EDM photo detector Outline: Rb vapor - PowerPoint PPT Presentation

冷却フランシウム原子を用いた 電子 EDM 探索のためのルビジウム磁力計の開発 photo detector Outline: Rb vapor cell 1. Motivation 2. Nonlinear magneto-optical Rotation (NMOR) effect coil 3. Frequency modulated (FM) NMOR μ – metal shield 4. FM-NMOR spectroscopy for a sensitive magnetometry laser light 5. Summary 東北大学 サイクロトロン RI センター (CYRIC) 内山愛子

Motivation to study the Rb Magnetometer -> search for electron permanent electric dipole moment ( e -EDM ) If an elementary particles has the finite size of the permanent electric dipole moment ( EDM ) (d) along its spin direction, T and P are violated. μ P T B E B E E B d           H B d E Experimental upper limit : μ : magnetic dipole moment | d e |< 8.7 × 10 -29 e cm d : electric dipole moment The ACME Collaboration et al., Science 343 , 269 (2014) Standard model (SM) Beyond the Standard model 10 -20 10 -25 10 -30 10 -35 10 -40 d e [ e cm] -> EDM can be a probe to test the physics beyond the SM 11. Feb. 2015 ICEPP Symposium 21st 2

How to search for the e -EDM? -> measurement of the energy shifts of atom Francium has large enhancement factor R Fr ~895 and Fr  d R d can be cooled and trapped by using laser light. Fr e B ≠ 0 E ≠ 0 B=0 B ≠ 0 E=0 E=0 hν - hν + Zeeman effect          h 2 B d E   d Fr ~10 -26 e cm in E = 100 kV/cm E d  B  Earth’s magnetic requires the sensitivity of δB ~0.1 fT  field~50 μT -> precision measurement of magnetic field should be performed and fluctuation of magnetic field should be suppressed. 11. Feb. 2015 ICEPP Symposium 21st 3

How to measure the magnetic field? ->using the frequency modulated nonlinear magneto-optical rotation ( FM-NMOR ) effect 1. The linearly polarized light produces an alignment state of Rb atoms. 2. The atomic alignment precesses Rb in the magnetic field. Linearly polarized light 3. The polarization plane of the light rotates due to an interaction Magnetic field B z with the atomic alignment. D. Budker et al ., Rev. Mod. Phys. 74, 1153 (2002) Rotation angle:  2 g B F B Z  l     2   l 2 g B    0 F B Z 1     g F : Landé g-factor, µ B : Bohr magneton l : length of the cell, l 0 : absorption length 11. Feb. 2015 ICEPP Symposium 21st 4

How to measure the magnetic field? ->using the frequency modulated nonlinear magneto-optical rotation ( FM-NMOR ) effect 1. The linearly polarized light produces an alignment state of Rb atoms. 2. The atomic alignment precesses Rb in the magnetic field. Linearly polarized light 3. The polarization plane of the light rotates due to an interaction Magnetic field B z with the atomic alignment. D. Budker et al ., Rev. Mod. Phys. 74, 1153 (2002) Rotation angle:  2 g B F B Z  l     2   l 2 g B    0 F B Z 1     g F : Landé g-factor, µ B : Bohr magneton l : length of the cell, l 0 : absorption length 11. Feb. 2015 ICEPP Symposium 21st 5

How to measure the magnetic field? ->using the frequency modulated nonlinear magneto-optical rotation ( FM-NMOR ) effect 1. The linearly polarized light produces an alignment state of Rb atoms. 2. The atomic alignment precesses Rb in the magnetic field. Linearly polarized light 3. The polarization plane of the light rotates due to an interaction Magnetic field B z with the atomic alignment. D. Budker et al ., Rev. Mod. Phys. 74, 1153 (2002) Rotation angle:  2 g B F B Z  l     2   l 2 g B    0 F B Z 1     g F : Landé g-factor, µ B : Bohr magneton l : length of the cell, l 0 : absorption length 11. Feb. 2015 ICEPP Symposium 21st 6

How to measure the magnetic field? ->using the frequency modulated nonlinear magneto-optical rotation ( FM-NMOR ) effect 1. The linearly polarized light produces an alignment state of Rb atoms. 2. The atomic alignment precesses Rb in the magnetic field. Linearly polarized light 3. The polarization plane of the light rotates due to an Magnetic field B z interaction with the atomic alignment. D. Budker et al ., Rev. Mod. Phys. 74, 1153 (2002) Rotation angle:  2 g B F B Z  l     2   l 2 g B    0 F B Z 1     g F : Landé g-factor, µ B : Bohr magneton l : length of the cell, l 0 : absorption length 11. Feb. 2015 ICEPP Symposium 21st 7

Frequency modulated NMOR (FM-NMOR) Modulated light enable to measure non-zero magnetic fields . • FM-NMOR spectrum Ω m =5 kHz    B = -1.08 μT n 2 ( ν Rb = 5 kHz) m L B = 0 μT Ω L : Lamor frequency ( ν Rb = 0 kHz) Ω m : modulation frequency  2 m g B   F F B B = -0.54 μT L B = +1.08 μT ( ν Rb = 2.5 kHz) h ( ν Rb = 5 kHz) Resonance frequency of B = +0.54 μT FM-NMOR ( ν Rb = 2.5 kHz) -> Lamor frequency -> Magnetic field Magnetic Field [ μT ] 11. Feb. 2015 ICEPP Symposium 21st 8

