The design and the simulated performances of a compact detector dedicated to the measurement of GRB photon polarization is presented. Such a detector would permit to answer the question “are most of ...the GRB strongly polarized?” in a mission of one year in space.
Following the decision to maintain the International Space Station (ISS) on orbit until at least 2020 (possibly until 2028) the AMS collaboration decided to correspondingly extend the lifetime of the ...experiment. Since the limited amount of helium used to cool the superconducting magnet allowed for only a limited run time of the experiment, a change from the superconducting magnet to the permanent magnet used in AMS-01 became necessary. Due to the lower magnetic field, to maintain the resolution the silicon tracker also had to be reconfigured with the installation of a silicon plane on the top of the experiment and a new plane above the electromagnetic calorimeter.
As a space-borne detector POLAR is designed to conduct hard X-ray polarization measurements of gamma-ray bursts on a statistically significant sample of events and with an unprecedented accuracy. ...During its development phase a number of tests, calibrations and verification measurements were carried out in order to validate instrument functionality and optimize operational parameters. In this article we present results on gain optimization together with verification data obtained in the course of broad laboratory and environmental tests. In particular we focus on exposures to the 137Cs radioactive source and determination of the gain dependence on the high voltage for all 1600 detection channels of the polarimeter. Performance of the instrument is described in detail with respect to the dynamic range, energy resolution and temperature dependence. Gain optimization algorithms and response non-uniformity studies are also discussed. Results presented below are important for the development of the POLAR calibration and operation database.
Response of the Compton polarimeter POLAR to polarized hard X-rays Orsi, S.; Haas, D.; Hajdas, W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2011, Volume:
648, Issue:
1
Journal Article
Peer reviewed
POLAR is a novel compact space-borne Compton polarimeter conceived for a precise measurement of hard X-ray polarization and optimized for the detection of Gamma-Ray Burst (GRB) photons in the energy ...range 50–500keV. In December 2009 we have performed a systematic calibration of one modular unit of POLAR at four energy levels (200, 288, 356 and 511keV) with a 100% polarized synchrotron radiation source at the beam line ID15A at ESRF. The detector was displaced several times on the beam line in order to achieve a uniform illumination, which mimics the flux from a GRB placed on the zenith of the experiment. Several rotations of the detector on the beam axis allowed us to test the response of POLAR to several polarization angles. Two different analysis methods to reconstruct the polarization angle of the beam and the modulation factor μ100 are presented; the first relies on the existence of a unpolarized sample, produced by merging two data sets with orthogonal polarization directions, and is less dependent on systematic effects due to asymmetries in the detector; the second is independent from unpolarized measurements, and will likely be used to analyze the polarization of GRB during the flight. Both methods reconstruct the input polarization angle within 2° and produce modulation factors μ100 between 30% and 50% depending on the beam energy. Monte Carlo simulations performed with GEANT4 confirm the experimental results.
A method to localize gamma-ray bursts using POLAR Suarez-Garcia, E.; Haas, D.; Hajdas, W. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2010, Volume:
624, Issue:
3
Journal Article
Peer reviewed
Open access
The hard X-ray polarimeter POLAR aims to measure the linear polarization of the 50–500
keV photons arriving from the prompt emission of
γ
-ray
bursts (GRBs). The position in the sky of the detected ...GRBs is needed to determine their level of polarization. We present here a method by which, despite of the polarimeter incapability of taking images, GRBs can be roughly localized using POLAR alone. For this purpose scalers are attached to the output of the 25 multi-anode photomultipliers (MAPMs) that collect the light from the POLAR scintillator target. Each scaler measures how many GRB photons produce at least one energy deposition above 50
keV in the corresponding MAPM. Simulations show that the relative outputs of the 25 scalers depend on the GRB position. A database of very strong GRBs simulated at 10
201 positions has been produced. When a GRB is detected, its location is calculated searching the minimum of the
χ
2
obtained in the comparison between the measured scaler pattern and the database. This GRB localization technique brings enough accuracy so that the error transmitted to the 100% modulation factor is kept below 10% for GRBs with fluence
F
tot
≥
10
−
5
erg
cm
−
2
. The POLAR localization capability will be useful for those cases where no other instruments are simultaneously observing the same field of view.
The Alpha Magnetic Spectrometer (AMS) is a precision particle physics detector on the International Space Station (ISS) conducting a unique, long-duration mission of fundamental physics research in ...space. The physics objectives include the precise studies of the origin of dark matter, antimatter, and cosmic rays as well as the exploration of new phenomena. Following a 16-year period of construction and testing, and a precursor flight on the Space Shuttle, AMS was installed on the ISS on May 19, 2011. In this report we present results based on 120 billion charged cosmic ray events up to multi-TeV energies. This includes the fluxes of positrons, electrons, antiprotons, protons, and nuclei. These results provide unexpected information, which cannot be explained by the current theoretical models. The accuracy and characteristics of the data, simultaneously from many different types of cosmic rays, provide unique input to the understanding of origins, acceleration, and propagation of cosmic rays.
The AMS-02 silicon tracker: First year on ISS in space Rapin, D.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2013, Volume:
718
Journal Article
Peer reviewed
The AMS-02 particle physics experiment was installed on the International Space Station in May 2011 and is taking cosmic ray data since then. Its tracker, with a total active area of 6.75m2, is made ...of silicon microstrips detectors in the field of a permanent magnet. It measures the rigidity and charge sign and identifies the ion species by dE/dx. The status of the AMS-02 tracker and its operation, after first months of data taking in space, is presented, as well as its performances and potentialities.
We report the observation of new properties of primary cosmic rays He, C, and O measured in the rigidity (momentum/charge) range 2 GV to 3 TV with 90×10^{6} helium, 8.4×10^{6} carbon, and 7.0×10^{6} ...oxygen nuclei collected by the Alpha Magnetic Spectrometer (AMS) during the first five years of operation. Above 60 GV, these three spectra have identical rigidity dependence. They all deviate from a single power law above 200 GV and harden in an identical way.
We report on the observation of new properties of secondary cosmic rays Li, Be, and B measured in the rigidity (momentum per unit charge) range 1.9 GV to 3.3 TV with a total of 5.4×10^{6} nuclei ...collected by AMS during the first five years of operation aboard the International Space Station. The Li and B fluxes have an identical rigidity dependence above 7 GV and all three fluxes have an identical rigidity dependence above 30 GV with the Li/Be flux ratio of 2.0±0.1. The three fluxes deviate from a single power law above 200 GV in an identical way. This behavior of secondary cosmic rays has also been observed in the AMS measurement of primary cosmic rays He, C, and O but the rigidity dependences of primary cosmic rays and of secondary cosmic rays are distinctly different. In particular, above 200 GV, the secondary cosmic rays harden more than the primary cosmic rays.
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