Exit collimator

A dispersive spectral apparatus contains an entrance collimator, a dispersive element and an exit collimator (for an example discussion, see Refs. [48, 49]). 

The loss of intensity is high in a monochromator equipped with a flat crystal because as much as 99% of the radiation is sufftcienlly divergent to be absorbed in the collimators. Increased intensities, by as much as a factor of 10. have been achieved by using a curved crystal surface that acts not only to diffract but also to focus the divergent beam from the source on the exit collimator. 

Fig. 4-7. Diffraction of a divergent beam from a broad sample by a large crystal. Collimation of this beam requires the Soller slit system shown. This system is equivalent to simple slits at A and B with separators provided to make certain that only parallel rays leave the exit slit.

Fig 4 is a diagram of an electron impact 1 source. The sample vapor is admitted into the ion source thru the slit in the back of the chamber and it passes thru a collimated electron beam b . On impact of electrons with the neutral molecules, positive ions (to a small extent negative ions) are produced. A small positive potential ( repeller potential ) between the back wall V of the ion source and first accelerator plate d , expels tile positive ions toward the accelerating region and at the same time attracts the negative ions which are then discharged at repeller plate c . The positive ions are accelerated by the potential difference applied to plates d and e , pass thru the exit slit T and continue toward the collector... 

For this purpose, the flow tube emptied directly into a high-pressure ion source. This source was essentially a sealed box with a gas inlet for the Cl reagent gas, a 0.58 mm hole to allow injection of a magnetically collimated electron beam, and a 0.99 mm hole to allow ions to exit into the mass spectrometer. The flow tube was coupled to the source using a 0.1 mm annular gap that thermally isolates the source from the flow tube, but allows little of the gas flow to escape. Even at a flow tube temperature of 1000 K, the source temperature increased no more than 50 K. To avoid any variations in source conditions with flow tube temperature, the source was thermostated to a constant temperature of 100 K. 

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