Optimum Beam Energy Research Articles

Optimize Electron Beam Energy toward In Situ Imaging of Thick Frozen Bio-Samples with Nanometer Resolution Using MeV-STEM.

To optimize electron energy for in situ imaging of large biological samples up to 10 μm in thickness with nanoscale resolutions, we implemented an analytical model based on elastic and inelastic characteristic angles. This model has been benchmarked by Monte Carlo simulations and can be used to predict the transverse beam size broadening as a function of electron energy while the probe beam traverses through the sample. As a result, the optimal choice of the electron beam energy can be realized. In addition, the impact of the dose-limited resolution was analysed. While the sample thickness is less than 10 μm, there exists an optimal electron beam energy below 10 MeV regarding a specific sample thickness. However, for samples thicker than 10 μm, the optimal beam energy is 10 MeV or higher depending on the sample thickness, and the ultimate resolution could become worse with the increase in the sample thickness. Moreover, a MeV-STEM column based on a two-stage lens system can be applied to reduce the beam size from one micron at aperture to one nanometre at the sample with the energy tuning range from 3 to 10 MeV. In conjunction with the state-of-the-art ultralow emittance electron source that we recently implemented, the maximum size of an electron beam when it traverses through an up to 10 μm thick bio-sample can be kept less than 10 nm. This is a critical step toward the in situ imaging of large, thick biological samples with nanometer resolution.

Scanning with Laser Beam over the TiO2 Nanotubes Covered with Thin Chromium Layers towards the Activation of the Material under the Visible Light.

This work presents pulsed UV laser treatment (355 nm, 2 Hz) of TiO2 nanotubes decorated with chromium oxides. The modification was performed in a system equipped with a beam homogenizer, and during the irradiation, the samples were mounted onto the moving motorized table. In such a system, both precisely selected areas and any large area of the sample can be modified. Photoelectrochemical tests revealed photoresponse of laser-treated samples up to 1.37- and 18-fold under the illumination with ultraviolet-visible and visible light, respectively, in comparison to bare titania. Optimal beam energy fluence regarding sample photoresponse has been established. Scanning electron microscopy images, X-ray diffraction patterns, along with Raman and X-ray photoelectron spectra, suggest that the enhanced photoresponse results from changes solely induced in the layer of chromium oxides. It is believed that the results of the present work will contribute to a wider interest in laser modification of semiconductors exhibiting improved photoelectrochemical activity.

α decay of the new isotope 204Ac

A new proton-unbound isotope 204Ac was produced in the fusion-evaporation reaction Tm(40169Ca,5n)204Ac and identified via the recoil-α correlation at the gas-filled recoiled separators SHANS2 and SHANS. The excitation function for producing 204Ac was measured and the optimal beam energy was evaluated to be 212 MeV. Nineteen ER - α1 - α2 - α3 decay chains were observed for this isotope. Based on these chains, the α-particle energy and half-life of 204Ac were determined to be 7948(15) keV and 7.4−1.4+2.2 ms, respectively. Both are consistent with the theoretical prediction. The reduced α-decay width was deduced to be 49−15+10 keV, which indicates a favored α decay for 204Ac. In addition, more precise decay properties of Eα = 7883(15) keV and T1/2 = 7.7−1.6+2.7 ms were obtained for 205Ac.

Production of neutron-rich heavy nuclei around $$N = 162$$ in multinucleon transfer reactions

Within the framework of the dinuclear system model, the production mechanism of neutron-rich heavy nuclei around \(N = 162\) has been investigated systematically. The isotopic yields in the multinucleon transfer reaction of \(^{238}\)U + \(^{248}\)Cm are analyzed and compared with the available experimental data at GSI. Systematics on the production of superheavy nuclei via the collisions of \(^{238}\)U on actinide nuclides \(^{252,254}\)Cf, \(^{254}\)Es and \(^{257}\)Fm is investigated thoroughly. It is found that the shell effect is of importance in the formation of neutron-rich nuclei around \(N~=~162\) owing to the enhancement of fission barrier and neutron separation energy. The fragments in the multinucleon transfer reactions manifest the broad isotopic distribution and are dependent on the beam energy. The polar angles of the fragments tend to the forward emission with increasing the beam energy. The production cross sections of new isotopes are estimated and the heavier targets are available for the neutron-rich superheavy nucleus formation. The optimal reaction system and beam energy are proposed for the future experimental measurements.

