Nuclear Gamma Rays Research Articles

Demonstration of nuclear gamma-ray polarimetry based on a multi-layer CdTe Compton camera

To detect and track structural changes in atomic nuclei, the systematic study of nuclear levels with firm spin-parity assignments is important. While linear polarization measurements have been applied to determine the electromagnetic character of gamma-ray transitions, the applicable range is strongly limited due to the low efficiency of the detection system. The multi-layer Cadmium-Telluride (CdTe) Compton camera can be a state-of-the-art gamma-ray polarimeter for nuclear spectroscopy with the high position sensitivity and the detection efficiency. We demonstrated the capability to operate this detector as a reliable gamma-ray polarimeter by using polarized 847-keV gamma rays produced by the 56Fe\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{56}\ extrm{Fe}$$\\end{document}(p,p′γ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${ p},{ p'}\\gamma $$\\end{document}) reaction. By combining the experimental data and simulated calculations, the modulation curve for the gamma ray was successfully obtained. A remarkably high polarization sensitivity was achieved, compatible with a reasonable detection efficiency. Based on the obtained results, a possible future gamma-ray polarimetery is discussed.

Collimator design for gamma-ray cascade angular correlations in medical imaging

In recent decades, Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) have become workhorses of molecular imaging. The main drawback of these modalities is that they resort to statistical methods of image reconstruction, as the location of the individual nuclei emitting radiation is not accessible. To remedy this situation, we embarked on a project to introduce a new modality of nuclear medical imaging which exploits the non-collinear angular correlations of nuclear gamma-ray cascades subsequent to beta decays. This modality, if effective, determines the location of each decay nucleus. We have retrofitted the small animal PET assembly of RIKEN-Kobe (Japan) with tungsten+PLA (polylactic acid) collimators. The chosen material is inexpensive, amenable to three-dimensional (3D) printing, and has good photon attenuation properties. We included the collimator geometry in GATE (Geant4 Application for Tomographic Emission) simulations and developed algorithms for image reconstruction with medical isotope candidates viz., 111In and 43K. Our preliminary simulations show that data acquisition with a 2 MBq source for 900 s is sufficient to reproduce the source geometry with high resolution. This report summarizes our progress to date and the plans for the near future.

Wide-band X-ray and gamma-ray imaging of living mouse to reveal pharmacokinetics of At-211

Nuclear medicine therapy is a treatment method in which a radionuclide-labeled agent is selectively taken up by the lesion, and a tumor is directly irradiated. In particular, At-211, which is an alpha-ray-emitting nuclide and is expected to be highly effective with few side effects, has attracted attention in recent years. In actual treatment, real-time monitoring is required to confirm the dynamics of drug accumulation at the correct location and to estimate the exposure of normal tissues; therefore, accurate imaging technology is required. We used a hybrid Compton camera (HCC), which is capable of broadband imaging, from characteristic X-rays to nuclear gamma rays, to image mice treated with At-211 NaAt. Four HCCs were used to image the At-211 NaAt-injected mouse under anesthesia. As a result, we were able to observe 3D pharmacokinetics in the living mouse by using 79 keV X-rays, and the accumulation of At-211 NaAt in the stomach and thyroid. By implementing the BGO active shield, we also succeeded in visualizing the drug distribution of At-211 NaAt in the mouse using nuclear gamma rays of 570 keV for the first time.

Calculated Event Rates for Axion Detection via Atomic and Nuclear Processes

The possibility of detection of 5.5 MeV and 14.4 keV solar axions by observing axion-induced nuclear and atomic transitions is investigated. The presence of nuclear transitions between spin orbit partners can be manifested by the subsequent deexcitation via gamma ray emissions. The transition rates can also be studied in the context of radiative axion absorption by a nucleus. The elementary interaction is obtained in the context of the axion-quark couplings predicted by existing axion models. Then, these couplings will be transformed to the nucleon level utilizing reasonable existing models, which lead to effective transition operators. Using these operators, we calculate the needed nuclear matrix elements employing wave functions obtained in the context of the nuclear shell model. With these ingredients, we discuss possibilities of experimental observation of the axion-induced nuclear gamma rays. In the second part, we will examine the axion-induced production of X-rays (axion-photon conversion) or ionization from deeply bound electron orbits. In this case, the axion electron coupling is predicted by existing axion models; no renormalization is needed. The experimental signal is the observation of directly produced electrons and/or the emission of hard X-rays and Auger electrons, following the deexcitation of the final atom. Critical discussion is made on the experimental feasibility of detecting the solar axions by using multiton scale NaI detectors.

