ID10A Beamline Description
Description of the ID10A (Troika I+III) beamline
The ID10A beamline is part of the TROIKA Beamline located at insertion device port ID10. It comprises two experimental stations: TROIKA I and TROIKA III. The undulator source, the Front-End and the Optics-Hutch are common for both beamline branches (ID10A and ID10B).
Schematic Layout
The schematic layout of the TROIKA beamline is shown in Figure 1. The frontend (FE), located 26 m from the insertion device (ID) interfaces the beamline to the storage ring and contains the main beam shutter, a diamond window (300 µm) and beryllium compound refractive lenses (CRL). The first safety hutch (Optics-Hutch) houses the primary slits (PS), a beam diagnostics device (BPM), the TROIKA II monochromator for the ID10B branch , a pair of secondary slits (SS0), a double mirror in vertical reflection geometry and a photon absorber/white beam shutter unit (A/S).The white beam passes in a shielded pipe through the TROIKA II experimental hutch and enters into the TROIKA I experimental station.
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Fig. 1: Schematic layout of the ESRF TROIKA beamline. |
The TROIKA I experimental-hutch contains a secondary slit module (SS1), the multi-crystal monochromator, a thin-wire XBPM and a photon absorber/shutter module (A/S) at the hutch exit. The multi-crystal monochromator is located at 44.2 m from the source and contains four single-bounce (in situ exchangeable) monochromator crystals, all operating in horizontal scattering geometry. A transfer pipe guides the beam into the TROIKA III station, equipeed with a sceondary slit module (SS2) and a Si(111) channel-cut monochromator in horizontal scattering geometry.
The Undulator Source
The beamline uses three undulator segments in series: one 27 mm undulator (U27), one 35 mm undulator (U35), and a revolver unit carrying both U27 and U35 undulators. Hence the source consists of either 2xU27+U35 or 2xU35+U27 depending on the energy requirements. All undulators are installed in series in the ID10 high- straight section. The source size (FWHM) for the 3.9 nm lattice and 1% coupling is 928 µm (horizontal) and 23 µm (vertical). The electron beam divergences are 24 µrad (h) and 9 µrad (v) . The divergence of the photon beam depends on the length of the undulator, the photon energy, the energy spread of the electron beam and the undulator tuning. Typical divergences (FWHM) at 10 keV are 28 µrad (h) and 17 µrad (v) implying a maximum beam size of 2 mm (h) x 0.8 mm (v) at the TROIKA I monochromator position (44.2 m from source). The total emitted power from a single undulator is 1.14/2.05 kW (U27/U35 @ 100 mA) and the maximum power density in the central cone at 27 m distance is 66 W/mm2 for both undulators at 100mA ring current. Figure 2 shows undulator spectra taken with a Si monochromator crystal. The spectra have been corrected for absorption by Be and diamond windows. More details about the UNDULATOR SOURCE
 |
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Fig. 2: Flux spectra of the ID10 undulators tuned to produce 8 keV photons (U27: 1st harmonic, U35: 3rd harmonic). The spectra were recorded with a Si (111) crystal in symmetric Bragg scattering geometry. |
Focussing and Filtering
Focussing in the vertical direction is provided by either beryllium compound refractive lenses (CRL) or by a double mirror system. Two CRL (4x1mm and 3x1mm) are installed in the ID10 frontend. They can provide a 8 keV vertically focussed beam in Troika I (46 m from source) or Troika III (61 m from the source). A double mirror system in vertical reflection geometry (36 m from source) can provide vertical focussing by thermally bending the first of the two mirrors. Both mirrors are separated into three stripes (uncoated Si, Pt-coating and Pd-coating) with critical angles c [mrad]=
(Si, Pt, Pd)/E[keV] and =
(Si)=32,
(Pt)= 84 and
(Pd)=68. The double mirror system is used to supress higher order light and decrease the thermal load on the monochromators downstream. Filtering of the beam can also be achieved by introducing flat mirrors in the monochromatic beam at the individual stations.
The TROIKA I station
The TROIKA I station is equipped with an enegy-tunable multi-crystal monochromator in horizontal scattering geometry operating between 7.5 keV and 20 keV. A multi-task diffractometer with 6-circle capability for high resolution diffraction experiments in horizontal and vertical scattering geometry is placed in the experimental hutch. The instrument can be operated in surface scattering geometries and as a liquid diffractometer. Coherent 8 keV photons are available in a /
=10-4 bandwidth configuration for X-ray photon correlation spectroscopy (XPCS) experiments.
