Heat capacity measurements on irradiated and non-irradiated Mo3Ge and Mo5Ge3

We have measured the heat capacity of irradiated and non-irradiated Mo₃Ge and Mo₅Ge₃ in the temperature range ≈ 1.6 to 10 K. An irradiation of 2.2 × 10¹⁹ neutrons cm^-2 results in an increase in the superconducting transition temperature T_c from < 1.6 K in the non-irradiated state to ～ 4 K after irradiation for Mo₃Ge and a corresponding change from < 1.6 K to ～ 3 K for Mo₅Ge₃. Our analysis shows that this change in T_c is not accompanied by a change in the electronic density of states (within experimental error) but rather a decrease in the Debye temperature from 392 to 322 K for Mo₃Ge and 377 to 320 K for Mo₅Ge₃.     

Pac studies of neutron irradiated Li2HfO3

The influence of defects, created in the reaction⁶Li (n,α)³H on the perturbed angular correlation (PAC) of 133–482 keV cascade of¹⁸¹Ta in Li HfO₃ has been studied. Two different types of defects were identified. Its concentration remains constant during the isochronal annealing up to 300°C. 10 min annealing at 350°C leads to its disappearing.     

Levels of188Os populated by thermal neutron capture

Direct and coincidence gamma spectroscopy has been applied to the reaction¹⁸⁷Os(n, γ)¹⁸⁸Os. A neutron binding energy of 7,989.3±0.3 keV is deduced and a level scheme is established. The experimental level energies andB(E2) ratios are compared to calculations in the framework of the Interacting Boson Model.     

Tunnel spectroscopy on neutron irradiated Pb

We have studied the properties of superconducting Pb junctions after neutron irradiation at low temperatures. The predicted low frequency vibrational mode of the Frenkel defects could not be observed. New structures introduced by the irradiation can be explained by new tunneling processes.     

Absorption measurements in neutron irradiated silicon

Silicon samples have been neutron irradiated at 76 °K with fluences sufficient to allow measurement of the 1.7 μ divacancy band at 76 °K. The growth of the divacancy concentration and the recovery of the edge absorption were studied as a function of annealing temperature between 76 °K and 550 °K. Immediately after irradiation the divacancy concentration is about 25 per cent of its maximum value which is attained at 330 °K, the temperature at which the divacancies begin to anneal out. Increases in the 1.7 μ band intensity and recovery of the edge absorption can also be achieved at 76 °K by illuminating the sample with intense sub-bandgap light or white light. The experimental results suggest a neutron-induced cluster model in which the cluster is a vacancy-rich region whose annealing characteristics are controlled by the liberation and motion of vacancies. The injection effects can be explained by analogy to the charge state dependent mobility of the Si vacancy.     

Raman scattering of neutron irradiated 6H-SiC

Confocal micro-Raman spectroscopy was preformed to investigate the structural damage of SiC neutron irradiated with the fluences of 1.72×10¹⁹ and 1.67×10²⁰ n/cm². In addition to characteristic peaks, several additional signals related to Si–Si, Si–C, and C–C vibration modes were monitored. The vibration mode associated with C_SiV _C complexes was identified to be the unambiguous peak at 575 cm^?1 which appears initially in the sample post-irradiation annealed at 800 °C. The defect-induced phonon confinement effect results in an asymmetric broadening with a low-frequency tail of the optical phonon peaks. The sigmoidal thermal recovery behavior of the optical phonon frequencies indicates that the reduction of FLO_0/6–FTO_2/6 splitting originates mainly from the isolated vacancies and interstitials.     

The paramagnetic susceptability of neutron irradiated V3Ge single crystals

The paramagnetic susceptibility χ of V₃Ge single crystals was measured in the temperature range from 10 K to 350 K after irradiation with neutron fluences of $\text{(0.3?20) × 10}{}^{18}\text{n}\text{cm}{}^2\text{(E>1}\text{MeV}\text{)}$. Unirradiated crystals show a flat maximum at T=65±6 K, which disappears at high neutron doses. The temperature dependence and the absolute values of χ are continuously reduced by increasing neutron doses. This behaviour can be understood by the models of high density of states (DOS) proposed for A15 materials confirming the assumption that a sharp peak in the electronic density of states exists which is lowered and broadened by irradiation induced defects.     

Magnetic properties of neutron irradiated RPV steel

The neutron irradiated reactor pressure vessel (RPV) steels at various dose of 0–10¹⁸ n/cm² have been studied with Mössbauer, x-ray diffraction, and VSM. The Mössbauer data shows that the value of magnetic hyperfine field of Fe atom that exist at martensite is 330 kOe at site 1 and 305 kOe at site 2. At room temperature, the total absorption area of Mössbauer spectra with respect to irradiation of neutron is constant for the dose of 0–10¹⁶ n/cm², while over the dose of 0–10¹⁷ n/cm² the absorption area decreases rapidly. But the doublet area for the dose of 0–10¹⁶ n/cm² is constant, while over the dose of 10¹⁷ n/cm² it increases with increasing the fluence level of neutron. The coercivity and remanence of the neutron irradiated samples do not change significantly. But the maximum induction decreases by 5% at 10¹⁸ n/cm², compared with that of the as-received sample.     

EPR study of neutron irradiated Ge-S glasses

The results of EPR measurements on neutron irradiated Ge-S glasses doped by Mn are presented. It has been found that the integrated neutron flux from 1·1 × 10¹⁵ n. cm^–2 to 1·5× × 10¹⁷n. cm^–2 has no detectable effect on the nearest neighbour surroundings of Mn²⁺ probing ions but increases the intensity of all EPR lines. A new EPR line was detected in Mn-doped Ge-S glasses irradiated with the highest neutron dose of 1·5 × 10¹⁷ n. cm^–2.     

