Applications of the Radiation from Fast Electron Beams

Motz, H.

doi:10.1063/1.1700002

Cited by 449 publications

(108 citation statements)

References 2 publications

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“…It measures the number of photons per unit time, per photon source area, per source solid angle and for a certain bandwidth (BW), given in the units photons (mm 2 mrad 2 s 0.1%BW) À1 . At present, the highest spectral brightness is achieved by special magnetically periodic insertion devices called undulators (Motz, 1951;Clark, 2004). In these devices the particle beams are forced on a slalom course by a sequence of differently poled magnets.…”

Section: Basics Of the Generation Of Srmentioning

confidence: 99%

The potential of future light sources to explore the structure and function of matter

Weckert¹

2014

Acta Cryst Sect A

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Structural studies in general, and crystallography in particular, have benefited and still do benefit dramatically from the use of synchrotron radiation. Lowemittance storage rings of the third generation provide focused beams down to the micrometre range that are sufficiently intense for the investigation of weakly scattering crystals down to the size of several micrometres. Even though the coherent fraction of these sources is below 1%, a number of new imaging techniques have been developed to exploit the partially coherent radiation. However, many techniques in nanoscience are limited by this rather small coherent fraction. On the one hand, this restriction limits the ability to study the structure and dynamics of non-crystalline materials by methods that depend on the coherence properties of the beam, like coherent diffractive imaging and X-ray correlation spectroscopy. On the other hand, the flux in an ultra-small diffraction-limited focus is limited as well for the same reason. Meanwhile, new storage rings with more advanced lattice designs are under construction or under consideration, which will have significantly smaller emittances. These sources are targeted towards the diffraction limit in the X-ray regime and will provide roughly one to two orders of magnitude higher spectral brightness and coherence. They will be especially suited to experiments exploiting the coherence properties of the beams and to ultra-small focal spot sizes in the regime of several nanometres. Although the length of individual X-ray pulses at a storage-ring source is of the order of 100 ps, which is sufficiently short to track structural changes of larger groups, faster processes as they occur during vision or photosynthesis, for example, are not accessible in all details under these conditions. Linear accelerator (linac) driven free-electron laser (FEL) sources with extremely short and intense pulses of very high coherence circumvent some of the limitations of present-day storage-ring sources. It has been demonstrated that their individual pulses are short enough to outrun radiation damage for single-pulse exposures. These ultra-short pulses also enable time-resolved studies 1000 times faster than at standard storage-ring sources. Developments are ongoing at various places for a totally new type of X-ray source combining a linac with a storage ring. These energy-recovery linacs promise to provide pulses almost as short as a FEL, with brilliances and multi-user capabilities comparable with a diffraction-limited storage ring. Altogether, these new X-ray source developments will provide smaller and more intense X-ray beams with a considerably higher coherent fraction, enabling a broad spectrum of new techniques for studying the structure of crystalline and non-crystalline states of matter at atomic length scales. In addition, the short X-ray pulses of FELs will enable the study of fast atomic dynamics and non-equilibrium states of matter.

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Section: Basics Of the Generation Of Srmentioning

confidence: 99%

The potential of future light sources to explore the structure and function of matter

Weckert¹

2014

Acta Cryst Sect A

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“…(1), (2), (4), (6), and (10) - (14). Moreover, the vector potential for the equilibrium magnetic field is approximated by Eq.…”

Section: A Basic Assumptionsmentioning

confidence: 99%

Theory of free electron laser instability in a relativistic annular electron beam

Uhm

1981

The Physics of Fluids

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A self-consistent theory of the free electron laser instability is developed for a hollow electron beam propagating through an undulator (multiple mirror) magnetic field. The stability analysis is carried out within the framework of the linearized Vlasov–Maxwell equations. It is assumed that the beam is thin, with radial thickness much smaller than the mean beam radius, and that ν/γb≪1, where ν is Budker’s parameter and γbmc2 is the characteristic energy of the electron beam. The dispersion relation describing the free electron laser instability in a hollow relativistic electron beam is obtained for an equilibrium distribution function in which all electrons have the same value of transverse energy and the same value of canonical angular momentum, and a Lorentzian distribution in axial momentum. It is shown that the influence of finite radial geometry plays a critical role in determining the detailed stability behavior. Moreover, the growth rate and bandwidth of the instability can be expressed in terms of Budker’s parameter ν, instead of the plasma frequency as in the case of a uniform density beam. Furthermore, it is found that free electron laser stability properties exhibit a sensitive dependence on axial momentum spread.

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“…0-m and o E -q g N z =0 (11) for the transverse and longitudinal components, respectively. Substituting the electric field components from Eqs.…”

Section: +=E X+ Ie Y(8)mentioning

confidence: 99%

Resonant Interaction Between an Active Molecular Medium and a Free Electron Laser

Wilhelmsson¹

1980

Phys. Scr.

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The system of a relativistic electron beam and an active molecular (maser) medium in the presence of a ripple magnetic field is studied theoretically. The tunability of the free electron laser could be used to reach different lines of such a molecular medium. We use a Lorentz model to describe the molecular transitions, a hydromagnetic model for the beam, and formulate the resonance condition for the two cases where (i) the coupling occurs at a common interface, e.g., cylindrical, between the beam and the molecular medium, and (ii) the beam and the molecules fill the same volume in space.The coupling between the beam and the molecules offers possibilities of enhanced radiation and improved coherence. In the case where the free electron laser acts as a pump of the molecules stimulated radiation could in principle be obtained at a new wavelength, i.e., the coupled system acts as a frequency transformer.

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Applications of the Radiation from Fast Electron Beams

Cited by 449 publications

References 2 publications

The potential of future light sources to explore the structure and function of matter

The potential of future light sources to explore the structure and function of matter

Theory of free electron laser instability in a relativistic annular electron beam

Resonant Interaction Between an Active Molecular Medium and a Free Electron Laser

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