Electron Beam Energy Research Articles

Characterization of RF System for MIR/THz Free Electron Lasers at Chiang Mai University

The establishment of the mid-infrared and terahertz free-electron laser (MIR/THz FEL) facility is ongoing at the PBP-CMU Electron Linac Laboratory (PCELL) in Chiang Mai University. The facility utilizes an S-band radio-frequency (RF) gun and a linear accelerator (linac) to generate and accelerate electron bunches. These electron bunches are accelerated in the RF gun and the linac using RF pulses with a frequency of 2856 MHz. Measuring the RF properties becomes essential, as the RF pulse information can be utilized to estimate the electron beam properties. To achieve the measurement results, we employed an RF measurement system comprising directional couplers, coaxial cables, attenuators, a crystal detector, and an oscilloscope. Prior to conducting measurements, the crystal detector and RF equipment were calibrated and characterized to ensure precise and reliable results. The electron beam energy estimation using the measured RF power was compared with the measured beam energies. The gun and the linac were operated with an absorbed RF power of 1.52 MW and an input power of 1.92 MW, respectively. The estimated electron beam energies were found to be 2.18 MeV and 15.0 MeV, respectively, closely aligning with the measured beam energies of 2.1 MeV and 14.0 MeV after the gun and linac acceleration. These consistent energy values support the reliability of our RF power measurement system and procedure.

Feasibility assessment of polycrystalline CsPbI3 relative dosimeters in photon and electron beam radiotherapy

Volumetric modulated arc therapy represents the latest technology in radiotherapy. It involves continuous modification of the multi-leaf collimator spatial distribution, dose rate, and gantry rotational speed, necessitating a dosimeter with high spatial resolution and exceptional sensitivity per unit volume. In particular, cesium-based inorganic perovskites have been studied for various applications, spanning from photoconductor solar cells to radiation detectors. These perovskites are renowned for their outstanding attributes, including thermal stability, inorganic stability, and light absorption capacity. Despite such advantageous characteristics, CsPbI3 materials have only been investigated in radiodiagnostics, with limited exploration in radiotherapy. To address this gap, this study verified the viability of CsPbI3 materials, note for their outstanding radiation detection efficiency, as dosimeters capable of measuring the radiation detection performance for radiotherapy devices. The reproducibility, linearity, and percent depth dose (PDD) were evaluated under the application of photon and electron beams in linear accelerators. The reproducibility assessment revealed impressive results, with the relative standard deviation registering at 0.53%, 0.32%, and 0.38% under electron beam energies of 6, 9, and 12 MeV and 0.45%, and 0.89% under photon beam energies of 6 and 15 MV. Moreover, the linearity test revealed an R 2 value of 0.9999, indicating high linearity, at 6, 9, and 12 MeV and at 6 and 15 MV. The PDD graphs drawn for the CsPbI3 dosimeter fabricated in this study showed that the D max points were consistent. The novel CsPbI3 dosimeter demonstrated a level of detection performance that satisfied all criteria; reproducibility, linearity, and PDD. The results collectively indicated that the CsPbI3 dosimeter can be used for dosimeters in radiotherapy devices.

Mathematical modelling of the emission characteristics of a field electron cathode in a scanning electron microscope under biosampling conditions