The Troika I Monochromator
TROIKA I is equipped with a UHV MULTI-CRYSTAL SINGLE BOUNCE MONOCHROMATOR operating with three different monochromator crystals: diamond(111), diamond(220), and silicon(111). The crystals are vertically stacked on a common water-cooled multi-crystal mount such that the momentum transfer vectors for all four crystals are parallel. A vertical in-situ translation allows to translate the individual crystals in the horizontal scattering plane and a single tilt motion about a common tilt axis allows to bend the monochromatic beam out of the horizontal plane with tilt angles between +5° (up) and -15° (down). A polished Be window (500 µm) for the monochromatic beam allows scattering angles (2) between 15° and 80° relative to the forward direction in horizontal geometry. This is illustrated in Figures 3a and 3b, showing a top view of the TROIKA I station and a graph displaying the accessible energy ranges for the different monochromator crystals.
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Fig. 3a: Layout of the TROIKA I Experiments hutch. |
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Fig. 3b: The graphs indicate the accessible energy ranges for the available monochromator crystals (Be crystal not available for the moment!). |
Polarization and Coherence Properties
The measured degree of linear horizontal polarization at 9.1 keV is 1.00-0.02 for a 2x2 µrad2 beam and 0.97±0.02 for a 10x10 µrad2 beam. A waveplate assembly operating a diamond crystal in either quarterwave or halfwave mode can allow to produce circular polarization or linear polarization in the verical plane. Partially coherent X-rays can be produced by appropriate collimation and by illuminating collimating pinhole apertures (typical diameter 10 µm at a distance RS=46 m from the source with size dS) with monochromatic X-rays provided by a Si(111) monochromator. A transverse coherence length of RS/2dS ~10 µm and a longitudinal coherence length of
2/2
~1 µm can be achieved for
=1.5 Å. The coherent flux through a 10 µm pinhole is typically 1x109 photons/sec at 100 mA storage ring current. Coherent X-ray beams are routinely used to record static X-ray speckle patterns from disordered materials and for the study of their slow dynamics via X-ray Photon Correlation Spectroscopy (XPCS).
TROIKA I Instrumentation
The TROIKA I station is equipped with a horizontal diffractometer. Figure 4 shows a schematic side view of this instrument (PHOTO HERE). Two horizontal turntables define the scattering angles and a third turntable can either support pathways for the scattered beam or can carry an additional detector assembly. A vertical sample translation stage (stroke 140 mm) allows measurements in which the sample has to be kept in the horizontal plane. The sample stage can either be equipped with an x-y translation assembly and a double tilt stage with a range of ± 20° or an Eulerian cradle providing full four-circle capability. The diffractometer can optionally be equipped with a vertical arm providing a vertical scattering geometry with six-circle capability. The diffractometer is mounted on a platform that can be moved on air-cushions in order to operate at different energies (7.5 keV < E < 20 keV). Reliable operation of the air-pad system is ensured by a leveled epoxy floor that is installed in the monochromator-diffractometer area of the hutch. Movement on a circular path is achieved by connecting the platform to a rotary table mounted underneath the monochromator assembly. The rotary table is mechanically decoupled from the monochromator and alignment between monochromator axis and the rotary table axis is achieved by means of an x-y stage located underneath the rotary table. Energy tuning including movements of the diffractometer and adjustment of the scattering angles (fixed wavevector-transfer mode) is fully computer controlled. The diffractometer can be equipped with a standard displex cryostat (20K), an Orange cryostat (4K), a small angle X-ray scattering (SAXS) chamber or any user instrumentation compatible with the diffractometer sample stage (Huber x-y translation assembly and double tilt stage). The Experiments-Hutch is air-conditioned and provides basic supplies (water, pressurised air, nitrogen/helium flow). A water purifying system is available on request. Simple sample-environment equipment and space for preparation of experiments is available in an adjacent CHEMISTRY LABORATORY.
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Fig. 4: Side view of the TROIKA I diffractometer. |
Data Acquisition and Beamline Control
The present detector environment involves scintillation counters (Bicron and Cyberstar), Avalanche Photo Diode (APD) detectors, and two CCD detectors (availability subject to prior collaboration agreement). The CCDs are both Princeton cameras with 1242 x 1152 pixels and a pixel size of 22.5 µm. One device is a deep depletion detector that is used in direct illumination mode enabling single photon counting in XPCS mode. The other CCD detector is a standard front-illuminated camera having a 1:1 lens system coupled with a thin phosphor screen for standard SAXS applications. The scintillation counters are supported by standard NIM electronics and interfaced into the data acquisition and control system (spec). Digital autocorrelators (correlator.com and ALV) is available for X-ray Photon Correlation Spectroscopy (XPCS) experiments with coherent X-rays. For more information about correlators and detectors we refer to the user guide section about DETECTORS AND CORRELATORS. All beamline and diffractometer motions are achieved via stepping motors. The beamline is controlled with a VME system and supported by UNIX workstations/Linux PCs. Monochromator and diffractometer are controlled via the spec software package interfaced into the VME system. Basic software for data analysis and data transfer is available on the Workstation and on Window based PCs.
