WIR SCHAFFEN WISSEN – HEUTE FÜR MORGEN P. Schmidt-Wellenburg, Solvay workshop 29.11-01.12.12, Brussels Overview and status of neutron EDM experiments
A brief history of nEDM searches -19 Neutron EDM Upper Limit [ e cm] 10 -20 10 ORNL, Harvard MIT, BNL -21 10 LNPI “ n-EDM has killed -22 10 Sussex, RAL, ILL -23 10 more theories than -24 10 any other single -25 10 experiment ” -26 10 Supersymmetry predictions -27 10 J.M. Pendlebury -28 10 1936-2015 -31 10 Standardmodel calculations -32 10 1950 1960 1970 1980 1990 2000 2010 2020 Year of Publication Last First RAL-Sussex-ILL Smith, Purcell, Ramsey d n < 3 x 10 – 26 e cm (90% C.L.) ~ 50 years d n < 5 x 10 – 20 e cm C.Baker et al. PRL(2006) 131801 PR 108 (1957) 120 J.M. Pendlebury et al., PRD 92 (2015) 092003
Outline Ultracold neutrons and Ramsey’s technique Worldwide competition Searches for static and oscillating nEDM at PSI
Modified Larmor Frequency with: 𝜈 𝑜 = 1 𝑊mag = −𝜈 n Ԧ 𝜏. 𝐶 Δ𝐹 𝑛𝑏 = ℏ𝜕 𝑀 = 2𝜈 𝑜 𝐶 2 ℏ𝛿 𝑜 Δ𝐹 𝑓𝑒𝑛 = ℏ𝜕 𝑓𝑒𝑛 = 2𝑒 𝑜 𝐹 𝑊 edm = −𝑒 n Ԧ 𝜏. 𝐹 For parallel electric and magnetic fields the precession frequencies add up and for anti-parallel fields the frequencies have to be subtracted. The precession frequency difference of the two cases can be measured: ℏ𝜕 ⇈ = ℏ 𝜕 𝑀 + 𝜕 𝑓𝑒𝑛 = 2 𝜈 𝑜 𝐶 + 𝑒 𝑜 𝐹 ℏ𝜕 ↿⇂ = ℏ 𝜕 𝑀 − 𝜕 𝑓𝑒𝑛 = 2 𝜈 𝑜 𝐶 − 𝑒 𝑜 𝐹 ℏ 𝜕 ⇈ − 𝜕 ↿⇂ = 4 𝑒 𝑜 𝐹 HOW ???
The Ramsey technique ℏ Sensitivity: 𝜏 𝑒 n = 2𝛽𝑈𝐹 𝑂 Visibility of resonance T Time of free precession N Number of neutrons E Electric field strength
ሶ ሶ The beam searches ℏ 1 𝑈 = 𝑚 𝑤 ≈ 0.015s; 𝛽 > 0.9; 𝐹 = 100kV 𝜀 𝑒 n = 𝑂 = 1 × 10 6 s −1 ; cm 𝑢 2𝛽𝑈𝐹 𝑂 = 8.7 × 10 −22 𝑓cm 1 𝜏 = 1×10 −24 𝑓cm 1 day 𝑢 Hz l = 2m 𝜌/2 𝜌/2 + + + + + + + + + + + + + + E n - - - - - - - - - - - - - B Dominant systematic effect: 𝐶 𝑤 = − 𝒘 × 𝑭 𝑑 2 final result: 𝜏 𝑒 𝐨 = 1.5 × 10 −24 𝑓cm Dres et al., PRD 15(1977 77) 9 due to misalignment of 0.1 mrad
ℏ Ultracold neutrons (UCN) 𝜏 𝑒 n = 2𝛽𝐹 𝑂𝑈 3/2 1 Storable neutrons σ d n 3/ 2 NT (UCN) Gravity V 102 neV/m Nb neV V F 350 Strong V F Storage properties are material dependent Magnetic 350 neV ↔ 8 m/s ↔ 500 Å ↔ 3 mK ∼ 60 neV/T E. Fermi & W.H. Zinn (1946) unpublished, Y. B. Zeldovich, Sov. Phys. JETP (1959) 389
ℏ Superthermal UCN production 𝜏 𝑒 n = 2𝛽𝐹 𝑂𝑈 3/2 macro cross section 𝜍 = 𝜐 න dΦ d𝜇 Σ 𝜇 d𝜇 𝜐 4 He ≈ 200s 4 He differential flux UCN lifetime in medium 𝜐 D 2 ≈ 25ms D 2 R. Golub & J.M. Pendlebury, PLA62(1977)338 C.A. Baker et al., PLA308(2003)67 PSW, J. Bossy et al., PRC92(2015)024002 8 F. Atchison et al., PRL99(2007)262502
ℏ Depolarization 𝜏 𝑒 n = 2𝛽𝐹 𝑂𝑈 3/2 2 𝑨 2 𝑈 2 𝛽 𝑈 = e −Γ 2 𝑈 − 𝛿 𝑜 ⋅ 𝑒ℎ 2 eff 2 Intrinsic depolarization Gravitational depolarization Afach et al., PRL115(2015)162502 Afach et al., PRD92(2015)052008
