106 research outputs found
Fast bolometric diagnostic in the RFX reversed field pinch experiment
No full textBolometric measurements are performed in the RFX reversed field pinch experiment by means of a low noise miniaturized multichannel metal resistor bolometer module. The first tests on RFX, an experiment with geometrical dimensions comparable with those of large tokamaks but characterized by a much faster plasma dynamics, show that this thin film bolometer can be operated with high bandwidth and high time resolution in very different fusion experiments. A new data analysis technique, which allows the derivation of the power absorbed by the bolometer at a high time resolution (Δt=3×10−5 s) for the study of fast phenomena is presented
High-yield thermalized positronium at room temperature emitted by morphologically tuned nanochanneled silicon targets
No full textNanochanneled silicon targets with high positron/positronium (Ps) conversion rate and efficient Ps cooling were produced. Morphological parameters of the nanochannels, such as their diameter and length, were adjusted to get a large fraction of thermalized Ps at room temperature being emitted into vacuum. Ps cooling measurements were conducted combining single-shot positron annihilation lifetime spectroscopy and Doppler spectroscopy of the 13S → 23P transition. 2γ-3γ annihilation ratio measurements were also performed to estimate the positron/Ps conversion efficiency. In a converter with nanochannel diameter of 7-10 nm and depth of 3.89 μm, ∼28% of implanted positrons with an energy of 3.3 keV was found to be emitted as Ps with a transverse kinetic energy of 11 ± 2 meV. The reduction of the nanochannels depth to 1.13 μm, without changing the nanochannel diameter, was found to result in a less efficient cooling, highlighting the presence of Ps reflection from the bottom end of nanochannels
High-yield thermalized positronium at room temperature emitted by morphologically tuned nanochanneled silicon targets
No full textInternational audienceNanochanneled silicon targets with high positron/positronium (Ps) conversion rate and efficient Ps cooling were produced. Morphological parameters of the nanochannels, such as their diameter and length, were adjusted to get a large fraction of thermalized Ps at room temperature being emitted into vacuum. Ps cooling measurements were conducted combining single-shot positron annihilation lifetime spectroscopy and Doppler spectroscopy of the 13S → 23P transition. 2γ–3γ annihilation ratio measurements were also performed to estimate the positron/Ps conversion efficiency. In a converter with nanochannel diameter of 7–10 nm and depth of 3.89 μm, ∼28% of implanted positrons with an energy of 3.3 keV was found to be emitted as Ps with a transverse kinetic energy of 11 ± 2 meV. The reduction of the nanochannels depth to 1.13 μm, without changing the nanochannel diameter, was found to result in a less efficient cooling, highlighting the presence of Ps reflection from the bottom end of nanochannels
The time-of-flight neutral particle analyzer and its calibration system for the RFX experiment
No full textMethod for measuring positron number in high intensity nanosecond positron bunches based on Poisson statistic
No full textA novel method for the measurement of the number of positrons contained in intense positron bunches is presented. The technique is based on the Poisson distribution of the number of gamma rays emitted by many simultaneous positron–electron annihilations in a small solid angle. The results have been found in good agreement with those achieved with a calibrated CsI(Tl) detector coupled to a photodiode. The small dimension of the required equipment and the reduced constraints of the technique open the possibility of monitoring, in complex positrons systems, the number of positrons at different positions that are too difficult to reach with other devices
CIRCUS: an autonomous control system for antimatter, atomic and quantum physics experiments
No full textA powerful and robust control system is a crucial, often neglected, pillar of any modern, complex physics experiment that requires the management of a multitude of different devices and their precise time synchronisation. The AEḡIS collaboration presents CIRCUS, a novel, autonomous control system optimised for time-critical experiments such as those at CERN’s Antiproton Decelerator and, more broadly, in atomic and quantum physics research. Its setup is based on Sinara/ARTIQ and TALOS, integrating the ALPACA analysis pipeline, the last two developed entirely in AEḡIS. It is suitable for strict synchronicity requirements and repeatable, automated operation of experiments, culminating in autonomous parameter optimisation via feedback from real-time data analysis. CIRCUS has been successfully deployed and tested in AEḡIS; being experiment-agnostic and released open-source, other experiments can leverage its capabilities
