MISTRAL
Soft X-ray microscope beamline
The soft X-ray microscopy beamline will be dedicated to transmission full-field imaging of biological thick samples from 270 eV to 2600 eV at cryo-temperature. The goal is to be able to record tomographic data sets in few minutes and 50 nm spatial resolution.
X-ray miscrocopy has shown to provide insight into the internal structure of whole cells. The water window range, between the C (284 eV) and the O (543 eV) absorption edges, is suited for imaging thick biological samples because water layers up to 10 um thick can be penetrated wheras organic cell structures can be visualized with good absorption contrast. Specimens can thus be imaged in their natural hydarted state.
Higher energies will allow the possibility to perform spectroscopic imaging at several interesting edges (such as C, N, O, Ca & S K-edges and Fe, Cu, Mg & P L-edges) for biological, environmental and materials applications as well as to perform phase contrast imaging at 2.6 keV.
Status
Under construction:
1. A first tender exercise for the procurement of the optical components of the beamline was launched in spring 2007. Contracts with companies were signed in summer/automn 2007. The PGM was awarded to FMB, the mirror vessels, slits and WB diagnostic was awarded to Cinel, mirrors to SESO and gratings to Jobin Yvon. Another tender exercise was launched in spring 2008 for the end-station. The cryo-Transmission X-ray Microscope was awared in September 2008 to Xradia.
2. The Plane Grating Monochromator (PGM) from FMB was installed in October 2009 (see picture below). The optics (2 VLS gratings and a plane mirror) were installed in April 2010.
3. Mirror vessels, slits and diagnostics were installed at the beginning of April 2010 by Cinel. Mirrors will be installed the first week of May 2010.
4. The cryo-TXM factory acceptance tests will be done during the first week of June 2010. The installation by Xradia is expected in September 2010.
Staff
Optics: Malcolm Howells
Scientist: Eva Pereiro, Maria Brzhezinskaya
Mechanical Engineer: Daniel Bacescu
Beamline Technician: Ricardo Valcárcel
Software Engineer: Antonio Milán
Beamline Characteristics
Energy range: 270 eV - 2600 eV
Energy resolution: 10 -3
Beam size at sample: 10 um
Technical Description
Polychromatic radiation wil be delivered by a bending magnet. A VLS Plane Grating Monochromator (PGM) will fill with light an elliptical glass capillary, which will, in turn, focus the light on to the sample. The transmitted signal will be collected by an objective Fresnel Zone Plate and a magnified image will be delivered to an X-ray CCD.
The following sketch shows the optical layout of the optics. A Kirkpatrick-Baez system focus ligth vertically (M1) on to the entrance slit (S1) and horizontally (M2) on to the exit slit (S2) of the vertically dispersive PGM. The monochromator will work in standard imaging conditions with a constant slit-to-slit magnification in the dispersive plane of 1/cff = 1/2.25. It is constituted by a plane mirror M3 and two varied line spacing gratings (G), covering the whole energy range. An elliptical cylinder mirror (M4) will refocuse the beam vertically onto the exit slit. The source is demagnified 3 times horizontally and 3*2.25 times vertically at the exit slit position.
The beamline layout including the Transmission X-ray Microscope is shown below:
Documentation
Original proposal of the XRM beamline (2005)
