用反应溅射法制备无衬底的氮化钽薄靶

我们制备无衬底氮化钽薄靶的目的,是为着用核物理背散射实验法研究工业上生产的氮化钽薄膜的钽和氮的组份比,或它们的原子比。 众所周知,阴极溅射就是在真空室中把衬底片置于阳极上,靶材钽片作为阴极。在阳极和阴极间施加直流高压后,阳极和阴极之间便产生辉光放电,使惰性气体氩气电离所产生的正离子去轰击阴极表面,使靶材表面的原子从中逸出而沉积在衬底片表面上。而反应溅射就是在这种阴极溅射的同时,在惰性气体中有意混入一定量的反应性气体来获得反应生成物薄膜。如果使用氮气为反应性气体,那么得到的就是有衬底的氮化钽薄膜。若在衬底片表面上事先喷镀一薄层脱膜剂,如NaCl、CsI、Al、Cu等。把这种反应溅射后生成的氮化钽膜连同衬底片一起放入相应的溶剂或腐蚀剂中。待脱膜剂被溶解或腐蚀后,就得到无衬底的氮化钽薄膜。     

质子活化分析快速测定钽、铌中的氮

钽和铌在高温时会熔解入微量的氮气,这些氮气位于晶体的空位,它会影响钽和铌的物理、机械和化学性质。很难用一股方法测定难熔金属中的微量气体。 带电粒子及光子活化分析都可测定金属中的氮含量。常用的核反应及可能的干扰反应列于表1。前面四种核反应都已被广泛应用。由于它们产生的都是半衰期较短的纯β~+辐射体,所以,仅靠选择适当的入射粒子能量,有时干扰核反应仍很难避免。K.Strijckmans等根据第五种核反应,用12MeV质子束测定难熔     

气体探测器的聚丙烯薄窗和薄膜电极的制备

用热拉伸法制备用于气体探测器的超薄聚丙烯薄膜存在膜易破和粘结等问题。分析薄膜制备的物理过程和膜破的原因后，不用大面积聚四氟乙烯薄膜做防粘层，而用带锥形泄气孔表面喷涂聚四氟乙烯的拉膜盘和从高压氮气获取的准静态拉伸压力制得了超薄薄膜和电极。     

离子束辅助沉积立方氮化硼的试验研究

本文运用离子束辅助沉积法在硅片上制备了立方氮化硼薄膜 ,主要研究了辅助能量、辅助束流及辅助束中氮气含量等参数对膜中立方氮化硼 (c -BN)含量的影响。用红外光谱 (FTIR)及光电子能谱 (XPS)分析技术对得到的c -BN膜进行了分析。结果表明 :(1)合适的离子辅助能量能够获得c -BN含量高的薄膜。(2 )膜中c -BN的含量随空中N2 含量的提高而增加。 (3)辅助束流对薄膜的形成影响不明显     

离子束辅助沉积立方氮化硼的试验研究

运用离子束辅助沉积(IBAD)法在硅片上制备了立方氮化硼(c—BN)薄膜，研究了辅助能量、辅助束流及辅助束中氮气含量等参数对膜中c—BN含量的影响。用红外光谱(FTIR)及X射线光电子能谱(XPS)分析技术对得到的c—BN膜进行了分析。结果表明：合适的离子辅助能量能够获得c—BN含量高的薄膜；膜中c—BN的含量随辅助气体中N2含量的提高而增加；辅助束流对薄膜的形成影响不明显。     

日本原子能研究所开发出将氧化镅转化成氮化物的技术

【日本《原子能视野》 1999年 5月刊报道】　日本原子能研究所于 3月 18日开发出了将乏燃料内半衰期为 70 0 0多年的氧化镅转化成可作为燃料使用的氮化镅的技术。将氧化镅与石墨粉末混合 ,然后在氮气中进行130 0℃的高温加热处理 ,便可得到氮化镅。将高放废物中所含超铀元素和长半衰期核物质再次作为反应堆燃料使用以消除废物的技术是下一代原子能开发的目标 ,原子能研究所此次开发就是这项技术的基础。本次开发的技术是在处理半衰期较长的镅及镎的同时 ,将镅及锔等进行处理作为燃料使用 ,这是今后的重点目标。原子能研究所在后处理中得到的…     

离子轰击对氮化铀表面氧化行为的影响

采用离子氮化技术制备得到一定厚度的氮化铀层,以不同能量的氩离子轰击考察氮化铀的辐照氧化行为,并与大气中的自然氧化行为进行对比,考察材料在辐照环境下的稳定性。结果表明,氮化铀表面经氩离子轰击后,表面形貌发生了改变;氩离子轰击氧化与大气中的自然氧化行为存在差异,离子轰击增强了氮化铀表面的氧化程度,但其对氧化行为的影响主要在浅表面,大气氧化的氮化铀氧化层更厚;随着氩离子轰击能量的增加,表面氧化物含量及氧化层深度显著增加。总体而言,氩离子辐照对氮化铀层的影响随深度的增加而减弱,并不影响氮化铀的整体稳定性。     

