Characteristics
Reactor hall, through-tube H6-H7 | ||
|---|---|---|
Neutron Flux: | 5 x 1014 n cm-2 s-1 | |
Available Crystals: | Flat | Si (220) |
| Bent | Si (220) | |
Eff. Solid Angle: | Flat: ~ 10-11 sr Bent: ~ 10-7 sr | |
Best Resolution: | 0.008 arc sec | |
Energy Range: | 50 keV - 7 MeV | |
Targets | |
|---|---|
Materials | stable elements |
Dimensions | 40 x 4 x 0.02 mm3 (bent) |
Mass | up to a few g |
Temperature | ~ 400°C |
Instrument Description
The ultra high resolution gamma ray spectrometers PN3-GAMS4 and GAMS5 are crystal spectrometers working in Laue geometry.
The basic concept of these instruments is to provide the best possible energy resolution by diffraction of gamma rays from perfect crystals, according to Bragg’s law. Both can operate with flat, nearly perfect Si or Ge crystals. In addition, a doubly bent crystal mode for GAMS5 is also available.
High angular resolution is obtained by using high precision optical interferometers. For this purpose the spectrometer crystals are mounted on interferometer arms. These can be rotated using a combined step motor/piezo device. Angular steps as small as 0.0004 arcsec are possible.
With GAMS4 extremely precise absolute measurements of gamma-etalons are made possible by an in-situ angle calibration of the interferometer.
Reference:
The GAMS4 Flat Crystal Facility, E.G. Kessler, M.S. Dewey, R.D. Deslattes, A. Henins, H.G. Börner, M. Jentschel and H. Lehmann, Nucl. Instr. Meth. A457 (2001) 187.