Successful Reposition of an Incarcerated Gravid Uterus by Instrument:A Case Report and Literature Review

Incarcerated gravid uterus is a rare obstetric condition that contributes to pregnancy-related adverse outcomes,especially if the uterus remains incarcerated and the condition goes undiagnosed until delivery.An effective diagnosis of this condition is benefited from pelvic examination combined with imaging methods and based on suspected symptoms.We present a case of ultrasound-assisted instrument reposition of an incarcerated gravid uterus at mid-gestation and discuss its clinical characteristics,diagnosis,imaging features,and treatment.We believe that once manual reduction fails,the use of instruments will undoubtedly be a better choice.

Superconducting multipole wiggler with large magnetic gap for HEPS-TF

A 16-pole superconducting multipole wiggler with a large gap of 68 mm was designed and fabricated to serve as a multipole wiggler for HEPS-TF.The wiggler consists of 16 pairs of NbTi superconducting coils with a period length of 170 mm,and its maximum peak field is 2.6 Tesla.In magnet design,magnet poles were optimized.Furthermore,the Lorentz force on the coils and electromagnetic force between the upper and lower halves were computed and analyzed along with the stored energy and inductance at different currents.To enhance the critical current of the magnet coil,all the pole coils selected for the magnet exhibited excellent performance,and appropriate prestress derived from the coil force analysis was applied to the pole coils during magnet assembly.The entire magnet structure was immersed in 4.2-K liquid helium in the cryostat cooled solely by four two-stage cryocoolers,and the performance test of the superconducting wiggler was appropriately completed.Based on the measured results,the first and second field integrals on the axis of the superconducting wiggler were significantly improved at different field levels after the compensation of the corrector coils.Subsequently,the wiggler was successfully installed in the storage ring of BEPCII operation with beams.

Hall sensor angle error and relative position calibrations for cryogenic permanent magnet undulator of high energy photon source test facility(HEPS-TF)

Purpose A new in-vacuum three-dimensional Hall probe magnetic measurement system is under fabrication for characterizing the magnetic performance of the Cryogenic Permanent Magnet Undulator(CPMU).In order to fit the small gap(5 mm)of magnetic structure and vacuum environment,a small three-dimensional Hall probe has been manufactured.The angular and positional misalignment errors of the Hall sensors play an important role in the measurement accuracy of the CPMU.In order to minimize the misalignment errors,a method of calibrating angle error and relative assembly displacements of a three-dimensional Hall probe is carried out.Methods The angle error of Hall sensors will be calibrated by a standard dipole magnet and a five-dimensional Hall bench.The standard dipole magnet will generate a single direction and uniform magnetic field.And the fivedimensional Hall bench is used to rotate the Hall probe which is put in the center of magnet.Based on the relationship between angle and magnetic field strength,the angle error of each Hall sensor will be obtained.The relative position between the sensitive areas of the Hall sensors will be calibrated by a two-dimensional magnetic field undulator section.Based on Maxwell’s equations,through the calculation of measurement magnetic field strength,the relative assembly displacements of the three Hall sensors can be derived.Results The details of the calibration methods and the data processing of angle error and relative assembly displacements of a three-dimensional Hall probe are presented.The three-dimensional magnetic fields of a cryogenic permanent magnet undulator can be received accurately by correcting these angle errors and position errors of Hall sensors.Conclusions This paper illustrates the relative position and angle calibration procedures and the data processing of a three-dimensional Hall probe.Now the design of a smaller Hall probe is in process.The calibration of the angle errors and position errors will be carried out after the fabrication of the standard dipole magnet.

Single-blockmeasurement for the cryogenic permanent magnet undulator sorting

Purpose The magnet sorting is a standard step in the undulator fabrication procedure.The shortest undulators period used in the High Energy Photon Source(HEPS)is only 12 mm.To the short period undulator,the sorting may be more important than the long-period undulator.Normally,the Helmholtz measurement is used as the input for the work.It is the averaged orthogonal magnetization of each block.In order to investigate whether the Helmholtz coil measurement is enough for the sorting,a careful study has been made.Method Firstly,a magnetic camera was used to scan the 3D surface field of a magnet.Afterward,its field integral ismeasured by the stretched wire.In the measurement,the magnetwas placed at different statuses.The results were checked to seewhether they are consistent with expected features supposing a homogeneous magnetized block.Finally,the results measured by the Helmholtz coil and the stretched wire were compared.Results The surface field scan demonstrates that the field over a magnet block is inhomogeneous.Moreover,the field integral measurement by the stretched wire also shows big difference when the different magnet sides toward thewire.The comparison between the stretched wire and the Helmholtz coil measurement shows no correlation.Conclusion The study presented in this paper reveals that the homogeneity of the magnetization is imperfect.Therefore,the Helmholtz coil data are insufficient to the short-period undulators sorting.

