STFC/RAL/ASTeC, Chilton, Didcot, Oxon
Royal Holloway, University of London, Surrey
STFC/RAL/ISIS, Chilton, Didcot, Oxon
The front end test stand FETS is an R&D project hosted at Rutherford Appleton Laboratory RAL with its aim to demonstrate a high power, fast chopped H- ion beam and will consist in final stage of ion source, low energy beam transport LEBT, RFQ and a transport line including a chopper system at 3MeV output energy. Possible candidates of applications are Isis upgrade (RAL neutron source), future spallation sources or the Neutrino factory. The high beam power may cause problems due to its thermal power deposition on diagnostics parts introduced into the beam so non-interceptive beam instruments are highly preferred to avoid those problems. Diagnostics for H- beams can benefit of laser light where photons with suitable energy are able to detach the additional electron. This method is applied to a beam profile monitor close to the ion source of the FETS beam line and the paper gives a status report of the ongoing process of commissioning and provides a detailed discussion of problems and recent changes including first "proof-of-principle" measurements.
STFC/RAL/ISIS, Chilton, Didcot, Oxon
The gas ionisation beam profile monitor is a well established piece of diagnostic hardware. The use of active devices such as micro-channel plates (MCP’s) and channeltrons within such a diagnostic can present problems with gain differences between channels. At the Rutherford Appleton laboratory we have produced a beam profile monitor that uses an array of 40 individually powered channeltrons; these devices were chosen over the MCP for their robustness and longer lifetimes. These channeltron devices (like MCP’s across their surface) can suffer from large variations in gain at the desired operating voltage. We have successfully shown that an additional in-built calibration system using a single, motorised , channeltron can overcome these issues. We report on the work to build the calibration system, and the 40 channeltron array. The PXI (National Instruments) system used to control the motor drive and provide the all data acquisition is also covered. Also we report the new high voltage drift field to reduce space charge effects on the beam profile. Ongoing work on understanding how the drift field as well the beam field affects the measured profile is also discussed.
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
This study evaluates a technique for the closed-loop position and velocity control of a wire scanner actuator. The focus of this technique is to drive a stepper motor-driven actuator through a 1-mm move using a combination of velocity feedback control and position feedback control. More specifically, the velocity feedback control will be utilized to provide a smooth motion as the controller drives the actuator through a pre-planned motion profile. Once the controller has positioned the actuator within a certain distance of the target position, the controller will transition to position-based feedback control, bringing the actuator to its target position and completing the move. Position and velocity data is presented detailing how the actuator performed relative to its commanded movement. Finally, the layout of, and algorithms employed by the wire scanner control system are presented.
GSI, Darmstadt
To avoid beam losses of intense beams stored at the GSI heavy ion synchrotron SIS-18 a precise tune measurement during a whole acceleration cycle is required. This contribution presents a sensitive method of tune determination using data of Beam Position Monitor (BPM) measured in bunch-by-bunch manner. The signals induced in the BPM electrodes were digitized by 125 MS/s and integrated for each individual bunch. The tune was determined by Fourier transformation of the position data for typically 512 subsequent turns. Coherent betatron oscillations were excited with bandwidth-limited white noise. The presented method allows for tune measurements with satisfactory signal-to-noise ratio already at relatively low beam excitation i.e. without a significant increase of transverse beam emittance. In parallel the evolution of transverse beam emittance was monitored by means of Ionization Profile Monitor. The system for online tune measurement is an integral part of the new digital BPM System, presently under commissioning.
BNL, Upton, Long Island, New York
Slow variations of the RHIC closed orbit have been strongly influenced by diurnal variations. These variations affect the reproducibility of RHIC operation and might have contributed to proton beam polarization degradation during past polarized proton runs. We have developed and commissioned a slow orbit feedback system in RHIC Run-10 to diminish these variations and improve energy ramp commissioning and tuning efficiency. This orbit feedback uses multiple dipole correctors and orbit data from an existing beam position monitor system. The precision of the orbit feedback system has resulted directly from application of an improved algorithm for measurement of the average orbit, from improved survey offsets and various measures taken to ensure deterministic delivery of the BPM data. Closed orbit corrections are calculated with an online model-based SVD algorithm, and applied by a control loop operating at up to 1 Hz rate. We report on the feedback design and implementation, and commissioning and operational experience in RHIC Run-10.
JLAB, Newport News, Virginia
The advent of the energy recovering linac (ERL) brings with it the promise of linac-quality beams generated with near storage ring efficiency. This potential will not, however, be fulfilled without overcoming a number of technical and operational challenges. We will review the basics of ERL dynamics and operation, and give examples of idiosyncratic ERL behavior and requirements posing particular challenges from the perspective of diagnostics and instrumentation. Beam performance parameters anticipated in next-generation ERLs will be discussed, and a “wish list” for the instrumentation of these machines presented.
