P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 1 Ultra-Cold Neutron Sources: from the past to the future UCN – properties and keystones early sources sD 2 at PSI, TUM, Mainz, LANL, NCSU, and ILL sLHe at ILL, TUM, and RCNP, and SNS thanks to the beautiful slides of J. Bazin, D. Bondoux, A. Frei, R. Gähler, P. Harris, W. Heil, P. Huffman, T. Ito, Y. Masuda, J.M. Pendlebury, A. Pichlmaier, C. Plonka, R. Stöpler, M. van der Grinten, A. Young, O. Zimmer, and R. Golub (book) turbine at ILL, PNPI
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P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 1
Ultra-Cold Neutron Sources:from the past to the future
UCN – properties and keystones
early sources
sD2 at PSI, TUM, Mainz, LANL, NCSU, and ILL
sLHe at ILL, TUM, and RCNP, and SNS
thanks to the beautiful slides ofJ. Bazin, D. Bondoux, A. Frei, R. Gähler, P. Harris, W. Heil, P. Huffman, T. Ito, Y. Masuda, J.M. Pendlebury,
A. Pichlmaier, C. Plonka, R. Stöpler, M. van der Grinten, A. Young, O. Zimmer, and R. Golub (book)
turbine at ILL, PNPI
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 2
Properties of UCN
λUCN ~ 1000 Å
Ekin (~ 5 ms-1) = 100 neV (10-7 eV)
~ 10-7 eV / TeslaMagnetic field∆E= μn B
~ 10-7 eV / MeterGravity∆E=mn g ∆h
~ 10-7 eVFermi potential
UCN are totally reflected from suitable materials at any angle of incidence, hence storable!
UCN are furthermore storable by gravity and/or magnetic fields
Interaction with matter:UCN see a Fermi-Potential EF
EF ~ 10-7 eV for many materials, e.g.
- beryllium 252 neV- stainless steel 200 neV
Long storage and observationtimes possible (up to several minutes)!
High precision measurements ofthe properties of the free neutron
(lifetime, electric dipole moment, gravitational levels)
That’s why we are here!
TUCN ~ 2 mK
Ultracold neutrons, that is, neutrons whose energy is so low that they can be contained for long periods of time in material and/or magnetic bottles
V n
V n < V c r it
V n > V c r it
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 3
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 4
UCN discovery
… by extracting neutrons from the low energy tail of the Maxwellian distribution in the source
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 5
Reactor core
Cold source
Vertical guide tube
Neutron turbineA. Steyerl (TUM - 1985)
The UCN/VCN facility PF2
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 6
The Vertical Cold Source (VCS)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 7
Steyerl turbine (2nd generation)at PF2 / ILL10 years later
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 8
Principle of the neutron turbine
TOF data as a function of axial velocity
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 9
The PF2 beam facility
PF2: Physique Fondamentale 22nd installation for fundamental physics
4 positions for Ultracold Neutrons (UCN)
- MAM [14x10 cm2]
- EDM [7x7cm2]
- UCN [10x5 cm2]
- TES [4x4 cm2]
v = 5 ms-1
ρ = ~50 cm-3 (at the experiment)
1 position for Very Cold Neutrons (VCN)
v = 50 ms-1
Φ = 108 cm-2 s-1- VCN beam
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 10
Other versions of the neutron turbine
Radial turbine, Kashoukeev et al (1975), Bulgaria
12 flat mirrors like the fins of a paddle wheel~ 1000 rpm
Super-mirror turbine, Utsuro et al (1988), Kyoto
less turbine blades (32 instead of 690)flat (instead of curved) mirrorsIncreased yield for velocities above UCN range
“Crystal” turbine, Dombeck et al (1979), Brun et al (1980), ANLLater revisisted in LANSCE at LANLBragg reflection from a moving crystalLarger velocity neutrons can be reflected
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 11
Source of polarized cold and UCN at PNPI
Φth ~ 2x1014 n cm-2 s-1
ρ ~ 16 cm-3
(1 l)
(Al +58Ni(Mo))
(1 l)
UCN yield as a function of source temperature (hydrogen)Highest gain (66) with D2 at 17K
see next talk by A. Serebrovon the impressive activities at PNPI in this field
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 12
UCN source using horizontal extraction
Dimitrovgrad, Kosvintsev et al (1977)
UCN are produced in a water cooled convertor of zirconium hydridelocated inside a stainless steel guide with several bends
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 13
All the details you will find in W. Heil’s talk later in this session!!
