A software application programme has been developed to allow fast and automatic high-gradient conditioning of accelerating structures at 30 GHz in CTF3. The specificity of the application is the ability to control the high-power electron beam which produces the 30 GHz RF power used to condition the accelerating structures. The programme permits operation round the clock with minimum manpower requirements. In this paper the fast control system, machine control system, logging system, graphical user control interface and logging data visualization are described. An outline of the conditioning control system itself and of the feedback controlling peak power and pulse length is given. The software allows different types of conditioning strategies to be programme

Dubrovskiy, A

Rodríguez, José Alberto

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CERN-AB-2008-05908Sep2008AN AUTOMATIC CONTROL SYSTEM FOR CONDITIONING 30 GHzACCELERATING STRUCTURESA software application programme has been developed to allow fast and automatic high-gradientconditioning of accelerating structures at 30 GHz in CTF3. The specificity of the application is the abilityto control the high-power electron beam which produces the 30 GHz RF power used to condition theaccelerating structures. The programme permits operation round the clock with minimum manpowerrequirements. In this paper the fast control system, machine control system, logging system, graphical usercontrol interface and logging data visualization are described. An outline of the conditioning control systemitself and of the feedback controlling peak power and pulse length is given. The software allows differenttypes of conditioning strategies to be programmed.EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHCERN   -   AB DepartmentGeneva, SwitzerlandAugust 2008AbstractCERN-AB-2008-059CLIC-Note -7431)  JINR, Dubna, Russia & CERNA. Dubrovskiy1) ,  J. A. RodriguezCERN, Geneva, SwitzerlandPresented atEPAC'08, 11th European Particle Accelerator Conference, Genoa, Italy - June 23-27, 2008AN      AUTOMATIC        CONTROL       SYSTEM       FOR         CONDITIONING     30 GHz ACCELERATING          STRUCTURES                                                 Dubrovskiy Alexey∗, (CERN, Geneva, Switzerland; JINR, Dubna, Russia)Jose Alberto Rodriguez† , (CERN, Geneva, Switzerland)AbstractA software application programme has been developedto allow fast and automatic high-gradient conditioning ofaccelerating structures at 30 GHz in CTF3. The specificityof the application is the ability to control the high-powerelectron beam which produces the 30 GHz RF power usedto condition the accelerating structures. The programmepermits operation round the clock with minimum man-power requirements. In this paper the fast control sys-tem, machine control system, logging system, graphicaluser control interface and logging data visualization are de-scribed. An outline of the conditioning control system it-self and of the feedback controlling peak power and pulselength is given. The software allows different types of con-ditioning strategies to be programmed.INTRODUCTIONCTF3 is a test facility where the feasibility of the CLIC(Compact Linear Collider) must be demonstrated [1]. Oneof the key issues is to develop an accelerating structurewhich should work at an accelerating gradient above 100MV/m, a pulse length of more 200 ns and a break downrate (BDR) less then 10−7. The 30 GHz power produc-tion system was installed in CTF3 [2] in order to investi-gate properties of accelerating structures. Results obtainedfor different structure designs and structure power require-ments are summarised in [3, 4].The machine layout for the conditioning is shown inFig.1. The linac generates a 3 GHz electron beam with anaverage current of up to 5A and a bunch length of 1 mm.Then 5 high power klystrons accelerate the beam, beforeit passes through the PETS (power extraction and transferstructure). Extracted 30 GHz RF is fed to the test-standthrough a 30 GHz low loss waveguide. A variable splitteris used to direct part of the RF power to the acceleratingstructure and the other to a dummy load. The RF splitterallows a variable power with constant beam conditions. Anaccelerating structure is placed in the accelerating struc-ture tank. Hardware and software interlocks, such as highvacuum levels, klystron trips, gun instability etc., have tobe continuously monitored and permanently controlled. Incase of a critical situation for a part of machine, the gun isautomatically turned off. It is only possible to turn it backon when everything has been restored back to normal.