Takeyoshi Ohtani

High Tc SQUID Detection System for Metallic Contaminant in Lithium Ion Battery

A highly sensitive detection system for magnetic contaminants using a High-Tc superconducting quantum interference device (SQUID) was developed. Finding ultra-small metallic contaminants is a big issue for manufacturers producing commercial products such as lithium ion batteries. When the contamination does occur, the manufacturer of the product suffers a great loss to recall the tainted products. The outer dimension of metallic particles less than 100 microns can not be detected by X-ray imaging, which is commonly used as the inspection method. In most cases, the matrix of industrial products is magnetized and the magnetic signal from the matrix is large enough to mask the signal from contaminants. We developed a detection system based on a high-Tc SQUID gradiometer. A specially designed low noise planar gradiometer for the system was developed. The flux white noise level of the SQUID gradiometer was 8-16 muphi0/Hz1/2 at 1 kHz. Use of the gradiometer and horizontal magnetization could solve problem above. We tested the performances of the system and found that small iron particles as small as 50 mum times 50 mum on the electrode of the lithium ion battery could be clearly detect. This detection level is difficult to achieve using other methods.

Development of Metallic Contaminant Detection System Using Eight-Channel High-

In this paper, a roll-to-roll eight-channel (8-ch) high-Tc superconducting quantum interference device (SQUID) detection system for magnetic contaminants in a lithium-ion (Li-ion) battery anode sheet was developed. Finding ultra-small metallic foreign matter is an important issue for a manufacturer because metallic contaminants carry the risk of an internal short. When contamination occurs, the manufacturer of the product suffers a great loss from recalling the tainted product. Metallic particles with outer dimensions smaller than 100 μm cannot be detected using a conventional X-ray imaging system. Therefore, a highly sensitive detection system for small foreign matter is required. We have already developed a detection system based on a single-channel SQUID gradiometer and horizontal magnetization. For practical use, the detection width of the system should be increased to at least 65 mm by employing multiple sensors. In this paper, we present an 8-ch high-Tc SQUID roll-to-roll system for inspecting a Li-ion battery anode with a width of 65 mm. A special microscopic type of a cryostat was developed upon which eight SQUID gradiometers were mounted. As a result, small iron particles of φ35 μm on a real Li-ion battery anode with a width of 70 mm were successfully detected. This system is practical for the detection of contaminants in a Li-ion battery anode sheet.

T_{c}

Magnetic nanoparticle imaging (MPI) utilizes the non-linear magnetization response M for the detection of superparamagnetic iron oxide magnetic nanoparticles (MNPs). When an external ac magnetic field is applied to the MNPs, some harmonic responses such as second, third, and higher ones arise. We propose and demonstrate that the use of the second-harmonic response is the most effective technique to enhance the signal. The advantage of using the second-harmonic response is that the response can be measured even in a small ac field. A 2-D MPI system using this technique was realized and its performance was evaluated. The MPI system has no mechanical parts but instead magnetically scans an MNP phantom by changing the dc bias field in two directions. The cosine component of the signal is detected by a lock-in-amplifier and differentiated in one direction. The image of the phantom is then reconstructed using the d(cosθ)/dz data. As a result, the position of the phantom may be identified down to the iron content of 9 μg.

SQUIDs

We developed a metallic contaminant detector using a high-Tc rf-SQUID with a Cu pickup coil for industrial products. For manufacturers producing industrial products, problems arising from metallic contaminants are critical issues. A detection system using a SQUID is a powerful tool for sensitive inspections. However, since the detection width is dependent on the size of the SQUID, multiple sensors are required for practical use. However, such devices are costly and complicated. This is the reason as to why the SQUID system has not been widely used in the field. Therefore, we have recently proposed a new detection system using Faradays law of electromagnetic induction. The detection section consists of a pair of permanent magnets surrounded by copper wound pickup coils. The output of the pickup coil is remotely connected to a copper wound input coil. The input coil couples magnetically with a SQUID. In this case, the width of the pickup coil can be widened as to be as large as 27 mm in diameter. As compared with 1-ch SQUID direct detection, the width of the new method is three times larger. In this paper, we describe the performance of the system with a conveyor, which uses an LC resonant circuit. By applying the LC resonance, the amplitude increased and the signal to noise ratio (SNR) was improved by a factor of two.

