MeV Maximum Energy Research Articles

A Reappraisal of the40Ar/38ArDating Technique via Irradiation withγ‐Rays

In a reconnaissance study, we investigated the potential of γ‐ray induced production of38ArKfrom39K for geochronological applications. For this purpose, various age monitors commonly in use for the established40Ar/39Ar‐method were co‐irradiated for 60 h at 17.6 MeV maximum energy in the ELBE facility, Dresden‐Rossendorf, Germany. Because the available energy was low, total production of38ArKwas depressed, leading to lowJ38‐values of (2.1–4.1) × 10‐6and hence resulted in only minor38Ar excess when compared with atmospheric38Ar/36Ar ratios. In spite of these restrictions, ages of younger monitors could be reproduced within error, whereas older age reference materials showed discrepancies due to the low production rate. We observed Ca‐derived contributions on36Ar in analysed CaF2reference materials, and calculated a limit for Ca‐interference on38ArCaof (38Ar/36Ar)Ca = 0.07 ± 0.03 (1s). In addition, we investigated a potential recoil redistribution of38Ar by stepwise heating experiments, but could not quantify this further because of concurring processes. More work at higher photon energies is necessary to resolve other open issues, in particular the potential of utilising40Ar/37Ar ratios for age determination and the possibility of42Ar production from44Ca, which would allow correction for Ca‐interference reactions on other Ar isotopes. This would be a pre‐requisite for dating extra‐terrestrial rocks.

Three-Dimensional Nondestructive Isotope-Selective Tomographic Imaging of 208Pb Distribution via Nuclear Resonance Fluorescence

Combining the nuclear resonance fluorescence (NRF) transmission method with computed tomography (CT) can be a novel method for imaging the isotope distributions, which is indispensable in nuclear engineering. We performed an experiment to reconstruct a three-dimensional NRF-CT image with isotope selectivity of enriched lead isotope rods (208Pb) together with a set of different rods, including another enriched isotope (206Pb), iron, and aluminum rods, inserted into a cylindrical aluminum holder. Using a laser Compton scattering (LCS) gamma ray beam with a 5.528 MeV maximum energy, 2 mm beam size, and 10 photon·s−1·eV−1 flux density, which is available at the BL1U beamline in the ultraviolet synchrotron orbital radiation-III (UVSOR-III) synchrotron radiation facility at the Institute of Molecular Science at the National Institutes of Natural Sciences in Japan, and we excited the Jπ = 1− NRF level at 5.512 MeV in 208Pb. An isotope-selective three-dimensional NRF-CT image of the 208Pb isotope distribution was experimentally obtained for the first time with a pixel resolution of 4 mm in the horizontal plane.

Progress in the realization and commissioning of the exotic beam facility SPES at INFN-LNL

SPES (Selective Production of Exotic Species) is an ISOL type facility for production and post-acceleration of exotic nuclei for forefront research in nuclear physics. Radioactive (RA) species (A = 80÷160) will be produced by fissions induced by a proton beam impinging on an UCx target: the proton beam will be delivered by a commercial cyclotron with a 40 MeV maximum energy and a 0.25 mA maximum current. The RA species, extracted from the Target-Ion-Source system as a 1+ beam, will be cooled in a RFQ (radiofrequency quadrupole) beam cooler (RFQ-BC) and purified from the isobars contaminants through a High Resolution Mass Separator (HRMS). Post-acceleration will be performed via an ECR-based charge breeder, delivering the obtained q+ RA beam to a being built CW RFQ and to the being upgraded superconducting (sc) linac ALPI (up to 10 MeV/A for a mass-to-charge ratio A/q = 7).

