Wakefield acceleration Tajima, T.; Yan, X. Q.; Ebisuzaki, T.
Reviews of modern plasma physics,
12/2020, Letnik:
4, Številka:
1
Journal Article
Odprti dostop
The fundamental idea of Laser Wakefield Acceleration (LWFA) is reviewed. An ultrafast intense laser pulse drives coherent wakefields of relativistic amplitude with the high phase velocity robustly ...supported by the plasma. The structures of wakes and sheaths in plasma are contrasted. While the large amplitude of wakefields involves collective resonant oscillations of the eigenmode of the entire plasma electrons, the wake phase velocity ~
c
and ultrafastness of the laser pulse introduce the wake stability and rigidity. When the phase velocity gets smaller, wakefields turn into sheaths. When we deploy laser ion acceleration or high density LWFA in which the phase velocity of plasma excitation is low, we encounter the sheath dynamics. A large number of world-wide experiments show a rapid progress of this concept realization toward both the high energy accelerator prospect and broad applications. The strong interest in this has driven novel laser technologies, including the Chirped Pulse Amplification, the Thin Film Compression (TFC), the Coherent Amplification Network, and the Relativistic Compression (RC). These in turn have created a conglomerate of novel science and technology with LWFA to form a new genre of high field science with many parameters of merit in this field increasing exponentially lately. Applications such as ion acceleration, X-ray free electron laser, electron and ion cancer therapy are discussed. A new avenue of LWFA using nanomaterials is also emerging, adopting X-ray laser using the above TFC and RC. Meanwhile, we find evidence that the Mother Nature spontaneously created wakefields that accelerate electrons and ions to very high energies.
Mini-EUSO is a space experiment selected to be installed inside the International Space Station. It has a compact telescope with a large field of view (44 × 44 sq. deg.) focusing light on an array of ...photo-multipliers tubes in order to observe UV emission coming from Earth’s atmosphere. Observations will be complemented with data recorded by some ancillary detectors. In particular, the Mini-EUSO Additional Data Acquisition System (ADS) is composed by two cameras, which will allow us to obtain data in the near infrared, and in the visible range. These will be used to monitor the observation conditions, and to acquire useful information on several scientific topics to be studied with the main instrument, such as the physics of atmosphere, meteors, and strange quark matter. Here we present the ADS control software developed to stream cameras together with the UV main instrument, in order to grab images in an automated and independent way, and we also describe the calibration activities performed on these two ancillary cameras before flight.
ABSTRACT
Gamma-ray observations have revealed strong variability in blazar luminosities in the gamma-ray band over time-scales as short as minutes. We show, for the first time, that the correlation ...of the spectrum with intensity is consistent with the behaviour of the luminosity variation of blazar spectral energy distributions (SEDs) along a blazar sequence for low synchrotron peak blazars. We show that the observational signatures of variability with flux are consistent with wakefield acceleration of electrons initiated by instabilities in the blazar accretion disc. This mechanism reproduces the observed time variations as short as 100 s. The wakefield mechanism also predicts a reduction of the electron spectral index with increased gamma-ray luminosity, which could be detected in higher energy observations well above the inverse Compton peak.
Accreting blackholes such as miniquasars and active galactic nuclei can contribute to the highest energy components of intra- (∼10
15
eV) galactic and extra-galactic components (∼10
20
eV) of ...cosmic rays. Alfven wave pulses which are excited in the accretion disk around blackholes propagate in relativistic jets. Because of their highly non-linear nature of the waves, charged particles (protons, ions, and electrons) can be accelerated to high energies in relativistic jets in accreting blackhole systems, the central engine of miniquasars and active galactic nuclei.
