423 research outputs found
Target holder as a specific sensor for laser-induced plasma ablation
No full textWe have used grounded and isolated targets to measure currents of electrons escaping the pulsed laser-produced plasma. Presented experiments show that the laser-produced plasma is dominated by three phases such as the ignition phase, active and afterglow phases. The last two phases occurring after laser-plasma interaction are influenced by whether the target is isolated from the vacuum chamber or grounded. The voltage arising on the isolated target, which acts as a capacitor, mainly affects the active phase, where collisions of particles still form the plasma. This can cause reduction in ion emissions, as observed for heavier elements. The target charging accompanying the laser ablation was driven by nanosecond laser radiation with fluence ranging between 1–4 J/cm2
Real-Time Diagnostics of Fast Light Ion Beams Accelerated by a sub-Nanosecond Laser
No full textMulti-MeV proton and light ion beams had been produced using the 300 ps, kJ-class iodine laser, operating at Prague Asterix Laser System (PALS) Centre in Prague. The target material had been chosen in such a way so as to increase the proton beam current density (approaching 0.1 A/cm2 at the distance of 1 m from the source). The real-time ion detection was performed by means of a standard flat and ring ion collectors (IC) in the time-of-flight (TOF) configuration. The ICs had been shielded with aluminum foils of various thickness, in order to cut the long photo-peak contribution that is usually overlapping with the ultrafast particle signal, and to analyze mainly the laser-accelerated proton beam. The processing of the obtained experimental IC data is described in some detail, including the deconvolution of TOF signals, evaluation of the UV/soft-X-ray photo-peak absorption, and ion transmission calculations for different metallic filters
Pre- and post-extraction analyses of different charge state ion components produced in a laser ion source
No full textKnowledge of the relative abundance and the energy distributions of various ion species produced in laser ablation plasma is essential both in the fundamental physics ground, to understand the thermalization and expansion dynamics of the plasma plume, and in the applied physics ground, to get an efficient and versatile ion source. We present measurements and analyses related to such aspects, both for plasma in free expansion and for the extracted ion bunch. In particular, we characterized the former by means of ion current measurements, employing appropriate Faraday cups and electrostatic spectrometers; as regard as the latter, we performed time-of-flight spectrometry and depth profiling of implanted substrates. The extracted bunch signal showed modulation on time-of-flight due to the presence of multiply charged ions; depth profiling by X-ray photo-electron spectroscopy also showed a maximum penetration range and a profile modulation compatible with a multi-energetic beam. In these experiments we used UV excimer lasers, at irradiance values in the range 0.1 - 10 GW/cm2, to generate plasma from Cu and Al targets. The ion beams were extracted at voltages of tens of kV, DC
Effect of grounding and isolation of the target on the emissive properties of laser-produced plasma
No full textDuring laser ablation, ions are accelerated by electrons, some of which definitely escape from the plasma by passing through a potential barrier that is created on the outer regions of the plasma produced by the laser. The escaping electrons generate a net positive charge at the target surface. Depending on whether the target is grounded or isolated from the vacuum chamber, either this positive charge is neutralized by the current flowing from the ground or generates a voltage on the isolated target corresponding to its capacitance. Under certain experimental conditions, it can be expected that this charge can retroactively affect not only the expansion velocity of the emitted ions and their number, but also the total number of escaped electrons. In this work, we deal with ion emission and measuring the voltage arisen on an isolated target or the current of electrons flowing between the ground and a grounded target. For the first time, this made it possible to estimate the ratio of the number of electrons released from plasma to the number of electrons stopped by a potential barrier. Irradiating various targets with a 60-110 mJ energy delivered by a 23-ns KrF excimer laser, this portion is 10−3 for grounded targets and 10−5 for targets isolated from the vacuum chamber. The observation of target currents also makes it possible to identify the level of influence of the contamination of the target surface with chemisorbed hydrocarbons on plasma production and ion separation caused by their different atomic weights
Speleogeneza Divaškega krasa
