The SNS neutron EDM experiment: overview and the Kerr-effect electric-field monitor

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1 The SNS neutron EDM experiment: overview and the Kerr-effect electric-field monitor Byung Kyu Park 1, Alex Sushkov 2, Darwin Windes 1, Dima Budker 1 (for the nedm collaboration) 1 Department of Physics, University of California, Berkeley 2 Department of Physics, Yale University 7th International UCN Workshop Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 1 / 29

2 Outline 1 The SNS nedm experiment: an overview 2 The SNS nedm experiment: current progress 3 Kerr-effect electric field monitor Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 2 / 29

3 State of the neutron EDM Currently: d n < e cm, Baker et al., PRL 97, (2006) Summary of current and expected experimental limits on nedm a CP violation in standard model (from K 0 decay) not enough to explain amount of matter in universe Stringent limit on extensions to the standard model Constrain or verify supersymmetry predictions in near future a Lamoreaux and Golub, The Neutron Electric Dipole Moment: Yesterday, Today, and Tomorrow in Lepton Dipole Moments, ed. Roberts & Marciano, 2009 Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 3 / 29

4 State of the neutron EDM Currently: d n < e cm, Baker et al., PRL 97, (2006) Summary of current and expected experimental limits on nedm a CP violation in standard model (from K 0 decay) not enough to explain amount of matter in universe Stringent limit on extensions to the standard model Constrain or verify supersymmetry predictions in near future a Lamoreaux and Golub, The Neutron Electric Dipole Moment: Yesterday, Today, and Tomorrow in Lepton Dipole Moments, ed. Roberts & Marciano, 2009 Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 3 / 29

5 SNS experiment: distinguishing features UCN production by superthermal method 1 with ultrapure superfluid 4 He and storage in the same cell UCN storage within the helium volume: Gain in neutron density by at 2 orders of magnitudes from previous experiments LHe is good dielectric higher applied electric field by factor of 4 Use of 3 He: as polarizer: selectively absorbs antialigned neutrons; improves neutron polarization from 90% to 95% as comagnetometer: precesses under B field and sees the same field as neutrons; control systematics related to magnetic fields as neutron detector: if neutron is absorbed, neutron was anti-aligned; if it is not absorebd, it was aligned 1 Golub and Pendlebury, Phys. Lett. A 62, 337 (1977) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 4 / 29

6 EDM sensitivity: statistics Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 5 / 29

7 EDM sensitivity: statistics E Ω L = µ B = γ B B Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 5 / 29

8 EDM sensitivity: statistics E + δe= µ B d E Ω L ± δω L = γ B B ± γ E E If state of n completely specified by existing quantum numbers, d µ Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 5 / 29

9 EDM sensitivity: statistics E + δe= µ B d E Ω L ± δω L = γ B B ± γ E E If state of n completely specified by existing quantum numbers, d µ Sensitivity: δω L 1 E NτT The SNS experiment: E 50 kv/cm N 150 per cm cm 3 τ 500 s for each measurement T 300 live days for initial duration of the experiment 2π δω L 2.6 µhz High electric field and density made possible by keeping neutrons in superfluid helium High voltage ( 500 kv) is produced without an actual high voltage supply with gain capacitors Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 5 / 29

10 EDM sensitivity: systematics v E effect For bottled UCN, only quadratic dynamic phase linear geometric phase may remain magnetic field fluctation correct with 3 He signal pseudomagnetic field in the presence of polarized 3 He significant but canceled with two-cell design geometric phase a occurs with B field inhomogeneity doesn t cancel between 3 He and n temperature-dependent From Conceptual Design Report for the nedm Project a Commins. Am. J. Phys. 59, 1077 (1991), Pendlebury et al. Phys. Rev. A 70, (2004) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 6 / 29

11 SNS nedm experiment: UCN source Beamline from SNS Superthermal production of UCN a in ultrapure superfluid 4 He at 0.5 K final neutron temperature: 3 mk a Golub and Pendlebury, Phys. Lett. A 62, 337 (1977) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 7 / 29

