A Room-Temperature nEDM Experiment at LANL Steven Clayton, LANL, - PowerPoint PPT Presentation

LA-UR-18-24533 A Room-Temperature nEDM Experiment at LANL Steven Clayton, LANL, for the LANL nEDM Collaboration May 25, 2018 Outline: • Experimental landscape • Demonstration of Ramsey’s separated oscillatory fields • Demonstration of stored technique UCN density • The LANL nEDM experiment International Workshop on Particle Physics at Neutron Sources 2018, Institut Laue-Langevin (ILL) May 24-26.

LANL nEDM Collaboration S. Clayton, S. Currie, T. Ito, S. MacDonald, M. Makela, C. Morris, C. O’Shaughnessy, R. Pattie Jr., A. Saunders, A. Urbaitis Los Alamos National Laboratory F. Gonzalez, C.-Y. Liu, J. Long, W. Snow, D. Wong Indiana University A. Alexandrova, R. Dadisman, B. Plaster University of Kentucky N. Sachdeva, T. Chupp University of Michigan S. K. Lamoreaux Yale University E. Sharapov Joint Institute of Nuclear Research � 2

Worldwide nEDM efforts PNPI TRIUMF PSI PNPI nEDM TUCAN nEDM n2EDM LANL LANL nEDM ORNL ILL SNS nEDM Sussex-RAL-ILL (current limit) CryoEDM PanEDM PNPI-ILL (2nd-best limit) � 3

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A LANL nEDM experiment is enabled by the recent UCN source upgrade Flapper valve 2L SD2 volume (5K) - 58Ni coated guide Source upgrade project Cooled Poly Moderator T. M. Ito et al., Phys. Rev. C He-cooled W 97 , 012501(R) – Published spallation target 29 January 2018 Graphite Be � 5

LANL UCN Experimental Hall LANL nEDM UCNt Beta spectrometer � 6

LANL UCN Facility UCN source Location of the polarized UCN density measurement New nEDM experiment UCN τ experiment UCNA/B experiment � 7

Polarized UCN density in a dummy nEDM cell Vanadium foil Cell 
 Polarizing (20 liters) Polarized UCN density (E < 170 neV) at t=0 magnet (6 T) • 13.6(6) UCN/cc from the fill and dump Switcher measurement (was 2.5 UCN/cc before To UCN source the source upgrade ) Cell valve • 39(7) UCN/cc from vanadium foil activation measurement UCN detector The difference can be attributed to loss in the switcher (~0.5) and the finite detection � 8 efficiency (~0.7).

Storage time curve GV N Normalized Unloaded UCN / v c Unload 2 10 ∫ -t/ (v) τ N(t) = (v) e dv ρ # of counted Holding time N 0 UCN = 180.5(7.3)s 〈 τ 〉 N(t=0) = 13.6(0.6) UCN/cc Vol 20 ~200,000 10 150 ~45,000 0 100 200 300 400 500 600 700 800 Holding Timing [s] � 9

Estimated statistical sensitivity of an nEDM experiment This estimate is based on the following: Parameters Values 50 cm diameter cell • E(kV/cm) 12.0 The estimate for E, T free , T duty , • N(per cell) 39,100 and α is based on what has T free (s) 180 been achieved by other T duty (s) 300 experiments. α 0.8 The estimate for N is based on • σ /day/cell (10 -26 e-cm) 5.7 the actual detected number of σ /day (10 -26 e-cm) 4.0 UCN from our fill and dump (for double cell) measurement at a holding time σ /year (10 -27 e-cm) 2.1 of 180 s. Further improvements (for double cell) are expected (new switcher and 90% C.L./year (10 -27 e-cm) 3.4 new detector). (for double cell) * “year” = 365 live days. In practice, it will take 5 calendar years to achieve this with 50% data taking efficiency and nominal LANSCE accelerator operation schedule � 10

Ramsey demonstration apparatus Polarizing magnet UCN switcher Goal was to gain experience with Magnetic shield room • 2 layer mu-metal the measurement technique: • 60”x52”x70” • Spin transport and analysis UCN spin • Magnetic shielding, monitoring, interior analyzer and control UCN detector • Ramsey separated oscillatory fields measurement � 11

Ramsey demonstration apparatus � 12

Ramsey Measurement Sequence π /2 π /2 RF power ( arb ) RF Gated Off time Fraction of up-spins after second π /2 pulse (T free = 10 s). Spin - Up Population 1.0 An EDM would 0.8 shift the pattern 0.6 upon application of an electric field 0.4 0.2 0.0 - 0.4 - 0.2 0.0 0.2 0.4 Δ f ( Hz ) � 13

Demonstration of Ramsey Fringes with 10-second Free Precession Time • Measured T 1 = 120 s, T 2 = 20 s ➡ Residual magnetism in parts of the retrofit storage cell + valve box • Polarization transport was a challenge ➡ Not much distance to go from 1 G to 20 µG; a larger 1/ T precession shield room will help. � 14

LANL nEDM • Main ideas: take advantage of existing UCN source; use existing technology for UCN switchers (1 existing, relatively low project risk. 1 to be constructed) • Double cell • Hg co-magnetometer • Develop the apparatus in 5-Tesla polarizing 2019—2021, followed by 5 magnet years production data. (existing) • Use of the UCN source is compatible with other experiments (UCNtau, UCNA, SNS nEDM Storage Time) � 15

LANL nEDM Apparatus B 0 coils (UKy) Cs/ 3 He magnetometer (UMich, IU) 200 kV direct feed (LANL) 3-4 layer magnetically shielded room (IU, LANL) Not shown: • 199 Hg co- magnetometer polarization cell, UCN readout optics, valve (existing) laser (LANL) system. (Yale/IU) • External UCN spin analyzer (IU) � 16

R&D Platform Upgrades for 2018 • Add high voltage: • Insulating vacuum • Custom 200 kV feedthrough • HV electrodes for top and bottom cell walls • Improve T 1 , T 2 *: • Rebuild cell and valve box • Improve B 0 • Improve B-field monitoring: • Add more Rb magnetometers • This year’s goal: First UCN-based nEDM measurement in the U.S. � 17