Vol.19,

The site of Shanghai Synchrotron Radiation Facility (SSRF) is of complicated geological conditions, and a system to monitor the uneven subsidence of foundation and key parts (different kinds of magnets) of the accelerators is a necessity. Considering actual conditions of the accelerator structure and the assembling place, a new type of sensor of hydrostatic levelling system (HLS) has been designed. In order to obtain the required measurement accuracy, every HLS's sensor was strictly calibrated. In this paper, we introduce the special calibration method to establish the HLS. The method has been used in the calibration for vessel sensor for SSRF.

449

The K-V beam through a hackle periodic-focusing magnetic field is studied using the particle-core model. The beam halo-chaos is found, and a power function controller is proposed based on mechanism of halo formation and strategy of controlling halo-chaos. Multiparticle simulation was performed to control the halo by using the power function control method. The results show that the halo-chaos and its regeneration can be eliminated effectively. We also find that the radial particle density evolvement is of uniformity at the beam's centre as long as appropriate parameters are chosen.

535

551

Radiation damage of NPN transistors under different fluxes with electron energy of 1.5 MeV was investigated in this article. It has been shown that when NPN transistors were irradiated to a given fluence at different electron fluxes, the shift of base current was dependent on flux. With electron flux decreasing, the shift of base current becomes larger, while collector current almost keeps constant. Thus, more degradation of NPN transistors could be caused by low-electron-flux irradiation, similar to enhanced low-dose-rate sensitivity (ELDRS) of transistors under ⁶⁰Co γ-irradiation. Finally, the underlying mechanisms were discussed here.

650

CT has rather low accuracy for the follow-up of tumors after therapy. This study was to determine whether the diagnostic accuracy can be improved with ^99mTc-HL91 SPECT in comparison with parallel results of CT imaging. Thirty patients of lung cancer or head & neck cancer, suspected of recurrences on clinical symptoms and CT during clinical follow-up after therapy, underwent ^99mTc-HL91 SPECT. The radioactivity ratios of tumor to normal tissues (T/NT) were calculated using the region of interest technique. Results of ^99mTc-HL91 SPECT were verified by histopathology. The ^99mTc-HL91 average uptake ratios of T/NT in the group of recurrent lesions and non-recurrent lesions were 1.58±0.16 and 1.18±0.14, respectively. A significant difference was found between T/NT data of the two phases (t=4.87, P<0.001).The^99mTc-HL91 SPECT shows sensitivity of 72.73%, specificity of 89.47% and accuracy of 83.83% for differentiating recurrent lesion, while the CT shows sensitivity of 63.63%, specificity of 84.21% and accuracy of 76.67%. A combination of ^99mTc-HL91 SPECT and CT for 21 patients with lung cancers or head & neck cancers with congruent results shows sensitivity of 100%, specificity of 94.12% and accuracy of 95.23%. It is concluded that ^99mTc-HL91 SPECT may play a role in differentiating recurrent lesions in patients with lung cancer and head & neck cancer. Furthermore, the combination of CT and ^99mTc-HL91 SPECT is a more effective method for diagnosing recurrence of lung cancer and head & neck cancer.

540

The organics in γ-ray irradiated aqueous N, N-diethylhydroxylamine (DEHA) solution, which is used as a reducing agent in reprocessing spent nuclear fuel, were analyzed with gas chromatography equipped with FFAP capillary column and flame-ionization detector. It was found that irradiated DEHA solutions contained acetaldehyde, ethanol, and acetic acid. For DEHA of 0.2 mol/L irradiated to 10~1000 kGy, the concents of acetaldehyde, ethanol and acetic acid are (9.7~18.7)×10^-3, (0.4~23.4)×10^-3 and (6.5~11.7)×10^-3 mol/L, respectively. The concentration of DEHA decreases obviously with the dose.

528

Co-55 (t_1/2=17.53 h) was produced by 150 μA irradiation of a natural nickel target using 15 MeV protons. It was separated from the irradiated target material by two ion exchange chromatography steps with a radiochemical yield of >95% and was used for the preparation of [⁵⁵Co]vancomycin ([⁵⁵Co]VAN). Optimization studies were performed using Co-57 due to its longer half-life. Cobalt-57 (t_1/2=271.79 d) was produced by irradiation of a natural nickel target with 150 μA current of 22 MeV protons. The ⁵⁷Co was separated from the irradiated target material using a no-carrier-added method with a radiochemical yield of >97%. Both products were controlled for radionuclide and chemical purity. The solutions of [⁵⁵Co]VAN were prepared (radiochemical yield>80%) starting with ⁵⁵Co acetate and vancomycin at room temperature after 30 min. A precise solid phrase extraction (SPE) method was developed using Si Sep-Pak in order to purify/reconstitute the final formulation for animal studies. [⁵⁵Co]VAN showed a radiochemical purity of more than 99%. The resultant specific activity was about 1.15 TBq/mmol. It is proved that the tracer is stable in the final product and in presence of human serum at 37°C up to 24 h. Biodistribution study of [⁵⁵Co]VAN in normal rats was undertaken for up to 72 h.

468

540

A matrix stripping method for the conversion of in-situ gamma ray spectrum, obtained with portable Ge detector, to photon ﬂux energy distribution is proposed. The detector response is fully described by its stripping matrix and full absorption efficiency curve. A charge collection efficiency function is introduced in the simulation to take into account the existence of a transition zone of increasing charge collection after the inactive Ge layer. Good agreement is obtained between simulated and experimental full absorption efficiencies. The characteristic stripping matrix is determined by Monte Carlo simulation for different incident photon energies using the Geant4 toolkit system. The photon ﬂux energy distribution is deduced by stripping the measured spectrum of the partial absorption and cosmic ray events and then applying the full absorption efficiency curve. The stripping method is applied to a measured in-situ spectrum. The value of the absorbed dose rate in air deduced from the corresponding ﬂux energy distribution agrees well with the value measured directly in-situ.

432

We present the electronic structure and electron energy loss spectroscopy (EELS) for uranium, niobium and U₃Nb in which uranium is substituted by niobium. Comparing the electronic structures and optical properties for uranium, niobium and U₃Nb, we found that when niobium atom replaces uranium atom in the center lattice, density of state (DOS) of U₃Nb shifts downward to low energy. Niobium affects DOS for f and d electrons more than that for p and s electrons. U₃Nb is similar to uranium for the electronic energy loss spectra.

684

438

The point-reactor model with power reactivity feedback becomes a nonlinear system. Its dynamic characteristic shows great complexity. According to the mathematic definition of stability in differential equation qualitative theory, the model of a reactor with power reactivity feedback is judged unstable. The equilibrium point is a saddle-node point. A portion of the trajectory in the neighborhood of the equilibrium point is parabolic fan curve, and the other is hyperbolic fan curve. Based on phase locus near the equilibrium point, it is pointed out that the model is still stable within physical limits. The difference between stabilities in the mathematical sense and in the physical sense is indicated.

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