Chemistry Laboratory

Instrument Picture
Sample Data Picture

Instrument Specifications:

• Manufacturer: DAWN® HELEOS™II
• Flow Cell Volume: 70 µl (0.07 µl scattering volume)
• Minimum Sample Size: ~1.5 ml
• Light Source: 120 mW GaAs linearly polarized laser; 100 mW delivery to the cell

DAWN HELEOS II is classified as a Class 1 Laser Product. Under normal
operation, no laser radiation should escape from the instrument, and no
protective equipment must be worn.

• Laser Operating Wavelength: 658 nm
• Beam (1/e²) Intensity Diameter: 80 µm vertical, 52 µm horizontal
• Polarization Ratio: > 100:1
• Max Power Stability: < 0.5%
• Typical Optical Noise: 0.1%
• Typical Operating Voltage: 2.4 VDC
• Typical Operating Current: 100 mA
• Adjustable Temperature Range:
• Detector Type: 18 custom-designed, ultra-quiet hybrid photodiodes with built-in FET transimpedance amplifiers. Single photon counting module for QELS option
• Detector Resolution: 24 bit
• Angular Range: typically 15° -160° depending on solvent/glass refractive indices
• Mobile phase compatibility: All-solvent compatible (aqueous and organic)
• Signal Processing: On chip sinc filter with proprietary dust rejection filter
• Analog Inputs: 4 differential analog inputs with 24 bit resolution. Input range -10V to 10V
• Analog Outputs: 2 analog outputs from selectable measurements channels -10V to 10V
• Molar Mass Range: < 103 to 109 g/mole (Daltons) (typical)
• Molecular Size Range: ≈ 10 to 500 nm (typical)
• Computer Interface: Ethernet and USB 2.0 interface
• Front Panel Display: 162.5mm 16-bit LCD display with Graphical User Interface
• Power: 400 W maximum, 200 W typical
• AC Voltage: 90–250V @ 50–60 Hz, universal power input
• Footprint: 30 cm x 20 cm
• Weight: 10 kg
• Software Compatibility(ASTRA 6 software): Windows® XP and Vista (32 bit)

Instrument Description:

The DAWN HELEOS II combines the proven features of photometers, nephelometers, turbidimeters and “goniometers” into a single light scattering instrument for Multi-Angle Light Scattering (MALS) measurements. It can be used as a detector for continuous-flow (GPC/SEC/HPSEC) detection or as a stand-alone unit in a batch or microbatch mode.
The read head and the laser system anchor to the base plate, and the flow cell and manifolds are mounted directly into the read head to provide a single, stable optical bench. The laser beam is aimed into the flow cell, and passes in the same direction as the flowing stream. The windows that let light pass through the flow cell are recessed in the manifolds, minimizing sample volumes and stray light.
In the DAWN HELEOS II, 18 discrete photodetectors are spaced around the flow cell enabling simultaneous measurements over a range of angles (typically 15° -160° , depending on solvent/glass refractive indices). Each photodetector has its own DSP (Digital Signal Processor) chip for processing the analog signal. Electronic filters within the DSP chips and within the embedded computer process each light scattering and auxiliary signal for the greatest possible noise rejection without peak distortion. Since the analog-to-digital conversion is performed on-board, low light scattering signals are not prone to environmental “noise” or pickup. The digital output transmits to your computer through its Ethernet port, or USB (with the supplied ethernet-to-USB converter).

The DAWN HELEOS II system uses a 130mW laser operating at 658 nm which after intensity stabilization delivers 100mW to the sample. The DAWN HELEOS II also includes a state-of-the-art electronics package with an embedded microprocessor and a graphical user interface.
All functions are controlled by the microprocessor.

User Manual: A printed version of the user manual can be found next to the Instrument. Online or PDF versions of the user manual will be provided soon.

Short Instructions: coming soon

It is possible to book this instrument (if still available) for the use in the neutron guide halls or experimental hall close to one neutron scattering instrument. In this case please get in touch with the contact person at least two weeks prior to your beamtime to make a reservation.

Contact: Dr. Tobias Schrader, phone: +49 89 28910743, email: t.schrader@fz-juelich.de