Two types of optical smoothly irregular waveguide structures promising for application in optical information systems are studied by numerical simulation and experimentally: the thin film generalised waveguide Luneburg lens and the liquid thin waveguide lens. The importance of the statistical analysis of functioning of optical components in information optical systems is emphasised.

Here we will briefly describe the commissioning of the Double ElectroStatic Ion Ring ExpEriment (DESIREE) facility at Stockholm University, Sweden. This device uses purely electrostatic focussing and deflection elements and allows ion beams of opposite charge to be confined under extreme high vacuum and cryogenic conditions in separate "rings" and then merged over a common straight section. This apparatus allows for studies of interactions between cations and anions at very low and well-defined centre-of-mass energies (down to a few meV) and at very low internal temperatures (down to a few K).

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(-), C-3(-), C-4(-) etc.) have been produced in a sputter ion source, accelerated to 10 keV or 20 keV, and stored successfully in the two electrostatic rings. The rings are enclosed in a common vacuum chamber cooled to below 13 Kelvin. The DESIREE facility allows for studies of internally relaxed single isolated atomic, molecular and cluster ions and for collision experiments between cat-and anions down to very low center-of-mass collision energies (meV scale). The total thermal load of the vacuum chamber at this temperature is measured to be 32 W. The decay rates of stored ion beams have two components: a non-exponential component caused by the space charge of the beam itself which dominates at early times and an exponential term from the neutralization of the beam in collisions with residual gas at later times. The residual gas limited storage lifetime of carbon anions in the symmetric ring is over seven minutes while the 1/e lifetime in the asymmetric ring is measured to be about 30 seconds. Although we aim to improve the storage in the second ring, the number of stored ions are now sufficient for many merged beams experiments with positive and negative ions requiring milliseconds to seconds ion storage.

In this proceedings I will describe the design of a new storage device currently under construction at Stockholm University, Sweden. This device uses purely electrostatic focussing and deflection elements and allows ion beams of opposite charge to be confined under extreme high vacuum and cryogenic conditions in separate "rings" and then merged over a common straight section. This Double ElectroStatic Ion Ring ExpEriment (DESIREE) apparatus allows for studies of interactions between cations and anions at low and well-defined centre-of-mass energies. I discuss the design of the DESIREE facility, highlighting some of the technical advantages of using purely electrostatic over magnetic elements, as well as the issues that have arisen during its development and construction. Finally, the advantages of this design are a boon to fundamental experimental studies and I finish by discussing an example of such potential research.

The polarization dependence of laser-induced radiative recombination (LIR) to D+ ions was investigated in the electron cooler of the CRYRING storage ring. The LIR gain as a function of wavelength into n = 3 principal quantum states of deuterium was measured at laser beam polarization angles of 0 degrees and 90 degrees with respect to the direction of the motional electric field in the interaction region. For the case of the polarization vector parallel to the external field, there is a double-peak structure in the gain curve that indicates a polarization effect in the LIR process. The two polarization directions also reveal a different width for the respective gain curves, giving additional evidence for the polarization effect, clearly seen by the behavior of a defined polarization parameter. The obtained polarization effect indicates a high sensitivity in recombination processes to external fields.

We describe the design of a novel type of storage device currently under construction at Stockholm University, Sweden, using purely electrostatic focussing and deflection elements, in which ion beams of opposite charges are confined under extreme high vacuum cryogenic conditions in separate "rings" and merged over a common straight section. The construction of this double electrostatic ion ring experiment uniquely allows for studies of interactions between cations and anions at low and well-defined internal temperatures and centre-of-mass collision energies down to about 10 K and 10 meV, respectively. Position sensitive multi-hit detector systems have been extensively tested and proven to work in cryogenic environments and these will be used to measure correlations between reaction products in, for example, electron-transfer processes. The technical advantages of using purely electrostatic ion storage devices over magnetic ones are many, but the most relevant are: electrostatic elements which are more compact and easier to construct; remanent fields, hysteresis, and eddy-currents, which are of concern in magnetic devices, are no longer relevant; and electrical fields required to control the orbit of the ions are not only much easier to create and control than the corresponding magnetic fields, they also set no upper mass limit on the ions that can be stored. These technical differences are a boon to new areas of fundamental experimental research, not only in atomic and molecular physics but also in the boundaries of these fields with chemistry and biology. For examples, studies of interactions with internally cold molecular ions will be particular useful for applications in astrophysics, while studies of solvated ionic clusters will be of relevance to aeronomy and biology.