The measurement technique Measure the difference of precession frequencies in parallel/anti-parallel fields: Δ μ 2 d E E 2 B B n n Statistical accuracy of a magnetometer correcting for a change in B should be better than the neutron sensitivity per cycle: 1 B 0 1 μT δf 11 μHz δB 100fT n 2 παT N
Magnetic fields 𝜀𝐶 < 100fT optical pumped magnetometers (CsM/HgM/XeM … )
Outline Ultracold neutrons and Ramsey’s technique Worldwide competition Searches for static and oscillating nEDM at PSI
Principal approaches 𝑒n = ℏΔ𝜕 − 2𝜈n 𝐶 ↿ ↾ − 𝐶 ↿ ⇂ ≈ ℏΔ𝜕 2(𝐹 ↿ ↾ − 𝐹 ↿ ⇂ ) 4|𝐹| Measured simultaneously (n2EDM) Measured as sequence (nEDM) +++++++ +++++++ Co-magnetometer Corrections for differences of mean magnetic- Corrections for changes of the mean (mercury, xenon, 3 He) field gradient magnetic field Magnetic shield Minimal residual fields + Small residual fields + (active, passive) Stability: higher order gradients Stability paramount !! TUM TRIUMF(2) LANL Efforts PNPI PSI(2) PSI(1) finished SNS LANL(2) TRIUMF(1) Non-UCN searches Crystal EDM (ILL&PNPI), beam EDM (F. Piegsa, ESS)
nEDM Experiment at LANL UCN Source Location of the nEDM experiment SD2 UCN source UCN τ Room temperature Ramsey experiment UCNA • Initial goal is to demonstrate a stored • UCN density sufficient for a several x 10 -27 e-cm nEDM experiment UCN upgrade concluded • LANL collaboration: First measurements with Ramsey cell • LANL, Indiana Univ., Univ of Kentucky, Univ. of Michigan, Yale Univ., JINR courtesy: Ito Takeyasu
ILL / TUM effort ILL/TUM effort: Berkley, ILL, Jülich, LANL, Michigan, MSU, NCSU, PTB, RAL, TUM, UIUC, Yale courtesy: Skyler Degenkolb Page 15
ILL SuperSun “ 3 He cryostat” Converter volume: 12 litres UCN production rate: 10 5 s -1 ( E < 230 neV) delivered and tested Saturated UCN number: 4 × 10 6 (stage I, Fomblin spectrum) 2 × 10 7 (stage II, polarized, E < 230 neV) SuperSUN stage II (with magnet) feasibility study in progress “magnetic trap cryostat” ordered (Elytt, Spain) SuperSUN stage I (without magnet) design in progress “converter cryostat” to be delivered soon courtesy: Oliver Zimmer Page 16
nEDM @ SNS Redesign to reduce costs (7/17) Smaller shield house Non-modular 3 He system & smaller building courtesy: Brad Filippone
nEDM @ SNS Critical Component Demonstration (1/14-12/17) nearing completion • > 75kV/cm achieved in mid-scale HV system • With Cu-coated composite electrodes • With closed measurement cell • 3 He transport (phonon heat-flush) demonstrated in large-scale • Non-magnetic dilution fridge nearly complete • B-field uniformity (3 ppm/cm in full-scale) achieved in 1/3-scale cryogenic prototype & dressed spin design advanced • Noise levels sufficient in SQUID system prototype • 1800s UCN storage time measured in cryogenic cell • > 18 photo-electrons equivalent observed in cryogenic light collection Full-scale operation in 2022 system with LHe & TBP (need 6 PE at least) courtesy: Brad Filippone