∗Alexey.Dubrovskiy@cern.ch, alex@solf.ru† on leave, Jose.Alberto.Rodriguez@gmail.comG u nP E T S  T a n kC T F 3C T F 2A t t e n u a t o r L o a dA c c e l e r a t i n g  s t r u c t u r e  t a n kL o a dK l y s t r o n sV a c u u m  g a u g eF a r r d a y  C u pR e f l e c t e d  p o w e rI n c i d e n t  p o w e rT r a n s m i t t e d  p o w e rFigure 1: The machine layout.CONDITIONING SYSTEMA few words about conditioning processes of a systemin general. The initial step is to define an appropriate listof conditions on the system. If over some period the exper-iment satisfies the requirements, one can analyse acquireddata and draw a conclusion about characteristics of the sys-tem. Acquisition, control, feed-back and feed-forward sys-tems help to adjust the experiment in accordance with theconditions (Fig. 2). Conditions themselves are defined byexperts. The control parts and conditions of the structureconditioning are described below.Figure 2: The conditioning system.The acquisition system of the 30 GHz conditioning con-sists of the incident, the transmitted and the reflected RFpower waveforms, a faraday-cup and a BPM signal, vac-uum levels and machine interlocks (Fig. 1). The powerprofiles are presented as I/Q signals [5]. The power sig-nals and faraday-cup signal are acquired pulse-to-pulse ata repetition rate up to 15 Hz and at a 1 GHz sampling rate.Calculations of the acquisition peak power and the pulselength are done using the incident power waveform.The control system consists of the gun pulse length con-trol, switching on and off the gun, resetting interlocksand the attenuation control. The gun pulse length controlchanges the pulse length of incoming RF into a structure.And the attenuator allows to control the incident power asdescribed in the introduction.The computer architecture is shown in Fig. 3. The condi-tioning controlling server is responsible for all control op-eration and all acquisition calculations which are relatedto the conditioning process. Also two fast channel ADCswere installed on a compact PC containing eight channelsin total. Configuration and control of the scopes and thechannels are served by OASIS software [6]. Communica-tions between device servers are provided by the softwarecommunication infrastructure for the controls MiddlewareCMW/RDA [7]. The automatic conditioning software waswritten by using FESA framework [8].L o g g i n g  s y s t e m sG r a p h i c a l  U s e r  I n t e r f a c e s W E Bs e r v e rI n t e r n e tT e x t  f i l e s M a t - f i l e s O r a c l eV a c u u m  l e v e l  r e a d i n gI n t e r l o c k  c o n t r o l l e r sS t e p p i n g  m o t o r  c o n t r o l l e rC o n d i t i o n i n g  c o n t r o l l i n g  s e r v e rG u n  t i m i n g  c o n t r o l l e rN e t w o r kI QI  s i gna lQ  s i g n a lI n c i d e n t p o w e rI QT r a n s m i t t e d     p o w e rI QR e f l e c t e d  p o w e rF a r a d a y - c u p      s igna lB P M  s i g n a lFigure 3: The computer architecture.CONDITIONING ALGORITHMA range of various structure conditioning procedureswere investigated before the automatisation was started.The conditioning software is an expert control application,which has been taking shape iteratively improving detailsbased on the results of the tests themselves. The presentconditioning logic (Fig. 4) consists of conditions on thethree following types:1. Safe machine operation, which is determined by ma-chine interlocks.2. Incoming RF properties: conditioning strategy andconditioning interlocks.3. Experiment description: events and pulse summarylogging.The machine interlocks serve to detect abnormal be-haviour in the machine and based on them, switch the ma-chine into a safe mode. For the 30 GHz conditioning thereare several crucial interlocks:• Gun inhibit interlock is an indicator for the e− gunthat it is allowed to produce bunches. This interlockis dependent on the status of the gun, klystrons, RFcomponents, personal safety components etc.M o d eS t a t u s  o f  d e v i c e sO NS e t  s a f e  m o d eE r r o rI n t e r l o c kO KS a v e  i n t e r l o c k  i n f oY E SS w i t c h  o f f  g u n ,  c h a n g e  p u l s e  l e n g t h  a n d  a t t e n u a t i o nS a v e  e v e n t  i n f o  a n dp u l s e  s u m m a r yC h a n g e  p u l s e  l e n g t ha n d  p e a k  p o w e rR e s e t  i n t e r l o c k sS w i t c h  o n  g u nN OFigure 4: The conditioning logic• Vacuum interlocks. In the RF path there are 5 relevantvacuum gauges: the pets tank, the first bend, the sec-ond bend, the third bend and the accelerating structuretank gauges (Fig. 1). They are all monitored to ensurethat the conditioning operates at a low vacuum level.The 30 GHz conditioning interlocks indicate an unex-pected behaviour of a tested structure or a breakdown.• FC interlock - the faraday-cup interlock is activatedif the peak of faraday-cup signal exceeds a certainthreshold. It’s the most used indicator of breakdown.