An aspect of some embodiments of the present invention relates to a plasma chamber for containing a solution electrode glow discharge (SEGD) apparatus, the plasma chamber comprising a hollow body and a lens. The hollow body is configured to enclose a plasma generated between a solid electrode and a solution electrode, and includes at least one viewing port for letting light generated from the plasma leave the hollow body. The lens is disposed at or near the viewing port, the lens being configured to collect light from the plasma and direct the light onto a light receiving unit.

An aspect of some embodiments of the present invention relates to a plasma chamber for containing a solution electrode glow discharge (SEGD) apparatus, the plasma chamber comprising a hollow body and a lens. The hollow body is configured to enclose a plasma generated between a solid electrode and a solution electrode, and includes at least one viewing port for letting light generated from the plasma leave the hollow body. The lens is disposed at or near the viewing port, the lens being configured to collect light from the plasma and direct the light onto a light receiving unit.

An aspect of some embodiments of the present invention relates to a plasma chamber for containing a solution electrode glow discharge (SEGD) apparatus, the plasma chamber comprising a hollow body and a lens. The hollow body is configured to enclose a plasma generated between a solid electrode and a solution electrode, and includes at least one viewing port for letting light generated from the plasma leave the hollow body. The lens is disposed at or near the viewing port, the lens being configured to collect light from the plasma and direct the light onto a light receiving unit.

An aspect of some embodiments of the present invention relates to a plasma chamber for containing a solution electrode glow discharge (SEGD) apparatus, the plasma chamber comprising a hollow body and a lens. The hollow body is configured to enclose a plasma generated between a solid electrode and a solution electrode, and includes at least one viewing port for letting light generated from the plasma leave the hollow body. The lens is disposed at or near the viewing port, the lens being configured to collect light from the plasma and direct the light onto a light receiving unit.

During a normal operation, alternating drive voltage to be applied between a pair of electrodes provided to face an outer surface of a bottom part of a gas discharge light emitting tube is switched to a voltage value V2 lower than a voltage value V1 at the time of starting lighting. Further, the alternating drive voltage to be applied during the normal discharge operation is intermittently applied in a predetermined cycle and duty ratio to enable adjustment of light emission intensity.