GILDA Beamline Handbook

The GILDA control room

INDEX

1. General Instructions for EXAFS users on the GILDA beamline

2. Front end operations

3. SECONDARY SHUTTERS operation

4. Programs for EXAFS acquisition

4.1 VACUUM OPERATIONS

4.1.1 Moving the sample

4.2 Program Setenergy

4.3 Program EXAFS_SCAN_SETUP

4.4 The Multielement Ge detector

4.4.1 General_setup

4.4.2 4_ch_standalone

5. PROCEDURE TO TRANSFER FILES AT HOME

6. TROUBLESHOOTING

1. General Instructions for EXAFS users on the GILDA beamline

Dear User

We are pleased to welcome you to the GILDA beamline!

Here you find a brief guide to successfully perform EXAFS experiments. Here we recall the main operations you will be requested to do with the references to programs you need:

1) Open/close the Front-end

See 'Front-end operations' section

2) Open/close the EXAFS beam shutter

See 'Secondary shutters' section

3) Perform all the 'vacuum' operations to put the samples in the measure chamber.

See ‘Vacuum operations’

4) Put the sample on the beam

See program 'Sample_holder'

5) Detectors set-up and beam conditioning

See section dedicated to program 'Setenergy'. If you are using the 7 (or 13) elements Ge detector see also the instructions for programs 'DXP_General_Setup' and '4_channel_spectra_standalone'.

6) Get the spectra

Have a glance to the 'EXAFS_scan' program guide.

Your Local Contact will perform for you the main initial beam conditioning so you will have just to put the sample on and make the measurement. Minor changes of the Beamline setup (absorption edge, Ge detector setup, ..) can also be easily performed by the user if the Local Contact agrees. If anything unusual happens note it in the beamline notebook and contact him.

2. Front end operations

Front-end operations are performed from the X-terminal numbered '1'. Before performing this procedure, please be sure that the optic hutch is correctly searched. In case of failure of these instructions call the floor coordinator (ext. 2525) for prompt rescue.

• If the terminal is off or in case of a network failure

1) switch on the terminal

2) When requested input the login parameters:

username= opd08

password= tonic08

3) when the x-session is active click on the left button of the mouse: a menu is highlighted. Choose 'id-appli' and release the button: the application will start.

4) Click on the 'Open front end' button (always moving the arrow with the mouse and pressing the left button) and the front-end will open. To close, click on 'Stop Beam'. Caveat: the front end is automatically closed at each injection: remember to re-open it after getting the message 'Back to USM'.

• If the application is yet active

see point 4 above

3. SECONDARY SHUTTERS OPERATION

All the operations involving secondary shutters (and vacuum valves in the various hutches) are performed from the terminal numbered '2'. A table is shown in the terminal where for each hutch are listed the device names and the realtive current status. An error window indicates occurring failures. If you get here a repeated error message please, call the Local Contact.

To get into the EXAFS hutch or to put the beam in the hutch the user has to close or open the shutter 'B1' between the optic hutch and the EXAFS hutch. To do so, follow this procedure:

1) Press the spacebar.

2) At the prompt 'Hutch number' tape the shortcut B1. The command acts to invert the current status of the device (opens if previously closed and vice-versa ).

3) Check if the status has really changed in the table on the terminal.

1) Press spacebar

2) You will get the prompt 'Hutch number'. Input the number of the hutch where you want to act accordingly to the following table:

3) Yo will get the prompt 'Command'. The commands are listed in the first column of the table shown in the terminal. Generally Vx means x-th valve, Bx is the x-th beam shutter. The command acts to invert the current status of the device (opens if previously closed and vice-versa ). Valve numbers are sticked on the valves in optic hutch, whereas the only valve in hutch #2 is numbered 1. Valves in other hutches are non-existent.

4) Check if the status has really changed in the table on the terminal.

4. Programs for acquisition

Programs for acquisitions are run from the MacIntosh numbered 3 and the PC #5 (Vacuum operations). For preliminary data analysis you can use the macintosh numbered 4 or the PC in the terminal room. In both cases you have to fetch the data from macintosh number 3 (ritasun1.esrf.fr, username=gilda , password=grenoble) and put them in a personal folder. Consult the beamline logbook or ask the Local Contact for the complete path.

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W A R N I N G

Macintosh '3' and PC ‘5’ are to be used for acquisition programs only. Running analysis programs, web browsers, games, cd-player and so on is strictly forbidden on this machine. The interaction of these programs with the acquisition software can result in a scan abort and consequent 'S.O.S cry' to the local contact.

