14MeV医用驻波加速管的微波调试

介绍了１４ＭｅＶ医用驻波加速管的微波调试情况。该加速管的加速能量与束流多档可调，可提供６、１５ＭＶ两档Ｘ射线和６—１４ＭｅＶ五档的电子线。该加速管总长１．４５ｍ，采用轴耦合双周期π／２模驻波结构。利用峰值２．６ＭＷ的脉冲磁控管为功率源，工作频率为２９９８ＭＨｚ，脉冲宽度４μｓ，重复频率为２５０ｙｓ。通过调节入口微波功率、电子枪的注入电压、电流等参数，实现加速管的能量调变     

短链羟肟酸对Pu(Ⅳ)的配位、还原及反萃

在λ-19分光光度计上观测了加入甲羟肟酸(FHA)前后Pu(Ⅳ)-硝酸溶液的吸收光谱随时间的变化，并进行了甲、乙羟肟酸(FHA，AHA)对含铀的30％TBP／0K中Pu(Ⅳ)的反萃实验。结果表明：在硝酸溶液中短链羟肟酸能与Pu(Ⅳ)形成比较稳定的配合物，随着溶液放置时间的延长，溶液中的Pu(Ⅳ)逐渐被还原到Pu(Ⅲ)，但该还原过程比较缓慢；在一定条件下，短链羟肟酸能有效地将有机相中的Pu(Ⅳ)反萃到水相，配位剂浓度的增加和反萃酸度的降低有利于短链羟肟酸对Pu(Ⅳ)的反萃。在同样条件下，AHA对Pu(Ⅳ)的反苯效果比FHA好。但这种差别随着配位剂浓度的增加和反萃酸度的降低而变小。     

长链脂肪酸衍生物99Tcm-MAMA-(CH2)nCOOH的制备和生物分布

以短链二酸和N2S2类配体（MAMA）为起始原料，合成了4个长链脂肪酸衍生物MAMA-(CH2)nCOOH（n=14,15,16,17），通过与99Tcm-GH在沸水浴中加热30 min完成配体交换反应，实现了99Tcm的标记，其标记率均大于90%。正常小鼠的生物分布数据显示这4个标记物在心肌中均有一定的摄取（5 min时的放射性摄取百分数依次为5.73、5.52、4.82和4.03%ID•g－1），但血本底较高，而且血清除较慢，标记物能否参与脂肪酸尚需进一步研究。     

Multiplicity dependence of charged particle,? meson,and multistrange particle productions in p + p collisions at s~(1/2) = 200 GeV from PYTHIA simulation

We report the multiplicity dependence of charged particle production for the n~±, K~±, p, , and ? mesons at |y|1:0 in p + p collisions at s~(1/2) = 200 GeV from a PYTHIA simulation. The impact of multiple parton interactions and gluon contributions is studied and found to be a possible source of the splitting of the particle yields as a function of p_T with respect to the multiplicity. No obvious particle species dependence of the splitting is observed.The multiplicity dependence of the ratios Kˉ/πˉ, K~+/π~+,/πˉ, p/π~+, and K_s~0 at mid-rapidity in p+ p collisions is found to follow a tendency similar to that in Au t Au collisions at (s_(NN))~(1/2) = 200 GeV at the Relativistic Heavy Ion Collider, indicating similar underlying initial production mechanisms despite the differences in the initial colliding systems.     

Oxygen potentials of UO2 + x and (Th1 − yUy)O2 + x

Oxygen potentials of UO_{2 + x} and (Th_{1 ? y}U_y)O_{2 + x} (y = 0.2 and 0.4) were measured by means of thermogravimetry in the range of 1282 ≦ T ≦ 1373 K and 10su?19 ≦ P(O₂) ≦ 10^?1 Pa. The oxygen potentials of (Th_{1 ? y}U_y)O_{2 + x} plotted against the mean uranium valence (V_u) were seen to be more negative than those of UO_{2 + x} in the region of V_u < 4.08 and more positive than those of UO_{2 + x} in the region of V_u > 4.08. The partial molar enthalpies and entropies of oxygen for UO_{2 + x} and (Th_0.6U_0.4)O_{2 + x} showed that each has a maximum against $\text{O}\text{U}\text{or}\text{O}\text{M}$ ratio at about 2.001, but no clear maximum was seen for (Th_0.8U_0.2)O_{2 + x}. From the oxygen partial pressure dependences of x in UO_{2 + x} and (Th_{1 ? y}U_y)O_{2 + x}, the defect structure was discussed with a complex defect model consisting of oxygen vacancies and two different types of interstitial oxygens.     

Resonant ion stimulated desorption of O from the TiO2(1 1 0) surface: Effects of oxygenation and ion bombardment

The O⁺ desorption from reduced, oxygenated, and ion-bombarded TiO₂(1 1 0) surfaces has been investigated during He⁺ irradiation. The O⁺ desorption is initiated by creation of an antibonding O 2s core hole state via quasi-resonant charge exchange with the He⁺ 1s state, followed by the intra-atomic Auger decay of the O 2s hole. Upon oxygenation of the reduced TiO₂(1 1 0) surface, the O⁺ yield increases by one order of magnitude. The O₂ molecule is dissociated at the vacancy site of bridging oxygen and the oxygen atoms either fill a vacancy site or chemisorb at a fivefold-coordinated Ti⁴⁺ site as an adatom. The latter is detected with much higher efficiency than the former. The O⁺ yield is increased during He⁺ bombardment of the reduced TiO₂(1 1 0) surface due to formation of lower coordinated oxygen atoms. The oxygen species thus formed by ion bombardment or oxygenation are unstable on the surface and tend to diffuse into bulk vacancy sites or higher coordination surface sites even at room temperature.     