Further investigation of lung tumour peripheral doses using normoxic polymer gel dosimetry techniques

This work builds upon previous investigations of lung tumour peripheral doses for 6 MV, 6 MV FFF, and 10 MV FFF conformal arc therapy beams calculated in the Monaco® TPS and delivered using an Elekta® Agility™ linac. An improved patient lung phantom is developed with measurements using the normoxic PAG gel dosimeter and compared against dose planes from the TPS. The gel dosimeter measurements indicate that the TPS is overestimating the secondary build-up in the lung tumour peripheral region. It has been determined that in lung tumours, 6 MV FFF is the optimal beam energy for peripheral dose coverage and that there is a dosimetric compromise using 10 MV FFF.

Production cross-section calculations of 111In via proton and alpha-induced nuclear reactions

[Formula: see text], a known gamma emitter, is used for many medical purposes such as imaging of myocardial metastases. It can be produced by using different nuclear reactions. In this study, the reactions of [Formula: see text]Ag([Formula: see text]2n)[Formula: see text], [Formula: see text](p,[Formula: see text]n)[Formula: see text], [Formula: see text](p,[Formula: see text]2n)[Formula: see text], [Formula: see text](p,[Formula: see text]3n)[Formula: see text] and [Formula: see text](p,[Formula: see text]4n)[Formula: see text], which are the production routes of [Formula: see text], were investigated. Production cross-section calculations were performed by using equilibrium and pre-equilibrium models of TALYS 1.95 and EMPIRE 3.2 nuclear reaction codes. Hauser–Feshbach Model was appointed in both codes for calculations of equilibrium approximations. Exciton and Hybrid Monte Carlo Simulation (HMS) models were used in the EMPIRE 3.2, whereas Two-Component Exciton and Geometry Dependent Hybrid Model, which is implemented to TALYS code, has been used in the TALYS 1.95 for pre-equilibrium reactions. Also, a weighting matrix of the nuclear models was obtained by using statistical variance analysis. The optimum beam energy to obtain [Formula: see text] has been determined by using the results obtained from this weighting matrix.

Efficiency enhancement of RF-linac based free electron laser oscillator with electron beam energy ramping

Free electron laser (FEL) oscillator is a very effective method to produce the tunable and high-intense laser in the infrared and terahertz regions. However, in an FEL oscillator, normally only a small portion of the electron beam’s kinetic energy is converted into the optical field. Inspired by the earlier work on the Israeli EA FEL, in this paper we investigate increasing the efficiency of RF-linac based FEL oscillators through ramping up the electron beam energy moderately in the post-saturation regime. Based on theoretical analysis, the optimal beam energy ramping amplitude and the possible maximum efficiency enhancement are presented. Three-dimension simulations with the FELiChEM parameters show that, through ramping the electron energy from the saturation point by 1.9% and 2.68% for the FEL wavelengths of 10μm and 30μm, respectively, about 3.6 and 9.1 times enhancements of the FEL efficiency at the new saturation are achieved. The simulation results are consistent with the analytical prediction. This scheme may also benefit the x-ray FEL oscillators.

Determination of dose enhancement caused by AuNPs with Xoft® Axxent® Electronic (eBx™) and conventional brachytherapy: in vitro study.

PurposeThe purpose of this study was to determine dose enhancement (DE) and the possible clinical benefits associated with the inclusion of gold nanoparticles (AuNPs) in cancer cells irradiated by either an 192Ir brachytherapy source or a Xoft® Axxent® Electronic (eBx™) Brachytherapy.Patients and methodsBrachytherapy DE caused by AuNPs is investigated using two methods, namely 192Ir and eBx™ Brachytherapy. The second method, which was recently introduced clinically, operates at ~50 kV, which is also the optimal beam energy for DE. In this in vitro study, two cancer cell lines, lung (A549) and prostate (DU145), were used. Cells were incubated with 1 mM (2% w/w) concentration of AuNPs of ~15 nm in size. The control groups were exposed to a range of doses from 0 (control) to 6 Gy, with eBx™ and 192Ir sources separately. A clonogenic assay was conducted to determine cell survival curves.ResultsHigh dose enhancement factor (DEF) values were achieved in treated groups with low concentration of AuNPs with the 50 kV energy associated with the eBx™. The DE levels in eBx™ for Du145 and A549 cells were found to be 2.90 and 2.06, respectively. The results showed DEFs measured for the same cell lines using 192Ir brachytherapy to be 1.67 and 1.54 for Du145 and A549 cancer cells, respectively. This clearly indicates that much higher DE values are obtained in the case of eBx™ X-ray brachytherapy compared to 192Ir gamma brachytherapy.ConclusionThe higher DE values obtained with eBx™ compared to 192Ir brachytherapy can be attributed to the lower average energy of the former and being closer to the optimal energy for DE. This could potentially be utilized by medical practitioners and clinicians to achieve the same tumor control with a significantly lower dose from the eBx™ compared to the 192Ir brachytherapy treatment, thus bringing huge benefits to the brachytherapy-treated patients.

