Cm In Radial Direction Research Articles

Development of a 32-channel Beam Emission Spectroscopy diagnostic based on Neutral Beam Injection on HL-2A tokamak

Abstract A 32-channel Beam Emission Spectroscopy (BES) diagnostic has been installed and operated on HL-2A tokamak. It covers a wide spatial range of 32 cm in the radial direction (from r = 12 c m / ρ = 0.27 to r = 44 c m / ρ = 0.98 ) and 27 cm in the poloidal direction (from -13.5 cm to +13.5 cm) inside the plasma, providing a capability of measuring density fluctuations in different spatial locations. It has high temporal resolution, 2 MHz, and good spatial resolution, about 1 cm in radial direction and 1.2 cm in poloidal direction. A 2D fiber mount with 135 slots is designed and installed on the curved image plane. Each slot corresponds to a different spatial location inside the plasma. BES channels can be placed in any slots as needed for desired spatial location measurement. More channels can be added up to 128 channels without re-designing collecting optical path & replacing optical components. First experimental results have demonstrated great performance of the system with high signal to noise ratio. Turbulence eddy dynamics can be measured and studied from 2D fast imaging. It will be a keen diagnostic in future plasma turbulence research on HL-2A.

Precise orbit determination of the Sentinel-3A altimetry satellite using ambiguity-fixed GPS carrier phase observations

The Sentinel-3 mission takes routine measurements of sea surface heights and depends crucially on accurate and precise knowledge of the spacecraft. Orbit determination with a targeted uncertainty of less than 2 cm in radial direction is supported through an onboard Global Positioning System (GPS) receiver, a Doppler Orbitography and Radiopositioning Integrated by Satellite instrument, and a complementary laser retroreflector for satellite laser ranging. Within this study, the potential of ambiguity fixing for GPS-only precise orbit determination (POD) of the Sentinel-3 spacecraft is assessed. A refined strategy for carrier phase generation out of low-level measurements is employed to cope with half-cycle ambiguities in the tracking of the Sentinel-3 GPS receiver that have so far inhibited ambiguity-fixed POD solutions. Rather than explicitly fixing double-difference phase ambiguities with respect to a network of terrestrial reference stations, a single-receiver ambiguity resolution concept is employed that builds on dedicated GPS orbit, clock, and wide-lane bias products provided by the CNES/CLS (Centre National d’Etudes Spatiales/Collecte Localisation Satellites) analysis center of the International GNSS Service. Compared to float ambiguity solutions, a notably improved precision can be inferred from laser ranging residuals. These decrease from roughly 9 mm down to 5 mm standard deviation for high-grade stations on average over low and high elevations. Furthermore, the ambiguity-fixed orbits offer a substantially improved cross-track accuracy and help to identify lateral offsets in the GPS antenna or center-of-mass (CoM) location. With respect to altimetry, the improved orbit precision also benefits the global consistency of sea surface measurements. However, modeling of the absolute height continues to rely on proper dynamical models for the spacecraft motion as well as ground calibrations for the relative position of the altimeter reference point and the CoM.

Centimeter-level precise orbit determination for the HY-2A satellite using DORIS and SLR tracking data

The HY-2A satellite is the first ocean dynamic environment monitoring satellite of China. Centimeter-level radial accuracy is a fundamental requirement for its scientific research and applications. To achieve this goal, we designed the strategies of precise orbit determination (POD) in detail. To achieve the relative optimal orbit for HY-2A, we carried out POD using DORIS-only, SLR-only, and DORIS + SLR tracking data, respectively. POD tests demonstrated that the consistency level of DORIS-only and SLR-only orbits with respect to the CNES orbits were about 1.81 cm and 3.34 cm in radial direction in the dynamic sense, respectively. We designed 6 cases of different weight combinations for DORIS and SLR data, and found that the optimal relative weight group was 0.2 mm/s for DORIS and 15.0 cm for SLR, and RMS of orbit differences with respect to the CNES orbits in radial direction and three-dimensional (3D) were 1.37 cm and 5.87 cm, respectively. These tests indicated that the relative radial and 3D accuracies computed using DORIS + SLR data with the optimal relative weight set were obviously higher than those computed using DORIS-only and SLR-only data, and satisfied the requirement of designed precision. The POD for HY-2A will provide the invaluable experience for the following HY-2B, HY-2C, and HY-2D satellites.

The laser ranging experiment of the Lunar Reconnaissance Orbiter: Five years of operations and data analysis

We describe the results of the Laser Ranging (LR) experiment carried out from June 2009 to September 2014 in order to make one-way time-of-flight measurements of laser pulses between Earth-based laser ranging stations and the Lunar Reconnaissance Orbiter (LRO) orbiting the Moon. Over 4,000h of successful LR data are obtained from 10 international ground stations. The 20–30cm precision of the full-rate LR data is further improved to 5–10cm after conversion into normal points. The main purpose of LR is to utilize the high accuracy normal point data to improve the quality of the LRO orbits, which are nominally determined by the radiometric S-band tracking data. When independently used in the LRO precision orbit determination process with the high-resolution GRAIL gravity model, LR data provide good orbit solutions, with an average difference of ∼50m in total position, and ∼20cm in radial direction, compared to the definitive LRO trajectory. When used in combination with the S-band tracking data, LR data help to improve the orbit accuracy in the radial direction to ∼15cm. In order to obtain highly accurate LR range measurements for precise orbit determination results, it is critical to closely model the behavior of the clocks both at the ground stations and on the spacecraft. LR provides a unique data set to calibrate the spacecraft clock. The LRO spacecraft clock is characterized by the LR data to a timing knowledge of 0.015ms over the entire 5years of LR operation. We here present both the engineering setup of the LR experiments and the detailed analysis results of the LR data.

610 poster ACCELERATED PARTIAL BREAST IRRADIATION: A DOSIMETRIC COMPARISON OF PERI- AND POSTOPERATIVE IMPLANTS

the lumpectomy cavity is comprised at least 0.5 cm in radial direction by the balloon pressure. Although breast tissue is essentially uncompressible, i.e. density is nearby constant, it can be stretched. Let us consider CTV as a spherical crown of 1.5 cm width around a theoretical spherical lumpectomy cavity with radius RCAV. If the cavity radius were expanded by the balloon, CTV would be contained into a spherical crown of 1 cm width at some balloon radius, RBALLOON > RCAV. In this way, the minimum balloon volume required to cover up CTV by the prescription dose can be calculated as a cavity volume function. Results: An approximate solution is (volume unit in cc): VBALLOON 0.52(1.46VCAV 0.33 + 1.59) [eq. 1]. If we consider also air or seroma inside the CTV up to 10% in volume, uniformly distributed on a ring fitted to the balloon, we obtain: VBALLOON 0.52(1.42VCAV 0.33 + 1.26) [eq 2]. Exact calculations (points) and approximations (continuous curves) for both cases are showed in the graph. Horizontal lines indicate the available diameter range of spherical mammosite balloons: 4-5 cm and 5-6 cm.