Quantification of the atomic hydrogen flux as a function of filament temperature and H2 flow rate

Abstract

An isothermal sensor is developed to quantify the atomic hydrogen flux on a surface, which can be located at any distance from the molecular hydrogen cracking unit. This flux is determined from the measured heat effect due to recombination of atomic hydrogen at the sensor surface. The temperature of the sensor was kept constant at 350 C to keep the heat losses constant during the measurement. Other heat flows due to radiative, conductive, and convective phenomena were quantified with targeted measurements. The design of the sensor allows ample area for the atomic hydrogen recombination reaction; thus enabling the flux values to be determined with high accuracy (errors were between 68:3 Â 10 15 and 63:3 Â 10 16 at cm À2 s À1 ). The atomic hydrogen flux, generated with a commercial atomic hydrogen source was measured as a function of the filament temperature in the range of 1400 À 1950 C and H 2 gas flow in the range of 7:44 Â 10 À6 to 7:44 Â 10 À5 mol=s (10-100 sccm). These measurements showed that the atomic hydrogen flux increases with both filament temperature and H 2 flux.

Density evaluation of remotely-supplied hydrogen radicals produced via tungsten filament method for SiCl4 reduction

“…It has been shown that H 2 molecules adsorb on the W filament surface with a dissociative reaction, and finally desorb as hydrogen radicals. 27,28) In this study, it can be observed that the desorption of hydrogen radicals from the W filament is initiated at a T W of ∼1800 K, and the desorption rate increases with the filament temperature. These results suggest that the SiCl 4 gas material is reduced in the reaction chamber by the remotely-supplied hydrogen radicals.…”

Application of a dual-thermopile radical probe to expanding hydrogen plasmas

“…A catalyst-based radical probe is another alternative to TALIF for hydrogen radical density measurements. The design of a catalytic probe essentially consists of an actively heated thermocouple coated with a specific metal such as Pt [20,21]. When the probe is exposed to hydrogen atom flux in a plasma, the recombination of hydrogen radicals at the metal surface generates a heat load to the probe.…”

“…When the probe is exposed to hydrogen atom flux in a plasma, the recombination of hydrogen radicals at the metal surface generates a heat load to the probe. The probe is typically heated to a constant temperature at known heating powers, and the hydrogen radical flux can be estimated by measuring the probe temperature and solving the heat balance equation for the probe [21]. However, this method might give large errors due to large background heat loads compared with the recombination heat load [22].…”

Electrode structure of a compact microwave driven capacitively coupled atomic beam source

“…Research on this type of hydrogen atomic source have been being made for decades. [11][12][13][14][15][16] Some sources dissociate hydrogen molecules in tungsten tube heated up to 2600 K by bombarding high energy electrons. High temperature components in the source not only produce contaminants, but also limit the operational lifetime, and thus, RF plasma excitation based atom sources are considered promising.…”