摘要:

By means of photodetachment we have detected negative hydrogen ions in an electron cyclotron resonance (ECR) discharge under conditions where highly charged ions are present in the plasma if hydrogen is absent. From the time delay between the laser pulse and the photodetachment (PD) signals we obtained the location of the negative ion clouds in the halo of the plasma. It coincides with the location found for atomic hydrogen ions in previous ion cyclotron resonance heating experiments. The confinement of the ions to these places must be due to the presence of local potential maxima. These maxima imply a potential dip in the core of the plasma. Furthermore, theseH−ions indicate the presence of cold electrons even under conditions where high charge states are produced. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148664

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A spectroscopic method based on the analysis of molecular and atomic spectra of nitrogen was used for the determination of electron distribution functions (EDFs) in electron cyclotron resonance (ECR) discharges run in nitrogen. EDFs were determined for the plasma region seen by the VUV-monochromator. This region includes the hot core plasma surrounded by a less dense and not so hot halo plasma. The EDF between 1.5 and 4.5 eV was determined from the vibrational distribution of excited molecular states of nitrogen, and that in the energy range above 8.5 eV was evaluated from the intensities of different emission lines and bands ofNIandN2.The shape of the EDF in the energy range between 4.5 and 8.5 eV was interpolated by using the electron density measured with Langmuir probes and normalizing the EDF to the same density. Due to the low gas pressure of2×10−5 Torrvibrational relaxation processes on the discharge chamber wall had to be taken into account. In the wavelengths range 30–400 nm the emission spectra of the ECR discharge were measured for the input microwave power rangePin=100–1500 W.This wavelength range includes the emission bands of the molecular transitionsN2(C3&Pgr;u→B3&Pgr;g),N2(a1&Pgr;g→X1&Sgr;g−),andN2+(B2&Sgr;u−→X2&Sgr;g+)and emission lines of the atoms and ions e.g., transitionsN(4P→4S, 120.0 nm),N(2P→2P, 124.3 nm),andN+(3P→3P, 91.6 nm),N+(3D→2P,108.4 nm).For these transitions the experimental emission cross sections for the excitation fromN2(X)and the some intermediate stable states [e.g., from the atomic ground stateN(4S)] are known from the literature. The other cross sections used in our EDF calculations especiallyNandN+excitation cross sections were calculated in this work. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148665

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Energy dispersive x-ray spectroscopy ofK&agr;transitions of neon and chlorine ions inside an electron cyclotron resonance (ECR) plasma is used to analyze the ion charge state distribution (CSD) inside the plasma. Basing on a computer code describing time dependent and stationary solutions of the balance equations for the CSD in ECR plasmas (considering single and multiple ionization and charge exchange processes, radiative recombination, vacancy cascades, and electron shake-off) and considering atomic properties (fluorescence yields, transition rates, x-ray energy shifts, x-ray production cross sections) of ions with different charge states, an approximation of simulated x-ray spectra to measured ones is possible. Thus the result we get is the corresponding CSD and information about the electron energy distribution function in the low energy region in the plasma. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1149228

出版商:AIP    

年代:1998

数据来源: AIP