Soft X-ray spectroscopy using charge-coupled devices with thin poly gates and floating gate output amplifiers

Ralph P. Kraft, David N. Burrows, Gordon P. Garmire, David H. Lumb, John A. Nousek, Mark A. Skinner, James R. Janesick, Thomas Elliot, Stuart A. Collins, Paul Vu

Research output: Contribution to journalConference articlepeer-review

5 Scopus citations


We present data from a charge-coupled device (CCD), collaboratively designed by PSU/JPL/Loral, which incorporates several novel features that make it well suited for soft X-ray spectroscopy. It is a three-phase, frontside illuminated device with 1024×1024 pixels. Each pixel is 18 microns by 18 microns. The device has four output amplifiers: two conventional floating diffusion amplifiers (FDAs) and two floating gate amplifiers (FGAs). The FGA non-destructively samples the output charge, allowing the charge in each pixel to be measured multiple times. The readnoise of a given pixel is reduced as the square root of the number of readouts, allowing one to reduce the amplifier noise of these devices to well below the 1/f knee. We have been able to achieve sub-electron readnoise performance with the floating gate amplifier (0.9 e- rms with 16 reads per pixel). Using the FGA, the measured energy resolution at 5.9 keV is 120 eV (FWHM). The CCD also has a thin poly gate structure to maximize soft X-ray quantum efficiency. Two-thirds of the active area of the chip is covered only by an insulating layer (1000 Å) and a thin poly silicon electrode (400 Å). This design enhances the soft X-ray quantum efficiency, but retains the excellent charge transfer efficiency and soft X-ray charge collection efficiency of front-side illuminated devices. The measured energy resolution at 277 eV is 38 eV (FWHM) with a measured quantum efficiency of 15%. We also show that this device performs well below 100 eV, as demonstrated by the detection of Al L fluorescence at 72 eV with a measured FWHM of 16 eV.

Original languageEnglish (US)
Pages (from-to)320-332
Number of pages13
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - Sep 16 1994
EventEUV, X-Ray, and Gamma-Ray Instrumentation for Astronomy V 1994 - San Diego, United States
Duration: Jul 24 1994Jul 29 1994

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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