LENS at IUCF: Design LENS at IUCF: Design and Instrumentationand Instrumentation

David V. BaxterDavid V. Baxter

Indiana UniversityIndiana 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

OUTLINEOUTLINE

What/why is LENS?What/why is LENS?Unique aspects of the LENS design Unique aspects of the LENS design NeutronicNeutronic PerformancePerformance

Fast/ThermalFast/ThermalCryogenicCryogenic

Instrumentation and ScienceInstrumentation and ScienceConclusionsConclusionsSee also presentations: See also presentations: MP09, WP14, WP35MP09, WP14, WP35

What is LENS?What is LENS?

Low Energy Neutron SourceLow Energy Neutron Source: based on low: based on low--energy energy ((p,nxp,nx) reactions () reactions (EEpp<13MeV) in Be.<13MeV) in Be.The source is tightly coupled to a The source is tightly coupled to a cold moderatorcold moderator(e.g. solid CH(e.g. solid CH44 at 4K<T<22K).at 4K<T<22K).LENS will have a LENS will have a variable pulse widthvariable pulse width (from ~10 (from ~10 μμs to more than 1.0 ms).s to more than 1.0 ms).In longIn long--pulse mode, LENS will have a pulse mode, LENS will have a timetime--averaged cold neutron intensity suitable for averaged cold neutron intensity suitable for SANS and other materials research.SANS and other materials research.BeamlinesBeamlines devoted to materials research and neutron devoted to materials research and neutron instrumentation development are under construction.instrumentation development are under construction.Budget : Budget : $14.5 M (not including surplus etc.).$14.5 M (not including surplus etc.).

The Facility TimelineThe Facility Timeline

Phase I (EarlyPhase I (Early’’05: 7MeV, 7mA, 0.3% DF; 2x1005: 7MeV, 7mA, 0.3% DF; 2x101111 n/sn/s))Moderator studies: Benchmarking LENS performance, lower Moderator studies: Benchmarking LENS performance, lower T, different materials, T, different materials, ……Simple diffraction experimentsSimple diffraction experiments

Phase II (Fall Phase II (Fall ’’06: 7MeV, 20mA, 2% DF; 4x1006: 7MeV, 20mA, 2% DF; 4x101212 n/sn/s))Total cross section measurementsTotal cross section measurementsModerator composition studies/Moderator composition studies/neutronicneutronic improvements improvements Emission time measurements Emission time measurements

Phase III (Summer Phase III (Summer ’’07: 13 07: 13 MeVMeV, 1x10, 1x101313n/s)n/s)Research with SANS Research with SANS Development of SESAME technique, RF spin flippers etc.Development of SESAME technique, RF spin flippers etc.

Eventual power (13MeV, 50mA, 5% DF; 10Eventual power (13MeV, 50mA, 5% DF; 101414 n/sn/s))

MissionsMissions

Collaborative researchprogram

IUCFIUCF

IUCFIUCF

Facility Layout: Spring 2006Facility Layout: Spring 2006

Facility Layout: Spring 2007Facility Layout: Spring 2007

Target Moderator Reflector Target Moderator Reflector (TMR)(TMR)

Protons in Protons in linaclinac: 15 Dec. 2004: 15 Dec. 2004

Proton Current

RFQ power

DTL Power

Neutrons in 2Neutrons in 2--D Detector:D Detector:15 Dec. 2004 22:4815 Dec. 2004 22:48

TMR with Cryogenic InsertTMR with Cryogenic Insert

MCNP modelMCNP model

Moderator Intensity Moderator Intensity MeasurementMeasurement

Activation FoilsHe3 “Pancake” Detector

(k=4.6(2)x10-4 /A)

Collimators Neutrons570 cm

Empty Moderator SpectrumEmpty Moderator Spectrum

Detector at 5.7 m

Moderator Cryogenic TestsModerator Cryogenic Tests

P(W) T4 (K) T3(K)0.0 4.9 3.81.0 7.3 5.92.0* 8.9 7.23.0 10.2 8.34.0 11.3 9.1 5.0 12.3 10.0

T3T4

Dec. 2004

* Estimated thermal load at 30kW

Cryostat insertionCryostat insertion----April 2005April 2005

Moderator AssemblyModerator Assembly

Water

CH4

Al

Poly

PT-410

50 cm

first methane cooldown - 06Apr05

0

50

100

150

200

250

300

350

400

88 90 92 94 96 98 100 102T [K]

P [to

rr] vapor pressure curve

normalized T3 data

Temperature dependenceTemperature dependence

5-point low-pass filter applied

Counts in 10Counts in 10--20 Angstrom Range vs. 20 Angstrom Range vs. Moderator TemperatureModerator Temperature

Emission TimeEmission TimeNIM A239 (1985) 536NIM A239 (1985) 536--544 Ikeda544 Ikeda--CarpenterCarpenter

τ=360 μs (320 from MCNP)

Emission time distributionEmission time distribution

FoilFoil--Normalized Cold SpectrumNormalized Cold Spectrum

( )

