The X-ray crystallographic, optical spectroscopic, and electrochemical properties of a newly synthesized class of boron-diindomethene (BDI) dyes and their tetrahydrobicyclo precursors (bc-BDP) are presented. The BDI chromophore was designed to show intensive absorption and strong fluorescence in an applicationary advantageous spectral range. Its modular architecture permits fusion of a second subunit, for example, a receptor moiety to the dye's core to yield directly linked yet perpendicularly prearranged composite systems. The synthesis was developed to allow facile tuning of the chromophore platform and to thus adjust its redox properties. X-ray analysis revealed a pronounced planarity of the chromophore in the case of the BDIs, which led to a remarkable close packing in the crystal of the simplest derivative. On the other hand, deviation from planarity was found for the diester-substituted bc-BDP benzocrown that exhibits a "butterfly"-like conformation in the crystal. Both families of dyes show charge- or electron-transfer-type fluorescence-quenching characteristics in polar solvents when equipped with a strong donor in the meso-position of the core. These processes can be utilized for signaling purposes if an appropriate receptor is introduced. Further modification of the chromophore can invoke such a guest-responsive intramolecular quenching process, also for receptor groups of low electron density, for example, benzocrowns. In addition to the design of various prototype molecules, a promising fluoroionophore for Na+ was obtained that absorbs and emits in the 650 nm region and shows a strong fluorescence enhancement upon analyte binding. Furthermore, investigation of the remarkable solvatokinetic fluorescence properties of the "butterfly"-like bc-BDP derivatives suggested that a second intrinsic nonradiative deactivation channel can play a role in the photophysics of boron-dipyrromethene dyes.

Four novel borondipyrromethene (BDP) and -diindomethene (BDI) dyes with one or two (dimethylamino)styryl extensions at the chromophore were synthesized and spectroscopically investigated. An X-ray crystal structure shows that the extended auxochrome is virtually planar. All dyes thus display intense red/near infrared (NIR) absorption and emission. The (dimethylamino)styryl group induces a charge-transfer character that entails bright solvatochromic fluorescence, which is only quenched with increasing solvent polarity according to the energy-gap law. The dye with an additional dimethylanilino group at the meso position of BDP shows a remarkable switching of lipophilicity by protonation. Two dyes with an 8-hydroxyquinoline ligand at the meso position display quenched emission in the presence of Hg2+ or Al3+ owing to electron transfer from the excited BDP to the complexed receptor. The BDI dye presents a pH indicator with bright fluorescence and extremely low fluorescence anisotropy.

No abstract

The Thomson scattering system of the ASDEX upgrade (AUG) tokamak is described. One of the main objectives of AUG is to investigate plasma wall interaction in reactor relevant discharges with a magnetic divertor. The very successful Nd:YAG scattering system developed for its predecessor ASDEX, has been upgraded to give higher spatial and temporal resolution, reliability, and flexibility to different discharge conditions. The system consists of two independently operating devices, each using a cluster of six lasers: One measures the electron temperature and density along three possible vertical chords alternatively through the magnetic axis, or the inner or outer boundary layer; a second chord in the equatorial plane will always cover the magnetic center even in the case of considerable Shafranov shifts. An additional compact spectrometer has been designed for measurements with high radial resolution in the equatorial plane across the separatrix. A third system, using the laser beams for the vertical arrangement once again, has been designed for profile measurements in the energy deposition zone 2 cm above the outer divertor plate. Each laser is run at a repetition rate of 20 Hz and 1 J per pulse. A variety of synchronization modes are available, e.g., 20 Hz/6 J, 120 Hz/1 J etc., or repetitive bursts at 20 Hz. In this case the minimum delay between two pulses is presently limited to ≊30 μs by the existing data acquisition. This mode will be used for investigating fast phenomena such as sawteeth or disruptive instabilities. During the time intervals between the laser pulses the bremsstrahlung radiation (line integral) will be measured by the Thomson scattering detection system to calculate Zeff.

