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ROUTINE USE OF ELEXSYS E-500 ESR SPECTROMETER; X-BAND

Stop and reverse the startup procedure, and inform the system manager if any step described below cannot be accomplished as described.

1.         Turn clockwise yellow lever on pipes behind magnet to turn on cooling water at a flow of >20 psi. 

2.         Turn on the main computer if necessary, and wait for it to boot up. Log on to your account and double-click the Xepr icon on the Linux desktop to start the main control program.

3.         Press the power button (green, upper left) on the main console that stands to the left of the magnet.  It will take about 30 seconds for all the hardware in the console to initialize, during which you can proceed with subsequent steps. 

4.         Flip the heat exchanger power switch to ON (you will hear the water circulation begin).  Press on the ELECTR ON button on the extreme top left of the power supply, then press the POWER ON button next to it.

5.         In Xepr, go to Acquisition > Connect to spectrometer.  This will display a small panel that says Server name with the entry E500 (case sensitive).  Click OK.  This should bring up a monitoring panel that shows Standby, Tune, Operate, Frequency and other settings.

6.         Always with the monitoring panel showing Standby in green, install your desired X-band type cavity.  You should already know how to do this.  If you are unsure, then ASK FOR HELP FROM SOMEONE WHO KNOWS BEFORE MESSING AROUND WITH THE PROCESS.

7. In Xepr, go to Acquisition > Spectrometer Configuration > Signal Channel.  Select the proper Resonator (1; 2 if using the back cavity of the dual resonator).   Select the appropriate Standard Calibration Data file from the pull-down entry, and Apply it.  Close the panel.

8.         Always with the system on Standby, properly place your sample in the cavity.  Be careful not to break the sample in the cavity, or force it in. The cavity is incredibly expensive.   Do not force the sample tubes (4 mm o.d. quartz, 2 mm o.d. quartz, borosilicate capillaries) through the sample adapter plugs. BE CAREFUL!!  It is best to hold the sample up in front of the cavity to gauge the depth of the sample in the cavity.  The bottom of the sample tube should be about at the bottom of the square in the front of the cavity.  The sample should be supported with the bottom insert plug, except if you are using capillaries. 

9.         Click the Tuning button in the upper icon menu (it looks like a small copy of the standard dip), then activate the Tune button in the panel below this.

10.         Set the Attenuation to 30 dB. (Left set of vertical arrows in the attenuator box change the setting by 10 units at a time and right set of vertical arrows change the setting by 1 unit at a time). Move the frequency slide-bar to center the dip. If you are having trouble finding the dip, try increasing the Bias slide-bar.  Activate the Operate button in the panel.  Finally, c lick the Up or Down button in Autotune; wait for lock.  Alternatively, hand tune phase and bias.

11.       Decrease the Attenuation by 2-3 units at a time, and each time click the Finetune button and wait for Stop to go green.  Continue down to Attenuation of 10.  Finish by setting the Attenuation back to 20, and and Finetune one more time.Close the tuning panel.

12.       Click on the new experiment button (icon menu atop main display, star-burst with Exp inside it).

13.       In the new panel, click the C.W. (continuous wave) tab.  Set Abscissa 1 to Field, Abscissa 2 to None, and Ordinate to Signal channel.  Temp unit, Goniometer, and Gradient Unit buttons should not be green (active) for routine use; deactivate them if necessary. Click Create.  You will have to give a temporary name to the experiment; after this the panel will close.

14.       Toggle on Activate button (rightmost in the picture shown).  The other buttons from left to right are Stop and Pause (after the present scan is finished).  If you toggle off the Activate button, ESR parameters are set only when you Run your spectrum (step 20).

15.       Click the Parameters button in the main (upper) tool bar. 

16.       In the Acquisition Parameters panel, click the Absc Field subtab, and set the Center Field and Sweep Width parameters. This can be done efficiently using Setup Scanning procedure (Chapter 5.3 in the Basic Operations Manual) to find the best center field, sweep width, microwave attenuation and receiver gain settings (see step 17).

17. In the Signal Channel section, click the Detection subtab and set the following values:

• Modulation Frequency (default is 100, smaller values give more noise and better resolution),
• Modulation Amplitude (default is 1, smaller values give more noise and better resolution),
• Receiver Gain (usually 20-60 dB, larger values give more signal, but truncate big peaks)
• Time Constant (usually 1.28-5.4 s, larger values decrease noise and resolution),
• Sweep Time (best to be 10-fold larger than time constant, unless your spectrum is really noisy)
• Resonator default is 1 (set for 2 if you are using the back cavity of a double resonator)
• Harmonic default is 1 for 1st deriv spectra, set for 2 for 2nd deriv spectra.

18. In the Acquisition Parameters panel, click the Microwave subtab.  The default microwave attenuation is 25 dB (smaller numbers give bigger signals, but may cause signal saturation)

19. In the Acquisition Parameters panel, click the Scans subtab and set the number of scans to make.

20.       Click the Run button to acquire spectrum; if needed, click Stop (stops after current scan) or the Run button again (stops immediately).

21.       To get a well-centered spectrum, execute Acquisition > Tools > Center Tool (horizontal double arrow in the tool bar beneath the spectrum), move the mouse to the cursor that shows Center Tool, left click, and pull the cursor to the position that you want to be the spectral center.  You can also change the spectral width by pointing, left clicking, and dragging the left or right limits of the Center Tool . Click on the trash barrel in the tool bar above the spectrum to Remove the Center Tool tool.  Click on the Run button to reacquire a well-centered spectrum.  If you used Setup Scanning (step 16) you already did this.

22.       Store your spectrum by clicking the leftmost, red spectrum in the upper tool bar, and choosing the appropriate data set.  This means your spectrum will be available for as long as your Xepr session is open.  It has not yet been saved to the computer, however.

23.       Save your spectrum in a manner similar to Store (step 22).  You will need to enter a filename, thereby saving your spectra as a pair of files to the hard-drive (*.DTA, *.DSC).  Do not put spaces into the name (none of that Apple naming stuff).  It is also possible to save ASCII or old Bruker format files for export.

24. When finished, click the Tuning button, change attenuation to 60, go to Standby, and Close.

25. In Acquisition, Disconnect from spectrometer, then Exit from Xepr (best not to save settings) and Logout.

26. Remove your sample tube carefully from the cavity, and cover the cavity.

27. In order, turn off the two buttons on the power supply, then the heat exchanger, then the main console, then the water.   TURN OFF THE WATER.  TURN OFF THE WATER. TURN --- OFF --- THE --- WATER!!!