A new UCN source at TRIUMF for EDM, β decay, gravity etc.

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Myra Booth
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1 A new UCN source at TRIUMF for EDM, β decay, gravity etc. UCN For these experiments, Phase space density is crucial. Momentum space is limited by Fermi potential (E c = 100~200 nev) and magnetic potential (60 nev/t), real space by bottle size!"#$#%&!' & ()*a#+

2 Present UCN source at ILL 50 UCN/cm 3 in source E c = 335 nev Turbine Vertical guide Cold source 60 MW Reactor 2 to 3 UCN/cm 3 in an experimental bottle of E c = 100 nev 0.7 UCN/cm 3 in EDM cell UCN density is limited by Liouville s theorem for the deceleration by gravity and Doppler effect

3 New UCN sources LANL, PSI, NCSU, Munich, ILL, SNS and Ours use neutron cooling by phonon no limitation of Liouville s theorem, we can use phonon phase space phonon cold neutron He-II or SD2 UCN E in E UCN form factor S(Q,ω) Production rate, P UCN P UCN = σ coh (E in E UCN ) Φ n (E in ) N de in de UCN d 2 σ/dqdω= k f /k i σ coh /4π S(Q,ω) ρ UCN = P UCN τ s (storage lifetime)

4 A new UCN production

5 Cold neutron flux Φ n SNS 1.5MW: Φ n ~10 8 n/cm 2 /s ILL 60MW: Φ n = n/cm 2 /s UCN source in cold neutron guide capture flux: 10-3 in cold neutron moderator Ours 20kW: Φ n = n/cm 2 /s PSI 1.2MW: Φ n = n/cm 2 /s NCSU 1MW: Φ n = n/cm 2 /s n

6 UCN production rate P UCN M.R. Gibbs et al. (1999) S(Q,ω) in He-II multi phonon single phonon In our He-II P UCN = (2 ~ 4) 10-9 Φ n /cm 3 /s, Phys.Lett A301(2002)462 = 0.37 ~ UCN/cm 3 /s 20 kw In Los Alamos SD2 P UCN = UCN/cm 3 /s, Phys.Lett B593(2004)55 76 kw In PSI SD2 P UCN = UCN/cm 3 /s, Phys.Rev C71(2005) MW

7 250 s 611 s 123 s 0.8 K 0.9 K 36 s 64 s 1 K 1.1 K 1.2 K Storage time τ s He-II [Golub et al. (1983)] phonon up-scattering, 1/τ ph T 7 τ ph = 600 s at T He-II = 0.8 K β decay lifetime, τ β = 886 s wall loss, τ wall = 300 s τ s = 150 s SD2 [Phys.Rev.C71(2005)054601] τ ph = 40 ms at T SD2 = 8 K τ ortho-para = 100 ms τ a = 150 ms τ s = 24 ms diluted in vacuum τ s = 1.6 s, L Los Alamos τ s = 6 s, 27L 2 m 3 PSI

8 Extraction from source Vacuum diffuse to UCN guide / storage volume acceleration shutter Superfluid He, ε 100% SD2, ε 10% [Phys.Rev.C71(2005)054601] 4 He d scattering UCN production phonon cold neutron UCN average velocity 5m/s (v av /4) 24ms = 3 cm absorption γ heating quickly remains removed neutron capture γ

9 Shuttered UCN source

10 World s UCN projects, ρ UCN = P UCN τ s ε ext (dilution factor) source type TRIUMF spallation He-II ILL SNS LANL PSI NCSU Munich n beam He-II n beam He-II spallation SD2 spallation SD2 reactor SD2 reactor SD2 E c nev 210 P UCN /cm 3 /s (10L) τ s s ε ext ρ UCN /cm 3 source/exp (20L) / **/ (7L) (240cm 3 ) (27L*) (1L) **/ / * (3.6L) / (2m 3 ) /1000 ** ** 1300/** 250 ** ** ** /**

11 Present status Los Alamos 76 kw: ρ UCN = 145 UCN/cm 3 in a 3.6 liter bottle at E c = 200 nev 0.8 UCN/cm 3 at experiment PSI 1.2 MW : will start in 2009 Munich 100 kw Trigger reactor at Mainz: 8 UCN/cm 3 in a 10 liter bottle at E c = 250 nev Sussex-RAL 60MW: P UCN = 1 UCN/cm 3 /s at E c = 250 nev Ours 390 W: P UCN = 4 UCN/cm 3 /s in a 10-liter He-II at E c = 210 nev (ρ UCN = 160 UCN/cm 3 at τ s = 40 s) ρ UCN = 10 UCN/cm 3 at experimental port of E c = 90 nev

12 open To 4 He pump To 3 He pump UCN valve UCN guide 3 m UCN production in our prototype source SRD220 4He cryostat 1.25 m 3He cryostat 35 K Liq. He UCN detector SUS disk with a 1-cm diam hole UCN phonon He-II 19 K D 2 O 300 K D2O Graphite Spallation target p n

13 Result of Nov UCN production with a proton-pulse of 1 μa Counts / Time bin / Cycle proton τ = 30 s at T He-II = 0.9K 0.9K 1.0K 1.1K 1.2K 1.4K Proton Time (0.5s/ch)

14 Counts / Time bin / Cycle With/without the annular SUS disk, with a p-pulse of 1μA UCN valve closed proton opened With Al foil one shot counting With Al foil UCN go back and forth Remove Al and the disk Time (0.5s/ch)

