nEDM with Spallation UCN Source of He-II Y. Masuda (KEK), April 15, - - PowerPoint PPT Presentation
nEDM with Spallation UCN Source of He-II Y. Masuda (KEK), April 15, 2016, Mainz + 10 -13 cm n d n Neutron Spin - CP violation shifts charge distribution EDM cell Nuclei in matter 1 nEDM upper limit Theoretical History of nEDM
1
Mainz
Neutron
10-13 cm
Spin
CP violation shifts charge distribution
μn
EDM cell
10-26 10-28 10-24 10-22 10-20
e cm
10-30
Theoretical predictions
1950 2000 Cold n beam UCN
History
1950
2
10-20 10-22 10-24 10-26 e cm
Year upper limit
ρ = 1 UCN/cm3 Pendlebury 800 UCN/cm3 A He-II UCN source
E 10 kV /cm Bo 1 μT spin s
S matrix: phase operator U(t) = exp{i(μ·B0 + dn∙E)∙t/h} rotation operator μ, dn ∝ s
EDM cell
1st π/2 ωotc precession phase
3
(ω-ωo)tc ωtc RF phase 2nd π/2
Statistical error: 1. N, He-II spallation UCN source
10-27~10-28 e cm Systematic error: 3. B0 monitor, 129Xe co-magnetometer
10-27 e cm
The difference (ω-ωo)tc is measured by polarimetry: δdsta = h/{2PnEtc√N}
20K D2O
Ramsey resonance EDM cell
VF(guide)= 210 neV
He-II Vacuum SCM
Al foils
UCN valve is closed during production
μB0(3.5T) = 210 neV > VF(Al)=54 neV
10K D2O 300K D2O
12L He-II
Target
Polarized UCN
PUCN~100%
Spin analyzer
δdsta = h/{2PnEtc√N}
N∝production rate∝Ep×Ip
E
Bo
proton beam
N∝production time∝τs
Rotary valve
ρpol = 800 UCN/cm3 in EDM cell of Ec = 90 neV
5
ρ t τs ρ = Pτs P P (production rate) = ∫∫dEindEUCN
Nσ(Ein→EUCN)dΦn(Ein)/dEin
∝Ep×Ip Energy deposit upon spallation reaction
target 10K D2O He-II
Target He-II 10K D2O 400MeV×1μA 0.1 W 4.4 W 400MeV×10μA 1 W 44 W 500MeV×40μA 5 W 220 W (our goal)
He-II bottle wall is dominant
Proton beam power
p beam →
6
250 s 123 s 64 s 36 s 600 s 0.8 K 0.9 K 1 K 1.1 K 1.2 K 1370 s 0.7 K He-II phonon up-scattering Golub, 1983
= 174 s τβ = 886 s (β decay) τph = 600 s at 0.8 K τw = 246 s (wall loss)
τ3He = 28 ms at 3He/4He = 1.4x10-6
= 3900 s at 3He/4He = 10-11
τs (UCN lifetime) = 1/{1/τβ + 1/τ3He + 1/τw + 1/τph}
We are aiming at τs = 100 s
= 174 s
20K D2O
1K pot
3He
pumping
PulseTube cryostat
4He pumping
8L pot
Liq.He
Isopure
4He 3He
EDM cell
3He
cryostat
10K D2O UCN valve SCM polarizer UCN detector
Door valve
3He-4He
Heat exchanger 300K D2O
7
Target
Heating
γ heating are conducted through He-II Heat load is removed upon
3He evaporation.
Proton beam Heat power He-II 400MeV×1μA 0.1 W 400MeV×10μA 1 W 500MeV×40μA 5 W
3He flow
0.032 mol/s 0.16 mol/s
3He pumping
1K pot
PulseTube
4He pumping
8L pot
Liq.He
needle valves
3He
Isopure
4He
3He
pumping
3He-4He
heat exchanger
He-II
20K D2O
10K D2O T a r g e t
104 m3/h pump
3He reserver
Pre-cooling from 300K to 30K
Heating 3He of 0.16 mol/s at Ep×Ip = 20 kW is returned to cryostat
φ12→φ25 φ12
γ heating are conducted through He-II Cooling power
3He evaporation rate
3He
filling
0.16 mol/s
0.24 mol/s at 0.7 K
20K D2O
1K pot
3He
pumping
4He pumping
8L pot
Liq.He
Isopure
4He 3He
Pulse Tube
UCN source
GM cryostat 10K D2O He-II UCN valve SCM polarizer UCN detector
Door valve
300K D2O
9
Steel Concrete Graphite Target Exhaust valve for bottle cleaning
3He
cryostat
3He-4He
Heat exchanger
EDM cell
Superconducting magnet
3He cryostat
UCN source
10
He-II
Heat exchanger
3He circulator
Superconducting UCN polarizer Isopure 4He circulator GM cryostats and He recovery line
3He-4He heat
exchanger
He-II
SCM for UCN extraction B0 Heat exchanger
was 1 W
40K radiation shield
Replaced Be-Cu with stainless steel for better thermal insulation
to the horizontal UCN guide and the UCN extraction part, 0.3 W 0.2 W
Added 4K radiation shield
Superconducting magnet
3He cryostat
UCN source
3He pumping of 2000 m3/h
Heat load on He-II 1 W 0.3 W 0.2 W
3He evaporation 32×10-3 mol/s 9.6×10-3 mol/s 6.4×10-3 mol/s
He-II temperature 0.7 K 0.6 K 0.58 K 10000 m3/h for 5W (10 W) Ep×Ip = 20 kW
13
20K D2O
1K pot
3He
pumping
4He pumping
8L pot
Liq.He
Isopure
4He 3He
Pulse Tube
UCN source
GM cryostat 10K D2O SCM polarizer UCN double valve UCN detector Spin analyzer Spin flipper 300K D2O
14
He-II Target Graphite Steel Concrete
3He cryostat
UCN valve
UCN guide
UCN spin flipper analyzer
UCN detector
3He cryostat
Superconducting UCN polarizer
15
Effect of holding field
Preliminary
to be published
Preliminary
VF(guide) = 210 neV
He-II Vacuum SCM B0 Al foils
UCN was counted as a function of valve opening time Including Al foils
B0 = 0 → 3.5 T τ = 20 → 40 s τ = 9 s
UCN transmission is enhanced ! μB0(3.5T) = 210 neV, VF(Al) = 54 neV. He-II UCN valve is effective !
