Travelling electrostatic field

Electrostatic analyzer. A velocity-focusing device for producing an electrostatic field perpendicular to the direction of ion travel (usually used in combination with a magnetic analyzer for mass analysis). The effect is to bring to a common focus all ions of a given kinetic energy. 

Ion mobility spectrometry (IMS) [3,12] is the most widely used instrument for drug detection. The sample is heated to vaporize the analyte, which is then ionized by atmospheric (ambient) pressure chemical ionization (APCI) [3]. The resulting gas-phase ions travel through a drift tube and are separated by their distinct velocities (mobilities) in a weak electrostatic field. IMS instruments use ambient air or nitrogen as the carrier gas, making it particularly adaptable to field applications. 

Early theories of the radiolysis of liquid water usefully illustrate two extreme possibilities. Samuel and Magee11 estimated that a 10 eV electron would travel approximately 20 A in 10 13 sec before being thermalised, after which, as it would still be effectively within the electrostatic field of the positive ion, charge neutralisation would take place to give an excited molecule. 

An ion entering an electrostatic field travels in a circular path of radius r such that the centrifugal force is balanced by the electrostatic field strength (E). 

Most energy analyzers are of the type illustrated in Figure 21-4, in which the electron beam is dellected by the electrostatic field of a hemispherical capacitor. The electrons thus travel in a curved path from the lens to the multichannel transducer, I he radius of curvature depends on the kinetic energy of the electrons and the magnitude of the electrostatic field. An entire spec-... 

In this method, acoustic waves are generated by a piezoelectric transducer, which converts an oscillating electric field to a mechanical oscillation. Detection of acoustic waves that have traveled through a polymer specimen is done with the same type of transducer. Depending on its use, a transducer is called a transmitting transducer (transmitter) or receiving transducer (receiver). Common transducer materials are quartz and various polycrystalline ceramics, such as lead zirconate titanate (PZT), polarized in a strong electrostatic field. 

A novel microengineered instrument with a rather different planar electrode layout has been proposed by Muller [3]. Figure Id shows the device, which uses the microwave ion source described earlier and electrostatic filtering. This time, however, mass selection is based on the filtering action provided by the interaction between the ion beam and a three-phase travelling electrical field, which is created by a periodic electrode structure fed by suitably phased drive signals. 

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