Abstract ID: 14 Montecarlo calculation of reaction cross sections for the production of innovative radionuclides

The production of innovative radionuclides in the context of theranostics is currently a topic of great interest. Various INFN projects are underway in search of new data and new techniques for radionuclides production. Among the possible channels under study, recent developments indicate 67Cu and 47Sc as good candidates competitive with more traditional nuclides, thanks to their application both for diagnostic and for therapy. INFN recently started two projects for the measurement of proton-induced reactions, considering the forthcoming use of the high-performance cyclotron installed at INFN-LNL (70 MeV maximum energy): COME in CSN3 (2016) and PASTA in CSN5 (Young Researchers grants 2016). The knowledge of reaction cross sections at low-intermediate energies is crucial in this context and, in parallel to the need of new measurements, it is important also to review the current situation in the reaction-model simulation of the production yields, by using the existing and available nuclear reaction codes. In particular the FLUKA code, based on the PEANUT (Pre-Equilibrium Approach to Nuclear Thermalisation) model, was used to calculate the production of residual nuclei in different experiments and is already validated with data. In this study we use FLUKA to calculate the reaction cross sections for the production of copper and scandium isotopes at the energy of interest for the LARAMED project (10–100 MeV). A comparison of the results obtained with dedicated codes (Talys and Empire) and with available experimental data is also given.

Laser-to-hot-electron conversion limitations in relativistic laser matter interactions due to multi-picosecond dynamics

High-energy short-pulse lasers are pushing the limits of plasma-based particle acceleration, x-ray generation, and high-harmonic generation by creating strong electromagnetic fields at the laser focus where electrons are being accelerated to relativistic velocities. Understanding the relativistic electron dynamics is key for an accurate interpretation of measurements. We present a unified and self-consistent modeling approach in quantitative agreement with measurements and differing trends across multiple target types acquired from two separate laser systems, which differ only in their nanosecond to picosecond-scale rising edge. Insights from high-fidelity modeling of laser-plasma interaction demonstrate that the ps-scale, orders of magnitude weaker rising edge of the main pulse measurably alters target evolution and relativistic electron generation compared to idealized pulse shapes. This can lead for instance to the experimentally observed difference between 45 MeV and 75 MeV maximum energy protons for two nominally identical laser shots, due to ps-scale prepulse variations. Our results show that the realistic inclusion of temporal laser pulse profiles in modeling efforts is required if predictive capability and extrapolation are sought for future target and laser designs or for other relativistic laser ion acceleration schemes.

188W/188Re Generator System and Its Therapeutic Applications

The188Re radioisotope represents a useful radioisotope for the preparation of radiopharmaceuticals for therapeutic applications, particularly because of its favorable nuclear properties. The nuclide decay pattern is through the emission of a principle beta particle having 2.12 MeV maximum energy, which is enough to penetrate and destroy abnormal tissues, and principle gamma rays (Eγ=155 keV), which can efficiently be used for imaging and calculations of radiation dose.188Re may be conveniently produced by188W/188Re generator systems. The challenges related to the double neutron capture reaction route to provide only modest yield of the parent188W radionuclide indeed have been one of the major issues about the use of188Re in nuclear medicine. Since the specific activity of188W used in the generator is relatively low (<185 GBq/g), the elutedRe188O4-can have a low radioactive concentration, often ineffective for radiopharmaceutical preparation. However, several efficient postelution concentration techniques have been developed, which yield clinically usefulRe188O4-solutions. This review summarizes the technologies developed for the preparation of188W/188Re generators, postelution concentration of the188Re perrhenate eluate, and a brief discussion of new chemical strategies available for the very high yield preparation of188Re radiopharmaceuticals.

Evaluation test of the energy monitoring device in industrial electron beam facilities

The electron beam energy monitoring device, previously developed and tested under standard laboratory conditions using electron beams in the energy range 4–12 MeV, has now been tested under industrial irradiation conditions in high-energy, high-power electron beam facilities. The measuring instrument was improved in order to measure high peak current delivered at low pulse repetition rate as well. Tests, with good results, were carried out at two different EB plants: one equipped with a LUE-8 linear electron accelerator of 7 MeV maximum energy used for cross-linking of cables and for medical device sterilization, and the other with a 10 MeV Rhodotron type TT 100 used for in-house sterilization.