Currently, the use of electron microscopes in medicine is developing intensively, including scanning electron microscopes (SEM), which are designed to solve a huge number of problems in various fields with a wide range of electron accelerating voltages and electron beam energies. The development of an SEM with certain emission characteristics, with a range of lower beam energies for the study of biological samples, is an urgent task because modifying the SEM to solve problems in medicine, for example, would make it possible to obtain higher-quality images of biospecimens for diagnostics and monitoring the effectiveness of therapy. To develop new SEMs with certain characteristics, it is proposed to conduct less expensive research using numerical methods based on mathematical models of processes in electron-optical SEM systems. In this regard, this work sets the task of determining the size and shape of the beam, the main emission characteristics of the field electron cathode (FEC) of the SEM, which is under the influence of the electric field that excites electron emission and the external longitudinal magnetic field by studying the movement of the outermost electron of the beam, taking into account the influence of space charge beam electrons, external magnetic field. In the model, the FEC is approximated by a paraboloid of rotation, and the concept of a boundary “outermost” electron is introduced, the trajectory of which determines the shape and size of the beam. The problem of calculating the emission characteristics along the trajectory of the outermost electron of a FEC is solved using a mathematical model that includes the following equations: motion of the “outermost” electron, Maxwell outside and inside the beam, continuity of the current density, Fowler-Nordheim equation. As a result, a system of 18 first-order ordinary differential equations was obtained, the numerical calculation of which using the 4th order Runge-Kutta method allows us to obtain the emission characteristics of the FEC. As a result, it is suggested that it would be feasible to modify SEMs for more effective use in the medical field, taking into account their increasing use in disease diagnosis and the possible improvement of image quality through the development of FEC SEMs with more suitable characteristics.

Observation of Renner-Teller and predissociation coupled vibronic intensity borrowing in dissociative electron attachment to OCS.

We use a time-of-flight-based velocity map imaging method to look into the dissociative electron attachment to a linear OCS molecule at electron beam energies ranging from 4.5 to 8.5eV. The conical time-gated wedge slice imaging method is utilized to extract fragments' slice images, kinetic energy (KE), and angular distributions, which provide a complete kinematic understanding of this experiment on the dissociative electron attachment process. We observe that the formation of S- is relatively higher than the O- product. Three distinct dissociative KE bands of S-/OCS have been observed for the 5.0 and 6.5eV resonance positions. We notice a prominent rovibrationally coupled bimodality for each KE band in the variation of the most probable KE values. When the electron energy is changed from 5.5 to 6.0eV, we observed vibronic intensity borrowing in the highest momentum band of S- via the Σ → Π symmetric dipole-forbidden transitions within the 1.5eV energy gap. Multiple peaks in the angular distributions of S- and their modeling indicate the presence of Renner-Teller vibronic splitting. Using Q-Chem's implemented complex absorbing potential-equation of motion-electron affinity coupled cluster singles and doubles aug-cc-pVDZ+4s3p level of multireference-based electronic structure theory, we confirm the presence of OCS temporary negative ion bending vibrations and Renner-Teller vibronic splittings for the Π symmetric states. Additionally, we notice the presence of a non-radiative predissociation continuum (bringing down the rotational spectrum) and speed-dependent angular anisotropy in the S- fragmentation. Our findings at the resonance of OCS at 6.5eV closely align with the prediction of vibronic intensity borrowing by Orlandi and Siebrand [J. Chem. Phys. 58, 4513 (1973)].

Three-dimensional, time-dependent simulation of tapered EUV FELs with phase shifters

In this article, we have developed and evaluated a method for obtaining extreme ultraviolet (EUV) radiation by amplifying the third harmonic of the free-electron laser (FEL) radiation using phase shifters and tapering. Simulations of self-amplified spontaneous emission (SASE) FELs and seeding schemes are presented. We have demonstrated that the combination of phase shifts and tapering results in a more efficient technique that reduces electron beam energy by half. The stability of the scheme in relation to phase shift errors has been analyzed, and the implementation of the method has been discussed. The proposed FEL design enables a decrease in facility energy and a reduction in the cost of both new and existing projects in the EUV band.