• Reflected energy interlock is activated if the peak ofreflected accelerating structure energy is above a cer-tain threshold. This threshold is a percentage of theincident power.• Missing energy interlock was implemented to measurethe power absorption by accelerating structures. Miss-ing energy is the incident energy minus the transmit-ted and reflected energy.When an interlock is activated, the gun is switched off andthe conditioning program reduces the pulse length and thepeak power. After that the program waits for a predefinedtime in order to gather all interlock information and allowthe structure time to recover. And then it switches the gunon.The conditioning strategy is specified by specialists inorder to raise the gradient in the structure without damag-ing it. All these procedures can be describe in the followingway. An operator defines a target map consisting of pairs ofpulse length and peak power points. According to that map,the program attempts to sequentially reach each target. Thetarget is reached if the current gun pulse length and attenu-ator position exceeds the target values. At first the programincreases the peak power, after which it increases the pulselength. The time and number of steps to move from one tar-get to another are specified. Due to the machine instability,the peak power and the pulse length vary slowly. A stabil-isation feedback based on an exponential moving averageand on fuzzy discrete control was implemented. It turnson if the conditioning reaches the last target or if the peakpower or the pulse length exceed the feedback stabilisationtarget.Figure 5: Pulse shapes of an event and events configuration.The experiment logging consists of 3 parts: pulse sum-mary, events and settings. For every pulse the programcomputes cardinal characteristics. For power signals theyare the peak power, the energy and the pulse length. Forthe BPM and faraday-cup signals they are the total chargeand the peak of the current. Also the missing energy, the re-flected energy, the accelerating gradient and the breakdownindicator are stored. In case of an event the software storesall power and signal waveforms, vacuum levels, interlocks,the attenuator position and the gun pulse length for the lastpulse and the two precedent pulses (Fig. 5).CONDITIONING SOFTWAREA fast control system, a GUI (Graphical User Inter-face), a logging system and a web-site were developed andevolved into a complex software system (Fig. 6). Thefast control system is entrusted with the fast, stable andlong-term conditioning process and with publishing dataequipped with a time stamp. The logging system storesdata in flat MAT- and TXT- files on local hard disks. FilesF a s t  c o n d i t i o n i n g  c o n t r o l  s y s t e mC + + , F E S AL o g g i n g  s y s t e m sM A T - f i l e s ,  T X T - f i l e sL o g g i n g  s y s t e mi n t o  O R A C L E  D BJ A V A  W E B - s e r v i c eh t t p : / / c e r n . c h / p r o j e c t - c l i c - r f c o n d 3 0G U IJ A V AFigure 6: 30 GHz conditioning software infrastructureare synchronised with a conditioning data depository. TheGUI provides configuration visual forms, acquisition datadisplays, logging histograms and an alert-system (Fig. 7).The latter detects problems during operation and informsan operator. The GUI application was written in JAVA us-ing JAPC, jdataviewer and other CERN java components[9]. The report-logging system sends summarised data oversome period into the ORACLE data base. The web-servicepublishes web-pages about the current conditioning statusand main characteristics, logging for the last tree days andhistory for all experiments [10].Figure 7: GUI screen shot of an acquisition panel.REFERENCES[1] CERN. The Compact Linear Collider Study.http://cern.ch/CLIC-Study.[2] C. Achard, H. H. Braun, G. Carron, R. Corsini, A. Grudiev,S. Heikkinen, D. Schulte, J. Sladen, I. Syratchev, F. Tecker,I. Wilson, and W. Wuensch. 30 ghz power production inctf3. 2005. Particle Accelerator Conference, Knoxville,Tennessee.[3] W. Wuensch, C. Achard, S. Doebert, H. H. Braun,I. Syratchev, M. Taborelli, and I. Wilson. A demonstrationof high-gradient acceleration. 2003. Particle AcceleratorConference.[4] Jose Alberto Rodriguez. 30 ghz high-gradient acceleratingstructure test results. PAC, 2007.[5] Raquel Fandos. Rf acquisition system for clic high gradienttesting. In HG2006, http://indico.cern.ch, September 2006.CERN, INDICO.[6] CERN/AB-CO. OASIS. http://cern.ch/project-oasis.[7] CERN/AB-CO-IN. CMW. http://cern.ch/CMW.[8] CERN/AB-CO-FC. FESA. http://cern.ch/project-fesa.[9] CERN/AB-CO-AP. AB/CO/AP software development page.http://cern.ch/ab-dep-co-ap.[10] CERN/AB-RF. 30 GHz conditioning home page.http://cern.ch/project-clic-rfcond30.

An Automatic Control System for Conditioning 30 GHz Accelerating Structures

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