Virtual Cathode Diagnostics with a Large Dynamic Range for a Continuous Wave SRF Photoinjector

In a SRF photoinjector the close relationship between the laser pulse and the generated electron bunch parameters requires continuous monitoring of some of the laser pulse parameters. A laser diagnostic system, called virtual cathode, is a key part of a system that controls the stability of the laser. One of the main challenges for the virtual cathode is to cover the large dynamic range of the photocathode laser between commissioning at 120 Hz and operation at 1.3 GHz repetition rate with constant laser pulse parameters. The design of the virtual cathode as well as first measurements with a photocathode drive laser for the SRF injector test facility GunLab of BERLinPro will be presente

CAVITATION EROSION WEAR OF METALLIC SPECIMENS USING THE NEW COMPACT ROTATING DISK DEVICE

A more compact version of the rotating disk device (where a disk with cavitation inducers and specimens fixed on it rotates in water to provide cavitating flow) is used here to study the failure by cavitation in metallic specimens. The damage in the specimens is measured by mass loss versus exposition time to cavitating flow diagrams. Images of the test specimens obtained by electronic microscope are also shown and discussed. After 25 hours working in cavitating conditions, aluminum, brass and cast iron are weared by the cavitation phenomenon, resulting in pitting formation and mass loss. After each 5 hours operating in cavitating conditions, the specimens are cleaned by ultrasound, dried and weighted in a digital balance to obtain the mass loss in the process by comparing to its initial weight. All specimens, aluminum, brass and cast iron, were eroded by cavitation although in the aluminum the mass loss was lesser than the expected. The brass specimen was eroded as expected, mas no mass loss could be attained for the cast iron due to specimen oxidation

Machine Protection Considerations for BERLinPro

The Berlin energy recovery linac project BERLinPro at the HZB is a 50 MeV ERL test facility, which addresses physical and technological questions for future superconducting rf based high brightness, high current electron beam sources. The combination of a 100 mA cw beam, electron bunches with normalized emittances lower than 1 mm mrad and the magnet optics of BERLinPro leads to power densities capable to harm the accelerator components within microseconds if total beam loss occurs. Furthermore, continuous beam loss on the level of 10 5 has to be controlled to avoid activation and to protect the SRF, beam diagnostics and other infrastructure components. In this paper, we present the evaluation of the required key parameters of the BERLinPro machine protection system and present its first conceptual desig

Studies for a Photon Collider at the ILC

One option at the International Linear Collider is to convert the electron beams into high energy photon beams by Compton scattering a few millimetres in front of the interaction region. Selected physics channels for this option have been analysed and technical issues have been studied. So far no showstoppers for this option have been found.Comment: V2: Minor changes, accepted by NI

Structure of mixed ombrophyllous forests with Araucaria angustifolia (Araucariaceae) under external stress in Southern Brazil.

This study is part of the Floristic and Forest Inventory of Santa Catarina, conceived to evaluate forest resources, species composition and structure of forest remnants, providing information to update forest conservation and land use policy in Southern Brazilian State of Santa Catarina (95 000km²). In accordance to the Brazilian National Forest Inventory (IFN-BR), the inventory applies systematic sampling, with 440 clusters containing four crosswise 1 000m² plots (20x50m) each, located on a 10x10km grid overlaid to land use map based on classification of SPOT-4 images from 2005. Within the sample units, all woody individuals of the main stratum (DBH?10cm) are measured and collected (fertile and sterile), if not undoubtedly identified in field. Regeneration stratum (height>1.50m; DBH<10cm) is registered in 100m² in each sample unit. Floristic sampling includes collection of all fertile trees, shrubs and herbs within the sample unit and in its surroundings. This study performs analysis based on 92 clusters measured in 2008 within an area of 32 320km² of mixed ombrophyllous forests with Araucaria angustifolia located at the state’s high plateau (500m to 1 560m above sea level at 26º00’-28º30’ S and 49º13’-51º23’ W). Mean density (DBH?10cm) is 578 individuals/ha (ranging from 85/ha to 1 310/ha), mean species richness in measured remnants is 35 (8 to 62), Shannon and Wiener diversity index (H’) varies between 1.05 and 3.48. Despite high total species diversity (364 Magnoliophyta, five Coniferophyta and one tree fern) and relatively high mean basal area (25.75m²/ha, varying from 3.87 to 68.85m²/ ha), the overwhelming majority of forest fragments are considered highly impacted and impoverished, mostly by logging, burning and extensive cattle farming, turning necessary more efficient protection measures. Basal area was considered an appropriate indicator for stand quality and conservation status

Inventário de Dicksonia sellowiana Hook. em Santa Catarina.

