scholarly journals “Chaotic” dart leaders in triggered lightning: Electric fields, X-rays, and source locations

2012 ◽  
Vol 117 (D3) ◽  
pp. n/a-n/a ◽  
Author(s):  
Jonathan D. Hill ◽  
Martin A. Uman ◽  
Douglas M. Jordan ◽  
Joseph R. Dwyer ◽  
Hamid Rassoul
Keyword(s):  
Electric Fields ◽  
X Rays ◽  
Triggered Lightning

Cytochemische Untersuchungen zur Reproduktion des Tabakmosaikvirus

1961 ◽  
Vol 16 (8) ◽  
pp. 520-538 ◽  
Author(s):  
Hendrik Zech
Keyword(s):  
Electric Fields ◽  
Uv Light ◽  
Refraction Index ◽  
Optical Measurements ◽  
Uv Spectrophotometry ◽  
X Rays ◽  
Optical Absorbance ◽  
Wide Range ◽  
Light Losses

Crystalline or paracrystalline tobacco mosaic virus (TMV) inclusions are known to be composed mainly of densely packed TMV-rods. These inclusions were studied in situ within infected tobacco leaf hair cells by scanning UV-microspectrophotometry. Comparative measurements in the macroand micro ranges of the instruments were carried out on purified TMV at low and high concentrations, on its separated and reconstituted RNA and protein parts and on isolated TMV-crystals, to permit the interpretation of the optical properties of TMV inclusions in situ. The optical absorbance of TMV in solution and in dried concentrates at room temperature could in part be attributed to distribution inhomogeneities caused by local particle aggregations being oriented to differing degrees. The resulting non-uniform electric fields around and within such unevenly distributed particle complexes caused local jumps of the refraction index and thereby unspecific light losses, chiefly through scattering. The apparent deviation from Beers law was found to be greatest at particle concentrations of 1 - 2 per cent. At higher concentrations the contribution of scatter to light losses was found to decrease again, probably because of increasing order of particles within the aggregates. On the other hand the specific absorbance of the chromophores of TMV over a wide range of concentration was not affected to a measurable degree by changing the distances between the rods. There was no indication that the charged groups of the RNA-cores within intact particles interacted with charged groups of other particles however great their proximity. The ribose phosphate backbone of the RNA strand, deeply embedded within the protein helix, may account for this phenomenon. However, isolated TMV-RNA reacted strongly to changes of the surrounding electric fields when concentrations were varied, and showed pronounced hypochromicity at higher concentrations and following prolonged irridation by x-rays and UV-light. RNA in dried and irradiated droplets was characterized by up to 55% lower extinction coefficients than freshly prepared RNA in solution. The hyprochromic effects caused by irradiation were shown to be almost, but not completely reversible. Hypochromicity increased towards the shorter wavelengths, diminishing the ratio E260/E280 from about 2.0 for diluted RNA to 1.4 for concentrated specimens. Mixing TMV-protein subunits with RNA before drying, leading to partial reconstitution of TMV particles, diminished the hypochromic effect resulting from irradiation of the concentrate. High UV-radiation doses applied to concentrated TMV solutions led to a marked splitting of RNA from protein, as revealed by UV-spectrophotometry of the supernatants and pellets of centrifuged irradiated specimens. Model measurements of intracellular and subsequently isolated TMV crystals combined with empirically derived parameters led to the construction of a correction curve, permitting interpretations of optical measurements on in situ TMV inclusion bodies.

scholarly journals Complex Attosecond Waveform Synthesis at FEL FERMI

2021 ◽  
Vol 11 (21) ◽  
pp. 9791
Author(s):  
Praveen Kumar Maroju ◽  
Cesare Grazioli ◽  
Michele Di Di Fraia ◽  
Matteo Moioli ◽  
Dominik Ertel ◽  
...  
Keyword(s):  
Electric Fields ◽  
Extreme Ultraviolet ◽  
X Rays ◽  
Free Electron Lasers ◽  
Short Wavelength Range ◽  
Pulse Trains ◽  
Multiple Phase ◽  
Waveform Shaping ◽  
Waveform Synthesis ◽  
Seeded Fel

Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this article, we present the generation of attosecond pulse trains (APTs) at the seeded FEL FERMI using the beating of multiple phase-locked harmonics. We demonstrate the complex attosecond waveform shaping of the generated APTs, exploiting the ability to manipulate independently the amplitudes and the phases of the harmonics. The described generalized attosecond waveform synthesis technique with an arbitrary number of phase-locked harmonics will allow the generation of sub-100 as pulses with programmable electric fields.

scholarly journals Ionization Waves Enhance the Production of X-rays during Streamer Collisions

Atmosphere ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1101
Author(s):  
Vernon Cooray ◽  
Gerald Cooray ◽  
Marcos Rubinstein ◽  
Farhad Rachidi
Keyword(s):  
Experimental Data ◽  
Electric Field ◽  
Electric Fields ◽  
Time Synchronization ◽  
Field Enhancement ◽  
Opposite Polarity ◽  
X Rays ◽  
Weakly Conducting ◽  
Ionization Waves ◽  
Discharge Gap

Experimental data show that in laboratory sparks, X-rays are produced in time synchronization with the meeting of streamers of opposite polarity just before the final breakdown of the discharge gap. It has been suggested that the electric field enhancement created during the collision of streamers could provide the necessary conditions for electron acceleration, even though some of the theoretical studies show that the duration of the electric field is not long enough to do so. The experimental data on laboratory discharges show that. when streamers of opposite polarity meet each other, a potential or ionization wave that renders the streamer channels conducting is initiated. This paper shows that these ionization waves that convert the discharge channels from weakly conducting to highly conducting are associated with electric fields large enough to accelerate electrons to relativistic energies.

scholarly journals X-Ray Analysis for Electron Beam Enhancement in the Plasma Focus Device*

1974 ◽  
Vol 18 ◽  
pp. 184-196 ◽  
Author(s):  
R. L. Gullickson ◽  
R. H. Barlett
Keyword(s):  
Electric Fields ◽  
Plasma Focus ◽  
Average Energy ◽  
High Energy ◽  
Plasma Focus Device ◽  
X Rays ◽  
Stored Energy ◽  
Power Law Distribution ◽  
X Ray ◽  
Thermoluminescent Dosimeters

AbstractThe plasma focus device, a form of linear pinch discharge, produces an intense x-ray and neutron (D2) burst from a magnetically heated dense plasma. Rapidly changing magnetic fields at pinch time generate large axial electric fields which accelerate electrons and ions. In the experiments reported here the x-ray production during the plasma pinch of a 96 kilojoule (at 20 kV) plasma focus device was measured.The purpose of these experiments was to evaluate the energy in accelerated electrons in the plasma focus device and to learn how to enhance these electron hursts. Well focused, megampere electron beams at a few hundred kilovolts, lasting less than 10 nanoseconds have applications in fusionable pellet heating experiments. (1) X-rays were monitored to evaluate these electron bursts using a defocusing bent crystal spectrometer, doubly diffused silicon (PIN) detectors, with Ross filters, thermoluminescent dosimeters (TLDs) with filters, and x-ray pinhole photography.Thermoluminescent dosimeters indicated maximum x-ray yields of 140 joules above 3 keV at 57.3 kilojoules stored energy (16 kV) for a conversion efficiency to x-rays of 0.2%. 40 joules are above 60 keV and 15 joules above 80 keV. The hard x-ray pulse typically rises in 3 ns and frequently has a pulse width less than 10 ns. The low energy x-ray spectrum consists almost entirely of lines from the high Z anode insert, and the high energy spectrum is characteristic of a nonthermal power law distribution with an exponent of 2.2 ± 0.8. Peak hard x-ray production is obtained at 1 torr deuterium in contrast to peak neutron production (3 x 1010) at 5 torr. The addition of argon reduces total x-ray yield and increases the relative fraction of soft x-rays.These measurements suggest that the plasma focus produces 1200 joules of electrons with an average energy of 150 keV, in 10 nanoseconds with a stored energy of 57.3 kilojoules. This is a power of 1.2 × 1011 watts and power density of 1.5 × 1013 watts cm−2.

scholarly journals Broad-band electric field measurements above thunderstorms by the IME-HF instrument prepared for the TARANIS mission

