Background, thermal

Photomultipliers are vacuum tube photocells with a sealed-in set of dynodes. Each successive dynode is kept at a potential difference of 100V o that photoelectrons emitted from the cathode surface are accelerated M each step. The secondary electrons ejected from the last dynode are Collected by the anode and are multiplied so that a 10° — 107 — fold arnpli-t tfion of electron flux is achieved. This allows simple devices such as l croammeters to measure weak light intensities. Background thermal mission can be minimised by cooling the photomultiplier. The schematic... 

Croammeters to measure w eak light intensities. Background thermal fission can be minimised by cooling the photomultiplier. The schematic... 

At very low voltage the injected effective carrier density may be lower than the background thermal carrier density and the current is then ohmic. The voltage at which SCLC begins to dominate is given by,... 

The process of entry is that whereby a radical arising from initiator ultimately becomes a polymerizing macroradical within a latex particle ( background thermal entry is considered elsewhere). At this point, this process is considered in isolation another possible ultimate fate of an initiator-originating radical, namely, forming a new particle, is explicitly excluded (particle formation will be developed later). 

The slit smeared x-ray data was obtained on a Kratky small angle camera and subsequently corrected for parasitic and background (thermal)... 

Comparisons with the limited experimental data available at high density (Kestin Wakeham 1980 Vesovic Wakeham 1991) indicate that the method is capable of predicting the background thermal conductivity of a mixture to within 4%, which is adequate for many practical purposes. 

Q(Af, Ap) is a crossover function which has the value of unity at the critical temperature and density and zero under conditions far removed from the critical conditions. Since the critical enhancement is present in a large range of temperatures and densities around the critical point, it was necessary initially to predict the background thermal conductivity in this range and to subtract this firom the experimental values. The amplitude Rd of the critical enhancement was then determined, and parameters in the equation for the background were adjusted. The equation selected by Basu Sengers (1977) for the crossover function was written in the form... 

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