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.

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.

双重辐射源~9C束流在其Bragg峰区对细胞致死效应增强的生物物理机制

相对12C束流而言,β缓发粒子衰变放射性9C束流在其Bragg峰区附近深度对细胞的致死效应明显增强,这已经在我们先前的研究中证实.9C束流的相对生物学效应(RBE)较12C束流要大1倍以上.本研究旨在探讨造成这一重要实验现象的生物物理机理.首先,建立模型计算了用于实验时产生的9C束流的阻止沉积几率密度分布,模型考虑了初始束流的动量分布,束流随贯穿深度增加由核反应导致的离子通量衰减和能量损失岐离等效应.发现9C束流对细胞致死效应增强的区域出现在入射9C离子的阻止沉积区域.其次,以9C束流入射处剂量为1Gy为例,根据计算得到的入射9C离子阻止分布几率密度推导了9C束流在不同贯穿深度上的沉积离子密度,进而得到了不同深度上每细胞内平均沉积9C离子数;同时,由相近剂量平均传能线密度(LET)深度上9C和12C束流实验上测得的细胞存活率推导出了9C及12C束流在这些深度上导致的每细胞平均致死事件数.研究结果表明,在照射剂量相同时每细胞平均沉积9C离子数与9C及12C束流每细胞平均致死事件数之差竟相吻合.由此推测,一个沉积9C离子将造成该细胞死亡.考虑到由9C衰变而发射低能粒子的性质,9C离子细胞中沉积可能会在该细胞中造成团簇损伤,因而本研究结果可作为辐射团簇损伤高效细胞致死的间接证据.

Enhanced biological effect induced by a radioactive C-9-ion beam at the depths around its Bragg peak

To explore the potential of double irradiation source, radioactive C-9-ion beam, in tumor therapy, a comparative study oil the surviving effect of human salivary gland cells at different penetration depths between C-9 and C-12-ion beams has been carried out. The 9C-ion C beam, especially at the distal side of the beam came out more efficient in cell killing at the depths around its Bragg peak than the 12 Bragg peak. Compared to the C-12 beam, an increase in RBE by a factor of up to 2.13 has been observed at the depths distal to the Bragg peak of the 9C beam. The 9C beam showed an enhanced biological effect at the penetration depths around its Bragg peak, corresponding to the stopping region of the incident C-9-ions and where the delayed low-energy particles were emitted. Further analysis revealed that cell lethality by the emitted particles from the stopping C-9-ions is responsible for the excessive biological effect at the penetration depths around the Bragg peak of the C-9 beam.

位置灵敏Bragg探测器的研制

位置灵敏Bragg探测器的研制，是为实现戴光曦老师提出的设想：在Bragg探测器的内部实现对位置测量而进行的一项研究工作。这项工作的实现对中、低能重离子核反应完成对裂片的测量是很有意义的。本工作采用电阻串进行电荷分除来定位，这在近物所为第一次。试验中，同时测量位置，能量及电荷对~(252)C+源的α粒子可以达到：ΔE/E = 1.9%, ΔZ/Z = 1.6% ΔX好于9mm

Stability of Mo/Si multilayer structure used in Bragg-Fresnel optics

The thermal and chemical stabilities of Mo/Si multilayer structure used in Bragg-Fresnel optics were studied to get optimal technological parameters of pattern generation. Mo/Si multilayers were annealed at temperature ranging from 360 to 770 K, treated with acetone and 5 parts per thousand NaOH solution, and characterized by small-angle x-ray diffraction technique as well as x-ray photoelectron spectroscopy, and Olympus microscopy.

Bottom simulating reflector and gas seepage in Okinawa Trough: Evidence of gas hydrate in an active back-arc basin

To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea (ECS) shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom simulating reflector (BSR) occurrence, but it is very rare. Besides several BSRs, a gas seepage was also found. As shown by the data, both the BSR and gas seepage are all related with local geological structures, such as mud diapir, anticline, and fault-controlled graben-like structure. However, similar structural "anomalies" are quite common in the tectonically very active Okinawa Trough region, but very few of them have developed BSR or gas seepage. The article points out that the main reason is probably the low concentration of organic carbon of the sediment in this area. It was speculated that the rare occurrence of gas hydrates in this region is governed by structure-controlled fluid flow. Numerous faults and fractures form a network of high-permeability channels in the sediment and highly fractured igneous basement to allow fluid circulation and ventilation. Fluid flow in this tectonic environment is driven primarily by thermal buoyancy and takes place on a wide range of spatial scales. The fluid flow may play two roles to facilitate hydrate formation: to help gather enough methane into a small area and to modulate the thermal regime.