PoS(EPS-HEP 2009)376 , 1 http://pos.sissa.it/ cm as measured with e 26 − 10 × 9 . 2 < | n d | 5 , M A H Tucker and D L Wark 3 , A Khazov 2 , S Henry, H Kraus and M McCann 4 ∗ [email protected] a room temperature experiment. Byhigh densities operating of in ultra superfluid cold helium ,or the below measure cryoEDM 0.9 an experiment K will EDM. improve and High on precision collecting thethe magnetometry existing cryoEDM is limit experiment essential originating to from reduce changes thecryoEDM in systematic apparatus the errors and magnetic in technologies. environment. We present the Speaker. The cryoEDM experiment at thedipole moment Institut (EDM) Laue-Langevin of in the Grenoble neutronCP with will violation. unparalleled measure precision. The the cryoEDM A experiment electric is“beyond EDM sensitive arises the to due levels standard to of model” CPtheories. violation theories predicted The and current by limit the many to the result neutron EDM will stands at therefore constrain or support these ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c

European Physical Society Europhysics Conference onJuly High 16-22, Energy 2009 Physics Krakow, Poland joint with Rutherford Appleton Laboratory, Chilton, Didcot, OXON OX11 0QX, UK University of Oxford, Keble Road, Oxford OX1 3RH, UK. P Geltenbort Institut Laue-Langevin, BP156, F-38042 Grenoble, France. H Yoshiki University of Kure, Japan. on leave of absence from INRNE,on Sofia, leave Bulgaria of absence from PNPI,joint St with Petersburg, Russia the University of Sussex,E-mail: Falmer, Brighton BN1 9QH, UK C A Baker, S N Balashov, V Francis, K Green, MScience and G Technology D Facilities Council, van Rutherford der AppletonOX11 Grinten, Laboratory, 0QX, Chilton, UK. P Didcot S Iaydjiev A Davidson, J R Grozier, MPendlebury, S Hardiman, J P M G Peeters, Harris, DUniversity J B of R Sussex, Shiers, Karamath, Falmer, Brighton P K BN1 N Katsika, 9QH, Smith, J UK. C M MC Townsley Clarke and I Wardell Measuring the ofneutron: the The cryoEDM experiment S N Ivanov 5 1 2 3 4 PoS(EPS-HEP 2009)376 C Clarke ). n d cm to the neutron He. The apparatus e 4 33 − ]. The current upper limit of to 10 3 ]. Two short RF pulses are ap- 31 5 − cm [ 10 e ∼ 28 − to 10 25 cm which allows for a nEDM discovery or a new 2 − e 28 − He expansion system cools the UCN production volume 3 ) is based at the Institut Laue-Langevin (ILL), Grenoble. 1 ]. This already constrains some supersymmetric models and CP 4 ]. A particle electric dipole moment (EDM) breaks parity and time 1 300 s) precession period. If the applied frequency matches the preces- cm [ ∼ e 26 − 10 ]. If this is the only contribution, measuring the nEDM is beyond the reach of any × , we need sensitivity within a small fraction of the Larmor frequency. This is n 2 9 . µ ). With an electric field present, in addition to the magnetic field, the precession fre-  n µ n d The cryoEDM experiment (Fig. The entire measurement in the cryoEDM experiment takes place below 0.9 K. The nEDM is Measurements of particle electric dipole moments have been the subject of increasingly sensi- The weak sector CP violation of the SM contributes As A neutron precesses in a magnetic field at the Larmor frequency due to its magnetic dipole 0.7 K. The electric field is generated by a Spellman HV supply and applied to the resonance ∼ It produces, stores and detects ultra-cold neutrons (UCN) within superfluid to the nEDM is 2 plied separated by a long ( sion frequency, the resonance case is metthe and magnetic the field. neutron A is difference completelythe in flipped RF the anti-parallel and to precession neutrons’ frequency precession anding the to in applied get a frequency increasingly final will out spin cause the state of direction dependant step on of during the the the phase electric freefrequency difference. field precession where Looking the is result- final for reversed number a requires of shift operating spin in at up frequency neutrons a when is frequency most near sensitive the to3. the resonance phase The difference. experimental set-up includes two cooling towers: towercools I the supplies magnetic the shields. helium A for circulating the production of UCN and tower II current experiment. Extensions tomodels) the predict SM a (for larger example nEDM in and the left-right range symmetric 10 measured through an NMR process thatsubjected looks to for external a electric shift and in the magneticenvironment neutron fields. is precession Tight frequency essential. control when andsensitivity Due measurement is of to predicted the to advantages magnetic be gained of from the order working 10 in cryogenic conditions, the violation in the strong sector of the SM. tive experiments since 1951 [ achieved using Ramsey’s method of separated oscillating fields [ The cryoEDM experiment 1. Introduction reversal symmetries. Therefore, assuming CPT invariance,the particle level EDMs of provide an CP indication violation of acrossviolation all will show sectors up of in particle an physics. EDM. As yet undiscovered sources of CP moment ( upper limit to the value. 