Journal articles on the topic 'Lithium Protons Alpha rays'

Shocks that arise from baryonic in-fall and merger events during the structure formation are believed to be a source of cosmic rays. These "structure formation cosmic rays" (SFCRs) would essentially be primordial in composition, namely, mostly made of protons and alpha particles. However, very little is known about this population of cosmic rays. One way to test the level of its presence is to look at the products of hadronic reactions between SFCRs and the ISM. A perfect probe of these reactions would be Li. The rare isotope Li is produced only by cosmic rays, dominantly in ?? ? 6Li fusion reactions with the ISM helium. Consequently, this nuclide provides a unique diagnostic of the history of cosmic rays. Exactly because of this unique property is Li affected most by the presence of an additional cosmic ray population. In turn, this could have profound consequences for the Big-Bang nucleosynthesis: cosmic rays created during cosmic structure formation would lead to pre-Galactic Li production, which would act as a "contaminant" to the primordial 7Li content of metalpoor halo stars. Given the already existing problem of establishing the concordance between Li observed in halo stars and primordial 7Li as predicted by the WMAP, it is crucial to set limits to the level of this "contamination". However, the history of SFCRs is not very well known. Thus we propose a few model-independent ways of testing the SFCR species and their history, as well as the existing lithium problem: 1) we establish the connection between gamma-ray and Li production, which enables us to place constraints on the SFCR-made lithium by using the observed Extragalactic Gamma-Ray Background (EGRB); 2) we propose a new site for testing the primordial and SFCR-made lithium, namely, low-metalicity High-Velocity Clouds (HVCs), which retain the pre-Galactic composition without any significant depletion. Although using one method alone may not give us strong constraints, using them in concert will shed a new light on the SFCR population and possibly give some answers about the pressing lithium problem. .

Precision measurements by AMS of the fluxes of cosmic ray positrons, electrons, antiprotons, protons as well as their rations reveal several unexpected and intriguing features. The presented measurements extend the energy range of the previous observations with much increased precision. The new results show that the behavior of positron flux at around 300 GeV is consistent with a new source that produce equal amount of high energy electrons and positrons. In addition, in the absolute rigidity range 60–500 GV, the antiproton, proton, and positron fluxes are found to have nearly identical rigidity dependence and the electron flux exhibits different rigidity dependence.

Abstract. Ulysses, launched in October 1990, began its second out-of-ecliptic orbit in September 1997. In 2000/2001 the spacecraft passed from the south to the north polar regions of the Sun in the inner heliosphere. In contrast to the first rapid pole to pole passage in 1994/1995 close to solar minimum, Ulysses experiences now solar maximum conditions. The Kiel Electron Telescope (KET) measures also protons and alpha-particles in the energy range from 5 MeV/n to >2 GeV/n. To derive radial and latitudinal gradients for >2 GeV/n protons and alpha-particles, data from the Chicago instrument on board IMP-8 and the neutron monitor network have been used to determine the corresponding time profiles at Earth. We obtain a spatial distribution at solar maximum which differs greatly from the solar minimum distribution. A steady-state approximation, which was characterized by a small radial and significant latitudinal gradient at solar minimum, was interchanged with a highly variable one with a large radial and a small – consistent with zero – latitudinal gradient. A significant deviation from a spherically symmetric cosmic ray distribution following the reversal of the solar magnetic field in 2000/2001 has not been observed yet. A small deviation has only been observed at northern polar regions, showing an excess of particles instead of the expected depression. This indicates that the reconfiguration of the heliospheric magnetic field, caused by the reappearance of the northern polar coronal hole, starts dominating the modulation of galactic cosmic rays already at solar maximum.Key words. Interplanetary physics (cosmic rays; energetic particles) – Space plasma physics (charged particle motion and acceleration)

