The active alignment system is capable of positioning accelerator components of CLIC (Compact Linear Collider) with a precision of a few microns. An electronic processing and command system connects the micro-movers and sensors of this system to the CERN-PS complex control system

Benedetti, M

Carrica, D

Coosemans, Williame

Pittin, R

CERN Document Server

OPEN-99-00115/06/98CERN - European Laboratory for Particle PhysicsC L I C  I CLIC Note 361Active Alignment Electronic System for CLIC 30 GHz Modules in CTF2D. Carrica*, R. Pittin, W. Coosemans, M. Benedetti*AbstractThe active alignment system is capable of  positioning  acceleratorcomponents of CLIC (Compact Linear Collider) with a precision of afew microns. An electronic processing and command system connectsthe micro-movers and sensors of this system to the CERN-PS complexcontrol system.*D. Carrica, Professor; M. Benedetti, Professor & Head Quarter,University of Mar del Plata, ArgentineGeneva, Switzerland15 June 1998CLIC Note No 361An electronic processing and command system for the active alignmentof the CLIC 30 GHz modules in CTF2D.Carrica, R. Pittin, W. Coosemans, M.BenedettiAbstractThe active alignment system is capable of  positioning  accelerator components of CLIC (CompactLinear Collider) with a precision of a few microns. An electronic processing and command system connectsthe micro-movers and sensors of this system to the CERN-PS complex control system.IntroductionCERN is studying the feasibility of building a linear collider (CLIC) to obtain electron-positroncollisions. The total energy reached in the collisions should be in the TeV range. The CLIC scheme isbased on beam acceleration at high gradient (150MV/m) and high frequency (30 GHz) with RF powergeneration by the Two Beam Acceleration (TBA) method. Pulsed microwave power is extracted from theDRIVE linac by means of power extracting structures and fed into the PROBE linac through waveguidefeeders.To demonstrate the feasibility of the CLIC scheme a test facility (CTF 2) with 30 GHz modulesresembling as closely as possible the real CLIC design has been constructed. As in CLIC, the accelerating, correction and beam detection components of the 30GHz CTF2 modulesmust be aligned to an accuracy <10 µm.  The alignment system used consisting of supports, positionsensors and actuators results from developments and tests on two models built for the purpose in thealignment test facility.   A 30 GHz module for CTF2 consists of two girders, one per linac, supporting accelerating or powerextracting  structures and beam position monitors. An assembly of quadrupoles sit above each girder onindependent supports.  CTF2 will require two modules for phase 1.Supports and displacement systemThe accelerating or power extracting  cavities and the beam position monitors sit on girders onpre-aligned vees.  The girders are supported by inter-girder articulation supports. This support fixed at therear of a girder has two micromovers with link rods for the vertical movement, one micromover with linkrod and a screw stop for the horizontal movement and two link rods to support and adjust the front of thenext girder. The distance between two articulation points is 1.41m. The quadrupoles sit on a rectifiedmetallic plate supported by three micromovers with link rods for the vertical, and two micromovers withlink rods and a screw stop for the horizontal movements.The micromovers of an inter-girder articulation and the micromovers of the nearest quadrupoles sitprecisely on a metallic plate. This plate is aligned and fixed on a concrete block which is integrated intothe floor. There is one concrete block for two modules.Alignment: Method and sensorsThe alignment system has two principal functions. The first is to pre-align the elements so that the beamcam pass through the aperture and produce  signals in beam position monitors. These signals are then usedto move the girders and the quadrupoles for making the definitive alignment. The second function is tomaintain the elements in this position.The Wire Positioning System (WPS) is used to position the girders and the quadrupole supports.  Thereference for each linac is a wire under tension. The spatial position of the wires is fixed by four referencesystems, one at each extremity of the two modules. The reference systems combine an HydrostaticLevelling System (HLS) and a WPS which are put in their theoretical place by geometrical measurementfrom the local survey network. The inter-girder articulations and the extremities of the quadrupolesupports are fitted with WPSs which are precisely located with respect to the axes of the acceleratorcomponents. The sensors measure the distance between the sensor axis and the wire in two directions, onevertical and the other horizontal perpendicular to the accelerator axis. An accelero-tiltmeter is alsorequired on each girder and each quadrupole support to measure the transverse tilt and the vibrations ofthe supports.Main characteristics of the instrumentsGirder• Silicon-carbide• Length