The photoinjector test facility at DESY, Zeuthen site (PITZ), was built to develop and optimize photoelectron sources for superconducting linacs for high-brilliance, short-wavelength free-electron laser (FEL) applications like the free-electron laser in Hamburg (FLASH) and the European x-ray free-electron laser (XFEL). In this paper, the detailed characterization of two laser-driven rf guns with different operating conditions is described. One experimental optimization of the beam parameters was performed at an accelerating gradient of about 43 MV=m at the photocathode and the other at about 60 MV=m. In both cases, electron beams with very high phase-space density have been demonstrated at a bunch charge of 1 nC and are compared with corresponding simulations. The rf gun optimized for the lower gradient has surpassed all the FLASH requirements on beam quality and rf parameters (gradient, rf pulse length, repetition rate) and serves as a spare gun for this facility. The rf gun studied with increased accelerating gradient at the cathode produced beams with even higher brightness, yielding the first demonstration of the beam quality required for driving the European XFEL: The geometric mean of the normalized projected rms emittance in the two transverse directions was measured to be 1:26 ` 0:13 mm mrad for a 1-nC electron bunch. When a 10% charge cut is applied excluding electrons from those phase-space regions where the measured phase-space density is below a certain level and which are not expected to contribute to the lasing process, the normalized projected rms emittance is about 0.9 mm mrad
ResumenCon la finalidad de evaluar el establecimiento de cinco cultivos de cobertura y determinar su aporte potencial a la fertilidad del suelo en función a la extracción total de nutrientes, se instaló un experimento en la Estación Experimental "El Choclino" del Instituto de Cultivos Tropicales, ubicado en la región de San Martín, Perú. Cinco cultivos de cobertura fueron sembrados: Arachis pintoi Krapov. & W.C. Greg, Calopogonium mucunoides (L.), Callisia repens (Jacq.) L., Canavalia ensiformis (L.) y Centrosema macrocarpum Benth. El porcentaje de cobertura alcanzado por Canavalia, fue significativamente superior a los demás cultivos, logrando el cubrimiento total del suelo a los 90 días después de la siembra. La mayor producción de biomasa foliar y radicular sobre la base de materia seca, se consiguió con Centrosema (9.61 t ha-1 y 2.76 t ha-1, respectivamente). Las cantidades de Nitrógeno (311 kg ha-1), Fósforo (24.97 kg ha-1) y Potasio (155.61 kg ha-1) extraídas por Centrosema fue significativamente mayor a las extraídas por las otras coberturas. Para las condiciones del ensayo, Canavalia fue el cultivo de cobertura más apropiado como herramienta de manejo para reducir el crecimiento de vegetación espontanea y proteger al suelo de la erosión al cubrir el suelo en menor tiempo. Para mejorar la fertilidad del suelo a través del reciclaje de nutrientes se recomienda usar Centrosema, por presentar la mayor capacidad extractiva de nutrientes del suelo y producir más cantidad de materia seca.
AbstractIn order to evaluate the establishment of five cover crops and their potential to increase soil fertility through nutrient uptake, an experiment was installed at the Research Station of Choclino, San Martin, Peru. Five cover crops were planted: Arachis pintoi Krapov. & W.C. Greg, Calopogonium mucunoides (L.), Callisia repens (Jacq.) L., Canavalia ensiformis (L.) and Centrosema macrocarpum Benth. The percentage of cover of Canavalia, was significantly higher than the others, reaching total cover at 90 days after planting. The highest above and below ground dry biomass was for Centrosema (9.61 t ha-1 y 2.76 t ha-1, respectively). The rates of Nitrogen (311 kg ha-1), Phosphorous (24.97 kg ha-1) and Potassium (155.61 kg ha-1) extracted by Centrosema were significatively higher than the other cover crops. Therefore, the most appropriate cover crop under the study conditions was Canavalia allowing it to be used as a management tool to reduce spontaneous vegetation growth and to protect the soil from erosion by covering it in less time. To improve soil fertility through nutrient cycling the use of Centrosema is recommended due to its highest nutrient extraction capacity and dry biomass production.
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