This paper studies the use of electron data from the Electron Proton Alpha Monitor (EPAM) on board the Advanced Composition Explorer (ACE) in the UMASEP (University of Málaga Solar particle Event Predictor) scheme [Núñez, Space Weather 9 (2011) S07003; Núñez, Space Weather 13 (2015)] for predicting well-connected >10 MeV Solar Energetic Proton (SEP) events. In this study, the identification of magnetic connection to a solar particle source is done by correlating Geostationary Operational Environmental Satellites (GOES) Soft X-Ray (SXR) fluxes with ACE EPAM electrons fluxes with energies of 0.175–0.375 MeV. The forecasting performance of this model, called Well-Connected Prediction with electrons (WCP-electrons), was evaluated for a 16-year period from November 2001 to October 2017. This performance is compared with that of the component of current real-time tool UMASEP-10, called here WCP-protons model, which predicts the same type of events by correlating GOES SXR with differential proton fluxes with energies of 9–500 MeV. For the aforementioned period, the WCP-electrons model obtained a Probability of Detection (POD) of 50.0%, a False Alarm Ratio (FAR) of 39% and an Average Warning Time (AWT) of 1 h 44 min. The WCP-protons model obtained a POD of 78.0%, a FAR of 22% and an AWT of 1 h 3 min. These results show that the use of ACE EPAM electron data in the UMASEP scheme obtained a better anticipation time (additional 41 min on average) but a lower performance in terms of POD and FAR. We also analyzed the use of a combined model, composed of WCP-electrons and WCP-protons, working in parallel (i.e. the combined model issues a forecast when any of the individual models emits a forecast). The combined model obtained the best POD (84%), and a FAR and AWT (34.4% and 1 h 34 min, respectively) which is in between those of the individual models.

The Alpha Magnetic Spectrometer (AMS-02) is a wide acceptance high-energy physics experiment installed on the International Space Station in May 2011 and operating continuously since then. With a collection rate of approximately 1.7 × 1010 events/year, and the combined identification capabilities of 5 independent detectors, AMS-02 is able to precisely separate cosmic rays light nuclei (1 ≤ Z ≤ 8). Knowledge of the precise rigidity dependence of the light nuclei fluxes is important in understanding the origin, acceleration, and propagation of cosmic rays. AMS-02 collaboration has recently released the precise measurements of the fluxes of light nuclei as a function of rigidity (momentum/charge) in the range between 2 GV and 3 TV. Based on the observed spectral behaviour, the light nuclei can be separated in three distinct families: primaries (hydrogen, helium, carbon, and oxygen), secondaries (lithium, beryllium, and boron), and mixed (nitrogen). Spectral indices of all light nuclei fluxes progressively harden above 100 GV. Primary cosmic ray fluxes have an identical hardening above 60 GV, of about γ = 0.12 ± 0.04. While helium, carbon and oxygen have identical spectral index magnitude, the hydrogen spectral index shows a different magnitude, i.e. the primary-to-primary H/He ratio is well described by a single power law above 45 GV with index -0.077 ± 0.007. Secondary cosmic ray fluxes have identical rigidity dependence above 30 GV. Secondary cosmic rays all harden more than primary species, and together all secondary-to-primary ratios show a hardening difference of 0.13 ± 0.03. Remarkably, the nitrogen flux is well described over the entire rigidity range by the sum of the primary flux equal to 9% of the oxygen flux and the secondary flux equal to 62% of the boron flux.

A cover for Scintag's six and twelve-position sample changers was designed and constructed to provide an inert atmosphere for samples during diffraction batch runs. The cover is equipped with inlet and outlet gas ports and fits over the top of the sample changer. Using dry nitrogen gas fed into the inlet of the cover, a sample of lithium bromide was protected from atmospheric moisture for greater than 18 h. The cover uses a thin Mylar window that gives greater than 95% transparency for copper K-alpha X-rays. The cover is a simple device that allows our lab to run multiple moisture-sensitive samples in a batch mode. The simple approach and materials used in the construction of the cover could be applied to other brands of powder diffractometers.

Boron neutron capture therapy (BNCT) is an anticancer modality realized through 10B accumulation in tumor cells, neutron irradiation of the tumor, and decay of boron atoms with the release of alpha-particles and lithium nuclei that damage tumor cell DNA. As high-LET particle release takes place inside tumor cells absorbed dose calculations are difficult, since no essential extracellular energy is emitted. We placed gold nanoparticles inside tumor cells saturated with boron to more accurately measure the absorbed dose. T98G cells accumulated ~50 nm gold nanoparticles (AuNPs, 50 µg gold/mL) and boron-phenylalanine (BPA, 10, 20, 40 µg boron-10/mL), and were irradiated with a neutron flux of 3 × 108 cm−2s−1. Gamma-rays (411 keV) emitted by AuNPs in the cells were measured by a spectrometer and the absorbed dose was calculated using the formula D = (k × N × n)/m, where D was the absorbed dose (GyE), k—depth-related irradiation coefficient, N—number of activated gold atoms, n—boron concentration (ppm), and m—the mass of gold (g). Cell survival curves were fit to the linear-quadratic (LQ) model. We found no influence from the presence of the AuNPs on BNCT efficiency. Our approach will lead to further development of combined boron and high-Z element-containing compounds, and to further adaptation of isotope scanning for BNCT dosimetry.

