Development of high-sensitivity magnetometer for EDM experiment with 129 Xe spin oscillator

Transcription

1 Development of high-sensitivity magnetometer for EDM experiment with 129 Xe spin oscillator A. Yoshimi RIKEN Nishina Center ( ~ ) Okayama University ( ~ ) T. Nanao 1, T. Inoue 1, M. Chikamori 1, T. urukawa 2, Y. Ichikawa 3, H. Hayashi 1, M. Tsuchiya 1, H. Miyatake 1, Y. Ishii 1, N. Yoshida 1, H. Shirai 1, M. Uchida 1, H. Ueno 3, Y. Matsuo 3, T. ukuyama 4, and K. Asahi 1 1 Department of Physics, Tokyo Institute of Technology 2 Department of Physics, Tokyo Metropolitan University 3 Nishina center, RIKEN 4 Department of Physics, Ritsumeikan University

2 EDM measurement B 0 B 0 E 0 E // B E // B d e 4dE h cm ecm10 Vcm s 1nHz requency shift of 1 nhz evs B 1pG 0.1fT x z B +E + t y 2B 2dE h x B E z y t 2B 2dE h nhz Phase measurement: s 31years 2T 1mrad (0.06 ), T 1,000s 160nHz Repeating measurements : average i i 10month = 25,920 ksec: n total i 160 nhz n total i n 1 nhz

3 B env [mg] requency precision [Hz] Nuclear Spin Maser with Polarized 129 Xe at low field Singnal (V) Maser signal requency precision Time (s) nhz 0 d ~ 810 T 28 m 30,000 s ecm E 0 10 kv/cm Environmental field Time [s] 0.3 mg δb = μg inside the magnetic shield δb = ng Time [s] + field fluctuation due to change in the magnetic shield

4 Comagnetometer with 3 He - Michigan Univ. - Rosenberry and Chupp, PRL (2001) 129Xe precession : locked with reference oscillator B 0 3.0G No drift locked Xe 20nHz 2000 s - Run eedback to solenoid current B 17 pg Pump bulb T [Rb] P maser Rbmaser 120 C / cm 3 Measuring 3He maser frequency 2 μhz EDM signal Maser bulb Long term fluctuation μhz ng free He T maser 40 C [Rb] P Rbmaser / cm 3

5 requency stability in Dual noble gas spin maser Sources of frequency drift Drift of the applied magnetic field B 0 Magnetic field generated from polarized atoms Other species: Longitudinal (7mHz, 8.2 mhz) Transverse (58 phz, -81 phz) Same species: Longitudinal (23mHz, 2.5 mhz) Transverse (-18mHz, -5.5mHz) rom Rb atoms (40 nhz, 2μHz) B sol B ext B atoms B z Xe Maser Position : (30mHz) B T Cavity pulling: (20μHz) B B B Tatoms ield gradient (100nHz, 36nHz) B Tgrad Maser posi. Laser properties Temperature Environmental field Shield drift, noise Mechanical instability Cavity pul

6 Magnetometer for Low freq-spin maser EDM experiment (1) High sensitivity magnetometers (2) Rb comagnetometer (3) 3He comagnetometer Rb Xe Rb Xe Xe He Magnetometer probe Rb Magnetometer probe Maser probe Not comagnetometer Rb magnetometer near maser cell Only Xe and Rb (small, and not pol) B G/ Hz 100 s run ( if constant ): B G Comagnetometer of Rb Only Xe and Rb (small, and not pol) Probrem of Rb Xe interaction? ( Low density Xe gas? ) Polarizability problem B? G/ Hz Comagnetometer of 3He S/N for He precession for laser probing.

