Photoelectron emission from metal surfaces induced by VUV-emission of filament driven hydrogen arc discharge plasma

Abstract

Photoelectron emission measurements have been performed using a filament-driven multi-cusp arc discharge volume production H − ion source (LIISA). It has been found that photoelectron currents obtained with Al, Cu, Mo, Ta and stainless steel (SAE 304) are on the same order of magnitude. The photoelectron currents depend linearly on the discharge power. It is shown experimentally that photoelectron emission is significant only in the short wavelength range of hydrogen spectrum due to the energy dependence of the quantum efficiency. It is estimated from the measured data that the maximum photoelectron flux from plasma chamber walls is on the order of 1 A per kW of discharge power.

Hydrogen plasma induced photoelectron emission from low work function cesium covered metal surfaces

“…It has been shown earlier that the PE current measured from clean metal samples increases linearly with the discharge power. 29 A VUV emission spectrum measured from the hydrogen plasma with a spectrometer consisting of a monochromator (McPherson model 234/302), holographic grating, and photomultiplier tube (ET Enterprises 9406B) is presented in Fig. 3.…”

“…making it impossible to determine the origin of electrons in the plasma. The PE current was measured with an updated version of a previous apparatus 29 with an integrated Cs oven and a deposition monitor. The light emitted by the hydrogen plasma passes through the extraction aperture (1 4 mm) of the plasma chamber and travels through the collimator (1 6 mm) and illuminates the sample (4 cm behind the collimator, 90 cm away from the plasma generator).…”

“…In the filament-driven arc discharge, the total PE current from the plasma chamber walls has been estimated to be in the order of 1 A per kW of discharge power, which corresponds to almost 10% of the arc current of 14 A at 70 V discharge voltage. 29 A thin layer of alkali metal can increase the PE emission by a factor of 2-3.5 at optimal layer thickness. The results obtained in this study suggest that the PE emission especially from cesiated surfaces should be considered to be included in plasma simulations, in which the plasma surface interaction is taken into account.…”

“…Thus, an increase in the PE emission is expected with a buildup of a thin Cs layer. It has been shown that low temperature hydrogen plasma induced PE emission from clean metals is predominantly caused by radiation at wavelengths shorter than 150 nm, 29 i.e., Lyman-alpha (121.6 nm) and Werner-band (84-158 nm) emission, which is due to the wavelength dependence of the quantum efficiency first increasing towards shorter wavelengths and then decreasing at wavelengths below 50 nm. 30 The Lyman-alpha and Werner-band range have also been found to dominate the plasma emission spectral power in the filament-driven arc discharge.…”

Photoelectron emission from metal surfaces induced by radiation emitted by a 14 GHz electron cyclotron resonance ion source

“…6 Previous work with light ion sources suggests that PE emission could contribute to properties of hydrogen ion source plasmas. 7 ECR plasmas emit less intense VUV-radiation compared to light ion sources, since typical ECRISs operate at lower neutral gas pressure. However, ECR plasmas emit characteristic X-rays and bremsstrahlung, and common metals have high QE at the X-ray parts of the emission spectrum as well.…”