windowless hollow cathode lamp for vacuum ultraviolet ionized gas emission lines

Windowless Hollow Cathode

The Model 629 Hollow Cathode is a CW gas discharge source used to ionize molecular or rare gases. It operates with no window and is a rich source of ion lines at wavelengths longer than 25 nm (less than 50 eV). Output line emission depends on the gases used. It is possible to mix or switch gases during operation. It is electrically quiet and features a water cooled anode and cathode. A differential pumping accessory is available to limit the gas load into the spectrometer. Commercial grade gases are generally used and selection may depend on your application. The source body has a port for directly monitoring gas pressure in the discharge. The Model 629 is a flexible source system for vacuum ultraviolet (VUV) wavelength calibration, ultraviolet photoemission spectroscopy (UPS) and other extreme UV spectroscopy applications.
Source operation requires a 2 kV 500 mA current regulated power supply like the McPherson Model 730

Model 629 PDF Data Sheet

Additional Information:

Specifications (Hollow Cathode lamp Data Sheet)

SourceGas discharge
Wavelength range25nm to Visible
Flux in bright lines~10E8 photons/second
Source EmissionIonized gas emission lines
Emission uniformity~12 degree cone angle
Power Supply0.5 A 2000 VDC required sold separate (see Model 730)
RequiresCooling water, gas (He, Ne, Ar, etc.) and 0.5 A at 2000 VDC
Starting pressure0.5 - 1 torr
Operating pressure200 - 400 microns
Sizeapproximately cylindrical, 6" diameter x 13" long
Weight8 lbs

Sample Spectra

example emission spectrum from the hollow cathode lamp

Outline Drawing

McPherson Model 629 Hollow Cathode Source, Outline Drawing

Select Publications

Abstract: A continuous gaseous discharge source suitable for use between 100 I and 1000 A is described. The source is stable, produces little or no electromagnetic interference, and is rich in high intensity lines throughout the extreme uv. The operating characteristics of this source and its spectral output with various gases are presented.
F. Paresce, S. Kumar, C. S. Bowyer
Abstract: The calibration of a McPherson’s fully computer-controlled grazing-incidence spectrograph Model 248/310G (Rowland circle diameter ≈ 1 m) with a MCP/CCD detection system is described. As a DC source of the XUV radiation served the Vacuum UV Hollow Cathode Light Source (McPherson Model 629), which was delivered together with the spectrograph. We concentrated on the MCP-centre- as well as across-MCP-wavelength calibration (a more general theoretical relation than in [1] was found), MCP gain uniformity, and CCD binning linearity. No attention was paid to a resolution of the system, because it changes with the wavelengths and it is determined by properties of the detection system. In general, it is usually much worse than the resolution of the spectrograph itself.
K. Koláčeka, J. Schmidta, V. Boháčeka, M. Řípaa, P. Vrbaa, O. Frolovb, M. Tichýb, A. Jančárekc, M. Vrbovác, E. Skladnik-Sadowskad, M. Sadowskid, and J. Baranowskid
Abstract: We investigated how antireflection (AR) using thin film interference can be achieved in the EUV for multilayer mirrors. This may not been much investigated since AR is not usually needed. AR is not as straightforward as in the visible and neighboring frequencies for several reasons. No materials are entirely transparent in the EUV (indeed materials commonly used in the visible are among the most opaque). The optical constants are not known as well (particularly for compounds), and the antireflection layers can decrease the desired reflection from the multilayer at the “called for” energy. Incorporation of impurities can also be a problem. Nevertheless AR has a role to play in some circumstances.
D. D. Allred and R. S. Turley
Abstract: This paper is a report on our effort to use reflectance measurements of a set of amorphous silicon (a-Si) and uranium (U) multilayer mirrors with an uranium oxide overcoat to obtain the optical constants of a-Si and uranium. The optical constants of U, its oxides, and Si, whether crystalline or amorphous, at 30.4 and 58.4 nm in the extreme ultraviolet (EUV) are a source of uncertainty in the design of multilayer optics. Measured reflectances of multilayer mirror coatings do not agree with calculated reflectances using existing optical constants at all wavelengths. We have calculated the magnitude and the direction of the shift in the optical constants of U and a-Si from reflectivity measurements of DC magnetron sputtered a-Si/U multilayers at 30.4 and 58.4 nm. The reflectivity of the multilayers were measured using a UV hollow cathode plasma light source, a 1 meter VUV monochromator, a back-thinned CCD camera, and a channeltron detector. These reflectance measurements were verified by measurements made at LBNL. The reflectances of the multilayer coatings were measured at 14.5 degrees from normal to the mirror surface. The optical constants were calculated using IMD which uses CURVEFIT to fit the optical constants to reflectivity measurements of a range of multilayer mirrors that varied over a span of 150 - 25.0 nm bilayer thickness. The effects of surface oxide and roughness, interdiffusion, and interfacial roughness were numerically subtracted in fitting the optical constants. The (delta) , (beta) determined at 30.4 nm does not well match the values of c-Si published in the literature (HBOC1), but do approach those of a-Si as reported in literature (HBOC). The difference in the optical constants of c-Si and a-Si are larger than can be attributed to differences in density. Why the optical constants of these two materials vary at 30.4 remains an open question.
M. B. Squires, D. D. Allred, R. S. Turley

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