Cancer is a malignant tumor that destroys healthy cells. Cancer treatment can be done by several methods, one of which is BNCT. BNCT uses 10B target which is injected into the human body, then it is irradiated with thermal or epithermal neutrons. Nuclear reaction will occur between boron and neutrons, producing alpha particle and lithium-7. The dose is estimated by how much boron and neutron should be given to the patient as a sum of number of boron, number of neutrons, number of protons, and number of gamma in the reaction of the boron and neutron. To calculate the dose, the authors simulated the reaction with Monte Carlo N Particle-X computer code. A water phantom was used to represent the human torso, as 75% of human body consists of water. Geometry designed in MCNPX is in cubic form containing water and a cancer cell with a radius of 2 cm. Neutron irradiation is simulated as originated from Kartini research reactor, modeled in cylindrical form to represent its aperture. The resulting total dose rate needed to destroy the cancer cell in GTV is 2.0814×1014 Gy.s (76,38%) with an irradiation time of 1,4414×10-13 s. In PTV the dose is 5.2295×1013 Gy.s (19,19%) with irradiation time of 5.7367×10-13 s. In CTV, required dose is 1.1866×1013 Gy.s (4,35%) with an irradiation time of 2.5283×10-12 s. In the water it is 1.9128×1011 Gy.s (0,07%) with an irradiation time of 1,5684×10-10 s. The irradiation time is extremely short since the modeling is based on water phantom instead of human body.Keywords: BNCT, Dose, Cancer, Water Phantom, MCNPX