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 24
LANSCELANSCE
UCN Source
Proton Linac(Los Alamos Neutron Science CEnter)
FP12
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 25
Schematic
Graphite
Tungsten targetBeryllium
UCN Guide to experiment
Polyethylenemoderator
Flapper valve
SD2 volume
58Ni coated wall
7 in.
1 m
(T. Ito)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 26
0
10
20
30
40
4 8 12 16
τ SD
(mse
c)
T (K)0 0.1 0.2 0.3 0.4
Para Fraction
Measured for the first time: UCN lifetime in SD2
τpara = 1.2 ± .14 (stat) ± .20 (syst)
C. L. Morris et al., Phys. Rev. Lett. 89, 272501 (2002)
PhD Thesis: Chen-Yu Liu
confirmed: F. Atchison et al., Phys. Rev. Lett. 95, 182502 (2005)
Experimental surprise: UCN lifetime depends strongly on
para-D2 content
Prototype Source Key Results
(T. Ito)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 27
Compare to previous record for bottled UCN of 41 UCN/cm3 (at ILL) A. Saunders et al., Phys. Lett. B 593, 55 (2004)
confirmed: F. Atchison et al., Phys. Rev. C. 71, 054601 (2005)
After learning how to control
para-D2concentration
Within 50% of expected fluxes (MCNP simulation)
Measured: 466 ±92 UCN/cm3/μC
Predicted: 750 UCN/cm3/μC
Very High Densities Achieved
(T. Ito)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 28
Area B Schematic
UCNA betaspectrometerSD2 UCN Source
Proton beam
Polarizermagnets
(T. Ito)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 29
Status & Plans• 2005 run
– Source & UCNA experiment commissioning– The UCN flux measured inside the source reasonable but the flux
coming out of the shielding package substantially lower than expectation, and the spectrum very soft, indicating that the Fermi potential of the guide coating is low.
• 2006 run– Guide tube before PPM was replaced with stainless steel tube– New source insert (flapper valve) was built and tested– Increased UCN flux observed, however the flapper valve was
unreliable• 2007 run
– Run started in mid June– A new source insert will be installed– Additional polyethylene moderator was installed– Additional proton beamline diagnostic was installed– Continue with the source and experiment commissioning and data
taking for beta asymmetry experiment
(T. Ito)
Listen carefully to A. Young’s talk on 5th July!
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 30
Development of an Ultracold Neutron Source at the PULSTAR Reactor
Albert R. YoungNorth Carolina State University
(courtesy of A. Young)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 31
NCSU PULSTAR Reactor
• Sintered UO2 pellets• 4% enriched• 1-MW power• Light water moderated and
cooled • Just issued a new license for
about 10 years of operation
Source located in thermal column (outside reactor proper)
28 ft
Core
(courtesy of A. Young)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 32
Source Schematic
• Lead shield -reduce gamma heating, maintain reactivity
• Floodable Helium Nose Port• Heavy Water Thermal
Moderator• CH4 cold moderator, 1 cm
thick cup around SD2• 1 liter SD2• 18 cm diameter, 58Ni-coated
guides
(courtesy of A. Young)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 33
UCN Transport Simulation
Transport efficiency around bend and down approx 3 m of guide
~ 30% (no foils)~15% (Al isolating foil)
Y.-P. Xu and A. R. Young
(courtesy of A. Young)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 34
Expected Results at 1 MW
• 5x1011 n/cm2/s CN Flux in Deuterium• 0.8x104 – 1.5x104 n/cm3/s UCN Production• ~250-400 UCN/cm3 Limiting Density • >30 UCN/cm3 Useful Density
(courtesy of A. Young)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 35
• Funding obtained from DOE INIE program starting in 2003 and NSF in 2004 (NSF provided equipment money)
• First licensing amendments complete, full source safety analysis and license amendment under way (3 person team)
• New scattering kernels for cryogenic materials developed
• Validation of Monte Carlo model of thermal flux in graphite thermal column (now removed to make room for new source)
• New nose port designed, constructed and test fitP li i i i d i f ti l
Current Activities
(courtesy of A. Young)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 36
8.9 A neutrons are needed to create UCN in 4He
(M. Pendlebury)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 37
Superthermal sourceUCN storage cryostat
Golub et al (1983), at ILL
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 38(Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 39
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 40
Calculating the UCN density in the super-fluid 4He
The UCN production rate per unit volume = (4.55 ±0.25) x10−8 (dΦ/dλ) at 8.9 Å.
