The Alpha Magnetic Spectrometer (AMS) is a high-energy particle physics magnetic spectrometer installed on the International Space Station (ISS) in May 2011, successfully operating and taking data ...since then. The goal of the experiment is to carry out accurate measurements of galactic Cosmic Rays spectra in a wide energy range from GeV/n to TeV/n and search for rare components as hints of the presence of Dark Matter and Anti-Matter. The AMS instrument includes a Ring Imaging Čerenkov (RICH), which provides a precise measurement of the particle velocity and electric charge. The AMS-RICH layout follows a proximity focusing design with two radiators: at the center there are sodium fluoride tiles surrounded by silica aerogel ones. No significant indications of degradation of the radiator properties have been observed in more than 11 years of operation in space and 95% of the detection sensors is working nominally. The velocity and charge responses are stable in time and their resolution fulfills the design requirements. The impact of the RICH detector in the AMS physics program will be highlighted and the most recent results on light isotopes in cosmic rays will be discussed, with a particular attention to the AMS capabilities to identify Beryllium isotopes.
Space application: The AMS RICH Giovacchini, F.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2020, Letnik:
970
Journal Article
Recenzirano
A Ring Imaging Cherenkov detector is on board the Alpha Magnetic Spectrometer, for mass and charge identification of charged cosmic rays. AMS is a high-energy particle physics magnetic spectrometer ...in space, which was successfully installed at the International Space Station on May 2011 to perform accurate measurements of Galactic Cosmic Rays fluxes in the rigidity range from 1 GV to a few TV. The RICH detector provides AMS the capability to measure the light nuclei isotopic composition of CRs, in the kinetic energy range from a few GeV/nucleon to about 10 GeV/nucleon, so far largely uncovered by previous experiment. In addition, the RICH is a key detector in indirect search for Dark Matter looking at the antiproton and anti-deuteron rare species.
The detector has shown stable response during the past 8 years of continuous data taking and no significant indication of degradation has been observed. Once accounted for the extreme environmental conditions of the detector in space and their variation in time, the performances in velocity end charge measurements match the requirements. The different stages of the AMS-RICH construction, from design to commissioning through space qualification and characterization tests, are addressed in this paper, in the aim of highlighting the important aspects which contributed to the success of this detector, only of its kind operative in a long duration mission in space.
Performance in space of the AMS-02 RICH detector Giovacchini, F.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2014, Letnik:
766
Journal Article
Recenzirano
AMS-02 was successfully installed on the International Space Station (ISS) in May 2011, to perform precise measurements of galactic cosmic rays in the 100 MV to few TV magnetic rigidity range. Among ...several specialized sub-detectors, AMS-02 includes a Ring Imaging Cherenkov detector (RICH), which provides a precise measurement of the particle charge and velocity. The Cherenkov light is produced in a radiator made of silica aerogel and sodium fluoride and collected by means of an array of photomultiplier tubes. Since its launch to space, the detector has been taking data without failures; its functionality and data integrity are monitored and show stable response. In order to achieve the optimal detector performance, calibrations have been performed to account for the dependence of the photodetectors response on temperature and for effective non-uniformities in the detector. The knowledge gathered of the photon yield at the percent level resulted in a charge resolution of 0.3 charge units for He and 0.5 charge units for Si ions. The required precision in the measurements of the particle velocity at the per mil level demanded a more accurate determination of the aerogel refractive index. A map of the aerogel radiator refractive index has been directly inferred from in-flight high statistics data with a precision of Delta n/n<210 super(-5) Delta n/n<210-5 on average and its stability with time has also been checked. Finally, a velocity resolution of ~0.810 super(-3)~0.810-3 for He and ~0.510 super(-3)~0.510-3 for Z>5Z>5 ions has been obtained.
