fsc2: 6.18 Monochromator Functions

6.18 Monochromator Functions

Modules for the following monochromators exist:

spectrapro_275: SpectraPro-275
spectrapro_300i: SpectraPro-300i (tested with a 308i)
spex_cd2a: Monochromators by SPEX contrilled via the CD2A Compudrive interface
spex232: Monochromators by SPEX contrilled SPEX232 interface
oriel_cs_260: Oriel (Newport) Cornerstone 260

To use a module in an experiment put its name into the DEVICES section of the EDL script.

There are two different types of monochromators by SPEX. They are either wavelength- or wavenumber-driven. In case of wavelength-driven monochromators functions accepting or returning spectral positions etc. expect or return them in units of wavelengths, i.e. in m. In contrast, for wavenumber-driven monochromators the functions expect or return values in wavenumber units, i.e. in cm^-1. To make things even more interesting, for wavenumber driven monochromators a laser line position can be set. If such a laser line position is set values are expected or returned in relative wavenumber units, i.e. as differences between the wavenumber of the laser line and the absolute wavenumber.

Another important point is that for SPEX type monochromators an offset (between the wavelength or -number displayed by the CD2A unit and the "real" wavelength or -number is automatically taken into account. Thus the position reported by the program and shown e.g. at the console of the CD2A interface unit may differ because the program tries to take care of the offset (see the description of the function monochromator_calibrate() below for more information). Furthermore, for wavenumber-driven SPEX monochromators also the position of the laser line gets remembered between experiments. These informations are stored in a file in the same directory where the module for the device resides (under the name `spex_cd2a.calib' unless specified differently in the configuration file for the device). This file automatically gets read in when the module is loaded and at the start of each experiment and rewritten at the end of the experiment.

Some of the functions listed below will only work when a monochromator is used in conjunction with a CCD camera (and have been tested only with the Roper Scientific Spec-10 CCD camera in conjunction with the supported monochromatore).

List of monochromator functions:

`monochromator_name()'
`monochromator_wavelength()'
`monochromator_wavenumber()'
`monochromator_laser_line()'
`monochromator_scan_setup()'
`monochromator_start_scan()'
`monochromator_scan_step()'
`monochromator_wavenumber_scan_limits()'
`monochromator_wavelength_scan_limits()'
`monochromator_shutter()'
`monochromator_shutter_limits()'
`monochromator_groove_density()'
`monochromator_grating()'
`monochromator_turret()'
`monochromator_exit_mirror()'
`monochromator_filter()'
`monochromator_output_port()'
`monochromator_step()'
`monochromator_wavelength_axis()'
`monochromator_wavenumber_axis()'
`monochromator_calc_wavelength()'
`monochromator_load_calibration()'
`monochromator_set_calibration()'
`monochromator_calibration_offset()'
`monochromator_calibration_factor()'
`monochromator_install_grating()'
`monochromator_zero_offset()'
`monochromator_grating_adjust()'
`monochromator_calibrate()'
`monochromator_init_motor()'
`monochromator_enforce_wavelength()'
`monochromator_enforce_wavenumber()'
`monochromator_grating_zero()'
`monochromator_set_gpib_address()'

Descriptions of monochromator functions:

`monochromator_name()'

Returns a string with the name of the monochromator being used.

`monochromator_wavelength()'

If called with no argument the function returns the current center wavelength (in m) of the currently used grating. If called with an argument the grating is moved to the specified center wavelength (which must be in the range covered by the monochromator and the current grating).

Please note: for SPEX monochromators doing a scan calling this function automatically aborts the currently running scan.

Also note: the Oriel Cornerstone 260 may under certain circumstances return negative wavelengths, but does not accept them.

`monochromator_wavenumber()'

If called with no argument this function returns the current center wavenumber in cm^-1 of the current grating, either in absolute units or, if setting a laser line position is supported by the device and has been set, in relative units, i.e. as the difference between the laser line position and the gratings center wavenumber. If called with an argument the grating is moved to the specified center wavenumber, which must be given in absolute units if setting a laser line position is not supported or it has not been set, otherwise in relative units. The possible range depends on the grating being used.

