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This paper describes the application of alpha-particle counting at a defined low solid angle and of high-resolution alpha-particle spectrometry at IRMM.These techniques are used in the frame of primary standardisations of radioact...
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This paper describes the application of alpha-particle counting at a defined low solid angle and of high-resolution alpha-particle spectrometry at IRMM.These techniques are used in the frame of primary standardisations of radioactive solutions or for the determination of nuclear decay data(alpha emission probabilities and energies,half-lives).Various technical aspects are discussed,such as source preparation,instrumentation,solid-angle calculations,peak shapes,fitting routines,bias of least-squares methods,off-line stability corrections,simulation of energy loss,uncertainties.The presented algorithms may also be useful for routine alpha-particle spectrometry,in particular for the assessment of its uncertainty budget.
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The mechanism of propagation of hadronic states in the medium is a key point for understanding particle-nucleus and nucleus-nucleus scattering at high energies. We have investigated the propagation of a baryon in the exclusive pro...
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The mechanism of propagation of hadronic states in the medium is a key point for understanding particle-nucleus and nucleus-nucleus scattering at high energies. We have investigated the propagation of a baryon in the exclusive process A(e, e'p)B in few-nucleon systems using realistic nuclear wave functions and Glauber multiple scattering theory both in its original form and within a generalized eikonal approximation. New results for the processes He-3(e, e'p)H-2 and He-4(e, e'p)H-3 are compared with data recently obtained at the Thomas Jefferson Laboratory, (JLAB).
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The International Commission on Radiation Units and Measurements (ICRU) published Report No. 49, Stopping Powers and Ranges for Protons and Alpha Particles, in 1993. Since the report shows only limited comparisons to experimental ...
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The International Commission on Radiation Units and Measurements (ICRU) published Report No. 49, Stopping Powers and Ranges for Protons and Alpha Particles, in 1993. Since the report shows only limited comparisons to experimental data, this Commentary discusses limits on the accuracy of its tables. Some of the stopping tabulations appear to have unusual variations for high energies (>1 MeV/nucleon) of the order of 2-4%, while the lower energies have possible errors of 10-20% for those targets which were not fitted with new data.
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Alpha-particle counting at a defined solid angle (DSA) is one of the most accurate methods used in the primary activity standardization of alpha-particle emitting radionuclides. The important features of the technique are geometri...
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Alpha-particle counting at a defined solid angle (DSA) is one of the most accurate methods used in the primary activity standardization of alpha-particle emitting radionuclides. The important features of the technique are geometrically calculated efficiency and low background energy spectra. This paper describes measurement conditions of the DSA counter installed at Turkish Atomic Energy Authority - Sarayk?y Nuclear Research and Training Center (TAEK-SANAEM) and source preparation apparatus. Details of source preparation, preliminary work of measurement and solid angle calculations are explained. The standardization of the activity of241Am sources with detailed uncertainty analysis is reported as part of a validation of the method.
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In a paper presented in the Proceedings of the 19th World Conference of the INTDS, 1998, the results of a blind comparison between groups at NIST and the IRMM showed excellent agreement in characterization of actinide targets by a...
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In a paper presented in the Proceedings of the 19th World Conference of the INTDS, 1998, the results of a blind comparison between groups at NIST and the IRMM showed excellent agreement in characterization of actinide targets by alpha-particle counting with low solid-angle geometry. At that time the most accurate NIST results estimated an uncertainty of 0.03 % for the solid-angle determination. The NIST Neutron Physics Group now has improved the accuracy of its solid-angle determination by about a factor of 4, based on an improved aperture design, improved metrology, and comparisons among independent metrology techniques at NIST. Applications of this improved technology are expected to include improved NIST measurements of the free neutron lifetime and a recalibration of the NIST standard for neutron emission rate, NBS-I.
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The majority of patients with late stage castration-resistant prostate cancer (CRPC) develop bone metastases that often result in significant bone pain. Therapeutic palliation strategies can delay or prevent skeletal complications...
