Detector cooling

Detector cooling often is accompHshed by providing good thermal conductivity to a suitable cryogen (2). The most readily available coolants are sohd carbon dioxide [124-38-9] [124-38-9] at 195 K, Hquid nitrogen, N2, at 77 K, andhquid hehum. He, at 4.2 K (see Carbon dioxide Helium group ... 

FTIR spectra were collected with a Nicolet 740 spectrometer and a custom built in situ gas flow cell. The spectrometer was equipped with a MCT-B detector cooled by liquid nitrogen. Approximately 15 mg of the MgO catalyst sample was pressed into a self-supported disc and placed in a sample holder located at the center of the cell. The temperature in the cell was measured with a thermocouple placed close to the catalyst sample. Transmission spectra were collected in a single beam mode with a resolution of 2 cm 1. Prior to introduction... 

Intrinsically conducting polymers, 13 540 Intrinsic bioremediation, 3 767 defined, 3 759t Intrinsic detectors, 22 180 Intrinsic fiber-optic sensors, 11 148 Intrinsic magnetic properties, of M-type ferrites, 11 67-68 Intrinsic photoconductors, 19 138 Intrinsic rate expressions, 21 341 Intrinsic semiconductors, 22 235-236 energy gap at room temperature, 5 596t Intrinsic strength, of vitreous silica, 22 428 Intrinsic-type detectors, cooling, 19 136 Intrinsic viscosity (TV), of thermoplastics, 10 178... 

The photomultipliers equipped in the Jasco J-500A and Jasco 500C are Hamatsu R-376 and R-316, respectively. The latter is of S-l type. An InSb photovoltaic cell (Judson) is used as a detector for the wavelength region from 1000 to 2400 nm 283). The InSb detector is cooled with liquid nitrogen. An extension of the CD measurements to 11 p can be conducted by using HgCdTe detectors cooled at liquid He temperature 287). 

The far-infrared emission of the idler frequency was also detected 81) with an InSb detector cooled with liquid He. The power of the pulses was estimated to be about 5 W. Their frequency was not directly measured but only inferred from energy conservation. Later measurements 83> gave a power from 0.25 W at 60 gm to 3 W at 200 jum and a linewidth of 0.1 to 0.5 cm"1 for the signal radiation. 

HPLC-UV-NMR can now be considered to be a routine analytical technique for pharmaceutical mixture analysis and for many studies in the biomedical field. HPLC-UV-NMR-MS is becoming more routine with a considerable number of systems now installed worldwide, but the chromatographic solvent systems are limited to those compatible with both NMR spectroscopy and mass spectrometry. The increased use of HPLC-UV-IR-NMR-MS is possible, but it is unlikely to become widespread, and the solvent problems are more complex. The future holds the promise of new technical advances to improve efficiency, and to enhance routine operation. These approaches include the use of small-scale separations, such as capillary electrochromatography, greater automation, and higher sensitivity and lower NMR detection limits through the use of NMR detectors cooled to cryogenic temperatures. 

Figure 2. Neon spectra (hollow cathode emission) acquired with an SIT detector cooled to —50°C. (a) Real-time detection, 20 ms/scan, neutral density filter (ND) = 0 (b) Readout, after signal integration for 20 seconds (c) Integration equivalent to 10s scan periods. ND filter = 5 (0.001% transmission) was used to attenuate the signal. Equivalent dark spectra were subtracted from each neon...

The basic optical setup was shown in Fig. 12 [90]. The spectra were recorded on a commercially available spectrometer equipped with an external PM setup. The photoelastic modulator modulated the polarization of the IR light at a fixed frequency. Demodulation was performed with a lock-in amplifier and a low-pass filter. After the IR beam passes through the polarizer and modulator, it is focused on the sample, then focused on an mercury-cadmium-telluride (MCT) detector cooled by liquid nitrogen. 

Figure 3.5-13 Influence of sample and instrument parameters on the observed intensity of a Raman line under the conditions of NIR FT Raman spectrometers. The relative output voltage of the Ge detector (cooled with liquid nitrogen) is given for a sample with the absorption spectrum of water. The upper curves, r = 0, represent a liquid sample with a thickness of 1 and 2 cm, respectively. The lower traces, r = 10, 100, and 500, represent a coarse, medium and fine powder, respectively. Abscissa below absolute wavenumbers, above Raman shift.

Raman spectra were obtained with a Spex Triplemate spectrometer(Model 1877) coupled to an EG G intensiTied photodiode array detector cooled thermoelectrically to -40°C, and interTaced with an EG G DMA III Optical Multichannel Analyzer(Mode1 1463). The samples were... 