No full textAuthor describes the evolution of the caves and karst surface of the Divaški kras, an area above caves Škocjanske jame and Kačna jama. This karst is with 18 km of known cave passages, accessible to the depth of 280 m, one of the most interesting karst areas in Slovenia. There are descriptions of the oldest caves that are because of the denudation of the surface in shallow depth or surface already cuts trough them. These unroofed caves, which can be found there, enable the reconstruction of the oldest phases of the karst formation. In following chapter cave system of Škocjanske jame – Kačna jama is presented. In these two caves was with the analysis of the geological structure and comparison of the for these two caves geological structures, passage morphology, and recent sediments were sediments analysed in order to get evolution of the caves. Special attention was paid to the large chambers, canyons and collapse dolines. The hydrology of the underground river Reka is described, especially the bifurcations to several separated streams. In special chapter there are results of the datations of the stalagmites and other flowstone which dates some phases in cave evolution and well reflects the past climatic changes. In well designed book with rich photographic material an extensive bibliography is added and summary in Slovene and English language.Avtor sintetično obravnava razvoj jam in površja Divaškega krasa med Škocjanskimi jamami in Kačno jamo. Ta kras je z okrog 18 km znanih jamskih rovov dostopnih do globine 280 metrov eno najbolj zanimivih kraških področij v Sloveniji in tudi v svetu. Opisane so najstarejše jame, ki leže zaradi denudacije plitvo pod površjem ali pa jih je površje že prerezalo. Te brezstrope jame s sedimenti, ki jih tam najdemo, omogočajo rekonstrukcijo najstarejših faz oblikovanja krasa. Sledi poglavje, v katerem je prikazan jamski sistem Škocjanskih jam in Kačne jame. Pri teh dveh jamah je s pomočjo analize geološke strukture in morfološke primerjave rovov ter analize recentnih sedimentov obdelana geneza jam s poudarkom na nastanku velikih dvoran, kanjonov in udornic. Opisana je hidrologija podzemne Reke ob različnih vodostajih ter njeno raztekanje na več ločenih tokov. V posebnem poglavju najdemo rezultate datacij kapnikov oziroma sige, kar omogoča datiranje nekaterih faz v razvoju jam, predvsem pa dobro odraža klimatske spremembe v preteklosti
Speleogeneza Divaškega krasa
No full textAuthor describes the evolution of the caves and karst surface of the Divaški kras, an area above caves Škocjanske jame and Kačna jama. This karst is with 18 km of known cave passages, accessible to the depth of 280 m, one of the most interesting karst areas in Slovenia. There are descriptions of the oldest caves that are because of the denudation of the surface in shallow depth or surface already cuts trough them. These unroofed caves, which can be found there, enable the reconstruction of the oldest phases of the karst formation. In following chapter cave system of Škocjanske jame – Kačna jama is presented. In these two caves was with the analysis of the geological structure and comparison of the for these two caves geological structures, passage morphology, and recent sediments were sediments analysed in order to get evolution of the caves. Special attention was paid to the large chambers, canyons and collapse dolines. The hydrology of the underground river Reka is described, especially the bifurcations to several separated streams. In special chapter there are results of the datations of the stalagmites and other flowstone which dates some phases in cave evolution and well reflects the past climatic changes. In well designed book with rich photographic material an extensive bibliography is added and summary in Slovene and English language.Avtor sintetično obravnava razvoj jam in površja Divaškega krasa med Škocjanskimi jamami in Kačno jamo. Ta kras je z okrog 18 km znanih jamskih rovov dostopnih do globine 280 metrov eno najbolj zanimivih kraških področij v Sloveniji in tudi v svetu. Opisane so najstarejše jame, ki leže zaradi denudacije plitvo pod površjem ali pa jih je površje že prerezalo. Te brezstrope jame s sedimenti, ki jih tam najdemo, omogočajo rekonstrukcijo najstarejših faz oblikovanja krasa. Sledi poglavje, v katerem je prikazan jamski sistem Škocjanskih jam in Kačne jame. Pri teh dveh jamah je s pomočjo analize geološke strukture in morfološke primerjave rovov ter analize recentnih sedimentov obdelana geneza jam s poudarkom na nastanku velikih dvoran, kanjonov in udornic. Opisana je hidrologija podzemne Reke ob različnih vodostajih ter njeno raztekanje na več ločenih tokov. V posebnem poglavju najdemo rezultate datacij kapnikov oziroma sige, kar omogoča datiranje nekaterih faz v razvoju jam, predvsem pa dobro odraža klimatske spremembe v preteklosti
Speleogeneza Divaškega krasa