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 Delta n = 0 core excitations. For Na-like Ar a measurement was also performed over the Delta n = 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 105 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 104 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.

DESIREE is a double electrostatic storage ring being built by the Manne Siegbahn Laboratory and the Physics Department of Stockholm University., and a common straight section along which stored ions can interact. The ion optics for both rings will be housed in a single, double walled vacuum chamber built like a cryostat with a radiation screen and several layers of super insulation in between the two chambers. The bottom of the inner chamber, which holds all the optical elements, will be cooled to around 10 K by four cryogenerators. It is constructed in low-alloy aluminium to ensure a good thermal conductivity over the whole structure. This low temperature in combination with the unique double ring structure will result in a powerful machine for studying interactions between cold molecular ions close to zero relative energy. For the outer vacuum chamber construction steel is used which will provide screening of magnetic fields on the outside. Two injectors will be able to supply both positive and negative ions to both rings.

The paper describes a novel application of an electron beam ion trap as a plasma target facility for intense laser-plasma interaction studies. The low density plasma target (similar to 10(13)/cm(3)) is confined in a mobile cryogenic electromagnetic charged particle trap, with the magnetic confinement field of 1-3 T maintained by a superconducting magnet. Ion plasmas for a large variety of ion species and charge states are produced and maintained within the magnetic field and the space-charge of an energetic electron beam in the "electron beam ion trap" (EBIT) geometry. Intense laser beams (optical lasers, X-ray lasers and upcoming "X-ray free electron lasers" (XFEL)) provide strong time varying electromagnetic fields (> 10(12) V/cm in femto- to nano-second pulses) for interactions with electromagnetically confined neutral/non-neutral plasmas. Experimental scenarios with intense photon fields on ionization/excitation processes, the ionization balance, as well as photon polarization effects and tests with intense lasers that utilize the ion plasma target are outlined. A first test of the plasma target with the PHELIX high intensity laser at GSI is described. (c) 2007 Elsevier B.V. All rights reserved.

A double electrostatic storage ring named DESIREE is under construction at the Manne Siegbahn Laboratory and Stockholm University. The two rings will have the same circumference, 9.2 m, and a common straight section for merged beam experiments with ions of opposite charges. The whole structure will be contained in a single vacuum vessel resulting in a very compact design. In addition to its unique double ring structure it will be possible to cool DESIREE below 20 K using cryogenerators. This will reduce the internal vibrational and rotational excitations of stored molecules. A cold system will also result in excellent vacuum conditions where longer lifetimes of the stored beams can be expected. While the ion optical calculations have entered a final phase much of the work is now devoted to solve many of the mechanical and cryogenic challenges of DESIREE. In order to test the mechanical and cryogenic properties of insulators, vacuum seals, and laser viewports a small test system has been built. The test system will provide valuable information for the final design of DESIREE.

DESIREE is a double electrostatic storage ring cooled to cryogenic temperatures. It is built at the Manne Siegbahn Laboratory for merged‐beam and single‐beam experiments in atomic and molecular physics as well as biophysics. This paper describes the present status of the design of DESIREE.

An optical trap for storage of high power laser pulses and tuning of these pulses to a high repetition frequency of several tens of MHz has been developed at our laboratory. 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 high reflecting mirrors in a linear configuration. The efficiency of the optical trap strongly depends upon optical losses. Power consideration gives an increasing of the efficiency of the optical trap of about 7 times compared to a single passage of the laser pulse through the experimental section. A controlled time structure of the trapped laser pulses is shown. To compensate optical losses an amplifying cell was introduced, that increased the efficiency by a factor of 25, where back and forward train of laser pulses is taken into account.

DESIREE is a double electrostatic storage ring being built at the Manne Siegbahn Laboratory and Stockholm University. It will consist of two 9.2-m-circumference rings with one common straight section, and the rings will be built in a single large vacuum vessel that can be cooled to cryogenic temperatures. The project was funded through grants in 2003 and 2004, and commissioning is foreseen for 2007. DESIREE will be used for experiments in atomic, molecular and optical physics as well as biophysics and biochemistry.

In an optical storage ring, a dye laser amplifier synchronously pumped by external laser pulses has been implemented and experimentally tested. The test was done at λ=580 nm, but the optical system can be used without limitations in a broad band of 400–700 nm. It is shown that a selected turn of the stored laser pulse can be amplified by typically a factor of 200. Power consideration gives an increase of the efficiency of the optical storage ring with a dye amplifying cell, as compared to a single passage of the laser pulse through the experimental section, by 23 times and it is shown that it can reach a factor of more than 100.

