Feedback Optimization of Pulse Width in the SORC Sequence

Schiano, J.L.; Routhier, T.; Blauch, A.J.; Ginsberg, Mark D.

doi:10.1006/jmre.1999.1824

Cited by 12 publications

(14 citation statements)

References 12 publications

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“…Experiments were performed at both liquid nitrogen (77 K) and room (Ӎ294 K) temperature. All experiments were conducted at the Ϫ transition in 14 N. The transition frequency Ϫ is 3.757 MHz at liquid nitrogen temperature and approximately 3.6 MHz at room temperature. When immersed in liquid nitrogen the sample is at a constant temperature, making variations in Ϫ , due to temperature, negligible.…”

Section: Methodsmentioning

confidence: 99%

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Optimization of Offset Frequency in the SORC Pulse Sequence Using Feedback

Blauch¹,

Schiano²,

Ginsberg³

1999

Journal of Magnetic Resonance

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Section: Methodsmentioning

confidence: 99%

“…The pulse width optimization of the SORC pulse sequence using feedback has recently been demonstrated (14). It was shown that a gradient tuning feedback algorithm can determine the pulse width that maximizes the SORC signal amplitude.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Offset Frequency in the SORC Pulse Sequence Using Feedback

Blauch¹,

Schiano²,

Ginsberg³

1999

Journal of Magnetic Resonance

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“…The tests were conducted with a sample of 70 g of sodium nitrite at room temperature (detection was not remote). In [26] the same feedback control methodology was suggested for adjusting pulse parameters, but it was proposed to make the tuning in a pre-screening stage, in which NQR equipment is placed over a test mine so that the algorithm finds optimal pulse parameters for the explosive material, depth, size and environmental conditions. In [27] a pulsed NQR spectrometer is described, designed specifically to facilitate real-time tuning of the pulse sequence parameters.…”

Section: Signal Processing Algorithmsmentioning

confidence: 99%

“…Although by using fixed pulse parameters the detected signal strength is sacrificed, tests in [25][26][27] were made under controlled conditions in the absence of MAPER. The presence of such signals could degrade the performance of the control system since they are added to the signal power that is used for feedback.…”

Section: Signal Processing Algorithmsmentioning

confidence: 99%

Nuclear quadrupole resonance for explosive detection

Cardona

Jiménez

Vanegas

2015

Ingeniare. Rev. chil. ing.

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Nuclear quadrupole resonance (NQR) is a spectroscopic technique that can detect explosives of high chemical specificity and therefore it is very suitable for the landmine detection problem. There are several factors affecting the relation of noise signal ratio with NQR: molecular dynamics of relaxation, interference signals, thermal noise, explosive amount, distance, temperature and the design of the detecting system. Literature has searched ways for solving one or more of these factors, but since not all the work has been focused on landmine detection, many have only been tested in simulation or with data obtained under controlled laboratory conditions, where the detection is not remote (there is no separation between the sample and the detection system). This paper makes a review of the state of art in NQR, analyzing its relevance to the landmine detection problem and concluding about unsolved problems that could be the focus of future research.Keywords: Nuclear quadrupole resonance, landmine detection, explosive detection, landmine, demining. RESUMEN

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“…This permits longer signal acquisitions per pulse train, resulting in higher SNR. In the steady-state, free precession sequence (SSFP) used in NMR [9], and its variations applied in NQR, the strong off-resonance comb (SORC) [10][11][12] and the transmission onreception off (TONROF) [13], the time τ is commonly set to be less than the T 2 , which leads to the steady-state condition. When this condition is fulfilled, the signal amplitude in each acquisition window between pulses is strongly augmented if the pulse spacing is reduced.…”

Section: Introductionmentioning

confidence: 99%

RF probe recovery time reduction with a novel active ringing suppression circuit

Peshkovsky

Forguez²,

Cerioni

et al. 2005

Journal of Magnetic Resonance

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A simple Q-damper device for active probe recovery time reduction is introduced along with a straightforward technique for the circuit's component value optimization. The device is inductively coupled to a probe through a coupling transformer positioned away from the main coil, which makes the design independent of the coil type being used. The Q-damper is a tuned circuit, which is resonant at the same frequency as the probe and can be actively interrupted. When the circuit is interrupted, it is detuned and, thereby, is uncoupled from the probe, which operates normally. Turning the device on leads to re-coupling of the circuits and causes splitting of the probe's resonance line, which can be observed through its drive port. A resistance of an appropriate value is introduced into the Qdamper circuit, resulting in smoothing of the resonance splitting into one broad line, representing the coupled system's low-Q state, in which the energy stored in the main coil is efficiently dissipated. The circuit's component values are optimized by monitoring the shape of this low-Q state. Probe recovery time reduction by, approximately, an order of magnitude has been obtained with this device. Application of the device during an NQR experiment led to an increase in the signal-to-noise ratio by a factor of 4.9.

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Feedback Optimization of Pulse Width in the SORC Sequence

Cited by 12 publications

References 12 publications

Optimization of Offset Frequency in the SORC Pulse Sequence Using Feedback

Optimization of Offset Frequency in the SORC Pulse Sequence Using Feedback

Nuclear quadrupole resonance for explosive detection

RF probe recovery time reduction with a novel active ringing suppression circuit

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