2020 ◽  
Author(s):  
Ondřej Santolík ◽  
Ivana Kolmašová ◽  
Radek Lán ◽  
Luděk Uhlíř ◽  
Jean-Louis Rauch ◽  
...  
Keyword(s):  
Electric Fields ◽  
Gamma Ray ◽  
Broad Band ◽  
Field Measurements ◽  
Detection Algorithm ◽  
X Rays ◽  
Scientific Instruments ◽  
Frequency Range ◽  
Low Frequencies ◽  
Blue Jets

<p>A broad-band analyzer of the IME-HF instrument (“Instrument de Mesure du champ Electrique Haute Frequence”) is prepared for the TARANIS (Tool for Analysis of RAdiation from lightNIng and Sprites) micro-satellite of the French space agency CNES. The spacecraft is based on the MYRIADE series platform. It will be launched on a Sun synchronous polar orbit at 700 km altitude. TARANIS will carry a complex payload of six scientific instruments to study radiation from lightning and optical phenomena (Transient Luminous Events) observed at altitudes between 20 and 100 km (blue jets, red sprites, halos, elves). The scientific instruments onboard TARANIS will detect electromagnetic radiation from very low frequencies up to 37 MHz, optical radiation, X rays (with an aim to study the Terrestrial "Gamma-ray" Flashes), and energetic electrons.</p><p>The IME-HF instrument will record waveform measurements of fluctuating electric fields in the frequency range from a few kHz up to 37 MHz, with the following scientific aims: (i) Identification of possible wave signatures associated with transient luminous phenomena during storms; (ii)    Characterization of lightning flashes from their HF electromagnetic signatures; (iii) Identification of possible HF electromagnetic or/and electrostatic signatures of precipitated and accelerated particles; (iv) Determination of characteristic frequencies of the medium using natural waves properties; (v) Global mapping of the natural and artificial waves in the HF frequency range, with an emphasis on the transient events. The instrument will be also able to trigger and record interesting intervals of data using a flexible event detection algorithm.</p>

scholarly journals Imaging local electric fields produced upon synchrotron X-ray exposure

2014 ◽  
Vol 112 (3) ◽  
pp. 696-701 ◽  
Author(s):  
Christopher M. Dettmar ◽  
Justin A. Newman ◽  
Scott J. Toth ◽  
Michael Becker ◽  
Robert F. Fischetti ◽  
...  
Keyword(s):  
Electric Fields ◽  
Second Harmonic ◽  
Soft Materials ◽  
Local Fields ◽  
X Rays ◽  
Electron Hole ◽  
X Ray ◽  
X Ray Absorption ◽  
Static Electric Fields ◽  
Cryogenic Conditions

Electron–hole separation following hard X-ray absorption during diffraction analysis of soft materials under cryogenic conditions produces substantial local electric fields visualizable by second harmonic generation (SHG) microscopy. Monte Carlo simulations of X-ray photoelectron trajectories suggest the formation of substantial local electric fields in the regions adjacent to those exposed to X-rays, indicating a possible electric-field–induced SHG (EFISH) mechanism for generating the observed signal. In studies of amorphous vitreous solvents, analysis of the SHG spatial profiles following X-ray microbeam exposure was consistent with an EFISH mechanism. Within protein crystals, exposure to 12-keV (1.033-Å) X-rays resulted in increased SHG in the region extending ∼3 μm beyond the borders of the X-ray beam. Moderate X-ray exposures typical of those used for crystal centering by raster scanning through an X-ray beam were sufficient to produce static electric fields easily detectable by SHG. The X-ray–induced SHG activity was observed with no measurable loss for longer than 2 wk while maintained under cryogenic conditions, but disappeared if annealed to room temperature for a few seconds. These results provide direct experimental observables capable of validating simulations of X-ray–induced damage within soft materials. In addition, X-ray–induced local fields may potentially impact diffraction resolution through localized piezoelectric distortions of the lattice.

Triggered-lightning properties inferred from measured currents and very close electric fields

2005 ◽  
Vol 76 (1-4) ◽  
pp. 355-376 ◽  
Author(s):  
V. Kodali ◽  
V.A. Rakov ◽  
M.A. Uman ◽  
K.J. Rambo ◽  
G.H. Schnetzer ◽  
...  
Keyword(s):  
Electric Fields ◽  
Triggered Lightning
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