低频率低β低温氮掺杂HWR超导腔的性能测试

Performance Test of Low β 162.5 MHz Nitrogen Infused HWR Cavity

  • 摘要: 中国原子能科学研究院和北京大学联合提出的北京在线同位素分离丰中子束流装置(BISOL)的强流氘驱动加速器采用半波长谐振(HWR)超导腔作为主要加速结构,加速能量为3~40 MeV的强流氘离子。为此,北京大学设计并研究了可加速50 mA 氘束的β=0.09、频率为162.5 MHz HWR超导腔。本文介绍该腔的设计、加工、表面处理及低温射频性能测试,并研究将低温氮掺杂这种新的表面处理方法用于该腔,进行低温超导性能测试。实验结果表明,采用圆锥形(taper)结构的HWR超导腔在2 K温度下达17 MV/m的高加速梯度。通过低温氮掺杂后,HWR超导腔在2 K、10 MV/m下的品质因数Q0提升了1倍,表明HWR超导腔有高加速梯度高品质因数的优点。

     

    Abstract: Beijing isotope-separation-on-line neutron rich beam facility (BISOL) for both basic science and application is a project proposed by China Institute of Atomic Energy and Peking University. The intense deuteron driver accelerator (IDD) of BISOL would adopt superconducting half wave resonator (HWR) with low β and high current. A β=0.09 HWR cavity was developed in Peking University which has the ability to accelerate deuteron beam with current of 50 mA even for IDD future update. The design, fabrication, surface treatment and low temperature RF performance test results of HWR cavity were presented in this paper. A surface treatment of low temperature nitrogen infusion was applied to this cavity to study the effect of nitrogen infusion on low frequency low β cavity. The results show that this tapered shape HWR cavity reaches high accelerating gradient of 17 MV/m at 2 K. After low temperature infusion, the quality factor Q0 almost doubles when the gradient is 10 MV/m at 2 K.

     

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