NSRRC Activity Report 2022

Facility Development and Status 095 Current Pulse The diagram of a circuit composed of a digital pulse generator (DG535, Stanford Research), voltage comparator circuit, and metal-oxide- semiconductor field-effect transistor (MOSFET) circuit is presented in Fig. 2 . The system uses the digital pulse generator to trigger the MOSFET and the voltage comparator circuit to filter noise from the circuit. When the MOSFET is triggered, the power supply (PAN110-5A, Kikusui) provides a current of 0–2.5 A to the wire. The digital pulse generator can be used to control the current pulse width and frequency. Wire-Displacement Detection System The pulsed wire measurement system includes a wire-displacement detection system on one side of the undulator. The detection system includes vertical and horizontal optical sensor pairs. Each pair comprises a diode laser (LNC-13MMC, 633 mm, Schäfter+Kirchhoff) and a photodiode (SM05PD3A, Thorlabs) mounted on a motorized stage, as shown in Fig. 3 . The active area of the photodiode is 1.1 × 1.1 mm 2 ; the rise and fall times are 15 ns. A current-to-voltage converter (PDA200C, Thorlabs) is used for measuring the photodiode current and output voltage with a digital multimeter (34465A, Keysight). The wire-displacement detection method employs a laser beam focused on the wire; the photodiode installed on the side opposite the laser is used to detect the intensity of the light not blocked by the wire. A motorized stage scans the vertical and horizontal optical sensor pairs. The performance of the wire-displacement detection system is presented in Fig. 4 (see next page); a linear range is used to detect the wire displacement. Measurement in a 2-m Undulator The pulsed wire system was used to measure the magnetic field of an in- vacuum undulator (period: 22 mm, magnetic length: 2 m). In this undulator, the direction of the magnetic field is vertical; the wire displacement is only horizontal. The following formulae were used to evaluate the pulse width ∆ t1st and ∆ t2nd for the first and second integral measurements: Fig. 1 : Design of pulsed wire system installed on in-vacuum undulator. Fig. 2 : Current pulse generation circuit. Fig. 3 : Wire-displacement detection system installed on the 2D motorized linear stage.