电解还原制备U（IV）过程中的阳极材料腐蚀研究

用间歇电解还原法研究了在有机玻璃电解槽中阳极镀铂钛网在ＵＯ２（ＮＯ３）２－ＨＮＯ３－Ｎ２Ｈ５ＮＯ３－Ｈ２Ｏ体系中的耐腐蚀情况。研究结果表明：在无隔膜电解还原时，镀铂钛网上的Ｐｔ的腐蚀速率极低（〈２．５×１０＾－２μｍ／ａ），而在以阳离子交换膜作隔膜的电解还原中，镀铂钛网上的Ｐｔ有明显的腐蚀，其腐蚀速率为５．７μｍ／ａ。对这两种情况下Ｐｔ的腐蚀速率明显差别的原因进行了分析讨论。     

CR—39探测器测量中子剂量的实验研究

研究了应用ＣＲ－３９探测器测量中子剂量的方法,蚀刻条件,刻度和实际应用。结果表明最佳蚀刻条件为：６．５ｍｏｌ／Ｌ ＫＯＨ,７０℃,ｈ刻度系数为７．０×１０＾－３ｍＳｖ／（径迹数．ｃｍ＾－２）,最低可探测下限为０．０６ｍＳｖ,可用于一般中子－γ混合辐射场中中子剂量的测量。     

~（85）Sr、~（134）Cs和~（60）Co在浅地层黄土与地下水间的分配系

本文报道了￣（８５）Ｓｒ、￣（１３４）Ｃｓ和￣（６０）Ｃｏ在采自本院野外试验场，从地表到地下２ｍ深黄土与地下水间分配系数的测定结果，以及核素浓度、ｐＨ和温度对分配系数的影响。黄土采集的深度范围分别为：地表－０．５ｍ，０．５－１ｍ，１－１．５ｍ，１．５－２ｍ，共采集１６个样品；地下水取自试验场的井水。实验采用静态法。实验结果表明，１６个样品测定的￣（８５）Ｓｒ、￣（１３４）Ｃｓ和￣（６０）Ｃｏ的分配系数的均值分别为８２、７．４×１０￣３和５．４×１０￣３ｍＬ／ｇ；在不同深度的黄土中测得的分配系数基本一致。ｐＨ值的变化对￣（１３４）Ｃｓ和￣（８５）Ｓｒ的分配系数有较大影响，对￣（６０）Ｃｏ则影响不大。     

电解还原制备U(Ⅳ)过程中的阳极材料腐蚀研究

用间歇电解还原法研究了在有机玻璃电解槽中阳极镀铂钛网在ＵＯ２（ＮＯ３）２－ＨＮＯ３－Ｎ２Ｈ５ＮＯ３－Ｈ２Ｏ体系中的耐腐蚀情况。研究结果表明：在无隔膜电解还原时，镀铂钛网上的Ｐｔ的腐蚀速率极低（＜２．５×１０－２μｍ／ａ），而在以阳离子交换膜作隔膜的电解还原中，镀铂钛网上的Ｐｔ有明显的腐蚀，其腐蚀速率为５．７μｍ／ａ。对这两种情况下Ｐｔ的腐蚀速率明显差别的原因进行了分析讨论。     

用于放射性滑膜切除的^153Sm—Citrate—HA的制备

介绍一种新放射性药物即钐［＾１５３Ｓｍ］－柠檬酸－羟基磷灰石，采用转换络合法进行标记。先将钐［＾１５３Ｓｍ］与柠檬酸络合，然后转换络合为羟基磷灰石（ＨＡ）的标记物，ＨＡ的络合容量约５ｍｇ（以Ｓｍ２Ｏ３计），标记物粒度主要为２－１０μｍ，标记率高达９８％。体外稳定性研究表明：标记物在生理盐水和人血浆蛋白溶液中放置三个半衰期，＾１５３Ｓｍ的总游离量小于２％。正常兔左后膝关节注射１４．８ＭＢｑ（４００μ     