No abstract

Optical control of the photo‐ and electrochemiluminescence of a brightly fluorescent reporter group is possible by switching between the photochromic units of dyads 1 a and 1 b. Irradiation, that is, writing in information, with UV light converts the highly luminescent dihydroazulene 1 a into the weakly emissive vinylheptafulvene 1 b. Readout of the system can be performed by either electrochemically generated or photogenerated luminescence.

Counter injection into ASDEX leads to good particle, momentum, and also energy confinement with XE -80 ms at 1 MW (43 ms for co-injection). The improved confinement develops gradually during the heating phase and correlates with a simultaneous peaking of the density profile. The ion heat transport has to be reduced for a consistent transport analysis, in agreement with theoretical expectations. The sawtooth instability flattens the density profile and transiently reduces the energy content.PACS numbers: 52.55.Fa, 52.50.Gj An important goal of tokamak research is the development of plasma regimes with good confinement under auxiliary heating conditions to provide well established scenarios for the upcoming deuterium-tritium experiments. An important and challenging task is the understanding of the energy and particle transport in a tokamak plasma. In particular, it is the electron transport which is much higher than neoclassical theory predicts and which shows an unexplained variation with plasma parameters. But there is also accumulating experimental evidence that the ion heat transport is enhanced as well above the neoclassical expectation. 1 The effort to increase the plasma temperatures by auxiliary heating generally causes the electron transport to increase even further, resulting in the degraded confinement properties of the L mode. An alternative to the L-mode confinement is the H mode which shows good confinement properties even at high heating power 2 (L denotes low and H high confinement properties).In this paper we report on another operational regime characterized by good confinement properties. It develops when neutral injection as an auxiliary heating method is applied in the counter direction (against the direction of the plasma current). The injection of energetic neutral atoms into the plasma is presently the most successful and reliable auxiliary heating method. The orbits of the energetic ions after ionization depend strongly on the injection geometry. In case of counter injection (ctr-NI) the power and particle deposition profiles are broader and the fraction of ions which is lost during the slowing down phase is somewhat larger. There have been many attempts in the past to study ctr-NI heated plasmas and to compare their characteristics with those under co-injection (co-NI). 3,4 The main results were that particle confinement improves and remarkable differences in impurity transport have been noted. While co-NI reduces the impurity concentration, ctr-NI causes the impurities to accumulate in the plasma center. The different transport behavior was explained on the basis of neoclassical impurity transport in a situa-tion with momentum input and plasma rotation. 5 The energy confinement time T£, however, was found to degrade like that of L-mode plasmas heated with co-NI.On ASDEX we observe improved particle confinement with ctr-NI both affecting the bulk plasma (leading to a density increase without any external gas puffing only fueled by the beam) and giving rise to low-Z and high-Z impurity acc...

The results of divertor studies on ASDEX Upgrade, at currents of up to 1.2 MA and heating powers up to 10 M W are described, with emphasis on the ELMy H-mode. The spatial and temporal characteristics of their heat load, and the simulation of ELMs by a time-dependent scrape-off layer code are described. High gas puff rata were found to lead to a large increase in divertor neutral pressure, at modest changes in %, and to a strong reduction in timeaveraged power flow and complete detachment from both target plates in between ELMs. Using pre-programmed puffs of neon and argon, the radiative power losses could be raised to 75% of the heating power, in H-regime discharges, and the regime of enhanced divertor neutral pressure was found also to lead to an improved pumping of recycling impurities. 1.Introduction:ASDEX Upgrade is a mid-size tokamak w i t h non-circular cross-section (major radius R, , = 1.625m, horizontal minor radius a = 0.5 m, elongation b/a = 1.6), purpose-designed as a poloidal divertor device (Figure 1). Further distinguishing features of it are the poloidal field coils placed outside the toroidal ones, and the presence of a saddle coil ("PSL" .. pssive Stabilising loop) inside the vacuum vessel for stabilising the vertical displacement instability. Together, these two features provide a relatively large space between the vacuum vessel and the X-point of the poloidal field lines, although the present divertor configuration, selected to optimise the heat load distribution, places the target plates relatively close to the x-point.