Energy optimization in gold nanoparticle enhanced radiation therapy

Gold nanoparticles (GNPs) have been demonstrated as radiation dose enhancing agents. Kilovoltage external photon beams have been shown to yield the largest enhancement due to the high interaction probability with gold. While orthovoltage irradiations are feasible and promising, they suffer from a reduced tissue penetrating power. This study quantifies the effect of varying photon beam energies on various beam arrangements, body, tumor, and cellular GNP uptake geometries. Cell survival was modeled based on our previously developed GNP-local effect model with radial doses calculated using the TOPAS-nBio Monte Carlo code. Cell survival curves calculated for tumor sites with GNPs were used to calculate the relative biological effectiveness (RBE)-weighted dose. In order to evaluate the plan quality, the ratio of the mean dose between the tumor and normal tissue for 50–250 kVp beams with GNPs was compared to the standard of care using 6 MV photon beams without GNPs for breast and brain tumors. For breast using a single photon beam, kV + GNP was found to yield up to 2.73 times higher mean RBE-weighted dose to the tumor than two tangential megavoltage beams while delivering the same dose to healthy tissue. For irradiation of brain tumors using multiple photon beams, the GNP dose enhancement was found to be effective for energies above 50 keV. A small tumor at shallow depths was found to be the most effective treatment conditions for GNP enhanced radiation therapy. GNP uptake distributions in the cell (with or without nuclear uptake) and the beam arrangement were found to be important factors in determining the optimal photon beam energy.

Generation of uniform electron beam plasma in a dielectric flask at fore-vacuum pressures

We describe a system for the generation of spatially uniform and homogeneous dense plasma in a dielectric flask using a forevacuum-pressure plasma-cathode electron beam source. At optimum beam energy and gas pressure, the non-uniformity in plasma density distribution along the length of the flask is less than 10%, and the plasma density and electron temperature in the flask are greater than for the plasma produced in the vacuum chamber with no flask. The measured parameters of the beam plasma in the flask are compared to the predictions of a model based on balance equations.

Improvements in PIXE analysis of hourly particulate matter samples

Most air quality studies on particulate matter (PM) are based on 24-h averaged data; however, many PM emissions as well as their atmospheric dilution processes change within a few hours. Samplings of PM with 1-h resolution can be performed by the streaker sampler (PIXE International Corporation), which is designed to separate the fine (aerodynamic diameter less than 2.5μm) and the coarse (aerodynamic diameter between 2.5 and 10μm) fractions of PM. These samples are efficiently analyzed by Particle Induced X-ray Emission (PIXE) at the LABEC laboratory of INFN in Florence (Italy), equipped with a 3MV Tandetron accelerator, thanks to an optimized external-beam set-up, a convenient choice of the beam energy and suitable collecting substrates. A detailed description of the adopted set-up and results from a methodological study on the detection limits for the selection of the optimal beam energy are shown; the outcomes of the research on alternative collecting substrates, which produce a lower background during the measurements, and with lower contaminations, are also discussed.

Electron beam effect on biomaterials I: focusing on bone graft materials.

BackgroundTo develop biocompatible bony regeneration materials, allogenic, xenogenic and synthetic bones have been irradiated by an electron beam to change the basic structures of their inorganic materials. The optimal electron beam energy and individual dose have not been established for maximizing the bony regeneration capacity in electron beam irradiated bone.ResultsCommercial products consisting of four allogenic bones, six xenogenic bones, and six synthetic bones were used in this study. We used 1.0-MeV and 2.0 MeV linear accelerators (power: 100 KW, pressure; 115 kPa, temperature; -30 to 120°C, sensor sensitivity: 0.1-1.2 mV/kPa, generating power sensitivity: 44.75 mV/kPa, supply voltage: 50.25 V), and a microtrone with different individual irradiation doses such as 60 kGy and 120 kGy. Additional in vitro analyses were performed by elementary analysis using field emission scanning electron microscopy (FE-SEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and confocal laser scanning microscopy (CLSM). In vivo clinical, radiographic, and micro-computed tomography (Micro-CT) with bone marrow density (BMD) analysis was performed in 8- and 16-week-old Spraque-Dawley rats with calvarial defect grafts.ConclusionsElectron beam irradiation of bony substitutes has four main effects: the cross-linking of biphasic calcium phosphate bony apatite, chain-scissioning, the induction of rheological changes, and microbiological sterilization. These novel results and conclusions are the effects of electron beam irradiation.

