SIKA - Cold 3-Axis Spectrometer
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More information on SIKA
3-axis (or triple-axis) spectrometers were originally developed by Bert Brockhouse (Nobel Prize in Physics, 1994) at Chalk River in Canada, and he was awarded the Nobel Prize in part for this invention, along with the constant-Q method of operation and for a series of seminal experiments performed at Chalk River in the fifties and sixties.
There are two rotation axes at the monochromator and sample. In the triple-axis spectrometer, a further crystal 'analyser' is added after the sample. This allows one to measure the neutron energy before and after scattering process.
If the incident and scattered neutron energies are equal, there is no net energy transfer to the sample and this is called elastic scattering, this is different from Total scattering or diffraction.
In solids, the transferred energy is in the form of quantised sound waves or phonons (by analogy to photons as quantised light), or magnons (quantised magnetic waves) or even as energy to transferred to individual electrons, as they jump from one quantum level to another. Typically, the inelastic scattering has an intensity one ten-thousandth of the equivalent elastic scattering.
By measuring the energy spectrum, and interrupting it in terms of how the atoms move with respect to each other we get a better understanding of the forces between atoms, or between magnetic moments. This is particularly important in understanding how materials change structure (phase transitions), and in understanding other thermodynamic properties of solids (specific heat, magnetic susceptibility, bulk modulus, etc.).
The SIKA (viewing the cold source) is designed to study problems in low-temperature physics, like understanding novel ground states of materials (superconductors, magnets, strange metallic states, etc.). It complements the Bragg institute other triple axis spectrometer TAIPAN which with its thermal spectrum is more suited to phonons, single ion properties and magnons.
Science on SIKA includes understanding zero-temperature phase transitions, other unconventional superconductors besides high-Tc, model statistical-mechanics systems, metal-insulator transitions, ionic conductors and so on.
Both TAIPAN and SIKA are highly configurable and versatile, and will have the most intense thermal and cold beams in the whole facility, together with the lowest background levels. There will be a substantial number of diffraction experiments, particularly when looking for weak scattering effects, performed on both instruments.
28.4o ≤ 2ΘM ≤ 120o
-100o ≤ 2ΘS ≤ 100o
-90o ≤ 2ΘA ≤ 90o
Dimensions: 220 mm x 232 mm(width x height)
Pyrolytic Graphite (002), double focusing
Beam size 80mm x 150mm(W x H)
Cold source - monochromator 6715mm
Virtual source - monochromator 2100mm
Monochromator - sample 2100mm (extendable)
c1 (pre-monochromator) 20", 40", 60", open
c2 (post-monochromator) 10", 20", 40", 60", open
c3 (pre-analyser) 10", 20", 40", 60", open
c4 (post-analyser) 20", 40", 60", open
Incident beam filters
Cooled polycrystalline beryllium (17cm)(Ei < 5 meV)
Pyrolytic Graphite (2 + 3 cm)
Sapphire (8 cm)
- CF-1, 3,4 CCR bottom-loading cryostats (3K - 300K)
- CF-7&8 top-loading cryofurnaces (4K - 450K)
- Helium-3 single-shot (0.5K for 8 hours)
- OC-1 Orange cryostats (1.5K - 300K)
The sample environments above were successfully commissioned. The 12T magnet, dilution refrigerator, and CF-10 are being commissioned on SIKA.
Note: Various sample environments are managed by the Bragg institute, whose sample environment group can accommodate the following on SIKA. If you would like to use some of this list please see the available Sample Environment, please contact us.