We use a paramagnetic salt TbF 3 with a dc SQUID to search for a possible axionlike s ? r interaction of a rotating copper mass with the salt. We set new limits on the axion coupling constant g s g p ͞hc and the finite-range Leitner -Okubo -Hari Dass coupling constant A. Our limit for range l at 30 mm is 2 orders of magnitude better than previous results. For l . 30 mm, g s g p ͞hc is ͑0.14 6 0.67͒ 3 10 228 , and A is less than 10. The outlook for further improvement is discussed.[S0031-9007(99)08656-1] PACS numbers: 14.80.Mz, 04.80.Cc, 12.20.Fv, 13.10. + q There are a number of groups experimentally searching for spin-dependent (semi-)long-range forces. These works are largely motivated to explore the role of spin in gravitation, and to explore the interaction associated with the exchange of a light or massless pseudoscalar Goldstone boson or similar interactions, e.g., arion interaction or axion interaction. Among the works to search for the spin-dependent (semi-)long-range forces, we can classify them into two categories: those searching for the monopole-dipole interactions [1-9] and those searching for the dipole-dipole interactions [5,[10][11][12][13][14][15][16][17].In connection with P (parity), and T (time reversal) noninvariance, Leitner and Okubo [18], and Hari Dass [19] suggested some time ago the following type of spingravity interaction, H int f͑r͒r ? s , (1) wherer is the unit vector from the massive body to the particle with spinhs . They assumed f͑r͒ 2AUm with U the gravitational potential of the massive body.Fujii [20] proposed finite-range mass-mass interactions. More recently, Fischbach et al. proposed a fifth force which violates the equivalence principle with finite-range monopole-monopole interactions and stimulated many experimental efforts [21].In our previous investigation [6], we used torsion balance with two cylindrical copper test masses and two cylindrical polarized "attracting" Dy 6 Fe 23 masses to search for finite-range mass-spin interactions with the Hamiltonian of the form (1). Our preliminary result showed that for the range of 3-5 cm, the upper limit of this interaction for our test mass and the Dy 6 Fe 23 polarized mass were below 1% of their gravitational interaction. We considered, in particular, the case of f͑r͒ 2Au 2mr mU with U the gravitational potential of the unpolarized body; that is, the finite-range mass-spin interaction is of the following form:H int 2Ae 2mr mUr ? s .(2) Ritter et al. [8], in a recent experiment, used spinpolarized Dy 6 Fe 23 masses acting on unpolarized copper masses in a dynamic-mode torsion pendulum and searched for the interaction of the axion [22][23][24] form,(3) In (3), l is the range of the interaction, g s and g p are the coupling constants of vertices at the polarized and unpolarized particles, and m is the mass of the polarized particle. Constraints on the coupling g s g p ͞hc with respect to the range are plotted in a logarithmic plot (Fig. 1). For l , 0.3 m, Refs. [6] and [8] give more stringent constraints than Refs. [5] and [7], a...

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This paper introduces a force measurement system recently established at the Center for Measurement Standards, Industrial Technology Research Institute for calibrating forces in a micronewton range with a resolution of a few nanonewtons. The force balance consists of a monolithic flexure stage and a specially made capacitor for electrostatic sensing and actuating. The capacitor is formed by three electrodes which can be utilized as a capacitive position sensor and an electrostatic force actuator at the same time. Force balance control is implemented with a digital controller by which the signal of the stage deflection is acquired, filtered and fed back to the electrostatic force driver to bring the flexure stage to the null position. The detailed description of the apparatus including the design of a monolithic flexure stage, principle of capacitive position sensing/electrostatic actuation and the force balance control is given in the paper. Finally, we present the results of electrostatic force calibration and the weighing of a 1 mg wire weight.

For strong fields, quantum electrodynamics tells us that the vacuum is refractive. This can be described by Euler-Heisenberg effective Lagrangian and for B ~ 12 T , the effective index deviates from one of the order of 10-21. Schemes to measure this effect are proposed using ultra-high sensitive interferometers of the type developed for gravity-wave detection. A double modulation scheme is promising in measuring the effect to 1%. For E ~ 5 × 107 V/m and B ~ 12 T , the mixed electric-magnetic effect is also within the reach of detectability.

Dark matter is a focused issue in galactic evolution and cosmology. Axion is a viable particle candidate for dark matter. Its interaction with photon is an effective way to detect it, e.g., pseudoscalar-photon interaction will generate vacuum dichroism in a magnetic field. Motivated to measure the QED vacuum birefringence and to detect pseudoscalar-photon interaction, we started to build up the Q & A experiment (QED [Quantum Electrodynamics] and Axion experiment) in 1994. In this talk, we first give a brief historical account of planet hunting and dark matter evidence. We then review our 3.5 m Fabry-Perot interferometer together with our results of measuring vacuum dichroism and gaseous Cotton-Mouton effects. Our first results give (-0.2 ± 2.8) × 10-13 rad/pass, at 2.3 T with 18,700 passes through a 0.6 m long magnet, for vacuum dichroism measurement. We are upgrading our interferometer to 7 m arm-length with a new 1.8 m 2.3 T permanent magnet capable of rotation up to 13 cycles per second. We aim at [Formula: see text] optical sensitivity with 532 nm cavity finesse around 100,000. When achieved, vacuum dichroism would be measured to 8.6 × 10-17 rad/pass in about 50 days, and QED birefringence would be measured to 28%.

We use a paramagnetic salt TbF3 with a DC SQUID to search for a possible anomalous spin-spin interaction of two rotating HoFe3 polarized bodies with the TbF3 paramagnetic salt. We set limits on the electron-electron spin interaction and the electron-nucleus spin interaction. In terms of a standard dipole-dipole form, the limits are (−2.1 ±3.5)×10−14 for the anomalous spin-spin interaction of electrons in terms of the interaction strength between the magnetic moments of the electrons, and (−2.1±3.6)×10−8 for the anomalous spin-spin interaction between the electron and the Ho-nucleus in terms of the interaction strength between the magnetic moments of the electron and the Ho-nucleus.

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We report the measurement of the spring constant of a cantilever using an electrostatic sensing and actuating force measurement system. The force measurement system consists of three main parts: a monolithic flexure stage, a three-electrode capacitor, and a digital controller. The most important feature of the system is the utilization of the three-electrode capacitor simultaneously as a position sensor and an electrostatic force generator. This allows us to constantly adjust and maintain gap distances between three electrodes, which is critical for this design to generate precise electrostatic compensation force. The force measurement system was partly upgraded and its performance was improved. The uncertainty estimation for the upgraded force measurement system is given. By measuring the spring constant of a commercially available cantilever force sensor, we demonstrate that the force measurement system is capable of calibrating the cantilever spring constant. The spring constant of the cantilever force sensor was measured to be (2227 ± 63) mN m−1 (coverage factor k = 2), corresponding to a relative expanded uncertainty of 2.8%.