A new dead-time determination method for gamma-ray detectors using attenuation law

This study presents a new dead-time measurement method using the gamma attenuation law and generalized dead-time models for nuclear gamma-ray detectors. The dead-time of the NaI(Tl) detection system was obtained to validate the new dead-time determination method using very thin lead and polyethylene absorbers. Non-paralyzing dead-time was found to be 8.39 μs, and paralyzing dead-time was found to be 8.35 μs using lead absorber for NaI(Tl) scintillator detection system. These dead-time values are consistent with the previously reported dead-time values for scintillator detection systems. The gamma build-up factor's contribution to the dead-time was neglected because a very thin material was used.

Neutron activation analysis of Tibetan traditional medicinal pills at the VR-1 training reactor

The nuclear analytical methods provide the research techniques usually used in hard sciences such as physics, chemistry, engineering and technology, or natural sciences and technology, but it is very rare to use them in social sciences and humanities. The Czech Technical University (CTU) in Prague operates the VR-1 training reactor primarily focused on training students, nuclear engineering, reactor physics, and research; however, the utilization of this nuclear reactor has also been extended to humanities in recent years. In this direction, the research activities carried out at the reactor include the investigation of historical artefacts and testing of pharmaceutical and food industry samples. This contribution deals with the detailed study of traditional Tibetan medicinal pills by means of instrumental neutron activation analysis (NAA) at the VR-1 nuclear reactor. Three various kinds of Tibetan pills were irradiated by thermal neutrons (ϕ=2×109cm−2s−1) in the experimental vertical channel at maximum reactor power (80 W), and irradiated samples were analysed using the semiconductor HPGe detector; saturated activities were obtained by means of the nuclear gamma-ray spectrometry, and subsequently the composition of the pills was determined (qualitative and quantitative analysis). The presence of Au, K, Fe, Na, As, Sr, Sb, and Hg was revealed in studied samples. The results presented in this paper show clearly that the low-power research reactor VR-1 is excellent tool for the neutron activation analysis experiments.

First demonstration of portable Compton camera to visualize 223-Ra concentration for radionuclide therapy

Radionuclide therapy (RNT) is an internal radiation therapy that can selectively damage cancer cells. Recently, the use of alpha-emitting radionuclides was initiated in RNT owing to its dose concentration and short range. In particular, 223Ra is widely used for bone metastasis of prostate cancer. Despite its potential for clinical applications, it is difficult to determine whether a drug has been properly delivered to the target lesion. As such, we propose a new method of monitoring nuclear gamma rays promptly and simultaneously emitted from 223Ra as alpha decay using a high-sensitivity Compton camera. We first observed a small bottle of 223Ra solution with a total radioactivity of 0.56 MBq. The reconstructed image converged at the correct position with a position resolution of ∼20 mm at a plane 10 cm in front of the camera. Next, we observed a phantom consisting of three spheres with diameters ranging from 13 to 37 mm filled with 223Ra solution (9 kBq/mL) and then surrounded by a ∼20-cm layer of water. A three-dimensional (3D) image was constructed by rotating the Compton camera around the phantom. Images were then acquired from eight directions at 30-min intervals, respectively. Although the image resolution remained limited at 351 keV, three spheres were resolved at the correct position in the 3D image with their relative intensities. Thirdly, we observed the body of a patient for 10 min and reconstructed almost the same accumulation as the image acquired by a single-photon emission computed tomography (SPECT) system for 30 min. While the spatial resolution of the Compton camera was worse, DOI-CC obtained a wider image in a shorter time. Finally, we discuss current problems and plans for improving sensitivity and angular resolution for future clinical applications.

