Abstract

We have developed an inexpensive, low-noise, high-resolution charge-coupled device (CCD) camera for imaging applications in the soft-x-ray region. It is capable of photon counting, and because it is cryogenically cooled, it can achieve integration times of several hours. A P31 phosphor coating on the CCD active surface downconverts incident x-rays with high efficiency and no loss in spatial resolution. The aluminum camera body is kept under moderate vacuum (1–10 mTorr) by a sorption pump for thermal insulation and unimpeded propagation of x rays to the detector plane. An aluminum coated Si₃N₄ entrance window delivers acceptable throughput down to 200 eV x-ray energies and effectively blocks external visible-light sources. The internal 0.8 L liquid-nitrogen Dewar flask maintains the detector substrate at –125°C by means of a flexible copper cold finger for ~10 h under ambient conditions. A slow-scan CCD sequencing and sampling circuit based on a CAMAC system provides standard image erasure, integration, and readout functions under computer control. Data-acquisition software permits convenient user manipulation of camera operating parameters as well as on-line image display. Our characterization of the CCD camera with 350 eV x-rays indicates good performance at 1 photon/pixel•s rates.

© 1990 Optical Society of America