged particle irradiations, and involves studies of the physicochemical, as well as the ‘purely physical’ effects of energy deposition.

GEANT4 simulation of electron energy deposition in extended media

The present work demonstrates that GEANT4 yields a consistent description of electron transport processes in semi-infinite homogeneous and heterogeneous extended media. This comparison covers the e − energy deposition profiles in a range of elements from aluminum to tantalum through molybdenum at source energies from 0.3 to 1.0 MeV and at incident angles from 0° to 60°. The good agreement between simulation results and data confirms that the Monte Carlo used code is capable of accurate electron beam energy deposition calculation even under such conditions.

Design, development, and testing of non-intercepting profile diagnostics for intense heavy ion beams using a capacitive pickup and beam induced gas fluorescence monitors

An intense and focused heavy ion beam is a suitable tool to generate high energy density in matter. To compare results with simulations it is essential to know beam parameters as intensity, longitudinal, and transversal profile at the focal plane. Since the beam's energy deposition will melt and evaporate even tungsten, non-intercepting diagnostics are required. Therefore a capacitive pickup with high resolution in both time and space was designed, built and tested at the high temperature experimental area at GSI. Additionally a beam induced fluorescence monitor was investigated for the synchrotron's (SIS-18) energy-regime (60–750 AMeV) and successfully tested in a beam-transfer-line.

Hard x-ray imaging for measuring laser absorption spatial profiles on the National Ignition Facility

Hard x-ray (“thin wall”) imaging will be employed on the National Ignition Facility (NIF) to spatially locate laser beam energy deposition regions on the hohlraum walls in indirect drive Inertial Confinement Fusion (ICF) experiments, relevant for ICF symmetry tuning. Based on time resolved imaging of the hard x ray emission of the laser spots, this method will be used to infer hohlraum wall motion due to x ray and laser ablation and any beam refraction caused by plasma density gradients. In optimizing this measurement, issues that have to be addressed are hard x-ray visibility during the entire ignition laser pulse with intensities ranging from 1013to1015W∕cm2, as well as simultaneous visibility of the inner and the outer laser drive cones. In this work we will compare the hard x-ray emission calculated by LASNEX and analytical modeling with thin wall imaging data recorded previously on Omega and during the first hohlraum experiments on NIF. Based on these calculations and comparisons the thin wall imaging will be optimized for ICF/NIF experiments.

Behavior of liquid lithium jet irradiated by 1 MeV electron beams up to 20 kW

Experiments were conducted to demonstrate the stable operation of the windowless liquid lithium target under extreme thermal loads that are equivalent to uranium beams from the proposed Rare Isotope Accelerator (RIA) driver linac. The cross section of the windowless liquid lithium target was 5mm×10mm and the velocity of the liquid lithium was varied up to 6m∕s. Thermal loads up to 20 kW within a beam spot of 1 mm in diameter were applied on the windowless liquid lithium target by 1 MeV electron beams. The maximum power density and total power deposited within the target was equivalent to that of a 200 kW, 400MeV∕u uranium beam. It was demonstrated that the windowless liquid lithium target flowing at as low as 1.8m∕s stably operates at a beam energy deposition up to 20 kW without disruption or excess vaporization.

Code OK2—A simulation code of ion-beam illumination on an arbitrary shape and structure target