Please note: for SPEX monochromators doing a scan calling this function automatically aborts the currently running scan. This function isn't yet available for the SpectraPro-275.

Also note: the Oriel Cornerstone 260 may under certain circumstances return negative wavenumbers, but does not accept them.

`monochromator_laser_line()'

The function is only supported for wavenumber-driven SPEX monochromators. It allows to set (or query if the function is called without an argument) to set a laser line position. If such a laser line has been set the device automatically switches to using relative wavenumbers, i.e. differences between the laser line position and absolute wavenumbers. All EDL functions accepting or returning spectral positions will then also switch to such relative wavenumbers.

To set a laser line position the function expects a single argument, the position in absolute wavenumbers (even when a different laser line position has already been set and other functions expect spectral positions in relative wavenumbers!). To switch use of a laser line position off (and thus revert to spectral positions in absolute a zero or negative value must be passed to the function.

The module will store the current value of the laser line position at the end of an experiment and start off with this value when the next experiment is started (even if the setting has been changed manually at the CD2A console, so make sure you call this function at least once after installing a new laser with a different line position).

Please note: for monochromators doing a scan calling this function automatically aborts the currently running scan.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_scan_setup()'

The function is only supported for SPEX monochromators. These have a special scan mode, where scans can be done going from low to high wavelengths or from high to low wavenumbers (during a scan the monochromator doesn't have to do backslash removal, making the slew to a new position faster). For being able to start a scan the start position and the step width for the scan must be defined, which can be done using this function. To set the scan parameter the function expects to arguments, first the start position of the scan, given in wavelength units for wavelength-driven monochromators and in wavenumbers (absolute, if no laser line position is set, otherwise in relative units). The second argument is the step width, which must be a positive wavelength or wavenumber step size (even though for wavenumber-driven monochromators the scan is always in the direction of lower wavenumbers!).

If called without an argument, the function returns a two-dinemsional array, with the first argument being the start position and the second the scan step size.

Please note: for monochromators doing a scan calling this function automatically aborts the currently running scan.

`monochromator_start_scan()'

The function is only supported for SPEX monochromators and requires that the function monochromator_scan_setup() has been called previously to define the scan parameters. It slews the monochromator to the start position of the scan, switches to scan mode and returns the spectral position of the monochromator, either in wavelength units for wavelength driven monochromators or wavenumbers for wavenumber driven ones (in absolute units, if no laser line position has been set, otherwise in relative units).

Please note: if the monochromators is already doing a scan calling this function automatically aborts the running scan.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_scan_step()'

The function is only supported for SPEX monochromators and requires that both the function monochromator_scan_setup() has been called previously to define the scan parameters and that the monochromator has been switched to scan mode by calling monochromator_start_scan(). The function slews the monochromator to the next spectral position by the scan step size and returns the new position, either in wavelength units for wavelength driven monochromators or wavenumbers for wavenumber driven ones (in absolute units, if no laser line position has been set, otherwise in relative units).

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_wavenumber_scan_limits()'

This function is only supported for SPEX monochromators. It does not take any arguments and returns an array with two elements, the first being the lower scan limit in absolute wavenumbers (in cm^-1) and the second the upper scan limit. monochromators.

`monochromator_wavelength_scan_limits()'

This function is only supported for SPEX monochromators. It does not take any arguments and returns an array with two elements, the first being the lower scan limit in wavelengths (in m) and the second the upper scan limit. monochromators.

`monochromator_shutter_limits()'

The function is only supported for SPEX monochromators when driven by the CD2A interface (but not the SPEX232) that have shutters to protect the PMT or APD etc. from excitation light in a certain frequency range. The function can be used to query or set these shutter limits. To set the shutter limits the function expects two arguments, the lower and the upper shutter limit. If a laser line position has been set the function won't allow to set the shutter limits to values that don't cover the laser line. When called without an argument the function returns a two-dimensional array, with the first element being the lower shutter limit and the second the upper shutter limit.

