Very Small Angle Neutron Scattering (VSANS)
The second SANS instrument at BER II is dedicated to soft matter research. V16 covers a Q-range from 10-3 nm-1 to 8.5 nm-1. In standard time-of-flight mode an offset of the detector to the instrument axis to extend the Q range will be possible.
The instrument works in the time-of-flight mode with ordinary pinhole collimation and in an optional low-q mode using multi pinhole grid collimation. In the latter mode many beams focus on a high resolution detector, which is only used for this option. The option is in a development phase.
Structure determination of mesoscopic particles, precipitations or voids in the range of a few nanometers to 50 nm.
colloid vesicles, proteins, voids in battery electrodes, agglomeration, gas adsorption, etc.
Following to a multichannel bender that supplies cold neutrons, a set of four choppers is run in a way that optimum pulse frame usage is made for the wanted temporal resolution and the individual instrument setup.
After this pulse definition unit, the neutrons enter a 12 m collimation chamber where segments allow to chose one of four beam optics to be brought into the beam axis. They are equipped with guide sements, diaphragms, and the multi-pinhole set-up. Additional diaphragms are at the beginning and end of the evacuated collimation chamber.
The scattering volume is typically defined by a diaphragm on the sample holder. V16 has a standard sample holder for 20 positions on which standard quartz cell cuvettes can be mounted in an easy and reliable way. The cuvette adapters are fully compatible to the V4 cuvette holder. The samples can be thermalized (-20°C to 80°C, for other values ask the team), and put under inert gas. The sample table can hold a load of 500kg+.
Entering the detector chamber through an Al window, the scattered neutrons travel to a multi-tube detector that can be moved through the evacuated detector vessel, in order to be set for the wanted Q-regime. The direct beam is caught by a movable beam stop in front of the detector. The beam stop can be exchanged against one with different size by picking it from a beam stop magazine within the vessel.
Data is recorded in list mode, which includes the chopper opening times.
|Neutron guide||NL 4C|
straight behind bender, SM coated, m=1
cross section 80x80 mm2 with cut-off λ=0.25 nm
|Collimation||exchangeable pinhole and guide optics on up to 12m length|
|Wave length||0.25 nm < λ < 1.8 nm|
|Wave length resolution|
|Q range||0.02 nm -1 < Q < 8.0 nm -1|
|Q resolution||5% < ΔQ/Q < 18%, depending on the chopper settings|
|Detector||2D 3He detector|
• 100x100 cm2 area
• physical pitch: 9 mm
|Sample-to-detector distance||1.7m up to 11.2m|
|Polarized neutrons||no, but principally possible|
|Instrument options||• Low-Q mode (not offered to users)|
|Sample environment||Hellma cuvettes (120, 404), rheometer, DEGAS cell and balance, battery cell, cryostats and magnets from sample environment group.|
|Software||Caress (control), Evalstat (in-house DAQ), Mantid (data reduction)|