BI-200SM Research Goniometer

The Bl-200SM Research Goniometer System provides access to SLS and DLS studies with an automatic, modular, and versatile system.

The Brookhaven Instruments Approach to Light Scattering

Brookhaven Instruments’ scientists have extensive experience in the development of instruments and methods for light scattering and this experience has been incorporated into the BI-200SM to make it the finest instrument available for research applications of light scattering.

With a Brookhaven Instruments BI-200SM Research Goniometer System, this rich field of exploration is open to you for studies of both Static Light Scattering (SLS) and Dynamic Light Scattering (DLS).

The Bl-200SM Research Goniometer System provides access to all of these studies with an automatic, modular, and versatile system. It is a precision instrument designed for exacting scattering measurements. Based on a special turntable with precision ball bearings and a stepping motor, the Bl-200SM’s modern design and quality construction guarantee precise measurements due to the wobble-free movement of the detector. It is field proven in hundreds of laboratories. It is ideal for macro-molecular studies and submicron particle sizing.

By taking advantage of the multiple inputs available on the TurboCorr correlator a new capability of the BI-200SM system is created. By adding an optical signal splitter to the beam of scattered light and a second detector it is possible to eliminate the effects of very high-speed interference from the detector(s). This Cross-Correlation System provides remarkably clean information as seen in the article we have presented.

The BI-200SM Research Goniometer modularity simplifies system expansion. Featuring a standard optical rail, the BI-200SM can be used with neutral density filters, a polarizer, an analyzer, and a reference detector. Special sample requirements can often be met by changing the cell holder design or size.

Overview

Features at a glance

Stepping motor controlled, multiangle measurements
Particle size and size distributions
M_w, R_g, A₂ for dilute polymer solutions
Cross-correlation detector option
Avalanche photodiode detector option
CONTIN, Zimm, Guinier, Fractal, and more

Advantages of the BI-200SM Research Goniometer System

Both DLS and SLS modes: Correlation & Intensity Measurements
Large angular Range: 8° to 155° with 25mm cells: 15° to 155° with 12 mm cells.
Fine Adjustment Control: Read angle to 0.01° directly on large, fine-control adjustment knob.
Open Design/Standard Optical Rails: Facilitates user customizations for special purposes.
Temperature Control: Heating and cooling via any standard external circulator Separate temperature and filtration plumbing.
Special Design Glass Vats: Specially polished and flat entrance window ensures minimum flare.
Alignment Cell: Fine-screw vertical adjustment makes finding the center of rotation easier.
Multiple Laser Line Filters: Filter wheel with 632.8 (HeNe), 514.5/488.0 nm (Ar+), one open position for weak scatterers, and 2 blank (shutter) positions. Also available with 532 nm bandpass filter
Enhanced Viewing Optics: Coated, precision achromats coupled with behind-the-slit viewing and high-quality eyepiece make alignment easier.
Additional Alignment Aperture: Alignment of laser much simpler and faster.
Variety of Cell Holders: High precision cell holders standard, low-priced round cells available: 27.5 mm dilution vials fit cell holder sleeve. Special small-volume cell available.

Measurement Principles

Light Scattering occurs when polarizable particles in a sample are bathed in the oscillating electric field of a beam of light. The varying field induces oscillating dipoles in the particles and these radiate light in all directions. This important and universal phenomena is the basis for explaining why the sky is blue, why fog and emulsions are opaque and other observations. It has been utilized in many areas of science to determine particle size, molecular weight, shape, diffusion coefficients etc.

Dynamic & Static Light Scattering (DLS/SLS)

In the SLS mode, time-averaged intensity measurements are made – at either fixed or variable angles – in the range from 8° to 155° and analyzed with software provided for the methods of: Zimm, Berry, Debye, Guinier, Kratky etc.

Such evaluations using measured angular or concentration dependencies of the intensity of the scattered light provide key information for those interested in the such topics as:

M_w Molecular weight determinations
R_g Radius of gyration
A₂ Determination of second virial coefficient
Micro-emulsion technology
Colloid behavior
Complex fluid characterization
Emulsion polymerization
Particle size growth
Nucleation processes

The field of DLS measurements is at least as rich as that of SLS . In this method the dynamics of the scattered light are determined and analyzed. The short-term intensity fluctuations (dynamics) of the scattered light arise from the fact that the scattering particles are undergoing rapid thermal motions. These movements are called Brownian motion and they cause short term fluctuations in the intensity of the scattered light. Various terms have been used for this phenomenon. These are Dynamic Light Scattering (DLS), Photon Correlation Spectroscopy (PCS) and Quasi-elastic Light Scattering (QELS), We will adhere to DLS. To uncover the key parameters which describe the diffusive motions a digital autocorrelator is used to determine the autocorrelation function (ACF).

From these DLS measurement many interesting subjects may be explored, among them:

Particle size distributions
Particle aggregation phenomena
Micellar systems
Micro-emulsion technology
Colloid behavior
Vesicles & liposomes
Plasmid DNA’s
Particle size growth
Nucleation processes & protein crystallization

Specifications

Beam Focus and Steering	Includes mounts, adjustments, and apertures
Turntable	200 mm O.D. turntable, worm gear, and ball bearnings; manual or automatic selection of angles in 0.01° steps; precision machine base with mounting holes; positioning table with micrometer adjustments (power supply and controller for stepping motor is optional)
Specimen Cell Assembly	Including thermal enclosure, centering adjustments, seperate plumbing for temperature control and index matching liquids, round cell holders, square cell holder and alignment cell
Index Matching Vat	With optically flat and specially polished entrance window, precision machined and annealed to minimize stray light
Periscopic Beam Stop	Located inside vat to prevent flare from exit window; provided with coupling for use with optional, zero-angle reference detector
Main Detector Optics	Entrance aperture 3 mm Coated, adjustable achromat for focusing scattered light onto 200 micron slit; slit position adjustable Reflex mirrow and high quality eye piece for viewing scattering region through slit Filter turret with 637, 532, 633, 514 and 488nm narrow band pass filters and 100, 200, and 400 micron, 1, 2, and 3 mm pinhole for SLS & DLS measurements.

A policy of continual improvement may lead to specification changes.

Options & Accessories

Options

BI-CrossCor	Eliminate detector artifacts by cross correlation with 2 APDx diodes.
BI-SFS	The new BI-SFS sample filtration system provides a fast and convenient way to clean your light scattering samples, a necessity for samples smaller than 20 nm. Utilizing Teflon tubing and nonreactive components, the BI-SFS is compatible with most smaple filtration needs. Its modular design allows users to change pump heads and speeds to encompass virtually any possible application.
BI-200SMPt	Allows direct measurement of temperature in the index matching liquid near the sample cell. Values updated every second in 32-bit, BI-DLSW software used in calculations.
BI-LRM	Laser rail and mounts for most lasers. Laser are frequently supplied by the user. Contact the factory for recommendations.
BI-TCD	Temperature controller, external circulator type, -20 to 100 ºC, alphanumeric setting and read out, ± 0.1º stability.
BI-PA	Polarization Analyzer, Glan-Thompson prism, 5×10 -6 extinction, 2-position mount.

Accessories

BI-RC12	Nominal 12 mm O.D. Round Glass Cell, polyethene cap.
BI-RC25	Nominal 25 mm O.D. Round Quartz Cell, dual Teflon tops, mounting ring.
BI-RC27	Nominal 27.5 mm O.D. Dilution Vials, package of 100 with HDPE scew caps.
BI-SVC	Small-volume cell for precious samples.