Compare triple-axis spectrometers
Monochromators, flux, analyzers, polarization, filters and unique capabilities, side by side.
Two tables compiled by the Instrumentation focus team of the International TAS Working Group (Adam Aczel, lead), from information supplied by each facility in 2026. Flux is the incident flux at the sample position in n cm-2 s-1 at the stated energy; values are facility-reported and measured in different ways, so compare with care. Blank or "t.b.d." cells are information the facility has not yet supplied. Corrections: contact the team lead (see contacts).
Cold triple-axis spectrometers
| Facility | Instrument | Monochromator | Incident flux (n/cm²/s) | Analyzers | Filter(s) | Virtual source | Comments or unique capabilities |
|---|---|---|---|---|---|---|---|
| ILL | ThALES updated 2026-09-24 | PG (002)1 Si (111)1 Heusler (111)2 | 2.4x108 @ 16.2 meV 1.3x108 @ 16.2 meV 2.7x107 @ 8.3 meV | PG (002)1 Si (111)1 Heusler (111)2 | Velocity selector | Yes | FlatCone option; high-magnetic-field compatible; new multiplexed option Marmot under commissioning; polarised neutrons including CRYOPAD. |
| ILL | IN12 updated 2026-08 | PG (002)1 PG (002)1 + polarizer (V-shape optics) | 8x107 @ 16.2 meV 2.8x107 @ 16.2 meV (polarized) | PG (002)2 Heusler (111)4 | Velocity selector | Yes | CRYOPAD option; high-magnetic-field compatible (including half-polarized measurements); the multiblade analyser option UFO is still in commissioning. CRG instrument. |
| NCNR | MACS | PG (002)1 | 5x108 @ 12 meV | PG (002)4 | Velocity selector | No | Unique multi-analyzer secondary spectrometer with 20 double-bounce PG (002) segments; dedicated cold source; polarization via 3He cells (vertical-field polarization only). |
| NCNR | SPINS to be replaced by POLAR | PG (002)3 | 1x107 @ 12 meV | PG (002) | Velocity selector | — | Analyzer composed of 11 individually controlled blades for horizontal focusing. To be replaced by POLAR, a design similar to MANTA. |
| MLZ | PANDA | PG (002)1 Cu (111)1 Si (111)2 Heusler (111)3 | 5.5x107 @ 14.7 meV (with PG filter) | PG (002)5 Heusler (111)5 | PG Be BeO | Yes | BAMBUS multianalyser under commissioning: 100 Q-E channels (20 x 5); high magnetic fields (coordinated with nearby instruments). Note: no cold neutrons at MLZ before 2027 (cold-source renovation). |
| MLZ | KOMPASS in commissioning | PG (002)1 (permanently polarized, dedicated V-cavity) | t.b.d. | PG (002)1 Heusler (111)5 | Velocity selector | Yes | Permanently polarized spectrometer: a V-cavity in the incident beam provides more than 96 % polarization between 1.5 and 15 meV. Cannot use magnets. |
| MLZ | LaDiff under construction (replaces MIRA) | PG (002)1 | 5x107 @ 9 meV 1x107 @ 9 meV (polarized) | PG (002)1 Heusler Multianalyser | Be PG | No | Versatile instrument enabling triple-axis and NRSE, complementary to TRISP; solid-state bender; extreme environments (pressure and magnetic fields); multianalyser with 155 Q-E channels (31 x 5). Upgrade of the former FLEXX (HZB) instrument. MIRA has been disassembled and removed. |
| ANSTO | SIKA | PG (002)1 | 5.66x106 @ 5.11 meV (flat monochromator, 10 mm virtual source; > 5x107 estimated with double focusing and the virtual source fully open) | PG (002)2 | Be | Yes | Polarisation analysis available through 3He. Flux measured by the gold-foil method. |
| PSI | CAMEA | PG (002)1 | 5x107 @ 7 meV (per mA of proton current) | PG (002), multiplexed | Be | Yes | CAMEA multi-analyzer incorporating the prismatic-analyzer concept for continuous coverage of Ef. |
| PSI | TASP | PG (002)3 | — | PG (002)5 | Be | No | Polarization option no longer available; a multiplexed secondary-spectrometer upgrade is expected. |
| HFIR | CTAX (CG-4C) to be replaced by MANTA | PG (002)3 | 3x106 @ 10 meV | PG (002)1 | Be or BeO | No | Will be taken out of the user program and replaced by MANTA after the Be-reflector outage at HFIR. |
| HFIR | MANTA planned | PG (002)1 PG (002)1 + polarizer | 1.5x108 @ 10 meV (simulated) | PG (002) | Velocity selector Be | Yes | Initial plan: secondary spectrometer interchangeable between a single analyzer/detector and an IRIS-type multiplexed spectrometer with up to 44 channels; a CAMEA-like upgrade is expected later. |
