Radium Atom. Electron and Nuclear EDM s. Trapped Radioactive Isotopes: µ icro laboratories for Fundamental Physics

Transcription

1 Radium Atom Electron and Nuclear EDM s TRIµ P: Trapped Radioactive Isotopes: µ icro laboratories for Fundamental Physics Lorenz Willmann, University of Groningen, KVI PandT2008, Heidelberg, 9 June 2008

2 Outline TRIµ P Facility at KVI EDM s and the Standard Model What about Radium? Laser Cooling and Trapping Heavy Alkaline Earth Elements: Barium (and Radium) Trapped Barium Isotope shifts in Barium Summary

3 Magnetic Separator Ion Catcher RFQ Cooler Atomic Physics Production Target Nuclear Physics AGOR cyclotron Particle Physics Magnetic separator Wedge Q MeV D Q Q kev Q D D Q D Q Production target Q Q ev mev MOT Beyond the Standard Model TeV Physics TRIµ P project and facility thermal ioniser RFQ cooler/buncher nev AGOR cyclotron MOT MOT Low energy beam line Trapped Radioactive Isotopes: µ icro laboratories for Fundamental Physics

4 TRIµ P Facility: Lasers Several experiment Flexibility: diode lasers, dye laser, Ti:Sapph, and others 2 different wavelength up and running Equipment for stabilization and frequency determination Typically more than one laser (7 for Barium atom trapping) Power [mw] dye laser Ti:Sapph Wavelength [nm] Trapped Radioactive Isotopes µ icro laboratories for Fundamental Physics

5 The Standard Model The Standard Model 3 Fundamental Forces: Electromagnetic Weak Strong 2 Fundamental Fermions: Leptons, Quarks 2 Gauge Bosons: γ, W+, W, Z0, 8 Gluons validated by many experiments Large variety of models extending SM Experimental verification required High energy experiments Precision experiments However, many open questions Exactly three generations? ~ 30 free parameters? Matter predominant? Sources of CP violation? Dark matter and dark energy? Moreover, problems remain Gravity not included in the SM No combined theory of Gravity and Quantum Mechanics Trapped Radioactive Isotopes: μicro laboratories for Fundamental Physics weak interaction β decay studies (2Na, ) APV (Ra Ion) Electric Dipole Moments (Ra Atom)

6 EDM Experiments Worldwide Fundamental particles, nucleons, atoms, molecules and crystals Limits of the EDM from some measurements.6x x x x orders of magnitude larger than the Standard Model prediction. Large window in new physics

7 EDM s in time molecules Hg de (SM) < 0 37

8 Measuring an EDM of Neutral Particles H = (d E + μ B) I/I B E d ω ω= 2 B 2dE h B µ E d ω2 ω2 = 2 B 2dE h h(ω ω ) 2 d= 4E mi = /2 µ ω ω 2 mi = /2 d = 0 25 e cm E = 00 kv/cm ω = 5 *0 5 rad/s

9 Fortson Group Seattle, Washington From M. Romalis

10 Possible Routes Cells high density motional fields average to zero long coherence times Beams ultra high vacuum leakage current suppression higher electric fields coherence time limited by length of beam Traps? no motional electric field, higher density long storage time long observation times ultra high vacuum high electric fields possible small sample region homogeneity New Systems New production facilities for short lived isotopes

11 What about Radium? A=88, alkaline earth element Ground state [Rn] 7s2 S0 No stable isotope 226 Ra, τ /2 = 600 yrs, g RaCl > Activity of Ci Interesting isotopes 225 Ra, I=/2, τ /2 = 4.7 d 223 Ra, I=3/2, τ /2 = 5 d 23 Ra, I=/2, τ /2 = 2.7 min

12 Radium Spectroscopy Data Radium hollow cathode, large grating spectrometer Ebbe Rasmussen, Z. Phys, 87, 607, 934; Z. Phys, 86, 24, 933. Resolution ~ 0.05 A, 99 lines. 30 listed in NIST Database [A] S0 P S0 3P Corrections in deduces energy levels, Level assignment. Some levels shifted by 640 cm H.N. Russel, Phys. Rev. 46, 989 (934) Similar to Barium identification as alkaline earth element [A]