At present, at the Chornobyl NPP, the main building of the general-purpose storage system for spent nuclear fuel is the "wet type" storage of spent nuclear fuel number 1 (SNF-1), designed for receiving and storing spent nuclear fuel. In the light of the post-Fukushima events, the task of increasing the explosion and fire safety is a priority direction of the Chornobyl NPP operation. SNF-1 should meet the current requirements of safety regulatory documents, both under normal operating conditions and during emergency situations. Among the emergencies that are likely to occur in the SNF-1 repository, the occurrence and development of fire in the interior space of reinforced concrete blocks should be considered. This condition is conditioned by the extraordinary importance of this radiation-hazardous object. An explosion on SNF-1 may occur, mainly due to violation of the rules of operation and fire safety, as well as in the event of malfunctions or failures of individual systems. Thus, the problem of providing explosion and fire safety on SNF-1 is extremely relevant. The purpose of this work was to calculate the study of the formation of radionuclide hydrogen and its explosion in the premises of SNF-1. Methods. Measurement, comparison, system analysis, physical and mathematical modeling. Results. The main purpose of ensuring the explosion and fire danger of SNF-1 is to prevent the uncontrolled development of nuclear reactions and the spread of radiation. In the case of irradiation of water with low ionization radiation (for example, by gamma rays), the formation of radicals prevails, whereas for radiation with high ionization density (for example, α- and β-particles, splinters of division), the formation of molecules becomes more important. In a nuclear reactor where there are different types of radiation (γ-rays and high-energy protons formed during interaction with neutrons), both of these reactions take place simultaneously. Radicals H and OH are extremely reactive substances that are rapidly interconnected with the products formed as a result of the reaction. In the case of radioactive contamination of water in open containers filled with air and does not contain any active acceptors of OH radicals at appreciable concentrations, the observed hydrogen output is usually equal to 0.1-0.2 molecules/100 eV, which is significantly less the initial release of hydrogen formation. The larger the vessel in height, the greater the likelihood of this reaction compared with the likelihood of removing hydrogen from the liquid phase. But if we organize a non-equilibrium open system by forcing the removal of hydrogen from water, for example, by bubbling an inert gas, then the rate of its removal will exceed the rate of chemical decomposition. In this case, the hydrogen yield will increase and at the boundary it will be equal to the initial yield (unless, of course, there are no impurities of organic substances in the water, the radiolysis of which leads to the formation of molecular hydrogen). Therefore, to calculate the rate of formation of radio-hydrogen hydrogen in the reservoir basin water, the initial yield is used, that is, the maximum possible rate of hydrogen generation is calculated. Since the radioisotopes of water in the basin are mainly due to gamma radiation (beta and alpha radiation are delayed by the shells of the fuel assemblies and their energy is transferred to heat), the initial yield of the radiolytic formation of hydrogen is 0.45 molecules/100 eV. Under normal operation of SNF-1 in the basement area, the accumulation of radioactive hydrogen is eliminated at the expense of the work of the exhaust ventilation system of the surface area. The main factors determining the conditions for the formation of an explosive gas mixture based on hydrogen are the amount of stored spent fuel and the volume of water and air in the space where spent SNF is stored. The calculation is made from all sources of γ-radiation with a uniform distribution by source volume. For calculation, the main radionuclide composition of fuel in the lower beam of the fuel element was used in the case of holding 20 years and the burning depth of 24 MW×day/kg. The estimated value of the power absorbed by the water in terms of the total spent fuel, is I=1,098×1024 eV/(m3/h). The failures of the equipment of the complex of the storage system, caused by both external and internal events, which lead to failures of the ventilation system of the surface of the basin, can lead to the accumulation of radio-hydrogen hydrogen in the air volume of SNF-1 premises in the absence of ventilation systems. The break in the operation of the ventilation system, during which it is theoretically possible to achieve the lower limit of the explosive concentration of hydrogen, may be 12 days. In order to ensure explosion-proof safety in the pool of pools, it is necessary that the concentration of radiolytic hydrogen in the air be lower than the lower concentration limit of hydrogen explosion in a mixture with air (~ 4% of volume) with a stockrate of 10. Thus, the concentration of hydrogen should not exceed 0.4% of the permissible concentration of hydrogen in the air to exclude the formation of an explosive mixture with oxygen. For the case of placing all spent nuclear fuel (21284 units) in the compartments of the catchment pool 1-5, W(H2)=1.34 Hm3/h. Thus, the reasonable time of inactivity of the ventilation system will be no more than 7 days. In order to ensure that the concentration of radical hydrogen above the surface of the pool does not exceed 0.4% of the volume, the blowdown must be 250 times higher than the hydrogen generation rate, that is, the flow of air blown over the pool (ventilation) to ensure explosion-proof safety must be equal to g=250 W(H2), m3/year. The temperature of self-ignition of hydrogen in the presence of water vapor is 970 K, and the explosive properties of the hydrogen mixture are characterized by an outbreak of 4.12–75% of the volume. The degree of damage to building structures of the building of SNF-1 will be determined by the deformations and destruction that they received during the explosion of hydrogen. The formation of shock loads during an accidental explosion is directly determined by the number (volume) of stoichiometric ratios of hydrogen with the vapor and the limits of hydrogen ignition. Conclusion. Thus, the presented methodology for the estimation of the formation of radiolithic hydrogen and its possible explosion in the premises of SNF-1 allows, within the framework of a conservative approach, to conduct an explosion safety assessment and the consequences of an accidental explosion of radioactive hydrogen.

Abstract We report a discovery of bright blob-like enhancements of an Fe i K$\alpha$ line in the northwest and the middle of the supernova remnant (SNR) IC 443. The distribution of the line emission is associated with molecular clouds interacting with the shock front, and is totally different from that of the plasma. The Fe i K$\alpha$ line has a large equivalent width. The most plausible scenario for the origin of the line emission is that the MeV protons accelerated in the shell leak into the molecular clouds and ionized the Fe atoms therein. The observed Fe i K$\alpha$ line intensity is consistent with the prediction of a theoretical model in which MeV protons are accelerated along with GeV and TeV protons at the SNR.

AbstractElectrodiffusion (sweeping) is a post-growth treatment which allows the selective exchange of charge compensating intersititial ions in quartz. This technique is employed commercially to enhance the radiation hardness of the material used for precision oscillator crystals. Most as-grown quartz contains substitutional Al3+ with an interstitial alkali providing the charge compensation. Additional unidentified sites also trap protons to form the OH--growth defects responsible for several IR absorption bands. When thermally released from their trapping sites, the intersitials can migrate along the large c-axis channels. Therefore, if the sample is heated with an electric field applied along the c-axis, the ions can be swept out and replaced either by protons from the surrounding atmoshpere or by the desired alkal i from a salt electrode. In order to better understand the electrodiffusion, we are systematically investigating various aspects of the process. The apparent ionic conductivity data taken as the swept sample is cooled usually shows a curved log( T) vs 1000/T plot. The conductivity of H+ in is much less than that of the lithium or sodium. The activation energies at high temperatures tend to be lower than those found from the low temperature data. The exponential prefactors are considerably larger than the values predicted for a given aluminum content and reasonable estimates of the attack frequency and jump distance. It seems likely that an additional source of mobile ions is present. The peak or plateau observed during the warm-up period for air or hydrogen sweeping appears to be caused by the transition from conduction primari1y by a1ka1i s to conduction by protons.