Much of the development of the CRYRING facility has been aimed at the production, handling and measurement of weak beams, often of ions that are difficult to produce in the ion sources. Due to the diverse requirements for ions, several different ion source types are in use. To be able to handle and measure the weak beams, the beam diagnostic systems have been improved. The ECR source is in regular use for single pass experiments and will be used for experiments in the storage ring before the summer of 2003. The EBIS source has been renovated and upgraded with a new electron gun and will be back in operation in May 2003.

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 <2 ns. For the test we have injected the light of a dye laser pulse (R6G in Methanol: 581 nm, 1 mJ, pumped by the 2nd harmonic of the Nd:YAG laser, 10 Hz) and stored in the optical ring for a time of about 2.5 μs. The electro-optical device works in a broad band of optical wavelengths.

The ECR source now delivers beams to experiments. The EBIS source, CRYSIS, has been used with some radioactive species such as tritium, and uranium. The research groups studying molecules and molecular clusters often request ions that can only be produced in small amounts. Thus, weak beams, less than 1 nA from the ion source, have been successfully injected into the ring and stored. Furthermore fast ramping of the magnets during acceleration is reported. 1 OVERVIEW CRYRING is a 52-m circumference ion storage ring. Bρ max is 1.44 Tm, giving a maximum energy of 96q 2 /A 2 MeV/u. q and A are ion charge and mass. The injection energy is 300 keV/A if q/A>0.23 so the ions can be accelerated in the RFQ, otherwise 40 keV total energy. 109 different ions have been stored in the ring, 30 different ones the last year. An EBIS ion source produces highly charged ions up to i.e. Pb 60+ . It is used both for injection in the ring and for low energy experiments. A recent addition is an ECR source for medium charged ions, which presently only is used for low energy experiments. The beamline to the ring will soon be finished.

The electron cooler at CRYRING is now operating with a superconducting gun solenoid and an electron beam that is adiabatically expanded with a factor of up to 100. This paper describes the new gun solenoid and electron gun. It presents measurements made on longitudinal cooling forces with different expansion factors, electron densities, magnetic field strengths and beam alignments. It also presents studies of a transverse beam instability that appears when a misalignment is introduced between ion and electron beams. Finally, some measurements of dielectronic recombination that directly yield transverse and longitudinal electron temperatures are discussed.

We have used a transverse instability that can be excited in an electron-cooled ion beam in order to produce beams with well-defined emittances. These beams have been cooled and the transverse cooling times have been stud- ied as functions of the emittance. Ions of different charge states (D+ ,F 6+ and Pb54+) have been used for the mea- surements to investigate the charge-state dependence of the cooling time. Comparisons are also made with numerical simulations of the cooling process. Electron cooling is a technique for reducing the emittance of stored ion beams that works best for beams of small emittances. More precisely, typical quantities like emit- tances, beam diameters, etc., shrink approximately expo- nentially with time if the velocity spread of the ion beam is small compared to that of the electron beam (and intrabeam scattering is neglected). At higher velocity spreads, the de- crease is slower than in the exponential regime. To know the cooling rate as a function of the emittance of the ion beam is important for applications of electron cooling, and in this paper this emittance-dependent rate is discussed. A method to achieve an ion beam with a transverse pro- file of a particular kind, namely a hollow beam where all particles perform betatron oscillations with the same ampli- tude, is introduced. This method allows us to measure the cooling rate as a function of the betatron amplitude of the ions. Since, in principle, any transverse beam profile can be constructed by superimposing these "elementary beams" with definite betatron amplitudes, the measurements make it possible to predict how the cooling will proceed for a beam with an arbitrary profile.

Much of the work performed to develop the storage ring CRYRING, is done with the aim of broadening the use of the ring. New ions and new kinds of ions are continuously requested and much work has been done, both on the existing ion sources as well as on new kinds. The long list of ions stored in the ring includes singly charged atoms, from protons to 151 Eu + ; highly charged atoms, up to 208 Pb 54+ , and molecules, from the lightest, H 2 + , to heavier, like O 2 + . Recently, also negative ions have been added to the list and, furthermore, clusters of water molecules, the heaviest being H(H 2O)4, with a mass of 73 amu. The adjustment of the electron cooler at the low energies that heavy ions like the water clusters have in the ring, with resulting very low electron currents of less than 1 mA, requires special care. A further important development in the ring is the completion of the gas jet target, which has opened up a new field of experiments, studying collisions between ions and neutral atoms.