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Cold and slow molecular beams: Application to electron electric dipole moment (EDM) measurements

Cold and slow molecular beams: Application to electron electric dipole moment (EDM) measurements. Katsunari Enomoto , Univ. of Toyama. Fundamental Physics U sing Atoms 2010 2010/Aug/9 Osaka U. Electron electric dipole moment. spin. spin. EDM. T, P. electron.

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Cold and slow molecular beams: Application to electron electric dipole moment (EDM) measurements

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  1. Cold and slow molecular beams: Application to electron electric dipole moment (EDM) measurements Katsunari Enomoto, Univ. of Toyama Fundamental Physics Using Atoms 2010 2010/Aug/9 Osaka U.

  2. Electron electric dipole moment spin spin EDM T, P electron EDM related with CP, T violation physics Standard model electron EDM de 10-38 e cm SUSY, left-right, multi-Higgs de< 10-24 e cm de< 10-27 e cm Experiment (Tl atomic beam) PRL 88, 071805 (2002). Table-top experiment for the physics beyond the standard model.

  3. EDM measurement using atoms E // B Typical atomic beam method E // B or S precession B1 nT Eappl0.1 MV/cm  t Due to the relativistic effect, heavy atoms have large enhancement factor R. (Cs: R110, Tl: R590, Fr: R1150) h B Eeff = R Eappl 0.1 GV/cm,   deEeff / h  10 Hz m=1/2 m=1/2 False EDM signal (systematic error) Leak current loop v  E induced field v I E

  4. EDM measurement using molecules atom molecule permanent dipole Induced dipole |p mix with Eappl |J=1 mix with Eappl Eeff Emol rot. |J=0 elec. |s Eeff = R Eappl 0.1 GV/cm, with Eappl 0.1 MV/cm Eeff = P Emol 10100 GV/cm, P  1 with Eappl  0.01 MV/cm (Eappl is needed just for aligning molecule) Sensitivity  1001000 Systematic error  0.1

  5. Atoms vs molecules Tl beam experiment YbF beam experiment PRL 88, 071805 (2002). vs PRL 89, 023003 (2002). de< 10-27 e cm de< 10-25 e cm Why is it not so good? …. because radical molecular beams are difficult to produce, and molecules have many internal levels (especially rotation). Vibration (1000 K) Rotation ( 1K) Cold (large population in the ground state) and slow (long interaction time) molecular beam will improve greatly the sensitivity. In this talk, after reviewing cold molecule experiments, I will present our recent results and ongoing projects.

  6. Ultracold molecules Ultracold molecules are one of the hottest topics in atomic/molecular/optical (AMO) physics in this decade. New condensed matter High resolution spectroscopy Quantum simulator Test of fundamental physics Ultracold chemistry Direct cooling of molecules (mK) Laser cooling of atoms and associating to molecules (nK) Control of chemical reaction

  7. Direct cooling methods (1) Supersonic expansion is a conventional method for molecular spectroscopy, and it generates cold (1 K) but fast (supersonic) molecular beams. How to slow down? Stark decelerator & electrostatic trap Bethlemet al., Nature 406, 491 (2000). Counter-rotating nozzle Gupta et al, J. Phys. Chem. A 105, 1626 (2001)

  8. Direct cooling methods (2) Laser ablation can generate molecular gases in cryogenic helium gas (1 K). Effusive molecular beam Maxwell et al., Phys. Rev. Lett. 95, 173201 (2005) Hydrodynamically enhanced-flux (but boosted to 160 m/s) molecular beam Buffer-gas cooling & magnetic trap Weinstein et al., Nature 395, 148 (1998) Patterson et al., J. Chem. Phys. 126, 154307 (2007)

  9. Control of translational motion Now, molecules can be cooled/decelerated down to 1 K. Many tools are available to control molecular translational motion, e.g. electric & magnetic static field, optical field, … Our approach: using microwave field Stark shift of diatomic molecules Advantage of microwave: High-field-seeking (HFS) ground state can be trapped. DeMilleet al, Eur. Phys. J. D 31, 375 (2004) HFS state cannot be trapped with static fields due to Earnshaw’s theorem.

  10. Microwave trap for molecule It has been proposed to a microwave field enhanced in a Fabry-Perot cavity to trap polar molecules. For static field (dc Stark shift) (J=0,1 states) For microwave field (ac Stark shift) DeMilleet al, Eur. Phys. J. D 31, 375 (2004) • 2B: rotational splitting • : detuning • d : dipole moment of molecule Electric field E  (P  Q)1/2 Assuming power P 2 kW, quality factor Q 105, Electric field E  30 kV/cm ( 3 K trap depth) is possible.

  11. Microwave Stark decelerator We proposed that HFS state molecules can be decelerated by using time-varying standing wave of microwave. Enomoto & Momose, PRA 72, 061403 (2005) Current plan: to use circular waveguide resonatorTE11mode TE11 Radial confinement for HFS state Potential w/o microwave Potential w/ microwave Alternate gradient focusing decelerator Bethlem et al., PRL 88, 133003 (2002) Tarbutt et al., PRL 92, 173002 (2004) More powerful, but dynamical radial confinement

  12. Simulation of deceleration Molecule : 174YbF Initial velocity : 21 – 24 m/s Center molecule : 22.5 m/s (5.8 K) Deceleration : 93 cm, 80 ms P[W]  Q : 107 Microwave Stark decelerator can be used for molecular beams pre-cooled to about 5 K.

