Optimization of a charge-state analyzer for ECRIS beams

A detailed experimental and simulation study of the extraction of a 24 keV He-ion beam from an ECR ion source and the subsequent beam transport through an analyzing magnet is presented. We find that such a slow ion beam is very sensitive to space-charge forces, but also that the neutralization of the beam's space charge by secondary electrons is virtually complete for beam currents up to at least 0.5 mA. The beam emittance directly behind the extraction system is 65 pi mm mrad and is determined by the fact that the ion beam is extracted in the strong magnetic fringe field of the ion source. The relatively large emittance of the beam and its non-paraxiality lead, in combination with a relatively small magnet gap, to significant beam losses and a five-fold increase of the effective beam emittance during its transport through the analyzing magnet. The calculated beam profile and phase-space distributions in the image plane of the analyzing magnet agree well with measurements. The kinematic and magnet aberrations have been studied using the calculated second-order transfer map of the analyzing magnet, with which we can reproduce the phase-space distributions of the ion beam behind the analyzing magnet. Using the transfer map and trajectory calculations we have worked out an aberration compensation scheme based on the addition of compensating hexapole components to the main dipole field by modifying the shape of the poles. The simulations predict that by compensating the kinematic and geometric aberrations in this way and enlarging the pole gap the overall beam transport efficiency can be increased from 16 to 45%

Backyard Bug Collecting Results in 6 New State Records for Arkansas, U.S.A.

The aquatic Hemiptera of Arkansas are fairly well documented (see Chordas et al. 2005), but the terrestrial bugs are less well known. Recent projects and publications have begun to address this deficiency. Including the 6 reported herein, there have been 64 Hemiptera species newly recorded for Arkansas between 2005 and 2009 (Chordas et al. 2005, Chordas and Kovarik 2008a, Chordas and Kovarik 2008b). The second author is an invertebrate enthusiast who maintains a large personal collection. The content of this collection is primarily an accumulation of invertebrates captured on or around his property in Clarksville (Johnson County) Arkansas (Figure 1). Identification of the Hemiptera from this “backyard bug collection” revealed 6 species (in 4 Hemiptera families) that are new state records for Arkansas. These 6 include: 2 Coreidae (Leaf-footed bugs), Acanthocephala declivis (Say, 1832) and Piezogaster calcarator (Fabricius, 1803); 1 Largidae (Largid bugs), Largus succinctus (Linnaeus, 1763); 2 Lygaeidae (Seed bugs), Lygaeus kalmii angustomarginatus Parshley, 1919 and Neacoryphus bicrucis (Say, 1825) and 1 Reduviidae (Assassin bugs), Sirthenea stria carinata (Fabricius, 1798). Of note, our record of L. succinctus is the first Arkansas record for this hemipteran family

Duo : Bassoon studio recital

Philipp Friedrich BoddeckerMichel Joseph GebauerGiovanni Antonio BertoliPaul HindemithIgor StravinskyTadd RussoWesley PittmanAlan HovhanessHeitor Villa-LobosFranz TauschEric Ewaze

Spatial distribution of Cherenkov radiation in periodic dielectric media

The nontrivial dispersion relation of a periodic medium affects both the spectral and the spatial distribution of Cherenkov radiation. We present a theory of the spatial distribution of Cherenkov radiation in the far-field zone inside arbitrary three- and two-dimensional dielectric media. Simple analytical expressions for the far-field are obtained in terms of the Bloch mode expansion. Numerical examples of the Cherenkov radiation in a two-dimensional photonic crystal is presented. The developed analytical theory demonstrates good agreement with numerically rigorous finite-difference time-domain calculations.Comment: 14 pages, 5 figures, Journal of Optics A (in press

Television Viewing Does Not Have to Be Sedentary: Motivation to Participate in a TV Exercise Program

The present study explored which underlying motivations induced people to participate in a television exercise program called “The Netherlands on the Move!-television” (NOM-tv). A cross-sectional study was carried out among 1,349 viewers of NOM-tv. The respondents completed the intrinsic motivation inventory (IMI), assessing their levels of intrinsic motivation towards participating in the NOM-tv exercises. The results showed that higher levels of intrinsic motivation (i.e. enjoying the NOM-tv exercises, feeling competent to perform this activity, and willingness to put effort into the exercises) were the most important predictive factors of more frequent participation in the NOM-tv exercises. Future screen-based interventions to reduce sedentary behavior should aim especially at encouraging people's intrinsic orientations towards physical activity in an autonomy-supportive way