Polarized Neutrons in ANSTO – From LONGPOL to Pelican, Taipan, Sika, Platypus and Quake Dehong Yu and Shane Kennedy Bragg Institute, ANSTO, Australia

LONGPOL (1973-~1980) Location/ beamtube HIFAR, radial tube with  =5.9 mm Monochromator Velocity selector with =3.6 Å &  =13 % Polarizer & Analyzer Iron Filters with t =6 mm in H =1 T, P =33 % Spin flipper R-F coil with =0.5 MHz in H =17 mT,  =98 % Detector 4 x  =2” BF 3 tubes (RSN 44A) in parallel Initial purpose: studies of magnetic diffuse (static) scattering Design criteria: separate magnetic & nuclear components, high intensity, low ‘q’ resolution

LONGPOL – Later Development Polarizer Spin flipper

LONGPOL – Energy Analysis Flipper drive pulse sequence Intensity variation for non-spin-flip scattering Intensity variation for spin-flip scattering Cross-correlation of intensity with drive sequence Direct separation of spin-flip and non-spin flip scattering. TOF – energy analysis Modulation of neutron polarization using pseudo-random pulse train to drive spin flipper, Cross-correlation of intensity with the drive sequence

LONGPOL - Science Served for more than 30 years Produced important scientific studies including:  spin glass nature of Cu 95 Mn 5  short range order in  -MnNi  flux relaxation in high Tc superconductors  crystal field transitions in PrAl 3  magnetic phase of Fe 2 MnSi  magnetic domains in amorphous Fe-Zr

Lessons from LONGPOL Fix Geometry means non-flexibility Compact design means  Difficulty to access  Limitation to different sample environment Low flux, long data acquisition time Statistic chopper  Relative high background  Only works well for strong signals

New Instruments in OPAL Wombat (HIPD) Kowari (RS) Echidna (HRPD) Koala (QLD) Platypus (Ref) Quokka (SANS) Taipan (TAS) Sika (CTAS) Pelican (TOFPAS)

Pelican - TOFPAS

TOF-PAS Preliminary Specifications Design goals: Inelastic & quasi-elastic neutron spectroscopy – time focusing TOF spectrometer (Comparable w/- ILL) + Polarization analysis capability (Comparable w/- ILL) Preliminary Specs. – to reach the design goals Neutron Wavelength: 2.4 Å – 6.3 Å, (14.2 meV – 2.1 meV) Energy resolution: 50 µeV to 350 µ eV (~2.5%) Q range: 0.05 Å Å -1 Solid angle: ¾ Steradians (non-pol), ¼ Steradians (pol) Neutron flux at sample: ~ 8 x10 6 n/cm 2 /s at 3.7 Å, (full beam)

Current Status - Stage 1 Conceptual design finished, Dance floor installed Monochromator stage ordered, Beam Monitor ordered Monochromator shield arrived, Installation started 40° < 2Θ < 140°; 2.1 meV < Ei < 14.2 meV, (HOPG)

The TOF-PAS Dance floor The TOF-PAS granite dancefloor (area = 38 m 2 ) -sufficient for 5m flight path from monochromator to detector over all possible take-off angles. 5.4 metre

Stage 2 Phase 1 - Conceptual Design General considerations Multiple HOPG monochromator (vertical or double focusing), mosaic about 0.5 o Wavelength filter: Cold Beryllium filter for λ above 4.1 Å and a HOPG diffraction filter for λ < 4.1 Å. Beam Chopper: Double Stage Fermi Chopper Sample stage: standard A-Z system Collimation system (after sample) Detector: 250 PSD 3 He tube (Φ = 12.5 mm and length = 1m), cover about ¾ Steradian (3.125 m 2 ) Spectrometer Tank: Vacuum or gas filled (He or Ar ?) Energy resolution:  E/E i = 2.5% (50µeV to 300 µeV)

Polarization Analysis Polarizer: Supermirror bender Spin Flipper: Mezei flipper; Analyzer: Supermirror bender, and 3 He polarizing filter is also considered if it becomes available in ANSTO. Guide field: to be designed Polarizing benderAnalyzing bender: (8 elements)

Polarization Analysis

Budget Estimation – Stage 2 ItemCost (A$ K) Sub-total Stage 2 Capital4,792 HR789 Running254 Total estimate for stage 2 Contingency (20%) 5,835 1,167 Total7002

Project Schedule Stage 1: Front End Monochromator shield, stage and dance floor Stage 2: Whole Instrument Schedule: Standard components (stage 1) Conceptual design Engineering design Manufacture & procure Assemble & install Commissioning

-TAS Incident E: 5 meV – 120 meV Energy Transfer: up to 80 meV Scattering angle 2Ө m : 15 o – 85 o Analyzer scattering angle 2Ө A : -110 o – 110 o Double focusing Mono. and Analyzer.

TOF-Neutron Reflectometer Horizontal sample Solid –solid Liquid – solid Polarization option

Transmission Polarizer – Ref. and SANS iron yoke adsorbing borated glass (Non-magnetic) m=3 supermirrors Permanent magnets 50 mm Elevation looking along the beam (m=3) FeSi polarizing supermirror on both sides of thin Si wafers Elevation perpendicular to the beam 1200 mm  = 3 to ~17 Å RF spin flippers before & after sample

Sample environments Cryo-free cryo- furnace 4 K  800 K Arrived One system is commissioned Liq. He cryostat 1.4 K  300 K Arrived 3 He cryostat insert ~300 mK Dilution refrigeration ~30 mK 7.4 Tesla cryo- free cryo-magnet Commissioned in ANSTO 5 Tesla cryo- free cryo- magnet (N.Z. design for Reflectometry/ SANS) Under design HMI’s 15 Tesla cryomagnet. Proposed

TOFPAS - (Q,ω) TOF-PAS SikaTaipan Heavy fermions Molecular & lattice vibrations Critical scattering Spin waves Molecular rotations