Resonant charge transfer in back-scattering of H-atoms from the Cs adsorbates on the Cs/Cu(1 1 1) surface

We use the wave packet propagation approach to study the dynamics of resonant charge transfer in hydrogen back-scattering from Cs adsorbates on Cu(1 1 1). The affinity level of the projectile strongly interacts with an adsorbate-localized state leading to an important modification of the projectile–substrate resonant charge transfer. At very low collision energies (<2.5 eV) the adiabatic evolution of the system leads to the blocking of the negative ion formation in back-scattering of neutral hydrogen atoms from Cs adsorbate. At higher energies non-adiabatic transitions exist, and negative ion formation is possible.     

基于CATHARE程序的熔盐堆热工物理耦合模拟计算

针对熔盐堆燃料和慢化剂的特点,对压水反应堆热工水力计算程序CATHARE进行了适应性改造。使用改造后的程序进行熔盐堆单通道流体的物理和热工耦合计算分析。分析计算表明,改造后的CATHARE程序可以模拟反应性引入事故和流量引入事故等瞬态工况的堆芯热工物理耦合过程。     

Vaporization study on UO2 and (U1−yNby)O2+x by mass-spectrometric method

The vapor pressures over UO_2.000 and (U_1?yNb_y)O_2+x (y = 0.01, 0.05, x = 0.000–0.022) were measured by the mass-spectrometric method in the temperature range 2025–2343 K. The main gas species over UO_2.000 were observed to be UO₃(g) and UO₂(g) and those over (U_1?yNb_y)O_2+x were NbO₂(g), NbO(g), UO₃(g) and UO₂(g). The partial vapor pressures of almost all gas species over (U_1?yNb_y)O_2+x increased with increasing O/M (M = U + Nb) ratio. With increasing Nb content in (U_1?yNb_y)O_2.000, the partial vapor pressures of UO₂(g) and UO₃(g) decreased and those of NbO(g) and NbO₂(g) increased. The congruently vaporizing composition in the (U_1?yNb_y)O_2+x phase was estimated to be ($\text{U}{}_{\mathrm{0.985\pm 0.005}}\text{Nb}{}_{\mathrm{0.015\pm 0.005}}\text{)O}{}_{2.000}$ from the compositional dependence of the total vapor pressures. The partial molar enthalpy and entropy of oxygen of (U_1?yNb_y)O_2+x calculated from the partial pressures of gaseous species NbO₂(g) and NbO(g) were in fairly good agreement with those previously obtained by the present authors with a thermobalance.     

Peculiarities of defect generation in Si+-implanted GaAs (2 1 1)

Peculiarities of the defect generation during implantation of (2 1 1) GaAs with Si⁺ ions and doses below the amorphisation dose of GaAs have been investigated by X-ray diffraction, the secondary ion mass-spectroscopy (SIMS) and transmission electron microscopy. It was shown, that in such implanted layers less radiation defects will be formed and these defects are more easily annealed by rapid photon annealing (RPA) than in (1 0 0)-oriented wafers.     

Oxygen potentials of (th, u)o2+x solid solutions

The oxygen potential and the nonstoichiometry ($\text{x}$) for (Th_1?yU_y)O_2+x were measured in situ at 1000° 1&;#x0303;200°C using a solid electrolyte oxygen sensor and a thermobalance, respectively. The results showed that the oxygen potentials of (Th_1?yU_y)O_2+x are not a function only of the U valence in the investigated range of $\text{0.05?y?0.20}$. The oxygen potentials at 1200°C decrease negatively with increasing thorium content at a given U valence. The calculated activity coefficients of urania in the solutions indicate an increasing positive deviation from ideality with increasing U valence.     

Phase diagram of the UO2-FeO1+x system

Phase-relation studies of the UO₂-FeO_1+x system in an inert atmosphere are presented. The eutectic point has been determined, which corresponds to a temperature of (1335 ± 5) °C and a UO₂ concentration of (4.0 ± 0.1) mol.%. The maximum solubility of FeO in UO₂ at the eutectic temperature has been estimated as (17.0 ± 1.0) mol.%. Liquidus temperatures for a wide concentration range have been determined and a phase diagram of the system has been constructed.     

Interferometry analyses of pion and kaon for the granular sources for Au+Au collisions at (~SNN)~(1/2)=200 GeV

We examine the interferometry results of identical pion and kaon for the granular sources of quark-gluon plasma droplets for the Au + Au collisions at S_(NN)~(1/2) = 200 GeV.The effects of particle absorptions of pion and kaon on the results are investigated.We find that the absorptions lead to the decrease of the interferometry radii.After considering the absorptions,the interferometry radii of pion and kaon of the granular sources are in better agreement with the experimental data of the Au + Au collisions.