~（99）Tc~m－HMPAO构效差异的研究──GSH水溶液中~（99）Tc￣

从化学动力学角度对ｄｌ－型和ｍｅｓｏ－型￣（９９）Ｔｃ￣ｍ－ＨＭＰＡＯ构效差异的原因进行了研究。通过测定￣（９９）Ｔｃ￣ｍ－ＨＭＰＡＯ两种异构体在ＧＳＨ和Ｌ－半胱氨酸水溶液中的解离反应的一级速率常数，比较了Ｌ－半胱氨酸和ＧＳＨ对￣（９９）Ｔｃ￣ｍ－ＨＭＰＡＯ作用，解释了ｄｌ－型和ｍｅｓｏ－型￣（９９）Ｔｃ￣ｍ－ＨＭＰＡＯ药效的差异，探讨了￣（９９）Ｔｃ￣ｍ－ｄｌ－ＨＭＰＡＯ在人脑中的贮留机理。     

C_(60)与甲苯的激光诱导反应

在激光辐照下,Ｃ６０与甲苯反应形成了一系列的富勒烯衍生物,对其中的可溶产物进行的高效液相色谱－质谱－紫外光谱（ＨＰＬＣ－ＭＳ－ＵＶ）分析研究表明,反应产物中包括Ｃ６０（Ｃ７Ｈ７）ｎ,Ｃ６０Ｈｎ,Ｃ６０（Ｃ７Ｈ７）ｎＯｍ等,它们的形成可能与甲苯在激光作用下形成的自由基有关,多级质谱（ＭＳ／ＭＳ）分析表明,这些衍生物是自由基链结在笼状Ｃ６０外围的结果。     

分光光度法测定dl—HMPAO冻干药盒中微量Sn（II）

采用分光光度法及Ｓｎ（Ⅱ）－Ｆｅ（Ⅲ）－邻二氮菲（Ｐｈｅｎ）体系测定ｄｌ－ＨＭＰＡＯ冻干药盒中微量Ｓｎ（Ⅱ）。在ｐＨ≈５的酸度下，Ｓｎ（Ⅱ）还原Ｆｅ（Ⅲ）生成红色的Ｆｅ（Ⅱ）－Ｐｈｅｎ配合物。该配合物的最大吸收波长λｍａｘ＝５１０ｎｍ，计算得到表观摩尔吸光系数为２．０×１０＾４ｌ·ｍｏｌ＾－１·ｃｍ＾－１。Ｓｎ（Ⅱ）浓度基０－２．５μｇ／ｍｌ内符合比尔定律。     

~（152）Sm的22－1019keV能区中子俘获截面的测量

在４．５ＭｅＶ静电加速器上．利用７Ｌｉ（ｐ，ｎ）７Ｂｅ和Ｔ（ｐ．ｎ）３Ｈｅ反应作为中子源，在２２－１０１９ｋｅＶ中子能区以（１９７）Ａｕ的中子俘获截面为标准，用活化法测量了（１５２）Ｓｍ的中子俘获截面．其误差小于６．８％。     

肿瘤内注射^90Y—GTMS治疗肝癌的实验研究：剂量与疗效的关系

荷瘤小鼠瘤内直接注射＾９０Ｙ－ＧＴＭＳ治疗实验性肝癌，以确定注射剂量与疗效的关系。在６个剂量（１．８７、３．７５、５．８２、７．９、９．３７、１８．５ＭＢｑ／ｃｍ＾３）组中，当注射的放射性浓度达到７．５ＭＢｑ／ｃｍ＾３时，肿瘤周边剂量为１０６．６Ｇｙ，整个肿瘤所受累积剂量为１３６．７Ｇｙ，此时肿瘤坏死大于５０％，肿瘤呈负生长；低于该剂量，肿瘤呈正生长。研究表明，肿瘤内直接注射＾９０Ｙ－ＧＴＭＳ，疗     

数字化PWM技术在电流传感器中的运用

提出了利用DSP实现PID控制,结合DSP芯片内部定时器模块产生PWM信号,最后由该信号通过反馈电路产生相应的补偿电流,根据被测电流与补偿电流的安匝比关系即可得到待测电流值。经过实验测试,该设计可用于交直流信号测量。研究证明,该技术使新型电流传感器具有高稳定性。     

