Technical Description

Key points

  • Energy range 20 < E < 140 KeV
  • Beam sizes from 1 µm to 8 mm

 

Overall layout

The ID15 straight section houses a complex series of beam lines, with two canted branches. This web site is dedicated to the ID15A branch, which houses the materials chemistry (EH3) and materials engineering (EH2) facilities. The ID15B branch houses a high pressure beam line (EH1), which is described elsewhere. The overall layout is shown below:

 

layout.png

X-ray source

ID15A views two insertion devices. One is a compact wiggler source W76, which provides a continuous spectrum up to several hundred keV for materials engineering applications in EH2. The second is currently a U22 undulator, which provides brilliant x-rays in the range 30-140 keV for materials chemistry applications in EH3. In the future (2018), this will be upgraded to a U14 undulator, which  will provide even more brilliant x-rays. As an indication, the spectrum of the U22 with the current lattice, and the U14 with the ESRF-EBS lattice are shown below:

u14.png

 

X-ray optics

For EH2, it is envisioned that the white beam will be shaped by high heat load slits, with a maximum beam size of 8 x 8 mm. Provision has been made for mounting a high-energy monochoromator (in air) at the entrance to the hutch. This can be equipped with Ge crystals for exotic high-energy monochromatic scattering experiments.

For EH3, two monochromators are available. The first is a double multilayer mirror at 40 m from the source in OH1. This provides the highest flux for energies below about 40 keV, at the expense of a band pass of around 0.3 %. The second is a liquid nitrogen cooled double Laue Si monochromator mounted in OH2. This provides excellent flux and tunability over the range 40 - 140 keV, and it is envisioned that it will be used for the majority of experiments. The band pass may be tuned from 0.01 to 0.5 % by bending the crystals.

Several options for x-ray focussing are available for monchromatic beams. So-called 'transfocators', which consist of motorized cartridges of x-ray refractive lenses are employed. To make the best use of the anisotropic x-ray source, vertical and horizontal focusing are carried out using 1D Aluminium annd Berylium lenses at 32 and 53 m respectively. The beam size in EH3 can be tuned down to around 10 microns using these white beam transfocators.

Additional focusing to beam sizes below 10 microns will also be available using further refractive lenses placed at the entrance to EH3 and a KB-mirror system.