| JRR-3 | HER / HODACA (C1-1) | PG (002) | — | PG (002) | Be PG (lambda/2 kick-out) | No | Vertically focused monochromator; interchangeable backend: HER, a conventional TAS (one analyzer plus 3He detector), or HODACA, an IRIS-type multiplexed TAS (24 analyzer/detector sets at Ef = 3.635 meV). |
| JRR-3 | LTAS (C2-1) | PG (002) | — | PG (002) | Be BeO | No | Analyzer composed of 9 blades (individual rotation and horizontal translation to control the gap between blades) for horizontal focusing. |
- 1 variable horizontal and vertical focusing
- 2 fixed vertical and variable horizontal focusing
- 3 variable vertical focusing
- 4 fixed focusing
- 5 variable horizontal focusing
Thermal triple-axis spectrometers
| Facility | Instrument | Monochromator | Incident flux (n/cm²/s) | Analyzers | Polarized? | Filter(s) | Comments or unique capabilities |
|---|---|---|---|---|---|---|---|
| ILL | IN8 updated 2026-08-12 | PG (002) Cu (200) Si (111) Si (311) | 7x108 @ 14 meV 1x109 @ 35 meV 5x108 @ 52 meV 5x108 @ 35 meV 2.5x108 | PG (002) Cu (200) Si (111) | No | PG | FlatCone option; double-focusing monochromator and analyzers; automatic change between four monochromators; Si monochromators are elastically bent; secondary spectrometer upgraded in 2020 (ThermES: a compact single double-focusing analyzer and single detector, optimized to minimize parasitic background). |
| ILL | IN20 updated 2026-08-12 | Heusler (111) Si (111) | 1x108 @ 35 meV 2x108 @ 52 meV | Heusler (111) Si (111) PG (002) | Yes | Sapphire Velocity selector PG | CRYOPAD; PASTIS; FlatCone; high-magnetic-field compatible; velocity selector and sapphire filter; also uses 3He polarized filters (PASTIS set-up). |
| ILL | IN22 updated 2026-08-12 | PG (002) Heusler (111) Cu (111) | 3.5x107 @ 14 meV 6x107 @ 36 meV 1.3x107 @ 36 meV 1.9x107 @ 36 meV | PG (002) Heusler (111) | Yes | PG | Neutron spin-echo option (ZETA); CRYOPAD; high-magnetic-field compatible; 40 T pulsed-field option. CRG instrument. |
| NCNR | BT-7 | PG (002) Cu (220) | 1.8x108 @ 40 meV 6.1x107 @ 50 meV | PG (002) | Yes (3He) | Velocity selector PG | Double-focusing monochromator; high-magnetic-field compatible; polarized neutrons (3He cells); dilution-refrigerator compatible; position-sensitive detector option. |
| MLZ | PUMA | PG (002) Cu (220) Cu (111) Ge (311) | 1.8x108 @ 14.7 meV (10 mm virtual source) | PG (002) Ge (311) PG (002) 11-blade multi-analyzer | Yes (3He) | Sapphire | Automatic monochromator changer; double-focusing monochromators; analyzers with fixed vertical and variable horizontal focus. Unique multi-analyzer system for unpolarized multiplexing and uniaxial polarization analysis: FeSi deflectors after the sample separate spin-flip and non-spin-flip; event-mode data collection for stroboscopic measurements. |
| MLZ | TRISP under reconstruction | PG (002) | t.b.d. | PG (002) Heusler (111) | Yes | PG | Specialised in neutron resonant spin echo and Larmor diffraction; own dedicated dilution refrigerator. Under reconstruction (moving to the Neutron Guide Hall East). |
| ANSTO | Taipan | PG (002) Cu (200) | 1.8x108 @ 50 meV 6x107 @ 50 meV | PG (002) | Yes (3He) | PG (x3) | Double-focusing monochromator and analyzer; automatic monochromator changer; Be-filter spectrometer option. |
| PSI | EIGER | PG (002) PG (004) | 5.8x106 @ 13 meV | PG (002) | No | PG Sapphire | Double-focusing monochromator; analyzer with fixed vertical / variable horizontal focus. |
| HFIR | HB-1 (PTAX) | PG (002) Heusler (111) | 5.2x107 @ 41 meV | PG (002) Heusler (111) | Yes | PG | Vertically focused monochromator and horizontally focused analyzer; spherical neutron polarimetry option; neutron spin echo / Larmor diffraction. |
| HFIR | HB-3 (TAX) | PG (002) Si (111) Be (002) | 2x108 @ 40 meV 4x107 @ 40 meV 4.5x107 @ 68 meV | PG (002) | No | PG Velocity selector (planned) | Vertically focused monochromator and vertically focused analyzer. |
| HFIR | HB-1A (VERITAS) fixed incident energy | PG (002) double monochromator | — | PG (002) | No | PG | Fixed-incident-energy (Ei = 14.6 meV) thermal triple-axis spectrometer with very low background; not in the working-group comparison table. |
