Magnetoencephalography with an atomic magnetometer

Xia, Hui; Baranga, A. Ben‐Amar; Hoffman, Dan; Romalis, Michael

doi:10.1063/1.2392722

Cited by 402 publications

(253 citation statements)

References 15 publications

Supporting

Mentioning

239

Contrasting

Unclassified

Order By: Relevance

“…While the potential of OPMs for magnetoencephalography has been demonstrated before [33], the small size and fiber-coupled nature of μOPMs will allow more flexibility in sensor placement and density. This makes them ideally suited for imaging of all kinds of magnetic field sources, including other biomedical applications and nonmedical applications such as buried anomaly detection.…”

Section: Discussionmentioning

confidence: 99%

Magnetic field imaging with microfabricated optically-pumped magnetometers

et al. 2017

View full text Add to dashboard Cite

A multichannel imaging system is presented, consisting of 25 microfabricated optically-pumped magnetometers. The sensor probes have a footprint of less than 1 cm 2 and a sensitive volume of 1.5 mm × 1.5 mm × 1.5 mm and connect to a control unit through optical fibers of length 5 m. Operating at very low ambient magnetic fields, the sensor array has an average magnetic sensitivity of 24 fT/Hz 1/2 , with a standard deviation of 5 fT/Hz 1/2 when the noise of each sensor is averaged between 10 and 50 Hz. Operating in Earth's magnetic field, the magnetometers have a field sensitivity around 5 pT/Hz 1/2 . The vacuum-packaged sensor heads are optically heated and consume on average 76 ± 7 mW of power each. The heating power is provided by an array of eight diode lasers. Magnetic field imaging of small probe coils was obtained with the sensor array and fits to the expected field pattern agree well with the measured data. 19887-19894 (2014). 24. S. J. Seltzer and M. V. Romalis, "Unshielded three-axis vector operation of a spin-exchange-relaxation-free atomic magnetometer," Appl.

show abstract

Section: Discussionmentioning

confidence: 99%

Magnetic field imaging with microfabricated optically-pumped magnetometers

et al. 2017

View full text Add to dashboard Cite

show abstract

“…Cardiomagnetic fields are recorded sequentially on a grid of points above human chest. Measurements of the brain magnetic field have been performed with a potassium SERF magnetometer which operates at the vapor cell temperature of 180 • C and uses a multi-channel photodetector to simultaneously record the spatial distribution of the magnetic fields [64]. Even though heating is required to maintain the operating temperature of the cell positioned close to the subject's head, it is technically easier and cheaper to do than maintaining cryogenic temperature at the sensor, as required in the case of SQUIDs.…”

Section: Applications a Biological Magnetic Fieldsmentioning

confidence: 99%

Optical magnetometry

2007

View full text Add to dashboard Cite

Some of the most sensitive methods of measuring magnetic fields utilize interactions of resonant light with atomic vapor. Recent developments in this vibrant field are improving magnetometers in many traditional areas such as measurement of geomagnetic anomalies and magnetic fields in space, and are opening the door to new ones, including, dynamical measurements of bio-magnetic fields, detection of nuclear magnetic resonance (NMR), magnetic-resonance imaging (MRI), inertialrotation sensing, magnetic microscopy with cold atoms, and tests of fundamental symmetries of Nature.

show abstract

“…We also developed a quantitative method for analyzing the effect of diffusion on quantum spin noise using spin timecorrelation function. By relying on precision timing measurements with very wide dynamic range and fractional field sensitivity of 7 × 10 −11 /Hz 1/2 this magnetometer opens the possibility of fundamentally new applications, for example unshielded detection of magnetoencephalography signals [27]. The sensitivity per unit volume can be further improved in this system by reducing the decay of the spin time-correlation function due to atomic diffusion, which will allow suppression of ASN due to spinsqueezing between two probe pulses.…”

mentioning

confidence: 99%

Subfemtotesla Scalar Atomic Magnetometry Using Multipass Cells

et al. 2013

Self Cite

View full text Add to dashboard Cite

Scalar atomic magnetometers have many attractive features but their sensitivity has been relatively poor. We describe a Rb scalar gradiometer using two multi-pass optical cells. We use a pump-probe measurement scheme to suppress spin-exchange relaxation and two probe pulses to find the spin precession zero crossing times with a resolution of 1 psec. We realize magnetic field sensitivity of 0.54 fT/Hz 1/2 , which improves by an order of magnitude the best scalar magnetometer sensitivity and surpasses the quantum limit set by spin-exchange collisions for a scalar magnetometer with the same measurement volume operating in a continuous regime. PACS numbers: 07.55.Ge, 42.50.Lc, 32.30.Dx Alkali-metal magnetometers can surpass SQUIDs as the most sensitive detectors of magnetic field, reaching sensitivity below 1 fT/Hz 1/2 [1, 2], but only if they are operated near zero magnetic field to eliminate spin relaxation due to spin-exchange collisions [3,4]. Many magnetometer applications, such as searches for permanent electric dipole moments [5], detection of NMR signals [6], and low-field magnetic resonance imaging [7], require sensitive magnetic measurements in a finite magnetic field. In addition, scalar magnetometers measuring the Zeeman frequency are unique among magnetic sensors in being insensitive to the direction of the field, making them particularly suitable for geomagnetic mapping [8] and field measurements in space [9,10]. The sensitivity of scalar magnetometers has been relatively poor, as summarized recently in [11]. The best directly measured scalar magnetometer sensitivity is equal 7 fT/Hz 1/2 with a measurement volume of 1.5 cm 3 [12], while estimates of fundamental sensitivity per unit measurement volume for various types of scalar alkali-metal magnetometers range from several fT cm 3/2 /Hz 1/2 [13, 14] to about 1 fT cm 3/2 /Hz 1/2 [12]. Here we describe a new type of scalar atomic magnetometer using multi-pass vapor cells [15,16] and operating in a pulsed pump-probe mode [17] to achieve magnetic field sensitivity of 0.54 fT/Hz 1/2 with a measurement volume of 0.66 cm 3 in each multi-pass cell. The magnetometer sensitivity approaches, for the first time, the fundamental limit set by Rb-Rb collisions. We also develop here a quantitative method to analyze significant effects of atomic diffusion on the spectrum of the spin-projection noise in vapor cells with buffer gas using a spin time-correlation function.The sensitivity of an atomic magnetometer, as any other frequency measurement, is fundamentally limited by spin projection noise and spin relaxation [18]. For N spin-1/2 atoms with coherence time T 2 the sensitivity after a long measurement time t ≫ T 2 is given by δB = 2e/N T 2 t/γ, where γ is the gyromagnetic ratio. Spin squeezing techniques can reduce this uncertainty by a factor of √ e, but do not change the scaling with N [18-20]. The number of atoms can be increased until collisions between them start to limit T 2 . Writing T −1 2 = nσv, where n is the density of atoms, σ is the spin relaxation c...

show abstract

Magnetoencephalography with an atomic magnetometer

Cited by 402 publications

References 15 publications

Magnetic field imaging with microfabricated optically-pumped magnetometers

Magnetic field imaging with microfabricated optically-pumped magnetometers

Optical magnetometry

Subfemtotesla Scalar Atomic Magnetometry Using Multipass Cells

Contact Info

Product

Resources

About