Precision measurements of cosmic ray positrons are presented up to 1 TeV based on 1.9 million positrons collected by the Alpha Magnetic Spectrometer on the International Space Station. The positron ...flux exhibits complex energy dependence. Its distinctive properties are (a) a significant excess starting from 25.2±1.8 GeV compared to the lower-energy, power-law trend, (b) a sharp dropoff above 284_{-64}^{+91} GeV, (c) in the entire energy range the positron flux is well described by the sum of a term associated with the positrons produced in the collision of cosmic rays, which dominates at low energies, and a new source term of positrons, which dominates at high energies, and (d) a finite energy cutoff of the source term of E_{s}=810_{-180}^{+310} GeV is established with a significance of more than 4σ. These experimental data on cosmic ray positrons show that, at high energies, they predominantly originate either from dark matter annihilation or from other astrophysical sources.
Precision results on cosmic-ray electrons are presented in the energy range from 0.5 GeV to 1.4 TeV based on 28.1×10^{6} electrons collected by the Alpha Magnetic Spectrometer on the International ...Space Station. In the entire energy range the electron and positron spectra have distinctly different magnitudes and energy dependences. The electron flux exhibits a significant excess starting from 42.1_{-5.2}^{+5.4} GeV compared to the lower energy trends, but the nature of this excess is different from the positron flux excess above 25.2±1.8 GeV. Contrary to the positron flux, which has an exponential energy cutoff of 810_{-180}^{+310} GeV, at the 5σ level the electron flux does not have an energy cutoff below 1.9 TeV. In the entire energy range the electron flux is well described by the sum of two power law components. The different behavior of the cosmic-ray electrons and positrons measured by the Alpha Magnetic Spectrometer is clear evidence that most high energy electrons originate from different sources than high energy positrons.
Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 ...to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30 GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.
We present high-statistics, precision measurements of the detailed time and energy dependence of the primary cosmic-ray electron flux and positron flux over 79 Bartels rotations from May 2011 to May ...2017 in the energy range from 1 to 50 GeV. For the first time, the charge-sign dependent modulation during solar maximum has been investigated in detail by leptons alone. Based on 23.5×10^{6} events, we report the observation of short-term structures on the timescale of months coincident in both the electron flux and the positron flux. These structures are not visible in the e^{+}/e^{-} flux ratio. The precision measurements across the solar polarity reversal show that the ratio exhibits a smooth transition over 830±30 days from one value to another. The midpoint of the transition shows an energy dependent delay relative to the reversal and changes by 260±30 days from 1 to 6 GeV.
We report the properties of sodium (Na) and aluminum (Al) cosmic rays in the rigidity range 2.15 GV to 3.0 TV based on 0.46 million sodium and 0.51 million aluminum nuclei collected by the Alpha ...Magnetic Spectrometer experiment on the International Space Station. We found that Na and Al, together with nitrogen (N), belong to a distinct cosmic ray group. In this group, we observe that, similar to the N flux, both the Na flux and Al flux are well described by the sums of a primary cosmic ray component (proportional to the silicon flux) and a secondary cosmic ray component (proportional to the fluorine flux). The fraction of the primary component increases with rigidity for the N, Na, and Al fluxes and becomes dominant at the highest rigidities. The Na / Si and Al / Si abundance ratios at the source, 0.036 ± 0.003 for Na / Si and 0.103 ± 0.004 for Al / Si, are determined independent of cosmic ray propagation.
The AMS-02 TRD for the international space station Hauler, F.; Bartoloni, A.; Becker, U. ...
IEEE transactions on nuclear science,
2004-Aug., 2004-08-00, 20040801, Volume:
51, Issue:
4
Journal Article
Peer reviewed
The Alpha Magnetic Spectrometer (AMS-02) is an experiment which will be mounted on the international space station (ISS) to measure primary cosmic ray spectra in space. A key element is the ...transition radiation detector (TRD) to extract an e/sup +/ or p/sup -/ signal reducing the p/sup +/ or e/sup -/ background by a rejection factor 10/sup 2/--10/sup 3/ in an energy range from 10 to 300 GeV. This will be used in combination with an electromagnetic calorimeter to provide overall p/sup +/ rejection of 10/sup 6/ at 90% e/sup +/ efficiency. The detector consists of 20 layers of 6 mm diameter straw tubes alternating with 20 mm layers of polyethylene/polypropylene fleece radiator. The tubes are filled with a 4:1 mixture of Xe:CO/sub 2/ at 1 bar absolute pressure from a recirculating gas system designed to operate >3 years in space. There are in total 5248 straw tubes which are read out by a custom-made DAQ system in less than 80 /spl mu/s. The electronics must be low in power consumption and sustain the stringent requirements of operation in space. The construction of the detector and its electronics is presented in this paper.
This study describes the successful upgrade of a mechanically pumped CO2 two-phase cooling system in space by designing a new pump module for the Alpha Magnetic Spectrometer-02 on the International ...Space Station. Key factors for mission success are emphasized, including achieving high coolant filling accuracy within 10% of the target and maintaining system stability within ±1 °C. The impact of adding radiators to improve cooling efficiency is examined, and it is found that operating multi-radiators out-of-phase does not significantly affect system reliability. The centrifugal pump design is shown to allow for better lubricant circulation, while the in-house designed controller incorporates protective measures to prevent cavitation, overheating, and over-current. This research advances the understanding of circulation loop systems and their upgrades in space and demonstrates the potential for extending the lifetime of space-borne mechanically pumped two-phase cooling systems.
•First in-space upgrade of a pumped two-phase cooling system.•Quantitative on-orbit fluid transfer achieves 7% accuracy.•Superior system control stability of 1 °C with multiple out-f-phase radiators.•Prolonged mechanical pump lifetime via hardware and software manners.
The Transition Radiation Detector of the AMS-02 experiment on the International Space Station is used for the separation of cosmic-ray positrons and electrons from protons and anti-protons, and for ...the identification of nuclei up to carbon (Z≤6). We present the Geant4 simulation that is used to describe the ionization and transition radiation processes and compare its results to flight data from AMS-02. After applying empirical corrections to the simulated data, the particle energy deposition and likelihood distributions in the TRD are described with high accuracy.
Status of AMS-TRD-Straw modules Kirn, Th; Chung, C.H.; Dömmecke, F. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2004, Volume:
522, Issue:
1
Journal Article
Peer reviewed
The AMS02 experiment will be installed on the International Space Station for a data taking period of 3 years. The TRD consists of 20 layers of straw modules and fleece radiator with a total of 328 ...modules (16 straws each). The housing consists of a conically shaped octagon structure made out of CFC-Al-honeycomb material and is closed by a lower and upper honeycomb plate. The gas is a 80:20 Xe/CO
2 mixture. The straw modules will be operated in proportional mode at a gasgain of 3000. The signals are readout by VA chips. The detector is under construction at RWTH Aachen, the gas system will be built at MIT, slow-control at INFN Rome and DAQ at TH Karlsruhe. In the presentation special emphasis will be dedicated to the space qualification aspects and the status of the straw module production.
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