Context . Observations of meteors in the Earth’s atmosphere offer a unique tool for determining the flux of meteoroids that are too small to be detected by direct telescopic observations. Although ...these objects are routinely observed from ground-based facilities, such as meteor and fireball networks, space-based instruments come with notable advantages and have the potential to achieve a broad and uniform exposure. Aims . In this paper, we describe the first observations of meteor events with Mini-EUSO, a very wide field-of-view telescope launched in August 2019 from the Baikonur cosmodrome and installed on board the Russian Zvezda module of the International Space Station. Mini-EUSO can map the night-time Earth in the near-UV range (290-130 nm) with a field of view equal to 44° × 44° and a spatial resolution of about 4.7 km at an altitude of 100 km from the ground. The detector saves triggered transient phenomena with a sampling frequency of 2.5 µs and 320 µs, as well as a continuous acquisition at 40.96 ms scale that is suitable for meteor observations. Methods . We designed two dedicated and complementary trigger methods, together with an analysis pipeline able to estimate the main physical parameters of the observed population of meteors, such as the duration, horizontal speed, azimuth, and absolute magnitude. To compute the absolute flux of meteors from Mini-EUSO observations, we implemented a simulation framework able to estimate the detection efficiency as a function of the meteor magnitude and the background illumination conditions. Results . The instrument detected 24 thousand meteors within the first 40 data-taking sessions from November 2019 to August 2021, for a total observation time of approximately 6 days with a limiting absolute magnitude of +6. Our estimation of the absolute flux density of meteoroids in the range of mass between 10 −5 kg to 10 −1 kg was found to be comparable to other results available in the literature. Conclusions . The results of this work prove the potential for space-based observations to increase the statistics of meteor observations achievable with instruments operating on the ground. The slope of the mass distribution of meteoroids sampled with Mini-EUSO suggests a mass index of either s = 2.09 ± 0.02 or s = 2.31 ± 0.03, according to two different methodologies for the computation of the pre-atmospheric mass starting from the luminosity of each event.
For life to have dramatically evolved and diversified during the so-called Cambrian explosion, there must have been significant changes in the environmental conditions of Earth. A rapid increase in ...atmospheric oxygen, which has been discussed as the key factor in the evolution of life, cannot by itself explain such an explosion, since life requires more than oxygen to flourish let alone survive. The supply of nutrients must have played a more critical role in the explosion, including an increase in phosphorus (P) and potassium (K) which are key elements for metabolisms to function. So, what happened at the onset of the Cambrian to bring about changes in environmental conditions and nutrient supply and ultimately evolution of life?
An ultimate trigger for the Cambrian explosion is proposed here. The geotherm along subduction zones of a cooling Earth finally became cool enough around 600Ma to allow slabs to be hydrated. The subduction of these hydrated slabs transferred voluminous water from the ocean to the mantle, resulting in a lowering of the sea level and an associated exceptional exposure of nutrient-enriched continental crust, along with an increase in atmospheric oxygen. This loss of water at the surface of the Earth and an associated increase in exposed landmass is referred to here as leaking Earth. Vast amounts of nutrients began to be carried through weathering, erosion, and transport of the landmass; rock fragments of the landmass would break down into ions during transport to the ocean through river, providing life forms (prokaryote) sufficient nutrients to live and evolve. Also, plume-driven dome-up beneath the continental crusts broadened the surface area providing a supply of nutrients an order magnitude greater than that produced through uplift of mountains by continental collision. Simultaneously, atmospheric oxygen began to increase rapidly due to the burial of dead organic matter by enhanced sedimentation from the emergence of a greater landmass, which ultimately inhibited oxidation of organic matter. Hence, oxygen began to accumulate in the atmosphere, which when coupled with a continuous supply of nutrients, resulted in an explosion of life, including an increase in the size. An enhanced oxygen supply in the atmosphere resulted in the formation of an ozone layer, providing life a shield from the UV radiation of the Sun; this enabled life to invade the land. In addition to a change in the supply of nutrients related to a leaking Earth, the evolution of life was accelerated through mass extinction events such as observed during Snowball Earth, possibly related to a starburst in our galaxy, as well as mutation in the genome due to radiogenic elements sourced from carbonatite magma (atomic bomb magma) in rift valley. There are two requirements to find a habitable planet: (1) the initial mass of an ocean and (2) the size of a planet. These two conditions determine the history of a planet, including planetary tectonics and the birth of life. This newfound perspective, which includes the importance of a leaking planet, provides a dawn of new planetary science and astrobiology.
Display omitted
•The Earth's fate was controlled by the initial mass of primordial ocean and its size.•Initiation of the Leaking Earth was an ultimate trigger of the Cambrian explosion.•An effective supply of nutrients began after landmass was emerged by sea level drop.•The emergence of landmass resulted in pO2 increase due to the burial of organic matter.•Super-Earth cannot be habitable due to its too big size.