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4.1 VACUUM OPERATIONS

Please, refer to the manual on the beamline

4.1.1 Program Sampleholder

Action: Moves the sample holder mounted on the liquid N2 cryostat. Vertical Movement: for lower values the sample raises; accepted positions are between 1 and 96 mm. Horizontal Movement: lower values correspond to the sample towards the machine wall. You can also make a scan and register the readout of a given detector (scan menu) to choose the good position of the sample to make the measurement.

Procedure so set a sample position

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1) Push the white arrow in the top left side to launch the program. The arrow becomes black indicating that the program is running.

2) Choose the motor you want to move in the ‘Choose Sample Holder’ menu.

3) Click the ‘Get position’ field to look the actual position

3a) Check that the "Motion Type’ boolean is on "Absolute’ mode

4) Put the new position in the ‘Set position’ field. If you want to know the acceptable values click the ‘Get Limits’ field before !

5) Click ‘Move Motor’

4) At th end of the operation the new position is loaded in the ‘Current Position’ field.

5) Push ‘Exit’ to exit the program

Procedure to center a sample on the beam

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1) Push the white arrow (if yet black skip this point) in the top left side to launch the program. The arrow becomes black indicating that the program is running.

2) Be sure that you are getting beam on the sample. You must have proviously run ‘Setenergy’ and the beam must be present on the oscilloscope (See ‘Setenergy’ section at this purpose)

3) Choose the motor you want to move in the ‘Choose Sample Holder’ menu.

4) Load the initial position in the ‘Lower limit’ field

5) load the final position in th ‘Upper limit field’

6) Input the step: possibly no coarser than 1/10 of the chosen range, no finer than 0.1 mm.

7) Input integration time and wait time: default values of 0.2s are OK.

8) Choose the detector you want to read in the ‘Counter type’ field. Usually used detectors are ‘I1’ (transmission mode) or ‘DXP Ch #7’ (Fluorescence mode). In the latter case be sure that suitable cursors have been set for the channel #7 of the multidetector. Refer to the 4_ch_standalone programs for details. For other detectors please ask to the Local Contact.

9) Change the default file-name if you wish to keep this file

10) Click ‘Start scan’: counts (or volts) as a function of the sample holder position are displayed in the plot. Note that (especially for horizontal scans) the motion is extremely slow !!

11) At the end you can place the cursor(s) on the plot and choose the central part of the picture. The n-th cursor x-value is displayed in the field on the right of the ‘Cursor n’ indicator.

5) Push ‘Exit’ to exit the program

Caveat

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This program is not compatible with the other programs. Be sure to exit before using other applications.

4.2 Program Setenergy

Action: Moves the monochromator to supply a beam at desired energy and intensity. Also plots of the reflectivity curve of the crystals

Procedure so set an energy at a desired output intensity (duty-point):

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-------------- a) With a curved crystal------------------

0) Push the white arrow in the top left side to launch the program. The arrow becomes black indicating that the program is running.

1) Check the state of the following boolean variables (and change if different)

2) Input the desired energy in the 'energy' field. Default is the current energy.

3) Input the desired output intensity in the 'duty-point' field. For a discussion on this topic see appendix A. However the Local Contact will always advice you on the correct value to use.

4) Input the rocking curve side (positive or negative derivative) to use. Again see appendix A and follow the Local Contact instructions.

5) Push 'Go'. Normally a spot on the oscilloscope should start to 'float' on the screen, its y voltage value corresponding to the duty-point. This means that the beam has been found and the desired duty-pointis set. In case of fail the program will automatically look for the beam in a limited angle range. This routine will last few minutes. In case of a further fail consult the 'troubleshooting' section or call the Local Contact.

--------------------- b) With a flat crystal-------------------

0) Push the white arrow in the top left side to launch the program. The arrow becomes black indicating that the program is running.

1) Check the state of the following boolean variables (and change if different)

2) Input the desired energy in the 'energy' field. Default is the current energy.

3) Input the desired output intensity in the 'duty-point' field. For a discussion on this topic see appendix A. However the Local Contact will always advice you on the correct value to use.

4) Input the rocking curve side (positive or negative derivative) to use. Again see appendix A and follow the Local Contact instructions.