Shielding design for a laser-accelerated proton therapy system

In this paper, we present the shielding analysis to determine the necessary neutron and photon shielding for a laser-accelerated proton therapy system. Laser-accelerated protons coming out of a solid high-density target have broad energy and angular spectra leading to dose distributions that cannot be directly used for therapeutic applications. A special particle selection and collimation device is needed to generate desired proton beams for energy- and intensity-modulated proton therapy. A great number of unwanted protons and even more electrons as a side-product of laser acceleration have to be stopped by collimation devices and shielding walls, posing a challenge in radiation shielding. Parameters of primary particles resulting from the laser–target interaction have been investigated by particle-in-cell simulations, which predicted energy spectra with 300 MeV maximum energy for protons and 270 MeV for electrons at a laser intensity of 2 × 1021 W cm−2. Monte Carlo simulations using FLUKA have been performed to design the collimators and shielding walls inside the treatment gantry, which consist of stainless steel, tungsten, polyethylene and lead. A composite primary collimator was designed to effectively reduce high-energy neutron production since their highly penetrating nature makes shielding very difficult. The necessary shielding for the treatment gantry was carefully studied to meet the criteria of head leakage <0.1% of therapeutic absorbed dose. A layer of polyethylene enclosing the whole particle selection and collimation device was used to shield neutrons and an outer layer of lead was used to reduce photon dose from neutron capture and electron bremsstrahlung. It is shown that the two-layer shielding design with 10–12 cm thick polyethylene and 4 cm thick lead can effectively absorb the unwanted particles to meet the shielding requirements.

SU‐FF‐T‐309: Laser‐Accelerated Proton Therapy: Target Chamber Design and Shielding Requirements

Purpose: Recent advances in laser technology have facilitated proton (light ion) acceleration using laser‐induced plasmas. In this work, we investigate target chamber designs and their shielding requirements for a laser‐proton therapy system. Method and Materials: This new therapy system employs laser‐accelerated protons. If successfully developed, it may provide a compact and cost‐effective solution to energy‐ and intensity‐modulated proton therapy (EIMPT). Since laser‐accelerated protons have broad energy and angular distributions, which are not suitable for radiotherapy applications directly, we have designed a compact particle selection and beam collimating system for EIMPT beam delivery. The target chamber contains the laser focusing and target assembles and is connected to the proton beam collimation and particle selection device. Monte Carlo simulations using MCNPX and FLUKA have been performed to verify the shielding walls for the experimental setup, which consist of stainless steel, polystyrene and lead. Results: The primary particles resulting from the laser‐target interaction are protons and electrons. Our particle in cell simulation predicted energy spectra with 300 MeV maximum energy for protons and 20 MeV for electrons for a laser intensity of 1021 W/cm2. The maximum number was 1011 and 1012 per pulse for protons and electron, respectively. Our Monte Carlo simulations showed that a combination of 1/4″ 304 stainless steel, 6″ polystyrene and 3″ lead will reduce the combined leakage dose equivalent to 0.32 μSv (0.032 mrem) per laser pulse at 1 m from the chamber, which included the effect of all primary and secondary particles. Conclusion: We have designed an experimental setup to accommodate the laser focusing mirror, the target assemblies, the beam collimator and the particle selection system. Different shielding walls are designed to ensure the leakage dose equivalent to within 20 μSv (2 mrem)/week.

TLD 300 Dosimetry in a 175 MeV Proton Beam

TLD-300 dosemeters have been successfully employed in high LET radiotherapeutic fields generated by fast neutron, negative pion and heavy ion beams. By proper peak height analysis of the two main peaks of CaF 2 :Tm glow curves after such irradiations it is possible to separate the high and low LET content of the radiation field. Therefore the distribution of the biological equivalent dose can be determined in a single irradiation. The method was extended to a pre-therapeutic proton field of 175 MeV maximum kinetic energy. It turned out that in such proton fields the sensitivity of the high temperature peak is constant; thus the dose can be determined to an accuracy of ±4%. The sensitivity of the low temperature peak decreases linearly to 50% as a function of y D such that the average lineal energy can be determined to an accuracy of ±5 keV.μm -1 .

