Abstract
本論文主要目的是要研製一平頂分佈的雷射光束做為飽和光束,使一快速反應(rise time =25 ns)的光二極體, 在觀測每圈同步輻射光斑大小時,可以操作在光二極體之非線性區. 如此, 可以避免以高斯光束做為飽和光束可能產生的誤差, 以增大同步輻射光斑偵測器之動態範圍.因為,用高斯光束作為飽和光束時,當待測射束有位移時,即使其光斑大小不變,亦會因而得到不同大小之訊號而造成誤判.我們使用的方法為吸收法, 以高斯光束使底片曝光, 若經由顯影與定影之過程後,得到Gamma值等於1之底片,則此底片成為一反高斯分佈之absorber,當以截面大小相同之高斯光束通過時,將產生平頂光束.而實驗結果顯示,確實可用照相之方法,沖洗出Gamma值等於1之absorber,並得到平頂光束.同時我們也將對利用二元光柵使高斯分佈之雷射能量重新分佈,得到一平頂光束之理論作一初步之瞭解.在實際觀測同步輻射電子束非相干阻尼所造成之電子束截面變化時,加一平頂飽和光束照在光二極體,確實可觀測到電子束截面產生變化. 然而,可能因為平頂飽和光束總功率不夠大,為了增加光強度以便使光二極體可以操作在特性曲線之非線性區,而犧牲了平頂飽光束之截面積,使得偏踢磁鐵踢動電子束時,同步輻射光部份跑出平頂飽和光束之範圍,造成訊號之變形. 未來, 我們可以改變光學系統增大平頂飽和光束之面積, 同時研製一功率較高之平頂光束來做改進.A fast photodiode was demonstrated to be able to extract theturn by turnphoton beam profile information of electron storagerings if the photodiodewas operated at the saturated region.When applied this method to an 1.3GeV synchrotron light sourcewith 200 mA beam current, the synchrotron radiation intensity isnot intense enough to saturate the photodiode. With a flat-topsaturating beam, we can force the photodiode operated in thenonlinear region.absorption method was used for this purpose. Wephotograph the expended gaussianbeam. If wecan manipulate theGamma value of the film to be 1, when the expendedgaussian beampassed the developed film, a flat-top beam can be obtained. Wefind that theoretical maximum efficiency of the absorptionmethod is 15.89% forthe film we used. The power of the flat-topbeamproduced by this method is toolow to saturate thephotodiode. By focusing the flat-top beam, we can increasetheintensity. However,in this way,the saturation area is too smallto cover the whole beam area,therefore,the detected photodiodesignal was deformed.Different methods of producing flat-top beamare under study these should overcome this weak point.