Please note: for monochromators doing a scan calling this function automatically aborts the currently running scan.

`monochromator_shutter()'

This function is only supported for the Oriel Cornerstone 260 monocromators and allows to query or set the state of the built-in shutter. If called with no argument the function returns 0 if the shuuter is open and 0 when closed. If called with a true boolean argument, either the string "OFF" or the integer 0, or one of the strings "OPEN" or "OPENED" the shutter is opened. If called with "ON" or a non-zero integer or one of the strings "CLOSE" or "CLOSED" the shutter is closed.

The function will automatically take care that the shutter isn't closed or opened at a higher rate than the specifications allow, if necessary introducing short delays.

This function can only be used in the EXPERIMENT section.

`monochromator_groove_density()'

If called with no argument the function returns the number of grooves per meter of the currently used grating. If called with an integer argument it returns the number of grooves per m of the grating indexed by the number (an integer between 1 and the maximum number of installed gratings) passed to the function.

For the Oriel Cornerstone 260 the function may also be called with the a second argument, the umber of lines per meter of the grating. This number is sent to the device and then used by it to calculate the wavelengths and wavenumbers. This two-argument version of the function is only useful when a new grating has been installed.

The function can only be used in the EXPERIMENT section of an EDL script. It isn't available for the SpectraPro-275.

`monochromator_grating()'

The function is only supported for SpectraPro-300i and Oriel Cornerstone 260 monochromators. It queries or sets a new grating. If called with no argument the function returns the number of the currently used grating (an integer between 1 and the maximum number of installed gratings). If called with an integer argument the monochromator switches to the grating giveb by that number (if it is available).

When switching to a new grating for the SpectraPro-300i the center wavelength the new grating is set to remains the same as for the previous grating.

With the Oriel Cornerstone 260 before switching gratings the built-in shutter is closed and has to be explicitely re-opened (using the function monochromator_shutter()). Also kep in mind that after switching gratings the wavelength may be set to 0. order, so make sure you set a wavelength before re-opening the shutter in order to avoid exposing the detector to excessive levels of radiation!

The function can only be used in the EXPERIMENT section of an EDL script. It isn't available for the SpectraPro-275.

`monochromator_turret()'

The function is only supported for SpectraPro-300i monochromators. If called with no argument the function returns the number of the currently used turret of the monochromator (an integer number starting at 1). If called with an integer argument it switches the monochromator to the indexed turret.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_exit_mirror()'

The function is only supported for SpectraPro-300i monochromators. If called with no argument the function returns the position of the exit divertor mirror, where 0 stands for front and 1 for side. If called with an string argument of "FRONT" or an integer argument of 0 it moves exit diverter mirror to position the beam to the front port position, of called with a string argument of "SIDE" or an integer argument of 1 it moves the mirror to position the beam to the side port.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_filter()'

The function is only supported for Oriel Cornerstone 260 monochromators having a wheel with up to 6 filters (and if support for the filter wheel is compiled in). Since not all have a filter wheel, the existence of this function depends on the configuration for compiling the module. The function allows to query or set which filter is used. If called without an argument the filter currently in use is returned, as an integer between 1 and 6. If called with an integer argument between these values the wheel is turned to the corresponding filter.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_output_port()'

The function is only supported for Oriel Cornerstone 260 monochromators, which have a motorized mirror that allows selecting one of two output ports. If called without an argument the function returns 1 if the exit mirror is set for the axial port and 2 for the lateral port. If called with a string argument of "AXIAL" (or the integer 1) or "LATERAL" (or, alternatively, 2) the mirror is set to the corresponding output port (and returns 1 or 2 for the output port that was set).

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_step()'

The function is only supported for Oriel Cornerstone 260 monochromators. It allows to directly query or set the position of the stepper motor moving the gratings. If called without any arguments the function returns the current position as an integer value.

