Frequency control and pre-tuning of a large aperture 500 MHz 5-cell superconducting RF cavity

The 500 MHz 5-cell superconducting RF(SRF) cavity was designed aiming to be a candidate cavity for high current accelerators. A copper prototype cavity and a niobium cavity were fabricated at SINAP in 2012. In order to ensure these cavities get the desired frequency and a good field flatness higher than 98%, frequency control was implemented in the manufacturing process and pre-tuning has been done using a simple pre-tuning frame based on the bead-pull pre-tuning method. Then, TM010-π mode frequency within 5 kHz from the target frequency was achieved and the field flatness reached 98.9% on the copper prototype cavity. Finally, the same procedure was applied to the niobium cavity to obtain a field flatness better than 98% which benefited the cavity performance in the vertical testing.     

Surface preparation processing for superconducting cavities

Surface preparation is an important processing in production procedures of superconducting niobium cavities,deciding whether the performance of the niobium cavities can meet the specifications. A series of surface preparation methods and relevant apparatuses have been constructed at Shanghai Institute of Applied Physics(SINAP) and the standard procedures of cavity processing were established and successfully applied to different types of cavities. With standard surface preparation procedures on the 500 MHz 5-cell niobium cavity, the cavity accelerating voltage at T = 4.2 K reached 7.5 MV while its quality factor was still higher than 1 × 109.The accelerating gradient of the IMP-HWR010 cavity reached 4.9 MV/m with the quality factor of better than3 × 108 at 4.2 K.     

三次谐波超导腔高次模抑制研究

对上海同步辐射装置中超导三次谐波腔开展了高次模深度抑制研究。分析了上海光源对三次谐波腔高次模的抑制要求,用电磁场计算软件SEAFISH作高次模吸收器长度、安装位置等参数的模拟计算和优化设计,以深度抑制各有害高次模,使高次模的分路阻抗降至能满足束团不稳定性阈值的要求。用ABCI计算得到了谐波腔的高次模功耗理论值。     

Femtocell小区选择问题研究

Femtocell是一种用于下一代移动通信技术的小型化家庭基站,由于其分布的随机性和接入方式的多样性,在Femtocell高密度覆盖的地区可能存在小区选择问题。文中介绍了Femto-cell存在的小区选择问题及相应的解决方案。     

1.5GHz超导加速腔双输入耦合器研究

本实验室设计的1.5 GHz 5-cell超导腔设计工作加速梯度为15-20 MV·m~(-1),至少需要使用两支输入耦合器才能满足高流强运行要求。借助三维电磁仿真模拟软件CST(Computer Simulation Technology),完成了相应的输入耦合器的电磁仿真,驻波比小于1.05的频带宽度达到18 MHz。从理论上计算加速腔双端口功率馈入,并通过铜腔双输入实验进行验证。结果表明,当两端均为欠耦合时,双输入对每个端口耦合度起到增强的作用;但当两者均为过耦合且差异较大时,耦合度小的一端则被减弱,甚至出现欠耦合的情况。对横向力场的计算显示,即使插入深度相差1 mm,使用双输入耦合器所引起的横向作用力仍比使用单耦合器情况小一个量级。