13 Why Radium? Atomic energy level diagram of Ra 7s7p P 2 7s6d D2 7s7p P nm 7s2 S0 Nearly degenerate opposite parity 3 P and 3D2 enhancement > ~ e EDM 0 7s6d 3D D2 er 3P 3 P H EDM 3 D2 d E ( 3D2 ) E ( 3 P ) V. A. Dzuba et al. Phys. Rev. A, 6, (2000) Density distribution of nuclear charge has mixed octupole and quadrupole deformation Deformed charge distribution in some isotopes (225Ra). Nucleon 2 J. Engel et al. Phys. Rev. C, 68, 02550EDM (2003) enhances 0

14 Radium Discharge and Hollow Cathode Atom, E. Rasmussen, Z. Phys, 86, 24, (933) Ion, E. Rasmussen, Z. Phys, 87, 607, (934) Absorption Cell Rydberg series > ionisation potential F.S.Tompkins, B. Ercoli, Appl. Opt. 6, 299 (968) Laser 7s2 S0 7s7p P, S0 3P, and 3P2 3D3 S.A. Ahmad et al., Phys. Lett. B 33, 47 (893) & Nuclear Physics A483, 244 (988). K. Wendt et al., Z. Phys. D 4, 227 (987). Argonne National Lab 3 D P transition J.R. Guest el al., Phys. Rev. Lett. 98, (2007)

15 Periodic Table of Elements TRIµ P

16 Laser Cooling of Radium and Barium P P 488 nm 2.8 µ m 428 nm nm 3 2 D2 3 P 0 30 nm D nm 500 nm D2 P nm 3 74 nm Leak rate without repumping Leak rate without repumping 350 : S0 Radium D 330 : S0 Barium 3 2

17 Comparison of Alkaline Earth Elements Cooling on S0 P: 0 v [m/s] v = vrecoil*nscatter 0 8 Radium intercombination line m/s Be Mg Ca Sr Alkaline earth elements Ba Ra

18 Trappist s View 7s 7p P Repumping necessary *0 s 5 3*05 7s 6d D2 3*04 s 2 4*03 s 2.2*08 s Cooling Transition 7s 7p 3P.6*06 s 0 7s 6d 3D 3 2 Repumping Weaker line, second stage cooling 7s2 S0 Preliminary Transition Rates as calculated by K. Pachucky (also by V. Dzuba et al.)

19 Competition at Argonne National Lab R. Holt, Lepton Moments 2006: Trapping efficiency < 0 6, ~ 20 atoms in trap J.R.Guest et al., PRL 98, (2007) Limited by cooling and trapping on intercombination line

20 Barium

21 Barium MOT λ, λ2,, λ3 R> coil II PMT I λ / L> 4 λ / 4 L> atomic beam Velocity λ λ λ λ, λ2, λ3 L> coil I z y x λ / 4 I R> L> λ, λ2, λ3 IR2 IR3, λ, λ IR2, λ IR3 IR

22 Laser Setup 500 nm (5 mw, δ= 0 MHz) 30 nm (40 mw, δ= 0 MHz) λir diode laser Pmt with filter at λ or λb Vertical MOT beam not shown Slowing beam λ 25 mw, δ = 220 MHz λir2 λ /4 λ /4 λ /4 λ /4 diode laser Ba Oven ~ 820 K mag. field coils 90 mw λir3 fiber laser λit3 fiber laser MOT beams 20 mw, Ø=2 mm δ = 0 MHz trapping laser λ λ3 diode laser 0 mw λir2 fiber laser 500 nm, 5 mw, δ = 80 MHz 30 nm, 25 mw, δ = 05 MHz

23 τ MOT ~s at 0 8mbar Atom losses in dark states Trapping laser Intensity I 3 > photoionisation 2.5 x 05 Decay time.0(5) s 2 Count rate [/s] P=4 0 9mbar Time [s] 4 6

24 Trapping of Barium Atoms λ 5d6p 3D = 43.3 nm λ = nm 5 2 x 0 50 MOT signal Results of trapping: 30capture of full velocity spectrum about %.5 s trap20lifetime D S0 Fluorescence [Counts/s] Doppler free beam signal (*00) 8 0 Improvements possible: 00 Increase laser power in infra red 90 (OPO) Transverse cooling 60 Frequency broadening cooling laser 50 MOT P S0 Fluorescence [Counts/s] 0 40 λ = nm Detuning [MHz] Longitudinal velocity of the atoms [m/s] 500 Building laser system for Radium trapping S. De, L. Willmann, 3 Oct 2007

