The neutron electric dipole moment experiment at PSI

The neutron electric dipole moment experiment at PSI Bri. X meeting, Mol, May 10 th, 2016 Nathal Severijns

PSI in Switzerland

Pendlebury et al. , Phys. Rev. D 92 (2015) 092003 (RAL/Sussex/ILL) dn < 3. 0 x 10 -26 e. cm

UCN Source UCN convertor 30 l solid D 2 @ 5 K 590 Me. V 2. 2 m. A D 2 O moderator Neutrons thermalized to 25 me. V Spallation target En~ Me. V R. Golub & J. M. Pendlebury, Phys. Lett. (1975)133 Anghel et. al. , NIM A (2009) 272

n. EDM Spectrometer

PSI in Switzerland Statistical accuracy of a magnetometer correcting for a change in B should be better than the neutron sensitivity per cycle:

Motivation

Magnetic Field Mappings

n. EDM Spectrometer

Cesium Gradiometer Monitoring of vertical magnetic gradients • 6 HV Cs. M • 10 ground Cs. M • stabilized laser ± 132 k. V 1 2 … 6 7 … 15 16

UCN Operation Statistics In 2015: full proton beam operation period (May - Dec. ) ~ 200 days 58'000 pulses total of ~140 days with UCN available in 2015 124 n. EDM data taking days used ~65% of proton beam operating time in 2015

Measured UCN counts Measurement of the total UCN counts (spin-up and down) after 180 s of storage in the n. EDM precession chamber Main features: - operation / failsafe - fast UCN output decrease - regain of UCN output after conditioning - continuous output increase after every conditioning July 26 th Dec. 13 th

Magnetic field stability 40 p. T 400 p. T

Neutron frequency as measured corrected for variations in B 0 using Hg co-magnetometer

Leuven: - homogenization of magnetic field with the Cs magnetometers - development of a K-based magnetometer for stabilizing B 0 current source - data analysis - study uncompensated field drift (most important systematic effect)

New magnetometry lab in Leuven - Laser systems for Cs and K magnetometers

Cs cell Magnetometer cell housing

New magnetometry lab in Leuven - Magnetic shields for magnetometers

R versus Gradient B 0 up B 0 down Field maps

2015 campaign RAL/Sus sex/ILL PSI 8. 3 11 Neutrons 14300 10350 Tmeaa (s) 130 180 alpha 0. 45 0. 75 E-field (k. V/cm)

Coarse Strategy • We are taking data with the highest sensitivity ever σ(dn) < 1. 7 x 10 -26 e. cm • 2016, (2017): continued data taking with n. EDM - expect with 200 data-days in 2016 : statistical sensitivity of σ ≲ 10 -26 e⋅cm - 2017: focus mainly on limiting systematic errors o continue UCN source improvement and upgrade scenarios o (2017), 2018 or 2019 start installation of n 2 EDM in area South n 2 EDM TDR in 2017 n 2 EDM data taking to start 2020

Pendlebury et al. , Phys. Rev. D 92 (2015) 092003 (RAL/Sussex/ILL) dn < 3. 0 x 10 -26 e. cm x n. EDM n 2 EDM