Noise analysis and cancellation for the underground application of magnetic resonance using a multi-component reference antenna – Case study from the rock laboratory of Mont Terri, Switzerland

On-site characterization of the spatio-temporal structure of the noise for MRS measurements using a pair of eight-shape loops

“…For sake of simplicity, we consider powerlines as infinite long straight wireline that are traversed by an alternating current ( ) ∑ ( ) composed of harmonics of a fundamental frequency (50 Hz in France) with an angular frequency . The fundamental frequency shows variations on the range of a few tens of mHz (Liu et al, 2018;Costabel, 2019, Kremer et al, 2019 which corresponds to a variation of a few Hz when regarding the higher harmonics in the MRS range. Note that generally all powerlines on the same grid have the same instantaneous frequency but various phases and amplitudes, and thus can hardly be distinguished from one another.…”

“…Nevertheless, its ease of implantation make it one of the most used design. More recently, other hardware have been introduced with promising efficiency (Díaz-Curiel et al, 2011;Davis et al, 2014;Behroozmand et al, 2016) and measurements of the three components of the magnetic field instead of only the vertical component have been explored (Radic, 2006(Radic, , 2009Costabel and Müller-Petke, 2014;Müller-Petke and Costabel, 2014;Girard et al, 2015;Kass et al, 2017;Costabel, 2019).…”

“…Hence, much research led to hardware and software development and the processing sequences are often combined in a workflow to successfully to enhance the signal-to-noise ratio (Behroozmand et al, 2015;Dalgaard and Auken, 2016;Ghanati et al, 2016;Müller-Petke et al, 2016;Hein et al, 2017, Liu et al 2018, 2019.…”

Feasibility study on prepolarized surface nuclear magnetic resonance for soil moisture measurements

“…For a suitable compensation , c) depict the 68% uncertainty intervals resulting from a mono-exponential fit of the data of the 3D noise field, we used a three-channel reference antenna, which was installed about 2 m next to the water basin (Figure 4b). According to Costabel (2019), this kind of antenna is preferred if the measurements have to take place in the near field of potential noise sources. To increase the signal-to-noise ratio, the number of measurement repetitions per pulse moment was set to 32.…”

First Measurements of Surface Nuclear Magnetic Resonance Signals Without an Oscillating Excitation Pulse – Exploiting Non‐Adiabatic Prepolarization Switch‐Off

“…This is mainly because the conventionally measured signal strength scales with the dimension of the surface loop layout. Hence, a signal from a small surface loop with a diameter of one to two meters can only be observed after long averaging, which in turn is too time‐consuming for practical applications (Costabel, 2019). The introduction of the prepolarization (PP) technique into SNMR is expected to overcome this limitation.…”