Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 51 (2018)

Development of co-located 129 Xe and 131 Xe nuclear spin masers
with external feedback scheme†
T. Sato,∗1,∗2 Y. Ichikawa,∗1,∗2 S. Kojima,∗2 C. Funayama,∗2 S. Tanaka,∗2 T. Inoue,∗3,∗4,∗1 A. Uchiyama,∗4,∗1A. Gladkov,∗1,∗5 A. Takamine,∗1 Y. Sakamoto,∗2 Y. Ohtomo,∗2 C. Hirao,∗2 M. Chikamori,∗2 E. Hikota,∗2T. Suzuki,∗2 M. Tsuchiya,∗2 T. Furukawa,∗6 A. Yoshimi,∗7,∗1 C. P. Bidinosti,∗8 T. Ino,∗9 H. Ueno,∗1Y. Matsuo,∗10,∗1 T. Fukuyama,∗11 N. Yoshinaga,∗12 Y. Sakemi,∗13,∗4 and K. Asahi∗1,∗2Precision measurement of the frequency of a nuclear
spin is important in fundamental physics experiments
such as searches for an electric dipole moment. To
achieve high precision, we have developed a nuclear
spin maser with an external feedback framework,1–3)
which enables us to extend the spin precession far beyond the transverse relaxation time. In our previous
works on 129 Xe, the frequency precision was found tobe limited by the changes in the environmental magnetic ﬁeld and the eﬀective magnetic ﬁeld due to theFermi contact interaction between a Xe atom and a
Rb atom. In order to eliminate the sources of uncertainty, we newly introduced a 131 Xe maser as a comagnetometer for the 129 Xe experiment. In addition
to the frequency drift caused by the change in environmental ﬁelds, the system of 129 Xe and 131 Xe colocated in a common cell can eliminate the frequency
instability that stems from the change in the eﬀective
magnetic ﬁeld, because the interaction strengths between 129 Xe-Rb and 131 Xe-Rb4) are almost the same.
Thus, comagnetometry using 131 Xe may provide more
eﬃcient cancellation of uncertainties for the 129 Xe experiments, as compared to that using 3 He, which has
been widely used in this ﬁeld. The shortened measurement time due to quadrupole relaxation, which is oneof the diﬃculties for the 131 Xe comagnetometer, canbe overcome by introducing the maser scheme.
In order to investigate the long-term stability of themasers, frequency responses (i.e., susceptibilities) tooperational parameters of the experiment (magneticﬁeld, cell temperature, power and frequency of laserlights) were measured. By combining the obtained
susceptibilities and the measured instabilities of theindividual parameters, the maser frequency instabilities caused by the parameters were evaluated. Fig†

Condensed from the article in Phys. Lett. A 382, 588–594(2018)∗1 RIKEN Nishina Center∗2 Department of Physics, Tokyo Institute of Technology∗3 FRIS, Tohoku University∗4 CYRIC, Tohoku University∗5 Department of Physics, Kyungpook National University∗6 Department of Physics, Tokyo Metropolitan University∗7 RIIS, Okayama University∗8 Department of Physics, University of Winnipeg∗9 Institute of Material Structure Science, KEK∗10 Department of Advanced Sciences, Hosei University∗11 RCNP, Osaka University∗12 Department of Physics, Saitama University∗13 CNS, University of Tokyo- 180 -ure 1 shows the standard deviation of the maser frequency evaluated from the drifts in the cell temperature (which leads to change in the Rb number density,and hence change in the eﬀective magnetic ﬁeld) andenvironmental magnetic ﬁelds as a function of the averaging time. It was found that frequency drifts dueto the magnetic eﬀects on 129 Xe were reduced by twoorders of magnitude by applying the appropriate correction based on the measured 131 Xe spin precession
frequency. This result indicates the eﬃcient performance of the proposed comagnetometry using 131 Xe
co-located with 129 Xe. Because of the enhanced stability of masers, the frequency drifts at a level of µHz
associated with the drifts in the power of the laser
lights were also revealed. Experimental investigationof the origin of this instability and its reduction aresubjects of our ongoing work.

Fig. 1. Long-term stability of masers and the evaluatedcontribution from the instabilities of magnetic eﬀects.
Closed symbols represent the evaluated contributions
from the frequency instabilities due to magnetic effects for frequency of masers. Hatched band represents
the error associated with the evaluated standard deviation of maser frequency σν . Open symbols represent
the measured standard deviations of the frequency ofmasers.

References
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2) A. Yoshimi et al., Phys. Lett. A 376, 1924 (2012).
3) T. Inoue et al., Eur. Phys. J. D 70, 129 (2016).
4) M. Bulatowicz et al., Phys. Rev. Lett. 111, 102001(2013).