7 Precise magnetometer with Rb atoms using NMOR Resonant optical rotation in Rb vapor (NMOR; Nonlinear Magneto-Optical Rotation) (b) x B 12 ~ 10 G/ Hz Incident laser beam // ' y ( =0) s + s - m 1 m 0 1 (=1) m Transmitted laser z beam Atomic alignment G.S. 1 2 gb m m m g BBz 0 2g BB 1 0 m m 1 1 z 2 l 2l 0 B 1μG Narrow line width (reducing spin relaxation) Operation at room temperature Operation at geophysical field range (mg~g) (by using modulation of laser property)

8 NMOR setup Photo elastic Modulator (PEM) 4-layer magnetic shield Beam splitter Linear polarizer-2 Photo diode x y z 3-axis coil Linear Polarizer-1 External Cavity Diode Laser (20mW, WHM 1MHz) Rb cell Rb reference cell Wavemeter PEM driver&controller Lock-in amplifier Oscilloscope Photo diode 85Rb Reference(50kHz) Signal 87Rb 87Rb 15 GHz

9 Setup, Rb cell Rb cell with Paraffin coating: commercial paraffin mixture (Paraflint) (CH 2 )n φ mm ield coil (3-axis) ECDL

10 回転角度 (mrad) NMOR spectrum Wide-field scan B 0.44G Dispersive function 2gBBz / 2gBBz / 1 l 2 2l0 2 Transit effect s Laser light Magnetic field (G) Narrow-field scan Δt = s Preservation of atomic spin coherence at wall-collision Magnetic field B 2 mg Laser beam Magnetic field (mg) ms / 2-1 [s ]

11 NMOR width (Cell dependence and residual field) B 4.04mG B 1.99mG Residual magnetic field B B B x y z 235μG 237μG 13μG B B B x y z 84μG 4 μg 45μG Degaussing mG 0.57mG

12 Rotation angle (mrad) Magnetic sensitivity NMOR spectrum Noise spectrum (V) V V/ Hz B 0.37 mg B z Bz rad/g μrad/ Hz Magnetic field (mg) req. (Hz) B G / Hz 50 ng / Hz

13 Rotation angle (mrad) Rotation angle (mrad) The cell made by Prof. M.V. Balabas:φ60 mm, T1 2s. Thanks to Prof. Hatakeyama (Tokyo Univ. Agri. Tech.) Balabas cell Balabas cell B 0.37 mg B 0.28mG / ms / ms B z Bz rad/g B z Bz rad/g Magnetic field (mg) Magnetic field (mg) No large difference in NMOR width Wall performance does not limit the width residual field

14 Modulated NMOR - measurement at B 0 = 10 mg - NMOR : measurement around B=0[G] At higher magnetic field, optical rotation does not appear Low field: ω Rb < γ rel x High field: ω Rb > γ rel x ω Rb > γ rel Modulated NMOR y z y z Production of alignment ω mod = ½ x ω Rb t B requency modulated Amplitude modulated Pustelny et al. J.Appl.Phys. 103, (2008)

15 Setup - measurement at B 0 = 10 mg - Block for 0 th order light Amplitude modulation by using AOM:(Acousto-Optical Modulator) NMOR cell λ/2 GLP AOM On Off ref. cell PD wave monitor ECDL

16 NMOR Signal V] Spectrum - measurement at B 0 = 10 mg - Modulation frequency : 9 khz (AM) corresponds to twice the Larmor freq. at B0 = 9.645mG Magnetic field sweep: -11 mg +11 mg AM-NMOR B0 9.7 mg g B khz/g M-NMOR B0 9.7 mg Magnetic field [mg] Magnetic sensitivity (at present) B d db 1 B Slope =53.5V/mG 3 40 ng/ Hz δφ = 2mV/ Hz

17 Summary and uture High sensitive magnetometer is inevitable for atomic EDM experiments because main source of frequency stability comes from drifts of magnetic field ( applied B 0 or environmental field). We have developed the Rb NMOR spectrometer for the operation of magnetometer. Operation of modulated NMOR for measurements at B0 = 10 mg. Improving NMOR-magnetometer performance; Optimization of degaussing procedure, cancelling field (to << ΔB z ) Improving cell-coating procedure. Measurement of T1 for the Rb cells Noise studies; detection method, electronics, experimental room Introduction to spin maser setup