[en] We investigated a thermalization of neutrons, which were produced by an accelerator in a concrete room, by experiments and calculations. It was clarified that the widely used simple empirical formula phi th = c x Q/S, where Q is the neutron source intensity and S is the total surface area of a room, gives about one-third the underestimated value to our experimental and calculated results and the coefficient, c, is not a constant, but dependent on the source neutron energy

[en] Recently, high-energy heavy ions have been used in various fields of nuclear physics, radiotherapy, material physics, and so on. Safety design consideration for heavy ion accelerator facilities requires nuclear reaction cross section data for high-energy ions to estimate the radioactivities induced in the accelerator components and in the shielding materials. We irradiated 230 and 100 MeV/nucleon Ar, Ne, C, He, p ions onto a Cu target to investigate the projectile dependency of induced radioactivities of spallation products. Irradiation experiments were performed at HIMAC (Heavy Ion Medical Accelerator in Chiba), National Institute of Radiological Sciences, Japan. The Cu target was composed of a stack of Cu plates, and C, Al, Cr, Fe, Ni, Cu, Pb samples were inserted between the Cu plates. The samples put on the front surface of Cu target are for measurement of reaction cross sections and the mass-yield distribution of produced nuclides. The samples inserted between the Cu plates are for measurement of the spatial distribution of the residual activities of produced nuclides in the Cu target. The thickness of Cu target is larger than the range of the projectile beam. After irradiation, we measured the gamma-ray spectra from samples with a HPGe detector. We obtained the spatial distribution of the residual activities of nuclides produced in these samples and the mass-yield distribution of nuclides produced on the surface of Cu target. For example, we could find the maximum number of 44 radioactive nuclides from ₆₅ Zn down to ₇Be in Cu sample. The results show that the dependence of the mass-yield distribution and the spatial distribution of the residual activities on the projectile mass varies with the mass number difference between the sample nuclide and the produced nuclide. These experimental results were compared with the Monte Carlo calculation

[en] Neutron activation cross sections of C, Na, Mg, Al, Si, Ca, V, Cr, Mn, Cu, Zn and Au, which are mostly constituents of accelerator and building materials, in the energy range of 10 to 40 MeV, by using semi-monoenergetic neutrons from the Be(p,n) reaction. A proton beam of energies of 20, 22.5, 25, 27.5, 30, 32,5, 35, 37.5 and 40 MeV hits the 1-mm and 2-mm thick Be targets which are backed by the water coolant. The induced gamma-ray activities of the irradiated samples were measured with a pure Ge detector and of long-lived ²⁶Al were done by accelerator mass spectrometry. The activation cross section data could be obtained by unfolding technique. (author)

[en] Two simple target systems which produce intense semi-mono-energetic neutron fields for activation experiments were made by using proton beams of energy up to 40 MeV. One consists of a Be target and a water coolant, and the other consists of a ⁷Li target and a carbon beam stopper. The p-Be neutrons were measured by an NE-213 scintillator with an aid of the unfolding method, and the p-Li neutrons were precisely measured by using the TOF technique. Activation experiments were performed at the p-Be neutron field with natural Na, Mg, Al, Si, Ca, V, Cr, Mn, Cu, Zn and Au samples for 9 proton energies between 20 and 40 MeV. Production rates of 32 radioisotopes were measured, and converted into excitation functions. The accuracy of these procedures were examined

[en] This paper discusses an intense semimonoenergetic neutron field which was made using a simple beryllium target system bombarded by protons of nine different energies between 20 and 40 MeV. Natural sodium, aluminum, vanadium, chromium, manganese, copper, zinc, and gold samples were irradiated at this field, and gamma rays from the samples were observed by a germanium detector. The production rates of 17 radionuclides were obtained for the nine different neutron fields, and the excitation functions of these 17 reaction channels of ²³Na(n,2n)²²Na, ²⁷Al(n,α)²⁴Na, ⁵¹V(n,α)⁴⁸Sc, ⁵¹V(n,p)⁵¹Ti, ⁵⁰Cr(n,3n)⁴⁸Cr, ⁵⁰Cr(n,2n)⁴⁹Cr, ⁵⁵Mn(n,pα)⁵¹Ti, ⁵⁵Mn(n,4n)⁵²Mn, ⁵⁵Mn(n,2n)⁵⁴Mn, ⁶³Cu(n,3n)⁶¹Cu, ⁶³Cu(n,2n)⁶²Cu, ⁶⁵Cu(n,p)⁶⁵Ni, ⁶⁴Zn(n,t)⁶²Cu, ⁶⁴Zn(n,3n)⁶²Zn, ⁶⁴Zn(n,2n)⁶³Zn, ¹⁹⁷Au(n,4n)¹⁹⁴Au, and ¹⁹⁷Au(n,2n)¹⁹⁶Au were obtained for neutron energies up to 40 MeV by using the SAND-II and the NEUPAC unfolding codes and also least-squares fitting. The initial guess value for these methods was obtained primarily from calculations of the ALICE/LIVERMORE82 code

[en] The reaction cross sections of spallation products in a Cu target by 230 MeV/u C and Ne ions were obtained. Irradiation experiments were performed at HIMAC (Heavy Ion Medical Accelerator in Chiba), National Institute of Radiological Sciences. Gamma-ray spectra from activation samples were measured with a HPGe detector. From the gamma-ray spectra, we obtained the variation of reaction cross sections of Cl-38, Cr-49, Mn-55, Cu-60, Cu-61 and Co-62m in Cu sample with Cu target thickness, and compared it with the experimental data by Kim et al.. The results showed that the dependence of the cross sections to the projectile mass is very small for the same projectile energy per nucleon. (author)