The AMS-02 RICH detector: Status and physics results Giovacchini, F.; Casaus, J.; Oliva, A.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2020, Letnik:
952
Journal Article
Recenzirano
The Alpha Magnetic Spectrometer (AMS-02) is a high-energy particle physics magnetic spectrometer installed on the International Space Station since May 2011, and operating continuously since then. ...Because of its large acceptance, long exposure time and particle identification capabilities, AMS-02 measures cosmic ray (CR) fluxes in the kinetic energy range between a fraction of GeV/n to multi-TeV/n with unprecedented precision. The AMS-02 Ring Imaging Cherenkov detector (RICH) provides a precise measurement of the particle velocity and charge. The detector has shown stable and nominal response during the past 7 years of continuous data taking without showing significant degradation. In combination with the Silicon Tracker momentum measurement, the RICH is able to measure the isotopic composition of the light elements (up to charge Z=5) in the kinetic energy range from a few GeV/n to about 10 GeV/n. This paper will focus on the separation of cosmic rays species with |Z|=1. For positive rigidities (Z=+1), the measurement of individual p and d fluxes and their ratio are important for the understanding of CR propagation in our galaxy, since deuterons are almost entirely the secondary products of interactions of cosmic rays with interstellar matter, while protons are mainly produced in astrophysical sources. The negative rigidity sample (Z=-1) is promising for indirect search of Dark Matter, looking at the p̄ and d̄ components. These species are rare secondary products of CR propagation and therefore an excess due to new physics could be more significantly seen on top of their faint expected flux. In particular, d̄ have never been observed so far in CR.
•AMS-02 experiment includes a RICH detector successfully operating in space.•RICH velocity measurement contributes to the AMS physics results.•Focus on detector performance for charge Z=1 particle and the associated physics relevance.•Isotopic Cosmic Rays composition with AMS-02.•Antideuteron search with AMS.
This paper presents the design and experimental testing of the robotic elbow exoskeleton NEUROBOTICS Elbow Exoskeleton (NEUROExos). The design of NEUROExos focused on three solutions that enable its ...use for poststroke physical rehabilitation. First, double-shelled links allow an ergonomic physical human-robot interface and, consequently, a comfortable interaction. Second, a four-degree-of-freedom passive mechanism, embedded in the link, allows the user's elbow and robot axes to be constantly aligned during movement. The robot axis can passively rotate on the frontal and horizontal planes 30° and 40°, respectively, and translate on the horizontal plane 30 mm. Finally, a variable impedance antagonistic actuation system allows NEUROExos to be controlled with two alternative strategies: independent control of the joint position and stiffness, for robot-in-charge rehabilitation mode, and near-zero impedance torque control, for patient-in-charge rehabilitation mode. In robot-in-charge mode, the passive joint stiffness can be changed in the range of 24-56 N·m/rad. In patient-in-charge mode, NEUROExos output impedance ranges from 1 N·m/rad, for 0.3 Hz motion, to 10 N·m/rad, for 3.2 Hz motion.
Transfemoral amputation is a debilitating condition that leads to long-term mobility restriction and secondary disorders that negatively affect the quality of life of millions of individuals ...worldwide. Currently available prostheses are not able to restore energetically efficient and functional gait, thus, recently, the alternative strategy to inject energy at the residual hip has been proposed to compensate for the lack of energy of the missing leg. Here, we show that a portable and powered hip exoskeleton assisting both the residual and intact limb induced a reduction of walking energy expenditure in four individuals with above-knee amputation. The reduction of the energy expenditure, quantified using the Physiological Cost Index, was in the range -10, -17 % for all study participants compared to walking without assistance, and between -2, -24 % in three out of four study participants compared to walking without the device. Additionally, all study participants were able to walk comfortably and confidently with the hip exoskeleton overground at both their self-selected comfortable and fast speed without any observable alterations in gait stability. The study findings confirm that injecting energy at the hip level is a promising approach for individuals with above-knee amputation. By reducing the energy expenditure of walking and facilitating gait, a hip exoskeleton may extend mobility and improve locomotor training of individuals with above-knee amputation, with several positive implications for their quality of life.Transfemoral amputation is a debilitating condition that leads to long-term mobility restriction and secondary disorders that negatively affect the quality of life of millions of individuals worldwide. Currently available prostheses are not able to restore energetically efficient and functional gait, thus, recently, the alternative strategy to inject energy at the residual hip has been proposed to compensate for the lack of energy of the missing leg. Here, we show that a portable and powered hip exoskeleton assisting both the residual and intact limb induced a reduction of walking energy expenditure in four individuals with above-knee amputation. The reduction of the energy expenditure, quantified using the Physiological Cost Index, was in the range -10, -17 % for all study participants compared to walking without assistance, and between -2, -24 % in three out of four study participants compared to walking without the device. Additionally, all study participants were able to walk comfortably and confidently with the hip exoskeleton overground at both their self-selected comfortable and fast speed without any observable alterations in gait stability. The study findings confirm that injecting energy at the hip level is a promising approach for individuals with above-knee amputation. By reducing the energy expenditure of walking and facilitating gait, a hip exoskeleton may extend mobility and improve locomotor training of individuals with above-knee amputation, with several positive implications for their quality of life.