Neutron activation analysis of Tibetan traditional medicinal pills at the VR-1 training reactor

The nuclear analytical methods provide the research techniques usually used in hard sciences such as physics, chemistry, engineering and technology, or natural sciences and technology, but it is very rare to use them in social sciences and humanities. The Czech Technical University (CTU) in Prague operates the VR-1 training reactor primarily focused on training students, nuclear engineering, reactor physics, and research; however, the utilization of this nuclear reactor has also been extended to humanities in recent years. In this direction, the research activities carried out at the reactor include the investigation of historical artefacts and testing of pharmaceutical and food industry samples. This contribution deals with the detailed study of traditional Tibetan medicinal pills by means of instrumental neutron activation analysis (NAA) at the VR-1 nuclear reactor. Three various kinds of Tibetan pills were irradiated by thermal neutrons (ϕ=2×109cm−2s−1) in the experimental vertical channel at maximum reactor power (80 W), and irradiated samples were analysed using the semiconductor HPGe detector; saturated activities were obtained by means of the nuclear gamma-ray spectrometry, and subsequently the composition of the pills was determined (qualitative and quantitative analysis). The presence of Au, K, Fe, Na, As, Sr, Sb, and Hg was revealed in studied samples. The results presented in this paper show clearly that the low-power research reactor VR-1 is excellent tool for the neutron activation analysis experiments.

Edward L. Chupp (1927–2017)

This pioneer in high-energy solar physics devised instruments for observing solar and cosmic ray emissions with which he detected, for the first time, nuclear gamma rays from solar flares.

Study of dietary supplements compositions by neutron activation analysis at the VR-1 training reactor

The VR-1 training reactor operated by the Czech Technical University in Prague is utilized mainly for education of students and training of various reactor staff; however, R&D is also carried out at the reactor. The experimental instrumentation of the reactor can be used for the irradiation experiments and neutron activation analysis. In this paper, the neutron activation analysis (NAA) is used for a study of dietary supplements containing the zinc (one of the essential trace elements for the human body). This analysis includes the dietary supplement pills of different brands; each brand is represented by several different batches of pills. All pills were irradiated together with the standard activation etalons in the vertical channel of the VR-1 reactor at the nominal power (80W). Activated samples were investigated by the nuclear gamma-ray spectrometry technique employing the semiconductor HPGe detector. From resulting saturated activities, the amount of mineral element (Zn) in the pills was determined using the comparative NAA method. The results show clearly that the VR-1 training reactor is utilizable for neutron activation analysis experiments.

Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that “Electron Tracking Compton Camera” (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics.

Cosmic ray nuclei detection in the balloon borne nuclear emulsion gamma ray telescope flight in Australia (GRAINE 2015)

Nuclear emulsion plates for studying elementary particle physics as well as cosmic ray physics are very powerful tracking tools with sub-micron spatial resolutions of charged particle trajectories. Even if gamma rays have to be detected, electron-positron pair tracks can provide precise information to reconstruct their direction and energy with high accuracy. Recent developments of emulsion analysis technology can digitally handle almost all tracks recorded in emulsion plates by using the Hyper Track Selector of the OPERA group at NAGOYA University. On the other hand, the potential of time resolutions have been equipped by emulsion multilayer shifter technology in the GRAINE (Gamma Ray Astro-Imager with Nuclear Emulsion) experiments, the aims of which are to detect cosmic gamma rays such as the Vela pulsar stellar object by precise emulsion tracking analysis and to study cosmic ray particle interactions and chemical compositions. In this paper, we focus on the subject of cosmic ray nuclei detection in the GRAINE balloon flight experiments launched at Alice Springs, Australia in May 2015.

Cosmic ray nuclei detection in the balloon borne nuclear emulsion gamma ray telescope flight in Australia (GRAINE 2015)

Nuclear emulsion plates for studying elementary particle physics as well as cosmic ray physics are very powerful tracking tools with sub-micron spatial resolutions of charged particle trajectories. Even if gamma rays have to be detected, electron-positron pair tracks can provide precise information to reconstruct their direction and energy with high accuracy. Recent developments of emulsion analysis technology can digitally handle almost all tracks recorded in emulsion plates by using the Hyper Track Selector of the OPERA group at NAGOYA University. On the other hand, the potential of time resolutions have been equipped by emulsion multilayer shifter technology in the GRAINE (Gamma Ray Astro-Imager with Nuclear Emulsion) experiments, the aims of which are to detect cosmic gamma rays such as the Vela pulsar stellar object by precise emulsion tracking analysis and to study cosmic ray particle interactions and chemical compositions. In this paper, we focus on the subject of cosmic ray nuclei detection in the GRAINE balloon flight experiments launched at Alice Springs, Australia in May 2015.

