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Large dynamic range small-angle diffractometer D22

Small-angle scattering is a technique that measures the deviation to small angles (much less than one degree to several degrees) of an X-ray or neutron beam due to structures of small size in the sample. “Small” means dimensions of a few tenths to about 100 nanometres, such as clusters in alloys, polymers, or biological macromolecules.

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Stopped-flow

Stopped-Flow Manual

 

The stopped-flow apparatus is completely controlled by PCby a software called Mps.exe. All the following parameters are given for a standard use. For any unusual use (personnal cell,...) please ask your local contact.

A. Software configuration

All the parameters present in the Config menu have to be correctly defined to ensure the rigth calculation of the flow rate, evolving and dead times.

Device...(If the hard stop is mounted, chose the option Auto)

Syringes...(Define the three syringes as 20 ml/17 mm/4 mm for SFM2, 3 & 4 (std))




 

Cuvette...

Delay Line...(Description of the delay line)




Serial Port...

Limits...




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B. Syringe filling

Syringe initialization
Turn the syringe valves to R. Set the syringes to their uppermost (empty position) manually directly on the MPS module or with the MPS software. When the uppermost position is reached, the motor vibrates with noisy pulses.
On the software, open Syringes Command: Load

Reset individually the syringes by pushing the Reset button or all the syringes with Reset All.

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Manual filling
* Verify that the three syringes are completely empty (upper most position) and that the valves are on position R.
* Attach the syringes containing the sample to the syringe reservoir port on the top of the SFM.
* Select the syringe number on the VMS module. Use the arrow down to fill the syringe.
* Eliminate any bubbles in the SFM syringe by driving it up and down several times while it is connected to the reservoir syringe.
* Turn the syringe valves to C.
* Empty of one or to step the syringe to definitely eliminate the bubbles.
* Repeat all these operations for the to other syringes.

Filling through the MPS software
* Verify that the three syringes are completely empty (upper most position) and that the valves are on position R.
* Attach the syringes containing the sample to the syringe reservoir port on the top of the SFM.
* In the Syringe Command window, select the syringe. Use the arrow down (simple arrow:1 motor step; double arrow:10 motor steps)  to fill the syringe.
* Eliminate any bubbles in the SFM syringe by driving it up and down several times with while it is connected to the reservoir syringe.
* Turn the syringe valves to C.
* Repeat all these operations for the to other syringes.


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C. Sequence file

A sequence file defines to the electronics module different operations such as moving the syringes, sending a trigger, activation of the hard stop...
Open Sequence Files: New for a new file or Sequence Files: Load if the sequence already exists.

 

 

Fill the description of the syringe content:
* Enter the volume of each syringe and the time of the injection. The injection may be repeat several time to ensure a good cleaning of the cell.
* Activate/desactivate the trigger signal (Synchro 1 on/off).

The software calculates:
* The volumes used and the flow rate.
* The dead time related to the cell volume and the evolving time ( or ageing time), in function of the delay line chosen.

 

 Before starting the sequence, check:

 

* The flow rate: 0.045-6 ml/s/syringe
* The minimum flow rate for an efficient mixing: 1 ml/s (total flow rate through each mixer)
* The minimal volume: at least the cell volume.


At this stage, the stopped-flow apparatus is ready for injection. Turn to D22's workstation to prepare the frames.

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D. Standby of D22's workstation waiting for TTL signal

Frames
The acquisition program needs a one-column text file containing the time of each run. The time (in seconds) has to be converted into ticks the electronics time unit (1 tick=90.9 ns). The default file extention is .tic.

* Open the pilot program GEORGE on the workstation to create the frames. Press Setup and chose Kinetics files.


Five options are available. All other suggestions are welcome!

* Constant acquisition time. If the total time is not a multiple of the preset time, the file stops at the closest and lowest value of the total time.

* Geometric series: tn+1=atn=an+1t0, Total time=t0(1-an+1)/(1-a). Again, the file stops at the closest lowest value of the total time.

* Personal choice for time acquisition: do what you want!

* Concatenation of files. Addition of 2 or 3 files already created.

* Reading a file already created and posting on screen the preset times (if you do not remember what you have done...)

Example: Geometric series

Save the file and press do to check your file

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D22's workstation standby, waiting for TTL signal

In the Mad window write the command kin slicename.tic x s/n, return or use the GEORGE dial.
x is the number of repetition, n is no save, s means save.
The VME acquisition card is in a standby mode, waiting for the TTL signal to start the acquisition.
Turn again to the Stopped Flow software.

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E. Running the sequence and starting the acquisition

In the window Stopped Flow Program, select Single or Multiple. The number of possible shots according to the sequence file and the remaining volume of suspensions is calculated.

If READY !!, use the arrow to start the sequence. the black square stops the experiment at any time if necessary.
Single allows only one shot. Close the window Program run to return to the Stopped-Flow Program window. Chose Single or Multiple again to continue with the same sequence files or define another sequence file.
In the Multiple configuration, the arrow execute the sequence file until the Number of shots equals 0.

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F. Data acquisition

The data acquisition starts when the trigger is activated and during the 0 to 5V part of the TTL signal. During the acquisition, the data are directly saved on the acquisition card. This avoids the transfer from the electronics to the workstation and the dead time between two spectra. At the end of the slice file, the spectra are transferred and saved on D22’s workstation.

Real time experiment may creates many thousand of 2D-spectra. It will be maybe necessary to compress the files during the experiment to save place on the Unix station hard disk.
* Open an x-term window
* c(hange)d(irectory) /users/data/
* compress 075* (for example)

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G. Data treatment

The data reduction is really hard work, be patient and rigorous. Further data reduction programs will be developed, in function of the user's needs. Nowadays, the available programs are described in the ILL report “A computing Guide for Small Angle Scattering Experiments”, R.E. Gosh, S. U. Egelhaaf and A.R. Rennie and in the LSS's web pages. Do not hesitate (in a reasonable way!) to ask the help of your local contact.

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H. End of the experiment

Stopped-Flow module cleaning and storage
* Remove the remaining samples and buffer from the syringes.
* Turn the valve to R and fill the three syringes with pure water. Turn the valves to C and empty the syringes to wash the flow lines and the cell.
* Repeat the procedure with ethanol.
* Dry the syringes and flow lines with a wash of air, with the same procedure as described in point 2.
* Turn the valve to R and move the syringes to their lowest position.
* Turn the valve to C and turn off the MSP.

Data storage
The raw data are store both on D22’s hard disk and on a general ILL’s server, under the directory /usr/illdata/data/d22/. They are saved for years under this last path.
The treated data are also saved under your directory on d22sgi for several months. But save your data on zip or CDs before leaving.

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Epilogue

Months or years later…Data are treated and understood. Do not forget when you write your paper that all your results would not have been possible without the beam time allocated by the ILL and the help of your local contact even if he/she has left the ILL.

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