Разработка ионно-плазменной технологической установки для нанесения функционального покрытия на крышки масляных фильтров, страница 13

The big interest represents influence on speed of dispersion of active gases and vapours, containing in residual environment of atomizing chamber after it spilling by vacuum pumps. Nitrogen, oxygen concern to such active components of a residual atmosphere, pairs water, dioxide and monoxide carbon and various hydrocarbons.

Concentration of chemically active gases in the vacuum chamber depends from sorption abilities of a material of a target and the intensity of its dispersion characterized in power density of an ionic current on target.

For the control of the gas environment over the vacuum chamber is widely used the weights-spectrometer method of the analysis.

Weights-spectrometer method of the analysis can be shown to following basic consecutive processes [11]:

1) input of investigated substance in a zone of ionization;

2) transformation of atoms (molecules) of investigated substance in positive (less often in negative) ions;

3) formation of an ionic beam or group of ions;

4) spatial or time division of ions on size of the ratio of weight to the charge;

5) consecutive or simultaneous separate measurement (registration) of ionic beam components.

The basic constructive elements of weights-spectrometer (figure 2.5) - weights-analyzers, a source and the receiver of ions, vacuum system with the device for preparation and input of investigated substance in a source of ions and electronic blocks.

In the ions source ions from atoms (molecules) of investigated substance are created and the ionic beam which acts in the chamber of weights-analyzers where it is divided into the components differing on size of the ratio of weight to the charge is formed. On an output from weights-analyzers ions get in the receiver and are caught by collector. All processes in weights-analyzers, a source and the receiver of ions proceed in conditions of high vacuum, λ > L (λ - free length of molecule, L – the characteristic size of the device).

Figure 2.5. The block diagram of weights-spectrometers (a dotted line denote vacuume part of the device)

In weights-spectrometer devices various types of weights-analyzers which can be divided on static and dynamic are applied. In static weights-analyzers there is a spatial division of ions under the ratio of weight to the charge in constants (quasi-stationary) magnetic or electric field. In dynamic weights-analyzers for division use dependence of speed, resonant frequency of fluctuations or accelerations of ions from size of the ratio of weight to the charge. Dynamic weights-spectrometers can be magnetic and nonmagnetic.

The basic characteristics of weights-spectrometer of devices:

1) The range of measurement on mass numbers characterizes the maximal and minimal value of mass numbers singly ions which can be registered by the device at the certain values of adjustable parameters (an induction of the magnetic field accelerating voltage, frequencies, etc.). At devices for the analysis of organic substances the range of weights exceeds 104 nuclear mass units.

2) One of the major characteristics of weights-spectrometers is its resolution which characterizes an opportunity of separate registration of the ions close on mass numbers. Numerically it is expressed by the ratio of weight of ion M to width of peak in observable spectrum δM, R=M/δM. Generally speaking, size R can depend both from M, and on intensity of an ionic current. Sometimes resolution name value of that greatest weight at which two peaks, differing on weight on unit, are resolved up to the set level. It is considered to be, that weights-spectrometers have low (R <10²), average (R ≈10²÷10³), high (R ≈10³÷10⁴) and very high (R ≈10⁵÷10⁶) resolution.