Γ-ray Beam Research Articles

New Method for Precise Determination of the Isovector Giant Quadrupole Resonances in Nuclei

The intense, nearly monoenergetic, 100% polarized γ-ray beams available at the HIγS facility, along with the realization that the E1-E2 interference term that appears in the Compton scattering polarization observable has opposite signs in the forward and backward angles, make it possible to obtain an order-of-magnitude improvement in the determination of the parameters of the isovector giant quadrupole resonance (IVGQR). Accurate IVGQR parameters will lead to a more detailed knowledge of the symmetry energy in the nuclear equation of state which is important for understanding nuclear matter under extreme conditions such as those present in neutron stars. Our new method is demonstrated for the case of (209)Bi.

Mineralization of aqueous phenolate solutions: A combination of irradiation treatment and wet oxidation

Wet oxidation (high-temperature, high-pressure oxidation of organic wastes in aqueous solution) and radiation technology were combined in γ-ray and electron beam induced oxidation of 4×10−4–1×10−2moldm−3 Na-phenolate solutions in a wide O2 concentration (1–20bar pressure) and absorbed dose (0–50kGy) range. Most experiments were made in stainless steel high pressure autoclave equipped with magnetic stirrer. The rate of oxidation was followed by chemical oxygen demand and total organic carbon content measurements. The rate was similar in γ-ray and pulsed electron beam irradiation and increased with O2 concentration in the liquid.

Synchrotron radiation studies of spectral response features caused by Te inclusions in a large volume coplanar grid CdZnTe detector

We report preliminary results from a synchrotron radiation study of Te inclusions in a large volume single crystal CdZnTe (CZT) coplanar-grid detector. The experiment was carried out by probing individual inclusions with highly collimated monochromatic X- and γ-ray beams. It was found that for shallow X-ray interaction depths, the effect of an inclusion on measured energy loss spectra is to introduce a ∼10% shift in the peak centroid energy towards lower channel numbers. The total efficiency is however not affected, showing that the net result of inclusions is a reduction in the Charge Collection Efficiency (CCE). For deeper interaction depths, the energy-loss spectra shows the emergence of two distinct peaks, both downshifted in channel number. We note that the observed spectral behaviour shows strong similarities with that reported in semiconductors, which exhibit polarization effects, suggesting that the underlying mechanism is common.

Mössbauer spectroscopic study of an iron(III) complex with crown porphyrin

A complex of 57Fe with 5-{4-[((4′-hydroxybenzo-15-crown-5)-5′-yl)diazo]phenyl}-10,15,20-triphenylporphyrin was studied by Mossbauer spectroscopy. The presence of signals of two types in the spectra (a doublet and an extended absorption band over a wide velocity range) suggests that the Fe atoms occupy two structurally different positions in this complex. The dependences of the doublet asymmetry on temperature and the angle between the normal to the sample plane and the γ-ray beam were studied. The isomer shift δ of the doublet in the temperature range from 360 to 5 K changes from 0.25 to 0.41 mm/s, while the quadrupole splitting remains virtually unchanged (Δ ≈ 0.65 mm/s). The relaxation-type absorption over a wide velocity range, the relative area of which strongly varies with temperature, can be described by a broad singlet with the following parameters: δ = 0.30–0.44 mm/s and Γ = 2.8–3.38 mm/s. According to the δ values, both signals are due to Fe(III) derivatives.

Characterization of a Fricke dosimeter at high energy photon and electron beams used in radiotherapy

The dosimetric features of the Fricke dosimeter in clinical linear accelerator beams are considered. Experimental data were obtained using various nominal energies 6 and 18 MV, 12 and 15 MeV, including the (60)Co γ-ray beam. The calibration of the dosimeters was performed using the ionization chamber as a reference dosimeter. Some general characteristics of Fricke dosimeter such as energy dependence, optical density (OD)-dose relationship, reproducibility, accuracy, dose rate dependence were analyzed. The Fricke solution shows linearity in OD-dose relationship, energy independence and a good reproducibility over the energy range investigated. The Fricke dosimeter was found to be suitable for carrying out absorbed dose to water measurements in the calibration of high energy electron and photon beams.