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The majority of patients with late stage castration-resistant prostate cancer (CRPC) develop bone metastases that often result in significant bone pain. Therapeutic palliation strategies can delay or prevent skeletal complications and may prolong survival. An alpha-particle based therapy, radium-223 dichloride (RaCl2), has been developed that delivers highly localized effects in target areas and likely reduces toxicity to adjacent healthy tissue, particularly bone marrow. Radiation safety aspects were evaluated for a single comprehensive cancer center clinical phase 1, open-label, single ascending-dose study for three cohorts at 50, 100, or 200 kBq kg-1 body weight. Ten patients received administrations, and six patients completed the study with 1 y follow-up. Dose rates from patients administered Ra dichloride were typically less than 2 μSv h-1 MBq-1 on contact and averaged 0.02 μSv h-1 MBq-1 at 1 m immediately following administration. Removal was primarily by fecal excretion, and whole body effective half-lives were highly dependent upon fecal compartment transfer, ranging from 2.5-11.4 d. Radium-223 is safe and straightforward to administer using conventional nuclear medicine equipment. For this clinical study, few radiation protection limitations were recommended post-therapy based on facility evaluations. Specific precautions are dependent on local regulatory authority guidance. Subsequent studies have demonstrated significantly improved overall survival and very low toxicity, suggesting that Ra may provide a new standard of care for patients with CRPC and bone metastases.
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A compact in-house alpha particle source has been developed and fully characterized. The irradiation source is a large area, 25 cm2, 5.4 MeV average energy 241Am source, above which a Mylar dish containing a monolayer of target ce...
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A compact in-house alpha particle source has been developed and fully characterized. The irradiation source is a large area, 25 cm2, 5.4 MeV average energy 241Am source, above which a Mylar dish containing a monolayer of target cells can be placed at defined positions. The source uniformity, flux, particle energy and dose rate were determined experimentally. The dose rate to the nucleus at the closest position was 1.57 Gy/min. Furthermore, a 3D printed collimator was tested and found to improve the uniformity of the energy spectra of particles reaching the target. For validation, prostate PC-3 cells were irradiated in our experimental setup with absorbed doses up to 2 Gy and for reference compared with cells irradiated with conventional X-rays with doses up to 8 Gy. The Relative Biological Effectiveness for alpha particles at 10% survival was 3.66 +/- 0.40 agreeing with previously published data. Data presented here show the feasibility of utilising a low-cost alpha-irradiation source for accurate in vitro assays to better understand the radiobiological effects of high LET alpha particles.
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Gas-like α-cluster states are investigated in light Λ hypernuclei. The α condensate-type microscopic cluster model wave function is introduced to describe Λ hypernuclei. In particular, the analogous state to the famous Hoyle s...
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Gas-like α-cluster states are investigated in light Λ hypernuclei. The α condensate-type microscopic cluster model wave function is introduced to describe Λ hypernuclei. In particular, the analogous state to the famous Hoyle state, the second ~(0 +) state in ~(12)C, is investigated in ~(13) _ΛC, with the use of the new type wave function. The Hoyle state is known to have a gas-like 3α cluster structure, where the 3α particles are condensed into an identical S orbit. The second 1/~(2 +) state in ~(13) _ΛC is shown to have the 3α + Λ structure. A strong shrinkage effect by adding the Λ particle is seen for the state, reducing the rms radius from 3.8 fm in the Hoyle state to 2.8 fm. In spite of the shrinkage effect, the α condensate fraction of about 60% still survives, though it is reduced by about 20% from the Hoyle state.
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The reported loss of α-particles in the 14 MeV tagged neutron generators has been investigated using two neutron generators equipped with α-particle counters and two neutron detectors. One neutron detector was put right in the m...
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The reported loss of α-particles in the 14 MeV tagged neutron generators has been investigated using two neutron generators equipped with α-particle counters and two neutron detectors. One neutron detector was put right in the middle of the tagged neutron cone and another one was put outside the cone. By measuring the difference between double (neutron-neutron) and triple (α-neutron-neutron) coincidences it is possible to deduce the α-particle loss since the number of triple coincidences should be equal to the number of double coincidences. In all measurements performed a deficit of triple with respect to double coincidences has been observed. This deficit was smallest for the threshold of α-particle Constant Fraction Discriminator (αCFD) being 0 and maximum allowed voltage of α-particle detector being -1.7 kV. The smallest measured deficit value was equal to 13 ± 1%. From the observed results it was concluded that the deficit was due to a number of non-detected α-particles that loose sufficient quantity of energy while traveling to the detector because of collisions with particles present in the neutron tube and/or in the tritium target. These α-particles will not be detected as they fall under the threshold of αCFD discriminator. Magnetic fields present in the system worsen the situation since they are forcing α-particles to travel larger distances because of toroidal movement and undergoing additional collisions. Tagged neutron technique has many kind of applications and it is particularly important for high accuracy nuclear cross-sections measurements when α-particles losses must be carefully assessed.
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