Interfacial areas and gas hold-ups in bubble columns and packed bubble columns at elevated pressures

Interfacial areas and gas hold-ups have been determined at pressures up to 1.85 MPa in a bubble column with a diameter of 85.5 mm and for superficial gas velocities between 1 and 10 cm s−1. In some experiments the bubble column was packed with glass cylinders of length 5.0 mm and diameter 4.0 mm. The interfacial areas were determined by the chemical method using the model reaction between CO2 and aqueous diethanolamine (DEA) and hold-ups by observation of height differences.\ud \ud The interfacial areas in the packed bubble column are unaffected by pressure. The gas hold-ups as well as the interfacial areas in the bubble column increase with increasing operating pressure. The magnitude of the pressure influence depends on the superficial gas velocity. The positive influence of pressure on the gas hold-ups and the interfacial in the bubble column originates from the formation of smaller bubbles at the gas distributor

10 kHz repetitive high-resolution TV Thomson scatatering on TEXTOR

In December 2003 a new 10 kHz multiposition Thomson scattering diagnostic with high spatial resolution has become operational on the TEXTOR tokamak. The system is the follow up of the high-resolution double-pulse Thomson scattering diagnostic. The conventional ruby laser has been replaced by a 10 kHz intracavity laser system and the spectrometer detector has been upgraded with two ultrafast complementary metal-oxide-semiconductor cameras combined with a special image intensifier stage. In the initial phase of operation, a burst of 18 pulses decaying from 17 to 8 J, with a repetition rate of 5 kHz, could be extracted from the laser. At a laser energy up to 12 J per pulse, ten electron temperature and density profiles were measured with an observational error of 10% on the electron temperature (T-e) and 5% on the electron density (n(e)) at n(e)=2.5x10(19) m(-3) per spatial element of 12 mm. The resolution of the detection optics enables to sample either the full plasma diameter of 900 mm with 120 spatial channels of 7.5 mm each, or a 160 mm long edge chord with 98 spatial channels of 1.7 mm each. (C) 2004 American Institute of Physics

10 kHz repetitive high resolution TV Thomson Scattering on TEXTOR: design and performance

In late 2003 a 10 kHz multiposition Thomson scattering diagnostic with high spatial resolution became operational on the TEXTOR tokamak. In the initial phase of operation, one burst of 18 pulses of 12 J each with a repetition rate of 5 kHz could be extracted from the laser system. The installation of a low-dope ruby rod (spring 2005) resulted in a system, which can deliver higher pulse energy and moreover a divergence of better than 0.7 mrad, leading to a big improvement in the detection of Thomson scattering photons. Furthermore, the number of laser pulses in one burst could be extended to even more than 30. The achieved laser energy of more than 15 J/pulse makes it possible to measure electron temperature and density profiles with an observational error of 8% on the electron temperature (T-e) and 4% on the electron density (n(e)) at n(e)=2.5 X 10(19) m(-3), per spatial element of 7.5 mm. The viewing optics enables sampling of either the full plasma diameter of 900 mm with 120 spatial channels of 7.5 mm each or a 160 mm long edge chord with 98 spatial channels of 1.7 mm each. The system, which has recently become available for physics exploration, has already been used to study the structure of m=2 magnetic islands and the response of the plasma to off-axis electron cyclotron resonance heating. (c) 2006 American Institute of Physics