(Inventário de Dicksonia sellowiana Hook. em Santa Catarina). A intensa exploração comercial de Dicksonia sellowiana a deixaram na categoria de ameaçada de extinção, sendo incluída na lista brasileira de espécies da flora ameaçada de extinção. Por isso, o presente trabalho visa apresentar o estudo da distribuição das populações de D. sellowiana para apontar os locais de maior ocorrência da espécie em Santa Catarina, e avaliar a relação da densidade populacional com fatores ambientais, como altitude e clima. Foram instaladas 225 unidades amostrais, com 4.000 m2 nas regiões do planalto e oeste catarinense, baseadas na grade de 10 km x 10 km conforme procedimento do Inventário Florístico Florestal de Santa Catarina. Nestas 225 unidades amostrais, D. sellowiana foi encontrada em 94, com variação de um a 391 indivíduos. A grande densidade da espécie em áreas mais elevadas (superiores a 1.000 m) está relacionada com os dados climáticos que influenciam a população diretamente, apontados pelo Critério de Informação de Akaike corrigido, ou seja, a altitude e a variação de temperatura que ela provoca. Observou-se também, que a espécie apresenta maior concentração da população nos menores intervalos de altura e diâmetro, chegando a elevadas densidades com até 977 indivíduos/ha em algumas áreas. As informações obtidas pelo inventário sobre esta espécie possibilitam indicar medidas de conservação para a espécie, como área a serem conservadas e apoio a produtores rurais

Generation of intense and coherent sub femtosecond X ray pulses in electron storage rings

Temporally short X ray pulses are an indispensable tool for the study of electron transitions close to the fermi energy and structural changes in molecules undergoing chemical reactions which take place on a time scale of hundreds of femtoseconds. The time resolution of experiments at 3rd generation light sources which produce intense synchrotron radiation is limited fundamentally by the electron bunch length in the range of tens of picoseconds. Here we propose a new scheme for the generation of intense and coherent sub femtoseconds soft X ray pulses in storage rings by applying the echo enabled Harmonic Generation eeHG method. Many issues for obtaining the eeHG structure such as two modulators and a radiator are solved by a paradigm shift in an achromatic storage ring cell. numerical demonstration of the feasibility of the scheme for the BeSSY ii beam parameters is presente

Extending Upward Planar Graph Drawings

In this paper we study the computational complexity of the Upward Planarity Extension problem, which takes in input an upward planar drawing $\Gamma_H$ of a subgraph $H$ of a directed graph $G$ and asks whether $\Gamma_H$ can be extended to an upward planar drawing of $G$. Our study fits into the line of research on the extensibility of partial representations, which has recently become a mainstream in Graph Drawing. We show the following results. First, we prove that the Upward Planarity Extension problem is NP-complete, even if $G$ has a prescribed upward embedding, the vertex set of $H$ coincides with the one of $G$, and $H$ contains no edge. Second, we show that the Upward Planarity Extension problem can be solved in $O(n \log n)$ time if $G$ is an $n$-vertex upward planar $st$-graph. This result improves upon a known $O(n^2)$-time algorithm, which however applies to all $n$-vertex single-source upward planar graphs. Finally, we show how to solve in polynomial time a surprisingly difficult version of the Upward Planarity Extension problem, in which $G$ is a directed path or cycle with a prescribed upward embedding, $H$ contains no edges, and no two vertices share the same $y$-coordinate in $\Gamma_H$

The value of hydrologic information for watershed management programs: The case of Camboriú, Brazil

Article explores the value of hydrologic modeling and monitoring with respect to two dimensions: scientific credibility and use of generated knowledge in the design, implementation, and evaluation of the watershed management program in the Camboriú watershed, Brazil