2. Method quency shifts. The difference inelectric and precession magnetic frequency fields when is subjected directly to proportional parallel to the and electric antiparallel dipole moment ( EDM (nEDM) [ PoS(EPS-HEP 2009)376 C Clarke He which is a 1 m 3 Cold neutron beam of 12 ] which is produced in 6 1 meV which need to be ∼ He [ 4 Cooling I Tower UCN UCN detectors SQUIDs 3 From Cooling From II Tower Neutron Guides He is very pure with less than 1 part in 10 4 The components to the cryoEDM experiment. S.C. Shield & S.C. Solenoid Ramsey Ramsey Chamber ]. The 7 Figure 1: ]. They are silicon devices coated with lithium fluoride. Lithium reacts 8 He, neutrons lose energy by phonon production. These UCN are transported 4 HV feedHV Mu metal metal Mu shields 100 neV in order to achieve long storage times for precession, increasing the sensitivity ∼ After resonance, the neutrons are emptied from the resonance cells and counted by cryogenic In practice, a component of the difference in precession frequency will be from changing The H53 cold neutron beam at ILL provides neutrons with energies solid state detectors [ neutron absorber. In from the UCN source topotential the of resonance beryllium cells is through beryllium-coatedneutrons above are copper the stored guides. energy in of The cells the(termed Fermi made the from neutrons HV beryllium and cell) oxide. so has There the the is electric guides field a applied are two to cell reflective.3.2 it design and where Cryogenic The the Detectors one other cell cell is held neutral. situ through superleaks [ with neutrons to producecan two then charged be products: detected by an theparticles. silicon alpha A device layer and producing of a a magnetically spectrum polarised tritonup of iron neutrons two particle. on can peaks a be for detector These counted the reflects separately products two one from different spin spin polarisation down. so spin 3.3 Magnetic control and monitoring cell (Ramsey Chamber).operation. Not shown in the figure are the3.1 large High pumps density necessary source of for UCN cryogenic cooled to of the measurement. As theUCN neutrons are produced enter by the downscattering experiment, the they cold pass neutrons in through superfluid a neutron polariser. The cryoEDM experiment PoS(EPS-HEP 2009)376 C Clarke 97 cm and move to a T is produced by a e µ (1989) 33 Nuclear Instruments and 27 − 284 ] Physical Review Letters 2 m from the resonance cells so field of 5 ∼ B (2005) pp.399-403 45-6 4 hep-ph/0705.2008v2 (2003) 517-523 Cryogenics 501 ]. (2008) 577 [ 80 . To manage the effects of field fluctuations, the magnetic field needs , 695 (1950). n d 78 APS (2003) 67-74. cm with the sensitivity ultimately limited by systematic errors. This will e 308 28 hep-ph/0008248v2 − Phys.Rev. Nuclear Instruments and Methods in Physics Research Section A S.N. Ivanov, D.J.R. May, J.M. Pendlebury, D.B. Shiers, K.F. Smith, (2006) 131801. P.G. Harris, P. Iaydjiev, S.N. Ivanov, J.M.Physics Pendlebury, D.B. Letters Shiers, A M.A.H. Tucker and H. Yoshiki, Methods in Physics Research Section A J.M. Pendlebury, D.B. Shiers, M.A.H. Tucker, H. Yoshiki and P. Geltenbort, Superconducting quantum interference devices (SQUIDs) are used to monitor the fields down We are currently in the commissioning phase of the experiment at the H53 beam position at Magnetic shielding comprising three layers of mu metal and one superconducting lead shield [2] S. Dar, (2000) [ [3] J. Ellis, [4] C.A. Baker, D.D. Doyle, P. Geltenbort, K. Green, M.G.D. van der Grinten, P.G. Harris, P. Iaydjiev, [1] T. Ibrahim and P. Nath, [5] N.F. Ramsey, [6] C.A. Baker, S.N. Balashov, J. Butterworth, P. Geltenbort, K. Green, M.G.D. van der Grinten, [7] H. Yoshiki, H. Nakai and E. Gutsmiedl, [8] C.A. Baker, S.N. Balashov, K. Green, M.G.D. van der Grinten, P.S. Iaydjiev, S.N. Ivanov, to 0.1 pT over the free precession time of 300 s. They are located ILL. We plan to make a measurement of the nEDM with sensitivity 10 superconducting solenoid and trim coils.resonance cells To is prevent non-magnetic. local magnetic dipoles, all material near the they do not introduce additionalpick-up magnetic loops fields. around the The resonance SQUIDs cellsread are via out superconducting in connected flux-locked twisted to loop wire superconducting mode pairs. usingfor room The uninterrupted temperature SQUIDs tracking electronics are and of continuous the digitalisation magnetica field. neutron The resonance complementing cell the that SQUIDs. is held neutral also acts as 4. Conclusion position of higher intensity 9 Åof neutron of flux the in order 2012. 10 Atbe this sufficient position to we discover the will nEDM achieveplace a predicted a by sensitivity new many upper “beyond limit the on ” the theories nEDM, or severely constraining to theory. References reduces the external magnetic field. The homogenous holding The cryoEDM experiment magnetic fields and not just to be stable and knownchanges well in enough the for magnetic corrections fieldpotentially to produce that a be are false applied. correlated nEDM signal. with A reversals particular of concern the is electric from field as this could