NEUTRON EDM Philip Harris, on behalf of the CryoEDM collaboration: Rutherford Appleton Laboratory University of Oxford University of Sussex ILL University of Kure

Technology Neutrons in HV in

Sensitivity (NB sensitivity/day is actually closer to ) Successfully produced, transported, stored UCN, but need to reduce losses Successfully applied 10 kV/cm (same as previous expt); aiming for kV/cm Achieved 60% polarisation in source, but must improve RT-edm: 130 s. So far we have 62 s cell storage time.

Sensitivity in 2012 Room-temperature expt final sensitivity ~2E-25 ecm/day Took 12 years of incremental developments from known technology Systematics limited (geometric phase effect) We can come within factor 4-5 of this in 2012 by increasing detector area x10: technology now proved refurbishing damaged detector-valve: in hand applying ~70 kV (previously ~40 kV): should be straightforward opening beam aperture from 43 to 50 mm: depends on radiation levels retaining polarisation: superconducting material has been removed There may be additional improvements beyond this  peak above background (detector improvement) Polarisation to 60% (improved guide field) Increasing cell storage lifetime (insulator bakeout) (we will achieve these by 2014)

Shutdown and move to new beamline Mid-2013: Have to vacate current location. ILL will shut down for a year; we will move to new dedicated beamline. New beam 4x more intense; and dedicated Due to become operational mid-2014 Beam must then be characterised (9A flux, divergence, stability, polarisation) We will then have access to the area (late 2014) to move our apparatus into it. M&O uplift requested to fund move and infrastructure in new location.

Upgrade : Upcoming PPRP request Not yet fully costed Major upgrade to experiment: Cryogenics design changes: Pressurise the liquid helium: increase E field x 2-3 Upgrade from two-cell to four-cell system 2 x neutrons Cancellation of some systematic effects Installation of inner superconducting magnetic shield B-field stability improves x1000, for systematics Construction of non-magnetic SCV Improves depolarisation: better T 2 Overcome geometric-phase systematic error Net result: Order of magnitude improvement in sensitivity Commensurate improvement in systematics

Sensitivity timeline DateItem factorecm/year Comment 2002RT-edm 1.7E-26 Baseline 2010CryoEDM commission 1.7E Large-area detector E-25 Proven 2012HV to 70 kV E-25 OK to 50 kV, lab tests suggest should work at 70 kV 2012Repair detector valve E-25 Repair – should be fine 2012Polarisation 60% E-25 Seen in source. Should transfer ok to cells. 2012Aperture to 50 mm E-25 Will increase radiation levels slightly, but should be ok 2012Ramsey time to 60 s E-26 Almost certain – undergoing mag. scan now to confirm 2013See alpha peak E-26 Quite likely by 2012, but we do not count on it by then 2014New beam E-26 ILL produced this estimate 2014Recover missing input flux? E-26 Depends on geometry match to new beam. 2014Improve cell storage lifetime to 100 s E-27 Not guaranteed, but haven't yet tried most obvious solutions (e.g. bakeout), so improvement likely 2014Match aperture to beam E-27 Likely 2015HV to 135 kV E-27 Requires pressurisation. Lab tests show this is realistic. 2015Four-cell system E-27 Guaranteed part of upgrade 2015Polarisation to 90% E-27 No known reason why not Inner supercond. shield Lab tests on scale model shows factor Cryogenics Included in upgrade Non-magnetic SCV Included in upgrade

Sensitivity and systematics Without upgrade, we may reach factor ~3 better stats than RT- edm (possibly better if storage lifetime improves significantly). Systematics is a different matter. Back-to-back cells (4-cell system) provide important cancellations Completely non-mag SCV would eliminate most of geometric-phase systematic (which limited RT-edm). 1 nT/m very difficult otherwise. Magnetic shielding controls fluctuations, reduces broadening of Ramsey fringes Changes to cryogenics would increase reliability (reduce down-time), reduce manpower burden, reduce He consumption... With upgrade, should reach factor ~10 improvement in stat sensitivity, with commensurate improvement in systematics.