Technology demonstration for the DARHT Linear Induction Accelerators
The Dual-Axis Radiographic Hydrodynamics Test (DARHT) facility will employ two 16-MeV, 3-kA Linear Induction Accelerators to produce intense, bremsstrahlung x-ray pulses for flash radiography. Technology demonstration of the key accelerator sub-systems is underway at the DARHT Integrated Test Stand (ITS), which will produce a 6-MeV, 3-kA, 60-ns flattop electron beam. We will summarize measurements of ITS injector, pulsed-power, and accelerator cell performance. Time-resolved measurements of the electron beam parameters will also be presented. These measurements indicate that the DARHT accelerator design is sufficiently advanced to provide the high quality electron beams required for radiography with sub-millimeter spatial resolution.
10-MeV linear induction accelerator for flash radiography
A 10 MeV linear induction accelerator has been built for use in flash radiography. This machine consists of a 1 MeV injector followed by 28 accelerating induction cells. Each accelerating cell adds 320 kV to the electron beam. An electron beam of 2 kA with focal spot diameter < 4 mm on the target has been obtained. Exposure dose at a distance of 1 meter is 90 R, and the pulse length is 90 ns. In this paper the construction of the accelerator and its operation characteristics are presented.
HIGH-TEMPERATURE SOLAR CHEMICAL REACTORS FOR HYDROGEN PRODUCTION FROM NATURAL GAS CRACKING
This study deals with the thermal cracking of natural gas for the coproduction of hydrogen and carbon black from concentrated solar energy without CO2 emission. A laboratory-scale solar reactor (1 kW) was tested and modeled successfully. It consists of a tubular graphite receiver directly absorbing solar radiation, in which a mixture of Ar and CH4 flows. A temperature increase or a gas flow rate decrease results in chemical conversion increase. Methane conversion higher than 75% was obtained. Reaction occurred near the wall where temperature is maximal and gas velocity is minimal due to the laminar flow profile. The work focused also on the design of a medium-scale tubular solar reactor (10 kW) based on the indirect heating concept. A reactor model including gas hydrodynamics and heat and mass transfers coupled to the chemical reaction was developed in order to predict the reactor performances. Temperature and species concentration profiles and final chemical conversion were quantified. According to the results, temperature was uniform in the tubular reaction zone and the predicted chemical conversion was 65%, neglecting the catalytic effect of carbon particles.