Guillermo Andler

First storage of ion beams in the Double Electrostatic Ion-Ring Experiment: DESIREE

We report on the first storage of ion beams in the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. We have produced beams of atomic carbon anions and small carbon anion molecules (C(n)(-), n = 1, 2, 3, 4) in a sputter ion source. The ion beams were accelerated to 10 keV kinetic energy and stored in an electrostatic ion storage ring enclosed in a vacuum chamber at 13 K. For 10 keV C2 (-) molecular anions we measure the residual-gas limited beam storage lifetime to be 448 s ± 18 s with two independent detector systems. Using the measured storage lifetimes we estimate that the residual gas pressure is in the 10(-14) mbar range. When high current ion beams are injected, the number of stored particles does not follow a single exponential decay law as would be expected for stored particles lost solely due to electron detachment in collision with the residual-gas. Instead, we observe a faster initial decay rate, which we ascribe to the effect of the space charge of the ion beam on the storage capacity.

Development of an electro-optical device for storage of high power laser pulses

Abstract We have constructed and tested a storage ring for high power ps to ns laser pulses. The aim of the optical laser ring is to increase the efficiency of using a high power laser pulse in different applications and particularly in laser-induced recombination at CRYRING. Efforts to increase the efficiency of using high power laser pulses by using different kind of optical cavities are going on in different laboratories around the world. In our case we use a very fast electro-optical switch to inject the laser pulse into an optical ring, where the used Pockels cell is driven by a fast high voltage pulser with a rise time

Experimental dielectronic recombination rate coefficientsfor Na-like S VI and Na-like Ar VIII

Aims. Absolute recombination rate coefficients for two astrophysically relevant Na-like ions are presented. Methods. Recombination rate coefficients of S vi and Ar viii are determined from merged-beam type experiments at the CRYRING electron cooler. Calculated rate coefficients are used to account for recombination into states that are field-ionized and therefore not detected in the experiment. Results. Dielectronic recombination rate coefficients were obtained over an energy range covering Δn = 0 core excitations. For Na-like Ar a measurement was also performed over the Δn = 1 type of resonances. In the low-energy part of the Ar viii spectrum, enhancements of more than one order of magnitude are observed as compared to the calculated radiative recombination. The plasma recombination rate coefficients of the two Na-like ions are compared with calculated results from the literature. In the 10 3 −10 4 K range, large discrepancies are observed between calculated plasma rate coefficients and our data. At higher temperatures, above 10 5 K, in the case of both ions our data is 30% higher than two calculated plasma rate coefficients, other data from the literature having even lower values. Conclusions. Discrepancies below 10 4 K show that at such temperatures even state-of-the-art calculations yield plasma rate coefficients that have large uncertainties. The main reason for these uncertainties are the contributions from low-energy resonances, which are difficult to calculate accurately.

Using an OPO laser system for recombination studies in a storage ring: LIR to n=3 states of deuterium

We have investigated the use of a one-stage optical parametric oscillator (OPO) laser system for studies of laser induced radiative recombination (LIR) of stored ions. For the test case considered, LIR into n = 3 states of deuterium, we find that the energy resolution is limited by the broad linewidth of the OPO. Within this resolution, our LIR results are in good agreement with a theoretical average field induced threshold shift model.

Commissioning of the DESIREE storage rings - a new facility for cold ion-ion collisions

We report on the ongoing commissioning of the Double ElectroStatic Ion Ring ExpEriment, DESIREE, at Stockholm University. Beams of atomic carbon anions (C-) and smaller carbon anion molecules (C-2( ...

First results from the Double ElectroStatic Ion-Ring ExpEriment, DESIREE

We have stored the first beams in one of the rings of the double electrostatic ion-storage ring, DESIREE at cryogenic and at room temperature conditions. At cryogenic operations the following parameters are found. Temperature; T= 13K, pressure; p 10(7) and storage lifetime of a C-2(-) beam; tau = 450 S.

A linear optical trap with active medium for experiments with high power laser pulses

A linear optical trap for circulating high power laser pulses and tuning these pulses to high repetition frequency of several tens of MHz has been developed. A ns excimer pumped dye laser pulse has been injected with help of a Wollaston prism and a synchronized Pockels cell into an optical trap formed by two highly reflecting mirrors in a linear configuration. The test was done at λ = 580 nm, but the optical trap can be used without limitations in a broad band of optical wavelengths (400-700 nm). Power considerations give an increase of the efficiency of the optical trap of about 7 times compared to single passage of the laser pulse through the experimental section. The time structure of the trapped laser pulses can be controlled by changing the distance between the two high reflecting mirrors. The efficiency of the optical trap strongly depends upon optical losses. To compensate the optical losses, an amplifying cell was introduced, and the efficiency was about 60 times higher than that by single passage of the laser pulse through the experimental section.

A seeded dye laser cavity for intracavity experiments

A seeded dye laser cavity, synchronously pumped by the 2nd harmonic of the Nd:YAG laser has been designed and experimentally tested. The used seed signal was the well defined narrow linewidth output laser signal (▵λ = 0.013 nm) from the excimer-dye laser system. Energy considerations showed that the intracavity laser energy, that can be used for an experimental section inside the cavity, can reach an efficiency of 20% of the pumping energy. The wavelength and linewidth are fully controlled by the wavelength and linewidth of the seeding laser.

The Double ElectroStatic Ion-Ring ExpEriment, DESIREE

We describe the status of the DESIREE facility, which is an electrostatic ion-storage device consisting of two storage rings with a common section, where ion beams of opposite charges stored in the two rings are merged. The electrostatic storage rings are mounted in a single common vacuum vessel, which is isolated inside an outer vacuum chamber and cooled by means of four cryogenerators. This unique system will allow for studies of interaction among ions of opposite charges at well controlled conditions both in terms of internal degrees of freedom and relative velocity. An advanced ion-beam production system for intense pulses of cold complex molecular ions is also presented.