EUSO-TA is a ground-based fluorescence telescope built to validate the design of ultra-high energy cosmic ray fluorescence detectors to be operated in space with the technology developed within the ...Joint Exploratory Missions for Extreme Universe Space Observatory (JEM-EUSO) program. It operates at the Telescope Array (TA) site in Utah, USA. With an external trigger provided by the Black Rock Mesa fluorescence detectors of the Telescope Array experiment, with EUSO-TA we observed air-showers from ultra-high energy cosmic rays, as well as laser events from the Central Laser Facility at the TA site and from portable lasers like the JEM-EUSO Global Light System prototype. Since the Black Rock Mesa fluorescence detectors have a ∼30 times larger field of view than EUSO-TA, they allow a primary energy reconstruction based on the observation of a large part of the shower evolution, including the shower maximum, while EUSO-TA observes only a part of it, usually far away from the maximum. To estimate the detection limits of EUSO-TA in energy and distance, a method was developed to re-scale their energy, taking into account that EUSO-TA observes only a portion of the air-showers. The method was applied on simulation sets with showers with different primaries, energy, direction, and impact point on the ground, as well as taking into account the experimental environment. EUSO-TA was simulated with an internal trigger and different elevation angles and electronics. The same method was then applied also to real measurements and compared to the simulations. In addition, the method can also be used to estimate the detection limits for experiments that are operated at high altitudes and in most cases can see the maximum of the showers. This was done for EUSO-SPB1, an instrument installed on a super-pressure balloon. Finally, the expected detection rates for EUSO-TA were also assessed using the prepared simulated event sets. The rates correspond to a few detections per recording session of 30 h of observation, depending on the background level and the configuration of the detector.
This analysis documents the process and results of reliability determination of the PhotoMultiplier Tube (PMT) components of the JEM-EUSO telescope under the different radiation sources, UV ...radiation, Total Ionizing Doses (TIDs), and Single Event Transients. In terms of UV Ionization, the transmittance of the glass of the PMTs during the 5-year duration of the mission is greater than 99.98%, thereby ensuring the desired 20% value for quantum efficiency. Of the 4932 PMTs covering the focal surface of the telescope, we estimate that of order 7 may fail due to TID and about 16 may fail due to SET. Therefore, it can be concluded that around 99% of the PMTs will complete their operation without failure, ensuring the success of the mission as far as TIDs and SETs radiation is concerned. PMTs suffer basically due to high brightness effects, reducing the transmittance of the crystal window. However, the result of this study, taking into account the values produced by the model based on the TID, as well as the darkening of the glass, show similar values in terms of degradation. Therefore, as a preliminary result, it is possible to conclude that the TID model proposed here for PMTs can be “validated”.
•Current methods and Space standards for the reliability analysis were evaluated.•New techniques to assess space radiation impact on electronic components are proposed.•Techniques suitable for reliability analysis of PMTs devoted to space applications.•Techniques developed can be used to enhance current reliability analysis standards.
Mini-EUSO is a high sensitivity imaging telescope that observes the Earth from the ISS in the ultraviolet band (2904÷430 nm), through the UV-transparent window in the Russian Zvezda module. The ...instrument, launched in 2019 as part of the ESA mission Beyond, has a field of view of 44°, a spatial resolution on the Earth surface of 6.3 km and a temporal resolution of 2.5 microseconds. The telescope detects UV emissions of cosmic, atmospheric and terrestrial origin on different time scales, from a few microseconds upwards. Mini-EUSO main detector optics is composed of two Fresnel lenses focusing light onto an array of 36 Hamamatsu multi-anode photomultiplier tubes, for a total of 2304 pixels. The telescope also contains: two ancillary cameras to complement measurements in the near infrared and visible ranges, an array of Silicon-PhotoMultipliers and UV sensors to manage night-day transitions. In this work we will describe the in-flight operations and performances of the various instruments in the first months after launch.
In the extreme high intensity regime of electromagnetic (EM) waves in plasma, the acceleration process is found to be dominated by the ponderomotive acceleration (PA). While the wakefields driven by ...the ponderomotive force of the relativistic intensity EM waves are important, they may be overtaken by the PA itself in the extreme high intensity regime when the dimensionless vector potential a_{0} of the EM waves far exceeds unity. The energy gain by this regime (in 1D) is shown to be (approximately) proportional to a_{0}^{2}. Before reaching this extreme regime, the coexistence of the PA and the wakefield acceleration is observed where the wave structures driven by the wakefields show the phenomenon of multiple and folded wave breakings. Investigated are various signatures of the acceleration processes such as the dependence on the mass ratio for the energy gain as well as the energy spectral features. The relevance to high energy cosmic ray acceleration and to the relativistic laser acceleration is considered.
PDF
