Scintillation screen

Whereas scintillation screens can be used to directly view x-rays passing through the body, the dose to a patient is too high. Instead, scintillation screens are combined with video cameras or electronic intensifier tubes and video cameras. This detection scheme is used in digital radiography where digital x-ray images are recorded, and fluoroscopy where temporal processes are to be followed. 

Other uses are to produce phosphorescence and fluorescence in organic compounds and for scintillation screens on instruments used to detect radiation. Radium salts were used in the past to paint the dials of luminous clock faces that glow in the dark. 

CCD detectors are now used extensively at s)m-chrotrons and increasingly in-house in combination with a high-brilliance X-ray generator (Naday et ah, 1998 Westbrook and Naday, 1997). Figure 5.4 shows the principal of the CCD detector, which consists of a scintillation screen attached to the face of the... 

Therefore, a new detector design, based on a scintillating screen lens coupled to a CCD camera, was developed and has been successfully employed in numerous applications (Koch et al., 1995). Beyond the... 

Fig. 7.5. Imaging system for photon-counting scintillation imaging (PCSI). The diagram shows mycelium pre-grown over a scintillant screen 2-aminoisobut3ric acid labelled in the carboxy-group with was added at the centre of the colony. Photons elicited by / -radiation from the screen are cumulatively recorded by the photon-counting camera. For use with soil systems an inverted camera is used, with the screen placed on top of the mycelium growing over soil, (see Watkinson et al., 2005).

For this test, the target was scanned by the read-out beam in 256 x 256 steps. The full width of the point-spread function (PSF) is 3 pixels, corresponding to 43 TV-line pairs . At FWHM, the width is 1.5 pixels, or 85 TV-line pairs . Thus the 256 pixels in both directions are not at all independent. This result clearly shows the degradation of the imaging performances of a Vidicon system by the scintillation screen. 

The sensitivity of a vidicon detector over its area is subject to nonuniformities of the scintillator screen, the photocathode, and the target. A typical result of a sensitivity test is shown in Fig. 19b from K It is very stable and therefore the data can be corrected in a reliable way. 

The data are at present recorded on video tape for later digitization and processing. The scintillator screen, deposited on a fiber optics face plate is either ZnS(Ag) or Gd S 0(Tb). A spatial resolution of 0,5 mm FWHM has been measured. The system has been used in diffraction measurements of polymer samples and in protein crystallography as well. At present a quantitative analysis of the collected data is in progress. 

SEM (scanning electron microscopy)—an electron beam is focused onto a small region of a sample contained within a vacuum. The beam is scanned across the sample and the backscattered electrons (those undergoing elastic collisions) and the secondary electrons (those electrons released through inelastic collisions) are collected on a positively charged detector to obtain an image on a scintillation screen or electronic detector. 

Arrangement of Ernest Marsden s experiment A-B, alpha particle source. R-R, gold foil. P, lead plate. S, zinc sulfide scintillation screen. M, microscope. 

His equipment was similar to Marsden s, a small brass box fitted with stopcocks to admit and evacuate gases from its interior, with a scintillation screen mounted on one end. For an alpha source he used a beveled brass disk coated with a radium compound ... 

Schippers JM, Boon SN, van Luijk P (2002) Applications in radiation therapy of a scintillating screen viewed by a CCD camera. Nucl Instmm Methods Phys Res Sect A Accelerators Spectrometers Detectors Assoc Equip 477 480-485... 

Nagarkar W, Miller SR, Tipnis SV, Lempicki A, Brecher C, Lingertat H (2004) A new large area scintillator screen for X-ray imaging. Nucl Instrum Methods Phys Res Sect B Beam Interact Mater Atoms 213 250-254... 

The most widely used fiat detector (FD) design is based on a two-level, indirect conversion process of X-rays to light (Granfors et al. 2001 Antonuk et al. 1997 Spahn et al. 2000 Yamazaki et al. 2004 Ducourant et al. 2003). In the first step, the X-ray quantum is absorbed by a fluorescence scintillator screen, e.g., a cesium iodide (Csl) substrate, converting it into visible light. In the second step, this light is received by a photodiode array, e.g., based on amorphous silicon (a-Si), and converted into electrical charge. 

The first commercially available multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) setup was the Plasma 54, introduced in 1992 by VG Elemental. This mass spectrometer incorporated the detector platform from the Sector 54 thermal ionization mass spectrometer and included an electrostatic analyzer before the entrance to the magnetic sector. This instmment featured seven Faraday cups and a Daly detector. The Daly detector [7] incorporates an A1 knob maintained at +25 kV together with a scintillator screen and photomultiplier (Figure 3.2). Incoming ions are accelerated to the A1 knob and large numbers of secondary electrons are produced as result of the impact of these ions on the aluminum surface. These electrons are then accelerated towards the scintillator. 

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