脉冲弦线磁场测量方法的实验研究

EXPERIMENTAL INVESTIGATION OF PULSED-WIRE MAGNETIC FIELD MEASURING METHOD

介绍了脉冲弦线磁场测量方法的基本原理和实验装置，研究了脉冲电流宽度对测量结果的影响，观测到双波叠加的新现象。该现象很好地解释了零信号的产生原因，并由此可以确定测量磁场二次积分时的脉冲电流宽度。

AbstractA experimental investigation of pulsed-wire magnetic field measuring method with limited-width current pulse excitation has been made with the pulsed-wire setup and a 8-periodwiggler model. The layout of the system is shown in Fig. 1. A0.05mm tungsten wire is threadedthrough the wiggler and stretched between two teflon pulleys, each of which is on an x-ytranslation stage, it allow us to align the wire, A weight equal to 200g provides sufficientwire tension to make it straight.The transverse wave speed is 250ms￣(-1). The detector systemused was similar to the one decribed in ref. [1, 6]. The detector is a Honeywell HOA1872transmissive sensor, which is on an x-y translation stage. Fig. 2 shows the wire displacementat detector on several current pulses.We find the number of signal period is different fromthat of the measuredwiggler from Fig. 2. We draw a conclusion that the measured signal atdetector consist of two waves, first waveform is the same as second, their phase is back andtheir interval versus time is just the width of current pulse.This conclusion can be usedto interpret null signal phenomenon.When the transverse wave speed is 250ms￣(-1),theperiod of measured wiggler is 1cm, the period of transverse wave is 40μs. If the width ofcurrent pulse is just 40μs, the first wave and second wave will cancel each other outbesides the entrances. When the width of current pulse is increased, the second wave movebackward versus time relative to the first wave but the first wave is steady versus time andthe interval of two waves is always width of current pulse.Increasing the width of thepulse until it is longer than L/v(L is the effective length of the wiggler, it include edgemagnetic field, v is the transverse wave speed), the two waves don't overlapping each otheragain.After that,increasing the width further, the first waveform will not be changed at alland second wave will disappear. It is seen in Fig, 2(f). So we get such a conclusion thatthe first wave corresponds to the second integral of the magnetic field, if the width ofcurrent pulse is longer than L/v.