C. A. Baker et al, NIM A, 308 (2003) 67.
Thus, for (dΦ/dλ) at 8.9 Å = 2.5 x10+8 /cm2/s/Å,
the production rate in the superfluid is 11 UCN/cm3/s.
If the UCN mean survival time in the super-fluid is 150 s,
then, after having the cold beam on for 150 s,
the UCN density will be 11 x 150 x (1− e−1) = 1080 /cm3
(M. Pendlebury)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 41
H17
requirement for He source: λ = 8.93 Å ± 1%Crystal: Intercalated graphite K-IHOPG stage 1
reflected beam crosses above H18
Cryo-EDM
Area ≈ 100 m2
D9
D3H18
New H17 for FIGARO and Cryo-EDM; general setup; top view (ILL reactor hall)
80× 80 for Cryo-EDM
15× 80 for FIGAROH171
H171: 15× 80 for FIGARO
beam stop for CRYO-EDMAxial separation to H16 and H18 ≈ 70 cm
H172 absorberGRANIT
(R. Gähler)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 42(O. Zimmer)
superthermal UCN production at MEPHISTO (FRM-II):
"HELIMEPHISTO“, soon at the ILL
… much more details and the latest and “hotest”news will be given by O.Zimmer just after the coffee break!
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 43(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 44(Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 45(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 46(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 47(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 48(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 49(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 50(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 51(courtesy of Y. Masuda & O. Zimmer)
compressed Al2O3 powder (50 nm)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 52(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 53(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 54(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 55(courtesy of Y. Masuda)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 56
SNS at ORNLSNS at ORNL1.4 MW Spallation Source1.4 MW Spallation Source
(P. Huffman)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 57
FNPB FNPB BeamlineBeamline
Double monochromator
Selects 8.9 Å neutronsfor UCN via sLHe
(P. Huffman)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 58
ULTRA COLD SOURCEintegrated in a possible 3rd cold neutron source at the ILL
(J. Bazin)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 59
• SD2 behaviour under radiation
• In pile cryostat concept
• UCN storage tube
• Overall integration
• Preparation of detailed design phase
SD2 UCN source at ILL: feasibility study
(courtesy of D. Bondoux)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 60
γ and n fluxes --> radiolysis phenomena
Water Ice
Sudden releaseof stored energy
Experimental investigations
Water & heavy water icesolid methanesolid mesitylene…
but not for solid deuterium
Major issues for a SD2 UCN source
Level of released energy / « crystal » quality?Period of occurrence / experiments?
UCN source at ILL: SD2 behaviour under radiation
(courtesy of D. Bondoux)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 61
UCN source at ILL: SD2 cryostat concept
Helium
“Ejection” whencooling off
Mini D2 (old design)
~ + 2 KSD2
Inner skin
Outer skin
Outer skinHe flow
Inner skin (coated Al?)
He flow
Helium
Plateexchanger
1/8 model
~ + 1 K
SD2
Exchanger skin, Be
Exchanger skin
SD2
He flow
A promising concept but a challenging technology!
(courtesy of D. Bondoux)
P. Geltenbort Ultra-Cold and Cold Neutrons: Physics and Sources, St. Petersburg --> Moscow, 1 - 7 July 2007 62
UCN source at ILL: SD2 cryostat concept
solidliquid (19 K)
CN flux (40 K) ~ 2.4e13 n/cm2-s
ILL concept advantages:
- reduced temperature excursion from He to SD2- reduced heating power (ratio ~ 5) due to cryostat reduced mass (geometry & material)- less thermo-mechanical constraints when re-heating SD2 (SD2 thermal expansion)