High-resolution MCP-TimePix3 imaging/timing detector for antimatter physics
No full textWe present a hybrid imaging/timing detector for force sensitive inertial measurements designed for measurements on positronium, the metastable bound state of an electron and a positron, but also suitable for applications involving other low intensity, low energy beams of neutral (antimatter)-atoms, such as antihydrogen. The performance of the prototype detector was evaluated with a tunable low energy positron beam, resulting in a spatial resolution of ≈ 12 mm, a detection efficiency of up to 40% and a time-resolution in the order of tens of ns
Advances towards gravitational studies of neutral atomic antimatter at AEgIS
No full textThe foreseen production of cold antihydrogen atoms at CERN's Antiproton Decelerator (AD) opened up the possibility to perform direct measurements of Earth's gravitational acceleration on antimatter bodies. This is one of the goals of the AEgIS collaboration: measure the value of g using a pulsed source of cold antihydrogen and a moiré deflectometer/TalbotLau interferometer. The milestones achieved so far by AEgIS, on the way of developing a pulsed cold antihydrogen source using resonant charge-exchange between antiprotons and cold Rydberg positronium, are reviewd. First, the procedure developed to capture, manipulate and prepare a cold plasma of antiprotons for antihydrogen production is summarized. Antiprotons were captured from the AD using aluminum degraders and cooled with electrons. These mixed e-/p+ plasma were radially compressed to sub-mm radii applying a rotating-wall drive and progressively reducing the number of cooling electrons. Antiprotons were finally transferred in high numbers to the antihydrogen production trap using an efficient in-flight launch and recapture procedure. Second, the many milestones achieved by AEgIS in producing, manipulating and studying Ps are summarized. Ps has been first studied in a dedicated setup for spectroscopy experiments at room temperature using nanoporous silica positron-positronium converters in a reflection geometry. The spectroscopy of its 1-3 and 3-15 transitions was carried out, first showing the feasibility of AEgIS' proof-of-concept in-flight laser excitation. These experiments yielded as a byproduct the development of a long-lived source of metastable 23S Ps atoms, which may be considered in the future as an alternative to long-lived Rybderg Ps to directly probe gravity on positronium. Ps was subsequently formed also from the 10K cryogenic converter inside the main AEgIS experiment, leading to the first Ps laser excitation to the Rydberg levels in a 1T magnetic field and to the detailed characterization of the Ps source for antihydrogen production
Gravity and antimatter: The AEgIS experiment at CERN
No full textFrom the experimental point of view, very little is known about the gravitational interaction between matter and antimatter. In particular, the Weak Equivalence Principle, which is of paramount importance for the General Relativity, has not yet been directly probed with antimatter. The main goal of the AEgIS experiment at CERN is to perform a direct measurement of the gravitational force on antimatter. The idea is to measure the vertical displacement of a beam of cold antihydrogen atoms, traveling in the gravitational field of the Earth, by the means of a moiré deflectometer. An overview of the physics goals of the experiment, of its apparatus and of the first results is presented
Experiments with mid-heavy antiprotonic atoms in AEgIS
No full textAntiprotonic atoms have been fundamental in experiments which provide the most precise data on the strong interaction between protons and antiprotons and of the neutron skin of many nuclei thanks to the clean annihilation signal. In most of these experiments, the capture process of low energy antiprotons was done in a dense target leading to a significant suppression of specific transitions between deeply bound levels that are of particular interest. In particular, precise measurements of specific transitions in antiprotonic atoms with Z>2 are sparse. We propose to use the pulsed production scheme developed for antihydrogen and protonium for the formation of cold antiprotonic atoms. This technique has been recently achieved experimentally for the production of antihydrogen at AEgIS. The proposed experiments will have sub-ns synchronization thanks to an improved control and acquisition system. The formation in vacuum guarantees the absence of Stark mixing or annihilation from high n states and together with the sub-ns synchronization would resolve the previous experimental limitations. It will be possible to access the whole chain of the evolution of the system from its formation until annihilation with significantly improved signal-to-background ratio
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