NEUTRON EDM Philip Harris on behalf of the
NEUTRON EDM Philip Harris, on behalf of the Cryo. EDM collaboration: Rutherford Appleton Laboratory University of Oxford University of Sussex ILL University of Kure
Technology HV in Neutrons in
Sensitivity Achieved 60% polarisation in source, but must improve Successfully applied 10 k. V/cm (same as previous expt); aiming for 20 -30 k. V/cm (NB sensitivity/day is actually closer to Successfully produced, transported, stored UCN, but need to reduce losses RT-edm: 130 s. So far we have 62 s cell storage time. )
Sensitivity in 2012 • Room-temperature expt final sensitivity ~2 E-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 x 10: technology now proved • refurbishing damaged detector-valve: in hand • applying ~70 k. V (previously ~40 k. V): 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 • a 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 4 x more intense; and dedicated • Due to become operational mid-2014 • Beam must then be characterised (9 A 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 2013 -15: 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 x 1000, 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 Date Item factor ecm/year Comment 2002 RT-edm 1. 7 E-26 Baseline 2010 Cryo. EDM commission 1. 7 E-24 2012 Large-area detector 3. 5 2012 HV to 70 k. V 1. 6 2012 Repair detector valve 1. 3 2012 Polarisation 60% 1. 5 2012 Aperture to 50 mm 1. 2 2012 Ramsey time to 60 s 1. 8 2013 See alpha peak 1. 4 2014 New beam 2. 0 5. 5 E-26 Quite likely by 2012, but we do not count on it by then 2. 7 E-26 ILL produced this estimate 2. 2 1. 2 E-26 1. 5 8. 3 E-27 1. 3 6. 4 E-27 1. 9 3. 3 E-27 Requires pressurisation. Lab tests show this is realistic. 2. 3 E-27 Guaranteed part of upgrade 2014 Recover missing input flux? 2014 Improve cell storage lifetime to 100 s 2014 Match aperture to beam 2015 HV to 135 k. V 2015 Four-cell system 1. 4 2015 Polarisation to 90% 1. 5 2013 -15 Inner supercond. shield 4. 9 E-25 Proven 3. 1 E-25 OK to 50 k. V, lab tests suggest should work at 70 k. V 2. 5 E-25 Repair – should be fine 1. 7 E-25 Seen in source. Should transfer ok to cells. 1. 4 E-25 Will increase radiation levels slightly, but should be ok 7. 7 E-26 Almost certain – undergoing mag. scan now to confirm Depends on geometry match to new beam. Not guaranteed, but haven't yet tried most obvious solutions (e. g. bakeout), so improvement likely Likely 1. 6 E-27 No known reason why not Lab tests on scale model shows factor 500 2013 -15 Cryogenics Included in upgrade 2013 -15 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 n. T/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.
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