Applications
I. Scattering with coherent X-rays
X-ray photon correlation spectroscopy (XPCS) probes the dynamic properties of matter by analyzing the temporal correlations among photons scattered by the studied material. It measures the low frequency dynamics (108 Hz to 10-3 Hz) in a Q range from typically 1x10-3 Å-1 up to several Å-1. It utilizes a partially coherent X-ray beam (E= 8 keV, /
=1.4x10-4, 10x10 µm2 beamsize, 1x109 ph/s/100mA). Experiments are carried out either in SAXS, WAXS or in grazing incidence scattering geometry. Temporal autocorrelation functions are measured by coupling a point detector (typically 100x100 µm2 aperture) to a digital autocorrelator giving fast access to the correlation function over a wide range of correlation times (10-8 sec to 1000 sec) at a single Q value. Aquisition times are typically in the order of 10-60 minutes per correlation function depending on the count-rate. Typical applications are the time-dependence of equilibrium critical fluctuations and the low frequency dynamics in disordered hard (e.g. non-equilibrium dynamics in phase separating alloys or glasses) and soft condensed matter materials, in particular complex fluids (e.g. hydrodynamic modes in concentrated colloidal suspensions, capillary mode dynamics in liquids, layer-fluctuations in membranes and equilibrium dynamics in polymer systems).
II. Surface Diffraction from Solids and Liquids
The X-ray beam can be directed down towards a horizontal surface (incidence angle 0-2 deg.) by a simultaneous tilting of the monochromator and the local mirror installed in the incident flightpath of the diffractometer. This makes studies of liquid surfaces possible. A true 6-circle geometry with the detector mounted on a vertically moving arm (gamma-arm) is available. Combined with the above outlined XPCS technique this allows for the study of liquid surface dynamics. Conventional surface scattering from vertical (solid) surfaces is also possible with the instrument operating in either two- or three-axis horizontal scattering geometry.
III. High resolution diffraction
High resolution diffraction experiments can be carried out in horizontal (or optionally in vertical) scattering geometry between 8 keV and 20 keV. Collimation on the detector side is provided by a set of motorized slits (typically 1 m from the sample). A motorized crystal analyzer stage with either Ge(111) or Si(111) analyzer crystals is available for improoved resolution needs. Magnetic scattering experiments (resonant or non-resonant) are possible in horizontal scattering geometry (incident polarization) and a polarization analyzer permits polarization analysis (-
,
-
channels).
The TROIKA III Station
The TROIKA III end-station is part of the ID10A beamline. It is optimized for scattering experiments with coherent X-ray beams but can also support "white" or "pink" beam experiments. Coherent photons are available in a Δλ/λ=10-4 bandwidth configuration via a silicon (111) channel-cut monochromator for standard XPCS experiments and in the broader "pink" beam mode (8 keV, Δλ/λ=10-2, under development) for SAXS experiments with coherent X-rays.
The general layout of the TROIKA III station is shown in Figure 1. It consists of two independent hutches, a small local optics-hutch and the main Experimental hutch. The first shutter of TROIKA III is located at the end of the TROIKA I station. After this shutter the beam travels through a white beam pipe and enters the local optics-hutch. Here it passes through a secondary slit module (SS2) and impinges on a Si (111) channel-cut monochromator diffracting in the horizontal plane. A shutter (A/S) at the hutch exit separates the Optics hutch from the Experimental hutch. The Experimental hutch hosts the main instrumentation in an almost fixed configuration. The beam is guided to the sample position on the four-circle Huber diffractometer located 60.8 m from the source. In the small-angle scattering configuration the scattered photons, guided by a 3m long flight tube, reach the detector stages located on an optical bench. The general (white) beam-stop marks the end of the TROIKA beamline (ID10A & B) about 66 m from the source.