Measurements of relative depth doses and Cerenkov light using a scintillating fiber–optic dosimeter with Co-60 radiotherapy source

In this study, we fabricated a scintillating fiber-optic dosimeter, which consists of an organic scintillator and a plastic optical fiber, for radiotherapy dosimetry. To select an adequate kind and length of scintillator for γ-rays generated from a Co-60 source, scintillating light from various kinds and lengths of organic scintillators is measured. Using a scintillating fiber-optic dosimeter, the γ-rays generated from a Co-60 therapy unit are measured and relative doses are obtained according to the field size of the γ-ray beam and the depth in a water phantom. Also, Cerenkov light generated by the interactions of primary or secondary electrons and the plastic optical fiber is measured with different field sizes and depths of a water phantom using a background optical fiber.

Comparison of the standards for absorbed dose to water of the NMIJ and the BIPM for 60Co γ-ray beams

A comparison of the standards for absorbed dose to water of the National Metrology Institute of Japan (NMIJ) and of the Bureau International des Poids et Mesures (BIPM) was carried out in the 60Co γ-ray reference beam of the BIPM in November to December 2009 under the auspices of the key comparison BIPM.RI(I)-K4. The comparison result, based on the calibration coefficients for two transfer standards and expressed as a ratio of the NMIJ and the BIPM standards for absorbed dose to water, is 0.9960(46). The degrees of equivalence between the NMIJ and the other participants in this comparison have been calculated and the results are given in the form of a matrix for the ten national metrology institutes (NMIs) that have participated. A graphical presentation is also given. Main text.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

Irradiation-Induced Metal Nanoparticles in Room-Temperature Ionic Liquid

Metal nanoparticles were prepared with γ-ray and accelerator electron beam irradiation in the 1-butyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (BuMeIm+Tf2N-) room-temperature ionic liquids. As for Au nanoparticles yielded in this investigation, the γ-ray irradiation made the particle size smaller compared to that by the accelerator electron beam irradiation. It is interesting to note that the nanoparticles prepared in this article were very stable although the surface was not covered with a stabilizing agent, which is usually employed so as to prevent aggregation. Similarly, other metal nanoparticle productions such as Ag, Cu, Mg, Al, Zn, and Fe were also investigated by means of the accelerator electron beam irradiation. In addition, some RTILs with Au nanoparticles yielded by the irradiation experiment showed fluorescent behavior under ultraviolet irradiation of 365 nm. It implies that the RTILs contain Au nanoparticles as well as Au clusters that cannot be observed by a common TEM system. In this study, we also found that the Si wafer, on which NaAuCl4⋅2H2O-added RTIL was spread, has distinctive two-dimensional Au microstructure crystals on the surface after the accelerator electron beam irradiation.

Performance testing of selected types of electronic personal dosimeters used in Sudan

Measurements were carried out for calibration and performance testing of a set of 10 electronic personal dosimeters (EPDs) at the Secondary Standard Dosimetry Laboratory of Sudan. Calibrations were carried out at three X-ray beam qualities described in ISO standard 4037 in addition to 137Cs and 60Co gamma ray beams. The experimental was performed with EPDs mounted on ICRU Slab phantom. X-ray and γ-ray beams were characterized in terms of air kerma free-in-air which were converted to the known delivered personal dose equivalent, Hp(10) using appropriate the air kerma to personal dose equivalent conversion coefficients. Dosimeters tested showed excellent energy and angular response and relative error of indication within the recommended limit for photon energies from 65 keV to 1.25 MeV. The study showed encouraging results for using electronic dosimeters in personal dosimetry.