5) Push 'Go'. Normally a spot on the oscilloscope should start to 'float' on the screen, its y voltage value corresponding to the duty-point. This means that the beam has been found and the desired duty-pointis set. In case of fail the program will automatically look for the beam in a limited angle range. This routine will last few minutes. In case of a further fail consult the 'troubleshooting' section or call the Local Contact.

Procedure obtain a plot of the rocking curve and optimum duty-point choice:

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First of all you must be sure that the beam is in the piezo range. To do so you can run a search of the Rocking-curve with duty-point of 0.1V first on the 'Positive derivative' side and the on the 'Negative derivative' side. Note that the curve will ba saved on a file.

-------------- a) With a curved crystal------------------

0) Push the white arrow in the top left side to launch the program. The arrow becomes black indicating that the program is running.

1) Check the state of the following boolean variables (and change if different)

2) Input the piezo scan parameters in the dedicated fields. Default values are normally OK. If you want to keep the scan input also a suitable file name

3) Clik 'Go'. The plot will appear in the window. For an EXAFS scan typical duty-point values are 70-80% of the maximum of the curve.

-------------- b) With a flat crystal------------------

0) Push the white arrow in the top left side to launch the program. The arrow becomes black indicating that the program is running.

1) Check the state of the following boolean variables (and change if different)

2) Input the piezo scan parameters (min and max voltage, step, integration time and file name) in the dedicated fields. Default values are normally OK. If you want to keep the scan input also a suitable file name

3) Click 'Go'and the plot will progressively appear in the window. For an EXAFS scan typical duty-point values are 70-80% of the maximum of the curve.

When you have finished click the 'QUIT' button to stop the program. Caveat: this program cannot run together with 'Exafs_Scan_setup' and other programs otherwise an alert message will be displayed.

4.3 Program EXAFS_SCAN_SETUP

ACTION: It loads the EXAFS scan parameters, executes the measurements and saves on file.

How to use it:

1) Launch the application from the 'launcher' on the desktop

2) CLick the white arrow om the top left side of the 'Labwiew window'

3) enter the energy intervals of the spectrum

4) enter the corresponding enegy step widths

5) enter the corresponding integration times

*********CAVEAT **********

This routine is not fool-proof. If the number of intervals does not corresponds to an identical number of steps or integration times the program could behave in an unpredictable way !!

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6) enter the wait time after motor positioning before starting the acquisition. Usally it must be set at least 3 times the amplifier rising time. Ask your local contact for details. 1s is OK for all situations.

7) Enter the initial and final duty-point.

8) Choose the working Roching curve side. Usually set to 'Ascending'.

9) Enter the number of scans to be performed on that sample. The program updates automatically the file name for each scan.

10) Check that 'Backlash’ correction is set to 'Yes'

11) Dynamical focusing: set 'Yes' if you are working with a curved crystal, 'No' if you are working with a flat crystal. In case of doubt ask your local contact !

12) Enter the file name. This will be a prefix to which the program adds 01, 02, ... depending on the number of scans you have chosen in point 9.

13) Choose the scan type: the most common modes are 'Absorption' (for measurements in transmission mode) or 'Multidetector Digital XP' (for fluorescence mode). In the latter case be sure to have properly initialized the Multidetector before launching the scan (See DXP_General_Setup.vi and DXP_4Ch_spectra_standalone.vi)

14) Click on the button 'Apply scan data' Now the scan parameters are loaded in a file. If you realize that something in not correct you can change the wrong field as many times as desired. But remember to click 'Apply scan data' after each change !

15) Click 'Execute scan' to start the scan.

4.4 The Multielement Ge detector

The 7 (13 very soon) High Purity Germanium detector is used for the collection of high quality fluorescence spectra. The signals from the built-in preamplifiers are fed to the Digital X-ray Processor (DXP) that performs the pulse amplitude analysis and spectrum integration. Two programs are used for the set-up pf the detector:

- General_setup to load general parameters

- 4_ch_standalone to load experiment-specific parameters.

Here we give an operative description ofthe two appications.

Caveat: These two programs need a 'server' running on 'ritamac' machine. If the server is not active connection errors are displayed when trying to run these applications.

4.4.1 General_setup

Action: Initialization and loading of very general setup parameters of Digital X-ray Processor (DXP).