Experimental characterization of the optical klystron effect to measure the intrinsic energy spread of high-brightness electron beams

The intrinsic energy spread of electron beams needs to be measured to characterize and optimize high-brightness electron beam sources such as those driving x-ray free-electron lasers (FELs). We demonstrate the use of the optical klystron effect as a precise and high-resolution method to measure the electron beam energy spread. The optical klystron setup consists of undulator modules and magnetic chicanes placed between them. The energy spread is found by measuring the radiation power produced in the undulators as a function of the chicanes’ strengths. High resolution and simplicity are the advantages of this approach, in contrast to the standard method, which measures the longitudinal phase space of the electron beam with a transverse deflector. The demonstration was performed at Athos, the soft x-ray FEL beamline of SwissFEL, for which we measured energy spreads below 1 MeV at a central beam energy of 3.4 GeV. We have verified the consistency of the method for different parameters (radiation wavelengths, undulator polarization configurations, and electron bunch durations) and we have benchmarked it against the standard measurement approach using a transverse deflector. Our results confirm the optical klystron as a valid approach to measure the electron beam energy spread. The method can be especially useful to reconstruct low energy spread values, where the conventional approach may be resolution limited, such as in ultra high-brightness radiofrequency photoinjectors or plasma sources, or when transverse deflectors are not available. Published by the American Physical Society 2024

Rapidly switchable x-ray orbital angular momentum from a free electron laser oscillator

X-ray vortices carrying tunable orbital angular momentum (OAM) are an emerging tool for x-ray characterization. However, in contrast to the generation of vortex beams in the visible wavelength region, the generation of x-ray vortices in a controlled manner has proved challenging. Here, we demonstrate an x-ray free-electron laser oscillator (XFELO) can adjust only the kinetic energy of the electron beam to produce vortex beams that can be programmed to dynamically change between different OAM modes, without the need for additional optical elements. With the nominal parameters of currently constructing 1 MHz repetition rate facility (i.e., Shanghai high-repetition-rate XFEL and Extreme Light Facility), the active formation of the OAM modes of l=±1 and l=±2 and the rapid switching between them by detuning the electron beam energy of the XFELO are numerically illustrated. The real-time switching can be achieved within 200 μs, while the output pulse energy can reach the 100 μJ level. This result extends the capabilities of XFELOs and paves the way for advanced at-source applications using x-ray vortex beams.

Electronic excitation of high-order spoof surface plasmons on metallic grating at terahertz frequencies

High-order spoof surface plasmon (SSP) mode on corrugated metallic surfaces can find many interesting applications, such as in imaging, sensing, transmission and enhanced radiation source, etc. In this paper, an efficient excitation method of the high-order SSP mode by using an injected electron beam on the uniform rectangular metallic grating is proposed and investigated numerically. Based on the matched wave momentum between the SSP mode and the electron beam, both the fundamental and high-order SSP modes can be excited on the structure by using a single injected electron beam. Numerical simulation results indicate that the maximum electric field intensity of the generated high-order SSP mode is about two orders higher than that of the fundamental SSP mode. In addition, the peak power of the excited high-order SSP mode is almost two times that of the fundamental SSP mode power by the same energy electron beam, which demonstrates the obvious advantage of the high-order SSP electronic excitation approach compared to the previous fundamental SSP mode excitation on the structure. The central working frequency of high-order SSP power spectrum is about three times that of the fundamental SSP power spectrum. Moreover, the influences of the injected electron beam energy on the excited SSP power spectrum are analyzed specifically. It is shown that the generated SSP power spectrum demonstrates a blue shift with the decreased working voltage of the electron beam simultaneously, with its peak power increasing. However, the working bandwidth is narrowed with decreased beam voltage, which further reveals its working mechanism of presented electronic excitation of the SSP mode. The presented studies provide a new method to excite a high-order SSP mode on the metallic grating, which can find some potential applications in high-sensitivity sensing, deep sub-wavelength waveguide, and many others in terahertz spectra.

Multi-point calorimeter using distributed fiber Bragg gratings for small field dosimetry in radiotherapy.

