236 research outputs found
Moths and butterflies (Insecta: Lepidoptera) of the Russian Arctic islands in the Barents Sea
Faunistic data are scarce for the Lepidoptera from the Arctic islands of European Russia. New sampling and revision of the earlier findings have revealed the occurrence of 60 species of moths and butterflies on Kolguev, Vaygach and Dolgij Islands and on the Novaya Zemlya archipelago. The faunas of Kolguev and Dolgij Islands (19 and 18 species, respectively) include typical moths of the northern taiga (Aethes deutschiana, Syricoris lacunana and Xanthorhoe designata), and the low numbers of species discovered on these islands have resulted primarily from low collecting efforts. By contrast, the fauna of Vaygach Island (22 species) is relatively well known and includes several high Arctic species, such as Xestia aequaeva, X. liquidaria and X. lyngei. Nevertheless, Vaygach Island is depauperated even relative to the fauna of Amderma (29 species), which is located on the continent next to the Vaygach Island. The fauna of Novaya Zemlya totals 30 species, but only eight of these were collected from the Northern Island, mostly near Matochkin Shar strait. Noteworthy is the record of Plutella polaris from Novaya Zemlya: this species was recently re-discovered in Svalbard, where the type series was collected in 1873. Udea itysalis, described from North America, is reported here for the first time from Europe. The fauna of the Russian Arctic islands in the Barents Sea is dominated by holarctic species, many of which are confined to tundra habitats. We estimate that some 40â60 moth species remain to be found in this region.</p
Investigating the prehistory of Tungusic peoples of Siberia and the Amur-Ussuri region with complete mtDNA genome sequences and Y-chromosomal markers
Speciation of heptavalent technetium in sulfuric acid: structural and spectroscopic studies
Experimental study of extended timescale dynamics of a plasma wakefield driven by a self-modulated proton bunch
Plasma wakefield dynamics over timescales up to 800 ps, approximately 100 plasma periods, are studied
experimentally at the Advanced Wakefield Experiment (AWAKE). The development of the longitudinal
wakefield amplitude driven by a self-modulated proton bunch is measured using the external injection of
witness electrons that sample the fields. In simulation, resonant excitation of the wakefield causes plasma
electron trajectory crossing, resulting in the development of a potential outside the plasma boundary as
electrons are transversely ejected. Trends consistent with the presence of this potential are experimentally
measured and their dependence on wakefield amplitude are studied via seed laser timing scans and electron
injection delay scan
Experimental Observation of Proton Bunch Modulation in a Plasma at Varying Plasma Densities
We give direct experimental evidence for the observation of the full transverse self-modulation of a long, relativistic proton bunch propagating through a dense plasma. The bunch exits the plasma with a periodic density modulation resulting from radial wakefield effects. We show that the modulation is seeded by a relativistic ionization front created using an intense laser pulse copropagating with the proton bunch. The modulation extends over the length of the proton bunch following the seed point. By varying the plasma density over one order of magnitude, we show that the modulation frequency scales with the expected dependence on the plasma density, i.e., it is equal to the plasma frequency, as expected from theory
AWAKE, the advanced proton driven plasma wakefield acceleration experiment at CERN
The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) aims at studying plasma wakefield generation and electron acceleration driven by proton bunches. It is a proof-of-principle R&D experiment at CERN and the worldŚłs first proton driven plasma wakefield acceleration experiment. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV/c proton beam bunches from the SPS. The first experiments will focus on the self-modulation instability of the long (rms ~12 cm) proton bunch in the plasma. These experiments are planned for the end of 2016. Later, in 2017/2018, low energy (~15 MeV) electrons will be externally injected into the sample wakefields and be accelerated beyond 1 GeV. The main goals of the experiment will be summarized. A summary of the AWAKE design and construction status will be presented
Path to AWAKE : evolution of the concept
This paper describes the conceptual steps in reaching the design of the AWAKE experiment currently under construction at CERN. We start with an introduction to plasma wakefield acceleration and the motivation for using proton drivers. We then describe the self-modulation instability - a key to an early realization of the concept. This is then followed by the historical development of the experimental design, where the critical issues that arose and their solutions are described. We conclude with the design of the experiment as it is being realized at CERN and some words on the future outlook. A summary of the AWAKE design and construction status as presented in this conference is given in Gschwendtner et al. [1]
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