A Precise Cyclic CMOS Time-to-Digital Converter With Low Thermal Sensitivity

In this paper, a precise cyclic CMOS time-to-digital converter (TDC) with low thermal sensitivity is proposed. Through compensation, the thermal sensitivity of the new cyclic time-to-digital converter is reduced dramatically. The proposed TDC not only possesses reduced thermal sensitivity but also has a small chip size. The circuit was fabricated with TSMC 0.35$mu$m CMOS technology. The size of the circuit is only 0.40 mm by 0.30 mm. The experimental results show that a$pm$6% resolution variation of the new TDC was achieved over 0$,^circhboxC$to 100$,^circhboxC$temperature range which is much better than the$pm$25% resolution variation of the original uncompensated version. The effective resolution is as fine as 57.3ps/LSB at room temperature with a fluctuation of$pm$3.5 ps over 0$,^circhboxC$to 100$,^circhboxC$temperature range, and the corresponding integral nonlinearities are all within$pm$0.8 LSB. The minimum measurement rate is 33 kHz. The measured power consumption is about 3.5 uW.     

Comparison of Hotelling observer models and human observers indefect detection from myocardial SPECT imaging

The objective of this study was to compare defect detection performance using a channelized Hotelling observer with radially symmetric channel (RSC) and oriented channels (OC) to that found in a previously reported human observer ROC study (see K.J. LaCroix and B.M.W. Tsui, “An evaluation ofthe effect of nonuniform attenuation compensation on defect detection for Tc-99m myocardial SPECT images,” J. Nucl. Med., vol. 38, p. 19P, 1997). The observer's task involved the detection of left-ventricular myocardial perfusion defects for Tc-99m sestamibi myocardial perfusion SPECT images. The images were reconstructed using the filtered-backprojection (FBP) algorithm without attenuation compensation or the maximum-likelihood expectation-maximization (ML-EM) algorithm with non-uniform attenuation compensation (AC). This was performed for cases with and without significant attenuation artifacts. The areas under the ROC curves for the Hotelling observers were calculated and compared to those for the human observers. The ML-EM reconstructed images (with AC) had high defect detectability across all anatomy types, while with FBP, a lower detectability was found for cases where the reconstructed images contained attenuation artifacts in the myocardium. Similar trends between the channelized Hotelling observer and those from the human observer study were found with both radially symmetric channel (RSC) and oriented-channel (OC) models. Further investigation of the channel models is needed to determine the number and alignment of orientations and the number and cutoff of frequency bands to improve agreement between human and Hotelling observer results     

Simultaneous compensation of 2nd-order parasitic aberrations in both principal sections of an achromatic quadrupole lens doublet

Experimental measurements are made of the aberrations of a doublet of achromatic quadrupole lenses. Second-order terms are altered and eliminated. Adjustment is guided by a theoretical model containing dipole and hexapole terms. Fixed hexapole terms of unknown magnitude arising from the inherent imperfect symmetry of lens construction cause the parasitic aberrations. Variable hexapole terms, caused by 2-pole electric excitations, are used to achieve compensation. The variable terms are adjusted to null the total hexapole field of each lens, leaving a small dipole field. Thus compensation of parasitic aberration is achieved at the expense of a small fixed image shift, which may be ignored or compensated by a beam-sweeping system. When a doublet with bore of 1 mm and working distance 10 cm is used to focus 1.2 MeV protons, aberrations less than 0.5 μm over an aperture of 0.4 × 0.5 mm are obtained. Alternative compensation methods require us of 5 separated lenses, 2 quadrupole and 3 hexapole. The field in each such hexapole lens is adjustable in magnitude and azimuth, requiring 6 parameters to be adjusted. A single such lens does not produce exact compensation. A method of compensation using the quadrupole lens structure is superior because construction and mechanical alignment of the 3 separate lenses is not required, and because only 4 parameters must be adjusted.     

A Novel Vacuum System Control Strategy for High Intensity D–T Fusion Neutron Generator

High intensity D–T fusion neutron generator (HINEG) is a high voltage accelerator-based D–T fusion neutron facility, which provides a significant platform for nuclear technology researches. The steady operation of HINEG vacuum system is enormously significant for its beam quality. In this paper, in order to eliminate the drawbacks and disadvantages caused by the time delay element in vacuum system, a gain adaptive compensation control strategy was proposed for vacuum system. In accordance with vacuum-pumping mechanism, the vacuum dynamic equilibrium equation was transformed from the time domain to the complex frequency domain by means of Laplace transformation, and the system transfer function in vacuum pumping process was derived. The experimental results analyses showed that the overshoot and settling time are eliminated effectively with this gain adaptive compensation control algorithm, which indicated that the system self-regulation and anti-interference performances were greatly improved.     

