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129Xe magnetometryfor KEK-RCNP neutron EDM measurementsM. Mihara, K. Matsuta (Osaka Univ.)Y. Masuda, S.C. Jeong, Y.X. Watanabe, S. Kawasaki (KEK)K. Hatanaka, R. Matsumiya (RCNP, Osaka Univ.)K. Asahi (TIT)C. Bidnosti (Winipeg Univ.)Y. Shin (TRIUMF)Workshop on nEDM Experimental Tecniques, Oct. 11-13, 2012, ORNL

nEDM measurements with 129Xe comagnetometern129XeEDM cellBE+En = (2nB 2dnE)/hXe= (2XeB 2dXeE)/h(n/Xe)E+(n/Xe)E 1 + 41hXenXedmeasEdn dXeXen~1028 ecm~1011B = 1TE = 10 kV/cm= ~29 Hz= ~12 Hz~0.5 nHz+(0.73.3)x1027 ecmRosemberry & ChuppPRL86(2001)22GPE for 129XeBuffer gas effect suppresses GPE129Xe mean free path (= 1/n) = 0.7~5 mm@2.5 x 1014 /cc (7 mTorr)

GPE for 129XeSuppression factor S = (Td/TL)2 = 6 x 104df (B0z/z)R2/c2 SdfXe = ~0.9 x 1028 ecmB0 = 2 TB0z/z = 2 nT/mR = 0.25 mvxy = 240 m/s@300K = 0.7 mmdiffusion time Td = (2R)2/(vxy) ~1.5 sLarmor precession time TL = 2/0 ~40 mscf. dfHg = ~5 x 1026 ecmPLA376(2012)1347

129Xe polarization system of Asahi (TIT) group. We will apply a part of this apparatus to co-magnetometry in nEDM.

Xe FID signalDetection system will be replaced by SQUID or SERF or NMORT1 = 1000 s, T2 = 350 s50%Polarize 129Xe in EDM cellRb-Xe [129Xe] = ~2.5 x 1014 cm3T1, T2 > ~100 sN2 free

Measure 129Xe precessionSQUIDprobe laserPolarize 129Xe nuclear spinOptical pumping

van der Waals molecule9

Effect of N2 buffer gasRosenberry et al., PRA75(2007)023401N2N2Buffer gas N2: reduce absorption of de-exciting unpolarized photons

Ruth et al., Appl. Phys. B 68 (1999) 93Xe + N2 + RbN2Plarization of Rb atomsPolarization of 129Xe nucleiPlan of 129Xe magnetometerNo buffer gas (N2) in EDM cellpump laserprobe laserVUCN guideEDM cell (Xe: 7 mTorr)detectorB129Xe & Rb

External cell: EDM cellXe: 7 mTorr (2.5 x 1014 cm-3)Total amount of Xe gas: 20 liter (EDM cell + UCN guide)External cell: 7 Torr / 20 cm3T2 > ~100 spolarize 129Xe11Freeze-pump-thaw separationLN2probelaserpump laserXeN2pump Xe + N2 mixture in polarizing cell Solidify Xe Evacuate N2 gas Transport polarized 129Xe into EDM cellXe, N2RbN2 freeAppl. Phys. B 68 (1999) 9312Appl. Phys. B 68 (1999) 93

Rb-K mixture 21Ne polarization x 10pump laserprobe laser

129Xe nuclear spin relaxation in EDM cell1/T2 = 1/T1 + 1/T2,field R4/D x |B|2~10 pT/cm p11/T1 = 1/T1,Xe-Rb + 1/T1,Xe-Xe + 1/T1,wall1/T1,Xe-Rb = (M/[Xe] + ) [Rb] s1vdW ~1011collision ~1016= ~1/(10 s) (T = 300 K)[Cates et al., PRA45(1992)4631]1/T1,Xe-Xe = 1/(4.1 h)[Chann et al., PRL88(2002)113201]1/T1,wall = 1/(3 h)~ 1/(several h)[Xe] = 2.5 x 1014 cm3 (7 mTorr)[Rb] = 1 x 1010 cm3 (T = 300 K)[Gemmel et al., EPJ D57(2010)303]Measurement of PXe, T1

AFP-NMRB0B1Pickup coilRFcoilB0 coilcell

Proton NMR (H2O)Lock-in amp. outB0 5 sL(proton) = 48 kHz@11.2 G

Rb & Xe transfer systemTi-sapphire & Ar laserSemiconductor laser

summaryGPE for 129Xe comagnetometer was discussed.Buffer gas effect suppresses GPE to dfxe ~1028 ecm.How to realize the 129Xe comagnetomter is under consideration. But, N2 free 129Xe polarization may be possible. R & D has been just started. Precision measurements of NMR frequency ratio n/Xe are planed to determine g factor of 129Xe and field gradient. Spin exchange rate in exernal cell[Xe] = 2.5 x 1017 cm3 (7 Torr), [N2] = 3.5 x 1018 cm3 (100 Torr)[Rb] = 3 x 1013 cm3 (T = 400 K)PXe(t) = PRb (1 + /se)1 x exp{( + se)t}PRb(t) = (1 + sd/+)1 x exp{(sd + +)t}sd; spin destruction rate of Rb atom+; production rate of mJ = +1/2; wall relaxation & Xe-Xe vdWse; Rb-Xe spin exchange rate()()sd = Xe-Rb[Xe] + Rb-Rb[Rb] + N2-Rb[N2] = 1.2 x 103 s111002433se = Xe-Rb[Rb] = 0.13 s1[Wagshul & Chupp, RRA49(1994)3854][Cates et al., PRA45(1992)4631]

Polarize 129Xe nuclear spinOptical pumpingmJ = 1/2mJ = +1/2+5S1/25P1/2 794.7 nmEnergy levels of Rb atom = 794.7 nmRb129Xe+PXe PRb (1 + /se)1PRb (1 + sd/+)1sd; spin destruction rate of Rb atom+; production rate of mJ = +1/2; 129Xe relaxation rate except sese; Rb-Xe spin exchange rate()()29129Xe magnetometerPolarize 129Xe before storing UCN129Xe129XeBBMeasure Xe during Ramsey resonance90 pulseT2 > tc

T1 >> tc

30

KEK

, (T1, T2)

Our approach to nEDMB 129Xe magnetization= 0/4 (3r(r) - r2)/r5= 0.9810-14 T at r = 0.1 m 2.51016/liter 129Xe = -3.923910-27 J/TS = 0.01 m2 = 0.047 0 cos(0t) 0 = h/2e = 2.06783366710-15 Tm2We need to developSQUID 1fT, 50/Hzvibration?SERF Cs magnetometervibration small effectBoObservation of 129Xe spin precession in the EDM cellEDM cellWe have experience of Xe polarization by means of spin exchange optical pumping. SQUID or SERF or NMORIf 50% polarization,p =7x 10-3 Torr, V =3 litters, B = 150 fT

PRA75(2007)023401: Xe: 7 mTorr (2.5 x 1014 cm-3)Diffusion time: td = (2R)2/(vxy)R = 0.25 mvxy = 158 m/s = 0.5 mm= ~3 sNo buffer gas PXe ?pump laserprobe laser36Appl. Phys. B 68 (1999) 93

Appl. Phys. B 68 (1999) 93