If called with just an integer value the stepper motor is moved by that amount of steps upwards or downwars. If an additional boolean argument, which is set to true (i.e. either 1 or the string "ON") the function only tests if moving the motor by this amount is possible. If called wit one or two arguments the function always returns either 0 or 1, indicating if the move is possible. If an actual attempt to step the motor fails the function does not throw an exception but merely emits a warning.

Note: if can't reliably checked during the test run if an attempt to move the stepper motor will fail, so during the test run the function will always return successful.

This function is mostly meant for making small adjustments to the grating position e.g. during calibrations.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_wavelength_axis()'

The function requires that the module for a CCD camera is available that returns information about the settings of the camera. It returns an array with four elements.

The first first element is the wavelength at the leftmost pixel of he chip and second element being the wavelength difference between neighboring pixels.

The third value is the wavelength at the first data point returned by the camera, taking its setting for the ROI and binning already into account, while the fourth value is the wavelength difference between data points (which will be different from the difference between neighbouring pixels when horizontal binning is used).

For the SpectraPro-300i monochronator the function can be called with up to two arguments, an integer for the grating number and the wavelength at the center of the chip. If these arguments aren't given, the currently used grating and wavelength of the monochromator are used.

For the SPEX_CD2A and SPEX232 monochromators the function accepts a single argument, the the wavelength at the center of the chip. If no argument is given the currently set wavelength of the monochromator is used.

This function isn't available for the SpectraPro-275.

For SpectraPro-300i monochromators it is required that a calibration for the grating has been loaded, either by calling monochromator_set_calibration() or monochromator_load_calibration(). If no calibration has been loaded for the grating a warning is printed and the returned scaling values represent pixel numbers relative to the center of the CCD chip, not wavelengths.

The function is mostly meant to make it easy to obtain a wavelength scale to be used with the functions change_scale_1d() and change_scale_2d(). Normally you will rather use the third element of the array returned by the function as the start value for the axis and the fourth element as the step width, since these already are adjusted for the ROI and binning of the camera.

Please note:: The function assumes that the spectra taken with the camera show increasing wavelengths going from the left to the right side!

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_wavenumber_axis()'

This function is similar to the function monochromator_wavelength_axis() but instead of returning values to be used for setting a wavelength axis the values are suitable for setting up a wavenumber axis (and, if given, instead of the wavelength at the center position of the chip, the wavenumber at this position must be passed to the function).

This function isn't available for the SpectraPro-275.

Please note:: The function assumes that the spectra taken with the camera show decreasing absolute wavenumbers and increasing relative wavenumbers going from the left to the right side!
Please also note:: Since the data returned from the camera are linear in wavelength and not in wavenumbers the scale shown when using these values isn't really correct and should only be taken to be a rough estimate!

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_calc_wavelength()'

The function is only supported for SpectraPro-300i monochromators. It requires that the module for a CCD camera is available that returns information about the number of pixels of the CCD chip and the distance between pixels. It accepts a pixel position or an array of pixel positions on the CCD chip (relative to the left edge of the chip and starting with 1) and returns, depending on the type of the argument, either a number or an array with the exact wavelengths for the pixel position(s). The function also accepts up to two arguments, an integer for the grating number and the wavelength at the center of the chip. If these arguments aren't given, the currently used grating and wavelength of the monochromator are used.

To be able to work the function also requires that a calibration for the grating has been loaded, either by calling monochromator_set_calibration() or monochromator_load_calibration() (see below). If no calibration has been loaded for the grating a warning is printed and the input value(s) are simply returned.

This function isn't available for the SpectraPro-275.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_load_calibration()'

The function is only supported for SpectraPro-300i monochromators. It tries to load a file with calibration data for one or more of the gratings. For each grating three values are required for a complete calibration.

The first value is the inclusion angle (i.e. the angle between the incident and the reflected beam for the center wavelength of the grating) of the monochromator (in degrees), the second the focal length of the monochromator (in m) and the third and final value is the detector angle (in degrees), i.e. the angle by which the plane of the CCD chip is rotated out of the focal plane.