For computer simulations on heavy ion beam (HIB) irradiation on a spherical fuel pellet in heavy ion fusion (HIF) the code OK1 was developed and presented in [Comput. Phys. Commun. 157 (2004) 160–172]. The new code OK2 is a modified upgraded computer program for more common purposes in research fields of medical treatment, material processing as well as HIF. OK2 provides computational capabilities of a three-dimensional ion beam energy deposition on a target with an arbitrary shape and structure. Program summary Title of program: OK2 Catalogue identifier: ADTZ Other versions of this program [1] : Title of the program: OK1 Catalogue identifier: ADST Program summary URL: http://cpc.cs.qub.as.uk/summaries/ADTZ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Computer: PC (Pentium 4, ∼1 GHz or more recommended) Operating system: Windows or UNIX Program language used: C++ Memory required to execute with typical data: 2048 MB No. of bits in a word: 32 No. of processors used: 1CPU Has the code been vectorized or parallelized: No No. of bytes in distributed program, including test data: 17 334 No of lines in distributed program, including test date: 1487 Distribution format: tar gzip file Nature of physical problem: In research areas of HIF (Heavy Ion Beam Inertial Fusion) energy [1–4] and medical material sciences [5], ion energy deposition profiles need to be evaluated and calculated precisely. Due to a favorable energy deposition behavior of ions in matter [1–4] it is expected that ion beams would be one of preferable candidates in various fields including HIF and material processing. Especially in HIF for a successful fuel ignition and a sufficient fusion energy release, a stringent requirement is imposed on the HIB irradiation non-uniformity, which should be less than a few percent [4,6,7]. In order to meet this requirement we need to evaluate the uniformity of a realistic HIB irradiation and energy deposition pattern. The HIB irradiation and non-uniformity evaluations are sophisticated and difficult to calculate analytically. Based on our code one can numerically obtain a three-dimensional profile of energy deposition onto an arbitrary shape and structure target. Method of solution: OK2 code works on the base of OK1 [1–9]. The code simulates a multi-beam illumination on a target with arbitrary shape and structure, and obtains the 3D energy deposition profile. Restrictions on the complexity of the problem: None Typical running time: The execution time depends on the pellet mesh number and the number of beams in the simulated illumination as well as on the beam characteristics (beam radius on the pellet surface, beam subdivision, projectile particle energy and so on). In almost of the practical running tests performed, the typical running time for one beam deposition is about 40 s on a PC with a CPU of Pentium 4, 2.4 GHz. Unusual features of the program: None

On the symmetry of cylindrical implosions driven by a rotating beam of fast ions

Cylindrical implosions driven by intense beams of heavy ions are one of the promising ways to create high energy density states in matter. To ensure the needed azimuthal symmetry of the beam energy deposition, it was proposed [Sharkov et al., Nucl. Instrum. Methods Phys. Res. A 464, 1 (2001)] to rotate the ion beam around the target axis. Combining analytical calculations with two-dimensional hydrodynamic simulations, a lower limit is established on the frequency ν of the beam rotation dictated by the target hydrodynamics. This limit is shown to be directly proportional to the desired radial convergence ratio Cr for stepwise beam power profiles, and to Cr1/2 for smooth pulses. With a smooth pulse, 6–10 beam revolutions per pulse should be sufficient to reach Cr≃30, while a stepwise pulse requires ≃100 revolutions. Also, the upper bound on the asymmetry of the elliptical focal spot of a rotating ion beam is calculated.

Determining the Spatial Structure of a High-Power Electron Beam Using Optical Radiation Emitted by a Beam Collector

A method for determining the spatial structure of a high-power relativistic electron beam is described. Using an absolutely calibrated CCD collector, the thermal-radiation brightness distribution of the beam-collector surface is registered in the visible and near-IR spectral regions and then converted into a spatial distribution of the beam energy deposition in a target. This method is applied at a high specific beam-energy flux (∼1 kJ/cm2), one which causes noticeable erosion of the beam collector.

Obtaining high pressures and metastable states in condensed media by using high-current relativistic electron beams

Experimental studies performed at the Russian Research Centre Kurchatov Institute on the interaction of high-current relativistic electron beams with various condensed media, including highly porous materials, are reviewed. The experiments on obtaining high pressures and accomplishing the structural and chemical conversions in the focal spot of a high-current beam are described. The principles of imitating an ultra-highspeed impact and other energetic actions on an obstacle with the help of high-current relativistic beams are discussed. The possibility of using such beams for surface modification is considered. Experimental data on the induced electric conductivity in highly porous SiO2 aerogels in the region of the beam energy deposition are presented.

Synthesizing single-phase β-FeSi 2 via ion beam irradiations of Fe/Si bilayers

This paper presents results on the direct synthesis of the β-FeSi 2 phase by ion beam mixing of Fe/Si bilayers with Xe ions. The influence of the substrate temperature, ion fluence and energy on the growth of this phase was investigated using Rutherford backscattering (RBS), X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS). Complete growth of single-phase β-FeSi 2 was achieved by 205 keV Xe ion irradiation to a fluence of 2×10 16 ions/ cm 2 at 600°C. We propose a two-step reaction mechanism involving thermal and ion beam energy deposition.