  13. First experimental step: microwave lens w/o microwave Molecular beams can be focused with a microwave field. w/ microwave Performed in Fritz-Haber institute by using a decelerated NH3 beam Odashima et al., PRL 104, 253001 (2010)

  14. Next plan for microwave control Electric field E2 (power P)  (quality factor Q) High P needs expensive amps and causes heating. So we are planning to use a superconducting cavity for high Q. (Q factor is mainly determined by the surface resistance.) Lens exp. (Cu cavity) SC cavity (Nb or Pb/Sn) Limited by cooling power (Note that only 0.1 s is needed for deceleration.) Power P[W] 3 < 3 ? Q > 106 is typically easily obtained, but we have to rapidly switch microwave. This limits the Q factor. Q-factor 5000 3106 ? P  Q 1.5 104 107 ? We will test the superconducting cavity soon in U. British Columbia (Momose lab.)

  15. Project in Univ. of British Columbia We are constructing a Stark decelerator in UBC. We will combine the Stark decelerator with superconducting cavity.

  16. Testing a microwave resonator Firstly, we tested a copper resonator with a loop antenna. loop antenna QL 5000 Cool down with L.N2 Q factor  3 QL 16000 We will test a Pb/Sn-coated superconducting cavity soon.

  17. Project in Univ. of Toyama We are making cold molecular beams based on He buffer-gas cooling. L. He bath He gas line To mass spectrometer exit hole Laser ablation (pulsed green laser) sorption pump We have observed Pb and O atoms produced by laser ablation of a PbO target with mass spectrometer.

  18. EDM measurement project We are starting the EDM measurement project in Univ. of Toyama from this year. Only the project plan is presented here. What molecules? How to produce molecules? How to cool them to a few K? How to enhance the flux? What more?

  19. Choice of molecule unpaired electron Large electro- negativity Heavy atom To obtain high beam flux in a single internal state Low boiling point (even for laser ablation) Small nuclear spin (simple hyperfine structure) large natural abundance From experimental point of view Less toxic Not radioactive Tentative plan: to use YbF (like E. Hinds group, Eeff = 26 GV/cm) or BaF(Eeff = 8 GV/cm)

  20. Cooling procedure Supersonic jet Initial velocity is determined by carrier gas high room T e.g. YbF in Xe 300 m/s corresponds to 1000 K for YbF Hydrodynamic He buffer-gas-cooled beam Initial velocity is determined by He gas (160 m/s  300 K for YbF) density and directionality 4 K, high He density Effusive He buffer-gas-cooled beam Initial velocity is determined by the cell temperature ( 4 K) low 4 K, low He density We will use He buffer-gas-cooled beam close to effusive regime.

  21. Improvement of flux How to generate molecules? Laser ablation Injection from oven oven 1012 /pulse poor reproducibility 1015 /s ? (like J. Doyle group) How to improve directionality? Microwave lens Laser cooling (SrF: Shuman et al., PRL 103, 223001 (2009).) They also help isotope selection  suppression of background noise Future possibility Microwave deceleration and trap Combination of alternate gradient decelerator and microwave decelerator

  22. Conclusion Microwave enhanced in resonators is available to control molecular translational motion (such as deceleration and trap). As a first step, we demonstrated the microwave lens. Odashima et al., PRL 104, 253001 (2010) We will test soon a high-Q superconducting resonator. For electron EDM measurement, we are making He-buffer-gas- based cold molecular beam (YbF or BaF). EDM measurement with molecular beams with cold molecule technologies developed in this decade is promising.

  23. Acknowledgments Microwave lens experiment H. Odashima, S. Merz, M. Schnell, G. Meijer (Fritz-Haber-Institut) Superconducting cavity project O. Nourbakhsh, P. Djuricauin, T. Momose, W. Hardy and his students (Univ. of British Columbia) Buffer-gas cooled beam project Y. Kuwata, H. Noguchi, H. Hasegawa, S. Tsunekawa, K. Kobayashi, F. Matsushima, Y. Moriwaki (Univ. of Toyama) And courtesy of D. DeMille

  24. 77K shield 分子ビーム 4K shield チャコール セル

  25. マイクロ波定在波 TE11 TE01 マイクロ波定在波あり マイクロ波定在波なし Fabry-Perot TEM00

  26. 光ポンピング B state J’=1 Diode laser マイクロ波 トラップ J=1 J=0 X state pump He gas L. He Q-mass PbO pump pulse YAG pump pump シュタルク ガイド

  27. LFS HFS Bethlemet al., PRA 65, 053416 (2002).

  28. Stark UBC Microwave Lens (collimation) deceleration trap Buffer gas Cold slow beam EDM measurement Toyama

  29. Acknowledgment FHI UBC Toyama

  30. Atoms or molecules? vib. atom molecule Induced dipole mix with Eappl elec. rot. mix with Eappl to align molecule Large internal electric field (Eeff 10 GV/cm) Easy to handle Rotation and vibration exist (small population in the ground state at room temperature, which reduce statistical certainty) High electric field Eappl is needed (causing systematic error) Eeff 500 Eappl, Eappl  100 kV/cm de< 10-27 e cm Experiment (Tl atomic beam) PRL 88, 071805 (2002). Experiment (YbF molecular beam) de< 10-25 e cm PRL 89, 023003 (2002). Cold molecular beam (or trapped molecules) will improve much more.

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