Noise detector background

A small addition to a logarithmic curve will be very evident at the lower end of the curve and virtually invisible at the top. For good matches with experimental curves plotted on a logarithmic scale (to see small peaks) it is necessary to add a background noise. With a well set up system, this is essentially the detector background, which may be measured at an angle remote from the substrate peak. 

This third scheme maintains favorable collection geometry (360 ) while minimizing detector background noise by electronically rejecting non-coincident photomultiplier pulses. The detectors described in the present work are applicable to both high-energy 0 emitters and 7 emitters. We report here on their application to the detection of 2P-labeled molecules separated by capillary electrophoresis. ... 

A second complication can come from materials that helium can easily permeate such as the elastomers used in O-ring connections. Helium readings from these materials can distract you from other true leak readings. Once an elastomer has become saturated with helium, it slowly desorbs the gas, which creates a large background noise. This background noise interferes with a helium leak detector s sensitivity and performance. All elastomers readily absorb, and slowly desorb, helium. Thus the fewer elastomers used within a system, the less of a problem there will be. Silicone tends to absorb helium the most, followed by nat-... 

The authors have demonstrated that it is possible, by the coincidence technique, to reduce the contribution of noise and background from a PIPS detector by a factor of ten and to improve its energy resolution. Such a detector system could be a useful tool for quality control of low-level, low-energy, pure beta emitters such as Ni from environmental samples. 

Photon counting is insensitive to baseline drift and noise as long as the noise and amplitudes are small compared to the amplitude of the single-photon pulses. Therefore, the signal-to-noise ratio of photon counting techniques follows the law down to the detector background count rate. 

The magnitude of the array readout noise will also severely limit the application of the photodiode array to HFLC fluorescence detection since the fluorescence detector background current 1 Is typically 1000-fold less than that of an absorbance photo-detector... 

Reduced detector background noise (absence of bieed problems that oc-cure with liquid phases)... 

This may significantly reduce noise problems caused by detector noise or background radiation. Furthermore, the large intensity allows new nonlinear spectroscopic techniques such as saturation spectroscopy (Sect.10.2), or multiphoton processes (Sect.10.5), which open new possibilities of studying molecular transitions not accessible to linear spectroscopy. 

The appearance over the last several years of large arrays of low noise detectors is the principal technical driver of our effort to cash in on the low background at the South Pole. Li particular, without the high performance of these arrays it would not be possible to reach the fundamental limit imposed by the low badcground. Also, increasing the number of detectors multiplies the measurement efficiency for many astrophysical problems. Surveys like SPIREX axe particularly susceptible to this multiplex advantage. 

There are important figures of merit (5) that describe the performance of a photodetector. These are responsivity, noise, noise equivalent power, detectivity, and response time (2,6). However, there are several related parameters of measurement, eg, temperature of operation, bias power, spectral response, background photon flux, noise spectra, impedance, and linearity. Operational concerns include detector-element size, uniformity of response, array density, reflabiUty, cooling time, radiation tolerance, vibration and shock resistance, shelf life, availabiUty of arrays, and cost. 

Fig. 3. Ideal photon detector sensitivity as a function of cutoff wavelength. Lower background flux generates less photon-induced noise giving higher sensitivity. The sensitivity limit for the condition of 300 K background temperature and hemispherical (27T) field of view is shown.

The choice of a detector for a specific appHcation should be made in order to minimize the cooling requirements and the magnitude of the background radiation noise therefore, in detector selection the cutoff wavelength should be only slightly greater than that required by the appHcation. If the... 

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