Design and Experience with the Ws/hs Assembly Movement Using Labview Vis, National Instrument Motion Controllers, and Compumotor Electronic Drive Units and Motors

The Low-Energy Demonstration Accelerator (LEDA), designed and built at the Los Alamos National Laboratory, is part of the Accelerator Production of Tritium (APT) program and provides a platform for measuring high-power proton beam-halo formation. The technique used for measuring the beam halo employs nine combination Wire Scanner and Halo Scraper (WS/HS) devices. This paper will focus on the experience gained in the use of National Instrument (NI) LabVIEW VIs and motion controllers, and Compumotor electronic drive units and motors. The base configuration couples a Compumotor motor driven by a Parker-Hannifin Gemini GT Drive unit. The drive unit is controlled by a NI PXI7344 controller card, which in turn is controlled by a PC running custom built NI LabVIEW VIs. The function of the control VI’s is to interpret instructions from the main control system, the Experimental Physics and Industrial Control System (EPICS), and carry out the corresponding motion commands. The main control VI has to run all nineteen WS/HS motor axes used in the accelerator. A basic discussion of the main accelerator control system, EPICs which is hosted on a VXI platform, and its interface with the PC based LabVIEW motion control software will be included. 1 BEAM CONFIGURATION A 52-quadrupole-magnet lattice at LEDA is used to study the formation of high-power proton-beam halo formation. Essential to this study are a series of wire scanner and halo scraper devices (collectively known as WS/HS). These devices are designed to measure the beam’s transverse distribution. By generating intentional lattice mismatches, it is possible to view halo formation at downstream WS/HS [1, 2]. The first WS/HS is located just after the fourth quadrupole magnet in the halo lattice and benchmarks the beam produced by the RFQ. This benchmark is used as a nominal input to the halo lattice. A set of four WS/HSs are located approximately halfway through the lattice. These provide phase-space information after the beam has debunched. The final set of four WS/HSs are located near the end of the halo lattice and are used to measure beam halo there. These are used to measure beam halo at a location very sensitive to halo formation. The wire scanner portion of the WS/HS is used to produce a cross-sectional or transverse distribution of the beam core. The halo scraper consists of two graphitescraping devices (one for each side of the distribution)[3] to acquire the tails of the beam distribution. Both the wire and scraper for a given transverse axis, either horizontal or vertical, are mounted on a single assembly and thus positioned by a single motion control unit (MCU). The present paper will only concern itself with controlling a single MCU. Figure 1: Electronics Setup for Three Axes Each MCU comprises the mechanism needed to move one axis, either horizontal or vertical, at one longitudinal location in the halo lattice. A unit is comprised of a Compumotor motor driven by a Parker-Hannifin Gemini GT Drive unit. See Figure 1 for the basic layout for three of the nineteen axes. The drive unit is controlled by one channel of a four-channel National Instruments (NI) PXI7344 motion control card sitting in a NI PXI chassis. The PXI chassis is mapped to a PC via a NI MXI-3 interface mounted in a PCI slot in the PC. The PC runs a NI LabVIEW Virtual Instrument (VI). A VI is similar to a computer program, but runs in NI’s LabVIEW graphical programming environment. The PC is in charge of all motion control for all WS/HS axes. There are a total of ten wire scanners while only nine WS/HSs. The * Supported by US DOE, Office of Defense Programs, and the Office of Nuclear Energy, Science and Technology 0-7803-7191-7/01/$10.00 ©2001 IEEE. 794 Proceedings of the 2001 Particle Accelerator Conference, Chicago