Imaging of Magnetic Nanoparticles Using Second-Harmonic Signals

Metallic particles with outer dimensions smaller than 100 microns in Li-ion battery cannot be detected using a conventional X-ray imaging system. We propose two systems using high Tc SQUIDs: One is a direct detection type and the other is an indirect type. In the direct detection system, an object with a contaminant is magnetized by a permanent magnet and then the remanent field of the contaminant is detected by SQUID. In the indirect detection system, the principle is based on Faradays law of electromagnetic induction. The diameter of the detection coil is 2 to 3 times larger than the SQUID; as a result, less number of SQUIDs, two or three is enough to inspect a specimen with a width of 65 mm. This method is applicable for an inspection of metallic contaminants in non-magnetic film such as a separator for Li-ion battery. We discuss the results of the evaluation of the new system as compared with a direct detection system.

Development of Metallic Contaminant Detection System Using RF High-Tc SQUID With Cu Pickup Coil

We develop magnetic metallic contaminant detectors using high-temperature superconducting quantum interference devices (HTS-SQUIDs) for industrial products. Finding ultra-small metallic contaminants is an important issue for manufacturers producing commercial products such as lithium ion batteries. If such contaminants cause damages, the manufacturer of the product suffers a big financial loss due to having to recall the faulty products. Previously, we described a system for finding such ultra-small particles in food. In this study, we describe further developments of the system, for the reduction of the effect of the remnant field of the products, and we test the parallel magnetization of the products to generate the remnant field only at both ends of the products. In addition, we use an SQUID gradiometer in place of the magnetometer to reduce the edge effect by measuring the magnetic field gradient. We test the performances of the system and find that tiny iron particles as small as 50 × 50 μm2 on the electrode of a lithium ion battery could be clearly detected. This detection level is difficult to achieve when using other methods.

Metallic Contaminant Detection System Using Multi-Channel Superconducting Quantum Interference Device (SQUID)

Mixture of metallic contaminants to food is serious problems not only for consumers but manufactures. To ensure the food safety, finding small metallic contaminants is important. A metal contaminant may come from a machine in the process of food and it contaminates food. Finding small metallic contaminants is important for food safety. Food manufactures are installing inspection systems such as eddy current detectors and X-ray imaging. The eddy current metal detector is widely used in a food factory. However, the sensitivity (threshold level) is not stable and is highly influenced by the conductivity of the material. The X-ray imaging is a useful technique and is getting popular in food factories and other industries. However, the lower detection limit for practical X-ray usage is in the order of 1 mm. Moreover, X-ray radiation sometimes causes ionization of the food, which may often change a taste of the food.

Metallic Contaminant Detection using a High-Temperature Superconducting Quantum Interference Devices Gradiometer

We propose and demonstrate a high-Tc SQUID(Superconducting Quantum Interference Devises) magnetic metallic contaminant detector using Faradays law of electromagnetic induction for food and industrial products. For manufacturers producing items such as processed food and industrial products, problems with metallic contaminants are critical issues. The lower detection limit for practical X-ray usage is on the order of 1 mm. A detection system using a SQUID is a powerful tool for sensitive inspections. An iron pellet with a size of 40 μm is successfully detected by the proposed system.

Development of three channel SQUIDs contaminant detector for food inspection

We developed a magnetic contaminant detection system for industrial products such as electrode foils of lithium ion battery employing eight high-Tc SQUID gradiometers. The system was based on pre-magnetization of a contaminant in an object under test by means of permanent magnets of 0.5 T, which magnetization direction was horizontal, in order to suppress the edge effect from the object composed of magnetic material. The object was conveyed to pass under the eight-channel gradiometer array, in which a pair of four gradiometers was aligned in two rows to cover target foils of several tens mm in width. The magnetization from the contaminant in the object was detected by the gradiometers of averaged flux white noise level of 25 μ0/Hz1/2. In case that an iron ball passed just under one gradiometer, an iron ball of about 30 μm in diameter was successfully detected with a signal to noise ratio (S/N) of 5. From measurement results using an iron ball of about 100 μm in diameter, it was demonstrated that the system had a detectable range of 70 mm in width. There results suggest that the system is a promising tool for the quality control of lithium ion batteries.