Mercury arc lamps generate light in the terahertz wavelength spectrum which can be measured by Sciencetech's SPS-300 Terahertz Spectrometer. Since the Sciencetech SPS-300 uses a more stable 75W Mecury Arc lamp as its THz source, this upgrade option allows owners of Sciencetech's older Model SPS-200 to upgrade to it. This Mercury Arc Light Source Housing is water cooled for operation in a 10^-3 Torr environment, and includes a "quick disconnect" water connector such that the arc lamp can be replaced easily without disconnecting and reconnecting the water cooling supply each time. A corresponding power supply and ignitor also needs to be purchased as the existing Model SPS-200 power supply and ignitor for the 150W HgXe lamp will not work with this 75W Hg lamp upgrade.

Housing Design

The THz Mercury Arc Lamp Housing is designed for use inside the vacuum housing of the SPS-200 or SPS-300 THz spectrometer. Hence the arc lamp is water cooled through a copper cooling loop and can withstand a vacuum environment of up to 10^-3 Torr. The arc lamp housing has a 1/2" output port for the arc lamp to exit. It also has a quick water disconnect loop to allow the easy removal and replacement of the 75W Hg arc lamp inside.

Continuous Broadband THz light vs. Monochromator THz light

While femto-second lasers can create a very powerful THz light source several orders of magnitude more powerful than an Hg arc lamp, this light is monochromatic and only centers on a particular chosen wavelength. It is also a temporal pulsating light source. A mercury arc lamp on the other hand, is a broadband THz light source that emits a continuous THz spectrum from 5-600cm^-1 (actually even wider) that does not pulsate.

Arc Lamp Performance in THz Spectral Range

The 75W Hg arc lamp generates a measurable continuous broadband THz light in the 5-600cm^-1 spectral region. It is approximately 8X more powerful than a globar in the 5-30cm^-1 region, about 2-3X more powerful in 30-100cm^-1 region, about 10-20% more powerful in the 100-300cm^-1 region, and about the same thereafter in the 300-600cm^-1 region.

Service Life

The guaranteed operating life for this lamp is 1000 hrs with a reduction of the output of max. 50%. The normal useful operating life can be between 2000 to 4000 hrs.

Stability

Sciencetech replaced the older 150W HgXe arc lamp with this 75W Hg arc lamp in the SPS-300 due its higher stability and less arc wander. While the older 150W HgXe had a stability of 1%, this 75W Hg lamp has a stability of less than 0.2% in the critical 25-100cm^-1 range. Internal test conducted at McMaster University (Hamilton, Canada) confirms this specification and in fact, can achieve higher than 0.2% in this region where the mercury plasma provides the signal over a period of 15 minutes.

Technical Specifications

• Light output port diameter: 1/2" Hole
• Brass Housing Shroud, 2.125" outside diameter
• 1/4" diameter copper water cooling tube supports flow rate of 1L/min
• 5" Optical Height to center of output light port.
• Vertically mounted Hg Arc Lamp
• Anodized Aluminum Base with Mounting Holes
• For a graph of the effecitve temperature (K) versus the wavelength (μm), please see the attached file.