Spectrometer

The spectrometer arm consists of two sections, the 7-meter section, equipped with five crystal analysers, and the 12-meter section, designed to host four analysers, and currently equipped with three analysers. They can be coupled together, and therefore provide the capability to record spectra at nine momentum transfers simultaneously. To date, only the 7-meter section was utilised for experiments, whereas the realisation of the 11.5 m crystal analysers is an ongoing research and development project. Figure 1 shows a schematic drawing of the 7-meter spectrometer section and an artists’ view of the whole spectrometer unit. Table below summarises the main characteristics of the spectrometer

Energy[keV]	Reflection order n	Qmax (7 m)[nm-1]	Q (7m)[nm-1]	Qmax (12 m)[nm-1]	Q (12 m)[nm-1]
13.840	7	64	1.89	30.3	1.89
15.817	8	74	2.16	35	2.16
17.794	9	83	2.43	39	2.43
21.747	11	101	3.0	47	3.00
23.725	12	111	3.24	52	3.24
25.704	13	120	3.5	56	3.50

Maximum momentum transfer, Q_max, for the 7- and 12-meter section of the spectrometer arm. Q indicates the Q-spacing between adjacent analysers. If the two sections are utilised simultaneously, The Q-spacing is reduced to half of the indicated value.

Figure 1: Schematic and artists’ view of the 7-meter spectrometer.

The spectrometer arm is positioned on rails on marble tables and the scattering angle is selected by rotating the spectrometer arm via a motorised screw. The vertical axis of rotation is by construction coinciding with the one of the sample goniometer. Figure 2 shows an artists’ view of the 5-Analyser chamber. The momentum transfer resolution is set by motorized slits in front of the crystal analysers.

Figure 2: Artists’ view of the 5-Analyser chamber.