The Model 629 Hollow Cathode Light Source is a continuous gas discharge source that can be used with molecular or the rare gases. It is electrically quiet and is a rich source of spectral lines in the extreme UV to at least 200A.
The source is basically a Schueler lamp which is known to produce strong ion lines. It differs principally from a capillary discharge source in that the negative glow of the discharge is viewed directly, rather than through the positive column of neutral gas as is the case in a capillary discharge.
The source features a water cooled anode and cathode. The cathode is stainless steel and the anode is aluminum. A Kel-F flange electrically isolates the cathode from the anode. A slit seal adapter is also included that can be used to limit the gas leak into the monochromator to the slit opening.
Water: The source should never be operated without water cooling. Normally a flow rate of approximately 1/8 - 1/4 gal/min. (.5-1 liter/min.) is sufficient.
Gas: Commercial grade gases are generally used. A 1/8 NPT tapped hole is located in the top of the anode for installation of a thermocouple gauge to monitor source pressure. Directly opposite this hole, in the bottom of the anode is a 1/4 NPT tapped hole that can be used for auxiliary pumping if needed.
Electrical: A 2000-3000 volt supply producing 250-500 MA. should be used to operate the source. A particularly good HV supply for this source is the McPherson Model 730 current regulated supply. Since the cathode is at high voltage, the source must never be operated with the Plexiglass protective housing removed. Normally the source is mounted directly to the entrance slit of the monochromator or spectrograph.