Search results for "buffer"
showing 10 items of 230 documents
A compact apparatus for mass selective resonance ionization spectroscopy in a buffer gas cell
1997
Abstract An ultra-sensitive laser spectroscopic method for the investigation of transuranium nuclides has been developed based on resonance ionization in an argon buffer gas cell. This method has been combined with ion-guide extraction and mass selective direct detection of the resonantly ionized atoms. Using argon as a buffer gas, recoils of fusion reactions can be thermalized even at low pressure. The differential pumping system consists of only one roots pump and two turbo molecular pumps. The set-up has been tested with 243 Am evaporated from a filament located inside the optical gas cell. Resonance ionization is performed using a two-step excitation with an excimer-dye-laser combinatio…
A study of on-line gas cell processes at IGISOL
2010
Abstract The laser ion source at the IGISOL facility, Jyvaskyla, has been used to study the effects of the passage of a primary beam through an ion guide via the dynamic time profiles of yttrium and related molecular compounds. The accessibility of a neutral fraction for laser ionization is shown to be restricted to the nozzle region in the presence of a weak plasma. The survival of this neutral fraction cannot be explained by recombination of the buffer gas alone and perhaps indicates a suppression of the transport of ions due to a plasma-generated electric field. The concept of a competition between the processes that create and destroy the ion of interest is used to explain the different…
First Determination of the Ionization Potential of Actinium and First Observation of Optical Transitions in Ferminm
2002
For the determination of the first ionization potential of actinium, 227Ac was electrodeposited on a Ta backing and covered with ~1 μm Zr. From this filament, Ac atoms were evaporated at ≥ 1250 °C. By resonant excitation with UV light of 388.67 nm and subsequent excitation with light of ca. 568 nm, Ac was ionized in an external electrical field. By determining the ionization thresholds as a function of the electrical field strength and by extrapolation to zero field strength, the first ionization potential of 43398(3) cm−1 = 5.3807(3) eV was measured.About 1 ng of 255Fm, half life 20.1 h, was prepared at ORNL by milking from 255Es produced in the High Flux Isotope Reactor and shipped to Mai…
Rapid extraction of short-lived isotopes from a buffer gas cell for use in gas-phase chemistry experiments. Part I: Off-line studies with 219Rn and …
2021
Abstract To study the chemical properties of the heaviest elements, a fast and efficient stopping and extraction of the highly energetic residues from heavy ion fusion reactions into the chemistry setup is essential. Currently used techniques like Recoil Transfer Chambers (RTC) relying on gas flow extraction provide high efficiencies for chemically non-reactive volatile species, but operate at extraction times t extr of about 0.5 s or more. Buffer Gas Cells (BGC) with electric and Radio-Frequency (RF) fields offer much faster extraction times. Here, we demonstrate the successful coupling of a BGC to a gas chromatography setup as is used for studies of chemical properties of superheavy eleme…
Rate capability of a cryogenic stopping cell for uranium projectile fragments produced at 1000 MeV/u
2016
At the Low-Energy Branch (LEB) of the Super-FRS at FAIR, projectile and fission fragments will be produced at relativistic energies, separated in-flight, energy-bunched, slowed down and thermalized in a cryogenic stopping cell (CSC) filled with ultra-pure He gas. The fragments are extracted from the stopping cell using a combination of DC and RF electric fields and gas flow. A prototype CSC for the LEB has been developed and successfully commissioned at the FRS Ion Catcher at GSI. Ionization of He buffer gas atoms during the stopping of energetic ions creates a region of high space charge in the stopping cell. The space charge decreases the extraction efficiency of stopping cells since the …
New concepts for the ion guide technique
2008
The technique of using noble gases to cool energetic beams offers fast extraction times, very little sensitivity to chemical properties of the ions and very low-energy spreads. A variant of this method is based on the selective laser ionization of radioactive species after they have been thermalized in gas as neutral atoms. The laser ion source in Jyvaskyla is used to highlight the importance of buffer gas purity using yttrium, a particularly chemically reactive element. The time distribution profiles obtained on-line illustrate the competing factors that create and destroy the ion of interest during evacuation from the ion guide. A review of the extraction efficiencies of gas catchers of d…
The MARA-LEB ion transport system
2020
Abstract A low-energy branch is under development for the MARA vacuum-mode recoil separator at the Accelerator Laboratory of the University of Jyvaskyla. This development will allow for the study of proton-rich nuclei through laser ionisation spectroscopy and mass measurements. After stopping and extraction from a buffer gas cell, the ions of interest will be accelerated and transported to dedicated experimental setups by an ion transport system consisting of several focusing, accelerating and mass-separating elements. This article presents the current design and simulations for the ion transport.
A CEMS-study of the passive layer on iron and steel
1988
From AES, ICEMS, and DCEMS experiments it was concluded that the passive layer formed on steel in a phosphate buffer consists of γ-FeOOH. Its thickness increases from 0.5 to 3.5 nm throughout the passive region. It is covered by noncorrelated layers of a precipitate and an adsorbate.
Crystallization of late-stage MORB under varying water activities and redox conditions: Implications for the formation of highly evolved lavas and ox…
2018
Abstract In order to understand late magmatic processes that occur in the deep oceanic crust, we performed a phase-equilibria study in a representative late-stage system at a pressure of 200 MPa with a special focus on the role of water and oxygen fugacity. The starting composition for the experiments was evaluated based on a statistical approach using evolved fresh MORB glasses from the database PETDB highest in FeO and TiO2 (in average 17.92 wt% and 3.73 wt%, respectively), assumed to represent frozen liquids erupted at the seafloor generated by extensive differentiation of MORB. We conducted crystallization experiments in a range of temperatures from 850 to 1050 °C with water activities …
Optic fibre as a transducer of tendomuscular forces
1996
Direct in vivo tendon force measurements open up new possibilities for understanding of muscle-tendon loads during natural locomotion. The present report presents a new optic fibre method for such applications. The method is based on light intensity modulation by mechanical modification of the geometric properties of the optic fibre. A special optic fibre with a plastic covering buffer and with a total diameter of either 265 microns or 500 microns was carefully prepared at both ends for receiving and transmitting light. The fibre was inserted through the rabbit common calcaneal tendon with a 20 gauge needle. By removing the needle the optic fibre remained in situ. Static loading demonstrate…