nEDM @ PNPI (&ILL) : 𝒆 𝐨 < 𝟔. 𝟔 × 𝟐𝟏 −𝟑𝟕 𝒇𝐝𝐧 Curr rren ent: Impro rove veme ment nt by fact ctor or 3 at new w posit ition ion and d with new w prec ecession sion cell ll 20 : 𝒆 𝐨 < 𝟑 × 𝟐𝟏 −𝟑𝟕 𝒇𝐝𝐧 ILL 2020 new scheme courtesy: Anatolii Serebrov
PNPI UCN source at WWR-M reactor • UCN density > 1 × 10 5 cm −3 • All hardware exists WWR-M reactor • Necessary cooling power test succesful • Unclear whether and when WWR-M will get permission to operate Page 20
ESS pulsed beam experiment Use neutron source ’ s intrinsic pulses Fixed installation Lenght: 50m d𝑂 d𝑢 > 100 MHz Τ courtesy: F. Piegsa
UCN EDM at TRIUMF • Overview: • Features: Japan-Canada collaboration Unique UCN source technology with world- Spallation-driven He-II leading potential. UCN source connected to 129 Xe/ 199 Hg dual-species comagnetometer to RT nEDM experiment. cancel false EDM’s. First UCN Nov 2017! Congratulations Goal sensitivity (statistics): δ d n ~ 10 -27 e-cm (2019-2022) UCN source courtesy: Rüdiger Picker
Status & Schedules Sensitivity goal Schedule Project Status (E-27 e cm) (start data-taking) UCN density sufficient for LANL 2017:UCN source upgrade finished 2019 O(1) TUM-ILL TUM apparatus moves to ILL O(0.1) 2019 PNPI At PNPI 2020 PNPI: 0.5 PNPI later SNS Critical component demonstration concluded 0.2 2022 TRIUMF 2017: first UCN 2-3 years for experiment 2019 O(1) Phase(1) data-taking concluded Phase 1: O(10) PSI Phase(2): 2020 Phase(2) construction Phase 2: O(1) ESS Demonstration phase at ILL O(0.1) ? 2025
Worldwide comparison of UCN sources Bison et al ., PR C 95(2017)045503 ?
Outline P. Schmidt-Wellenburg Ultracold neutrons and Ramsey’s technique TRIUMF Colloquium 2017-10-12 Worldwide competition Searches for static and oscillating nEDM at PSI 25 50
The collaboration P. Schmidt-Wellenburg • 15 Institutions • 7 Countries • 48 Members • 14 PhD students TRIUMF Colloquium 2017-10-12 26 50
PSI UCN source P. Schmidt-Wellenburg UCN storage volume Main shutter Neutron guide to experiments TRIUMF Colloquium 2017-10-12 1m UCN convertor (solid D 2 @ 5K) Protons Spallation target E n ~ MeV 590 MeV D 2 O moderator 2.2 mA Neutrons thermalized to 25 meV Golub, R. & Pendlebury, J. M PLA (1975 75)133 Anghel, et. al 27 50 NIMA (2009) 09) 272
The nEDM spectrometer 28 50 P. Schmidt-Wellenburg TRIUMF Colloquium 2017-10-12
Simultaneous spin detection P. Schmidt-Wellenburg o Spin dependent detection Adiabatic spinflipper • Iron coated foil • o 6 Li-doped scintillator GS20 TRIUMF Colloquium 2017-10-12 B 29 S. Afach et al., EPJA (2015)51: 143 50
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