Wigglers

Wigglers Wijs reagent Wij s solution Wild cherry Wild Musk Wiley melting point... 

Figure 2. Synchrotron X-ray source (schematic). The electrons execute circular motions in the storage ring and emit intense X-rays along the tangent of the orbit. This radiation is enhanced by undulator magnets that are often placed inside the vacuum vessel for enhanced performance. The storage ring has a number of straight sections for undulators and wigglers (not shown).

The circular polarization (CIPO) beamline at the Elettra synchrotron (Trieste, Italy) operates in the VUV-SXR range with radiation from a combination permanent magnet-electromagnetic elliptical wiggler [94, 95]. This does not achieve full circular polarization in the VUV region, but rather an elliptical output with principal axis lying in the horizontal plane (ii > 0, 2 = 0, < 1). 

Unfortunately, in the VUV region no polarimetry data are available, but calculations indicate the degree of circular polarization achieved by the wiggler may be 80%, estimated to be no worse than 70% delivered at the experimental chamber [95, 96]. In PECD experiments, we have calibrated the polarization state by deduction from cross-comparison of results at a few fixed energies previously studied on the SU5 beamline where accurate polarimetry data was available [36]. Because the horizontal magnetic field array in the insertion device is electromagnetic, fast current reversal to switch left- and right-handed elliptical polarizations is possible, with the usual potential benefit for dichroism measurements. 

J. A. Clarke, The science and technology of undulators and wigglers, Oxford series on synchrotron radiation 4. Oxford University Press, Oxford, UK, 2004. 

Hideo Onuki and Pascal Elleaume (eds.). Undulators, Wigglers and Their Applications. Taylor and Francis CRC Press, London, 2003. 

MCP experiments were performed at AR-NE1 station of KEK (National Laboratory of High Energy Physics), Japan, using circularly polarized X-rays with the incident X- ray energy of 60 keV emitted from the elliptical multipole wiggler. Figures 1 and 2 show MCPs ofUSe and UTe, which have been measured at 150 and 80 K, respectively. 

The fact that Ac is proportional to the bending radius is used in so-called insertion devices such as wiggler and undulator magnets.t Although a description of these is beyond the scope of this chapter, the basic principle behind these is to make the electron beam undergo sharp serpentine motions (thereby having a very short radius of curvature). The net effect is to increase the flux and the critical energy (see topmost curve in Fig. 5). 

Figure 5. Photon flux as a function of energy for the Cornell High Ei-chrotron Source (CHESS) operated at various accelerating voltages. The curve is the radiation profile from a 6 pole wiggler magnet. (Figure courted Laboratory for Nuclear Studies at Cornell University.)...

Insertion devices are placed in the electron path of a synchrotron. They increase the photon flux by several orders of magnitude. Similar to the FEL principle they operate by forcing the electrons on a wavy path. At each bend of the path synchrotron light is emitted. In contrast to the FEL device there is no coherence. Instead, the light intensity sums up to form the effective beam. Two kind of insertion devices are used. In wigglers the curvature of the electron path is high. In undulators it is relatively low. 

A completely different emission process, which can in principle provide table-top ultrashort X-ray sources up to 100 keV has been recently discovered and studied, both from an experimental and a theoretical viewpoint [9]. It can be understood as one consider that the electrons, trapped and accelerated in a plasma wake as described earlier, can also experience, in some cases, a transverse force pulling them toward the beam axis. This force is basically due to the creation of a sort of plasma channel at low electron density, which is a consequence of the ponderomotive force that expels the electrons from the laser beam axis (the ions, due to their larger inertia, being fixed). The trapped electrons thus undergo a sort of wiggler motion, thus producing so-called betatron radiation. 

Red wigglers, also called brandling worms or manure worms, are the type most commonly used. They are very efficient recyclers of organic waste and will reproduce quickly in the confines of the bin. It is a good idea to start a worm bin with at least 1,000 worms—about 18 oz (500 g) in weight. They can be extracted from a maturing compost pile, a manure stack, or another worm bin, or they can be purchased by mail order or over the Internet. The dark, moist conditions that worms need to live in can be provided by keeping them in a plastic bin or a wooden box of some form. 

Worms for a worm bin Red wigglers, have a characteristic red-and-yellow banding they are also known as tiger worms. Their eggs are borne in tiny, lemon-shaped cocoons. 

Fiuther progress in time resolved experiments will need increased x-ray intensity and smaller beam sizes, particularly for measurement of the weaker reflections from insect flight muscle. Fortunately, both of these improvements are expected over the next few years from new storage ring sources, from wigglers and undulators and from... 

The X-ray source may be a conventional sealed tube or rotating anode generator or bending magnet synchrotron radiation and more recently the exploitation of multipole insertion devices such as wigglers and undulators represent great gains in source intensity. 

For a full discussion and review of instrumentation employed at SR centres see Helliwell (1984) and the references therein. In order to give an idea of the scale of the apparatus involved Fig. 1 shows a schematic of the optics on the SRS wiggler protein crystallography workstation and a view of the apparatus inside the experimental hutch. 

Another approach to these experiments is also being followed, which involves the use of the full white beam from the SRS wiggler. The geometry of the Laue method is advantageous since a single exposure (Fig. 8) yields 30% of all data to 3 A resolution for the tetragonal crystal form of phosphoryla% and exposure times in the millisecond time scale. 

X-ray Absorption Spectra (XAS). X-ray absorption measurements were performed at station 9.2 of the SRS at Daresbury (UK) with an electron beam energy of 2 GeV and a stored current varying between 290 and 160 mA. The wiggler was operational at 5.0 Tesla. Data were collected in the transmission mode from 11.37 keV to 13.43 keV (Pt Li -edge 11.564 keV, Pt Vedge 13.273 keV) with a Si (220) monochromator detuned to 50 % of the maximum intensity... 

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