Spin and parity assignments to dipole excitations of the odd-mass nucleus 207Pb from nuclear resonance fluorescence experiments with linearly-polarized γ-ray beams

Pb(γ⃗,γ′) photon scattering reactions were studied [1] with the nearly monochromatic, linearly polarized photon beams at the High Intensity γ-ray Source (HIγS) at the DFELL. Azimuthal scattering intensity asymmetries measured with respect to the polarization plane of the beam have been used for the first time to assign both the spin and parity quantum numbers of dipole excited states of 206,207,208Pb at excitation energies in the vicinity of 5.5 MeV. Evidence for dominant particle-core coupling is deduced from these results along with information on excitation energies and electromagnetic transition matrix elements.

Chitosan and radiation chemistry

Chitosan as a raw material with special properties has drawn attention of scientists working in the field of radiation processing and natural polymer products development, and also of specialists working in the field of radiation protection and oncologists. Especially the applications concern reduced molecular weight chitosan which still retain its chemical structure; such form of the compound is fostering biological, physical and chemical reactivity of the product. Chitosan degrades into fragments under γ-ray or electron beam irradiation. Antibacterial properties of the product are applied in manufacturing hydrogel for wound dressing and additional healing properties can be achieved by incorporating in the hydrogel matrix chitosan bonded silver clusters. Another possible application of chitosan is in reducing radiation damage to the radiation workers or radiation cured patients. In the case of radioisotopes oral or respiratory chitosan-based materials can be applied as chelators. Applications of chitosan in oncology are also reported.

Neutron generation in (γ, n) process assisted by inversely populated medium

Neutron production upon interaction of a γ-ray beam (generated using an inversely populated medium) with a target (which contains isotopes with a pronounced first photoneutron resonance) has been investigated. The research is mainly focused on the influence of the inversely populated medium on the prodaction and parameters of the γ radiation that causes the photonuclear reaction.

NUCLEAR PHOTON SCIENCE WITH INVERSE-COMPTON SCATTERING

Recent developments of the synchroton radiation facilities and intense lasers are now guiding us to a new research frontier with probes of a high energy GeV photon beam and an intense and short pulse MeV γ-ray beam. New directions of the science developments with photo-nuclear reactions are discussed. The inverse Compton γ -ray has two good advantages for searching for a microscopic quantum world; they are 1) good emmitance and 2) high linear and circular polarizations. With these advantages, photon beams in the energy range from MeV to GeV are used for studying hadron structure, nuclear structure, astrophysics, materials science, as well as for applying medical science.

Determination of the potential for extrinsic color development in natural colorless quartz

Colorless natural quartz can develop many extrinsic colors after exposure to ionizing radiation and heat due to trace elements such as aluminum, iron, hydrogen, lithium, and sodium. The infrared spectrum of colorless natural quartz is correlated to the development of these colors, because the bands between 3200 and 3600 cm-1 are related to the presence of trace elements. The colors produced by γ-ray or electron beam irradiation are caused by displacements of electrons in the quartz lattice and can be bleached by ultraviolet irradiation. Colors produced by irradiation and additional heating, however, are resistant to ultraviolet rays, probably due to Li+ diffusion. The infrared spectra of colorless natural quartz crystals can be used to identify the crystals’ potential for color development by irradiation and heating. At room temperature, all natural colorless samples of alpha quartz show bands at 2499, 2600, 2677, 2771, 2935, and 3063 cm-1. The samples that do not develop color after irradiation also show bands at 3202 and 3304 cm-1. The samples that become grayish to black after irradiation show three additional bands at 3381, 3433, and 3483 cm-1. This last band is related to the development of the colors greenish yellow, yellow, or brown (citrine) after irradiation and heating. The samples that become grayish olive green after irradiation and olive green after additional heating show a pair of bands at 3404 and 3510 cm-1 in addition to the former bands noted. The samples that become violet (amethyst) or green (prasiolite) after irradiation, or sky blue after irradiation plus heating show a broad band at ~3441 cm-1 and a band at 3585 cm-1.

