Fiber Bragg Grating Sensor for Strain Sensing in Low Temperature Superconducting Magnet

Fiber Bragg grating (FBG) sensor for monitoring the electromagnetic strain in a low temperature superconducting (LTS) magnet was studied. Before used to LTS magnet strain sensing, the strain response of the sensor with 1.54-mu m wavelength at liquid helium was experimentally studied. It was found that the wavelength shift showed good linearity with longitudinal applied loads and the strain sensitivity is constant at 4.2 K. And then, the hoop strain measurement of a LTS magnet was carried out on the basis of measured results. Furthermore, the finite element method (FEM) was used to simulate the magnet strain. The difference between the experimental and numerical analysis results is very small.

Modal correction for fiber-coupling efficiency in free-space optical communication systems through atmospheric turbulence

High-speed free-space optical communication systems have recently used fiber-optical components. The coupling efficiency with which the received laser beam can be coupled into a single-mode fiber is noticeably limited by atmospheric turbulence due to the degradation of its spatial coherence. Fortunately, adaptive optics (AO) can alleviate this limitation by partially correcting the turbulence-distorted wavefront. The coupling efficiency improvement provided by Zernike modal AO correction is numerically evaluated. It is found that the first 3-20 corrected polynomials can considerably improve the fiber-coupling efficiency. The improvement brought by AO is compared with that brought by a coherent fiber array. Finally, a hybrid technique that integrates AO and a coherent fiber array is proposed. Results show that the hybrid technique outperforms each of the two above-mentioned techniques. (C) 2009 Elsevier GmbH. All rights reserved.

Micro-PET探测器单元的研究

为了发展一种快速、准确、方便、低廉的医用肿瘤诊断设备——微型正电子断层扫描仪(Micro-PET),我们对它的探测单元进行了一系列实验研究。本文描述了探测单元的结构、信号读出网络、电子学及获取系统。整个探测系统的空间位置分辨达到1.02mm。H8500光电倍增管64路阳极输出响应最大值和最小值之比为3.1,说明它的阳极输出响应具有较好的一致性。

γ射线和PET用晶体单元相互作用特性的研究

γ射线与晶体单元的相互作用特性对于PET探测器的研制有着重要的参考意义. 通过实验测得了不同能量的γ射线在BGO, CsI, NaI3种闪烁晶体中的探测效率、能量分辨率等相互作用特性参数, 并与蒙特卡洛模拟结果进行了比较. 结果给出了最适合PET探测器的晶体单元.

用于HIRFL重离子治癌的PET成像实验研究与蒙特卡罗模拟

为了HIRFL重离子治癌的需要 ,使用两个位置灵敏闪烁体探测器组成了一个简单的PET成像系统 .对PET成像进行了实验研究 ,实验测量得到了物体成像以及γ射线能谱 ,对于 5 11keV全能峰处的能量分辨率为 18 6 % ,峰总比为 5 2 4 % .采用GEANT3程序对该系统进行了模拟计算 ,并与实验进行比较 ,最后对该系统进行了优化设计

22MeV/u的Fe离子在PET膜中引起的辐照效应研究

用能量为22MeV/u的Fe离子在室温和真空条件下辐照了多层堆叠的半晶质聚酯膜,采用傅里叶转换红外吸收光谱、紫外/可见吸收光谱和X射线衍射技术分析测量了辐照后聚酯膜的微观结构所发生的变化,详细研究了分子结构的变化和非晶化转变与离子剂量、离子在样品中的平均电子能损以及吸收剂量的依赖关系.分析结果表明:辐照导致化学键的断裂、新化学键的形成和非晶化转变.非晶化效应和化学键的断裂随离子剂量和电子能损的增加而增大,但变化的总量仅依赖于总的吸收剂量,表明在所涉及的能损范围里,辐照产生的变化与辐照离子的种类和能量没有直接的关系,而只决定于材料对辐照离子能量的吸收程度.

