1.3 GHz连续波超导射频腔的数字低电平射频系统和腔模拟器设计及测试

Digital low-level radio frequency system and cavity simulator for 1.3 GHz continuous-wave superconducting radio-frequency cavity

1.3 GHz连续波超导射频腔需要高精度低电平射频(LLRF)系统来稳定超导腔的电磁场。但由于1.3 GHz CW射频腔的高负载品质因数和宽电磁频段,射频腔在频域中的电磁带宽较小。射频功率源与射频腔体之间的微小电磁频率差异易造成发生器驱动谐振器控制系统的不稳定,最终导致腔体电磁场的变化。开发了一种自激环控制系统,以防止“有质”不稳定性的发生,并补偿微噪声的影响。此外,还开发了数字1.3 GHz射频腔体模拟器,用于验证LLRF系统的设计算法。测试表明,即使在射频腔失谐5 Hz时,自激励控制系统也能确保腔场的稳定性。经过对比,验证了1.3 GHz射频腔体模拟器是测试新算法的可靠平台。

A highly precise low-level radio-frequency(LLRF)system for a 1.3 GHz continuous-wave(CW)superconducting radio-frequency(RF)cavity is required to stabilize the electromagnetic field of cavities.However,because of the high loaded quality factor and wide electromagnetic frequency band of the 1.3 GHz CW RF cavity,the RF cavity has a small electromagnetic bandwidth in the frequency domain.The small electromagnetic frequency mismatch between the RF power source and RF cavity can easily cause ponderomotive instabilities in the generator driven resonator control system,eventually resulting in variations in the electromagnetic field of the cavity.In this study,a self-excited loop(SEL)control system was developed to prevent the occurrence of ponderomotive instabilities and compensate for the effects of microphonics noise.In addition,a digital 1.3 GHz RF cavity simulator,which can easily verify the designed algorithms of the LLRF system,was developed.The recorded measurements show that the SEL control system can ensure stability of the cavity field even when the RF cavity is detuned by 5 Hz.The comparison and validation have verified that the cavity simulator is a reliable platform to test the new algorithms.