Deuteron beam interaction with lithium jet in a neutron source test facility

Testing and evaluating candidate fusion reactor materials in a high-flux, high-energy neutron environment are critical to the success and economic feasibility of a fusion device. The current understanding of materials behavior in fission-like environments and existing fusion facilities is insufficient to ensure the necessary performance of future fusion reactor components. An accelerator-based deuterium—lithium system to generate the required high neutron flux for material testing is considered to be the most promising approach in the near future. In this system, a high-energy (30–40 MeV) deuteron beam impinges on a high-speed (10–20 m/s) lithium jet to produce the high-energy (≥ 14 MeV) neutrons required to simulate a fusion environment via the Li (d, n) nuclear stripping reaction. Interaction of the high-energy deuteron beam and the subsequent response of the high-speed lithium jet are evaluated in detail. Deposition of the deuteron beam, jet-thermal hydraulic response, lithium-surface vaporization rate, and dynamic stability of the jet are modeled. It is found that lower beam kinetic energies produce higher surface temperature and consequently higher Li vaporization rates. Larger beam sizes significantly reduce both bulk and surface temperatures. Thermal expansion and dynamic velocities (normal to jet direction) due to beam energy deposition and momentum transfer are much lower than jet flow velocity and decrease substantially at lower beam current densities.

Calculation of the dose in the build-up region for high energy photon beam. Treatment planning when beam spoilers are employed

Recoil electrons from a polystyrene sheet (beam spoiler) placed in a photon beam were used to modulate the dose in the build-up region. The effects of the beam spoiler on the dosimetry in simple phantoms were studied for both 6 MV and 15 MV photon beams at 100 cm source-to-surface distance (SSD) as a function of (1) the thickness of the spoiler, (2) the spoiler-to-surface distance (SD) and (3) the field size. A radiotherapy treatment planning (RTP) algorithm was used that employs pencil beam dose deposition kernels to evaluate the three-dimensional (3D) dose distribution due to photons and electrons in the build-up region. To determine the energy deposition kernels for the recoil electrons emanating from the spoiler, their energy spectrum needs to be known. Monte Carlo simulations were performed to derive the spectrum of electrons from the beam spoiler. The recoil electron spectrum was found to be nearly independent of field size, SD, and spoiler thickness. The pencil beam energy deposition kernel was calculated for the recoil electrons from the spoiler and inserted in the treatment planning algorithm. The dose calculation algorithm permits merging the photon and recoil electron dose components. In all cases the calculation agrees to within 3% of the measured results.

'Squirrel-cage'-an effective configuration of REB injection

An effective system of REB injection has been proposed. The cylindrical N-pole magnetic wall formed by N conductors performs effective trapping of REB electrons of N band beams injected through the N cusps of multipole magnetic field. The proposed scheme of REB injection allows one to minimize beam losses and to reach a high efficiency of energy deposition into gas up to 90%. The desirable shape of beam energy deposition and plasma distribution can be realized by changing the number of magnetic poles and the value of magnetic field. The model of an effective source of argon plasma has been represented by using the Monte Carlo method in combination with a plasma kinetics simulation.

Calculation of the dose in the build-up region for high energy photon beam. Treatment planning when beam spoilers are employed

Recoil electrons from a polystyrene sheet (beam spoiler) placed in a photon beam were used to modulate the dose in the build-up region. The effects of the beam spoiler on the dosimetry in simple phantoms were studied for both 6 MV and 15 MV photon beams at 100 cm source-to-surface distance (SSD) as a function of (1) the thickness of the spoiler, (2) the spoiler-to-surface distance (SD) and (3) the field size. A radiotherapy treatment planning (RTP) algorithm was used that employs pencil beam dose deposition kernels to evaluate the three-dimensional (3D) dose distribution due to photons and electrons in the build-up region. To determine the energy deposition kernels for the recoil electrons emanating from the spoiler, their energy spectrum needs to be known. Monte Carlo simulations were performed to derive the spectrum of electrons from the beam spoiler. The recoil electron spectrum was found to be nearly independent of field size, SD, and spoiler thickness. The pencil beam energy deposition kernel was calculated for the recoil electrons from the spoiler and inserted in the treatment planning algorithm. The dose calculation algorithm permits merging the photon and recoil electron dose components. In all cases the calculation agrees to within 3% of the measured results.