Evaluation of the Undesired Neutron Dose Equivalent to Critical Organs in Patients Treated by Linear Accelerator Gamma Ray Therapy

A careful theoretical and experimental evaluation has been made in order to estimate the neutron dose equivalent for critical organs of patients treated by gamma ray therapy. The machine employed in these studies is the linear electron accelerator MD Class Mevatron, Siemens, installed at the S. Giovanni Battista A.S. Hospital in Torino (Italy) and used for tumour therapy. A calculational method was developed, using two suitable 3D Monte Carlo computer codes: the EGS4 code (Electron Gamma Shower), which evaluates bremsstrahlung gamma rays and photo-neutron production in the accelerator head and the MCNP code (Monte Carlo Neutron and Photon Transport), which simulates the neutron transport and evaluates the organ dose equivalents. In addition, two sets of measurements were made during treatment sessions with 2 Gy therapeutic gamma dose: (a) by means of thermoluminescence dosemeters TLD-600 and TLD-700 placed at various depths inside an anthropomorphic phantom in positions corresponding to the organs; (b) in vivo by albedo neutron personal dosemeters UD-802, National Panasonic, positioned on the patients according to the organs. The agreement between experimental and theoretical data is good. The neutron organ dose equivalents are by no means negligible; for instance HT varies from 2.65 mSv on the thyroid to 42.02 mSv on testes, if normalised to one Gy of maximum absorbed dose in the pelvis, of the primary gamma beam if 15 MeV maximum energy (10 cm × 10 cm field size and source-skin distance of 1 m).

Fission yields of209Bi andnatPb nuclei induced by photon beams of 226 MeV maximum energy from compton backscattered laser light

The yields of the photofission reactions induced in209Bi andnatPb by quasi-monochromatic photon beam of 226 MeV maximum energy have been measured by using makrofol plates as solid-state detector of fission tracks and found to be (1.1±0.4) mb and (0.8±0.4) mb, respectively. The measured yields are compared with data of fission induced in the same targets by different photon beams.

Microwave electron gun theory and experiments

A general microwave electron gun (rf gun) theory and some new ideas about further reducing the emittance of electron beams are reviewed and introduced briefly. Experimental results are presented from a thermionic cathode rf gun which has been developed for Beijing Free-Electron Laser Project (BFELP) at Institute of High Energy Physics (IHEP), Academia Sinica as the injector of 30 MeV constant gradient linac. LaB6 is used as the thermionic emitter with 100 crystal surface and the temperature around 1620 °C. Back bombardment heating effect and another effect connected with the cathode surface temperature was observed. An electron beam with macropulse length 4 μs, repetition rate 12.5 Hz, greater than 500 mA beam current during macropulse and around 1 MeV maximum energy has been obtained. In the last section of this article, two useful formulas used to determine electric field distribution near the cathode surface and coupling coefficient β of a rf gun are introduced.

Rf gun development at IHEP for BFELP

A rf gun injection system was developed for the Beijing free electron laser project (BFELP) at IHEP. LaB 6 was used as a thermionic emitter with the temperature around 1620°C. Backbombardment heating effect (BHE) and another effect connected with the cathode surface temperature were observed. An electron beam with 4 μs macropulse, 12.5 Hz repetition rate, greater than 500 mA beam current during macropulse and around 1 MeV maximum energy was obtained.

The microprobe at the Eindhoven University of Technology

The 3.5 MeV proton microbeam of the Eindhoven University of Technology is produced from an AVF cyclotron beam of 30 MeV maximum energy by a 1 × 1 mm 2 object diaphragm and a quadruplet lens system of high demagnification. A beam current of 150 nA was obtained in a spot of 60 × 40 μm 2 and a current of 2 nA in a spot of 10 × 10 μm 2 . In the near future the minicyclotron ILEC will become operational. The beam specifications of this machine are an order of magnitude better for microprobe applications than those of the 30 MeV cyclotron. An important application of the present EUT microprobe is the detection of platinum in rat tumors treated with cisplatin. When higher currents are available in a small spot, sensitivity is limited by sample deterioration. Some methods to cope with those problems are discussed.

