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

A Room-Temperature nEDM Experiment at LANL

Steven Clayton, LANL, for the LANL nEDM Collaboration May 25, 2018

Outline:

• Experimental landscape
• Demonstration of stored

UCN density

• Demonstration of Ramsey’s

separated oscillatory fields technique

• The LANL nEDM experiment

International Workshop on Particle Physics at Neutron Sources 2018, Institut Laue-Langevin (ILL) May 24-26.

LA-UR-18-24533

LANL nEDM Collaboration

2

• 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

Worldwide nEDM efforts

3

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

Current Limit: Sussex/ILL Experiment

• Ramsey’s separated oscillatory

field magnetic resonance method on stored ultracold neutrons

• 199Hg comagnetometer
• Parameters:
• E ≈ 10 kV/cm
• T ≈ 130 s
• N ≈ 14,000 (detected)
• Result: dn < 2.9 x 10-26 e-cm

(90% CL)

• Note: final result was statistics-

limited

4

Baker et al. Phys. Rev. Lett. 97, 131801 (2006).

δdn ∝ 1 ET √ N

A LANL nEDM experiment is enabled by the recent UCN source upgrade

• T. M. Ito et al., Phys. Rev. C

97, 012501(R) – Published 29 January 2018

Be Graphite He-cooled W spallation target Cooled Poly Moderator 2L SD2 volume (5K) - 58Ni coated guide Flapper valve

Source upgrade project

5

LANL UCN Experimental Hall

6

UCNt Beta spectrometer LANL nEDM

LANL UCN Facility

7

UCNA/B experiment UCNτ experiment New nEDM experiment UCN source

Location of the polarized UCN density measurement

Polarized UCN density in a dummy nEDM cell

Polarized UCN density (E < 170 neV) at t=0

• 13.6(6) UCN/cc from the fill and dump

measurement (was 2.5 UCN/cc before the source upgrade )

• 39(7) UCN/cc from vanadium foil

activation measurement The difference can be attributed to loss in the switcher (~0.5) and the finite detection efficiency (~0.7).

Polarizing magnet (6 T) Switcher To UCN source UCN detector Cell valve Cell 
 (20 liters) Vanadium foil

8

9

Holding Timing [s] 100 200 300 400 500 600 700 800

GV

N /

Unload

N 10

2

10

Normalized Unloaded UCN dv

(v) τ

• t/

(v) e ρ

c

v

∫

N(t) = = 180.5(7.3)s 〉 τ 〈 = 13.6(0.6) UCN/cc Vol N(t=0) Holding time # of counted UCN 20 ~200,000 150 ~45,000

Storage time curve

Estimated statistical sensitivity of an nEDM experiment

Parameters Values E(kV/cm) 12.0 N(per cell) 39,100 Tfree (s) 180 Tduty (s) 300 α 0.8 σ/day/cell (10-26 e-cm) 5.7 σ/day (10-26 e-cm) (for double cell) 4.0 σ/year (10-27 e-cm) (for double cell) 2.1 90% C.L./year (10-27 e-cm) (for double cell) 3.4

This estimate is based on the following:

• 50 cm diameter cell
• The estimate for E, Tfree, Tduty,

and α is based on what has been achieved by other experiments.

• The estimate for N is based on

the actual detected number of UCN from our fill and dump measurement at a holding time

• f 180 s. Further improvements

are expected (new switcher and new detector). * “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

11

Polarizing magnet UCN switcher UCN spin analyzer and UCN detector Magnetic shield room

• 2 layer mu-metal
• 60”x52”x70”

interior Goal was to gain experience with the measurement technique:

• Spin transport and analysis
• Magnetic shielding, monitoring,

control

• Ramsey separated oscillatory

fields measurement

Ramsey demonstration apparatus

12

Ramsey Measurement Sequence

13

time RF power (arb)

π/2 π/2 RF Gated Off

Fraction of up-spins after second π/2 pulse (Tfree = 10 s).

• 0.4
• 0.2

0.0 0.2 0.4 0.0 0.2 0.4 0.6 0.8 1.0 Δf (Hz) Spin-Up Population

An EDM would shift the pattern upon application

• f an electric field

Demonstration of Ramsey Fringes with 10-second Free Precession Time

14

1/Tprecession

• Measured T1 = 120 s, T2 = 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 shield room will help.

LANL nEDM

• Main ideas: take advantage
• f existing UCN source; use

existing technology for relatively low project risk.

• Double cell
• Hg co-magnetometer
• Develop the apparatus in

2019—2021, followed by 5 years production data.

• Use of the UCN source is

compatible with other experiments (UCNtau, UCNA, SNS nEDM Storage Time)

15

5-Tesla polarizing magnet (existing) UCN switchers (1 existing, 1 to be constructed)

LANL nEDM Apparatus

16

200 kV direct feed (LANL) UCN valve (LANL) Cs/3He magnetometer (UMich, IU) B0 coils (UKy) Not shown:

• 199Hg co-

magnetometer polarization cell, readout optics, (existing) laser

• system. (Yale/IU)
• External UCN spin

analyzer (IU) 3-4 layer magnetically shielded room (IU, LANL)

R&D Platform Upgrades for 2018

• Add high voltage:
• Insulating vacuum
• Custom 200 kV feedthrough
• HV electrodes for top and

bottom cell walls

• Improve T1, T2*:
• Rebuild cell and valve box
• Improve B0
• Improve B-field monitoring:
• Add more Rb magnetometers
• This year’s goal: First UCN-based

nEDM measurement in the U.S.

17