What is an SR Beamline

IR emission from Diamond IR bending magnet. From top, simulations by SRW at 2 pm, 10 pm and 100 pm wavelengths. Left 2-D intensity plots. Right linear horizontal intensity traces at the vertical position of maximum bending radiation intensity, namely 9 mm, 20 mm and 40 mm, respectively. The blind region at the centre is due to the first mirror slot of 10 mm vertical size. (Source DLS, Design Report of the IR beamline.) 

The first mirror has to be cooled and may also be partially shielded by an absorber when the beam energy is very high or the distance from the source is short. The second mirror, typically a toroid or an ellipsoid, focuses the radiation on a window that isolates the first section of the beamline, in ultra-high vacuum because of the open connection to the storage ring, from the second section. The early beamlines were equipped with windows made with expensive natural diamonds, type Ila, typically below 2cm in area. Diamond is chosen for its excellent hardness and chemical stability, and for its flat transmittance in the whole IR domain (except for an absorption band at 2000cm i,e, Spm). Nowadays, the availability of large synthetic CVD diamond films makes the use of diamond much simpler. Moreover, synthetic diamond can be 

In spite of the slow start of IR research with SR and the competition of available intense and compact IR conventional sources, the interest in IRSR research and applications is continuously increasing all over the world. 

To summarize, at present an ideal IR source to be used for IR spectroscopy and microspectroscopy is a low emittance, stable low energy storage ring with the highest possible current, possibly working in top-up mode, to perform the most demanding research that is not possible with conventional sources. 

The top-up mode of operation is certainly beneficial for IR spectroscopy in terms of constant photon flux at the samples, but it is questionable for FTIR spectroscopy stability unless coupled to fast orbit feedback for e-orbit. 

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