日本核废物处理技术有新发展

【《科技日报》 1 999年 4月 1 4日东京报道】　最近日本原子能研究所发布消息说 ,他们利用碳热还原法在世界上首次将镅的氧化物直接还原成氮化镅 ,把处理核废物的技术大大向前推进了一步。核反应堆使用的燃料一般为铀或钚 ,在它们燃烧后的乏燃料中有大量高辐射物质。其中半衰期在 1 0 0 0年以上的主要是镅、镎等所谓的超铀元素 (TRU) ,所以开发有效处理TRU的技术便成了关键。日本原子能研究所的科研人员使用碳热还原法 ,在氧化镅中加入过量的碳 ,然后在氮气流中加热到 1 30 0℃ ,成功地还原为氧残留量极少的氮化镅。超铀元素镅具有极强…     

钽电容器电介质层厚度的测量

金属钽片在阳极氧化处理过程中,在不同的电解液、电解电压及通电时间下,会形成不同厚度的Ta_2O_5层,即可制成各种不同耐压规格的钽电容器。钽基片上的Ta_2O_5层厚度与阳极氧化工艺之间的数量关系过去不太清楚。用离子束背散射方法便可很好地解决这一问题,并且具有简便、可靠、无需标准样品、不破坏样品等优点。钽片的阳极氧化处理一般有两种方法。一种是先预赋能,然后再赋能;另一种是不预赋能而仅     

pA微电流仪表的标定方法研究

为了对p A微电流测量仪表进行标定,根据微电流的测量原理,研制了一种采用高值电阻器的p A微电流源。分析了电阻器热噪声的影响,指出采用高值电阻器的必要性。分析了测量仪表的输入端口特性,指出端口电势是制约微电流源准确度的关键因素,从而确定了源电压和输出电阻器的设计参数。测试验证表明:所设计的±1~±200 p A微电流源准确度优于±3%,可满足p A微电流测量仪表的标定需要。     

Eu活化过渡法测量绝对热中子注量率

在相同条件下,以不同时间辐照Ａｕ箔和Ｅｕ箔,用γ谱仪测量＾１９８Ａｕ的４１１ｋｅＶγ射面积和＾１５２Ｅｕ的４１１ｋｅＶγ峰面积,再通过４πβ－γ符合装置测得金箔的绝对中子注量率,根据两者的峰面积之比和测得的Ａｕ箔绝对中子注量率,求得＾１５３Ｅｕ的４１１ｋｅＶγ峰面积对应的中子注量率。     

DU/Au复合平面膜大气寿命研究

黑腔材料的大气寿命是点火黑腔的重要指标之一,寿命实验是黑腔研制中的必要环节。本文通过X射线光电子能谱方法分析了DU/Au平面膜储存于大气环境中O含量及其分布随时间的变化规律,利用X射线衍射仪测试了相同情况下薄膜的结晶状态。实验证明,这种平面膜大气寿命（O原子百分数低于5%）在18～21 d之间,此期间内薄膜晶体结构无明显变化,未检测到氧化物结晶信号。     

光学渡越辐射在电子束能谱测量上的应用

论述了用光学渡越辐射对强流短脉冲束团的能谱进行测量的理论和方法。探讨了利用单膜装置、双膜装置或多膜装置产生的光学渡越辐射进行束流能谱测量的方法，并针对２０ＭｅＶ电子感应直线加速器能散为０．５％的电子束能谱测量作了一些计算以得到部分装置的设计参数。计算表明：应用渡越光栅谱仪选择合适的膜片厚度及间距，对于给定的电子能谱，可以得到大的能量接受度和好的能量分辨率。然而，要用大量的膜片是困难的，而且还有许多影响多膜渡越辐射能谱仪的实际问题需要讨论。     

U形靶框-双层结构碳剥离膜制备

本研究涉及用于兰州重离子加速器冷却储存环上的碳剥离膜的制备方法。该剥离膜采用特殊的U形靶框和双层结构，使膜的强度大为加强，以提高高真空条件下剥离膜使用寿命。采用碳弧法制备的剥离膜的有效面积较大，为10cm²，质量厚度约为150μg/cm²。碳剥离膜的X衍射谱测试结果表明，膜上的碳以非晶体石墨形式存在。     

Diode-like ion-track asymmetric nanopores: Some alternative methods of fabrication

We present two fabrication methods which allow production of ion-track nanopore membranes with pronounced geometrical asymmetry and diode-like ionic conductivity. The asymmetry of the pores is provided by self-assembly of surfactant molecules at ion-track entrances on one side of the ion-irradiated polymer foil. On the other side of the membrane, the effect of surfactant is excluded using a pre-treatment with ultraviolet radiation or a surfactant-free etching solution. Highly tapered pore profiles are obtained and characterized using SEM and FESEM. In electrolyte solutions, the asymmetric pores thus fabricated exhibit a high rectification of electric current. The nanopores with a large angle aperture can be of interest for resistive-pulse technique applications and for the atomic beam projection nanolithography.     