What should I do for the sensitive FM-NMOR magnetometer? -> find the best condition for the FM-NMOR       1   V       B ,      B B B large magnitude of slope = high sensitivity ΔB = ℏ Γ /g F μ B The best sensitivity is now 10 δB ~ 3 nT/ √ Hz 1 Noise [V/ √ Hz] 0.1 10 -2 ΔV=l 0 /l 10 -3 10 -4 10 -5 10 -6 50 200 250 0 100 150 frequency [Hz] g F : Landé g-factor, µ B : Bohr magneton l : length of the cell, l 0 : absorption length 11. Feb. 2015 ICEPP Symposium 21st 9

Experimental apparatus PBS λ/2 λ/2 PBS Photo detector 3-axis coil DFB Laser (Rb D1 line) Rb cell Saturated Frequency Magnetic shield absorption Modulation spectroscopy <- frequency monitor SYNC Lock-in Function amplifier generator DFB laser Magnetic shield 3-axis coil and Rb cell 11. Feb. 2015 ICEPP Symposium 21st 10

PBS λ/2 λ/2 PBS Photo detector 3-axis coil DFB Laser (Rb D1 line) Rb cell Saturated Frequency Magnetic shield absorption Modulation spectroscopy <- frequency monitor SYNC Lock-in Function amplifier generator DFB laser Magnetic shield 3-axis coil and Rb cell 11. Feb. 2015 ICEPP Symposium 21st 11

NMOR effect. PBS λ/2 λ/2 PBS Photo detector 3-axis coil DFB Laser (Rb D1 line) Rb cell Saturated Frequency Magnetic shield absorption Modulation spectroscopy <- frequency monitor SYNC Lock-in Function amplifier generator DFB laser Magnetic shield 3-axis coil and Rb cell 11. Feb. 2015 ICEPP Symposium 21st 12

NMOR effect. PBS λ/2 λ/2 PBS Photo detector 3-axis coil DFB Laser (Rb D1 line) Rb cell Saturated Frequency Magnetic shield absorption Modulation spectroscopy <- frequency monitor SYNC Lock-in Function amplifier generator DFB laser Magnetic shield 3-axis coil and Rb cell 11. Feb. 2015 ICEPP Symposium 21st 13

FM parameter dependence - long coherence time - large absorption = large alignment high sensitivity 25 25 20 20 slope (mV/ μT ) slope (mV/ μT ) 1 15 5 10 1 0 5 5 0 0 0 600 700 800 900 100 200 300 400 500 200 800 1000 1200 1400 1600 1800 400 600 laser power (µW) scan width (MHz) 11. Feb. 2015 ICEPP Symposium 21st 14

Cell dependence 25 2 3 slope (mV/ μT ) 20 15 1 10 5 Cell No. Cell size Coating Cleaning Buffer gas NMOR signal Best cell f 30 mm × L 30mm － ○ 1 Paraffin HNO 3 f 30 mm × L 30mm － ○ 0 2 Paraffin HF f 25mm × L 25 mm ○ 3 Paraffin ? He 1 torr f 20mm × L 20 mm － × 4 Paraffin HF f 25mm × L 25 mm － × 5 ? N 2 50 torr f 25mm × L 25 mm － － × 6 ? 11. Feb. 2015 ICEPP Symposium 21st 15

Summary The Rb atomic magnetometer based on the FM-NMOR effect was studied for the electron EDM search using the laser cooled Fr atoms. The dependences on the frequency scan width, the laser power, and the cell production procedure for the field sensitivity were measured. The best magnetic sensitivity is now 3 nT/ √ Hz at the present condition. 11. Feb. 2015 ICEPP Symposium 21st 16

Collaboration Cyclotron and Radioisotope Center (CYRIC), Tohoku University S. Ando, T. Aoki, H. Arikawa, K. Harada, T. Hayamizu, T. Inoue*, T. Ishikawa, M. Itoh, K. Kato, H. Kawamura*, K. Sakamoto, A. Uchiyama, and Y. Sakemi *Frontier Research Institute for Interdisciplinary Sciences (FRIS), Tohoku University The University of Tokyo Tokyo Inst. Tech Tokyo Metropolitan University Tokyo Univ. Agri. Tech. K. Asahi A. Hatakeyama T. Aoki T. Furukawa Japan Atomic Energy Agency Kyoto University Indian Tech. Roorkee Osaka University K. Imai T. Murakami H. S. Nataraj K. Hatanaka Tohoku University Osaka University Okayama University Tokyo Inst. Tech. Y. Shimizu H. P . Yoshida A. Yoshimi T. Sato Foreign students Kyushu University T. Wakasa J. Mathis (ENSICAEN), L. Koehler (TU Darmstadt) 11. Feb. 2015 ICEPP Symposium 21st 17