Beams brightness enhancement

Fig. 1.10. The fully electrostatic high-brightness positron beam developed by the Brandeis group. The positron Soa gun is located near B. The beam is deflected at C using a cylindrical mirror analyser and focussed onto a remoderator in chamber D. The extracted beam is then focussed and remoderated at the lower left of D. The double brightness-enhanced beam is then transported into the target chamber, E. Reprinted from Nucl. Instrum. Methods B143, Charlton, Review of Positron Physics, 11-20, copyright 1998, with permission from Elsevier Science.

Mills (1984) pointed out that it might soon be experimentally feasible to realize systems containing positrons which overlapped one with another, both spatially and temporally. This was due to the production of time-focussed beams and the prospects (since demonstrated) for brightness-enhanced, highly focussed beams. 

Fig. 8.6. Schematic of a proposed configuration for the production of conditions for Bose-Einstein condensation of positronium using a pulsed, brightness-enhanced positron beam (see text for details). Reprinted from Physical Review B 49, Platzman and Mills, Possibilities for Bose condensation of positronium, 454-458, copyright 1994 by the American Physical Society.

Mills Jr., A.P. (1980). Brightness enhancement of slow positron beams. Appl. Phys. 23 189-191. 

Brightness enhancement is achieved in positron beams by repeated... 

The most common species used with SIMS sources are Ar+, 02+, 0 , and N2+. These ions and other permanent gas ions are formed easily with high brightness and stability with the hollow cathode duoplasmatron. Ar+ does not enhance the formation of secondary ions but is popular in static SIMS, in which analysis of the undisturbed surface is the goal and no enhancement is necessary. 02+ and 0 both enhance positive secondary ion count rates by formation of surface oxides that serve to increase and control the work function of the surface. 02+ forms a more intense beam than 0 and thus is used preferentially, except in the case of analyzing insulators (see Chapter 11). In some cases the sample surface is flooded with 02 gas for surface control and secondary ion enhancement. An N2+ beam enhances secondary ion formation, but not as well as 02+. It is very useful for profiling and analysis of oxide films on metals, however. It also is less damaging to duoplasmatron hollow cathodes and extends their life by a factor of 5 or more compared to oxygen. 

If sufficient positrons can be confined, studies of particle transport within the plasma, etc., similar to those conducted with electrons can be carried out. It may be possible to use the enhanced detection possibilities afforded since positron-electron annihilations can be detected. An ultra-cold source of positrons would also have a variety of other applications.24 For example, it has been proposed to eject trapped positrons into a plasma as a diagnostic.25 Also, positrons initially in thermal equilibrium at 4.2K within a trap would form a pulsed positron beam of high brightness when accelerated out of the trap. 

The low degree of hard-segment crystallinity in the solvent-cast samples with the added problem of loss of crystallinity from electron-beam damage prevented visualization of either the hard- or soft-segment domains by dark-field microscopy. Therefore bright-field defocus electron microscopy was used to enhance contrast between the microphases (27, 28). Only for the 1/5/4 and 1/6/5 samples was a distinct domain... 

The advent of the high brightness lattice at the SRS in 1985 enhanced the focussed beam intensity by a factor of 3. 

Patterson, D. and Doyle, J.M., Bright, guided molecular beam with hydrodynamic enhancement, J. Chem. Phys., 126, 154307, 2007. 

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