Detectors and CCDs

If the CCD is permitted to integrate the incident photons for a while, it will accumulate photoelectrons in its array of potential wells that corresponds 

Several terms of importance to Raman applications will be defined in this section. The list is not intended to be comprehensive. 

A basic specification of CCDs is the number and size of pixels in the two-dimensional photoactive area. A common format is 256 x 1024 square pixels that are 25 pm on each side, for an overall area of 6.4 x 25.6 mm. Several formats are listed in Table 8.6. 

As noted earlier, the stored electrons in each potential well are converted to a digital value by an analog-to-digital (A/D) converter, with the gain, )/, usually stated as e /count or electrons per analog to digital unit (e /ADU)  

At any temperature above 0°C, there will be spontaneous generation of elec-tron/hole pairs that is unrelated to incident light intensity. In addition, defects in the silicon may be sources of electrons and contribute dark electrons. Both of these processes are exponentially dependent on temperature, and CCDs must be actively cooled to reduce dark current to acceptable levels. The dark current is usually expressed as e pixel s (electrons per pixel per second) and depends both on the specific device and the temperature. A few examples are listed in Table 8.6. As an approximate rule of thumb, ihe dark current doubles for each 5°C increase in temperature. 

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New developments in solid-state array detectors and CCDs, as well as powerful, specially designed echelle spectrometers and improvements in CSs, have led to a fresh concept for AAS, which allows the simultaneous determination of several elements based on atomic absorption measurements.9... 

For fluorescent detection in multiple channels on microchips, scanning detectors and CCD cameras have been used. For instance, scanning LIF detection was first performed using a galvanoscanner which sequentially probed 16 channels [265] and 48 channels [557],... 

Walter, R.L., et al. High resolution macromolecular structure determination using CCD detectors and synchrotron radiation. Structure 3 835-844, 1995. 

An optical detector with appropriate electronics and readout. Photomultiplier tubes supply good sensitivity for wavelengths in the visible range, and Ge, Si, or other photodiodes can be used in the near infrared range. Multichannel detectors like CCD or photodiode arrays can reduce measurement times, and a streak camera or nonlinear optical techniques can be used to record ps or sub-ps transients. 

The CCD detector and the potentiostat were synchronized in an open-loop configuration by starting the experiment with a common trigger. Careful measurements... 

A modern spectrophotometer (UV/VIS, NIR, mid-IR) consists of a number of essential components source optical bench (mirror, filter, grating, Fourier transform, diode array, IRED, AOTF) sample holder detector (PDA, CCD) amplifier computer control. Important experimental parameters are the optical resolution (the minimum difference in wavelength that can be separated by the spectrometer) and the width of the light beam entering the spectrometer (the fixed entrance slit or fibre core). Modern echelle spectral analysers record simultaneously from UV to NIR. 

CCD detectors (and also image plates), this contamination is a potential source of systematic errors because these devices cannot discriminate with respect to energy. 

The 27-cm telescope is equipped with four CCD detectors and measures the light curves of bright stars in the wavelength range 370-950 nm. The scientific goals of the mission are ... 

Consider you have forgotten to switch on multi-read 28 with your CCD detector and the raw data are full of cosmic-ray spikes. How do you remove them without spoiling the image ... 

In conventional chip experiments, fluorescence scanners are used for chip read-out. In the case of laser scanners, HeNe lasers are used as excitation sources and photomultiplier tubes as detectors, whereas CCD-based scanners use white light sources. The optical system can be confocal or non-confocal. Standard biochip experiments are performed using two fluorescent labels as... 

Experimental equipment for X-ray diffraction methods has improved enormously in recent years. CCD detectors and focusing devices (Goepel mirror) have drastically reduced the data acquisition time. Cryogenic systems have been developed which allow structural studies to be extended down to the liquid helium temperature range. These developments have had important implications for SCO research. For example, fibre optics have been mounted in the cryostats for exploring structural changes effected by light-induced spin state conversion (LIESST effect). Chaps. 15 and 16 treat such studies. 

ED intensity data collected by using a HRTEM and CCD detector reveal a monoclinic crystal structure having the following unit-cell dimensions ... 

Figure 12.2 SGX-CAT data acquisition station. The CCD detector and cryogenic sample handling robot appear in the foreground. The pump to deliver the liquid nitrogen that removes ice from the sample is located at the rear right.

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