| JRR-3 | TAS-1 (2G) | Heusler (111) PG (002) | — | Heusler (111) PG (002) | Yes | PG Sapphire | Double-focusing Heusler monochromator/analyzer (fixed vertical). Polarized-neutron options: vertical (8.4 T) and horizontal (3 T) magnets, Helmholtz coil, CRYOPAD; 3He spin filter on ki. |
| JRR-3 | GPTAS (4G) | PG (002) | — | PG (002) PG (004) | No | PG | Double-focusing monochromator; analyzer with fixed vertical / variable horizontal focus. |
| JRR-3 | PONTA (5G) | PG (002) Heusler (111) | — | PG (002) Heusler (111) | Yes | PG Sapphire | Heusler flat; PG (002) vertically focused monochromator, V/H-focused analyzer; polarized diffraction with 3He spin filter and a small 2D PSD (commissioning). |
| JRR-3 | TOPAN (6G) | PG (002) Cu / Ge (future) | — | PG (002) | Yes (3He, half-polarized) | PG Sapphire | Monochromator and analyzer V/H-focused; 3He spin filter (commissioning); double monochromator (commissioning). |
| JRR-3 | HQR (T1-1) | PG (002) | — | PG (002) | Yes | PG | ki fixed; monochromator and analyzer vertically focused; supermirror polarizer option. |
| JRR-3 | AKANE (T1-2) | Ge (311) Ge (511) | — | PG (002) | No | — | Vertically focused (fixed); Ei fixed at 20 or 48 meV. |
| JRR-3 | TAS-2 (T2-4) | PG (002) Ge (311) | — | PG (002) Ge (311) | No | PG | Monochromator and analyzer vertically focused; Ge monochromator and analyzer (commissioning); non-magnetic shielding for high-field measurements (2 x 10 T vertical, 3 T horizontal). |
JRR-3 flux values were not included in the working-group table.
Working-group observations
Cold instruments
Capacity. Most facilities have at least two cold TAS instruments, reflecting community demand.
Capability. A standard configuration has emerged for the incident-beam optics of cold TAS instruments: focusing guides, double-focusing monochromators, a virtual source imaged at the sample with Rowland focusing geometry, and a polarization option (Heusler crystals or polarizing optics). The MANTA plan incorporates all of these; the POLAR instrument planned for the NCNR is similar in design. ThALES at the ILL is a world-leading cold TAS with a peak flux of 2.4×108 n cm-2 s-1 at 16 meV for PG (002). MACS has a higher flux (5×108) but a very large monochromator, hence large horizontal and vertical divergence, and a dedicated cold source that most facilities cannot provide. The simulated MANTA flux of 1.5×108 is competitive with the best instruments in the world. Massively multiplexed secondary spectrometers are the most exciting development: CAMEA is in operation today, and the IRIS concept developed in Japan with BNL and NIST is a newer multiplexing option likely to be implemented on MANTA first. Most, if not all, cold instruments are optimized for high magnetic fields combined with ultra-low temperatures.
Thermal instruments
Capacity. Most facilities have one thermal TAS; the ILL has three, HFIR two and JRR-3 seven.
Capability. Double-focusing monochromators, typically combined with a virtual source and Rowland-circle geometry, are used on most instruments worldwide: imaging the virtual source on the sample increases flux and reduces background. HB-1 and HB-3 are limited to vertical focusing by the horizontal divergence their beam tubes allow. Double-focusing analyzers, often fixed-vertical / variable-horizontal arrays, usually accompany them and should be part of any secondary-spectrometer redesign. Velocity selectors on IN20 and BT-7 reduce background and would benefit both polarized and unpolarized instruments. Most thermal instruments use a single analyzer and detector with horizontal focusing; even the new IN8 secondary spectrometer is optimized for that backend. A FlatCone-type option enables mapping of large regions of (Q, ω) space but is not a workhorse capability on any thermal TAS (about 20 % of IN8 experiments use it). IN20 and IN22 have polarized options.
Source: Thermal TAS Instruments.docx and Cold TAS Instruments.docx (International TAS Working Group, Instrumentation focus team, led by Adam Aczel; entries dated 2026), transcribed Oct 2026. Facility links verified Oct 2026 unless marked.