Paramagnetic centers in neutron irradiated glassy semiconductors

EPR was used for investigation of neutron irradiated glassy semiconductors (E_n = 2 MeV). It was shown that the neutron irradiation causes an increased number of unpaired spins: EPR signal was detected in glassy semiconductors which have not exhibited any signal before irradiation. A possible interpretation of the formation of paramagnetic centers due to neutron irradiation is suggested.     

X-ray emission spectra and electron structure of neutron irradiated V3Si

The results of the X-ray VKβ₅ emission spectra of V₃Si irradiated with fast neutrons are reported. A comparison with the spectrum for unirradiated V₃Si as well as with cluster calculations suggested that the changes observed in the electron structure of irradiated V₃Si result from antisite defects and inhomogeneous atomic distribution.     

Stage II recovery of thermal neutron irradiated copper

Recovery stages at 65 K, 125 K and 220 K are discussed. The 220 K stage which seems to shift to lower temperature with increasing dose could be resolved into two substages at ～200 K and 220 K with dose dependent relative heights.     

Microstructural analysis of neutron irradiated titanium and rhenium

The defect structure in α-titanium and rhenium irradiated with neutrons at 0.4T _m (T _m = absolute melting temperature) has been analyzed using transmission electron microscopy. In rhenium, the vacancies agglomerate into voids whereas in titanium, vacancy dislocation loops lying on the prism planes are the only vacancy type defects observed. In both metals, dislocation segments and network fragments are the main evidence of interstitial type defects. The presence of dislocation loops rather than voids in titanium irradiated at this temperature is an anamalous result when compared to results on other similarly irradiated pure metals. Possible explanations for the preferential formation of loops rather than voids in the titanium are discussed.     

Absence of voids in fast neutron irradiated zirconium by small angle neutron scattering

Abstract

The aim of this research was to resolve a difference of opinion in the literature on the presence of voids in fast neutron irradiated zirconium. There is a great interest in the study of zirconium, since zirconium and its alloys are used extensively in modern power reactors, for example in the fuel rods as a containment material for enriched uranium. A polycrystalline sample of zirconium was irradiated in the HERALD reactor at 40°C with 10²⁰ fast neutrons per cm^?2. The neutron scattering from irradiated and unirradiated standard samples was studied over a wide Q range from 0.001 to 1.12 Å^?1 on a D11 Spectrometer at the ILL (France). The defect cross-section (the difference between the scattering of the standard zirconium crystal and irradiated crystal) was nearly flat as a function of Q (momentum transfer vector) with an average value of 8.5 mb/Str/atom. This indicates a point defect concentration of about 1.8%. Thus the absence of any small angle (Q dependent) defect scattering indicates that large damage regions (e.g. voids) are not produced in zirconium by fast neutron irradiation.     

Polarizing neutron by light‐irradiated graphene

We study the spin orientation of the neutron scattered by light‐irradiated graphene and calculate the average value of spin z‐component of the neutron in terms of a generating functional technique. Our calculation results indicate that there is a remarkable neutron polarization effect when a neutron penetrates graphene irradiated by a circularly polarized light. We analyse the dynamical source of generating this effect from the aspect of photon‐mediated interaction between the neutron spin and valley pseudospin. By comparing with the polarization induced by a magnetic field, we find that this polarization may be equivalent to the one led by a magnetic field of several hundred Teslas if the photon frequency is in the X‐ray frequency range. This provides an approach of polarizing neutrons.

     

Raman scattering from amorphous zones in neutron irradiated silicon

A Raman scattering study of neutron irradiated silicon is presented for the first time. We have observed features in the Raman spectrum arising from amorphous zones produced in the bulk of the sample due to neutron induced defects. We relate these first order Raman modes to the crystalline vibrational density of states averaged over the Brillouin zone.     

Accelerated oxygen precipitation in fast neutron irradiated Czochralski silicon

Annealing effect of the oxygen precipitation and the induced defects have been investigated on the fast neutron irradiated Czochralski silicon （CZ-Si） by infrared absorption spectrum and the optical microscopy. It is found that the fast neutron irradiation greatly accelerates the oxygen precipitation that leads to a sharp decrease of the interstitial oxygen with the annealing time. At room temperature （RT）, the 1107cm^-1 infrared absorption band of interstitial oxygen becomes weak and broadens to low energy side. At low temperature, the infrared absorption peaks appear at 1078cm^-1, 1096cm^-1, and 1182cm^-1, related to different shapes of the oxygen precipitates. The bulk microdefects, including stacking faults, dislocations and dislocation loops, were observed by the optical microscopy. New or large stacking faults grow up when the silicon self-interstitial atoms are created and aggregate with oxygen precipitation.     

The atkermal stress component in neutron irradiated mild steel

Abstract

The temperature dependence of the tensile lower yield stress of an annealed aluminium grain size controlled mild steel has been investigated in the range 23–250 °C and at a strain rate of 1.67 × 10^?4 sec^?l before and after neutron irradiation to 2.3 × 10¹⁸ n/cm² (fission). The yield stress of the irradiated steel decreases with increasing temperature due to thermal activation of the radiation damage and is predicted to reach asymptotically that of the unirradiated steel at ～285 °C; the maximum test temperature was below that at which thermal annealing of the damage occurs. This implies that the athermal stress component due to irradiation is zero and hence there is negligible long range interaction between dislocations and radiation-induced defects.