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Searching for a nEDM at PSI

Searching for a nEDM at PSI. P. Schmidt-Wellenburg on behalf of the PSI-nEDM collaboration. The collaboration. 6 countries 14 institutions 45 members. UCN source at PSI. Proton Accelerator 590 MeV Cyclotron 2.2 mA beam current. See talk by B. Lauss. nEDM. UCN Source.

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Searching for a nEDM at PSI

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  1. Searching for a nEDM at PSI P. Schmidt-Wellenburgon behalf of the PSI-nEDM collaboration

  2. The collaboration • 6 countries • 14 institutions • 45 members

  3. UCN source at PSI Proton Accelerator 590 MeV Cyclotron 2.2 mA beam current See talk by B. Lauss nEDM UCN Source 2 experimental areas / 3 beamlines

  4. Outline • The apparatus • Ongoing measurements and results • UCN - performance • Magnetometers and field control • High voltage and leakage currents • Ideas for the next generation experiment

  5. Apparatus overview

  6. The apparatus • 2009 Transfer from ILL (France) toPSI (Switzerland) • Setup in thermally stabilized wooden house • Two independent air-conditionings • Six coils for surrounding field compensation (SFC)

  7. Outline • The apparatus • Ongoing measurements and results • UCN - performance • Magnetometers and field control • High voltage and leakage currents • Ideas for the next generation experiment

  8. UCN operation Empty Filling Monitor A. Serebrov et al., NIMA 545(2005)490

  9. UCN 6Li depleted 3H Signal (mV) 6Li 110 µm 60 µm  6Li enriched Time (ns) UCN detector • 6Li doped glass scintillator stack • 9 independent channels (PMTs +DAQ) • High count rate capable > 10 M G. Ban et al., NIMA 611 (2009) 280

  10. UCN Detector • Monitor mode ~70000 UCN • Emptying ~30000 UCN • High UCN losses • High depolarization rate G. Ban et al., NIMA 611 (2009) 280

  11. τflip = 236 sτloss =16.5 sτ↓ = 163 s τ↑ = 16.9 sN= 29185α0 = 0.999 Best fit to data UCN emptying curve • During emptying: high loss rate of stored spin component → wrong polarisation

  12. UCN storage time

  13. Rough adjustment of trim coils UCN detection spin sequence not yet optimized UCN Spin performance

  14. UCN Ramsey cycles Ramsey curve taken with 250 s precession time

  15. Sensitivity E=110/12 kV/cm N10=9838 N20=8042 T1=56.6 s T2=182.5 s α0=0.79 Tα=556.6 s Minimum: σ(219s)=5.94×10-24e·cm → σ(1d)=4×10-25 e·cm Assuming 30 x more UCN

  16. Outline • The apparatus • Ongoing measurements and results • UCN - performance • Magnetometers and field control • High voltage and leakage currents • Ideas for the next generation experiment

  17. The measurement technique Measure the difference of precession frequencies in parallel/anti-parallel fields: RAL-Sussex-ILL:dn< 2.9 x 10–26e cmC.A.Baker et al., PRL 97 (2006) 131801 for dn<10-26 ω< 60 nHz

  18. Magnetic shield • Four layer Mu-Metal • Shielding factors:x: 12000, y: 3000, z:8000

  19. Surrounding field compensation • Surrounding field (~ 80μT) • Compensation and stabilization • Three coil pairs: • 6m x 8m, d= 4m • 9/18 windings • Six current supplies(10/20 A) • Ten 3-axis Fluxgates (FG)

  20. Sensor positions Z Monitoring positions close to shield (~ 0.3…0.8 m) nEDM Coordinate system FG 9 FG8 FG3 FG6 FG1 Al frame Y FG5 FG7 Thermo house (first floor) Magnetic shield door FG0 FG2 X

  21. Results • Feedback with inverted & regularized Matrix • Twelve sensors close to shield taken into account • (for x-direction shown below: • sensors 0x, 3x, 6x, and 8x are used)

  22. Most important source of systematic effects →Field mapping →Online Cs-OPM measurement →Dedicated B-drift runs (ramping E-field) →Magnetic scanning at PTB, Berlin Systematic effects × 10-27

  23. Hg co-magnetometer See talk by D. Rebreyend

  24. Principle of Cs magnetometer

  25. Cesium magnetometers • Two cesium magnetometer arrays • Stabilized laser • PID phase locked DAQ Monitoring of vertical magnetic gradients ±140kV 1 2 3 4 5 … 11 12

  26. Homogenizer and fiber bundle Fiber bundle Beam splitter mounted on the enclosure support 31 vacuum feedthroughs for optical fibers