Iterative restoration of SPECT projection images

Photon attenuation and the limited nonstationary spatial resolution of the detector can reduce both qualitative and quantitative image quality in single photon emission computed tomography (SPECT). In this paper, a reconstruction approach is described which can compensate for both of these degradations. The approach involves processing the projection data with Bellini's method for attenuation compensation followed by an iterative deconvolution technique which uses the frequency distance principle (FDP) to model the distance-dependent camera blur. Modeling of the camera blur with the FDP allows an efficient implementation using fast Fourier transform (FFT) methods. After processing of the projection data, reconstruction is performed using filtered backprojection. Simulation studies using two different brain phantoms show that this approach gives reconstructions with a favorable bias versus noise tradeoff, provides no visually undesirable noise artifacts, and requires a low computational load     

A Novel Concept of Gamma-Ray Compensation for Neutron Ionization Chamber

A novel method of γ-ray compensation in a neutron ionization chamber (CIC) is developed as an ex-core nuclear instrumentation in a pressurized water reactor. To minimize the dependence of the compensation efficiency on γ-ray dose and dose rate, the improved CIC has the signal electrode with small holes to induce leakage or fringing electric fields. Change in compensation characteristics could be controlled by adjusting the field strength. It has been shown that the compensation margin for adjustment can be extended to 5-8%.     

Development of HL-2M data integration and acquisition system for magnetic diagnostics

Magnetic measurement and diagnostics are critical for the operation of magnetic confinement experimental facilities and plasma analysis,while differential signals are mostly detected by a detector.For this,we have developed and designed a stable and reliable data integration system for HL-2 M magnetic measurement and magnetic diagnostics.The system will be used for realtime control of HL-2 M after the construction of HL-2 M is completed.The system is built based on the PXI platform,and the software system is based on the LABVIEW platform.Key technologies realized by the system primarily include drift compensation,pulse data acquisition technology,multi-threading processing technology and transmission control communication protocol.Trials of the system were successfully carried out on HL-2 A,and the results showed that the system could fully meet the construction needs of HL-2 M.     

在线进样ICP-MS用于239Pu气溶胶活度浓度连续监测技术研究

为了弥补传统场所α气溶胶实时连续监测技术在后处理等场所239Pu气溶胶活度浓度连续监测方面探测能力和响应速度方面的不足,本文开展了基于ICP MS的空气中239Pu气溶胶连续监测技术研究。通过对气溶胶直接进样方法、ICP MS连续测量定量方法、238U干扰等方面研究工作的开展,建立了基于ICP MS、气溶胶直接进样系统和膜去溶雾化器联用的场所239Pu气溶胶活度浓度连续监测技术。在单次测量时间为1 min的情况下,依据ISO 11929（2019）计算得到本系统对239Pu气溶胶判断限和探测限分别为124×10-5 Bq/m3和248×10-5 Bq/m3,优于传统的基于PIPS的α气溶胶实时连续监测系统,远低于239Pu的导出空气浓度限值,证明该技术可为相关工艺场所239Pu气溶胶活度浓度连续监测提供快速高效的技术支持。     

Operating Characteristics of Lithium Drift Detectors

A study of the operating characteristics of diffused window lithium drift silicon detector has revealed that the level of compensation is independent of depth. The compensation corresponds to a net impurity concentration of 5 × 1010 impurities per cubic centimeter and is approximately three order of magnitude poorer than that set by current flow through a diode. Using time stability studies it is possible to differentiate between stability of compensation in the bulk or main body of the detector and in the window (diffused type) area of the diode. By appropriate biasing a lithium distribution can be obtained in the window area which has good time stability. The stability of the compensation in the bulk of the diode is sufficiently high that the diffused window detector will provide many years of operation, even when the detector is left largely unbiased.