TROIKA III Optics
The Troika III Optics hutch is equipped with a Si (111) channel-cut monochromator diffracting in the horizontal plane in the range 6-22 keV. It is made out of a silicon monolithic block and is water cooled. A piezoelectric actuator can push on the second Si blade to compensate for the Bragg angle change of the first crystal due to the thermal load. Focussing and filtering can be performed by use of the elements described above in the FOCUSSING AND FILTERING section.
TROIKA III Instrumentation
The TROIKA III instrumentation is organized around two granite tables and a 1.8m long optical bench:
- On the first granite table (Figure 5) a flight path guides the beam to the sample position.
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Fig. 5: TROIKA III 1st granite table. |
It consists of three small X95 profiles clamped on elevators and contains a local absorber unit (elevator z0), a local deflecting mirror (elevator z1) and a pair of slits (elevator z2). The settings of the slit is controlled by four motors jjhg (horizontal gap), jjho (horizontal offset), jjvg (vertical gap), jjvo (vertical offset). The assembly is evacuated and connected without any windows to the monochromator vessel. An additional x-z translation (motornames fx and fz) unit can be mounted externally on the last X95 element on the z2 elevator to install a set of pinholes close to the sample when a coherent beam is needed. The translations xtf and xtb can move/rotate the flight path in the horizontal plane up to 200mm/5°. - On the second granite table (Figure 6) a four-circle Huber diffractometer in horizontal scattering geometry is located.
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Fig. 6: TROIKA III diffractometer. |
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Fig. 7: The optical table carrying the detector assembly at TROIKA III. |
It hosts two elevators (zbicron and zccd) carrying a point detector and a CCD device on the horizontal translation xdet and a third x-z unit (xpipe, zpipe) able to hold an evacuated 3 m long flight tube. At the inner side of the exit window of the flight tube a tantalum beam-stop can be inserted to block the direct beam. It can be mounted in vertical, horizontal and 45° position and translate in the radial direction (motor bst). The optical table can be moved by a compressed air pads system. The Experimental hutch is air-conditioned and provides basic supplies (water, pressurized air, nitrogen gas, low-flow extraction). Simple sample-environment equipment and space for preparation of experiments is available in an adjacent laboratory.
Technical Information (TROIKA I & III)
| scientist in charge | Anders Madsen tel:+33 (0)4 76 88 23 57, fax: +33 (0)4 76 88 21 60, Email |
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| scientific applications | Originally conceived as a so-called open undulator beamline; now optimized for scattering with partially coherent X-ray beams (7-20keV) and X-ray Photon Correlation Spectroscopy (XPCS) | |||||||||
| source parameters | high  straight section; three undulator segments in series: U27, U35 and a U27/U35 revolver unit. |
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| U27 undulator | U35 undulator | |||||||||
 u |
27 mm | 35 mm | ||||||||
| Kmax | 5.0 | 6.5 | ||||||||
| field Bmax | 2 T | 2 T | ||||||||
| source size | 928 x 23 µm2 (HxV) FWHM | |||||||||
| source divergence | 28 x 17 µrad2 (HxV) FWHM @ 10keV | |||||||||
| peak brilliance | > 1020 ph s-1mrad-2mm-2 (0.1% bw, 100 mA @ 8 keV) | |||||||||
| power | 1.14/2.05 kW @ 100mA ring current (single U27/U35) | |||||||||
| power density | 66 W mm-2 (single U27 or U35) @ 27 m distance from source and 100 mA ring current | |||||||||
| optics | PS | SS0 | Mirror | SS1 | monoI | SS2 | monoIII | |||
| distance from source [m]: | 27 | 33 | 36 | 43 | 44.2 | 55.7 | 56.8 | |||
| focusing: | 2 Be CRL @ 24 m from source (FE) for vertical focussing in Troika and Troika III (8keV) | |||||||||
| beam size at sample: | max. 2 x 0.8 mm2, min. 10 x 10 µm2 (HxV) | |||||||||
intrinsic resolution  E/E: |
5.9 x 10-5 diamond (111), 2.3 x 10-5 diamond (220), 5 x 10-4 beryllium (002), 1.4 x 10-4 silicon (111) | |||||||||
| flux at sample: | About 5 x 10 13 ph/s/mm2 (8 keV) depending on the monochromator crystal chosen | |||||||||
| detectors | scintillation counters, APD detectors, CCD detectors (availability subject to prior collaboration agreement) | |||||||||
| beamline control | UNIX Workstation, Linux PC, SPEC control software | |||||||||
| ancillary equipment | SAXS chamber, displex cryostat, polarisation analyser, autocorrelator etc. | |||||||||
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