In the calibration file you will find lines like the following for each of the gratings:

INCLUSION_ANGLE_1  =   30.3
FOCAL_LENGTH_1     =   301.2 mm
DETECTOR_ANGLE_1   =   0.324871

The number appended to each of the keywords stands for the grating (in this example the first) they are to be used with.

Calling the function will load the data from the calibration file. These calibration data are required to be able to calculate correct wavelengths for the pixel positions of the CCD chip.

When the function gets called without an argument it tries to read a default calibration file. The name of this file is compiled into the module and can be changed via the configuration file of the module and then recompiling the module. If an argument is passed to the function this must be a string with the name of a file that the program has the permissions to read.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_set_calibration()'

The function is only supported for SpectraPro-300i monochromators. It allows to set calibration data for a grating directly instead of reading them from a file. It can also used to reset the calibration for a grating.

The function expects 4 arguments, the grating number (an integer between 1 and the maximum number of installed gratings), the inclusion angle (in degrees), the focal length (in m) and the detector angle (in degrees).

Alternatively, to clear the calibration for a grating the function can also be called with two arguments, the number of the grating and the string "DELETE".

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_calibration_factor()'

The function is only supported for Oriel Cornerstone 260 monochromators. It allows to query or set a factor that is used (in conjunction with an offset value, see monochromator_calibration_offset()) in calculating the wavelengths from grating positions. When called without an argument it returns the factor for the currently set grating. If called with a single argument, an integer of either 1 or 2 for grating #1 or #2, the factor for this grating is returned. If called with a grating number and another argument, this latter value is set as the factor for the addressed grating. Normally, you will call this function only after installing a new grating, using the factor provided by Oriel.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_calibration_offset()'

The function is only supported for Oriel Cornerstone 260 monochromators. It allows to query or set an offset that is used (in conjunction with a factor, see monochromator_calibration_factor()) in calculating the wavelengths from grating positions. When called without an argument it returns the offset for the currently set grating. If called with a single argument, an integer of either 1 or 2 for grating #1 or #2, the offset for this grating is returned. If called with a grating number and another argument, this latter value is set as the offset for the addressed grating. Normally, you will call this function only after installing a new grating, using the offset provided by Oriel.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_install_grating()'

The function is only supported for SpectraPro-300i monochromators. It can be used to tell the monochromator about a new grating. It expects two arguments, the grating number (an integer between 1 and the maximum number of installable gratings) and a string with the part number of the newly installed grating. All part numbers are expected to start with a single digit, followed by a dash, a three-digit number with the number grooves per thenth of a mm (if necessary left-filled with zeros), another dash and an identifier for the blaze wavelength or type of the grating. Thus a valid part number string would be e.g. "1-120-750" for a grating with 1200 grooves per mm and a blazing wavelength of 750 nm. Another possible part number string is "2-030-HVIS". The total length of the string may not excceed 13 characters.

Alternatively, the function can also be used to tell the monochromator that a grating has been removed. In this case the part number string has to be replaced by the string "UNINSTALL".

Please note: There's a list of supported gratings in the manual on page 29. Other gratings, while sold as gratings for the device, can't be installed by the normal INSTALL command. I tried to implement a solution for these gratings, but which hasn't been tested yet. So, if you have such a grating and installing it doesn't work, please send me a bug report!

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_zero_offset()'

The function is only supported for SpectraPro-300i monochromators. It allows to either query or set the zero offset of a grating. The zero offset is basically an angle that results from misalignments of the grating (and the CCD chip) and leads to the zero order peak not appearing exactly at the center of the CCD chip. By setting the zero offset value correctly this misalignments can be compensated for. It is expressed as a number in the interval [-1,+1] and the correct value can only be found experimentally.

The function expects at least one argument, an integer number designating the grating (an integer between 1 and the maximum number of installed gratings). If there is no second argument the function returns the zero offset used for the grating. If there is a second argument (which must be between -1 and +1) the zero offset is set to this value.