<i>In Situ</i> Soldering Process Technique by Synchrotron X-Ray Imaging

This paper demonstrates the development of an experimental technique of in-situ observation for soldering of Sn-0.7wt%Cu lead-free solder on a Cu substrate which was achieved for the first time by synchrotron X-ray imaging. Reactions between liquid solder and Cu substrate during a soldering process were able to be recorded in real-time. Individual stages of the soldering process consisted of flux activation in removal of Cu oxide, solder melting and contact with the Cu substrate (wetting) and intermetallic compound (IMC) and void formation between the solder and Cu substrate. The technique development which includes experimental setup with calculated optimum beam energy in the range of 20 – 30 keV appears to result in a clear observation of real-time X-ray imaging of the soldering process. This technique provides a key method to understand the mechanism of formation of micro-electronic inter-connects for future electronic packaging applications.

The Correct Selection of Pitch for Optimal CT Scanning: Avoiding Common Misconceptions

Today’s state-of-the-art CT scanners include many features that aid in the selection of optimal technique parameters. Vendors offer solutions for choosing the optimal beam energy (tube voltage), automatic exposure control (AEC) via tube current modulation control, patient positioning within the gantry, and patient-specific contrast injection protocols. The trend seems to be leading to a “push button” CT scanner in which only the dose, noise level, and image sharpness, determined by the clinical indication, need to be prescribed. This trend will likely decrease the frequency of nondiagnostic CT scans. However, it should not mitigate the need to understand some of the fundamental relationships between acquisition parameters and dose. We illustrate the most common misconceptions concerning the selection of pitch in this article.

Electron linac based mixed-field transmutation of 129I

The goal of this work was to determine the feasibility of using electron linacs for transmutation of selective long-lived fission products (LLFPs), particularly 129I. We have designed a converter system that produces both photons and neutrons, thus creating a mixed radiation field. The strength of the field depends on electron beam energy and current, as well as the converter material and geometry. The converter was optimized to maximize transmutation rate of 129I via two channels: 129I(γ,n)128I and 129I(n,γ)130I. The optimum electron beam energy was found to be around 100MeV. Computer simulations were benchmarked by experimental data on 133Cs (129I surrogate) photon-induced and neutron-induced transmutation rates. While further optimization of the system is necessary, we have demonstrated that accelerator-driven photonuclear reactions can be practical for 129I transmutation.

Gold bearing ore assays using 197Au(γ,n)196Au photonuclear reaction

We performed computational and experimental studies of the feasibility of the gold bearing ore assay utilizing the 197Au(γ,n)196Au photonuclear reaction. Gold bearing silicate samples were irradiated using bremsstrahlung produced by an electron accelerator with endpoint energies ranging from 25 to 40 MeV. 196Au yield simulations were benchmarked and experimental results were in good agreement with the predictions. Optimum electron beam energy for photon activation analysis was found to be around 32 MeV which corresponded to a detection limit of 80 ppb. Two-hour gamma-spectroscopy measurements were repeated every 24 h and the optimum sample cooling time was found to be about 100–160 h.

SU-E-T-462: Energy Modulated Photon Radiotherapy: A Monte Carlo Investigation

Purpose: To investigate the feasibility of energy modulated photon radiation therapy (EMXRT) using Monte Carlo simulations of photon beams of various energies. Methods: An EMXRT plan was generated for a prostate cancer patient treated with 10-MV 5-field intensity modulated radiotherapy (IMRT) optimized using Eclipse treatment planning system. Based on beam characterization of a Varian Clinac with EGS4/BEAM Monte Carlo code, multiple source models were first generated to represent the photon beams with energy of 1, 2, 3, 4, 5, 6, 10 and 15 MV, respectively. Optimal beam energy was then selected based on the effective path-length in the patient via ray-tracing for each beam angle. An inverse planning system based on gradient search algorithm was used to optimize photon beam intensity of various beam energies with pre-simulated Monte Carlo pencil beam dose distributions in patient anatomy. Finally, both EMXRT and IMRT plans were simulated with EGS4/MCSIM for 3D dose distributions in patient and compared. Results: Based on different path-lengths, 5, 6 and 10 MV photons were chosen in our EMXRT plan with lower energy photons used for shorter path-lengths. DVH analysis indicated that the target coverage in EMXRT plan was less uniform with Dmax and Dmin at 111.6% and 92.6% of prescription dose, respectively, as compared to 106.2% and 97.8% in regular IMRT plan. On the other hand, critical structures were much more spared in EMXRT plan than in IMRT plan, with 32% dose reduction in rectum and 40% reduction in bladder, respectively. The integral dose to the surrounding normal tissues was significantly reduced by 56% in EMXRT plan. Conclusion: This work demonstrates the potential of this Monte Carlo based tool for investigating the feasibility and desirability of EMXRT. Further investigation on more complex tumor sites such as head and neck cancer are now in progress.