Procedure:

1) Choose the 'peaking' time of the detector with the pop-up menu. Default value is 1µs; for an extensive description of this parameter please refer to the 'XIA DXP Manual' available on the beamline. Very roughly the peaking time is a measure of the time of pulse analysis just like the 'shaping time' on a conventional analogic amplifier. Longer peaking times lead to better energy resolution but the maximum count rate is limited. As a rule of thumb for 20000 cps (total count) the maximum peaking time for a good detector linearity is 1µs. The max peaking time scales linearly with the count rate(4µs for 5000 cps and so on).

2) Insert the energy of the fluorescence line in the 'Fluorescence Energy' field. Clearly this parameter depends on your sample and the fluorescence energies can be found in the 'X-ray Data booklet' available on the beamline.

3) Insert the desired pulse amplitude (in mV) at the input of the ADC converter of the DXP. The default value (100 mV) is generally OK.

4) Press the white arrow. The parameter loading takes a few minutes so please wait the ‘DONE" boolean become green.

4.4.2 4_ch_standalone

Action: Provides the energy spectrum of the fluorescence signal and the total count-rate. It performs also the integration of the spectrum between the limits chosen by the user (CURSORS). As the DXP electronics consists in cards of 4 amplifiers each, this program deals with a single card at a time. The setup has to be repeated then for all the cards in the system. A 7 element detector uses 2 cards, whereas 4 cards are needed for the 13 elements detector. The Local Contact will inform you on the system presently running.

Procedure:

Before performing this procedure be sure that an X-ray beam with an energy above the absorption edge of interest is present on the sample. Use an energy ‰50-100 eV above the edge to safely separate the 'elastic' from the 'fluorescence' peak. For energy setting refer to the program 'Setenergy' on this manual.

0) CLick the white arrow om the top left side of the 'Labwiew window'

1) Input the integration time (1s is OK for most cases) in the corresponding field.

2) Input the number of the card you want to use. Cards are numbered from 0 to 3.

3) Inhibit the readout of unused channels by clicking the corresponding booleans. Default is 'all channels read' presented as 'XXXX': see table below for the correct settings of all cards:

After the first check on point 4) badly behaving channels (showing a much worser energy resolution than the others, collecting no counts, ...) must be inhibited in addition to those indicated.

Caveat: Allowing the reading of unused (or bad) channels can lead to fatal runtime errors when collecting the spectrum needing a new startup of the detector.

4) Click on the ‘Execute and DO NOT SAVE CURSORS’ button to collect the spectrum of the 4 channels of the card. Now you can expand each spectrum window and place the CURSORS sidewise the fluorescence line of interest (Cursor 0 at lower energies). The pulses between the cursors will be integrated and displayed (divided by the integration time) in successive acquisitions in the 'Slow peak' field. The 'Fast peaks' field shows the total count rate: check if the current shaping time is suited for your experimental conditions.

You have to repeat the CURSOR positioning for all the channels read on the card. For instructions on window zooming and cursors on 'labview' plots take a glance to the 'Labview plots' section of this manual. Remember that cursors should be placed in zones of zero derivative (Pulses/Energy) to minimize the effects of slow drifts of the pulse analyzer.

5) Click the ‘Exacute and save cursors’ button to collect the final spectrum. Now the cursor positions are loaded in a configuration file as well as the channels to be read. This configuration file will be used by the sample alignment program or by the acquisition program.

Caveat: Each spectrum acquisition leads to an automatic cursor position saving on the file. NEVER leave the program after an acquisition with ill-positioned cursors otherwise bad data will be collected by the concerned card.

6) Repeat points 2-5 for all the cards of the system.

7) if you want to check the position of the cursors proceed as follows

7a) Choose a card

7b) Collect a spectrum without saving the cursors

7c) Click on the ‘Refresh cursors’ button. Now the previously cursors loaded for that card are shown on the plots.

5. PROCEDURE TO TRANSFER FILES AT HOME

To do this you must have an account (username=yourname, password=yourpassword) on an external machine (yourmachine). To transfer the data you have just taken on the beamline folow the procedure:

1) open ‘Versaterm FTP client’ in he ‘Network’ menu of the launcher

2) Double click on ‘OUT"

3) In the ‘username’ field load yourname@yourmachine

4) In the password field load yourpassword

5) Check that the transmission mode is TEXT/ASCII.

6) press ‘send’

7) select your directory (see the logbook in case of doubt) in the left field

8) press ‘apple’-A to select all files

9) press ‘apple’-S to send files

10) Click ‘Done’

11) Press ‘apple’-Q to quit the appication.

If you cannot succeeed to connect try to put the TCP/IP number of your machine rather than its logical name.

6. TROUBLESHOOTING