Fabrication of a Short-Period Nb3Sn Superconducting Undulator
Fabrication of a Short-Period Nb3Sn Superconducting Undulator
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短周期 Nb3Sn 超导波荡器的制造
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发表时间：
2008
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通讯作者：
D. Dietderich
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作者：
D. Dietderich
IEEE应用超导学报，第17卷，第2期，2007年6月，第1243-1246页。短周期铌锡超导波荡器的研制。放大图片创作者：J. Prestemon，Paul T. Pipersky，Nate L.作者：Liggins，Hugh C. Higley，Steve Marks，and Ross D.劳伦斯伯克利国家实验室开发用于HEP应用的高场Nb 3 Sn磁体。在过去的几年中，这方面的经验已扩展到设计和制造的波荡器磁铁。一些波荡器应用需要可在存在来自射束的热负载的情况下操作的装置。与NbTi器件相比，Nb 3 Sn的使用允许器件在略微更高的温度（5- 8 K）和更高的Jc下操作，而不需要更大的磁隙。设计了一个由6个周期（12个线圈组）组成的14.5 mm周期的半波荡器装置，并进行了缠绕、反应、灌封和测试。在4次淬火中达到了717 A的短样品电流极限。股线的非Cu J c超过7，600 A/mm 2，淬火时的Cu电流密度超过8，000 A/mm 2。磁场模型表明，如果一个完整的设备制造相同的参数，可以获得1.1 T和1.6 T的极间隙为8毫米和6毫米，分别束场。超导波荡器-铌锡索引项I.超导波荡器（SCU）具有实现具有增强的亮度和拓宽的能量范围的新一代插入装置的潜力，代表了对现有辐射源的显著改进。最有前途的（尽管是激进的）技术是基于Nb 3Sn超导体.研发传真：510-486- 5310;电子邮件：drdietderich@lbl.gov）与来自其他光源的研究人员的讨论确定图像电流加热可能严重限制SCU的性能[4]。Nb 3 Sn的相对较高的临界温度（Tc）用于减轻与镜像电流加热幅度和磁体低温系统性能的不确定性相关的风险，而不需要对磁隙产生不利影响的中间衬垫，从而限制最终性能。LBNL的研发工作已经产生了3个原型设备。第一个器件的周期为30 mm，专注于基本的制造细节和磁体保护[5]。第二个是14.5 mm器械，包括基于第一个器械经验的许多设计修改/改进[6]。第二个器件的一个关键特征是实现了NbTi微调线圈，为未来器件的相位误差校正提供场扰动。正如模型所预期的那样，调整线圈在所有场水平上实现了>1%的中心场扰动。该测试表明扰动幅度足以为未来设备中的主动相位误差校正提供机制。前两个装置的性能表明，它们在某些情况下受到磁不稳定性的限制，在另一些情况下受到机械干扰的限制。图1的两个可能的起源。铌锡SCU样机及其部件的主要截面.主线圈分为三个部分：轭部分位于两个独立的不锈钢端块部分的中间，提供机械支撑并实现Nb 3 Sn到NbTi的拼接。
IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY, VOL. 17, NO. 2, JUNE 2007 , pp 1243-1246. Fabrication of a Short-Period Nb 3 Sn Superconducting Undulator Daniel R. Dietderich, Arno Godeke, Soren O. Prestemon, Paul T. Pipersky , Nate L. Liggins, Hugh C. Higley, Steve Marks, and Ross D. Schlueter Abstract— Lawrence Berkeley National Laboratory develops high-field Nb 3 Sn magnets for HEP applications. In the past few years, this experience has been extended to the design and fabrication of undulator magnets. Some undulator applications require devices that can operate in the presence of a heat load from a beam. The use of Nb 3 Sn permits operation of a device at both a marginally higher temperature (5-8K) and a higher J c , compared to NbTi devices, without requiring a larger magnetic gap. A half-undulator device consisting of 6 periods (12 coil packs) of 14.5 mm period was designed, wound, reacted, potted and tested. It reached the short sample current limit of 717A in 4 quenches. The non-Cu J c of the strand was over 7,600 A/mm 2 and the Cu current density at quench was over 8,000 A/mm 2 . Magnetic field models show that if a complete device was fabricated with the same parameters one could obtain beam fields of 1.1 T and 1.6 T for pole gaps of 8 mm and 6 mm, respectively. Index Terms— Nb 3 Sn, Superconducting Undulator I. I NTRODUCTION Superconducting undulators (SCU’s) have the potential to enable a new generation of insertion devices with enhanced brightness and broadened energy range, representing significant improvements over existing radiation sources. The most promising (though aggressive) technology is based on Nb 3 Sn superconductors. An RD fax: 510-486- 5310; e-mail: drdietderich@lbl.gov) discussions with researchers from fellow light sources determined that image current heating may severely limit the performance of SCU’s [4]. The relatively high critical temperature (T c ) of Nb 3 Sn serves to mitigate the risks associated with uncertainties in the magnitude of the image current heating and in the performance of the magnets' cryogenic system without the need for an intermediate liner that adversely affects the magnetic gap, limiting ultimate performance. The R&D effort at LBNL has resulted in 3 prototype devices. The first device, with a 30 mm period, concentrated on basic fabrication details and magnet protection [5]. The second, a 14.5 mm device, included a number of design modifications/improvements based on experience from the first device [6]. A key feature of the second device was the implementation of NbTi trim coils to provide field perturbations for phase error correction on future devices. The trim coils achieved center-field perturbations of >1% at all field levels, as anticipated by models. The test demonstrated perturbation amplitude sufficient to provide a mechanism for active phase- error correction in future devices. The performance of the first two devices indicated that they were limited in some cases by magnetic instabilities and in others by mechanical disturbances. Two possible origins for Fig. 1. Main sections of the Nb 3 Sn SCU prototype and its components. The main coil is separated into its three sections: the yoke section in the middle of two independent stainless steel end block sections, which provide mechanical support and enable the Nb 3 Sn to NbTi splice.