No full textAuthor describes the evolution of the caves and karst surface of the Divaški kras, an area above caves Škocjanske jame and Kačna jama. This karst is with 18 km of known cave passages, accessible to the depth of 280 m, one of the most interesting karst areas in Slovenia. There are descriptions of the oldest caves that are because of the denudation of the surface in shallow depth or surface already cuts trough them. These unroofed caves, which can be found there, enable the reconstruction of the oldest phases of the karst formation. In following chapter cave system of Škocjanske jame – Kačna jama is presented. In these two caves was with the analysis of the geological structure and comparison of the for these two caves geological structures, passage morphology, and recent sediments were sediments analysed in order to get evolution of the caves. Special attention was paid to the large chambers, canyons and collapse dolines. The hydrology of the underground river Reka is described, especially the bifurcations to several separated streams. In special chapter there are results of the datations of the stalagmites and other flowstone which dates some phases in cave evolution and well reflects the past climatic changes. In well designed book with rich photographic material an extensive bibliography is added and summary in Slovene and English language.Avtor sintetično obravnava razvoj jam in površja Divaškega krasa med Škocjanskimi jamami in Kačno jamo. Ta kras je z okrog 18 km znanih jamskih rovov dostopnih do globine 280 metrov eno najbolj zanimivih kraških področij v Sloveniji in tudi v svetu. Opisane so najstarejše jame, ki leže zaradi denudacije plitvo pod površjem ali pa jih je površje že prerezalo. Te brezstrope jame s sedimenti, ki jih tam najdemo, omogočajo rekonstrukcijo najstarejših faz oblikovanja krasa. Sledi poglavje, v katerem je prikazan jamski sistem Škocjanskih jam in Kačne jame. Pri teh dveh jamah je s pomočjo analize geološke strukture in morfološke primerjave rovov ter analize recentnih sedimentov obdelana geneza jam s poudarkom na nastanku velikih dvoran, kanjonov in udornic. Opisana je hidrologija podzemne Reke ob različnih vodostajih ter njeno raztekanje na več ločenih tokov. V posebnem poglavju najdemo rezultate datacij kapnikov oziroma sige, kar omogoča datiranje nekaterih faz v razvoju jam, predvsem pa dobro odraža klimatske spremembe v preteklosti
Speleogeneza Divaškega krasa
No full textAuthor describes the evolution of the caves and karst surface of the Divaški kras, an area above caves Škocjanske jame and Kačna jama. This karst is with 18 km of known cave passages, accessible to the depth of 280 m, one of the most interesting karst areas in Slovenia. There are descriptions of the oldest caves that are because of the denudation of the surface in shallow depth or surface already cuts trough them. These unroofed caves, which can be found there, enable the reconstruction of the oldest phases of the karst formation. In following chapter cave system of Škocjanske jame – Kačna jama is presented. In these two caves was with the analysis of the geological structure and comparison of the for these two caves geological structures, passage morphology, and recent sediments were sediments analysed in order to get evolution of the caves. Special attention was paid to the large chambers, canyons and collapse dolines. The hydrology of the underground river Reka is described, especially the bifurcations to several separated streams. In special chapter there are results of the datations of the stalagmites and other flowstone which dates some phases in cave evolution and well reflects the past climatic changes. In well designed book with rich photographic material an extensive bibliography is added and summary in Slovene and English language.Avtor sintetično obravnava razvoj jam in površja Divaškega krasa med Škocjanskimi jamami in Kačno jamo. Ta kras je z okrog 18 km znanih jamskih rovov dostopnih do globine 280 metrov eno najbolj zanimivih kraških področij v Sloveniji in tudi v svetu. Opisane so najstarejše jame, ki leže zaradi denudacije plitvo pod površjem ali pa jih je površje že prerezalo. Te brezstrope jame s sedimenti, ki jih tam najdemo, omogočajo rekonstrukcijo najstarejših faz oblikovanja krasa. Sledi poglavje, v katerem je prikazan jamski sistem Škocjanskih jam in Kačne jame. Pri teh dveh jamah je s pomočjo analize geološke strukture in morfološke primerjave rovov ter analize recentnih sedimentov obdelana geneza jam s poudarkom na nastanku velikih dvoran, kanjonov in udornic. Opisana je hidrologija podzemne Reke ob različnih vodostajih ter njeno raztekanje na več ločenih tokov. V posebnem poglavju najdemo rezultate datacij kapnikov oziroma sige, kar omogoča datiranje nekaterih faz v razvoju jam, predvsem pa dobro odraža klimatske spremembe v preteklosti
Contents of the krasA object, representing the exons in isoform A of KRAS.
No full text<p>Contents of the krasA object, representing the exons in isoform A of KRAS.</p
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