Interactions of slow H, H2, and H3 with thin carbon foils

Interaction processes resulting from the transit of incident 2–30 keV H⁺, H⁺₂ and H⁺₃ through 1.2 to 2.5 μg cm⁻² carbon foils are investigated by examining the charge state and angular scatter distributions of atomic and molecular species that exit the foils. A comparison of the scatter distributions of exiting H⁺₂ and H⁰ from incident H⁺₂ and H⁺₃ show that the atomic components of transmitted molecules scatter independently from foil atoms. For a given foil thickness, the measured fractions of H⁺₂ from incident H⁺₂ and H⁺₃ are inversely proportional to the square of the angular scatter half-width.     

Recent Developments in Accelerator Based Atomic Physics

Much progress toward a detailed understanding of atomic collision phenomena and atomic structure has recently been made with the aid of accelerated ion beams. Beam foil Lamb shift measurements and the possible observation of spontaneously created positrons from quasi-superheavy atoms give promise for critical tests of QED. The mechanisms of innershell ionization and charge transfer in ion atom collisions have been intensively investigated and the results have brought together the various approaches - Coulomb excitation and MO treatments for these processes. That violent collisions at high energies can cause multiple ionization of the target atom has been known for some time. However, only recently have theoretical treatments been able to predict, e.g., the degree of L shell ionization accompanying K shell ionization. The highly charged ions formed in these collisions have themselves come under intensive investigation and are used for the study of the structure and collision physics of multiply charged species. Electron-Ion collision studies have also been started and initial results on dielectronic recombination are reported.     

Numerical and experimental studies of Electra's scalloped transmission foil cooling with small impinging jets

The 5 Hz rep-rate operation of the Electra KrF laser necessitates the cooling and protection of the transmission foil that is subject to the pulsating electron beam bombardment. The pulsed volumetric heating from the e-beam attenuation heats up the foil (～2.54 × 10^?5 m thick) rapidly and often causes the foil to fail, increasing the operation cost and down time for the laser. Various methods have been investigated forheat transfer enhancement. While elevated heat transfer was achieved, the previous methods assume a flat foil shape. The actual foil shape is scalloped due to the pressure difference across the foil during the laser operation. Also a new “scalloped” foil design was proposed for thermal stress reduction. This paper investigates the applicability of small locally impinging jets to cooling the scalloped-shaped foil. The jets were formed through a line of small circular openings on two stainless-steel jet tubes aligned with the foil edges having the two columns of jets impinging on the foil obliquely in a staggered pattern for improved coverage. CFD simulations were used to optimize jet configurations. Experiments were performed that utilize a scalloped foil strip which matched the foil shape between two neighboring supporting ribs in the Electra hibachi. Jet diameters and jet velocities were varied at a surface heat flux greater than 20.0 kW/m². Substantial heat transfer enhancement with impinging jets was observed. Average Nusselt numbers were correlated with jet Reynolds number and the normalized jet-to-foil distance. The study indicates that the impinging jets can effectively enhance heat transfer for the scalloped foil and can be a promising method for actual foil coolingof KrF lasers, including Electra.     

Infrared Imaging Bolometer for the HL-2A Tokamak

An infrared imaging bolometer diagnostic has been upgraded recently to be adapted for the complications of the signal-to-noise ratio arising from the low level of plasma radiation and high reflectivity of low energy photon(6.2 eV).It utilizes a platinum foil,blackened on both sides with graphite spray,as the bolometer detector.The advantage of the blackened foil is the light absorption extending into the infrared.After a careful calibration of the foil,the incident power density distribution on the foil is determined by solving the heat diffusion equation with a numerical technique.The local plasma radiated power density is reconstructed with a minimum fisher information regularization method by assuming plasma emission toroidal symmetry.Comparisons of the results and the profiles measured by an ordinary bolometric detector demonstrate that this method is good enough to provide the plasma radiated power pattern.The typical plasma radiated power density distribution before and after high mode(H-mode) transition is firstly reconstructed with the infrared imaging bolometer.Moreover,during supersonic molecular beam injection(SMBI),an enhanced radiation region is observed at the edge of the plasma.     

Some current problems in beam-foil spectroscopy

The use of tilted foils to produce alignment and orientation excitation asymmetries in fast ion beams is reviewed. These asymmetries, their observed dependence on various experimental parameters (ion energy, foil tilt angle, observation geometry, etc.) and their utilisation for the study of atomic and nuclear structure properties are discussed. In addition, measurements are described that utilise differential decay curve measurements to suppress cascade effects and to determine decay rates into forbidden or inhibited radiative and autoionising intercombination channels.