Ion mirror

Figure Bl.7.17. (a) Schematic diagram of a single acceleration zone time-of-flight mass spectrometer, (b) Schematic diagram showing the time focusing of ions with different initial velocities (and hence initial kinetic energies) onto the detector by the use of a reflecting ion mirror, (c) Wiley-McLaren type two stage acceleration zone time-of-flight mass spectrometer.

In (a), a pulse of ions is formed but, for illustration purposes, all with the same m/z value. In (b), the ions have been accelerated but, because they were not all formed in the same space, they are separated in time and velocity, with some ions having more kinetic energy than others. In (c), the ions approach the ion mirror or reflectron, which they then penetrate to different depths, depending on their kinetic energies (d). The ones with greater kinetic energy penetrate furthest. In (e), the ions leave the reflectron and travel on to the detector (f), which they all reach at the same time. The path taken by the ions is indicated by the dotted line in (f). 

By use of an electrostatic ion mirror called a reflectron, arrival times of ions of the same m/z value at the detector can be made more nearly equal. The reflectron improves resolution of m/z values. 

The mass accuracy and resolution of TOF analyzers was improved by the reflectron design in which traveling ions are reflected by an ion mirror and are turned around in their flight paths. 

G. Brinkmalm, P. Hakansson, J. Kjellberg, P. Demirev, B. U. R. Sundqvist, and W. Ens. A Plasma Desorption Time-of-Flight Mass Spectrometer with a Single-Stage Ion Mirror Improved Resolution and Calibration Procedure. Int. J. Mass Spectrom. Ion Proc., 114(1992) 183-207. 

Fig. 11.13. Diagram of a TOF mass analyzer (with reflectron). Ions enter from an external source and are accelerated (orthogonally) by the pusher electrode toward the reflectron. The reflectron (ion mirror) retards, reverses and reaccelerates the ions back toward the micro-channel plate detector.

The reflector or reflectron has been developed by Mamyrin. [35] In the reflector TOF analyzer - often abbreviated ReTOF - the reflector acts as an ion mirror that focuses ions of different kinetic energies in time. Its performance is improved by using two-stage or even multistage reflector designs. 

Ion optics Omega lens single cylinder lens Chicane ion lens 90° reflecting ion mirror... 

Fig. 24. Cartoon demonstrating the effect of the reflectron (ion mirror) on the ions flight path in...

Provided that the initial ion energy distribution is not large with respect to the acceleration potential, a much more common approach is the incorporation of a device known as an ion mirror or re ectron [4,5]. This concept, first introduced... 

Figure 2 Schematic diagram of ion mirror illustrating the reflection of the primary space-...

The reflectron is situated behind the field-free region opposed to the ion source. The detector is positioned on the source side of the ion mirror to capture the arrival of ions after they are reflected. There are two common methods of positioning the detector. It may be coaxial with the initial direction of the ion beam. This detector has a central hole to transmit the ions leaving the source. However, the most common instrument geometry has the detector off-axis with respect to the initial direction of the ion beam. Indeed, adjusting the reflectron at a small angle in respect to the ions leaving the source allows the detector to be positioned adjacent to the ion source. 

Reflection (also known as an ion mirror) a device used in a time-of-flight mass spectrometer that retards and then reverses ion velocities in order to correct for the flight times of ions having the same mass but different kinetic energies... 

The resolution is limited by the length of the flight tube. A longer tube will result in improved separation between ions with different m/z. An ion mirror or reflectron (see below) can be used to double the length of the flight tube without compromising the dimensions of the instrument. 

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