The interest of using fiber Bragg gratings (FBGs) dosimeters in radiotherapy (RT) lies in their (i) microliter detection volume, (ii) customizable spatial resolution, (iii) multi-point dose measurement, (iv) real-time data acquisition and (v) insensitivity to Cherenkov light. These characteristics could prove very useful for characterizing dose distributions of small and nonstandard fields with high spatialresolution. We developed a multi-point FBGs dosimeter customized for small field RT dosimetry with a spatial resolution of 1mm. The 3cm-long multi-point dosimeter is made by embedding a 80 silica fiber containing an array of thirty (30) co-located 1mm-long fs-written FBGs inside a plastic cylinder with an UV curing optical adhesive. With its higher thermal expansion coefficient, the plastic cylinder increases the sensitivity of the dosimeter by stretching the fiber containing the FBGs when the temperature rises slightly due to radiation energy deposition. Irradiations (2000MU at 600MU/min) were performed with a Varian TrueBeam linearaccelerator. The dose profile of a 2 2cm 6MV beam was measured with a mean relative difference of 1.8% (excluding the penumbra region). The measured output factors for a 6MV beam are in general agreement with the expected values within the experimental uncertainty (except for the 2 2cm field). The detector response to different energy of photon and electron beams is within 5% of the mean response ( pm/Gy). The calorimeter's post-irradiation thermal decay is in agreement with thetheory. An energy-independent small field calorimeter that allows dose profile and output factor measurements for RT using FBGs was developed, which, to our knowledge, has never been done before. This type of detector could prove really useful for small field dosimetry, but also potentially for MRI-LINAC since FBGs are insensitive to magnetic fields and for FLASH since FBGs have been used to measure doses up to100kGy.

Numerical characterization of dual-frequency capacitively coupled plasmas modulated by electron beam injection

The modulated approach of electron beam (EB) injection can achieve favorable parameters for capacitive coupled plasmas (CCP). In this work, a one-dimensional particle-in-cell/Monte Carlo collision (PIC/MCC) model is used to simulate the stable dual-frequency CCP with EB injection. First, when the parameters of EB are kept constant at 0.01 A and 30 eV, the results demonstrate significant enhancements in electron density, self-bias voltage, and ion flux. Furthermore, the electron energy probability function (EEPF) appears to have a transition from a typical bi-Maxwellian distribution to a Maxwellian distribution, and the dominant heating mode shifts from the α-mode to the α-γ-mode. Secondly, when the EB current and energy are all changed, the basic parameters of DF-CCP can be achieved by different modulations. Furthermore, we also discuss the transition of the electron heating mode as the current increases from 0.001 A to 1 A and the energy increases from 10 eV to 490 eV. In particular, we conduct a comparative study among different cases of EB injection. According to these results, the modulation capability of EB injection in DF-CCP is thoroughly investigated, which can greatly benefit atom-scale etching in practical applications.

Chaotic dynamics in X-ray free-electron lasers with an optical undulator.

In this work, the chaotic motions of relativistic electrons in X-ray free-electron lasers are investigated using an optical undulator in the presence of a magnetized ion-channel background. To miniaturize X-ray light sources, the optical undulator is a promising concept. The optical undulator provides higher optical gain than conventional magnetostatic undulators due to its micrometer wavelength. In addition, it reduces the required electron beam energy from several GeV to the multi-MeV range to produce X-ray pulses. The interaction of an optical undulator with an intense relativistic electron beam is a highly non-linear phenomenon that can lead to chaotic dynamics. At synchrotron radiation sources, the possibility of chaos control for X-ray FELs can be critical for certain classes of experimental studies. The equations of motion for a relativistic electron propagating through the optical undulator in the presence of a magnetized ion-channel can be derived from the Hamiltonian of the interaction region. Simulation results revealed that the intensity of the perturbation route from orderly behavior to chaos depends on the beam density, axial magnetic field strength, ion-channel density parameter, and pump laser undulator. Specific values of parameters were obtained for the transition from regular to chaotic paths. Bifurcation diagrams of the system were plotted to demonstrate the origin of chaos at a critical point, and Poincaré maps were created to distinguish between chaotic and orderly motions of electrons. The proposed new scheme can help to improve X-ray FELs, which have potential usages in basic sciences, medicine, and industry.

