1. General

 

The highflux SAXS beamline at Elettra has been built by the Institute of Biophysics and Nanosystems Research (IBN), Austrian Academy of Sciences, and is now in user operation since September 1996. The beamline was mainly intended for time-resolved studies on fast structural transitions in the sub-millisecond time region in solutions and partly ordered systems with a SAXS-resolution of 1 to 140 nm in real-space. But increasingly also grazing incidence (GISAXS) measurements are performed to study self-assembly processes on surfaces, or to perform structural characterizations of thin films.

The photon source is the 57-pole wiggler whose beam is shared and used simultaneously with a Macromolecular Crystallography beamline. From the very intense wiggler radiation, the SAXS Beamline accepts 3 discrete energies, namely 5.4, 8 and 16 keV (0.077, 0.154, 0.23 nm). The beamline optics consists of a flat, asymmetric-cut double crystal monochromator and a double focusing toroidal mirror.

A versatile SAXS experimental station has been set-up, and an additional wide-angle X-ray scattering (WAXS) detector can monitor simultaneously diffraction patterns. The sample station is mounted movable onto an optical table for optimising the sample detector distance with respect to SAXS resolution and sample size. Besides the foreseen sample surrounding, users have the possibility to install their own specialised sample equipment. In the design phase, besides technical boundary conditions, user friendliness and reliability have been considered as important criteria.

In conclusion, due to the highly variable kept sample stage, there are nearly no limits for the realization of an experiment, and you are welcome by our team to propose any interesting and high-lighting investigation for the benefit of material and life sciences.

 

2. Sample Stage

 

Usually the sample is mounted onto the sample alignment stage which allows the user to place the sample into the beam with a precision of 5µm (resolution: 1µm). The Figure (below) shows the maximum possible dimensions, and alignment range, for a sample holder to be mounted via a base-plate onto our standard alignment stage (left), and dimensions of the base-plate (right). The maximum weight on the sample stage is limited to 10 kg.

In case the envelope dimensions of a sophisticated sample station provided by the users are slightly larger than those given in Fig. 5, the user can ask the beamline responsible for a check up of his space requirements. If it does not fit at all to these specifications, user equipment can also be mounted directly onto the optical table, which allows much larger spatial dimensions.

3. Sample holder

 

As standard equipment for liquid samples Paar capillaries (diameter: 1 and 2 mm) are used thermostated with the KPR (Peltier heating/cooling) sample holders (Anton Paar, Graz, Austria). For use in these sample holders flow through capillaries and Gel holders are standard equipment. Temperature scans can be performed with KPR (-30-70 °C). Typically the precision and the stability of this systems is 0.1 °C. Additionally thermostats for temperature control or cooling proposes can be used at the beamline (-40 - 200 °C). Helium and Nitrogen gas bottles are available at the beamline, for other gases please contact the beamline responsible.
Multiple-sample holders can be mounted onto the standard sample manipulator. At present holders are available for measuring in automatic mode up to 30 solid samples at ambient temperature or up to 4 liquid or gel samples in the temperature range 0 – 95 °C.

4. Online Exhaust System

 

At the experimental station is available a custom-built fume cover and chemical exhaust system for toxic gases. Thus it is possible to e.g. study in-situ chemical reactions, during which toxic gases might develop.

5. Stopped Flow Apparatus

A commercial stopped flow apparatus (manufactured by Bio-Logic, Paris, France), especially designed for Synchrotron Radiation SAXS investigations of conformation changes of proteins, nucleic acids and macromolecules, is available. The instrument consists of a 4-syringe cell with 3 mixer modules manufactured by Bio-Logic. Each syringe is driven independently from the others by an individual stepping-motor, which allows a high versatility of the mixing sequence (flow-rate, flow duration, sequential mixing). For example, injection sequences using one or up to 4 syringes, unequal filling of syringes, variable mixing ratio, reaction intermediate ageing in three- or four-syringe mode etc.. The solution flow can be entirely software-controlled via stepping motors, and can stop in a fraction of a millisecond.
The software allows the set-up of the shot volumes of each of the 4 syringes in a certain time interval. Up to 20 mixing protocols can be programmed. Additionally macros for the repeated execution of individual frames can be defined. Furthermore, the input and output trigger accessible for user operation can be programmed. In the usual operation modus the start of rapid mixing sequence is triggered from our X-ray data-acquisition system (input trigger).
 
