very cold moderator development at lens
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Very Cold Very Cold Moderator Moderator
Development at Development at LENSLENSDavid V. Baxter and W. M. David V. Baxter and W. M.
SnowSnow
Indiana UniversityIndiana UniversityA. Bogdanov, V. P. Derenchuk, H. Kaiser, C. M. Lavelle, M. A. Lone, M. B. Leuschner, H. O. Meyer, H. Nann,R. Pynn, N. Remmes, T. Rinckel, Y. Shin P. Sokol
OUTLINEOUTLINE
What/why is LENS?What/why is LENS? Neutronic design; what is unique Neutronic design; what is unique
about LENS?about LENS? Why is LENS ideal for very cold Why is LENS ideal for very cold
netron development?netron development? ConclusionsConclusions
What is LENS?What is LENS? Low Energy Neutron SourceLow Energy Neutron Source: based on : based on
low-energy (p,nx) reactions (Elow-energy (p,nx) reactions (Epp<13MeV) in <13MeV) in Be.Be.
The source is tightly coupled to a The source is tightly coupled to a cold cold moderatormoderator (e.g. solid CH (e.g. solid CH44 at 3K<T<30K). at 3K<T<30K).
LENS will have a LENS will have a variable pulse widthvariable pulse width (from ~10 (from ~10 s to more than 1.0 ms).s to more than 1.0 ms).
In long-pulse mode, LENS will have a In long-pulse mode, LENS will have a time-time-averaged cold neutron intensity suitable averaged cold neutron intensity suitable for SANS and other materials research.for SANS and other materials research.
A small number of scattering instruments A small number of scattering instruments will be developed to utilize these neutrons.will be developed to utilize these neutrons.
Budget : Budget : $14 M+ for construction;$14 M+ for construction; $1.5M/yr operations$1.5M/yr operations
LENS MissionsLENS Missions
Education
LENS
Materials research
Instrumentation development
The Facility Timeline-The Facility Timeline-SourceSource
Phase I (Early ’05: 7MeV, 7mA, 0.2% DF; 10Phase I (Early ’05: 7MeV, 7mA, 0.2% DF; 101111 n/s)n/s) Moderator studies: Benchmarking LENS performance, Moderator studies: Benchmarking LENS performance,
lower T, different materials, …lower T, different materials, … Simple diffraction experimentsSimple diffraction experiments
Phase II (July ‘07: 7MeV, 20mA, 0.5% DF; 10Phase II (July ‘07: 7MeV, 20mA, 0.5% DF; 101212 n/s)n/s) Moderator composition studies/neutronic improvements Moderator composition studies/neutronic improvements Start pushing to lower spectral temperatures ->VCNSStart pushing to lower spectral temperatures ->VCNS Initial SANS measurements Initial SANS measurements Total cross section measurementsTotal cross section measurements
Phase III (Jan. ’08: 13 MeV, 10Phase III (Jan. ’08: 13 MeV, 101313n/s)n/s) SANS studies SANS studies Development of SESAME instrumentDevelopment of SESAME instrument
Eventual power (13MeV, 50mA, 5% DF; 10Eventual power (13MeV, 50mA, 5% DF; 101414 n/s)n/s)
The Facility Timeline-The Facility Timeline-InstrumentsInstruments
SANSSANS Commissioning of final instrument July 2007Commissioning of final instrument July 2007 Experiments on confined water, polymer networks, Experiments on confined water, polymer networks,
fractal structures in geological samples, nano-fractal structures in geological samples, nano-particles Sept. 2007.particles Sept. 2007.
SESAMESESAME Magnetic component development Summer 2007Magnetic component development Summer 2007 Initial construction Oct. 2007Initial construction Oct. 2007 Initial commissioning Jan. 2008Initial commissioning Jan. 2008
Total elastic scattering instrumentTotal elastic scattering instrument Conceptual design Summer 2007Conceptual design Summer 2007 Possible construction to begin in Fall 2007 (not yet Possible construction to begin in Fall 2007 (not yet
fully funded)fully funded) Micro-SANSMicro-SANS
Seeking fundingSeeking funding Others …Others …
IUCFIUCF
IUCFIUCF
Facility Layout: 2005 - 2006Facility Layout: 2005 - 2006
Protons in linac: 15 Dec. Protons in linac: 15 Dec. 20042004
Proton Current
RFQ power
DTL Power
Neutrons in 2-D Neutrons in 2-D Detector:Detector:
15 Dec. 2004 15 Dec. 2004
Target Moderator Reflector Target Moderator Reflector (TMR)(TMR)
Target Moderator Reflector Target Moderator Reflector (TMR)(TMR)
Empty Moderator Empty Moderator SpectrumSpectrum
Detector at 5.7 m
Cryogenics inserted in Cryogenics inserted in TMR2TMR2
Moderator AssemblyModerator Assembly
Water
CH4
Al
Poly
PT-410
50 cm
Spectra Captured every 10 Spectra Captured every 10 MinutesMinutes
5-point low-pass filter applied
Phase II Structure of Phase II Structure of MethaneMethane
Circle at the centerrepresents an essentiallyfreely rotating molecule, all others are hindered rotors that librate in place.
Calculated Cross Section of Calculated Cross Section of Methane in Phase IIMethane in Phase II
From Grieger, J. Chem. Phys. 109, 3161 (1998).
Shin kernel: Total cross Shin kernel: Total cross sectionsection
Shin kernel- freq. Shin kernel- freq. spectrumspectrum
Shin kernel: 20 K CHShin kernel: 20 K CH44 spectraspectra
MCNP kernel (Y. Shin)MCNP kernel (Y. Shin)
Free Rotational and Phonon modesTunneling, Librational and Phonon modes
Methane-Argon Moderator: Excitation Methane-Argon Moderator: Excitation SpectrumSpectrum
Prager et. al., J. Chem. Phys. Vol. 95, 569-575 (1991)
Facility Layout: 2007Facility Layout: 2007
Scattering Hall Update: 2007Scattering Hall Update: 2007
Scattering Hall Update: 2007Scattering Hall Update: 2007
22 Feb 2007 29 March 2007
Pictures of Upgrade: Pictures of Upgrade: SANSSANS
LENS has been producing cold neutrons LENS has been producing cold neutrons for some time, and has recently done so for some time, and has recently done so at its second target station.at its second target station.
Neutronic performance is within 20% of Neutronic performance is within 20% of predictions at low E (cold and thermal).predictions at low E (cold and thermal).
Spectral temperature of <30K has been Spectral temperature of <30K has been realized, and work is underway to reduce realized, and work is underway to reduce this. This will be a major goal for the this. This will be a major goal for the project over the next 3 years.project over the next 3 years.
Future improvements to neutronics Future improvements to neutronics should increase cold flux by more than should increase cold flux by more than 30% (more on this tomorrow).30% (more on this tomorrow).
We have started to explore new materials, We have started to explore new materials, and are looking for more ideas in this and are looking for more ideas in this area!area!
ConclusionsConclusions
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