AbstractThe radiation-induced displacement damage in yttrium borate (YBO3) is studied under X-ray, proton, and alpha irradiation. The photoluminescence (PL) was tested before and after irradiation to determine whether damage occurred and whether it could be queried by examining the PL spectrum. Two different dopants (cerium and europium) were used to activate the phosphor because each provides not only a different spectral signature but also a different mechanism for altering the spectrum between the pre- and post-PL measurements. X-rays, being primarily ionizing radiation, did not show any significant change between the pre and post measurements. We expected protons and alphas to damage the crystal structure, evidence of which could be seen in the change in the spectra before and after irradiation. However, we found no change under alpha exposure (3.6 × 1010 particles/cm2) and a significant change after proton exposure (5 × 1015 particles/cm2). While the material appears to be sensitive to protons, we cannot rule out its sensitivity to alphas because the alpha fluence may be too low to show an effect. This result provides strong indication that our materials are being damaged by particle radiation and that the radiation effects can be quantified.

AbstractLithium fluoride (LiF), one of the most pervasive alkali halides in optical device research, is routinely used in optical data storage and radiation protection. LiF crystals may contain different aggregate defects produced by several types of ionizing radiation, with the number of defects being proportional to the cumulative radiation dose. Stimulation of irradiated LiF detectors by heating or with blue light causes thermoluminescence (TL) or photoluminescence (PL), respectively. We developed a new PL reader equipped with a blue light-emitting diode for stimulation and a Hamamatsu photomultiplier for registering green emissions, dedicated to examining LiF detectors as well as more broadly investigating TL/PL emission from standard LiF detectors irradiated with gamma rays, 60 MeV protons and alpha particles. The results confirmed very high efficiency PL signal from alpha-irradiated LiF detectors corresponding to their low efficiency after gamma irradiation, and vice versa for TL readout. Combining the TL and PL readouts permits us to discriminate between how different kinds of radiation affect efficiency in LiF detectors.

AbstractThe degradation of the electrical performance of strained Si1-xGex epitaxial diodes by 220-MeV carbon particles is reported and compared with the effect of 20-MeV alpha rays and 20-MeV protons. The macroscopic damage is studied in a broad fluence range and for different Ge contents, ranging from 8 to 16 %. It is shown that the radiation damage of carbon irradiated diodes is about one order of magnitude larger than that for alpha ray irradiation, which can be explained by considering the difference of the nonionizing energy loss (NIEL). It is observed that the reverse current at a fixed bias increases with increasing fluence, while the rate of increase decreases with increasing fluence and/or Ge content. The fact that a close to square root dependence exists between the boron deactivation in the diode depletion region, derived from capacitance-voltage measurements and the reverse current increase suggests that the device degradation is dominated by radiation induced deep levels associated with interstitial boron complexes.

ABSTRACTSemiconductor materials have shown promise as ionizing radiation detection devices; however, to be used as a neutron detector, these materials require the addition of a nucleus with a large neutron absorption cross section (such as 10B or 6Li) to capture thermal neutrons and convert them into directly detectable particles. A semiconducting material that contains the neutron absorber within its regular stoichiometry has the potential to be more efficient than a layered or heterogeneous device at transferring the kinetic energy of the charged particle into the semiconducting material. One class of materials that has shown promise is Li-containing AIBIIIXVI2 compounds such as LiGaTe2, LiGaSe2, and LiInSe2. These materials have band gaps (2-3.5 eV) appropriate for room-temperature detection of thermal neutrons and would be the first detection material that is simultaneously, exquisitely sensitive to thermal neutrons; is insensitive to gammas; and acts as a direct conversion device. A vacuum distillation process provided high-purity lithium metal for AIBIIIXVI2 synthesis. Single crystals of sufficient bulk resistivity (grown for LiGaSe2 and LiInSe2LiInSe2) showed a distinct photo response as well as a clear response to alpha particles. Additional radiation measurements indicated that a 6 mm x 7 mm x 1.33 mm crystal of LiInSe2 detected gamma rays, and despite being composed of natural abundance lithium, responded to thermal neutrons as well.