Please note: setting a zero offset takes quite a long time (about half a minute), mainly because the monochromator needs to be reset. Fortunately, setting a new zero offset is only required when e.g. the monochromator has been opened up. Since the zero offset values are stored in non-volatile memory of the monochomator the setting won't get lost when the monochromator is switched off.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_grating_adjust()'

The function is only supported for SpectraPro-300i monochromators. The value that can be queried or set by this function is used to adjust the angle by which the grating is rotated when moving it to a certain wavelength. The monochromator has a built-in default value for the ratio between the angle and the wavelength which can be changed by the grating adjust value. If this value (and also the zero offset, see above) is set correctly, a line will appear at the center of the CCD chip when the monochronator is set to the wavelength of the line.

The grating adjust value is a number in the interval [-1,+1] and can the correct setting can only be found experimentally.

The function expects at least one argument, an integer number designating the grating (an integer between 1 and the maximum number of installed gratings). If there is no second argument the function returns the currently used value for the grating adjust value. Otherwise the second argument must be a number between -1 and +1 and the grating adjust is set to this value.

Please note: setting a grating adjust value takes quite a long time (up to half a minute), mainly because the monochromator needs to be reset. Fortunately, setting a new grating adjust value is required when e.g. the monochromator has been opened up. Since the grating adjust values are stored in non-volatile memory of the monochomator the setting won't get lost when the monochromator is switched off.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_calibrate()'

The function is takes different arguments for the SpectraPro 300i, the SPEX and the Oriel Cornerstone 260 monochromators. It isn't available for the SpectraPro-275.

For the SpectraPro-300i it is for use in the dispersion calibration of a grating, i.e. the procedure where from a set of at least 4 measured positions of known lines (at at least two different center wavelengths) the optimum values for the inclusion angle, the focal length and the detector angle are determined. This function requires that the module for a CCD camera is available that returns information about the number of pixels of the CCD chip and the distance between pixels.

The function expects a minimum of 5 arguments. The first is the grating number (an integer between 1 and the maximum number of installed gratings). The second is an array of the wavelengths of at least 4 measured lines (given in m). The third is the array of the center wavelengths used in the measurements of the lines (also given in m). The fourth is the array of the diffraction orders the lines where measured at. The fifth required array is the array of the measured line positions, given in pixel positions on the CCD chip (relative to the left edge, where the leftmost pixel is corresponds to position 1). All arrays must have the same length.

Using these values the function will now try to find the best fit for first the inclusion angle, then the focal length and finally the detector angle using a Simplex algorithm.

You may influence the way the Simplex algorithm tries to find the optimum values by specifying seven further, optional arguments: 1. the end criterion for the fit (per default this value is set to 1.0e-9, 2. the start value for the inclusion angle (in degrees), 3. the start value for the focal length (in m), 4. the start value for the detector angle (in degrees), 5. the start deviation for the inclusion angle (in degrees), 6. the start deviation for the focal length (in m) and finally, 7. the start deviation for the detector angle (in degrees).

After the function found what it guesses to be the optimum paramters it returns an (1-dimensional) array with three elements, where the first element is the inclusion angle (in degrees), the second element is the focal length (in m) and the third is the detector angle (in degrees).

When called without an argument for SpectraPro-300i monochromators the function returns an array with three elements, which are the current calibration settings for the inclusion angle (in degree), the focal length (in m) and the detector angle (in degree).

For the SPEX monochromators it can be used to set an offset between the wavelength or -number used to set the monochromator to the current position and the "real", i.e. experimentally determined wavelength or (absolute) wavenumber. Once it has been set, all functions will take this offset into account when talking with the device.

The second calibration value (the optional second argument) to be set by the function for SPEX monochromators is the wavelength (even for wavenumber driven monochromators) difference between two pixels of an attached CCD camera.

The offset is taken to be the difference between the "real" position of a line and the position where it appears when measured with fsc2. Thus the usual procedure to set the offset is to measure the position of a well-known line using fsc2 and then to call the function with the difference between the "real" position and the observed position. Afterwards fsc2 will automatically take the offset into account and, after a further call to monochromator_wavelength() or monochromator_wavenumber(), the line should seem to appear at the expected position.