Ozone Generation in Air during Electron Beam Processing

Ozone, the triatomic form of oxygen, can be generated by exposing normal diatomic oxygen gas to energetic electrons, X-rays, nuclear gamma rays, short-wavelength ultraviolet radiation (UV) and electrical discharges. Ozone is toxic to all forms of life, and governmental regulations have been established to protect people from excessive exposures to this gas. The human threshold limit values (TLV) vary from 60 to 100 parts per billion (ppb) in air, depending on the agency or country involved. Much higher concentrations can be produced inside industrial electron beam (EB) facilities, so methods for ozone removal must be provided. Equations for calculating the ozone yield vs absorbed energy, the production rate vs absorbed power, and the concentration in the air of an EB facility are presented in this paper. Since the production rate and concentration are proportional to the EB power dissipated in air, they are dependent on the design and application of the irradiation facility. Examples of these calculations are given for a typical EB process to cross-link insulated electrical wire or plastic tubing. The electron energy and beam power are assumed to be 1.5 MeV and 75kW.

The research stands on the basis of the typical gamma-spectrometric complex

Multifunctionality of typical gamma-spectrometric complexes, which should solve various tasks of applied nuclear gamma-ray spectrometry is considered. These tasks include:- defining nuclide and element composition of matter;- developing the system for determining metrological registration factors of gamma-radiation of bulk samples;- developing the background stabilization and reduction system;- developing the internal security system.The description of the developed and existing research stands that solve these tasks at the gamma-spectrometric complex of the Institute of Electron Physics of the NAS of Ukraine is given. It is shown that these systems act as autonomous research stands that typically exist as independent units.The fact of efficiency of multifunctionality of gamma-spectrometric complex allows to conclude on the possibility to implement functional completeness in the gamma-spectrometric complex as a system.Operation of research stands allows to make the process of improving gamma-spectrometric complex indicators in whole and in specific cases constant.Results are related to typical gamma-spectrometric complexes, which are in the majority. Therefore, our results can be used in practice in many analytical laboratories.

TRANSMISSION AND EMISSION OF SOLAR ENERGETIC PARTICLES IN SEMI-TRANSPARENT SHOCKS

While major solar energetic particle (SEP) events are associated with coronal mass ejection (CME)-driven shocks in solar wind, accurate SEP measurements reveal that more than one component of energetic ions exist in the beginning of the events. Solar electromagnetic emissions, including nuclear gamma-rays, suggest that high-energy ions could also be accelerated by coronal shocks, and some of those particles could contribute to SEPs in interplanetary space. However, the CME-driven shock in solar wind is thought to shield any particle source beneath the shock because of the strong scattering required for the diffusive shock acceleration. In this Letter, we consider a shock model that allows energetic particles from the possible behind-shock source to appear in front of the shock simultaneously with SEPs accelerated by the shock itself. We model the energetic particle transport in directions parallel and perpendicular to the magnetic field in a spherical shock expanding through the highly turbulent magnetic sector with an embedded quiet magnetic tube, which makes the shock semi-transparent for energetic particles. The model energy spectra and time profiles of energetic ions escaping far upstream of the shock are similar to the profiles observed during the first hour of some gradual SEP events.