12 SNS nedm experiment: 3 He comagnetometer comagnetometers: measure local magnetic field fluctuations Hg comagnetometers successfully used before 3 He occupy same volume as neutrons in superfluid 4 He: ideal comagnetometer for SNS experiment 3 He precession signal detected by externally-placed SQUIDs Harris et al., Phys. Rev. Lett. 82, 904 (1999) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 8 / 29

13 SNS nedm experiment: 3 He neutron detector n + 3 He p + 3 H kev reaction products produce UV scintillation light (80 nm) in the LHe 2 UV scintillation light down-shifted (430 nm) and detected greater cross section (by factor of 200) in the singlet state measures beat frequency between Ω L, 3 He and Ω L,n (small because gyromagnetic ratio is the same within 10%) Figure from W. Korsch s talk at PANIC08, The SNS Neutron EDM Experiment 2 Doyle and Lamoreaux, Europhys. Lett. 26, 253 (1994) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 9 / 29

14 SNS nedm experiment: 3 He neutron detector Optimization of initial 3 He and n angle Calculation by Pinghan Chu for nedm collaboration Change in Ω L,n without change in Ω L, 3 He nedm 3 He has negligible EDM: d199 Hg < e cm, and EDM of diamagnetic atom varies as Z 2 Dressed spin technique a modify effective gyromagnetic ratio with oscillating B field so that γ n = γ 3 He (critical dressing) optimize sensitivity to d n by appropriate choice of initial angle: as much as a factor of 2 increase in sensitivity a Golub and Lamoreaux, Phys. Rep. 237, 1 (1994) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 10 / 29

15 SNS nedm experiment: Measurement Cycle 1 Diffuse polarized 3 He atoms into the measurement cell 2 Illuminate the measurement cell with polarized cold neutrons to produced polarized UCN aligned with the 3 He atoms 3 Apply π/2 pulse to rotate spins to be perpendicular to the magnetic field 4 Make precession frequency measurements 5 Remove 3 He atoms from the cryostats by diffusion to the purifier 6 Reload the collection volume with polarized 3 He from the ABS 7 Return to step sec 1000 sec 10 sec 500 sec 100 sec (300 sec, during other steps) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 11 / 29

16 SNS nedm Experiment: progress Basic R&D done, including: valve test: 10,000 cycles without failure 3 He relaxation time: measured at Duke and UIUC; results agree and meet project requirement UCN storage time: 300 s at 20K in vacuum with same wall coating Dielectric breakdown in superfluid 4 He: 50 kv/cm at 7-cm separation cos θ coils tested for magnetic field homogeneity LHe scintillation test with HV: major components successfully tested Design optimization and engineering currently in progress Building construction in progress Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 12 / 29

