LCABD Collaboration: Work Package 5: Crab Cavity

LCABD 协作：工作包 5：蟹腔

• 批准号: PP/E002625/1
• 负责人: Amos Dexter
• 金额: $ 40.76万
• 依托单位: Lancaster University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=PP%2FE002625%2F1
• 关键词: LCABD; Collaboration; Work; Package; Crab

The most flexible designs of the international linear collider (ILC) beam delivery system in terms of operating parameters, typically have a crossing angle between the electron and positron beamlines greater than about 14 mrad so that electron and positron bunches do not pass through each other's final focusing quadrupole doublets thereby assisting the extraction of spent beams after collision. The baseline option has two interaction points with crossing angles of 20mrad and 2mrad. An alternative option has one crossing angle of 14 mrad. The angle between the electron and positron bunches at the interaction point will cause a luminosity loss unless corrected by an appropriate rotation. The rotation of these bunches is to be performed using two crab cavity systems. A crab cavity is a transverse deflecting RF cavity operated with a 90 degrees phase shift. The development of a crab cavity system is a critical R&D requirement for ILC large crossing angle schemes. The UK has taken a lead role in initial studies to define the type of system that will most readily fit current layouts for the ILC beam delivery system (BDS) and that will meet Global Design Effort (GDE) specifications. A current project has established that the best fit to the ILC crab cavity requirement is to develop a derivative of the CKM 3.9 GHz superconducting cavity. RF phase tolerances for the operation of the cavity have been established. The crab cavity system development now requires optimisation of the superconducting RF dipole cavity, such that its Higher Order Mode (HOM), Lower Order Mode (LOM) and Same Order Mode (SOM) components are sufficiently damped so as to eliminate any unwanted wakefield interaction with the ILC beams. Coupling out this power from the cavity and cryomodule requires development of appropriate coupler and absorber solutions. Microphonics instabilities in the SRF cavity/cryomodule can also deteriorate RF system performance. To mitigate such effects detailed mechanical and thermal analysisis required. Amplitude stability of the crab cavity systems must be better than one part in 10,000 and the relative phase error between the electron and positron crab cavity systems must not be more than 0.07 degrees at 3.9 GHz. To reach this demanding specification it is anticipated that advanced control techiques built on state of the art digital digital processing must be employed and research is needed to push the limit on what is currently achieveable. The high power 3.9 GHz RF system must be characterised in terms of its amplitude and phase stability and subsequent integration with the crab LLRF control system. The entire system needs to be fabricated, tested on a beamline and operation proven in preparation for the Technical Design report of the GDE due in 2010.

在操作参数方面，国际线性撞机（ILC）梁传递系统的最灵活设计通常在电子和正电子束线之间具有大于14 mrad的电子和正电子束线之间的交叉角度，因此电子和正电子束不会通过彼此的最终焦点四倍的双倍双倍侧乘，从而辅助了后面的碰撞型钻孔的提取。基线选项具有两个相互作用点，其交叉角度为20Mrad和2Mrad。另一种选择的一个交叉角度为14 mrad。除非通过适当的旋转校正，否则电子和正电子束之间的角度将导致亮度损失。这些束的旋转将使用两个蟹腔系统进行。螃蟹腔是一个横向偏转的RF腔，以90度的相移操作。螃蟹腔系统的发展是ILC大交叉角度方案的关键研发要求。英国在初步研究中发挥了领导作用，以定义最容易适合ILC束输送系统（BDS）的当前布局的系统类型，并符合全球设计工作（GDE）规格。当前的一个项目已经确定，对ILC螃蟹腔需求的最佳拟合是开发CKM 3.9 GHz超导腔的衍生物。已建立了腔室操作的RF相公差。现在，螃蟹腔系统的开发需要优化超导型RF偶极子腔，以使其高阶模式（HOM），较低阶模式（LOM）和相同的订单模式（SOM）组件得到充分减弱，以消除与ILC束相互作用的任何不需要的Wakefield的相互作用。从腔和冷冻模块中耦合这种功率需要开发适当的耦合器和吸收剂溶液。 SRF腔/冷冻模块中的麦克相应不稳定性也会导致RF系统性能恶化。为了减轻此类效果，需要详细的机械和热分析。螃蟹腔系统的振幅稳定性必须比10,000中的一个部分更好，并且电子和正电子蟹腔系统之间的相对相误差必须在3.9 GHz时不得超过0.07度。为了达到这一苛刻的规范，预计必须采用基于最先进的数字处理状态的高级控制技术，并且需要进行研究以促进目前可实现的限制。高功率3.9 GHz RF系统必须以其幅度和相位稳定性以及随后与Crab LLRF控制系统的整合来表征。整个系统需要进行制造，在光束线上进行测试并经过经过证明的操作，以准备2010年GDE的技术设计报告。