Photoproduction of π0π+ pairs on proton and deuteron

The reaction of π0π+ photoproduction on free and quasi-free protons with γ-ray energies from 0.5 to 1.5 GeV has been studied. Its cross section was measured in the range θ π 0 ≥ 20°. The distributions of π0π+, π0n, and π+n invariant masses were analyzed. The experiment was performed using the Compton back-scattered γ-ray beam at the GRAAL facility (Grenoble, France), applying liquid deuterium and hydrogen targets and a large-aperture (almost 4π) detector. Particular attention was paid to analysis of systematic errors related to the neutron detection efficiency.

On the interpretation of the results of the experimental test of the Askar’yan effect

The effect of the environment on the results of measuring the radio radiation spectrum is considered in the experimental simulation of the cascade shower by a high-energy γ-ray beam in a dense medium. The calculation shows that the character of the measured energy spectrum depends on the location of the receiving antenna with respect to the shower axis.

Dense laser-driven electron sheets as relativistic mirrors for coherent production of brilliant X-ray and γ-ray beams

Several techniques exist to obtain brilliant X-ray beams by coherent reflection from relativistic electrons (Ee=γmc2) with Doppler frequency upshift of 4γ2. We describe a new approach starting with an ultra-thin solid target. Larger ‘driver’-laser intensities with high contrast are required to produce dense electron sheets. Their acceleration in vacuum results in a transverse momentum component besides the dominant longitudinal momentum component. The counter-propagating ‘production’ laser for optimum Doppler boost in X-ray production by reflection has to be injected opposite to the electron direction and not opposite to the driver laser. Different measures to increase the reflectivity of the electron sheet via laser trapping or free-electron-laser-like micro-bunching are discussed, extending the photon energy into the MeV range. Here, first-order estimates are given.

Experimental durability studies of electrolysis cell materials for a water detritiation system

The radiation durability of the polymers in the solid-polymer-electrolyte (SPE) water electrolyzer of the water detritiation system (WDS) was investigated. A series of γ-ray and electron beam irradiation tests on the Nafion ® N117 ion exchange membrane (a key polymer in the SPE electrolyzer, beyond the ITER-WDS requirement (530 kGy)) indicated that the Nafion ® N117 membrane had sufficient radiation durability (up to 1600 kGy) with regard to the mechanical strength and the ion exchange capacity. To maintain the electrolysis function of the SPE cell up to 530 kGy, we suggest replacing the Teflon ® insulator with a polyimide insulator. Any serious damage in the tensile strength of the Kapton ® polyimide (up to 1500 kGy) was not observed during the γ-ray irradiation tests. Regarding the rubber material selection for the O-ring seal, we observed that the VITON rubber swelling in the water kept the tensile strength value constant (up to 1500 kGy). Moreover organic elution was not observed in the water after irradiation. With regard to its stable tensile strength and negligible organic elution, VITON rubber is a suitable material for the O-ring seal.

Laser Inverse Compton Photon Beams: Past, Present and Future

We describe a brief history to generate inverse Compton γ-ray beams for science applications. It is discussed that we can open a new field for science developments with a high γ-ray beam, generated by using the coherent inverse Compton scattering.

A Model for Fast Rising, Slowly Decaying Subpulses in γ-ray Bursts

Gamma-ray bursts (GRBs) often feature subpulses that have a distinctively asymmetric profile—they rise quickly and decay much more slowly, while their spectrum softens slightly with observer time. It is suggested that these subpulses are caused by slow baryonic clouds embedded within a primary γ-ray beam, which scatter the γ-radiation into our line of sight as they accelerate. Good quantitative agreement is obtained with observed light curves and spectral evolution. The kinetic energy that the baryonic component of GRB jets receives from the primary γ-radiation is predicted to be about equal to the amount of γ-radiation that is scattered, consistent with observations of afterglow. Several other observational consequences are briefly discussed. The possibility is raised that the timescale of short GRBs is established by radiative acceleration and/or baryon injection rather than the timescale of the central engine.