摘要
肖特基诊断是同步环加速器束流参数的一种重要测量手段,可用于束流回旋频率、动量分散、工作点等多个参数的测量。电容型探针是开展肖特基信号测量的常用手段,但常规的电容型探针灵敏度低,在粒子数较少时测量信噪比差,难以获得有效的测量结果。电容型探针可等效为RC并联电路,通过添加并联电感形成RLC电路可实现信号的谐振放大。通过建立谐振放大等效电路模型,分析了影响谐振放大倍数以及信噪比的主要因素。开展了谐振放大电路研制,在西安质子应用装置进行了实验验证,实现了Q为177的谐振放大,将测量信噪比提升了22.9 dB。
Schottky noise diagnostic is a very important method to measure beam revolution frequency,momentum spread,tune,and chromaticity,etc.,in the synchrotron.Capacitive pickups are widely used to measure Schottky noise.However,the application of the pickups is limited in low-intensity rings due to their low sensitivity.The capacitive pickup can be modeled as an RC parallel circuit,where R is the input impedance of the front-end FET low-noise amplifier and C is the ground capacitance of the pickup.Usually,the impedance of the RC circuit is determined by the ground capacitance C and is much smaller than R.To increase the impedance,a parallel inductance is added to form an RLC parallel resonant circuit,whose impedance is just R at the resonance frequency ideally.Actually,the amplification factor is the quality factor of the resonant circuit,which is mainly affected by the parasitic resistance of the added inductor.Noises may also be amplified by the resonant circuit,which is unfavorable for improving the pickup sensitivity.Noise analysis was performed with an RLC equivalent model,the results show that the input noise current of the FET amplifier is the main contributor at the neighbor of the resonance frequency,and the input noise voltage of the amplifier contributes more at off-resonance frequencies.Take the FEMTO HVA-200M-40-F amplifier,which has equivalent input noise voltage density and current density of 4.5 nV/Hz and 2 pA/Hz,respectively,for example,total noise at the resonance frequency is about 10 times larger than that at off-resonance frequencies owing to the high impedance at the resonance frequency.Due to the small size and high Q-factor of the helical resonator,a helical resonator with 2.57μH was designed and constructed,and connected to the capacitive pickup in parallel.The performance of the RLC parallel resonant circuit was tested with a wire setup.Signal amplification of 44.5 dB at the resonance frequency is achieved by the resonant circuit with a 19.8 dB increase of the noise at the same time.Overall,ad
作者
王敏文
王忠明
邱孟通
赵铭彤
王迪
王茂成
卓鑫
闫逸花
WANG Minwen;WANG Zhongming;QIU Mengtong;ZHAO Mingtong;WANG Di;WANG Maocheng;ZHUO Xin;YAN Yihua(State Key Laboratory of Intense Pulsed Radiation Simulation and Effect,Northwest Institute of Nuclear Technology,Xi’an 710024,China)
出处
《原子能科学技术》
EI
CAS
CSCD
北大核心
2023年第7期1435-1442,共8页
Atomic Energy Science and Technology
关键词
肖特基噪声
谐振放大
电容型探针
同步环
Schottky noise
resonant amplification
capacitive pickup
synchrotron
