Acoustic emission during quench training of superconducting accelerator magnets

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The HQ magnet is a 120 mm aperture, 1-meter-long Nb3Sn quadrupole developed by the LARP collaboration in the framework of the High-Luminosity LHC project. A first series of coils was assembled and tested in 5 assemblies of the HQ01 series. The HQ01e model achieved a maximum gradient of 170 T/m at 4.5 K at LBNL in 2010-2011 and reached 184 T/m at 1.9 K at CERN in 2012. A new series of coils incorporating major design changes was fabricated for the HQ02 series. The first model, HQ02a, was tested at Fermilab where it reached 98% of the short sample limit at 4.5 K with a gradient of 182 T/m in 2013. However, the full training of the coils at 1.9 K could not be performed due to a current limit of 15 kA. Following this test, the azimuthal coil pre-load was increased by about 30 MPa and an additional current lead was installed at the electrical center of the magnet for quench protection studies. The test name of this magnet changed to HQ02b. In 2014, HQ02b was then shipped to CERN as the first opportunity for full training at 1.9 K. In this paper, we present a comprehensive summary of the HQ02 test results including: magnet training at 1.9 K with increased pre-load, quench origin and propagation, and ramp rate dependence. A series of powering tests was also performed to assess changes in magnet performance with a gradual increase of the MIITs. We also present the results of quench protection studies using different setting for detection, heater coverage, energy extraction and the Coupling-Loss Induced Quench (CLIQ) system. However, the full training of the coils at 1.9 K could not be performed due to a current limit of 15 kA. Following this test, the azimuthal coil pre-load was increased by about 30 MPa and an additional current lead was installed at the electrical center of the magnet for quench protection studies. The test name of this magnet changed to HQ02b. In 2014, HQ02b was then shipped to CERN as the first opportunity for full training at 1.9 K. In this paper, we present a comprehensive summary of the HQ02 test results including: magnet training at 1.9 K with increased preload, quench origin and propagation, and ramp rate dependence. A series of powering tests was also performed to assess changes in magnet performance with a gradual increase of the MIITs. We also present the results of quench protection studies using different setting for detection, heater coverage, energy extraction and the Coupling-Loss Induced Quench (CLIQ) system.

Section: A Test Instrumentation and Electrical Quality Assurancementioning

confidence: 99%

Test Results of the LARP HQ02b Magnet at 1.9 K

Bajas

Ambrosio

Anerella

et al. 2015

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“…Transverselypolarized piezo-transducers (PZT)-ceramics ring elements of 10 mm in diameter and 1 mm in thickness are used as sensing elements. PZT elements are interfaced to MOSFET-based cryogenic preamplifiers with a bandwidth of 100 Hz-300 kHz and operational temperature range of 300-1.9 K [8]. Use of MOSFETs allows converting a high piezo-element impedance down to ∼1 kΩ, thus significantly improving signal-to-noise ratio, and allowing for regular "twisted pair" cables being used instead of coax for instrumenting the sensors to the cryostat header and then further on to the coupling box.…”

Section: A Ae Sensor Hardware and Installationmentioning

confidence: 99%

Localization of Quenches and Mechanical Disturbances in the Mu2e Transport Solenoid Prototype Using Acoustic Emission Technique

Marchevsky¹,

Ambrosio²,

Lamm³

et al. 2016

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Acoustic emission (AE) detection is a noninvasive technique allowing the localization of the mechanical events and quenches in superconducting magnets. Application of the AE technique is especially advantageous in situations where magnet integrity can be jeopardized by the use of voltage taps or inductive pickup coils. As the prototype module of the transport solenoid (TS) for the Mu2e experiment at Fermilab represents such a special case, we have developed a dedicated six-channel AE detection system and accompanying software aimed at localizing mechanical events during the coil cold testing. The AE sensors based on transversely polarized piezoceramic washers combined with cryogenic preamplifiers were mounted at the outer surface of the solenoid aluminum shell, with a 60 • angular step around the circumference. Acoustic signals were simultaneously acquired at a rate of 500 kS/s, prefiltered and sorted based on their arrival time. Next, based on the arrival timing, angular and axial coordinates of the AE sources within the magnet structure were calculated. We present AE measurement results obtained during cooldown, spot heater firing, and spontaneous quenching of the Mu2e TS module prototype and discuss their relevance for mechanical stability assessment and quench localization.

“…6b). The receiver transducers were combined with MOSFET cryogenic preamplifiers [17]. Experiments were conducted in liquid nitrogen.…”

Section: Quench Detection In Corc ® Dipole Coil Assemblymentioning

confidence: 99%

Quench Detection for High-Temperature Superconductor Conductors Using Acoustic Thermometry

Marchevsky

Hershkovitz

Wang

et al. 2018

Abstract-Detecting local heat-dissipating zones in hightemperature superconductor (HTS) magnets is a challenging task due to slow propagation of such zones in HTS conductors. For long conductor lengths voltage-based methods may not provide a sufficient sensitivity or redundancy, and therefore non-voltage based detection alternatives are being sought. One of those is the recently proposed method of Eigen Frequency Thermometry (EFT), which is an active acoustic technique for a fast and non-intrusive detection of "hot spots", utilizing temperature dependence of the conductor elastic moduli. In the present work, we demonstrate efficiency of EFT for detecting localized heating in a 1.2 m-long sample of REBCO tape immersed in liquid nitrogen, and benchmark sensitivity of the acoustic detection with respect to voltage, hot spot temperature, and power dissipation in the conductor. Modifying the original technique for differential mode of operation enables a much improved sensitivity, and adds a hot spot localization capability. Furthermore, we adapt this technique to subscale coils wound with REBCO CORC® conductor built in the framework of US Magnet Development Program. A successful thermal-based detection of dissipation onset at the critical current for a two-layer canted CORC® dipole assembly is discussed. Index Terms-Acoustic sensors, temperature sensors, superconducting coils, high-temperature superconductors, quench detection.