0

( )X meV

XY E dE= Φ∫

XX YxYx

6/02/20056/02/2005

YxYx

3/29/20063/29/2006

YxYx

MCNPMCNP

RatioRatio

10 10 meVmeV 32.232.2 35.135.1

72.672.6

.48.48

47.447.4 .68.68

125 125 meVmeV 64.664.6 99.399.3 .65.65

RatioRatio .48.48 .48.48

n/cm2/uC

Validation/development of scattering Validation/development of scattering kernels:kernels:

Methane phase IIMethane phase II

VCN/UCN candidate material investigationsVCN/UCN candidate material investigations

Total crossTotal cross--section measurementssection measurements

Bench tests of new ideas/geometriesBench tests of new ideas/geometriesSNS poison burnSNS poison burn--up issuesup issues

Be filter/reflector Be filter/reflector

Spin equilibrationSpin equilibration

Moderator ResearchModerator Research

Calculated Cross Section of Calculated Cross Section of Methane in Phase IIMethane in Phase II

From Grieger, J. Chem. Phys. 109, 3161 (1998).

Total Cross SectionTotal Cross SectionFrom Dawidowski et al. Physica B271, p 212 (1999)

elastic

multiphonon

inelastic

Total Cross SectionTotal Cross Section

From Dawidowski et al. Physica B271, p 212 (1999)

SANSSANS

PFP = 8.0 m SFP 1.0 m to 4.5 mPFP = 8.0 m SFP 1.0 m to 4.5 mI = 0.2 I = 0.2 –– 1 x 101 x 1055 n/cmn/cm22.s .s

QQminmin = 0.06 nm= 0.06 nm--1 1 : : λλmaxmax=2.0 nm, 20 Hz=2.0 nm, 20 Hz

SCIENCE:SCIENCE:Structure of surfaceStructure of surface--functionalized functionalized nanoparticlesnanoparticlesComplex fluids (surfactants, clay slurries, Complex fluids (surfactants, clay slurries, ……))Polymer networksPolymer networksGlasses/Glasses/crystalizationcrystalization

See poster: WP 14See poster: WP 14

SANS Specifications/ScienceSANS Specifications/Science

SESAME: a spin interferometerSESAME: a spin interferometer

+ -z

•The magnetic regions act as birefringentareas for spin-up and spin-down componentsof the incident state.

SESAME: a spin interferometerSESAME: a spin interferometer

+ -z

•The magnetic regions act as birefringentareas for spin-up and spin-down componentsof the incident state. Final polarization state directly probes corrleations between 2 paths.

SESAME: a spin interferometerSESAME: a spin interferometer

+ -z

•The magnetic regions act as birefringentareas for spin-up and spin-down componentsof the incident state. To first order, the finalpolarization state is independent of the trajectory.

High precision without collimation!High precision without collimation!

RealReal--space probe; out to several microns.space probe; out to several microns.

Delft group has demonstrated an analytical Delft group has demonstrated an analytical approach to multiple scattering corrections: approach to multiple scattering corrections: STRONG SCATTERERS WELCOME!STRONG SCATTERERS WELCOME!

SESAMESESAME

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

ConclusionsConclusions

Fast Neutron MeasurementsFast Neutron Measurements

Ni foil

SiliconDamage

Measured Fast Flux Summary,Empty or Poly Moderator

measuredmeasured

101077 n/s/cmn/s/cm22

MCNPMCNP

101077 n/s/cmn/s/cm22

Measured/Measured/

SimulationSimulation

Fast, > ~3 Fast, > ~3 MeVMeV, Ni, S, Ni, S

3.29+/3.29+/--.21.21 5.95.9

18.118.11 1 MeVMeVequiv., equiv., 2N2222A2N2222A

10.50+/10.50+/--.45.45

0.560.56

0.580.58

Gamma dose negligible (TLD: 1.5 krad in 24h)Measured fast flux is ~45% lower than predicted7.3 mA peak, 150 μs pulse width, 20 Hz rep rate (Oct 2005)

2.3 . 1012 n/cm2 thermal 1.0 . 1012 n/cm2 fast 2.9 . 1012 n/cm2 1 MeV equiv.

One 8h shift:

Cryogenic vacuum insert

Cryogenics

Cryogenic “gallery”

Thermal Flux XY Position Thermal Flux XY Position Dependence (MCNP)Dependence (MCNP)

Spectra Captured every 10 MinutesSpectra Captured every 10 Minutes

5-point low-pass filter applied

Foil Normalized Cold SpectrumFoil Normalized Cold Spectrum

( )

0

( )X meV

XY E dE= Φ∫

XX YxYx

6/02/20056/02/2005

YxYx

3/29/20063/29/2006

YxYx

MCNPMCNP

RatioRatio

10 10 meVmeV 32.232.2 35.135.1

72.672.6

.48.48

47.447.4 .68.68

125 125 meVmeV 64.664.6 99.399.3 .65.65

RatioRatio .48.48 .48.48

n/cm2/uC

MCNP modelMCNP model

Emission Time ExperimentEmission Time ExperimentEquipmentEquipment