Thermal Surface Treatment Using Intense, Pulsed Ion Beams

ABSTRACTSurface treatment experiments using intense pulsed ion beams have demonstrated new capabilities for materials surface treatment. These experiments have confirmed corrosion resistance, surface hardening, amorphous layer and nanocrystalline grain size formation, metal surface polishing, controlled melt of ceramic surfaces, surface cleaning and oxide layer removal by rapid melting and resolidification. Deposition of beam energy in a thin surface layer allows melting of the layer with relatively small energies (1-10 J/cm2) and allows rapid cooling (109-1010 K/sec) and resolidification of the melted layer by thermal diffusion into the underlying substrate. At higher intensities (≥20 J/cm2), this technology can provide rapid ablation of material from targets followed by rapid, congruent deposition of polycrystalline thin films on substrates. This technology uses high energy pulsed (40–400 ns) ion beams to directly deposit energy in the top 2–20 micrometers of the surface of materials.

Numerical simulation of vapor shielding and range shortening for ions impinging on a divertor during plasma disruptions

The behavior of divertor materials under the high heat load during a plasma disruption, a key problem in tokamak fusion technology, is studied at several laboratories under simulated plasma disruption conditions. Numerical modelling of the complex processes taking place at the divertor during a plasma disruption event was started recently at Kernforschungszentrum Karlsruhe. The aim of these activities is to determine the erosion rate of divertor material under different heat loads, to quantify the vapor shield effect and to give insight in the mechanisms of the beam target interaction. The simulation studies are performed with the Karlsruhe target code KATACO. This is a 1D plasma hydrodynamic code including beam energy deposition and multigroup radiation transport. First results for 10 and 100 keV proton beams with a power density of 5 and 50 MW/cm 2 respectively at a pulse duration of 100 μs show, that an equilibrium state at a plasma temperature of a few electron volt is reached shortly after the beginning of the disruption. A substantial part of the incoming energy is radiated back into the cavity.

A pencil beam model for photon dose calculation.

A method for photon dose calculation in radio therapy planning using pencil beam energy deposition kernels is presented. It is designed to meet the requirements of an algorithm for 3-D treatment planning that is general enough to handle irregularly shaped radiation fields incident on a heterogeneous patient. It is point oriented and thus faster than a full 3-D convolution algorithm and uses the same physical data base to characterize a clinical beam as a full 3-D convolution algorithm. It is shown that photon therapy beams can be characterized with great accuracy from a combination of precalculated Monte Carlo energy deposition kernels and dose distributions measured in a water phantom. The data are used to derive analytical pencil beam kernels that are approximately partitionated into the dose from (i) primary released electrons and positrons, (ii) scattered, bremsstrahlung, and annihilation photons, (iii) contaminating photons, and (iv) charged particles from the collimator head. A semianalytical integration method, based on triangulation of the field, is developed for dose calculation using the analytical kernels. Dose is calculated in units normalized to the incident energy fluence which facilitates output factor calculation. For application in heterogeneous media, a scatter correction factor is derived using monodirectional convolution along the ray path. In homogeneous media results are compared with measurements and in heterogeneous media with Monte Carlo calculations and the Batho method.

Numerical Investigations of Electron Beam Energy Deposition into the Gas Medium of an Excimer Laser

"Numerical Investigations of Electron Beam Energy Deposition into the Gas Medium of an Excimer Laser." Fusion Technology, 20(2), p. 258This article refers to:An Angle-Dependent Albedo for Fast-Neutron-Reflection Calculations

Acquisition of the effective lateral energy fluence distribution for photon beam dose calculations by convolution models

A method is described for acquiring the lateral energy fluence distribution of therapeutic photon beams. The method is designed for characterization of clinical accelerators for the convolution/superposition methods of photon dose calculations. Radial dose profiles, measured in a water phantom at a reference depth for the largest field size of the machine, are used to construct a discrete Cartesian dose matrix. A corresponding pencil beam energy deposition kernel is calculated from a database of Monte Carlo calculated kernels for monoenergetic photons by using the energy bin data of an effective spectrum as weights. The lateral kernel distribution at the depth of measurement is filtered and resampled into a discrete matrix, similar to that of the measured dose distribution. The dose matrix is then deconvolved by the kernel matrix, using fast Fourier transforms and Wiener filtering, to yield the effective energy fluence distribution. The method is tested by using the acquired energy fluence for convolution dose calculations and comparing the result with measured dose distributions.