The detection of the free precession of co‐located 3He/129Xe nuclear spins (clock comparison) is used as ultra‐sensitive probe for non‐magnetic spin interactions, since the magnetic dipole ...interaction (Zeeman‐term) drops out in the weighted frequency difference, i.e., Δω = ωHe‐ γHe/γXe·ωXe of the respective Larmor frequencies. Recent results are reported on searches for (i) short‐range P‐ and T‐violating interactions between nucleons, and (ii) Lorentz violating signatures by monitoring the Larmor frequencies as the laboratory reference frame rotates with respect to distant stars (sidereal modulation). Finally, a new experimental initiative to search for an electric dipole moment of 129Xe (CP‐violation) is discussed, which strongly benefits from the long spin‐coherence times obtained, reaching T2,He*> 100 h and T2,Xe*> 8 h in case of 3He and 129Xe, respectively.
The detection of the free precession of co‐located 3He/129Xe nuclear spins (clock comparison) is used as ultra‐sensitive probe for non‐magnetic spin interactions, since the magnetic dipole interaction (Zeeman‐term) drops out in the weighted frequency difference, i.e., Δω = ωHe‐ γHe/γXe·ωXe of the respective Larmor frequencies. Recent results are reported on searches for (i) short‐range P‐ and T‐violating interactions between nucleons, and (ii) Lorentz violating signatures by monitoring the Larmor frequencies as the laboratory reference frame rotates with respect to distant stars (sidereal modulation). Finally, a new experimental initiative to search for an electric dipole moment of 129Xe (CP‐violation) is discussed, which strongly benefits from the long spin‐coherence times obtained, reaching T*2,He> 100 h and T*2,Xe> 8 h in case of 3He and 129Xe, respectively.
Detection of magnetic fields generated by deep brain stimulation (DBS) using optically pumped magnetometers (OPMs) operating in the spin-exchange relaxation-free (SERF) regime holds significant ...promise. High bandwidth DBS signals are particularly valuable for understanding current OPM limitations and developing predictive strategies to overcome them. This primary study investigates the response of commercially available SERF-OPMs (QZFM Gen-2, QuSpin Inc.) with their limited 135 Hz bandwidth and open-loop operation when exposed to magnetic DBS signals emitted by a commercially available DBS lead and generated by a DBS implantable pulse generator (IPG), which are characterized by short-duration rectangular pulses. Such magnetic fields emitted from a real DBS lead were measured using OPMs across a range of DBS pulse repetition frequencies from 2 to 255 Hz. A versatile 304-channel superconducting quantum interference device (SQUID) vector magnetometer system was employed in the Berlin Magnetically Shielded Room-2.1 for reference measurements. Our findings identified peaks at several spectral frequencies in addition to those relevant to the DBS signal, including the known DBS repetition frequency and its spectral harmonics peaks. These additional peaks are attributed to the interaction between the lock-in detection-based OPM's 923 Hz modulating field, supplied by the OPM's on-sensor coils, and the DBS repetition frequency. These peaks were successfully reconstructed by developing an OPM lock-in model and applying this model to signal characteristics provided by SQUID reference measurements. This letter identifies and clarifies the origin of various spectral peaks observed when using bandlimited OPMs for high bandwidth signal detection. This understanding allows magnetometer users of this particular sensor technology to differentiate between artificially introduced signal components and the DBS signal components. These findings are essential for improving the application utility of OPM-based detection for DBS and contribute to the advancement and understanding of OPM technology and address its current limitations.
Very low residual magnetic field and field gradients are essential for a number of high resolution fundamental physical experiments and for further improvement of very sensitive magnetic measurement ...devices. The scope ranges from spin precession experiments, e.g. with 3He or neutrons, to biomagnetic measurements, like magnetoencephalograms, and to low field MR spectroscopy. One method of reducing environmental magnetic noise is to use a magnetically shielded room (MSR). Here, measures are demonstrated to improve residual field and field gradient inside a common MSR by a factor of more than 10 by a specific degaussing procedure, material selection of prefabricated parts and active shielding. The process is independent of the shielding factor and works also properly for heavily shielded rooms.
A co-located 3He and 129Xe nuclear spin free precession measurement at sub-μT magnetic field was carried out in a magnetically shielded environment. The uncorrected quotient of the gyromagnetic ...ratios between neutral 3He and 129Xe atoms is determined to be 2.754 082 81(07), accounting for only statistical error. Our measurement shows that this ratio has a stability of 1.4×10-5 √τ, demonstrating the ability to reach the current precision limit of the quotient in a 10000 s of averaging time τ. This precision is enough for the next-generation EDM search in neutral 129Xe atoms based on a similar comagnetometer scheme.
We report on the search for a new spin-dependent P- and T-violating interaction between nucleons mediated by light, pseudoscalar bosons such as the axion which was invented to solve the strong CP ...problem. Our experimental approach is to use an ultra-sensitive low-field magnetometer based on the detection of free precession of co-located 3He and 129Xe nuclear spins using SQUIDs as low-noise magnetic flux detectors. In the presence of an unpolarized mass the precession frequency shif
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