Magnetic field strength and temperature-dependent calibration system of Hall probe for the HEPS-TF cryogenic permanent magnet undulator

Purpose High energy photon source test facility(HEPS-TF)has manufactured a three-dimensional Hall probe to measure the cryogenic permanent magnet undulator(CPMU).Since the operating environment of the CPMU is the subcooled liquid nitrogen(85K),the temperature of the Hall probe will have a decrease of several degrees while carrying out the local magnetic measurement.We established a magnetic field strength and temperature-dependent calibration system to calibrate the Hall probe.Methods The magnetic field strength of the Hall probe was calibrated by a standard dipole electromagnet and a nuclear magnetic resonance Tesla meter(NMR).The temperature of Hall probe was controlled by a control system which can modulate temperature from 0℃ to 30℃.Results A new homemade Hall probe has finished the temperature-dependent(0℃ to 30℃),magnetic field strength(-1.2 to 1.2 T)and angle error calibration at this new calibration system.The temperature correction error is less than 0.045%.The calibration error of magnetic field strength is less than 1.5 Gs.The RMS calibration error of Hall sensors angle matrix is less than 5.1E-5.Conclusion The magnetic field strength and temperature-dependent calibration system including a standard dipole electromagnet,a temperature regulation system,an NMR and a five-dimensional Hall bench was established.The detailed magnetic field strength and temperature-dependent calibration system is introduced and the results of the calibrations are presented.

Research on magnetic centermeasurement of quadrupole and sextupole using vibrating wire alignment technique in HEPS-TF

Purpose In order to meet the extremely low emittance requirement,the magnets in the storage ring of high-energy photon source(HEPS)need to have a stable support and precise positioning.In HEPS-TF,the key and difficult technologies of HEPS should be researched and developed.Vibrating wire alignment technique is one important project of HEPS-TF.It can be used to pre-align the quadrupoles and sextupoles on one girder with high precision.A vibrating wire measurement system was set up and tested to verify the magnetic center measurement precision and the magnet adjustment error.Methods There are one sextupole and one quadrupole installed on a multipole girder.Vibrating wire is stretched through mechanical center of the magnet apertures and supported by the test benches on the two sides.A single conducting wire is stretched through themagnet aperture and electrified by alternating current.The wire will vibrate for a period of Lorentz force.By matching the current frequency to one mode of natural frequency of the wire,the vibrating amplitude will be enhanced.And by measuring the vibrating amplitude,the magnetic field at the wire position can be got.Moving the wire across the magnet aperture in the transversal or vertical direction,the distribution of magnetic field and magnetic center position can be measured.According to the magnetic center position error to adjust the magnet.Measure the magnetic center of all magnets installed on the multipole girder one by one,and adjust their magnetic center to a line.Results The magnetic center measurement precision is better than±3μm,and the magnet adjustment error is less than 6μm.Conclusion The vibrating wire system design and a series of magnetic center measurement experiments have gained good achievements.It has been proved the vibrating wire system is designed reasonable and using the vibrating wire to align the magnets installed on a multipole girder is feasible and can reach a high precision.

Influence of cryogenic permanent magnet undulator motion error on magnetic field error and radiation intensity loss

A cryogenic permanent magnet undulator prototype designed for Chinese High Energy Photon Source Test Facility(HEPSTF)at Institute of High Energy Physics is constructed and now commissioning.Motion precision of girders is a significant parameter to guarantee gap error so as to avoid phase error and radiation intensity loss.In order to study and minimize girder parallelism errors,RADIA and SPECTRA are used to calculate qualified motion precision.Spring Modules and single motor closed-loop feedback are designed to compensate the errors.Magnetic field is finally tuned to reach specifications.Details of the study and analysis will be presented in this paper.