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Research Contents > Beamlines > TEMPO > Detailed beamline description > Monochromator

Short description of the monochromator and presentation of the measured resolving power.

The monochromator

The monochromator is composed by three plane gratings and two spherical mirrors. The gratings presents a Variable Line Spacing (VLS) to focus on the exit slits and a Variable Groove Depth (VGD) to optimize total photon flux and harmonic rejection at each photon energy.

The monochormator is then characterized by two optical paths : one for low energy  ranges and the other for high energy ranges. The photon energy intervals are summarized in the table.

Low energy optical path (Mirror A)
Grating  350 t/mm 40/120 eV 
Grating  800 t/mm 95/280 eV 
Grating 1500 t/mm 180/540 ev
High energy optical Path (Mirror B)
Grating 800 t/mm 330/825 eV
Grating 1500 t/mm 620/1500 eV
Alignment procedure

Picture taken during the first monochromator alignemnt. The alignment was carefully verified by Alignment group and Optic group.
Energy Resolution
The resolution tests were performed measuring the ion yield spectra in the energy region close to the resonant 2p excitation of atomic argon as well as the rydberg series of helium and the 1s excitation of molecular nitrogen. The spectra were obtained by monitoring the total number of ions produced in the interaction region between the monochromatic synchrotron radiation beam and an effusive gas jet emanating from a small nozzle. The results obtained for Helium, Argon and Nitrogen are shown in the following panels. In order to extract the Gaussian broadening introduced by the beamline, we have to take into account the intrinsic Lorentzian width of lines.
The resolving power E/ΔE is higher than 10.000 for the three energies.

Nitrogen 1s absorption edge

Ar absorption

He
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