Monochromator-spectrograph MS750 series are devices with with a large flat focal field, combined with a high-intensity, accuracy and spectral resolution. They are completely automated spectral devices with focal length of 750 mm and F-number of 1/8.9, which can be used both as monochromators and spectrographs. High-quality optics and wide choice of diffraction gratings provide devices operation in a wide range from 185 nm up to 60 µm (depending on the selected grating).   M750 Series monochromator-spectrographs are based on Cherny–Turner asymmetric scheme that allows to minimize of aberrations and exclude spectra re-entrance from diffraction gratings and mirrors. Model MS7501i and model MS7504i have the astigmatism-correctedoptics what makes these devices applicable in multi-channel spectroscopy. Automated four-grating turret (model MS7504 and model MS7504i) provides a fast switching of gratings with high repeatability of the set wavelength and the vertical image.   In MS7501 and MS7501i models a single-position holder is used for easy manual switching of gratings. A wide choice of changeable gratings gives the best combination of high energetic efficiency and maximal spectral resolution for different spectrum areas.   Monochromators–spectrographs of MS750 series have one input port and two output ports. Selection of an output port is realized with an automated mirror. Either output spectral slits or multi-channel detectors can be installed on each of the output ports. Extremely high spectral resolution – better than 0.02 nm for grating 1200 grooves/mm,makeS monochromators-spectrographs of MS750 series ideal devices for high resolution spectroscopy: Raman spectroscopy, laser-induced breakdown spectroscopy and also for multi-channel spectroscopy – models MS7501i and MS7504i, which provides extremely high spatial resolution along the slit heigh.

I M A G I N G       Theory & Instructions 1. Spectral Instrument. Basic Concepts and Characteristics. 2. Spectral Devices. A Spectral Device Selection.  3. Spectra Detection. Detector Selection.

 Monochromator-spectrograph MS750 series, models

	MS7501	MS7501i	MS7504	MS7504i
Diffraction unit	Single-position holder for manually changeable gratings	Single-position holder for manually changeable gratings	Four–grating turret	Four–grating turret
Optics	Standard	Imaging	Standard	Imaging

 

In the devices with the standard optics (model MS7501 and model MS7504) a flat entrance deflecting mirror is used, and in the astigmatism–compensated devices (model MS7501i and model MS7504i) a cylindrical mirror is used as an entrance deflecting.

As well as in all Czerny–Turner design spectral devices, in the MS750 series an axis of the diffraction gratings rotation goes through the center of grating operating surface and coincides with the direction of grooves. This fact provides the stability of the geometry of the beams for formation of a flat and fixed focal field. The image quality in the whole flat focal field is optimized due to the use of an asymmetric scheme and use of a focusing large-size mirror allows one to use the whole focal field width without vignetting. Besides, Cherny–Turner asymmetric scheme provides a low level stray light and light re-entrance from the optical elements and detectors can be avoided.

In MS7504 and MS7504i the gratings rotation axes are arranged perpendicular to the spectrum scanning axis, providing a high repeatability of wavelength setting at replacing of gratings.

Optical system

Optical scheme:	Cherny–Turner (astigmatism–compensated in model MS7501i and model MS7504i)
Ports:	1 input, 2 output
Wavelength range:	185 nm - 60 µm (depends on the type of grating)
F/number (entrance):	8.9
Focal length (output):	750 mm
Scanning range limited by the grating rotation angle:	0 - 1270 nm (grating 1200 l/mm)
Main mirrors:	spherical
Stray light:	5.5 х 10-7 (20 nm from laser line 632.8 nm)
Focal plane:	28 х 10 mm

Optical scheme is optimized for:

• minimization of coma aberration over the whole operating spectral range
• elimination of the light re-entrance from two basic mirrors
• elimination of the light re-entrance between mirrors
  of the instrument and input windows of the detectors in the focal plane
• a large plane focal field for the whole operating spectral range
• astigmatism compensation for the whole operating spectral range
  by means of special correcting optics (for imaging modifications MS7504i and MS7501i)

*Imaging

*Horizontal magnification:	1.05
*Vertical magnification:	1.125
*Vertical spatial resolution:	<15 m="" --15--="">

* Characteristics of models with astigmatism compensation: MS7501i, MS7504i

Spectral images obtained with imaging monochromator-spectrograph MS7504i (grating 1800 l/mm, 
light source - mercury-helium lamp, pixel size of CCD detector 24x24 µm).

 Drive

Motor:	microstepper
Drive:	sine
Step size:	0.22 arc seconds
Precision:	± 1 step
Max. speed:	10000 steps/s

**Optics

Type of grating:	1200 l/mm, λ = 546 nm	Echelle, 75 l/mm, λ = 200 nm, 120 order
Reciprocal linear dispersion:	1.02 nm/mm	0.055 nm/mm
Spectral resolution:
- PMT (slit width 10 µm):	0.015 nm	0.0008 nm
- digital cameras (12 µm pixel):	0.02 nm	0.0011 nm
Repeatability:	± 0.007 nm	± 0.0009 nm
Wavelength accuracy:	± 0.034 nm	± 0.0045 nm
Average scanning step:	0.0017 nm	-
Scanning step at 200 nm:	-	2.25 x 10-4 nm

** For grating 1200 l/mm, slit width 15 µm, wavelength 546 nm

Gratings

Size:	80 х 70 х 10 mm
Rotation:	About the center of grating working surface
Mounting:	1. Automated 4-grating turret (models MS7504, MS7504i) 2. Positioner for 1 manually changeable grating (модели MS7501 и MS7501i)
Grating repeatability for the automated 4-grating turret (models MS7504, MS7504i):
- wavelength:	± 0.03 nm
- vertical image:	± 50 µm
Grating repeatability for 1 manually changeable grating (models MS7501 and MS7501i):
- wavelength:	± 0.05 nm
- vertical image:	± 75 µm

Ports

Number:	1 input, 2 output
Output port repeatability (automated mirror):	± 0.01 nm
Switching time (output port):	10 s

Spectral slits

Control:	Automated (drive) or manual (micrometer)
Width:	Regulated from 0 up to 2.0 mm
Parallelism:	± 1 µm
Accuracy (slit 1 mm):	± 10 µm
Repeatability:	± 1 µm (± 1.5 µm - manual slit)
Reading accuracy (micrometer):	2 µm
Step size:	0.5 µm
Height:	Diaphragm-regulated from 0 up to 10 mm

Integrated shutter

Shut time:	~ 100 ms
Max. frequency:	1 Hz
Control:	On-board CPU or TTL-signals from the external device

Control

Central:	on-board CPU
External:	PC
External interface:	Ethernet

Dimensions

Overall sizes (LхWхH):	950 х 361 х 343 mm
Weight:	45 kg (may vary, depends on configuration)