Beam induced heating in electron microscopy modeled with machine learning interatomic potentials.

We develop a combined theoretical and experimental method for estimating the amount of heating that occurs in metallic nanoparticles that are being imaged in an electron microscope. We model the thermal transport between the nanoparticle and the supporting material using molecular dynamics and equivariant neural network potentials. The potentials are trained to Density Functional Theory (DFT) calculations, and we show that an ensemble of potentials can be used as an estimate of the errors the neural network make in predicting energies and forces. This can be used both to improve the networks during the training phase, and to validate the performance when simulating systems too big to be described by DFT. The energy deposited into the nanoparticle by the electron beam is estimated by measuring the mean free path of the electrons and the average energy loss, both are done with Electron Energy Loss Spectroscopy (EELS) within the microscope. In combination, this allows us to predict the heating incurred by a nanoparticle as a function of its size, its shape, the support material, and the electron beam energy and intensity.

Online energy verification of linear electron accelerator: Important criteria for safety and beneficial applications

The electron beam (EB) energy is one of the most crucial parameters of EB treatment applications. It governs the dose distribution inside the bulk of the product treated with an energetic EB. An online monitoring and robust system is proposed for EB energy monitoring for radio frequency (RF) linear accelerator (LINAC). Attenuation method using dosimeter films is applied to reproduce the range of electron beam in aluminum. In online monitoring system, two electrically isolated aluminum plates having identical shape but different thicknesses, as per full penetration thickness of electron beam, are used. The current constituted in each plate is measured by an oscilloscope with suitable resistors, by keeping the set up under the beam. The ratio of the current signal from the front plate to the sum of the signals from both plates is very sensitive to the beam energy. Here, an electron accelerator of 10 MeV is used to incorporate this device. Sensitivity and robustness are the key factors to make this device highly suitable for desirous applications of 10 MeV LINAC and also to meet the regulatory mandates related to energy limitations for industrial utilities.

Dielectronic recombination experiment of Na-like Kr<sup>25+</sup> at heavy ion storage ring CSRe

The experimental study of precision spectroscopy of dielectronic recombination (DR) of highly charged ions is not only important for astronomical plasma and fusion plasma, but also can be used as a new precision spectroscopy to test the strong-field quantum electrodynamic effect, measure isotope shift, and extract the radius of atomic nuclei. An specially designed electron beam energy detuning system for electron-ion recombination precision spectroscopy experiments has been installed on the heavy ion storage ring CSRe in Lanzhou, China, where the electron-ion collision energy in the center-of-mass system can be detuned to 1 keV, and an independently-developed plastic scintillator detector and multiwire proportional chamber detector have been installed downstream of the electron cooler of the CSRe for detecting recombined ions. The multiwire proportional chamber detector has the ability to non-destructively monitor the profile of the ion beam in real-time while acquiring the recombined ion counts, providing guidance for optimizing the ion beam. On this basis, the first test experiment on dielectronic recombination of Kr<sup>25+</sup> ions is carried out at the CSRe, and the dielectronic recombination rate coefficients in a range of 0–70 eV in the frame of center-of-mass are measured. In order to fully understand the experimental results, we calculate the dielectronic recombination rate coefficient of the Kr<sup>25+</sup> ion by using the flexible atomic code (FAC) and make a detailed comparison with the experimental result, showing that they are in good agreement with each other, and only the resonance energy values of the two resonance peaks at 1.695 eV and 2.573 eV are significantly different. In addition, the DR resonance energy values and intensities are obtained by fitting the experimental results in a range of 0–35 eV, and we find that the transition 3s→4l (∆<i>n</i> = 1) contributes significantly to the experimental spectral lines. Furthermore, we compare the plasma rate coefficients derived from the DR rate coefficients with those derived from the AUTOSTRUCTURE and FAC theories, which differ by 20 percent in a temperature range less than 10<sup>6</sup> K. The experimental results show that the DR experimental platform of the CSRe has very good stability and reproducibility, and can provide support for the future DR experiments of highly charged ion, i.e. for testing strong-field quantum electrodynamics effect and measuring the properties of atomic nuclei.

