BESIII亮度监测器的运行结果PPT课件.ppt

BESIII 亮度监测器的运行结果薛镇1Outline•亮度监测器原理和结构•亮度监测器相对亮度的测量的精度•亮度监测器的bunch by bunch测量•利用亮度监测器对束团尺寸的测量2亮度监测器的原理和结构亮度监测器的原理和结构单轫致辐射过程•e+ e-  e+ e-  通过探测  来确定亮度•截面大，可以实现快速更新 ～161 mb when kt=50MeV•出射的 沿着束流方向且张开角度很小，0.5 mrad以内的光子占66%以上@1.89GeV “零角度亮度探测器”3•切伦科夫介质采用 熔融石英 (fused silica)Ø非常高的抗辐照性能 (>109 rad/y)Øn=1.46•采用钨作转换体•仅测计数，所占空间小•主要用于相对测量亮度监测器的原理和结构亮度监测器的原理和结构4surrounded by tungsten shield Light pipe 钨fused silicaPMT钨转换体厚为1.2cm熔融石英的几何尺寸为 4.5 x 4.0 x 6.6 cm3亮度监测器的原理和结构亮度监测器的原理和结构5 According to Fig. (a) and (b) the ratio between the counting rates with separated beams and colliding beams are lower than 3.5%.Fig. (a) Counting rate with colliding beams normalized by the current of e- and e+ bunches vs. the FEE threshold. Fig. (b) Counting rate with separated beams normalized by the current of e- and e+ bunches vs. the FEE threshold.相对亮度测量的精度相对亮度测量的精度6 相对亮度测量的精度相对亮度测量的精度According to the table above the error of relative luminosity with threshold of 400mV and the pair of bunches currents of 5×5mA2 is about 0.9%.the counting rates and their errors due to different thresholds in SBBS (I+=5.11mA,I-=5.00mA）Thr.(mV)100200300400500600800100012001400 2599119946162451353511281922660363305150964925992199461624513535112819226603633051509649 16114112711610696785739258575754203062501921205817.5029242017161411840317752441319914166281385311335741440641866811204179161147134121987249250.0081 0.0092 0.0102 0.0111 0.0121 0.0134 0.0166 0.0222 0.0326 0.0081 7 相对亮度测量的精度相对亮度测量的精度由上图可见,东西零角度亮度监测器给出的相对亮度的趋势和量能器端盖的亮度值的趋势接近8零角度亮度监测器能够给出各个束团的相对亮度,从而使调束人员对各个束团的注入和对撞情况有了清楚的了解.亮度监测器的亮度监测器的bunch by bunchbunch by bunch测量测量9从纵向扫描看,前5个束团明显比后5个束团注入质量更高;从横向扫描看,这一点不明显,因为横向的束团尺寸较大.亮度监测器的亮度监测器的bunch by bunchbunch by bunch测量测量10By steering the electron beam while observing the counting rate changes of the luminosity monitor, the horizontal and vertical sizes of the bunch spots can be estimated as shown in the figure. There are 70 e+ bunches and 10 e- bunches stored in the storage rings. The total e+ current is 321.660 mA, the total e- current is 54.758 mA. The data of the figure is of the fifth e+ and e- bunch pair. Fitted by gaussian function, the horizontal standard deviation σx=0.50±0.01mm, the vertical standard deviation is σy=0.0146±0.0003mm. , Supposing σe+ = σe- in both horizontal and vertical direction, then 利用亮度监测器对束团尺寸的测量利用亮度监测器对束团尺寸的测量11σx=0.636mm, σy=0.015mm which is close to the luminosity monitor resultσx=0.50±0.01mm,σy=0.0146±0.0003mm. 利用亮度监测器对束团尺寸的测量利用亮度监测器对束团尺寸的测量12。