Closed orbit feedback system for the fast ramping hadron synchrotrons

The realization of a fast and robust closed orbit feedback (COFB) system for the on-ramp orbit correction at SIS18 synchrotron of FAIR project is reported in this thesis. SIS18 has some peculiar behaviors including on-ramp optics variation, very short lengths of the ramps (200 ms to 1 s) and a cycle-to-cycle variation of beam parameters. The realized fast COFB system being robust against above mentioned features of SIS18 is a first of its kind and the course to its realization led to some novel contributions in the field of closed orbit correction. A new method relying on the discrete Fourier transform (DFT)-based decomposition of the orbit response matrix (ORM) has been introduced, exploiting the symmetry in the arrangement of beam position monitors (BPMs) and the corrector magnets in the synchrotrons. A nearest-circulant approximation has also been introduced for synchrotrons having slight deviation from the symmetry, making the method applicable to a vast majority of synchrotrons. Moreover, the performance and the stability analysis of COFB systems in the presence of ORM mismatch between the synchrotron and the feedback controller is presented. The COFB systems are divided into slow and fast regimes and a new stability criterion consistent with measurements, is introduced. The practicality of the criterion is verified experimentally at COSY Jülich and is used for the analysis of various sources of ORM mismatch at SIS18. The commissioning of the SIS18 COFB system is also reported in detail which relies on Libera Hadron as the main hardware resource for the controller implementation. The on-ramp orbit correction is demonstrated for the horizontal plane of SIS18, for the disturbance rejection up to 600 Hz.

THE SUPERSONIC ARGON FLOW PARAMETERS IN AN ARCJET THRUSTER

A small closed volume occupied by the gas plasma is a specific feature of the propulsion systems for orbit correction of spacecraft (PSSC). We found the temperature of argon in the PSSC chamber using emission spectroscopy methods in the approximation of partial local thermal equilibrium.

Assessment of Different Real Time Precise Point Positioning Correction Over the Sea Area

In a global scale, the accuracy of Real Time Precise Point Positioning (RT-PPP) method in Global Navigation Satellite System (GNSS) point positioning is within cm to dm level. Unlike other conventional method in GNSS point positioning which used differential data to minimize the error sources, RT-PPP used additional orbit correction, clock correction and other atmospheric correction to minimize the error since RT-PPP is an absolute point positioning method. Currently, there are several providers who give the orbit correction and clock correction in real-time. Not only in the land area, this service can be also used in sea area. Thus, this research aims to analyse the differences in point determination derived from RT-PPP method by using several service providers in sea area. The RT-PPP data acquisition used three different receivers with unique service correction, namely RTX correction from Trimble Net R9 receiver, ATLAS correction from Hemisphere receiver and Veripos correction from Hemisphere receiver. All these antennas were set up on the ship with a controlled distance and the point coordinates were estimated from Seribu Island to Ancol, Jakarta with a different time interval for each receiver due to the technical limitations. To assess the point positioning stability, the distance between each antenna derived from point positioning then evaluated by comparing to its controlled distance. The results indicate that a time lag is found in Trimble Net R9 compared with the others, and it should be corrected first before applying the further analysis. In general, after removing the outliers, the distance and the precision between each antenna between Veripos-ATLAS is 4.472 ± 0.040 m, RTX-ATLAS is 2.054 ± 0.077 m and RTX-Veripos is 3.947 ± 0.060 m. Therefore, RT-PPP method can be used as an alternative in precise point positioning in sea area.