Vacuum System Optimization for EAST Neutral Beam Injector

The neutral beam injector (NBI) generates a high-energy ion beam and neutralizes it, and then relies on drift transmission to inject the formed neutral beam into the fusion plasma to increase the plasma temperature and drive the plasma current. In order to better cooperate with the Experimental Advanced Superconductive Tokamak (EAST), part of the Chinese major national scientific and technological infrastructure, in carrying out long-pulse high-parameter physics experiments of 400 s and above, this paper considers the optimization of the current design and operation of the NBI beam line with a pulse width of 100 s. Based on an upgraded and optimized NBI vacuum chamber and the structure of the beam-line components, the gas-source characteristics under the layout design of the NBI system are analyzed and an NBI vacuum system that meets relevant needs is designed. Using Molflow software to simulate the transport process of gas molecules in the vacuum chamber, the pressure gradient in the vacuum chamber and the heat-load distribution of the low-temperature condensation surface are obtained. The results show that when the NBI system is dynamically balanced, the pressure of each vacuum chamber section is lower than the set value, thus meeting the performance requirements for the NBI vacuum system and providing a basis for subsequent implementation of the NBI vacuum system upgrade using engineering.

Redesigning the Jefferson Lab Hall A beam line for high precision parity experiments

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. 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 raster shape with this arrangement so a sixth quadrupole was installed downstream of the Moller polarimeter to provide an additional degree of freedome. All of the parity experiments in Hall A have been run with this still-unsatisfactory configuration. The MOLLER experiment is predicated on achieving a 2% error on a 32 ppb asymmetry. Beam line changes are required to meet the systematic error budget. This paper documents the existing beam line, an interim change which can be accomplished during a annual maintenance down, and the final configuration for MOLLER and subsequent experiments.

Strap-On Magnets: A Framework for Rapid Prototyping of Magnets and Beam Lines

We describe a framework to assemble permanent-magnet cubes in 3D-printed frames to construct dipole, quadrupole, and solenoid magnets, whose field, in the absence of iron, can be calculated analytically in three spatial dimensions. Rotating closely spaced dipoles and quadrupoles in opposite directions allows us to adjust the integrated strength of a multipole. The contributions of unwanted harmonics were calculated and found to be moderate. We then combined multiple magnets to construct beam-line modules: a chicane, a triplet cell, and a solenoid focusing system.

SINDRUM II

In 1987 a collaboration including ETHZ - UZH - PSI - RWTH Aachen - Univ.,Tbilisi proposed a new search for \mu eμe conversion in muonic atoms. The SINDRUM II spectrometer came into operation in the \muμE1 area in 1989, but a dedicated beam line was delayed until 1998 by technical setbacks.

A novel method to improve the spatial resolution of GEM neutron detectors with a stopping layer

This paper proposes a novel method to improve the spatial resolution of ceramic GEM detectors by adding a stopping layer on top of the solid ¹⁰B4C neutron converter. This will restrict the emission of the secondary ion products of large angles and consequently improve the spatial resolution. The Monte Carlo program FLUKA is used to validate the method, and the verification experiments are carried out at the beam line #20 (BL20) of the China Spallation Neutron Source (CSNS). The experimental results are approximately in agreement with the simulations. The measured spatial resolution is 1.61 mm for the GEM neutron detector operated at ambient pressure with a 1-μm-thick ¹⁰B4C converter, and it is improved to ~0.8 mm by coating a 3-μm-thick titanium on top of the ¹⁰B4C converter.<br><br>

A novel method to improve the spatial resolution of GEM neutron detectors with a stopping layer

This paper proposes a novel method to improve the spatial resolution of ceramic GEM detectors by adding a stopping layer on top of the solid ¹⁰B4C neutron converter. This will restrict the emission of the secondary ion products of large angles and consequently improve the spatial resolution. The Monte Carlo program FLUKA is used to validate the method, and the verification experiments are carried out at the beam line #20 (BL20) of the China Spallation Neutron Source (CSNS). The experimental results are approximately in agreement with the simulations. The measured spatial resolution is 1.61 mm for the GEM neutron detector operated at ambient pressure with a 1-μm-thick ¹⁰B4C converter, and it is improved to ~0.8 mm by coating a 3-μm-thick titanium on top of the ¹⁰B4C converter.<br><br>

An Ion Source’s View of Its Plasma

Modeling of ion beam extraction from an ECRIS requires special procedures in order to achieve results similar to what is found experimentally. The initial plasma conditions must be included for consistency between experiment and simulation. Space charge forces and their compensation of the extracted ion beam become important with increasing beam intensity. Here we consider the various beam-plasma conditions that occur along any beam line.