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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Studies of basic limitations on production, transport and acceleration of the high intensity polarized H{sup −} beam in the RHIC polarized ion source

Basic limitations on the high-intensity polarized H{sup −} ion beam production and transport were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vaporjet ionizer cell. The energy dependence of space-charge effects on the beam instabilities and losses were studied and described in the model of synthetic H{sup +} — H{sup −} beam transport. A xenon gas admixture to the H{sup −} ion production cell and beam transport line greatly improves the space-charge compensation, which is also successfully described in the simulations. These studies are the part of the polarized source upgrade project for RHIC.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Demonstration of a real-time interferometer as a bunch-length monitor in a high-current electron beam accelerator

A real-time interferometer (RTI) has been developed to monitor the bunch length of an electron beam in an accelerator. The RTI employs spatial autocorrelation, reflective optics, and a fast response pyro-detector array to obtain a real-time autocorrelation trace of the coherent radiation from an electron beam thus providing the possibility of online bunch-length diagnostics. A complete RTI system has been commissioned at the A0 photoinjector facility to measure sub-mm bunches at 13 MeV. Bunch length variation (FWHM) between 0.8 ps ({approx}0.24 mm) and 1.5 ps ({approx}0.45 mm) has been measured and compared with a Martin-Puplett interferometer and a streak camera. The comparisons show that RTI is a viable, complementary bunch length diagnostic for sub-mm electron bunches.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Capturing the two-way hydromechanical coupling effect on fluid-driven fracture in a dual-graph lattice beam model

Fluid-driven fractures of brittle rock is simulated via a dual-graph lattice model. The new discrete hydromechanical model incorporates a two-way coupling mechanism between the discrete element model and the flow network. Through adopting an operator-split algorithm, the coupling model is able to replicate the transient poroelasticity coupling mechanism and the resultant Mandel-Cryer hydromechanical coupling effect in a discrete mechanics framework. As crack propagation, coalescence and branching are all path-dependent and irreversible processes, capturing this transient coupling effect is important for capturing the essence of the fluid-driven fracture in simulations. Injection simulations suggest that the onset and propagation of fractures is highly sensitive to the ratio between the injection rate and the effective permeability. Moreover, we show that in a permeable rock, the borehole breakdown pressure, the pressure at which fractures start to grow from the borehole, depends on both the given ratio between injection rate and permeability and the Biot coefficient.

58 GEOSCIENCES↗