An iterative algorithm to estimate the energy spectrum of an electron beam from PDD curves

Electron beam central-axis percentage depth dose (PDD) curves in water phantom are routinely employed to evaluate the electron beam energy at the phantom surface, in particular the mean and most probable energies from the values of R 50 (half-value range) and Rp (practical range). However, these two quantities are not enough to evaluate important details of the energy distribution, such as the FWHM (Full Width Half Maximum) and the possible presence of a low-energy tail. This paper presents a numerical method that allows estimating the shape of the energy spectrum from a PDD curve. The algorithm uses a database consisting of a set of depth dose curves for monochromatic beams computed by FLUKA in the range 0.1-7.0 MeV by steps of 0.1 MeV and, using an adaptive iterative Monte Carlo process, reconstructs the incident energy spectrum by minimizing the distance between the measured PDD and the computed one. Applications of a MATLAB code based on this algorithm to simulated and real measurements of electron beams done at APAM lab (ENEA Frascati) are presented. This approach represents a strong simplification with respect to energy analysis based on the use of a magnetic spectrometer.

Electron Beams Commissioning and Initial Measurements on an Elekta Synergy Platform Linear Accelerator

A linear accelerator (Linac) must be commissioned for use in treating cancer patients. This research work aims to analyze part of the electron beam data produced by the Elekta Synergy Platform Linac at the radiotherapy department at Tripoli University Hospital, Tripoli, Libya. In this paper, percentage depth dose (PDD), beam profile and applicators factor were studied at five different electron beam energies (4, 6, 8, 10 and 12 MeV). The relative measurement part of this study was carried out using a PTW MP3-M 3D water scanning system, and the absolute measurement was taken using a plane parallel ionization chamber and a unidose E electrometer. The analysis for these measurements has yielded the following results: a) The Penetrative qualities of all the electron beam energies were within the manufacturer's tolerance limits of ±1%; b) the maximum values of beam flatness of 2.94 and beam symmetry of 1.93 are within the accepted limits of International Electrotechnical Commission criteria; c) A penumbra maximum value of 1.30 was measured at the 4-MeV electron beam energy and using a 14×14 cm2 applicator size. All the obtained parameters were within the permissible limits. Therefore, the electron beams can be safely used for clinical purposes.

Analysis of contact zone of coating-substrate system exposed to irradiation with a pulse electron beam

Using the wire-arc additive manufacturing method (WAAM) on a 5083 aluminum alloy substrate, a non-equiatomic Mn – Cr – Fe – Co – Ni high-entropy alloy (HEA) coating was formed. By scanning and transmission electron diffraction microscopy we analyzed the structure, phase and elemental composition of the contact zone after irradiation with high-current low-energy electron beams with the following parameters: accelerated electron energy 18 keV, electron beam energy density 30 J/cm2, electron beam pulse duration 200 µs, number of pulses 3, pulse repetition rate 0.3 s–1. Multiphase multielement submicro- and nanocrystalline structures are formed predominantly in the substrate, which has a lower melting temperature compared to HEAs. Mutual doping of the coating – substrate system occurs in the contact layer, which has sinuous boundaries. The contact layers adjacent to the substrate and coating have the structure of high-speed cellular crystallization. In the layer adjacent to the substrate, the cells are formed by a solid solution of magnesium in aluminum. Interlayers of the second phase, enriched in atoms of the coating and substrate, are revealed along the cell boundaries. In the layer adjacent to the coating, the cells are formed by an alloy of composition 0.17Mg – 20.3Al – 4.3Cr – 16.7Fe – 9.3Co – 49.2Ni corresponding to the coating. Interlayers of the second phase, enriched mainly in magnesium and, to a lesser extent, in atoms of the HEA coating, are located along the cell boundaries. Central region of the contact zone with a thickness of ~1700 μm is formed by lamellar crystallites, which indicates the eutectic nature of its formation. Its main element is aluminum (≈77 at. %).

