Performance Characterization of a Solenoid-type Gas Valve for the H−H^{-} Magnetron Source at FNAL

The magnetron-style $H^{-}$ ion sources currently in operation at Fermilab use piezoelectric gas valves to function. This kind of gas valve is sensitive to small changes in ambient temperature, which affect the stability and performance of the ion source. This motivates the need to find an alternative way of feeding H2 gas into the source. A solenoid-type gas valve has been characterized in a dedicated off-line test stand to assess the feasibility of its use in the operational ion sources. $H^{-}$ ion beams have been extracted at 35 keV using this valve. In this study, the performance of the solenoid gas valve has been characterized measuring the beam current output of the magnetron source with respect to the voltage and pulse width of the signal applied to the gas valve.Comment: 4 pp. arXiv admin note: text overlap with arXiv:1701.0175

Implementation of Design Changes Towards a More Reliable, Hands-off Magnetron Ion Source

As the main $H^{-}$ ion source for the accelerator complex, magnetron ion sources have been used at Fermilab since the 1970s. At the offline test stand, new R&D is carried out to develop and upgrade the present magnetron-type sources of $H^{-}$ ions of up to 80 mA and 35 keV beam energy in the context of the Proton Improvement Plan. The aim of this plan is to provide high-power proton beams for the experiments at FNAL. In order to reduce the amount of tuning and monitoring of these ion sources, a new electronic system consisting of a current-regulated arc discharge modulator allow the ion source to run at a constant arc current for improved beam output and operation. A solenoid-type gas valve feeds $H_{2}$ gas into the source precisely and independently of ambient temperature. This summary will cover several studies and design changes that have been tested and will eventually be implemented on the operational magnetron sources at Fermilab. Innovative results for this type of ion source include cathode geometries, solenoid gas valves, current controlled arc pulser, cesium boiler redesign, gas mixtures of hydrogen and nitrogen, and duty factor reduction, with the aim to improve source lifetime, stability, and reducing the amount of tuning needed. In this summary, I will highlight the advances made in ion sources at Fermilab and will outline the directions of the continuing R&D effort.Comment: 4 pp. arXiv admin note: substantial text overlap with arXiv:1701.0175

Improvements on the Stability and Operation of a Magnetron H- Ion Source

The magnetron H- ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated offline test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. A new cesium oven was designed and tested in order to avoid glass pieces that were present with the previous oven, improve thermal insulation and fine tune its temperature. A current-regulated arc modulator was developed to run the ion source at a constant arc current, providing very stable beam outputs during operations. In order to reduce beam noise, the addition of small amounts of N2 gas was explored, as well as testing different cathode shapes with increasing plasma volume. This paper summarizes the studies and modifications done in the source over the last three years with the aim of improving its stability, reliability and overall performance.Comment: 8 pages, 19 figure

NATURAL HISTORY OF LEIOCEPHALUS SEMILINEATUS IN ASSOCIATION WITH SYMPATRIC LEIOCEPHALUS SCHREIBERSII AND AMEIVA LINEOLATA

We examined diet, habitat use, and behavior (focal animal observations of intraspecific interactions, escape behavior, and activity period) of Leiocephalus semilineatus from near Puerto Alejandro, Provincia de Barahona, República Dominicana, and compared some parameters to similar data collected at a site near Baní, Provincia de Peravia. Leiocephalus semilineatus is found in sympatry in dry scrub forests at both sites with Ameiva lineolata, an active-foraging teiid of approximately the same size, and at the Puerto Alejandro site with a larger congener, L. schreibersii. Leiocephalus semilineatus and L. schreibersii from Puerto Alejandro exhibited sexual size dimorphism, whereas L. semilineatus from the Baní site and A. lineolata did not. Leiocephalus semilineatus spent most of the time motionless; other observed activities were interactions with conspecifics, movement, and feeding. Lizards were active from shortly after sunrise to sundown, although activity peaked in late morning. Mean cloacal temperatures of L. semilineatus did not differ significantly from those of the other two species, but were significantly above ambient temperatures. Reproductive condition of collected specimens was examined and no correlation was found between snout-vent length and egg, follicle, or testis size. Clutch size was 1–2. Diets consisted primarily of invertebrates and did not differ significantly between the three species

Overview of Recent Studies and Design Changes for the FNAL Magnetron Ion Source

This paper will cover several studies and design changes that will eventually be implemented to the Fermi National Accelerator Laboratory (FNAL) magnetron ion source. The topics include tungsten cathode insert, solenoid gas valves, current controlled arc pulser, cesium boiler redesign, gas mixtures of hydrogen and nitrogen, and duty factor reduction. The studies were performed on the FNAL test stand, with the aim to improve source lifetime, stability, and reducing the amount of tuning needed.Comment: 8 p

Manejo de ácaros-praga em soja.

Reconhecimento. Danos e manejo.bitstream/item/54312/1/folder-acaros-soja-COAMO.pdfFolder 01/2012

Experimental study of optimal measurements for quantum state tomography

Quantum tomography is a critically important tool to evaluate quantum hardware, making it essential to develop optimized measurement strategies that are both accurate and efficient. We compare a variety of strategies using nearly pure test states. Those that are informationally complete for all states are found to be accurate and reliable even in the presence of errors in the measurements themselves, while those designed to be complete only for pure states are far more efficient but highly sensitive to such errors. Our results highlight the unavoidable tradeoffs inherent to quantum tomography.Comment: 5 pages, 3 figure