X-ray spectrometry is generally carried out with Si(Li) detectors. The set-up is similar to that applied to y-ray spectrometry with i-Ge or Ge(Li) detectors cooling of the detector in a cryostat, operation in combination with a preamplifier, an amplifier and a multichannel analyser. The energy resolution is very good, as already mentioned in section 7.6, and makes it possible to distinguish the characteristic X rays of neighbouring elements. Some X-ray emitters that may be used for calibration purposes are listed in Table 7.6. 

The most common medium for detector cooling is liquid nitrogen, however, recent advances in electrical cooling systems have made electrically refrigerated cryostats a viable alternative for many detector applications. 

The properties of the dual-film electrode were characterized by in situ Fourier transform infrared (FTIR) reflection absorption spectroscopy [3]. The FTIR spectrometer used was a Shimadzu FTIR-8100M equipped with a wide-band mercury cadmium teluride (MCT) detector cooled with liquid nitrogen. In situ FTIR measurements were carried out in a spectroelectro-chemical cell in which the dual-film electrode was pushed against an IR transparent silicon window to form a thin layer of solution. A total of 100 interferometric scans was accumulated with the electrode polarized at a given potential. The potential was then shifted to the cathodic side, and a new spectrum with the same number of scans was assembled. The reference electrode used in this experiment was an Ag I AgCl I saturated KCl electrode. The IR spectra are represented as AR/R in the normalized form, where AR=R-R(E ), and R and R(E ) are the reflected intensity measured at a desired potential and a base potential, respectively. 

The majority of experimental powder diffraction patterns in the following five examples were collected using a step scan data collection method on a Scintag XDS2000 system equipped with a Ge(Li) solid-state detector cooled with liquid nitrogen. 

Raman spectra have been obtained with a Jobin Yvon single monochromator equipped with a notch filter and a CCD detector cooled at liquid nitrogen temperature. Raman scattering has been excited through a He-Ne laser (632.8 nm) at low power (6 mW) to avoid heating effects. Spectra have been taken both in situ, that is during and after the deposition in an ultra high vacuum (UHV) chamber, and ex situ after the exposition of the deposited film to atmosphere. 

Because the dark current properties of SPD and MCP-SPD arrays are low and much of the dark current has thermal origins, the dark current can be substantially reduced by detector cooling. Most devices are equipped with Peltier-effect thermoelectric cooling systems coupled to cold liquid coolant systems to achieve temperatures as low as -40 to -80°C in some designs. 

After drifting is completed, the Si(Li) detector is mounted on a cryostat, since the best results are obtained if the detector is operated at a very low temperature. Usually, this temperature is 77K, the temperature of liquid nitrogen. Si(Li) detectors may be stored at room temperature for a short period of time without catastrophic results, but for longer periods it is advisable to keep the detector cooled at all times. The low temperature is necessary to keep the lithium drifting at a frozen stage. At room temperature, the mobility of lithium is such that its continuous diffusion and precipitation will ruin the detector. 

Data collection. Two data sets are used to demonstrate the multiscale cluster analysis method and have been kindly provided by Dr. Roy Goodacre at Institute of Biological Sciences. University of Wales, Aberystwyth [64,65]. Ten microlitre aliquots of bacterial suspensions were evenly applied onto a sand-blasted aluminium plate. Prior to analysis the samples were oven-dried at 50°C for 30 min. Samples were run in triplicate. The FT-IR instrument used was the Bruker IFS28 FT-IR spectrometer (Bruker Spectro-spin, Banner Lane, Coventry, UK) equipped with an MCT (mercury-cadmium-telluride) detector cooled with liquid Ni. The aluminium plate was then loaded onto the motorised stage of a reflectance TLC accessory. The wave-... 

Photon detectors consist of a thin film of semiconductor material, such as lead sulfide, lead telluride, indium antimonide, or germanium doped with copper or mercury, deposited on a nonconducting glass and sealed into an evacuated envelope. Photon flux impinging on the semiconductor increases its conductivity. Lead-sulfide detectors are sensitive to radiation below about 3 fj.m in wavelength and have a response time of about 10 /nsec. Doped germanium detectors cooled to liquid-helium temperatures are sensitive to radiation up to about 120 jitm in wavelength, and have a response time of approximately 1 nsec. 

Fig. 4. Infrared detector cooled by evacuated spot-cooling.

The polymerization reaction was followed in situ by RTIR spectroscopy by using either a dispersive IR spectrophotometer (Perkin Elmer 780) or a Fourier transformed IR spectrophotometer (Brucker IFS 66) equipped with a MCT detector cooled by liquid nitrogen. The time resolution of the dispersive instrument was 100 ms. For the FTIR spectrophotometer, the number of spectra taken per second depends on the spectral resolution and varies between 57 at 4 cm and 100 at 12 cm ... 

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