Abstract
The measurement of cosmic-ray individual spectra provides
unique information regarding the origin and propagation of
astro-particles. Due to the limited acceptance of current space
...experiments, protons and nuclei around the “knee” region
(∼ 1 PeV) can only be observed by ground based
experiments. Thanks to an innovative design, the High Energy
cosmic-Radiation Detection (HERD) facility will allow direct
observation up to this energy region: the instrument is mainly based
on a 3D segmented, isotropic and homogeneous calorimeter which
properly measures the energy of particles coming from each direction
and it will be made of about 7500 LYSO cubic crystals. The read-out
of the scintillation light is done with two independent systems: the
first one based on wave-length shifting fibers coupled to
Intensified scientific CMOS cameras, the second one is made of two
photo-diodes with different active areas connected to a custom
front-end electronics. This photo-diode system is designed to
achieve a huge dynamic range, larger than 10
7
, while having a
small power consumption, few mW per channel. Thanks to a good
signal-to-noise ratio, the capability of a proper calibration, by
using signals of both non-interacting and showering particles, is
also guaranteed. In this paper, the current design and the
performance obtained by several tests of the photo-diode read-out
system are discussed.
As a consequence of limb loss, trans-femoral amputees exert 60% additional knee extension torque and 50% more plantar flexion torque in the healthy limb compared to non-amputees. In this paper, we ...developed an active knee-ankle-foot orthosis (KAFO) designed to assist the healthy leg of trans-femoral amputees in activities of daily living, such as walking, ascending/descending stairs, and transitioning from sit-to-stand with adequate range of motion, speed, and peak torque. Our KAFO was designed to exceed the performance of similar assistive devices reported in literature in terms of: 1) portability; 2) power; 3) compliance; and 4) versatility. It is based on one-degree-of-freedom active series-elastic actuators in both the knee and ankle, with an additional passive degree of freedom at the ankle level to allow natural inversion/eversion. The knee module consists of a worm-gear surrounded by two pre-compressed springs. The ankle actuator relies on a mechanically adjustable compliance system combined with a 4-bar linkage transmission. The actuators were designed to optimize the torque output at the joints while fulfilling low-power requirements. This novel KAFO is controlled with a three-layer structure. The optimized low level, based on a closed-loop torque controller, has adequate performances for the targeted application. The device is also shown to fulfill the three pre-defined functional requirements for all locomotion modes.
The “Time-Of-Flight” (TOF) system of the AMS-02 superconducting spectrometer, to be installed in the ISS International Space Station, consists of four layers of plastic scintillation counters. During ...the precursor mission AMS-01 (June 1998), a similar system successfully operated in space for 10 days. However, the AMS-02 TOF had to be redesigned taking into account the more stringent mass and power constraints of the AMS-02 detector. The main characteristics of the new TOF system are (a) capability to stand the high fringing field of AMS-02 superconducting magnet; (b) high redundancy of electronic components for unmanned operation of at least three years in the space station; (c) capability to operate in the space environment on the ISS. Counters and electronics have been extensively tested before the installation in the spectrometer.
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.
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