Windowless, back illuminated CCD

We do not have a wafer fab or foundry for making CCD sensors at McPherson. We buy these cameras. A CCD array detector can tremendously speed up data acquisition of spectra – collecting a complete spectrum in the time a scanning monochromator acquires one point. Direct detection CCDs are sensitive in the soft x-ray, extreme and vacuum ultraviolet as well, or better than in the visible light region (response graph below). They enable rapid data collection, imaging spectroscopy and more. For the time being, because pixels are relatively large, monochromator exit slits with single channel detectors provide slightly better spectral resolution and faster data acquisition of single point (wavelength) for dynamic spectral evolution.

Many companies integrate the same sensors fabricated by companies like e2v in England. We have had good experiences with many different CCD suppliers. Trusted suppliers include Andor-Technology (now Oxford Instruments) and Princeton-Instruments. In our minds Andor has an edge because their SOLIS software talks to our spectrometer motor controller. Other companies like Raptor Photonics and greateyes and even Hamamtsu have items on offer for deep ultraviolet wavelengths.

While our microchannel plate intensifier can make any CCD a viable sensor of short wavelengths, the direct detection CCD collects data with less noise and overhead (HV power supplies, vacuum requirement, etc). Call on us -- we will help if we can.


Additional Information:

Response (from Andor Technology)

Outline Drawing (Andor Technology

Andor Technology direct detection CCD with 1024*256 0.026mm pixels

Select Publications

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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