Photoelectric multiplier

EMR Photoelectric Multiplier Phototubes, from EMR Photoelectric, Princeton, New Jersey RCA Photomultiplier TUbes, from local representative or RCA Electronic Components, Harrison, New Jersey... 

EMR Photoelectric Multiplier Phototubes, from EMR Photoelectric, Princeton, New Jersey... 

Optical parametric oscillator, a monochromator, a near-infrared photoelectric multiplier, and a digital oscilloscope. The wavelength of the pulsed laser (X) could be tuned from 410 nm to 2550 nm by the optical parametric oscillation of a BBO ( 3-BaB204) crystal (10). The monochromator is utilized to keep the spectral line width constant because it varies with the wavelength. 

The transmitted output power from the sample is measured by a NIR photoelectric multiplier with a spectral response ranging from 300 nm to 1700 nm, which is cooled to -80°C, through an optical fiber cable. A Si pin-type photodiode is placed near the optical parametric oscillator to generate a trigger signal. The optical fiber cable is directly in contact with the sample. 

Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0% (complete absorption). All methods of detection, whether the human eye or a modern photoelectric transducer, measure the transmittance of electromagnetic radiation. 

In the phosphor-photoelectric detector used as just described, the x-ray quanta strike the phosphor at a rate so great that the quanta of visible light are never resolved they are integrated into a beam of visible light the intensity of which is measured by the multiplier phototube. In the scintillation counters usual in analytical chemistry, on the other hand, individual x-ray quanta can be absorbed by a single crystal highly transparent to light (for example, an alkali halide crystal with thallium as activator), and the resultant visible scintillations can produce an output pulse of electrons from the multiplier phototube. The pulses can be counted as were the pulses-from the proportional counter. 

The photometer is adequately described in Figure 3-2. In the phosphor-photoelectric detector (2.10), the x-ray beam strikes a silver-activated zinc sulfide phosphor to produce blue-violet light that is changed by the multiplier phototube (Type 931-A) into an electric current that is amplified and read on a suitable micro- or milliammeter. A stable power supply for both x-ray tube and detector circuit are essential, as is clear from the circuit diagrams.10... 

Fig. 3-2. A, Phosphor-photoelectric detector B, sample cell C, sample D, CA-5 x-ray tube and housing E, milliammeter F, amplifier and rectifier vacuum tubes G, regulated power supply for amplifier tubes and multiplier phototube H, control panel.

PHOTOELECTRIC CONSTANT. A quantity equal to hje where h is the Planck constant, and e, the electronic charge, and which multiplied by the frequency of any radiation exciting photoemission gives the potential difference corresponding to the quantum energy absorbed by the escaping photoelectron. 

Sommerfeld applied the theory of quanta to the emission of X- and y-rays, to the photoelectric effect, and sketched the theory of the ionization potential. At the beginning of his paper he discussed in some detail the relationship observed in the emission of X- (or y-) rays by cathode (or 0) rays and arrived at the conclusion that large quantities of energy are emitted in shorter times and small quantities of energy in larger times. 9 According to Sommerfeld this empirical result speaks in favor of the central role played in atomic and molecular phenomena by the quantum of action h introduced by Planck, the dimensions of which are energy multiplied by time. 

For the precise and quick measurement of radiant intensities but also of ion currents photoelectric techniques are used almost exclusively. The measurements can easily be automated. The detectors used are photomultipliers, electron multipliers, photodiode array detectors, camera systems and other solid state detectors. 

The decrease for titania occurs at an unexpectedly low dose. The authors note that the copper X-rays should be highly effective for photoelectric ejection of K electrons from titanium, and that the multiply charged ions resulting from the subsequent Auger cascade may be very effective in reducing the surface area, perhaps simply because of the large energy liberation on neutralization. 

Broadband instruments Broadband instruments measure solar irradiance in a specified wavelength range, typically 20 nm to 100 nm wide. This range is defined by the construction of the detector and it results from a combination of different optical elements such as filters and photoelectric sensors. The output signal of broadband instruments corresponds to the integral of the incident irradiance multiplied by the spectral response of the detector. Therefore, any information about the detailed spectral structure of the incident solar radiation is lost. On the other hand, the measurement is instantaneous and thus allows rapid changes in irradiance to be followed, due to fast moving clouds for example. 

The Daly detector uses a photomultiplier rather than an electron multiplier. Ions leaving the analyzer are directed onto a conversion dynode, and the ejected electrons are accelerated onto a plate coated with a fast-acting scintillant. Each electron releases a photon from the scintillant. The photons then enter a photomultiplier tube and impact on a photocathode, producing electrons (photoelectric effect) and initiating an electron cascade (Pigure 2.40). The output from the photomultiplier is further amplified electronically, similarly to the output of dynode type electron multipliers. The level of amplification is similar to that of electron multipliers. Photomultiplier tubes last longer than electron multipliers, but the scintillant-coated plates require replacement every few years. 

For characterization of smoke formation, light absorbance measured by the photoelectric cell is plotted against time. The area under the curve for the specimen is divided by that for the red oak and then multiplied by 100 to obtain a numerical index for the performance of the material in comparison to that of the red oak, regarded arbitrarily as 100 (while the asbestos-cement board represents the zero point of this scale). 

When cool, carefully tap the crucibles to detach the melt pellets, and, without touching the upper surface with the fingers, irradiate with a UV lamp (366 nm) on a matt-black base. Compare the sample and calibration standards visually, or instrumentally, if required, in a reflection fluori-meter (with a photoelectric cell or a secondary electron multiplier fluorescence line at 555.0 nm). The melt pellets may be kept for about 12 hours. 

Formally, the Auger effect can be interpreted as a two-step process first an X-ray photon is emitted, which is then absorbed via photoelectric effect in the same atom. The Auger effect may cause further ionization of a given atom and so multiply ionized atoms can be formed in Auger cascades, especially in high-Z atoms. This, in turn, can cause chemical changes, so the Auger effect has an important role in the mechanism of radiochemical reactions. 

Channel Electron Multiplier (CEM) or channeltron is an electron detector that is used to multiply each electron (up to 10 times) to provide a pulse output suitable for further amplification by conventional electronic circuits. This is a bent tube that is coated with a photoelectric material (of a specific work function) with a high secondary electron coefficient. The tube is kept at a potential of about 2.5 kV. When the electrons pass through the inlet aperture of the CEM and strike the surface of the CEM, a collision of sufficient energy between the ultraviolet radiation and the CEM wall will eject at least one electron. When an electron strikes the mouth of the tube, a number of secondaries is produced that is accelerated in the channeltron. A local electric field created by the bias voltage of the power source accelerates these... 

Photometer, Rgure 1 Photomultipliers are constnjcted from a glass vacuum tube lA/hich houses a photocathode, several dynodes, and an anode. Incident photons strike the photocathode material which is present as a thin deposit on the entry window of the device, with electrons being produced as a consequence of the photoelectric effect. These electrons are directed by the focusing electrode towards the electron multiplier, where electrons are multiplied by the process of secondary emission... 

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