Coherent control of the waveforms of recoilless γ-ray photons

The concepts and ideas of coherent, nonlinear and quantum optics have been extended to photon energies in the range of 10-100 kiloelectronvolts, corresponding to soft γ-ray radiation (the term used when the radiation is produced in nuclear transitions) or, equivalently, hard X-ray radiation (the term used when the radiation is produced by electron motion). The recent experimental achievements in this energy range include the demonstration of parametric down-conversion in the Langevin regime, electromagnetically induced transparency in a cavity, the collective Lamb shift, vacuum-assisted generation of atomic coherences and single-photon revival in nuclear absorbing multilayer structures. Also, realization of single-photon coherent storage and stimulated Raman adiabatic passage were recently proposed in this regime. More related work is discussed in a recent review. However, the number of tools for the coherent manipulation of interactions between γ-ray photons and nuclear ensembles remains limited. Here we suggest and implement an efficient method to control the waveforms of γ-ray photons coherently. In particular, we demonstrate the conversion of individual recoilless γ-ray photons into a coherent, ultrashort pulse train and into a double pulse. Our method is based on the resonant interaction of γ-ray photons with an ensemble of nuclei with a resonant transition frequency that is periodically modulated in time. The frequency modulation, which is achieved by a uniform vibration of the resonant absorber, owing to the Doppler effect, renders resonant absorption and dispersion both time dependent, allowing us to shape the waveforms of the incident γ-ray photons. We expect that this technique will lead to advances in the emerging fields of coherent and quantum γ-ray photon optics, providing a basis for the realization of γ-ray-photon/nuclear-ensemble interfaces and quantum interference effects at nuclear γ-ray transitions.

Assessment of Fuzzy Logic Radioisotopic Pattern Identifier on Gamma-Ray Signals with Application to Security

Analysis of acquired nuclear detector gamma-ray signals for recognition of present radioisotopic signatures is crucial to national security and security applications. Identification algorithms must be accurate and rapid. Artificial intelligence is a scientific field with a variety of tools suitable to implement automated processing of nuclear signals. The use of low resolution portable detectors to measure gamma-ray signals has found a wide use in security and safeguards applications. In this paper, the fuzzy logic based analysis methodology that has been previously developed is applied and assessed on a variety of nuclear signals obtained with a low resolution scintillation detector, and more particularly a sodium iodide (NaI) detector. Various types of fuzzy membership functions are employed and their performance is assessed with regard to the number of positive detections, misses, and false alarms. Furthermore, recorded results from the set of low resolution gamma ray signals are used to estimate the detection sensitivity for each membership function. Results demonstrate the overall effectiveness of the fuzzy logic based identifier, and consist of the main course for the assessment of each membership function. Furthermore, comparison of results designates the triangular membership function as the best membership shape for this type of detector signals.

Developing a method for soft gamma-ray Laue lens assembly and calibration

Laue lenses constitute a promising option for concentrating soft gamma rays with a large collection area and reasonable focal lengths. In astronomy they could lead to increased telescope sensitivity by one to two orders of magnitude, in particular for faint nuclear gamma-ray lines, but also for continua like hard X-ray tails from a variety of compact objects. Other fields like Homeland security and nuclear medicine share the same need for more sensitive gamma-ray detection systems and could find applications for gamma-ray focusing optics. There are two primary challenges for developing Laue lenses: the search for high-reflectivity and reproducible crystals, and the development of a method to accurately orient and fix the thousands of crystals constituting a lens. In this paper we focus on the second topic. We used our dedicated X-ray beamline and Laue lens assembly station to build a breadboard lens made of 15 crystals. This allowed us to test our tools and methods, as well as our simulation code and calibration procedure. Although some critical points were identified, the results are very encouraging, with a crystal orientation distribution lower than 10”, as required to build a Laue lens telescope dedicated to the study of Type Ia supernovae (30-m focal length). This breadboard lens represents an important step towards raising the technology readiness level of Laue lenses.

Characterization of barren, granitic soils from the Nubian Desert (SW Egypt) by 57Fe Mössbauer spectroscopy

Abstract 57Fe Mössbauer spectroscopy - a versatile technique involving the recoil-free, resonant absorption and emission of nuclear gamma (γ) rays by the iron-57 isotope in natural iron in solids - has been used to provide quantitative information about the mineral host, occupation sites and oxidation states of iron atoms in geological samples. This technique has been applied to the bulk chemistry of a barren soil (Soil A) derived from an aluminous-type granite and another barren soil (Soil B) derived from a sodic-type granite located ~ 100 kilometers apart in the Nubian Deseit in the currently hyper arid south-west of Egypt and which exhibit distinct chemical and mineral differences. The analyses indicate different mineral hosts for the iron in these samples, namely, vermiculite-chlorite plus some hematite in Soil A and hematite and goethite plus minor aegirines in Soil B. Each soil has distinct intensities of oxidized iron (89% for Soil A and 100% for Soil B) and these differences reflect changes in soil sources and processes.