Enhancement of electron energies in the laser wakefield acceleration using a density up-ramp capillary gas-cell

In the laser wakefield acceleration (LWFA), the dephasing problem is a serious energy-limiting factor, which is caused by the velocity difference between the accelerated electrons and the laser wake wave. To overcome the dephasing problem, we developed a special capillary gas-cell with a density up-ramp along the laser propagation direction and used it for electron acceleration experiments. Our experiments, which were performed with a peak laser power of 15 TW at GIST, show that the electron beam energy was enhanced to 260 MeV compared with 98 MeV from a flat density profile, which is more than two fold by the density up-ramp due to the increase of the dephasing length in the density up-ramp. This is the first experimental demonstration for electron energy enhancement using the density up-ramp in a capillary gas-cell. Two-dimensional particle-in-cell (PIC) simulations were also performed to confirm the effect of the density up-ramp, which shows a good agreement with the experimental results. Compared with a gas jet, the capillary gas-cell can provide a more stable and longer plasma so that the density up-ramp method in the capillary gas-cell may produce high quality electron beams of energy up to GeV range.

Microbial quality and Aflatoxin levels of sorghum grains (Sorghum bicolor) irradiated with gamma rays, low energy electron beam (LEEB) and high energy electron beam (HEEB)

Sorghum grains (Sorghum bicolor) are used as food components for man as well as feed for animals. However, there have been reported cases of microbial contamination on sorghum grains. The present study investigated the comparative effects of gamma rays, low energy electron beam (LEEB) and high energy electron beam (HEEB) on the microbial quality and mycotoxin levels of sorghum grains. Sorghum grains were purchased from a local market in Accra, Ghana, and packaged in zip-lock bags. Samples were exposed to irradiation doses of 2, 4, 6, 8, and 10 kGy, and the un-irradiated sorghum grains served as control. For LEEB, the ILU-6 accelerator (250 keV) was used, and for HEEB ELEKTRONIKA 10-10 accelerator (9 MeV) was used. Gamma Chamber 5000 Co-60 source was used for gamma irradiation. Total viable counts, total coliforms, Bacillus cereus, Staphylococcus aureus, Salmonella spp, yeasts, and molds counts were determined using standard methods. Aflatoxins B1, B2, G1, and G2 were also evaluated. The presumptive yeast and molds were further analyzed using MALDI-TOF. All three sources of irradiation significantly reduced the microbial populations of the sorghum grains, and subsequently eliminated the microorganisms at high doses. However, at 10 kGy, total viable counts as well as yeasts and molds were still detected for LEEB. Aspergillus flavus was identified as an organism associated with the sorghum grains. The aflatoxin levels were below the detection limits. Gamma rays and HEEB were more effective than LEEB.

Three-pole wigglers at NSLS-II

The National Synchrotron Light Source-II (NSLS-II) at Brookhaven National Lab (BNL) is a third-generation medium-energy storage ring with 3 GeV and sub-nm-rad horizontal emittance, equipped with a top-off capability of 500 mA. It is designed to deliver an extremely intense photon beam across a wide spectral range, from the far-infrared to the very hard X-ray region. This outstanding performance is achieved through a combination of bending magnets (BM), three-pole wigglers (3 PW), and advanced insertion device (ID) sources. Six three-pole wigglers have been constructed at the NSLS-II IDs Lab. These devices are used to produce broadband radiation with lower angular power density and to monitor the electron beam emittance and energy spread. This paper describes the R&D activities focused on developing the required magnetic and mechanical designs, along with magnetic field optimization and the final magnetic measurement results. It also covers the spectral brightness, flux, power density, spatial and angular output properties of the 3 PWs, including their commissioning results and their effects on the performance of the NSLS-II storage ring.