A novel concept for producing polarized positrons at Jefferson Lab using the CEBAF polarized electron photo-injector is presented. This approach relies on the polarization transfer from low energy highly polarized electrons to positrons via bremsstrahlung followed by pair production in a conversion target. An experiment to test this concept is discussed on the basis of GEANT4 simulations. It is shown that this low energy approach, which benefits from recent advances in high current high polarization electron sources, can yield positron longitudinal polarization up to 40%.
A Relational Database Model for Managing Accelerator Control System Software At Jefferson Lab
Thomas Jefferson国家加速器设施的运营软件团队面临着许多挑战，这些挑战与管理大量内部开发软件的设施相同。开发人员包括软件组成员、操作员、硬件工程师和加速器物理学家。一个管理问题是确保所有软件都有一个确定的维护人员，他仍然在实验室工作。在某些情况下，定位“孤儿”软件的源代码也被证明是困难的。其他挑战包括执行版本和文档的最低标准，将测试软件与操作软件隔离，鼓励更好的代码重用，整合输入/输出文件存储和管理，以及跟踪软件依赖关系。本文将描述一个关系数据库模型，用于跟踪解决上述问题所需的信息。该数据库模型的实例化为各种提高生产力和一致性的工具提供了基础，这些工具用于自动化（或至少辅助）软件的构建、版本控制、文档编制和安装。
Jefferson Lab began a plasma processing program start-ing in the spring of 2019. Plasma processing is a common technique for removing hydrocarbons from surfaces, which increases the work function and reduces the sec-ondary emission coefficient. Unlike helium processing which relies on ion bombardment of the field emitters, plasma processing uses free oxygen produced in the plasma to break down the hydrocarbons on the surface of the cavity. The residuals of the hydrocarbons in the form of water, carbon monoxide and carbon dioxide are re-moved from the cryomodule as part of the process gas flow.…
The Continuous Electron Beam Accelerator Facility (CEBAF) and associated experimental equipment at Jefferson Lab comprise a unique facility for experimental nuclear physics. This facility is presently being upgraded, which will enable a new experimental program with substantial discovery potential to address important topics in nuclear, hadronic, and electroweak physics. Further in the future, it is envisioned that the Laboratory will evolve into an electron-ion colliding beam facility.
The Continuous Electron Beam Accelerator Facility (CEBAF) was built with a thermionic electron source and the three original experimental hall lines reflected this. A few years after beam delivery began a parity violation experiment was approved and two polarimeters were installed in the Hall A beam line without consultation with the accelerator physics group. The beam raster system was placed after the new Compton polarimeter, before one accelerator quadrupole and four quadrupoles in the new Moller polarimeter. It was very difficult to meet experimental requirements on envelope functions and …
Precise and accurate measurements of the beam energy delivered to the experimental halls at the Thomas Jefferson Accelerator Facility (Jefferson Lab) is required by many experiments for proper data analysis and physics event reconstruction. During the 6 GeV era of Jefferson Lab, the energy delivered to experimental Hall A was determined to 2E-4 dE/E with multiple measurements; but after the machine was upgraded to 12 GeV, the accelerator's beam energy calculations needed to be re-calibrated. In order to link the 6 GeV era calibrations to the 12 GeV era, the Hall A ARC energy measurement system…