After the liquids have been rapidly mixed, they are filled within few ms into a 1 mm quartz capillary - situated in the X-ray beam- , which is thermostated with a water bath. Depending on the diffraction power of the sample time resolutions of up to 10 ms can be obtained.

 

6. Grazing Incidence Small Angle X-ray Scattering

Grazing incidence studies on solid samples, thin film samples or Langmuir-Blodget-films can be performed using a specially designed sample holder, which can be rotated around 2 axes transversal to the beam. Furthermore the sample can be aligned by translating it in both directions transversal to the beam. The precisions are 0.001 deg for the rotations and 5 mm for the translations. Usually the system is set to reflect the beam in the vertical direction. According to the required protocol and the actual assembly of the rotation stages ω, Θ, 2Θ and φ-scans can be performed.

7. Flow-through Cell

 

The flow through cell works in a simple manner: Special quartz capillaries (Glas Technik & Konstruktion, Schönwalde/Berlin) of 1.5 mm diameter and wide openings of about 3 mm at each end, can be inserted into the standard Anton Paar sample holder, which allows various temperature treatments (T-range 25-300 or –30-70 °C, respectively). Thin tubes are connected directly to the capillary ends and a constanst flow is achieved by a peristaltic pump.

8. Temperature Gradient Cell

A temperature gradient cell for X-ray scattering investigations on the thermal behaviour of soft matter manybody-systems, such as in gels, dispersions and solutions, has been developed. Depending on the adjustment of the temperature gradient in the sample, on the focus size of the X-ray beam and on the translational scanning precision an averaged thermal resolution of a few thousands of a degree can be achieved.

9. IR-Laser T-Jump System for Time-Resolved X-ray Scattering

 

The Erbium-Glass Laser available at the SAXS-beamline (Dr. Rapp Optoelektronik, Hamburg, Germany) delivers a maximum of 4 J per 2ms pulse with a wavelength of 1.54 µm
onto the sample. The laser-beam is guided by one prism onto the sample, which is filled in a glass capillary (1 or 2 mm in diameter) and Peltier or electronically thermostated in a metal sample holder (A. Paar, Graz, Austria). With a laser spotsize of maximal 7 mm in diameter a sample-volume of maximal 5.5 µl or 22 µl, respectively, is exposed to the laser-radiation. In a water-solutions/dispersions with an absorption coefficient of A = 6.5 cm-1 T-jumps up to 20°C are possible.

10. High Pressure Cell System 

 

SWAXS measurements of samples under pressure can be performed from 1 to 2500 bar, from 0 to 80 °C in the scattering angle region up to 30 degrees, both in the static or time-resolved mode, e.g. p-jump or p-scan, with a time-resolution down to the ms range. Precise pressure scans of any speed within a broad range (e.g. ca. 1.0 bar/s - 50 bar/s in the case of water as pressurising medium, and a typical sample volume) can be performed. Alternatively, dynamic processes can be studied in pressure-jump relaxation experiments with jump amplitudes up to 2.5 kbar/10ms in both directions (pressurising and depressurising jumps). In most applications diamond windows of 0.75 mm thickness (each) are used. The transmission of one pair (entrance and exit window) is 0.1 at 8 keV, i.e. lower than 0.3, the value for the originally used 1.5 mm thick Be-windows. However the loss in intensity is more than compensated for by the considerably lower background scattering of diamond thus leading to higher q-resolution in the experiments. The sample thickness can be 0.6-4.0 mm, with a volume of approximately 0.5-3 mm3 completely irradiated by the collimated (< 1.0 mm diameter) X-rays. The pressure cell system is flexible and can be built according to the needs of the particular experiment. Normally, a liquid (water, ethanol or octanol) is used as pressurising medium. But in principle, also gaseous media can be employed as well. N2 has been successfully tested, and measurements in supercritical CO2 became frequent. Beside bulk measurements on samples in transmission set-up, also grazing incidence experiments using silicon wafer with highly aligned samples on its surface inserted in the high-pressure cell have been carried out successfully. 