Please note that the offset can only be set for wavenumber driven monochromators while using absolute wavenumbers, i.e. while no laser line position is set! If you want to determine and set a new offset first store the current laser line position, switch off use of a laser line position by calling monochromator_laser_line() with a zero argument and only after measuring and setting a new offset set the laser line position again.

If called without an argument for SPEX monochromators the function returns an array with two elements, representing the current calibration setting of the offset (in m for wavelength driven and in cm^-1 for wavenumber driven monochromators) and the wavelength or -number difference between two adjacent CCD camera pixels (or 0 if the value isn't known).

Please note: To set the offset of a SPEX monochromator to 0 don't pass a zero argument for the offset to the function. Instead determine the current offset setting by a call without arguments and then call the function again with that offset as the first argument!.

For the Oriel Cornerstone 260 the function requires a single argument, the wavelength the monochromators grating is currently set to (which you know by e.g. moving it to the exact position of a line of a calibration sample). Calling this function then induces the device to update its internal algorithm to calculate wavelengths. It Should only be used for minor corrections.

The function can only be used in the EXPERIMENT section of an EDL script.

`monochromator_init_motor()'

This function onky exists for SPEX monochromators controlled via the SPEX232 interface and only for those that have autocalibration capabiliy. If for these types of monochromators the function is called in the PREPARATIONS section an autocalibration is executed when the monochromator is initialized. Please note that this is usually not necessary and can take a rather long time.

`monochromator_enforce_wavelength()'

This function only exists for SPEX monochromators controlled via the SPEX232 interface. It allows, when called in the PREPARATIONS section, to set the wavelength the monochromator is currently set to, which then overrules the setting read from the file in which the state of the monochromator in the last run of the program is stored. This function should only be used when the data in the state file have gotten out of synch from the real setting of the monochromator (e.g. because different program was used in between that drove the monochromator to a different wavelength from the one stored in the state file).

`monochromator_enforce_wavenumber()'

This function only exists for SPEX monochromators controlled via the SPEX232 interface. It allows, when called in the PREPARATIONS section, to set the wavenumber the monochromator is currently set to, which then overrules the setting read from the file in which the state of the monochromator in the last run of the program is stored. This function should only be used when the data in the state file have gotten out of synch from the real setting of the monochromator (e.g. because different program was used in between that drove the monochromator to a different wavenumber from the one stored in the state file).

`monochromator_grating_zero()'

This function only exists for the Oriel oriel_cs_260 monochromator. It allows to query or set the gratung zero parameter (used internally by the device to calculate the center position of a grating). It expects at least one argument, the grating number. If no more arguments exist it returns the currently used zero paramter for the grating. If called with a second, positive argument this is used set as the zero paramter for the grating. This function should only be called with two arguments if the internal memory of the device became corrupted and the zero position argument should be the one from the data sheet for the device.

This function can only be used in the EXPERIMENT section.

`monochromator_set_gpib_address()'

This function only exists for the Oriel oriel_cs_260 monochromator. This device comes with a preset GPIB address of 4 that can only be modified via software. In ordr to do so the device must be entered into the GPIB configuration file with this address of 4 (and an already existing device with this address must be temporarily commented out and at least switched off or disconnected from the bus). Then an EDL script must be written and run that calls this function somewhere before the EXPERIMENT section. E.g. use

DEVICES:
  oriel_cs_260;

PREP:
  monochromator_set_gpib_address( 17 );

EXPERIMENT:

This sets a new GPIB address of 17 during initialization of the device and then stops the script immediately. The new GPIB address then has to be entered into the GPIB configuration file.

Note: Use this function only if you really have to. If you inadvertently set an address you don't know afterwards you'll have a hard time figuring out what it is and will have to do up to 31 trials to find it out before the device is under control again!

If the GPIB address of the device is already set to the one this function is called with it has no effect.

This document was generated by Jens Thoms Toerring on September 6, 2017 using texi2html 1.82.