STATUS OF THE RAL FRONT END TEST STAND
The Front End Test Stand (FETS) under construction at RAL is a demonstrator for front end systems of a future high power proton linac. Possible applications include a linac upgrade for the ISIS spallation neutron source, new future neutron sources, accelerator driven sub-critical systems, a neutrino factory etc. Designed to deliver a 60mA H-minus beam at 3MeV with a 10% duty factor, FETS consists of a high brightness ion source, magnetic low energy beam transport (LEBT), 4-vane 324MHz radio frequency quadrupole, medium energy beam transport (MEBT) containing a high speed beam chopper plus comprehensive diagnostics. This paper describes the current status of the project and future plans.
Proposal for continuation of the Front End Test Stand
i Executive summary High power proton accelerators (HPPAs) are at the heart of many future large-scale scientific facilities such as a spallation-neutron source, Neutrino Factory and the Muon Collider, high energy physics at the energy or intensity frontier, accelerator driven sub-critical systems, and the transmutation of nuclear waste. Controlling beam-loss induced machine activation during injection into a circular accelerator (synchrotron or FFAG) is essential for safe operation of HPPAs and requires the beam in the injector linac to be chopped very precisely at the synchrotron revolution frequency. The Front End Test Stand (FETS) at RAL has as its primary aim to demonstrate perfect chopping of a high quality, high intensity, negative Hydrogen ion beam at an energy of 3 MeV. Although primarily a hardware construction project, the FETS collaboration has become an efficient mechanism for sharing the wealth of real-world accelerator expertise within ISIS and the ASTeC Intense Beams Group with the wider academic community as well as benefitting from the specialisations and expertise of the university groups. The work already undertaken has contributed to the UK's continuing international reputation as a centre of excellence and has stimulated collaborations with leading international accelerator institutes such as CERN, FNAL, ESS and CNS. FETS consists of a high-brightness Penning surface plasma negative-hydrogen-ion source, magnetic Low Energy Beam Transport (LEBT) at 65 keV to match the beam into a 3 MeV Radio Frequency Quadrupole (RFQ) operating at 324 MHz which delivers the 60mA beam to the Medium Energy Beam Transport (MEBT) where the chopping systems are situated. Comprehensive, state-of-the-art diagnostics measure the performance of the system and the beam quality. The ion source, LEBT and high power RF systems have been commissioned and the manufacture of the RFQ is underway. With this proposal we seek the resources to complete the construction of FETS in a timely manner. This will entail:  The installation, testing and commissioning of the RFQ;  Accelerating the desired beam intensity and beam quality through the RFQ;  The completion of the engineering design and the manufacture of the chopper systems;  The installation, testing and commissioning the MEBT and chopper systems;  The transmission of beam through the MEBT and the demonstration of precise and efficient beam chopping; and  Evaluating the performance of the complete test stand. In addition, we proposed to evaluate the additional benefits that will accrue from exploiting the FETS as a driver for …
Dimensional Errors of Fixtures, Locating and Measurement Datum Features in the Stream of Variation Modeling in Machining
Machining processes are usually multi-station processes involving a large number of operations and several locating datum changes. Machining errors are thus introduced, transformed and accumulated as the workpiece is being machined. This paper introduces procedures for expressing the influence of errors in fixtures, locating datum features and measurement datum features on dimensional errors in machining. These procedures are essential in the derivation of the Stream of Variation model of dimensional machining errors using the CAD/CAPP parameters of the machining process. The linear state space form of the Stream of Variation model allows for advanced control theory achievements to be employed in formal solutions to problems in multi-station machining. Modeling procedures presented in this paper were experimentally verified in machining of an automotive cylinder head.