Spectroscopy
Macromolecular
Soft Condensed 
Imaging and
Biological
Magnetic
Structures and
Crystallography 
Spectroscopy 
Andy Dent, former Principal Beamline Scientist on B18
A user from the University of Hull with a sample of metal nanoparticles
B18 being used to study the Tudor warship the Mary Rose
Beamline Specifications
| Energy range (keV) | 2.05 – 35 |
| Energy resolution (Δ E/E) | Si 111: 1.4 x 10-4 (2.05-20 keV) Si 311: 3 x 10-5 (4-35 keV) |
| Flux @ 8 keV at sample (ph/s, Si111) | 5 x 1011 |
| Beam size at sample (µm) | 200 (H) x 250 (V) |
| Beam divergence at sample (mrad) (FWHM) | 1.9 (H) x 0.22 (V) |
The design of B18 is based on three main optical elements: a collimating mirror, a water-cooled double crystal monochromator and a focusing mirror.
The first element is a water-cooled, vertically collimating Si mirror, which is placed at 20 m from the source. It is coated with Cr and Pt stripes and is able to cover the whole energy range from 2 to 35 keV.
The fixed exit double crystal monochromator is water cooled and capable of fast scanning. It has two sets of crystals, Si(111) and Si(311), that can be translated horizontally under vacuum to allow a rapid configuration change.
A double toroidal mirror, coated again with Cr and Pt, is placed at 25 m from the source to focus the two beam branches horizontally and vertically onto the sample. The position of this mirror is also fixed in the vertical and horizontal directions.
Finally, a pair of smaller plane mirrors for harmonics rejection are placed in the Experimental Hutch. They are inserted in the beam path for low energy (<11 keV) operations.
High Energy
The in-air section of the table can be used for experiments between 4 and 35 keV approximately. The sample environments provided for this section include cryostats, furnaces, and a large capacity multiple sample holder system. A flexible experimental space is available for the installation of user designed sample environments (please contact beamline staff for details).
| Detection Methods | |
|---|---|
| Transmission | Ionization chambers for transmission mode measurement and intensity monitoring |
| Fluorescence | A high rate fluorescence 9 element Ge solid state detector system. Portable Vortex detector. |
| XRD | A wide angle detector for simultaneous fast collection of low resolution powder diffraction spectra |
Low Energy
The in-vacuum section is can be used for experiments in the lower energy region, down to approximately 2 keV. A sample manipulator with a capacity of 10 samples and a liquid nitrogen cryostat are available as standard on this section.
| Detection Methods | |
|---|---|
| TEY | Total Electron Yield measurement |
| Fluorescence | A high count rate, multielement Gas Microstrip Detector |
| Fluorescence | Silicon Drift Detector |
The beam source is a Diamond Bending Magnet. B18 Front End will allow the collection of about 3mrad (H) x 0.14 mrad (V) radiation.
| Electron energy | 3 GeV |
| Beam current | 300 mA (w. upgrade to 500 mA) |
| Beam emittance | 2.7 nm.rad |
| Electron beam (rms) dimensions s x, , s y s x’ , s y’ | 53.7 m m, 23.7 m m 81.4 m rad, 2.6 m rad |
| Dipole magnetic field | 1.4 T |
| Dipole bending radius | 7.148 m |
| Critical energy | 8.39 keV |
| Photon flux at 10 keV [ph/sec/mrad/0.1%BW/300mA] | 1.3 x 1013 |
| Brightness at 10 keV [ph/sec/mm2/ mrad2/0.1%BW/300mA] | 3.8 x 1015 |
| Dipole power per horizontal angle | 47.9 W/mrad (80 W/mrad @500mA) |
| On axis power density | 184.4 W/mrad2 (307 W/mraAd2 @500m) |