focusing devices
parabolic guide optic - HQR, JRR-3M
The high resolution triple-axis spectrometer (JRR-3M) uses a double focusing parabolic guide optic to enhance the neutron intensity available for experiments. The device is optimized with a focal length of 290mm in the horizontal plane and 92mm in the vertical plane from the exit of the guide. The supermirror coating with m = 3 and high reflectivity (R > 0.85) enables efficient beam focusing.
- type: parabolic focusing guide optic
- path/profile: truly curved parabolic
- cross-section: 21.07 × 54.85mm˛ → 10 × 16mm˛
- length: 1000mm
- coating: Ni/Ti, m = 3
- substrate: Borofloat
- waviness of truly curved parabolic profile < ≈10-4 rad
- pronounced beam focusing
multi-channel parabolic optic - JRR-3M
This optic focuses in the vertical and horizontal plane. The vertical focusing is optimized by sub-dividing the guide height into 9 channels with parabolic profiles. The horizontal focusing needs to be only moderate, thus it is sufficient to use a linear tapering.
- type: multi-channel parabolic optic – 9 channels
- path/profile: truly curved parabolic, linear tapering
- cross-section: 20 × 90mm˛ → 12 × 52mm˛
- length: 1.8 m
- coating: Ni/Ti, m = 3, 3.6
- substrate: float glass, Borofloat
- pronounced beam focusing
S. Yamada et al., Physica B 385–386 (2006) 1243
semi-elliptic neutron guide - PGAA, FRM-II
The Prompt Gamma Activation Analysis station at the FRM-II utilizes an elliptic neutron guide which is attached to the preceding conventional neutron guide. Simulations of the instrument group established that a semi-elliptic neutron guide provides best focusing properties. The last section (≈ 1 m) is mounted on an optional support, which has highly repeatable positioning. Thus a simple change between two different beam sizes is possible.
- type: semi elliptic neutron guide
- path/profile: truly curved elliptic
- cross-section: 50 × 110mm˛ → 8.42 × 18.55mm˛
- length: 7090mm
- coating: Ni/Ti m = 3
- substrate: float glass
