Ultra-Small-Angle Neutron Scattering Instrument


Mission Statement

Analyzing the structure of inhomogeneities, from minerals to biological tissues.

Instrument Description

USANS is designed for the study of hierarchical structures in natural and artificial materials. It can be considered an advanced version of the classical Bonse-Hart double-crystal diffractometer (DCD), which in contrast with its single-wavelength reactor-based analog, will operate with the discrete multiwavelength spectrum of Bragg reflections.

The optical scheme of the USANS instrument is similar to that of the conventional Bonse-Hart DCD; however, the pulsed nature of SNS offers an opportunity to separate the orders of Bragg reflection in time space using the time-of-flight technique. Thus, the application of time-of-flight to the USANS technique allows the separation of data optimized for neutron flux and the Q resolution or minimum accessible Q while simultaneously removing contamination by higher harmonic reflections, one of the most significant contributions to the intrinsic instrument background on this class of instruments.


Ultra-small-angle neutron scattering provides a new way to solve a broad range of scientific problems such as:

  • Structure of soft matter systems including polymer solutions and melts, colloidal suspension and micellar solutions
  • Structure of precipitate strengthened alloys
  • Phase transitions and critical phenomena

Requesting Complementary SANS beam time on a USANS proposal

Beginning with the Spring 2020 call for proposals, users submitting USANS General User proposals may request SANS beam time in order to obtain complementary information on the same sample(s) as for the USANS experiment, with the following conditions:

  1. SANS beam time that has been requested with a USANS general user Proposal that has been awarded time through the general user program review process may only be used to measure the samples that were characterized by USANS.
  2. Only experiments that use the standard sample environment (10-70°C, titanium or copper demountable cells, or solid thin films) are eligible for measurement through this program. In the event that a specialized sample environment is required, SANS beam time must be obtained through the general user (GU) program.  
  3. The SANS experiment will be performed on the requested SANS instrument if schedule permits during the awarded cycle, but staff reserves the right to perform the experiment on any one of the GP-SANS, Bio-SANS or EQ-SANS instruments depending on capabilities and availability.
  4. The SANS beam time at SNS or HFIR will be scheduled by the members of the team of the SANS instrument to be used.
  5. Users are encouraged to perform the SANS experiment, if possible.
  6. If users are not able to attend the SANS experiment due to scheduling, a staff member will perform the experiment on their behalf.
  7. Staff members are not responsible for any sample degradation or problems that result from sample handling that occur between the USANS experiment and the SANS experiment. 


Moderator Decoupled poisoned hydrogen
Source detector distance 30 m
Focusing    Copper mosaic Cu (111) crystals
Monochromator and analyzer Si (220) channel-cut, triple-bounce crystals
Bragg angle 70°
Wavelength spectrum 4 Bragg reflections at 3.6, 1.8, 1.2, 0.9 Å
Q range 1x10-5 Å-1 < Q < 3x10-3 Å-1