11. Oxford Cryostream Cooler

 

The Cryostream  cooler  creates  a  cold  environment  only  a  few millimeters  from  the  nozzle position. The temperature and the flow of the nitrogen gas stream is controlled and regulated by a Programmable Temperatur Controller based on an 'in stream' heater and a thermo-sensor before it passes out over the sample.  The  system  has  been  especially  developed  for X-ray  crystallography  to  perform  diffraction experiments  on  e.g.  shock  frozen  bio-crystals.  However,  the  programmable  temperature controller allows  further  implication for SAXS-experiments, e.g.,  rapid  temperature drops  in solvents. The design of the Cryostream Cooler facilitates: 

•  Nitrogen stream temperatures from -190 to 100 °C
•  Stability of 0.1 °C,
•  Refill without any disturbance of the temperature at the sample
•  Temperature  ramps  can  be  carried  out  remotely  controlled with  scan  rates  up  6°C/min
•  Individual temperature protocols can be cycled
•  T-jumps  in  both  directions  can  be  performed  by  rapid  transfer  of  the  sample  in  a  pre-
cooled or -heated capillary using an fast syringe driver reaching a minimum temperature
of  -80  °C. Here,  typical  scan  rates are about 15  °C/sec with a  total process  time  in  the
order of 10 sec.
Further information can be found at the webpage: http://www.oxfordcryosystems.co.uk/ 

12. In-line Differential Scanning Calorimeter (DSC)

 

The  in-line micro-calorimeter  built  by  the  group  of Michel Ollivon  (CNRS,  Paris,  France) allows  to  take  simultaneously  time-resolved  synchrotron X-ray Diffraction  as  a  function  of the Temperature (XRDT) and high sensitivity DSC from the same same sample. The  microcalorimetry  and  XRDT  scans  can  be  performed  at  any  heating  rate  comprised between 0.1 and 10 °C/min with a 0.01 °C  temperature resolution  in  the range -30/+130 °C. However, maximum cooling  rates are T dependent and 10°C/min  rates  cannot be  sustained below  30°C  since  cooling  efficiency  is  a  temperature  dependent  process. Microcalorimetry scans  can  be  recorded  independently,  and  also  simultaniously,  of  X-ray  patterns.  The microcalorimeter head can also be used as a  temperature controlled sample-holder for X-ray measurements while not recording a microcalorimetry signal. Isothermal microcalorimetry  is also  possible when  a  time  dependent  thermal  event  such  as meta-stable  state  relaxation  or self-evolving reaction, is expected. The sample capillaries (to be brought by the users !) must have an outer diameter of  exactly 1.50 +/- 0.05 mm, and  a standard length of ca 80 mm.

13. Tension Cell

 

Together with the external user group Schulze-Bauer/Holzapfel the research team constructed a general-purpose tension cell. This particular cell was designed for in-situ tensile testing with the  particular  feature  that  the  sample  could  be  completely  immersed  in  a  solvent  (e.g. physiological  solution), which  is of particular  interest  for  the blood vessel or collagen  fiber testing. The sample container can be attached  to a  thermal bath  to control  the  temperature  in the range from 5 to 95 ºC. A screw with an appropriate opening for the passage of the X-ray beam can adjust  the optical  thickness of  the sample container continuously and optimize  the set-up for different sample geometries.  The fully remote controlled system allows to control not only the fiber extension from 0 to 50 mm, but also it records simultaneously the force signal in the range from 0 to 25 N and as an option  the  optically  determined  Video  extensometer  signal  to  measure  the  transversal contraction of the sample.