Vol.13,

The ²³⁰Ra has been produced via multinucleon transfer and dissipative fragmentation of heavy target in the 60 MeV/u ¹⁸O ion reaction with natural thorium. The radium was radiochemically separated from irradiated thorium targets. ²³⁰Ac was obtained by 230Ra→β−A230c, Thin Ra sources were prepared for observing fission fragments from β-delayed fission of ²³⁰Ac. The sources were exposed to the mica fission track detectors and measured by a HPGe γ detector. The two fission events were obtained and could been assigned to the β-delayed fission of ²³⁰Ac. The β-delayed fission probability of ²³⁰Ac was determined to be (1.19±0.85)×10^-8.

279

Research on a single cell Multi-gap Resistive Plate Chamber (MR.PC) was carried out for the Time Of Flight detector (TOF) R. and D of the STAR. experi-ment. The property of the single chamber was tested with the test beam facility T10 at CERN in Geneva. The MRPC was scanned with the test beam to get the efficiency and time resolution at different position of the active area. The HV plateau was also measured. The time resolution is 65 ps which satisfies the requirement of STAR. The working mechanism of the MRPC is also explained.

274

Combining x-ray diffraction and high pressure Mössbauer spectroscopy, the structure and the hyperfine parameters of Sn substituted for Fe in γ'-Fe₄N were in-vestigated. The results of x-ray diffraction indicate that single phase γ'-(Fe_1-xSn_x)₄N compounds can be synthesized in the composition range 0≤x≤0.3, and the lattice parameter can be well fitted with two linear formulas α₀(x) = 3.795+0.019×x (0.0≤x≤0.10) and α₀(x)=3.795 + 0.228 × (x-0.1)(0.10≤x≤0.30) for different content of Sn. Using high pressure Mössbauer spectra, the influences of the magnetovolume effect and the chemical bonding effect of Sn atom on the hyperfine magnetic field and the isomer shift were first distinguished. It is found that the magnetovolume and the chemical bonding have different influences on the properties of γ'-(Fe_1-xSn_x)₄N. and the latter plays a more important role.

442

The effect of a 0.9 nm Mo interlayer at the interface of Ti film deposited on a Si substrate on phase formation of TiSi₂ during annealing has been studied by using transmission electron micro-diffraction technique. When Ti/Mo/Si was annealed at low temperature as 550℃ for 30 min in Ar ambient, a metastable phase, i.e., hexagonal C40 TiSi₂, and the equilibrium phase, i.e., orthorhombic C54 TiSi₂, were both detected. The experimental patterns of the C40 and C54 compare well with the simulated ones.

274

CdS films prepared with chemical pyrolysis deposition (CPD) at different temperature during film growth were characterized by XRD. Hexagon-like struc-ture appeared at the temperature of 350-500℃, while wurtzite phase was observed at temperature of 540℃ during film growth. Also CdS films prepared by CPD at 400℃ were undergone post annealing at different temperature of 200-600℃ or post Ar⁺ ion irradiation. It is found that wurtzite phase happened when the annealing temperature rose to 600℃. And hexagon-like structure existed at the annealing temperature from 25℃ to near 500℃. Ar⁺ ion irradiation could not cause phase transformation, but induce some preferred orientations and an increase in grain size for the CdS films.

482

In order to study the mechanism of irradiation-indueed damage of botanic samples caused by low energy heavy ions, transmission energy spectrum mea-surement was performed. Kidney bean slice samples 100 µm in thickness were irradi-ated by 50 keV N⁺ ions. The irradiation beam current density was about 30 μA/cm², and the irradiation ion doses were 1×10¹⁵, 1×10¹⁶, 3×10¹⁶ and 1×10¹⁷ ions·cm^-2, respectively, A target set up that could greatly reduce the incident ion current density was designed to achieve the damage-free measurement. The 3.2 MeV H⁺ transmitted ion energy spectrum measurement was carried out before and after the irradiation. From the transmission ion energy spectrum, it was found that the kidney bean slice itself was structurally inhomogeneous compared with the PET films (C₁₀H₈O₄). Our results indicated that the average mass thickness changed little when the N+ ion dose was below 3×10¹⁶ ions·cm^-2, but changed obviously when ion dose was beyond 3×10¹⁶ions·cm^-2.

354

GaN film grown on Si substrate was characterized by Rutherford backscattcring/Channeling (RBS/C). The experimental results show that the thiek-ness of GaN epilayer is about 2.5 µm and the GaN film has a good crystalline quality (χ_min=3.3%). By using channeling angular scanning, the 0.35% of average tetragonal distortion in GaN layer is observed. In addition, the depth profiles of strain in GaN film layer reveal that the strain in GaN film nonlinearly decreases with the increase of film thickness. The strain-free thickness (above 2.5 µm) of GaN film on Si substrate is far below that (150 µm) of GaN film on Sapphire.

315

345

The radioactivity level of the ambient environment of Anren Bone-coal Power Station (BCPS) was investigated systematically. The γ radiation dose rate level in the environment, the content of ²³⁸U and ²²⁶Ra in the ambient soil and the farmland in the direction of downwind, the concentrations of ²³⁸U, ²³²Th, ²²⁶Ra, ⁴⁰K and ²²²Rn, as well as α potential energy in air, and the concentrations of natural U and Th in effluent are all higher than the corresponding values of the reference site. The additional annual effective dose equivalent to the residents living in the houses made of bone-coal cinder brick is 2.7 mSv.

297

A nuclear microprobe with high spatial resolution and high analytical sensitivity was applied to analyze trace elements, especially lead, in vehicle exhaust of Shanghai city. The result shows that the chemical composition and its corresponding x-ray relative intensity are different among different vehicle exhausts, There are many kinds of metal elements in particles of vehicle exhaust, most are harmful to people, such as Ti, Cr, Mn, Pb, etc. We found that the lead concentration was 6820μg/g and the bromine concentration was 5300 μg/g in the exhaust from Santana using leaded gasoline (SULG), which is higher than any other kinds of vehicle exhausts. We have also detected the minimum lead in the particles of unleaded gasoline and its content varies from one to another. Its mean concentration was 450 µg/g and the highest reached 6210 µg/g. The unleaded gasoline's Pb existed in the whole particle while the leaded gasoline's enriched in the surface of the particle and was more harmful to the human beings.

323