TU‐G‐110‐08: Feasibility of Tissue Composition Measurement with Dual Energy Computed Tomography

Purpose: To investigate the feasibility of tissue composition measurement with dual energy computed tomography as compositional information may help to better characterize suspicious lesions. Method and Materials: Simulations and experimental studies were performed for a flat panel dual energy dual kVp CT system. Simulations were performed to identify optimal beam energy combinations. A figure of merit (FOM) was used to determine the optimal dual energy signal to noise ratio with respect to mean glandular dose. Beam energies ranging from 40 to 140 kVp were simulated in 1 kVp increments. The distribution of dose between low and high energy images was simulated at intervals of 10%. An experimental calibration phantom of 3.175 cm in diameter was constructed from a polyoxymethylene plastic with cylindrical holes filled with water and oil. Similar size samples of pure adipose and lean bovine tissues were also prepared. The phantom and tissue samples were imaged with the dual energy CT system. The calibration phantom was used to estimate the water, lipid and protein contents of each tissue sample. Tissue composition results computed from images were compared to data from chemical analysis of prior tissue samples. Results: The predicted spectra from simulation which optimized the FOM were at beam energies of 40 kVp and 140 kVp with the mean glandular dose divided equally between each exposure. Given tube loading and system constraints, experimental beam energies for the dual kVp CT system were selected to be 50 kVp and 120 kVp. The percentage RMS errors of water, lipid and protein contents as compared to data from chemical analysis were 10.9% for the dual kVp technique. Conclusion: The results of this study suggest that the water, lipid, and protein content may be measured with dual energy CT with relatively good agreement. This might potentially be useful for characterizing suspicious lesions.

Treatment planning considerations in contrast-enhanced radiotherapy: energy and beam aperture optimization

It has been shown that the use of kilovoltage x-rays in conjunction with a contrast agent incorporated into the tumor can lead to acceptable treatment plans with regard to the absorbed dose distribution produced in the target as well as in the tissue and organs at risk surrounding it. In this work, several key aspects related to the technology and irradiation techniques necessary to clinically implement this treatment modality are addressed by means of Monte Carlo simulation. The Zubal phantom was used to model a prostate radiotherapy treatment, a challenging site due to the depth of the prostate and the presence of bony structures that must be traversed by the x-ray beam on its way to the target. It is assumed that the concentration levels of the enhancing agent present in the tumor are at or below 10 mg per 1 g of tissue. The Monte Carlo code PENELOPE was used to model a commercial x-ray tube having a tungsten target. X-ray energy spectra for several combinations of peak electron energy and added filtration were obtained. For each energy spectrum, a treatment plan was calculated, with the PENELOPE Monte Carlo code, by modeling the irradiation of the patient as 72 independent conformal beams distributed at intervals of 5° around the phantom in order to model a full x-ray source rotation. The Cimmino optimization algorithm was then used to find the optimum beam weight and energy for different treatment strategies. It is shown that for a target dose prescription of 72 Gy covering the whole tumor, the maximum rectal wall and bladder doses are kept below 52 Gy for the largest concentration of contrast agent of 10 mg per 1 g of tissue. It is also shown that concentrations of as little as 5 mg per 1 g of tissue also render dose distributions with excellent sparing of the organs at risk. A treatment strategy to address the presence of non-uniform distributions of the contrast agent in the target is also modeled and discussed.

Towards the optimal energy of the proton driver for a neutrino factory and muon collider

Cross section data from the HARP experiment for pion production by protons from a tantalum target have been convoluted with the acceptance of the front-end channel for the proposed neutrino factory or muon collider and integrated over the full phase space measured by HARP, to determine the beam-energy dependence of the muon yield. This permits a determination of the optimal beam energy for the proton driver for these projects. The cross section data are corrected for the beam-energy dependent amplification due to the development of hadronic showers in a thick target. The conclusion is that, for constant beam power, the yield is maximum for a beam energy of about 7 GeV, but it is within 10% of this maximum for $4<{T}_{\mathrm{beam}}<11\text{ }\text{ }\mathrm{GeV}$, and within 20% of the maximum for ${T}_{\mathrm{beam}}$ as low as 2 GeV. This result is insensitive to which of the two HARP groups' results are used, and to which pion generator is used to compute the thick target effects.