Calibración de monitores de posición del haz basados en medidas ópticas

  1. Garcia-Tabares Valdivieso, Ana
Dirigida por:
  1. Rogelio Tomás García Director/a

Universidad de defensa: Universidad Complutense de Madrid

Fecha de defensa: 08 de noviembre de 2019

Tribunal:
  1. Juan Abel Barrio Uña Presidente
  2. Joseluis Contreras Gonzalez Secretario/a
  3. Barbara Dalena Vocal
  4. Ubaldo Iriso Ariz Vocal
  5. Concepción Celia Oliver Amorós Vocal

Tipo: Tesis

Teseo: 151486 DIALNET

Resumen

Accurate measurements of the focusing properties of an accelerator are extremely important for a proper operation of a synchrotron, both for the machine protection and for the experiments- performance. Measurement of linear optics functions based on turn-by-turn measurements have been constantly developed in pursuit of more accurate results. Optics functions, that describe the focusing properties of the machine, can be obtained from different observables: phase and amplitude of the transverse betatron oscillations and the change of the tune by modulating the current of quadrupoles (K-modulation). Reconstruction of linear optics using the phase, in combination with K-modulation, have been the main approaches for obtaining the beta function in accelerators all over the world. Measurements of optics functions based on the amplitude have not been used as widely as the other methods since it requires accurate beam-position-monitor (BPM) calibration. BPMs are key elements in accelerator operation, providing essential information about different beam parameters that are directly related to the accelerator performance. In order to obtain an accurate conversion from an induced voltage to the center of charge position, the BPMs have to be calibrated prior to its installation in the accelerator. This calibration procedure can only be performed when the accelerator is in a period of non-activity and does not completely reproduce the exact conditions that occur during the machine operation. First, a study of the error-bar associated to the measured beta from amplitude-function is introduced using an analytically formalism that has been contrasted with simulations and experimental results. Second, a study of the BPM calibration factors based on optics measurements has been developed as part of this research. Discrepancies observed during the optics measurements at the Large Hadron Collider (LHC) and the Proton Synchrotron Booster (PSB) show that the impact of the BPM calibration factors on the optics functions was greater than expected from the design values and tolerances. Measurement of the optics functions allows obtaining extra information on BPM calibration together with its associated uncertainty and resolution. This thesis summarizes the development of two different techniques to accurately compute the BPMs calibration factors based on optics measurements calculations. These approaches have been developed using as a test bench the LHC and the PSB and it is foreseen to extrapolate them to future accelerators. In case of LHC, the optics developed for computing the calibration factors only allows to accurately calibrate a limited range of BPMs located in the vicinity of the experiments denoted as IRs. The implementation of this approach in LHC and PSB is introduced in this thesis together with a summary of the hardware and software upgrades needed for its implementation. In case of LHC, calibration factors have been implemented in different machine configurations, in which the beta-function can be measured accurately using the three different approaches previously introduced: beta from phase, beta from amplitude and K-modulation. In LHC IRs BPMs a systematic deviation of the BPM calibration was observed when reconstructing the beta function using the beta from amplitude method with respect to the results obtained using the beta from phase approach. By compensating the effect of the calibration factors in the measured beta from amplitude function, the average accuracy of the beta-function has improved in a 6 per-cent in Beam 1 and 4 per-cent in Beam 2 with respect to the direct measured beta from amplitude-function. On the other hand, in case of PSB, calibrating the BPMS using an optics-based approach has allowed to decrease the beta-function error bar, previously computed using the beta from phase approach, by a factor of three.