[en] Safety design consideration for the accelerator facilities requires reaction cross section data for high-energy ions to estimate the radioactivities induced in the accelerator components and in the shielding materials. Therefore we irradiated 230 MeV/nucleon p, He, C, and Ne ions onto a target, and investigated the projectile dependency of induced radioactivities of spallation products. Irradiation experiments were performed at HIMAC (Heavy Ion Medical Accelerator in Chiba) of National Institute of Radiological Sciences, Japan. The target was composed of a stack of 100 mm x 100 mm x 5 mm Cu plates, and C, Al, Cr, Fe, Ni, Cu and Pb samples were inserted between the Cu plates. After irradiation, we measured the gamma-ray spectra from samples with HPGe detectors. The production rates of radionuclides in samples which were identified from the gamma ray spectra and the decay curves were estimated after being corrected for the coincidence-summing effect on the peak efficiency of the HPGe detectors. From the reaction rates we have obtained reaction cross sections of ³⁸Cl, ⁴⁹Cr, ⁵⁶Mn, ⁶⁰Cu, ⁶¹Cu and ^62mCo produced by 230-MeV/nucleon C and Ne ions. These cross sections are almost equal for these two projectile ions, which imply the independence of projectiles having the same energy per nucleon. Protons and He ions experiments have already performed and those data are under analysis. (author)

[en] Irradiation experiments were performed at the HIMAC (heavy ion medical accelerator in Chiba) facility, National Institute of Radiological Sciences, Japan. The radioactivity distributions of spallation products in a thick Cu target were obtained by irradiating 230 and 100 MeV/nucleon Ne, C, He, p and 230 MeV/nucleon Ar ions. The gamma-ray spectra from thin irradiated samples of C, Al and Cu inserted into a Cu target were measured with a HPGe detector. From the gamma-ray spectra, we obtained the spatial distribution of radioactive yields of spallation products of about 40 nuclides in Cu sample in the Cu target. Our results agree with other experimental data. We also calculated the spatial distribution of residual radioactivities in the Cu target by the PHITS (particle and heavy-ion transport code system) code and compared with measured results. The PHITS code provides good results on residual activity calculations. (orig.)

[en] We have carried out a nuclear magnetic resonance study on pseudo-binary spinel compounds (Cu_xCo_1-x)Co₂S₄ with x=0-1.0 to deduce the varied impact of variations in the antiferromagnetic (AF) spin correlation and density of states (DOS) that can clearly define the combination of magnetism and superconductivity in the system. The Curie-Weiss-type behaviour of the Knight shift K for both ⁵⁹Co and ⁶³Cu on the tetrahedral A site and the temperature-independent K for ⁵⁹Co on the octahedral B site indicate that the magnetism of the system originates from 3d bands associated with the transition-metal elements on the A site. With the Cu substitution x for Co on the A site, the negative Weiss temperature θ deduced from the K data initially decreases, takes a deep minimum around x=0.7 followed by a rapid increase for x→1. For the compounds with x≤0.3 and x>0.8, the nuclear spin-lattice relaxation rate T₁^-1 for the nuclei on both A and B sites has a T^1/2 dependence at high temperatures, which is characteristic of three-dimensional itinerant weak antiferromagnets. In the Cu-rich region (x>0.7) the compounds transform into a superconducting state below T_S with no long-range magnetic ordering. From a T₁^-1 data analysis, we find that the increase of T_S correlates not only with the development of the AF spin correlation but also with the significant increase in the DOS at the Fermi level of the 3d bands N_d(E_F) associated with Co on the B site. T₁^-1 in the superconducting state of CuCo₂S₄ (T_S = 4.4 K), measured for ⁵⁹Co on the B site utilizing the pure quadrupole resonance spectrum, has a coherence peak followed by an exponential decrease, indicating that CuCo₂S₄ is an s-wave superconductor with an energy gap of 2 Δ=4.14k_BT_S. We conclude that the appearance of superconductivity for the compounds in the Cu-rich region originates from the large increase in N_d(E_F) associated with Co on the B site, and the development of the AF spin correlation originates from the increase in N_d(E_F) associated with Cu on the A site. (author)

[en] We have measured the production cross sections of long-lived isotopes, ¹⁰Be(1.5x10⁶ y) by ¹⁴N(n, pα)¹⁰Be, ¹⁴C(5.7x10³ y) by ¹⁶O(n, ³He)¹⁴C and ²⁶Al(7.2x10⁵ y) by ²⁷Al(n, 2n)²⁶Al and ^natSi(n, pxn)²⁶Al reactions in the energy range of 10 to 40 MeV. Vanadium nitride (VN) for ¹⁴N, quartz plate (SiO₂) for ¹⁶O and ^natSi, silicon plate for natural Si and aluminum foils for ²⁷Al were irradiated with semi-monoenergetic p-⁹Be and p-⁷Li neutrons at several proton energies of 20 to 40 MeV using the AVF cyclotron. The activities of the irradiated samples have been measured by the accelerator mass spectrometry system using the internal beam monitor method which has been equipped at the tandem Van-de-Graaf accelerator. The excitation functions of these reactions were obtained from the neutron energy spectrum and the measured number of atoms. (orig.)