Seonghoon Jeong

Improvement of the pulsed wire method for undulator magnetic-field measurement

The U10 undulator for the Pohang Light Source was measured with a pulsed wire measurement (PWM) method. By adjusting the aperture of the slotted optical switch (SOS) for PWM, the sensitivity of SOS output to the wire displacement improved significantly. A calibration table, which translates the output voltage to the displacement of wire, was obtained and the linearity of the PWM was enhanced using this table. The magnetic-field profile of the U10 undulator measured with the PWM method agrees well with that measured with Hall probe mapping. The effect of the wire dispersion on PWM is also discussed.

Laminated magnetic flux sensor for thick-steel-plate control

This paper presents a rugged magnetic flux sensor, which can measure the thickness of steel plates and can operate reliably in the poor environment of a warehouse for thick steel plates. The sensor, consisting of a laminated sensing plate and a sensing coil, has a size of 6/spl times/6 cm/sup 2/, and it is embedded inside the core of a lifting magnet. Depending on the thickness of steel plates attached on the lifting magnet, the magnetic permeability of the core and the sensing plate changes. The thickness of steel plates is indirectly measured by measuring the changes in the magnetic flux density of the sensor. The measurement sensitivity of the magnetic flux sensor with laminated sensing plate is much better than that of a sensor with a solid sensing plate. With a proper procedure for securing measurement reliability, it is demonstrated that the sensor can measure up to 13 sheets of 6-mm steel plate.

Development of a Precision Amplifier for the Detector

A trans-resistance amplifier has been designed and tested to measure the intensity of synchrotron radiation at Pohang Light Source (PLS). The front-end stage of the amplifier was implemented using discrete circuit elements and can measure input current in the range of 1 pA to 1 μA. A microprocessor interfaces the amplifier with computer and controls the other sub-circuits for synchrotron radiation measurement. The amplifier was tested and obtained a resolution of ∼ 20 fA, a temperature drift of ∼ 0.1 pA/°C, and a signal-to-noise ratio greater than 80 dB.

Laminated magnetic flux sensor for thick steel plate control

This paper presents a rugged magnetic flux sensor, which can measure the thickness of steel plates and can operate reliably in the poor environment of a warehouse for thick steel plates. The sensor, consisting of a laminated sensing plate and a sensing coil, has a size of 60 mm/spl times/60 mm, and it is embedded inside the core of a lifting magnet. Depending on the thickness of steel plates attached on the lifting magnet, the magnetic permeability of the core and the sensing plate changes. The thickness of steel plates is indirectly measured by measuring the changes in the magnetic flux density of the sensor. The measurement sensitivity of the magnetic flux sensor with laminated sensing plate is much better than that of a sensor with a solid sensing plate. With a proper procedure for securing measurement reliability, it is demonstrated that the sensor can measure up to 14 sheets of 6 mm steel plate.