25 Two Photon (Raman) transitions Λ System 6s6p P Rabi frequency Ω ge = < g er.e0 e> 2 Ω nm nm 6s5d D2 Ω 6s2 S0 2 ħ Ω 3 3 er electric dipole operator E0 Electric field In case of two coherent laser field (for >> Ω 2,Ω 23) Ω 3 = Ω 2Ω 23/2

26 Two Photon (Raman) transitions Example 3D state d2 3D2o Normalized P S0 fluorescence from MOT Large population of metastable states But: atoms remain in MOT Detuning 659.7nm laser [MHz]

27 Testing Calculations

28 MOT: Lifetime of 3F2 state 3 D2 667nm pulse populated 3F2 state τ = 90µ s ~ 93 % cascading back into cooling cycle Calculations of energy levels and transition rates for barium and radium V.A. Dzuba and V.V. Flambaum, arxiv:physics/0609 Other Publication ~ 68 % cascading back

29 MOT: Lifetime of 3F2 state D2 667nm pulse populated 3F2 state 6% losses from cooling cycle Excellent agreement with recent calculation Loss to other states Transfer to 3F2 Normalized MOT signal MOT Fluorescence 3 ms τ = 30(25) µ s Time [micro s].5 2 Time [ms]

30 Isotope shifts: 5d6s 3D 6s6p P transition Ba Ba 36 Ba Isotope selective population with intercombination line Coupling to nuclear spin Ba 37 Ba 35 I=0 I = 3/2 U. Dammalapati et al., arxiv:

31 Isotope shifts ν IS = ν ν FS Normal mass shift NMS + ν specific mass shift SMS + Field shift F δ <r2> (ν me/mp + FSMS ) (A A2)/AA2 FSMS electron correlation part Modified shift ν A2) M = ( ν SMS + ν FS ) AA2 /(A

32 Modified shifts for isotope pairs (King plot) 5d 6p transition P. Grundevik et al., Z. Phys. A 32, (983). 6s 6p transition Different slope with odd isotopes Result of core polarisation

33 Th 7340 yrs kbcl 229 Th source α Ra 5 days 225 Ac 0 days 225 β α Fr, At, Bi ~ 4 hours ion pump ion pump gate valve Ra/s Offline Setup of 225Ra for Spectroscopy

34 Offline Atomic Beam of 225Radium Ra 40.0 kev 225 Th 229 α decay y 4.9 d Inside oven 3.6*05 Bcl Fr 28. kev Ra 04 /s/cm2 22 Bi kev 23

35 Summary Radium is attractive Laser cooling strategy, go for it Barium MOT capture velocity 30m/s, 30G/cm number of atoms in the trap ~ capture efficiency ~ 0.5% of full velocity distribution life time of the MOT ~.5 s, depends on laser intensity temperature of the cloud 3() mk Lifetime and decay Isotope shifts of 5d6s 3D,2 6s6p P transition strong core polarization effects

36 Trapped Radioactive Isotopes: µ icro laboratories for Fundamental Physics TRIµ P Group kev MeV nev Q D D Thermal Ioniser Q Q Q D Barium Trapping D Q Q Magnetic separator S. De U. Dammalapati J. v.d. Berg T. Middelmann K. Jungmann LW Production target Q Q AGOR RFQ cooler/buncher MOT MOT G.P. Berg, J. v.d. Berg, U. Dammalapati, S. De, P.G. Dendooven, O Dermois, G. Giri, R. Hoekstra, D.J. v.d. Hook, K. Jungmann, W. Kruithof, T. Middelmann, A. Mol, R. Morgenstern, G. Onderwater, A. Rogachevskiy, M. Sohani, M. Stokroos, M. da Silva, R Timmermans, E. Traykov, O.O. Versolato, L. Wansbek, U. Wegener, L Willmann and H W Wilschut Radium Spectroscopy 229 Th 7340 y α decay 225 Ra 4.9 d S. De A. Mol K. Jungmann LW