Photographic detector

Describe the two common detectors invariably used in emission spectroscopy. Differentiate the plus and negative aspects encountered in (a) Photographic Detector and (b) Photomultiplier Detector, briefly. 

Most nuclear radiation is classified as ionizing radiation because interaction with individual atoms or molecules generally transfers enough energy to exceed the ionization potential of the absorber. Some of the earliest replacements of photographic detectors were based on this ionization process, and developments continue. 

Detection of ions. The observation of electrical signals due to particular ionic species by a detector under conditions that minimize ambiguities from interferences. Ions can be detected by photographic or suitable electrical means. 

Soft x-rays with wavelengths of 1—10 nm ate used for scanning x-ray microscopy. A zone plate is used to focus the x-ray beam to a diameter of a few tens of nanometers. This parameter fixes and limits the resolution. Holographic x-ray microscopy also utilizes soft x-rays with photoresist as detector. With a strong source of x-rays, eg, synchrotron, resolution is in the 5—20-nm range. Shadow projection x-ray microscopy is a commercially estabflshed method. The sample, a thin film or thin section, is placed very close to a point source of x-rays. The "shadow" is projected onto a detector, usually photographic film. The spot size is usually about 1 ]lni in diameter, hence the resolution cannot be better than that. 

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