17 Measurement Cell Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 13 / 29

18 3 He services Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 14 / 29

19 Apparatus Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 15 / 29

20 Building Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 16 / 29

21 Building (April 2009) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 17 / 29

22 Building (May 2009) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 18 / 29

23 The nedm collaboration M. Ahmed 7, R. Alarcon 1, R. Allen 16, A. Apostol 11, A. Avakian 4, S. Baessler 19, S. Balascuta 1, L. Bartoszek 2, D. Beck 8, E. Beise 12, J. Boissevain 11, B. Bourque 11, H. Breuer 12, D. Budker 3, M. Busch 7, J. Chacon 11, C.-Y. Liu 9, P. Chu 8, V. Cianciolo 16, S. Clayton 11, M. Cooper 11, C. Crawford 10, K. Dow 13, J. Dunne 14, D. Dutta 14, A. Esler 8, M. Espy 11, B. Filippone 6, A. P. Galvan 6, H. Gao 7, R. Golub 15, T. Gorringe 10, C. Gould 15, G. Greene 16, D. Haase 15, D. Hasell 13, M. Hayden 17, E. Hazen 4, R. Hennings-Yeomans 11, P. R. Huffman 15, E. Ihloff 13, T. Ito 11, J. Kelsey 13, A. Kolarkar 4, E. Korobkina 15, W. Korsch 10, S. Lamoreaux 20, V. Logashenko 4, J. Long 9, M. Makela 11, A. Matlachov 11, C. M. Mauger 11, B. Mckeown 6, D. McKinsey 20, M. Mendenhall 6, H. Meyer 9, F. Mezei 11, J. Miller 4, R. Milner 13, E. Olivas 11, J.-C. Peng 8, B. K. Park 3, S. Penttila 16, B. Plaster 10, J. Ramsey 11, R. Redwine 13, L. Roberts 3, I. Savukov 11, R. Schmid 6, J. Seele 13, G. Seidel 5, M. Snow 9, W. Sondheim 11, S. Stanislaus 18, A. Sushkov 20, C. Swank 15, S. Tajima 7, J. Torgerson 11, E. Tsentalovich 13, C. Vidal 13, P. Volegov 11, W. S. Wilburn 11, S. Williamson 8, D. Windes 3, H. Yan 10, A. Q. Ye 7, J. Yoder 8, A. R. Young 15, W. Zheng 7, X. Zhu 7 1 Arizona State University, Tuscon, AZ; 2 Bartoszek Engineering, Aurora, IL; 3 University of California, Berkeley, CA; 4 Boston University, Boston, MA; 5 Brown University, Providence, RI; 6 California Institute of Technology, Pasadena, CA; 7 Duke University, Durham, NC; 8 University of Illinois, Urbana-Champaign, IL; 9 Indiana University, Bloomington, IN; 10 University of Kentucky, Lexington, KY; 11 Los Alamos National Laboratory, Los Alamos, NM; 12 University of Maryland, College Park, MD; 13 Massachusetts Institute of Technology, Cambridge, MA; 14 Mississippi State University, Mississippi State, MS; 15 North Carolina State University, Raleigh, NC; 16 Oak Ridge National Laboratory, Oak Ridge, TN; 17 Simon Fraser University, Burnaby, BC, Canada; 18 Valparaiso University, Valparaiso, IN; 19 University of Virginia, Charlottesville, VA; 20 Yale University, New Haven, CT 90 members from 20 institutions Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 19 / 29

24 Kerr-effect electric-field monitor Need to measure electric field directly E field requirements: at least 1% homogeneity within the cell, and precise reversal of E field for systematics (quadratic v E) presence of dielectric can affect reversing electric field charge accumulation on acrylic plates can affect electric field Kerr effect probes electric field in the medium itself Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 20 / 29

25 Optical access for Kerr monitor small LHe Kerr constant a : (cm/v) 2 expected ellipticity in SNS experiment: 10 µrad stress-induced birefringence in optical windows: offset on the order of mrads and drifts on the order of 100 µrad over 100 seconds solution: cancel the noise out cancellation demonstrated to 1% of the noise in a mock-up setup b Original cancellation scheme a Sushkov et al., Phys. Rev. Lett. 93, (2004) b Park, Sushkov, and Budker, Rev. Sci. Instr. 79, (2008) Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 21 / 29

26 Kerr monitor: demonstration in a mock setup Cancellation in real time Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 22 / 29

27 Kerr monitor: demonstration in a mock setup Better cancellation with integration over 10 s Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 23 / 29

28 Kerr monitor: implementation within nedm apparatus Early conceptual design Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 24 / 29

29 Kerr monitor: implementation within nedm apparatus Early conceptual design Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 25 / 29

30 Kerr monitor: implementation within nedm apparatus Recent design illustrations from John Ramsey Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 26 / 29

31 Kerr monitor: implementation within nedm apparatus Recent design illustrations from John Ramsey Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 27 / 29

32 Kerr monitor: implementation within nedm apparatus Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 28 / 29

33 Summary The nedm collaboration plans to measure the electric dipole moment of the neutron with precision of δd n e cm, 2 orders of magnitude improvement from the current limit High intensity neutron beam from SNS and new UCN production technique gives UCN density two orders of magnitudes higher than previous experiments Highest applied electric field to date Local electric field strength to be monitored to 1% accuracy using Kerr effect in LHe Start collecting data in 2016? Park (for nedm collaboration) (UC Berkeley) SNS nedm experiment 7th UCN workshop 29 / 29