Cell death (apoptosis) in the mouse small intestine after low doses: effects of dose-rate, 14.7 MeV neutrons, and 600 MeV (maximum energy) neutrons.

The production of dead (apoptotic) cells by low doses of gamma-rays was independent of dose-rate between 0.27 and 450 cGy per min. The r.b.e. for doses of 14.7 MeV neutrons between 1 and 15 cGy was about 4, and for neutrons generated by bombarding a beryllium target with 600 MeV protons the r.b.e. was about 2.7. The dose-incidence curves for all three radiation types reached a plateau at about 3-4 dead cells per crypt section, and this occurred at about 20-40 cGy of gamma-rays. These curves are compatible with exponential survival of the cell population at risk (D0 of 24 cGy for gamma-rays, 6 cGy for 14.7 MeV neutrons and 9 cGy for 600 MeV neutrons). Since the dose-response is exponential there is no indication of much higher r.b.e. values at very low doses, a point of concern in radiation protection. The spatial distribution of dead cells in the crypt was similar after doses of gamma-rays or neutrons, indicating that the same population of target cells was affected in both cases.

A method for calculating megavoltage x-ray dose and dose parameters.

Limitations of the most commonly used dose calculation methodologies as apply to medium and high-energy x rays are discussed. A method is presented whereby the dose to a point in medium is divided into several components with expressions given for various components. The depth of transient-charged particle equilibrium is chosen as the reference point. Equations are derived for calculating and relating the dose parameters including the percent depth dose, the tissue-reference ratio, and the scatter-reference ratio. Particular emphasis is placed on the accuracy and adequacy of the technique in the region of buildup. The applicability of the present method to megavoltage photons is established for a number of x-ray beams in the range 4-45 MeV maximum energy.

Absorbed dose distributions in small copper wire insulation due to multiple-sided irradiations by 0.4 MeV electrons

When scanned electron beams are used to crosslink polymeric insulation of wire and cable, an important goal is to achieve optimum uniformity of absorbed dose distributions. Accurate measurements of dose distributions in a plastic dosimeter simulating a typical insulating material (polyethylene) surrounding a copper wire core show that equal irradiations from as few as four sides give approximately isotropy and satisfactorily uniform energy depositions around the wire circumference. Electron beams of 0.4 MeV maximum energy were used to irradiate wires having a copper core of 1.0 mm dia. and insulation thicknesses between 0.4 and 0.8 mm. The plastic dosimeter simulating polyethylene insulations was a thin radiochromic polyvinyl butyral film wrapped several times around the copper wire, such that when unwrapped and analyzed optically on a scanning microspectrophotometer, high-resolution radial and depth-dose profiles could be determined.

Effects of negative pions and neutrons on the growth of Vicia faba bean roots.

Vicia faba bean roots have been irratiated with neutrons of various energies and with negative pi-mesons, and the effect on the ten-day growth of the roots has been determened. The neutron irratiations were made in beams of 400 and 600 MeV maximum energy, as well as with neutrons from a plutonium-beryllium source (mean energy 4.4 MeV) and from a 14 MeV neutron generator. The bean roots have also been irradiated at various points along the depth-dose curve of negative pi-mesons, including the gegion where the pions annihilate on coming to rest. The results show a maximum relative biological effectiveness (RBE) of 3.7 for 50% reduction in ten days growth for stopped negative pions and values up to 3.3 for high-energy neutrons, compared to 5.5 for 14 MeV neutrons. The biological effectiveness of high-energy neutrons and stopped pions shows a more pronounced dependence on dose than does the effect with lower-energy neutrons.

Photofission in238U,232Th and209Bi at intermediate energy

Fragment energy correlation measurements have been made for238U,232Th and209Bi with bremsstrahlung of 600 MeV maximum energy. The study was performed with silicon surface barrier detectors. Distributions of kinetic energy as a function of fragment mass are presented. The results are compared with earlier photofission data and, in the case of bismuth, with calculations based on the liquid drop model.