15 UCN density by 390W p beam UCN valve v av = 3.1 m/s at E c = 90 nev S = π cm 2 UCN flow rate = 1/4 ρv av S count rate = 1/4 ρv av S d ε = 409 counts/s S d = π cm 2 UCN detector ε = 0.68 ρ = 10 UCN/cm 3 assuming statistical distribution UCN / 36 liter 1.2x10 6 UCN/30 s for 10 liter He-II production rate = 4 UCN/cm 3 /s

16 Comparison with the theoretical prediction Present exp. : production rate = 4 UCN/cm 3 /s 5.2 UCN/cm 3 /s (E c : nev) 0.9 UCN/cm 3 /s at ILL 250neV [Phys.Lett. A308(2003)67] 4 ~ 8 UCN/cm 3 /s at 400W, 250neV Predicted production rate (1/8) (2 ~ 4) 10-9 Φ n /cm 3 /s, Φ n (T n = 80 K) Φ n = (n/cm 2 /s) by Monte Carlo [ (2 ~ 4) 10-9 Φ n /cm 3 /s, Φ n (T n = 20 K) ]

17 UCN double valve 273 K Heater 3 m 3 He circulator γ heating 1.2 m 86 K is transformed Shield to 3 He of gas kinetic energy 1 m iron latent heat (potential energy) UCN 0.5 m concrete = 34.5 J/mol at 0.8 K detector 3 He gas flow γ heating Liq. He SRD220 To 4 He pump 4He cryostat 3He condenser Spallation target UCN guide γ heating He-II 0.5 K To 3 He pump 3He cryostat 3He pot 10 K D 2 O 35 K Liq. He 300 K D2O Graphite

18 γ heating in He-II at a 390W of proton beam 3 He gas flow increased by 0.8 slm γ heating = 20 mw He-temperature increased by 0.01 K 75 mw by Monte Carlo assuming D 2 O is an ideal gas Neutron temperature expected to be higher, 20 K 80 K neutron capture rate may be smaller at higher temperature or Bragg cut off?

19 Cooling power for He-II latent heat of vaporization (34.5 J/mol) P He (vapor pressure 3 Torr at 0.8 K) dv/dt (pumping power m 3 /h) / R (gas constant) 17 W γ heating is 8 W at 20 kw of p beam by Monte Carlo ( 3 He flow rate showed much smaller heating)

20 Preparation for Ramsey resonance with the present source radiation shield 3 He pump UCN guide 4 He pump He-II cryostat p beam UCN storage bottle in 2007

detector After t s Ho, E (in preparation) Filling valve H1

21 Study of EDM cell Fomblin coated Teflon bottle UCN spin analyzer (in preparation) UCN count Emptying valve UCN detector After t s Ho, E (in preparation) Filling valve H1 (in preparation) from UCN source UCN spin polarizer (in preparation)

22 Results of Nov storage time in the Teflon bottle: τ s = 210 s A proton pulse of 0.2 μa Filling valve closed Leak from emptying valve Emptying valve opened Opening time Here delayed EDM can be measured More delay

23 UCN counts Storage Height Dependence time of UCN Counts measurement / SUS disk / I p =1µA 10 5 Fitting function: as a function of h h = 30 ~ 90 cm y = A exp ( - t /! ) τ 1 = 23 s τ 2 = 39 s h = 10 cm h = 10 ~ 20 cm y = A 1 exp ( - t /! 1 ) + A 2 exp ( - t /! 2 ) After t s emptying valve open 21 cm Piston filling valve close h h = 90cm h = 85cm h = 80cm h = 70cm h = 60cm h = 50cm h = 40cm h = 30cm h = 20cm h = 10cm h = 5cm UCN valve UCN detector Time [s]

24 3 He x z Ramsey resonance Y. Mauda et al.,phys. Lett. A364 (2007)87_92 Appl. Phys. Lett. 87, (2005) H 1 γh 1 t r = π/2 H 1 rotations π/2 and Larmor precession are coherent π/2 y n spin Rotating field H 0 (ω 0 = γh 0 ) H 1 x cosωt r + H 1 y sinωt r ω = ω 0 n spin H 1 Rotating frame of ω 0 + ΔH 0 γδh 0 t φ = π + γδh 0 t cosφ

25 φ = π + ϒΔH 0 t T on /T off H s = ± 0.05 G x = ± m (!"# = 20.7 Gauss) arises from additional field Neutron Energy (ev)

26 Experiment with prototype source 1. UCN density is consistent with the prediction. 2. We can remove the γ heating, which is not so serious. 3. Storage time τ s = 30 s (improved to 40 s in Nov. 2007) is limited by the wall loss, but much longer in He-II bottle. 4. We are preparing Ramsey resonance with the present source

At TRIUMF Φ n = 1.8x10 12 /cm 2 /s in 10L He-II P UCN = 0.

27 At TRIUMF Φ n = 1.8x10 12 /cm 2 /s in 10L He-II P UCN = UCN/cm 3 /s E c = 210 nev τ s = 150 s E p xi p = 20kW UCN phonon T=0.8K cryogenic window

28 ρ UCN = P UCN τ s ε ext (dilution factor) source type TRIUMF spallation He-II ILL SNS LANL PSI NCSU Munich n beam He-II n beam He-II spallation SD2 spallation SD2 reactor SD2 reactor SD2 E c nev 210 P UCN /cm 3 /s (10L) τ s s ε ext ρ UCN /cm 3 source/exp (20L) / **/ (7L) (240cm 3 ) (27L*) (1L) **/ / * (3.6L) / (2m 3 ) /1000 ** ** 1300/** 250 ** ** ** /**

The New Search for a Neutron EDM at the SNS

The New Search for a Neutron EDM at the SNS Jen-Chieh Peng University of Illinois at Urbana-Champaign The Third International Symposium on LEPTON MOMENTS, Cape Cod, June 19-22, 2006 Physics of neutron