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Precise measurements of primary cosmic ray Neon, Magnesium and Silicon flux is important to understand the origins and propagation properties of heavy elements in the Galaxy. This thesis presents the measurements of Neon, Magnesium, and Silicon flux in the rigidity (momentum per unit charge) range from 2.15 GV to 3 TV, with 5.6 million Ne, Mg, and Si nuclei events collected during 7 years of AMS operation (2011- 2018). The three fluxes show identical rigidity dependence above 86.5 GV, deviating from a single power law and hardening at high rigidity above 200 GV. Surprisingly, the rigidity dependence of Neon, Magnesium, and Silicon flux is different from the rigidity dependence of primary nuclei Helium, Carbon and Oxygen, even though the two groups are both primaries produced at cosmic rays sources.
Primary nuclei (He, C, O, Ne, Mg, Si, ...) are thought to be mainly produced and accelerated in astrophysical sources such as the supernova. Secondary nuclei (Li, Be, B, ...) are mostly produced by interactions of primary nuclei with the interstellar medium. Precise knowledge of the secondary-to-primary flux ratio, like B/C, is essential in the understanding of cosmic ray propagation. This thesis presents the first precision measurements of the heavy cosmic ray fluorine (F), sodium (Na), and aluminum (Al) fluxes in the rigidity range from 2.15 GV to 3.0 TV, based on data collected by the Alpha Magnetic Spectrometer (AMS) during the first 8.5 years of operation. The F flux is believed to be the only pure secondary flux between oxygen and silicon, and Na and Al fluxes are thought to be produced both in astrophysical sources and by the collisions of heavier nuclei with the interstellar medium.
The Alpha Magnetic Spectrometer (AMS) is a particle detector installed on the International Space Station; it starts to record data since May 2011. The experiment aims to identify the nature of charged cosmic rays and photons and measure their fluxes in the energy range of GeV to TeV. These measurements enable us to refine the cosmic ray propagation models, to perform indirect research of dark matter and to search for primordial antimatter (anti-helium). In this context, the data of the first years have been utilized to measure the electron flux and lepton flux (electron + positron) in the energy range of 0.5 GeV to 700 GeV. Identification of electrons requires an electrons / protons separation power of the order of 104, which is acquired by combining the information from different sub-detectors of AMS, in particular the electromagnetic calorimeter (ECAL), the tracker and the transition radiation detector (TRD). In this analysis, the numbers of electrons and leptons are estimated by fitting the distribution of the ECAL estimator and are verified using the TRD estimator: 11 million leptons are selected and analyzed. The systematic uncertainties are determined by changing the selection cuts and the fit procedure. The geometric acceptance of the detector and the selection efficiency are estimated thanks to simulated data. The differences observed on the control samples from data allow to correct the simulation. The systematic uncertainty associated to this correction is estimated by varying the control samples. In total, at 100 GeV (resp. 700 GeV), the statistic uncertainty of the lepton flux is 2% (30%) and the systematic uncertainty is 3% (40%). As the flux generally follows a power law as a function of energy, it is important to control the energy calibration. We have controlled in-situ the measurement of energy in the ECAL by comparing the electrons from flight data and from test beams, using in particular the E/p variable where p is momentum measured by the tracker. A second method of absolute calibration at low energy, independent from the tracker, is developed based on the geomagnetic cutoff effect. Two models of geomagnetic cutoff prediction, the Störmer approximation and the IGRF model, have been tested and compared. These two methods allow to control the energy calibration to a precision of 2% and to verify the stability of the ECAL performance with time.
Secondary cosmic rays are mainly produced by the collisions of nuclei with the interstellar medium. The precise knowledge of secondary cosmic rays is important to understand the origin and propagation of cosmic rays in the Galaxy. In this thesis, my work on the precision measurement of secondary cosmic rays Li, Be, and B in the rigidity (momentum/charge) range 1.9 GV to 3.3 TV with a total of 5.4 million nuclei collected by AMS is presented. The total error on each of the fluxes is 3%-4% at 100 GV, which is an improvement of more than a factor of 10 compared to previous measurements. Unexpectedly, the results show above 30 GV, these three fluxes have identical rigidity dependence and harden identically above 200 GV. In addition, my work on a new method of the tracker charge measurement leads to significant improvements in the AMS charge resolution, thus paving the way for the unexplored flux measurements of high Z cosmic rays.
A precision measurement of the Boron to Carbon ratio in cosmic rays is carried out in the range 1 GeV/n to 670 GeV/n using the first 30 months of flight data of AMS-02 located on the International Space Station. Above 20 GeV/n, it is the first accurate measurement. About 5 million clean Boron and Carbon nuclei are identified. The experimental and analysis challenges in achieving a high precision measurement are addressed. Boron is exclusively produced as a secondary particle by spallation from primary elements like Carbon in collisions with interstellar medium. The unprecedented precision and energy range of this measurement deepen the knowledge of cosmic ray propagation. Using this measurement, the diffusion coefficient in Gal-Prop model is determined to be (6.05 ± 0.05)10^28 cm2/s, and the Alfven velocity is (33.9 ± 1.0) km/s. This makes the prediction of secondary anti-proton background in dark matter search one order of magnitude more accurate.