Search results for "ion source"
showing 10 items of 337 documents
Extended GT-STAF information indices based on Markov approximation models
2013
Abstract A series of novel information theory-based molecular parameters derived from the insight of a molecular structure as a chemical communication system were recently presented and usefully employed in QSAR/QSPRs (J. Comp. Chem, 2013, 34, 259; SAR and QSAR in Environ. Res. 2013, 24). This approach permitted the application of Shannon’s source and channel coding entropic measures to a chemical information source comprised of molecular ‘fragments’, using the zero-order Markov approximation model (atom-based approach). This report covers the theoretical aspects of the extensions of this approach to higher-order models, introducing the first, second and generalized-order Markov approximati…
Study of the long-period changes in samples of isotactic poly(propylene) obtained by quenching from the melt and subsequent annealing at different te…
1997
The structural modifications induced in samples of isotactic poly(propylene) obtained by quenching from the melt at 100°C/s and subsequently annealed at 40, 60 and 80°C for different annealing times have been studied using simultaneous wide-angle and small-angle X-ray scattering at the synchrotron radiation source of DESY. The occurrance of two different long-period values is demonstrated. These values are related to the mesomorphic phase, existing in the starting quenched material, and to the α-monoclinic one, which settles during the annealing process, respectively.
Development of accelerator mass spectrometry assisted by isotope-selective laser photodetachment for monitoring 129I
2013
Abstract A prototype system was developed to investigate an isotope-selective laser photodetachment technique for a 129 I accelerator mass spectrometer. A pulsed ion source for negative iodine ions (I − ) that employed laser ablation proved to be suitable for isotope-selective laser photodetachment. Laser photodetachment of pulsed negative iodine ions was estimated to have an efficiency of about 81% based on a model calculation for the prototype system with a tunable pulsed Ti:sapphire laser.
Optimizing charge breeding techniques for ISOL facilities in Europe: conclusions from the EMILIE project
2015
ThuM07; International audience; The present paper summarizes the results obtained from the past few years in the framework ofthe Enhanced Multi-Ionization of short-Lived Isotopes for Eurisol (EMILIE) project. The EMILIEproject aims at improving the charge breeding techniques with both Electron Cyclotron ResonanceIon Sources (ECRIS) and Electron Beam Ion Sources (EBISs) for European Radioactive Ion Beam(RIB) facilities. Within EMILIE, an original technique for debunching the beam from EBIS chargebreeders is being developed, for making an optimal use of the capabilities of CW post-acceleratorsof the future facilities. Such a debunching technique should eventually resolve duty cycle andtime st…
A complementary laser system for ISOLDE RILIS
2011
The Resonance Ionization Laser Ion Source (RILIS) is a powerful tool for efficient and selective production of radioactive ion beams at Isotope Separator On Line (ISOL) facilities. To avoid isobaric background, highly selective stepwise resonant ionization is applied, using up to three different laser wavelengths. Due to their advantages in terms of stability and reliability, an all solid-state titanium:sapphire (Ti:Sa) system is used or is planned to be installed at the majority of on-line facilities worldwide. Such an all solid-state Ti:Sa laser system is going to be installed at the ISOLDE RILIS at CERN alongside the well-established dye laser system.
Progress in ISOL target–ion source systems
2008
The heart of every ISOL (isotope separation on-line) facility is its target and ion source system. Its efficiency, selectivity and rapidity is decisive for the production of intense and pure ion beams of short-lived isotopes. Recent progress in ISOL target and ion source technology is discussed at the examples of radioactive ion beams of exotic zinc and tin isotopes that were purified by isothermal chromatography and molecular sideband separation respectively. An outlook is given to which other elements these purification methods are applicable.
A new off-line ion source facility at IGISOL
2019
An off-line ion source station has been commissioned at the IGISOL (Ion Guide Isotope Separator On-Line) facility. It offers the infrastructure needed to produce stable ion beams from three off-line ion sources in parallel with the radioactive ion beams produced from the IGISOL target chamber. This has resulted in improved feasibility for new experiments by offering reference ions for Penning-trap mass measurements, laser spectroscopy and atom trap experiments.
PRIN Project 2010-11 “Active and recent geodynamics of Calabrian Arc and accretionary complex in the Ionian Sea”: new constraints from geological, ge…
2014
This contribution illustrates the preliminary results of our Research Unit in the PRIN Project 2010-11, which focuses on active and recent geodynamics of Calabrian Arc. The integration of the new geological, geodetic and seismological data supports the inferred recent plate boundary reorganization in the central-southern Mediterranean, where the regional GNNS velocity fields point to a deceleration or cessation of Calabrian Arc migration, and to extension along the axis of the Calabrian Arc, accommodated by normal faulting (e.g. Capo Vaticano and Messina Straits (Aloisi et al., 2012; Pepe et al., 2014; Spampinato et al., 2014). The study of the lateral borders of the Arc revealed that obliq…
Does More Context Help? Effects of Context Window and Application Source on Retrieval Performance
2021
We study the effect of contextual information obtained from a user’s digital trace on Web search performance. Contextual information is modeled using Dirichlet–Hawkes processes (DHP) and used in augmenting Web search queries. The context is captured by monitoring all naturally occurring user behavior using continuous 24/7 recordings of the screen and associating the context with the queries issued by the users. We report a field study in which 13 participants installed a screen recording and digital activity monitoring system on their laptops for 14 days, resulting in data on all Web search queries and the associated context data. A query augmentation (QAug) model was built to expand the or…
No place for negative emotions? The effects of message valence, communication channel, and social distance on users’ willingness to respond to SNS st…
2017
Abstract The present study contributes to the investigation of communicative norms and social support in Social Network Sites (SNSs). We suggest that a positivity bias restricts the availability of social support users receive from others via public responses to negative status updates. Moderated mediation analyses of the data of an online experiment ( N = 870, M age = 25.16 years, 64% female) show that users are less willing to comment on negative status updates than on positive ones. In contrast, users are more willing to respond to negative status updates with private messages. These effects are moderated by the strength of the relationship between sender and receiver of the status upd…