ORNL, Oak Ridge, Tennessee
The Spallation Neutron Source accelerator systems are designed to deliver a 1.0 GeV, 1.4 MW proton beam to a liquid mercury target for neutron scattering research. The accelerator complex consists of an H- injector, capable of producing one-ms-long pulses at 60 Hz repetition rate with 38 mA peak current; a 1 GeV linear accelerator; an accumulator ring; and associated transport lines. The accelerator systems are equipped with a variety of beam diagnostics, which played important roles during beam commissioning. They are used for accelerator tuning and monitoring beam status during production runs. This talk will give an overview of our experience with the major SNS beam diagnostics systems.
ORNL, Oak Ridge, Tennessee
A new Target Imaging System (TIS) has been installed to directly measure the size and position of the proton beam on the Spallation Neutron Source (SNS) mercury target. The proton beam passing through a luminescent coating on the target nose produces light that is transported via a radiation-tolerant optical system to an image acquisition system integrated with the accelerator controls network. This paper describes the software that acquires and analyzes the image, the integration of the system with the SNS control system, and a comparison of the TIS results with the indirect methods of calculating the peak densities of the proton beam.
LANL, Los Alamos, New Mexico
The Accelerator Operations & Technology Division operates a half-mile linear particle accelerator which utilizes 110 wire scanning diagnostics devices to gain position and intensity information of the proton beam. In the upcoming LANSCE improvements, 51 of these wire scanners are to be replaced with a new design, up-to-date technology and off-the-shelf components. This document outlines the requirements for the mechanical design of the LANSCE wire scanner and presents the design currently being worked on. Additionally, it presents the decision making process for the selected components and sub-systems within the wire scanner such as the drive system, frame, mounting interface, and vacuum components. This is done by comparing design alternatives and comparing them to the objectives of the project. Similarly, a comparison between the use of a stepper motor and a servo motor is detailed in this document; this is mostly done through motor-torque calculations, back-drive calculations, and a comparison of the inherent properties of both types of motors, such as detent torque and torque capabilities. Lastly, the paper concludes with a plan for future work on the wire scanner development.
LANL, Los Alamos, New Mexico
The primary goal of this newly installed beam profile measurement is to provide the facility operators and physicists with a reliable horizontal and vertical projected beam distribution and location with respect to the proton beam target and beam aperture. During a 3000-hour annual run cycle, 5 microcoulombs of charge is delivered every 50 milliseconds through this harp to the downstream 1L target. The resulting radioactive annual dose near this harp is at least 600 MRads. Because of this harsh environment, the new harp design has been further optimized for robustness. For example, compared to an earlier design, this harp has half of the sensing wires and utilizes only a single bias plane. The sensing fibers consist of a 0.078-mm diameter SiC fiber. To hold these fibers to a rigid ceramic structure, a “collet” fiber-clamping device accomplishes the three goals of maintaining a mechanical fiber clamp, holding the sense fiber under a slight tensile force, and providing a sensing fiber electrical connection. This paper describes the harp analysis and design, and provides fabrication, assembly, and installation information, and shows how facility wiring was altered.
ORNL, Oak Ridge, Tennessee
Recent improvements to the next generation beam loss monitor analog front end used on the SNS accelerator have proved successful. Particularly in the removal of incident EMI noise sources and the reduction of RF cavity X-Rays and non beam related "loss" signals. The prototype system under development allows the users to view true beam loss integrated as part of the machine protect system. Sucessful measurements of activation during non-beam times have also been made. This paper is an overview of the improved electronics and the results of the ongoing checkout and verification of this system.
ORNL, Oak Ridge, Tennessee
Beam Loss Monitors are common devices used in hadron and lepton accelerators. Depending on accelerator specifics, BLMs could be just diagnostics or could play an essential role in the Machine Protection System (MPS). This tutorial discusses different types of BLMs and their applicability to different accelerators. It covers traditional BLMs like ionization chambers and scintillator-based devices, and also less common techniques like those based on fiber optics and avalanche diodes. The tutorial gives an overview of the underlying physics involved in beam loss detection, and recent advances in computer simulation of particle interaction with matter helpful for BLM modeling. Options for signal processing electronics are described, as well as interfaces to both the control system and the MPS.