with extremity plates : 1.40 m• Cross section : 0.6 x 0.12 m• Side thickness : 7.5 mm• Module of elasticity : 2100 daN/mm²• Density : 2.65 g/cm³• Thermal expansion : 4.8 x 10-6• Very good thermal conductivity• weight : ~ 12 Kg• Tolerance for adjustment of the vees and             the extremity support plates  < 5 µmWire• Carbon + aramid fiber (Kevelar)• Apparent diameter: 0.50 mm• Weight of 100m : 20 gr + 16 gr• Elastic limit: ~ 300 N• Mass of counterweight used : 6 KgWire Positioning System (WPS)• Two axes• Measurement range : ± 5mm• Resolution: 0.1 µm• Repeatability: 1 µm• Bandwidth: 0-10 HzMicromover• Stepwise motorisation• Length at mid course : 155 mm• Diameter : 60 mm• Travel : ± 4 mm• Resolution : 0.2 µm• Repeatability : 1 µm• Maximum load along the thrust axis : 400 NElectronicsNew developmentThis system, which is now being fabricated, will provide: increased alignment precision, higherprocessing speed, simultaneous and synchronised displacements, decreased equipment volume, reducedcost and easier and more flexible use. Version 1 processing was executed by the CPU of the VMEcontroller whereas it is done by local units in version 2.These local units consist of VME Alignment Main Control Card (AMCC) modules operating in slavemode. Each AMCC module contains two DSPs (Digital Signal Processors), one dedicated to motormovement control and the other to the alignment control algorithms, acquisition control andcommunication with VME bus. Logical circuits and volatile memory are contained in two Logic CellArrays (LCA). The DSP clock rate is 40 MHz.Each motor driver circuit can manage up to 6 motors. There are 5 motor driver circuits in each 3UEurope crate. Two daisy-chain optical fibers connect the driver crates to the AMCC. Asynchronouscommunication is used in order to avoid problems caused by delays in optical fiber transmission.Analog signals are captured using 16 bit acquisition systems with 14 or 20 differential channel. Extracare has been taken to ensure that the 16 bit A/D’s precision is not degraded by crosstalk with themultiplexing (MPX). The acquisition systems communicate with the AMCC via 2 additional optical fibers.There are 102 actuators and 164 sensor signals involved in the system. Two AMCCs control all motorsand sensor signals with an average response time of 1 ms. The decentralised processing of this systemallows the number of elements to be increased up to 64 groups of 6 motors and up to 62 acquisition groups(14 or 20 channels per group) without degrading the response time. Communication by optical fibbersensures high precision and immunity to electronic noise.Hydrostatic Leveling System  (HLS)• Measurement range : 5 mm• Resolution : 0.2 µm• Repeatability : 1.2  µm• Separate external electronicsTilt Meter System   (TMS)• The instrument measures the tiltand the acceleration in two axes• Resolution : 10-7 radian• Repeatability : 10-6 radian• Bandwith : 0 to 100 Hz• Measurement range : ± 3.10-3 radianHardware Architecture3     The application program, which is available in the “Console Manager” of any Operation workstation, isbuilt around a full screen graphic representation of the two 30 GHz modules and their components. Directinteraction on this picture allows individual control of active equipment by knob widgets. This is completedby “normal operation facilities” like starting or stopping the alignment process for a beam or introducingmanual offset position corrections for each girder or quadrupole.VME BusXILINXData Ramcontent: 51216bit-wordsAddress &Control BusData BusXilinx forlogical controlsDSP DSPFPGFPGMain DSPOptical fiber15 MbaudsSENSORS MOTORSElectronicsfor sensorsA/D MPXConverter14 Bit (≥20)A/D MPXConverter 16bit (14channels)Electronicsfor sensorsMotor drive5 slots6 chan.eachMotor drive5 slots6 chan.eachDriver FinalMotorCapability to acquire 82 sensorsaccording to the memory map andlogical program. of XILINXCapability to control 51 motors accordingto the memory map and logical program ofXILINX130130ConclusionThe system is now operational and it has been successfully operated for the first time with a beam in CTF2.In closed loop in respect with the wire we maintain continuously the elements in a < 5 micron window . Nextyear we install two new modules with the new electronic control system. In addition of the strong integrationand performances described below, we hope to be able to test the possibilities of the alignment control systemfor the CLIC machine.References• W. Coosemans, H. Mainaud. « Pre-Alignement of CLIC using the Double-Wire method », CERNjanvier 1997.• Clic Study Group. « CTF2 Design Report », CERN CLIC Note 304, June 1996• Clic Study Group. «The CERN Linear Collider », CERN CLIC note 195, May 1993• R.Rausch, Ch.Serre (editors). “Common Control System for the CERN Accelerators”, ICALEPCS1991, TSUKUBA, JAPAN (11-15 November 1991) page 54• WEB CERN PS Controls Home Page : http://psas01.cern.ch/

Active Alignment Electronic System for CLIC 30 GHz Modules in CTF2

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