Ar离子辐照PET膜引起的表面结构和组分变化研究

用 35MeV u的Ar离子室温下辐照多层堆叠的半晶质的聚酯 (PET)膜 ,采用X射线衍射技术和X射线光电子谱仪分析研究了辐照引起的表面结构和组分的变化。结果表明 ,Ar离子辐照PET膜引起了明显的非晶化转变和化学键断裂 ,断键主要发生在甲氧基和羰基功能团上 ,并使这两个功能团中的C和O的比分相对减少。非晶化效应和化学键断裂同时依赖于离子的照射剂量和离子在样品表面的电子能量损失 ,剂量越高 ,表面电子能量损失越大 ,效应就明显。同时定性地讨论了结果

高能Ar离子辐照PET膜引起的表面改性研究

采用傅立叶转换的红外光吸收技术在反射方式下分析研究了 35MeV/uAr离子辐照半晶质PET膜引起的表面改性及其对吸收剂量的依赖性。结果表明 ,辐照导致PET膜中与晶态区域相关的吸收带强度随吸收剂量增加普遍减弱 ,而与非晶区域相关的吸收带强度随吸收剂量增加逐渐增加 ,表明辐照使PET膜发生了非晶化转变。化学键断裂主要发生在苯环的对位和酯的C—O键上 ,而苯环的基本结构在整个辐照过程中变化较小。非晶化效应和化学键断裂同时依赖于离子的照射剂量和样品表面的电子能量沉积。此外 ,在约 5.0MGy以上的吸收剂量 ,辐照还引起了炔端基团的形成 ,炔端基团浓度随吸收剂量的增加显著增加。对实验结果进行了定性解释。

高能Ar离子辐照PET引起的光吸收变化研究

采用紫外 -可见光吸收技术分析和研究了 35MeV/uAr离子辐照聚酯膜引起的光吸收改性 .结果表明 ,Ar离子轰击聚酯膜时引起了碳键的共轭体系形成 ,从而导致了紫外 -可见光区域中光吸收明显增加 ,光吸收增加的幅度依赖于离子的照射剂量、离子在样品中的平均电子能量损失以及光的波长 ,剂量越高 ,电子能损越大 ,光吸收增幅越大 ;而光的波长越长 ,光吸收的增加则越不明显 .利用测量到的光吸收曲线 ,同时还定量地研究了各种辐照条件下聚酯膜的光能隙和碳原子团的尺寸 .

Advance in in-beam PET

Tumor radiotherapy was a promising modality and over 100 years. Beams of heavy-charged particles show high RBE advantages and become the optimum tool for tumors therapy. Newly, along with the development of accelerators, scintillators, micro-electronics and computers, the heavy ion tumor therapy has been recognized more and developed.

25MeV/u Kr辐照下PET薄膜的损伤机制研究；Damage Mechanism of PET Irradiated by 25 MeV/u Kr Ions

通过25MeV/u86Kr离子辐照叠层结晶聚对苯二甲酸乙二醇酯膜(PET),在不同的电子能损(3.407.25keV/nm)和离子注量(5×10113×1012ions/cm2)辐照条件下,对Kr离子在PET中引起的辐照损伤效应进行了研究。借助傅里叶变换红外光谱分析,通过对样品的红外吸收峰进行扣除基底后的Lorentz拟合,分析了与主要官能团对应的吸收峰强度的变化趋势,研究了化学结构与组分在重离子辐照下的变化规律;利用X射线衍射光谱仪测量,研究了Kr离子在PET潜径迹中引起的非晶化过程,并通过对吸光度和非晶化强度随离子注量的指数衰减规律的分析,获得了不同电子能损离子辐照PET时主要官能团的损伤截面和非晶化截面及对应的潜径迹半径。

A TOF-PET prototype with position sensitive PMT readout

A prototype of time-of-flight positron emission computed tomography (TOF-PET) has been developed for acquiring the coincident detection of 511 keV gamma-rays produced from positron annihilation. It consists of two 80.5 mmx80.5 mm LYSO scintillator arrays (composed of 35 x35 pixel finger crystals) with the position sensitive photomultiplier tubes R2487 as the readout. Each array is composed of 2 mm x2 mm x 15 mm finger crystals and the average pixel pitch is 2.30 mm. The measured results indicate that the TOF information has the potential to significantly enhance the image quality by improving the noise variance in the image reconstruction. The best spatial resolution (FWHM) of the prototype for the pairs of 511 keV gamma-rays is 1.98 mm and 2.16 mm in the x and y directions, respectively, which are smaller than the average pixel pitch of 2.30 mm.