分类: 物理学 >> 核物理学 提交时间: 2024-02-07
摘要: We report on using synthetic silicon for a high-precision X-ray polarimeter comprising a polarizer and an analyzer, each based on a monolithic channel-cut crystal used at multiple Brewster reflections with a Bragg angle very close to 45. Experiments were performed at the BL09B bending magnet beamline of the Shanghai Synchrotron Radiation Facility using a Si(800) crystal at an X-ray energy of 12.914 keV. A polarization purity of 8.410-9was measured. This result is encouraging, as the measured polarization purity is the best-reported value for the bending magnet source. Notably, this is the firstly systematic study on the hard X-ray polarimeter in China, which is crucial for exploring new physics, such as verifying vacuum birefringence.
分类: 核科学技术 >> 核科学与技术 提交时间: 2023-12-10
摘要: X-ray photon correlation spectroscopy (XPCS) has emerged as a powerful tool for probing nanoscale dynamics of soft condensed matter and strongly correlated materials, offering high spatial resolution and high penetration capability. This technique requires high brilliance and beam coherence, which are not directly available at modern synchrotron beamlines in China. To pave the way for future XPCS experiments, we first modified the optical setup of the newly commissioned BL10U1 USAXS beamline at the Shanghai Synchrotron Radiation Facility (SSRF). Subsequently, we carried out XPCS measurements on silica suspensions of glycerol, which were opaque in appearance due to high concentrations. Image series were collected by a high frame-rate area detector. Comprehensive analysis was carried out, yielding the correlation functions and several key dynamic parameters. All results agree well with the theory of Brownian motion, demonstrating the feasibility of XPCS at SSRF. Eventually, by carefully optimizing the setup and analyzing algorithms, we achieved a time resolution of 2 ms, enabling characterization of millisecond dynamics in opaque systems.
分类: 物理学 >> 核物理学 提交时间: 2023-07-06
摘要: Proton computed tomography (CT) has a distinct practical significance in clinical applications. It eliminates 35% errors caused by the transformation of Hounsfield unit (HU) to relative stopping power (RSP) valueswhen using X-ray CT for positioning andtreatment planning systems (TPSs). Following the development of FLASH proton therapy, there are increased requirements for accurate and rapid positioning in TPSs. Thus, anewrapid proton CT imaging mode is proposed based on sparsely sampled projections. The proton beam wasboosted to 350 MeV by a compact proton linear accelerator (linac). In this study,thecomparisons of the proton scattering with the energyof 350 MeV and 230 MeV are conducted based on GEANT4simulations.Asthe sparsely sampledinformation associated with beam acquisitions at 12angles is not enough for reconstruction, X-ray CT is used as a prior image. The RSP map generated by converting the X-ray CT was constructed based onMonte Carlo simulations. Consideringtheestimationof the most likely path (MLP), the prior image-constrained compressed sensing (PICCS) algorithm isused to reconstruct images from twodifferent phantoms using sparse protonprojections of 350 MeV parallel proton beam. The results show that it is feasible to realize the proton image reconstruction with the rapid protonCT imaging proposed in this paper. It can produce RSP maps withmuchhigher accuracy for TPSs and fast positioning to achieve ultra-fast imaging for real-time image-guided radiotherapy(IGRT) in clinical proton therapyapplications.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2021-12-31
摘要: Doped elements in alloys significantly impact their performance. Conventional methods usually sputter the surface material of the sample, or their performance is limited to the surface of alloys owing to their poor penetration ability. The X-ray K-edge subtraction (KES) method exhibits great potential for the nondestructive in situ detection of element contents in alloys. However, the signal of doped elements usually deteriorates because of the strong absorption of the principal component and scattering of crystal grains. This in turn prevents the extensive application of X-ray KES imaging to alloys. In this study, methods were developed to calibrate the linearity between the grayscale of the KES image and element content. The methods were aimed at the sensitive analysis of elements in alloys. Furthermore, experiments with phantoms and alloys demonstrated that, after elaborate calibration, X-ray KES imaging is capable of nondestructive and sensitive analysis of doped elements in alloys.