  27. Measure the response of all n=17 magnetometers to changes of each m=33 individual coil current Known response allows to calculate ideal currents for given field setting(iterative process) Adjusting field gradients 10nT 10pT

  28. Gradients • STD from six gradiometer pairs

  29. Outline • The apparatus • Ongoing measurements and results • UCN - performance • Magnetometers and field control • High voltage and leakage currents • Ideas for the next generation experiment

  30. High voltage • Cesium work with HV • HV did not work with Cs • HV works up to 200kV • Flashovers along fiber bundles • Reliable HV runs at ±150kV Tests 3 Leakage current @ 195 kV 2 nA 1 15:06 15:14

  31. Testing high voltage Configuration w bundle -110 kV vacuum 145 kV He/Ne Configuration wo bundle 198 kV He/Ne 200 kV He/Ne

  32. Leakage current • Changing the polarity of the high voltage will change the direction of the leakage current, and hence the magnetic field produced by these currents • Most contribution of the leakage currents cancel out, not so jφ. Leakage currents are caused by the high voltage and appear along the surface of the insulator ring. jr jφ jφ jr jz jφ A leakage current of 1 nA produces a false edm of 2 × 10 -28 e cm

  33. 0.9 0.6 0.3 ILeak (nA) 0.0 -0.3 ILeak ≤ 0.5 nA σ ≤ 0.1 × 10-27e cm -0.6 -0.9 -80 -60 -40 -20 0 20 40 60 80 UHV (kV) Leakage current measurement • Monitoring of leakage currents on ground electrode • Combination of protection circuit and highly sensitive current/voltage amplifier 3.5600 FEMTO 3.5595 3.5590 3.5585 3.5580 Current (nA) 3.5575 3.5570 0.75pA 4 pA 3.5565 3.5560 3.5555 0 2 4 6 8 10 Time (h)

  34. Outline • The apparatus • Ongoing measurements and results • UCN - performance • Magnetometers • High voltage and leakage currents • Ideas for the next generation experiment

  35. Simultaneous measurement in 2 precession chambers Laser based Hg co-magnetometer 3He magnetometers Multiple Cs magnetometers for 3He readout and gradients UCN chamber position at PSI UCN beam height n2EDM: General concept E E 3He see talk by A. Kraft

  36. Thermohouse2 • 10×6×8 m3 • EMC shield made of copper • Thermally stabilized

  37. Conclusion & Outlook • Apparatus is ready for data taking • Presently remeasuring UCN parameters • High quality adjustment of B-field gradients • Excellent performance of high voltage • nEDM data taking from Nov 2012 • 400 nights of data in 2013/2014→σ < 5×10-27e·cm • In parallel design of next generation experiment →σ < 5×10-28e·cm

  38. Physikalisch Technische Bundesanstalt, Berlin Laboratoire de Physique Corpusculaire, Caen Institute of Physics, Jagiellonian University, Cracow Henryk Niedwodniczanski Inst. Of Nucl. Physics, Cracow Joint Institute of Nuclear Reasearch, Dubna Département de physique, Université de Fribourg, Fribourg Laboratoire de Physique Subatomique et de Cosmologie, Grenoble Biomagnetisches Zentrum, Jena Katholieke Universiteit, Leuven Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, Orsay Inst. für Kernchemie, Johannes-Gutenberg-Universität, Mainz Inst. für Physik, Johannes-Gutenberg-Universität, Mainz Paul Scherrer Institut, Villigen Eidgenössische Technische Hochschule, Zürich M. Burghoff, A. Schnabel, J. Vogt G. Ban, V. Helaine1, Th. Lefort, Y. Lemiere, O. Naviliat-Cuncic, G. Quéméner K. Bodek, G. Wyszynski3, J. Zejma A. Kozela N. Khomutov Z. Grujic, M. Kasprzak, P. Knowles, H.C. Koch4, A. Weis G. Pignol, D. Rebreyend S. Afach, G. Lembke N. Severijns, P. Pataguppi S. Roccia C. Plonka-Spehr, J. Zenner1 W. Heil, A. Kraft G. Bison, Z. Chowdhuri, M. Daum, M. Fertl3 , B. Franke3, B. Lauss, A. Mtchedlishvili, D. Ries3, PSW, G. Zsigmond K. Kirch1, J. Krempel, F. Piegsa The Neutron EDM Collaboration also at: 1Paul Scherrer Institut, 2PNPI Gatchina, 3Eidgenössische Technische Hochschule, 4GUM Mainz

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