LENS at IUCF: Design and Instrumentation David V. Baxter Indiana University

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1 LENS at IUCF: Design and Instrumentation David V. Baxter Indiana University A. Bogdanov, D. Bossev, P. Chen (UIUC), V. P. Derenchuk, B. Jones (UIUC), H. Kaiser, C. M. Lavelle, M. A. Lone, M. B. Leuschner, R. Pynn, N. Remmes, T. Rinckel, W. M. Snow, P. Sokol

2 OUTLINE What/why is LENS? Unique aspects of the LENS design Neutronic Performance Fast/Thermal Cryogenic Instrumentation and Science Conclusions See also presentations: MP09, WP14, WP35

3 What is LENS? Low Energy Neutron Source: : based on low-energy (p,nx)) reactions (E( p <13MeV) in Be. The source is tightly coupled to a cold moderator (e.g. solid CH 4 at 4K<T<22K). LENS will have a variable pulse width (from ~10 μs s to more than 1.0 ms). In long-pulse mode, LENS will have a time- averaged cold neutron intensity suitable for SANS and other materials research. Beamlines devoted to materials research and neutron instrumentation development are under construction. Budget : $14.5 M (not including surplus etc.).

4 The Facility Timeline Phase I (Early 05: 7MeV, 7mA, 0.3% DF; 2x10 11 n/s) Moderator studies: Benchmarking LENS performance, lower T, different materials, Simple diffraction experiments Phase II (Fall 06: 7MeV, 20mA, 2% DF; 4x10 12 n/s) Total cross section measurements Moderator composition studies/neutronic improvements Emission time measurements Phase III (Summer 07: 13 MeV,, 1x10 13 n/s) Research with SANS Development of SESAME technique, RF spin flippers etc. Eventual power (13MeV, 50mA, 5% DF; n/s)

5 Missions Collaborative research program

6 IUCF

7 IUCF

8 Facility Layout: Spring 2006

9 Facility Layout: Spring 2007

11 Target Moderator Reflector (TMR)

13 Protons in linac: : 15 Dec DTL Power RFQ power Proton Current

14 Neutrons in 2-D 2 D Detector: 15 Dec :48

15 TMR with Cryogenic Insert

16 MCNP model

17 Moderator Intensity Measurement He3 Pancake Detector (k=4.6(2)x10-4 /A) Activation Foils Collimators Neutrons 570 cm

18 Empty Moderator Spectrum Detector at 5.7 m

Moderator Cryogenic Tests T4 T3 Dec. 2004 P(W) T4 (K) T3(K) 0.0 4.9 3.8 1.0 7.3 5.

19 Moderator Cryogenic Tests T4 T3 Dec P(W) T4 (K) T3(K) * * Estimated thermal load at 30kW

20 Cryostat insertion-- --April 2005

21 Moderator Assembly PT-410 Al CH 4 Poly 50 cm Water

22 400 first methane cooldown - 06Apr P [torr] vapor pressure curve normalized T3 data T [K]

23 Temperature dependence 5-point low-pass filter applied

24 Counts in Angstrom Range vs. Moderator Temperature

25 Emission Time NIM A239 (1985) Ikeda-Carpenter

26 Emission time distribution τ=360 μs (320 from MCNP)

27 Foil-Normalized Cold Spectrum YX X( mev) = Φ 0 n/cm 2 /uc ( E) de X Yx 6/02/ mev Yx 3/29/2006 Yx MCNP Ratio mev Ratio

28 Moderator Research Validation/development of scattering kernels: Methane phase II VCN/UCN candidate material investigations Total cross-section section measurements Bench tests of new ideas/geometries SNS poison burn-up up issues Be filter/reflector Spin equilibration

29 Calculated Cross Section of Methane in Phase II From Grieger, J. Chem. Phys. 109, 3161 (1998).

30 Total Cross Section From Dawidowski et al. Physica B271, p 212 (1999) elastic inelastic multiphonon

31 Total Cross Section From Dawidowski et al. Physica B271, p 212 (1999)

32 SANS

33 SANS Specifications/Science PFP = 8.0 m SFP 1.0 m to 4.5 m I = x 10 5 n/cm 2.s Q min min = 0.06 nm -1 : λ max =2.0 nm, 20 Hz SCIENCE: Structure of surface-functionalized functionalized nanoparticles Complex fluids (surfactants, clay slurries, ) Polymer networks Glasses/crystalization See poster: WP 14

34 SESAME: a spin interferometer + z - The magnetic regions act as birefringent areas for spin-up and spin-down components of the incident state.

35 SESAME: a spin interferometer + z - The magnetic regions act as birefringent areas for spin-up and spin-down components of the incident state. Final polarization state directly probes corrleations between 2 paths.

36 SESAME: a spin interferometer + z - The magnetic regions act as birefringent areas for spin-up and spin-down components of the incident state. To first order, the final polarization state is independent of the trajectory.

37 SESAME High precision without collimation! Real-space probe; out to several microns. Delft group has demonstrated an analytical approach to multiple scattering corrections: STRONG SCATTERERS WELCOME!

38 Conclusions LENS has produced cold neutrons and is starting its work on science, education, and technology Neutronic performance is in good agreement with model predictions at low E (thermal), but differs significantly at high E (MeV( MeV). Future improvements to neutronics should increase cold flux by more than 30% (beyond increases from accelerator improvements). Over the next year we will be conducting moderator research, initiating SANS studies, and starting to investigate various options for SESAME.

39 Fast Neutron Measurements Ni foil Silicon Damage

40 Measured Fast Flux Summary, Empty or Poly Moderator Fast, > ~3 MeV,, Ni, S 1 MeV equiv., 2N2222A measured 10 7 n/s/cm 2 MCNP 10 7 n/s/cm / / Measured/ Simulation ma peak, 150 μs pulse width, 20 Hz rep rate (Oct 2005) Measured fast flux is ~45% lower than predicted Gamma dose negligible (TLD: 1.5 krad in 24h) One 8h shift: n/cm 2 thermal n/cm 2 fast n/cm 2 1 MeV equiv.

41 Cryogenics Cryogenic gallery Cryogenic vacuum insert

42 Thermal Flux XY Position Dependence (MCNP)

43 Spectra Captured every 10 Minutes 5-point low-pass filter applied

Foil Normalized Cold Spectrum YX X( mev) = Φ 0 n/cm 2 /uc ( E) de X Yx 6/02/2005 10

44 Foil Normalized Cold Spectrum YX X( mev) = Φ 0 n/cm 2 /uc ( E) de X Yx 6/02/ mev Yx 3/29/2006 Yx MCNP Ratio mev Ratio

45 MCNP model

46 Emission Time Experiment Equipment

LENS as a Resource for Cold Moderator Development David V. Baxter Indiana University

LENS as a Resource for Cold Moderator Development David V. Baxter Indiana University A. Bogdanov, J. M. Cameron, P. Chen (UIUC), V. P. Derenchuk, B. Jones (UIUC), H. Kaiser, C. M. Lavelle, M. A. Lone,