16
Preliminary Preliminary
He-II
Wall loss
V E < V
We need material of low absorption and high Fermi potential
loss/collision:μ = 2f ∫{Ecos2θ/(V-Ecos2θ)}1/2
cosθ d(cosθ)
f = W/V
U = V - iW = 2πh2/m N (ar - iai) Im f(0) = k/4π σtot
σtot = σinela + σa
3He absorption: τ3He = 3900 s at 3He/4He = 10-11
He-II
electropolished SUS316L Ra < 2 nm electropolished aluminum
58Ni coated pipe
good heat conduction
In future, Be pipe or DLC coating?
UCN valve
We need material of lower f = W/V ! for τ > 100 s The material should sustain at the low temperature !
NiP → 58Ni → Be pipe or DLC coating?
20K D2O
1K pot
3He
pumping
4He pumping
8L pot
Liq.He
Isopure
4He 3He
Pulse Tube
10K D2O
SCM UCN detector Spin analyzer Spin flipper Rotary valve Door valve
19
He-II
Target Graphite Steel Concrete
H.V. EDM cell
3He cryostat
in spallation source
extraction of UCN from He-II
co-magnetometer
Superconducting UCN polarizer
3He cryostat
Compensation coils Spallation UCN source
Ramsey resonance apparatus
Permalloy shield
π/2 RF coil EDM cell
Spherical coil for B0 UCN valve Door valve
21
Iron magnetized foil Spin flipper Rotary valve UCN detector
(ω-ωo)tc =
2π 4π
3π5π
200 mG
measured by
22
nEDM is measured from shift upon E reversal B0 stability
23
Bo
EDM cell
129Xe
λ = 252 nm δν < 1 GHz P > 0.5 W Beam size < 50 μm
photon detector x8
IR photons
t
10-27 e cm
5 days of measurement δB0 = 0.3 fT
P129Xe = 3 mmTorr
895.5 nm 823.4 nm
2 GHz
+3/2 +1/2
+5/2 +3/2
F=3/2
F=5/2 5p5(2P3/2)6p(2[3/2]2) 5p5(2P3/2)6s(2[3/2]1) 5p5(2P3/2)6s(2[3/2]2) 5p6(1S0)6s
F=1/2 252.5 nm ×2 δMF = +2
σ+
129Xe
level scheme
B0 solenoid coil
B0 = 4.3 mT
B1 coil pickup coil
σ+
B1 (ν = 51.5 kHz)
0.3 0.2 0.1 0.0
Lock-in out (V)
5 4 3 2 1
t (s) B0
Xe 10 Torr N2 750 Torr enriched Xe (129Xe 86%) 156 °C
natural Xe (129Xe 26.4%) 141 °C
We have achieved
129Xe polarization of 70%
Happer
1K pot
PulseTube
4He pumping
8L pot
Liq.He
needle valves
3He
Isopure
4He
3He
pumping
3He-4He
heat exchanger
He-II
20K D2O
10K D2O Target
104 m3/h pump
3He reserver
Present helium venting tube complies with ASME at normal vacuum loss. He venting upon vacuum failure For sudden huge vacuum loss, we are now working on reconstructing the cryostat.
P = 4 UCN/cm3·s at Ec = 210 neV, Ep×Ip = 0.4 kW (2012) → 200 UCN/cm3·s in 12 L He-II 20 kW τs = 81 s (2012) → 100 s Statistical error: 10-27~10-28 e cm
Systematic error: 10-27 e cm
PUCN = 90% at the EDM cell visibility α = 83 %
ρpol = 800 UCN/cm3 in the EDM cell of Ec = 90 neV