[ sono rs/its `.`DR. 3A?\lIZATION ron NucLEAR RESEARCH

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1 [ sono rs/its `.`DR. 3A?\lIZATION ron NucLEAR RESEARCH ilcmwii CERN - PS DIVISION CERN LIBRARIES, GE A NEV CERN/PS (RF) L,,. ; to av 23 P0OO24»46O DIGITAL BEAM CONTROLS FOR SYNCHROTRONS AND STORAGE RINGS IN THE CERN PS COMPLEX F. Blas, ]. Boucheron, B.]. Evans, R. Garoby, G.C. Schneider, ].P. Terrier, ].L. Vallet Abstract New beam control systems have been designed for the acceleration of lead ions in the PS complex. The standard selected satisfies the medium term needs of all six synchrotrons and storage rings in the PS division, for the minimum cost. Special care has been taken to preserve the beam gymnastics capability that characterises the PS machine. Digital technology is used where it is considered to bring decisive advantages over more traditional analogue techniques. Full scale tests of these beam control systems have been done with protons during the LHC injectors test run in December Concept, design and practical experience are reported. Paper presented at the 1994 European Particle Accelerator Conference june 27 ]u1y 1, 1994, London, United Kingdom Geneva, Switzerland 4/7/94 OCR Output

2 Digital Beam Controls for Synchrotrons and Storage Rings in the CERN PS Complex F. Blas, J. Boucheron, B.J. Evans, R. Garoby, G.C. Schneider, J.P. Terrier, J.L. Vallet CERN-PS CH Geneva 23 Abstract New beam control systems have been designed for the DIGITAL acceleration of lead ions in the PS complex. The standard 1..0 selected satisfies the medium term needs of all six synchrotrons and storage rings in the PS division, for the minimum cost. Special care has been taken to preserve the beam gymnastics capability that characterises the PS machine. Digital technology is used where it is considered to bring decisive advantages over more uaditional analogue techniques. Full scale tests of these beam control systems have been done with protons during the LHC injectors test run in December Concept, design and practical experience are reponed. 1. INTRODUCTION DDS: DLP: Direct Dig. Sgthesizer Dtal Looesso DAU: DFP: igiop er 7 Digital Ari hmetic Unit I I ' "" Dig. Frequency Program Decimal....[ Imsplay nt.? <I> -LLDC. As part of the lead ion acceleration project at CERN [1], a an. 5]/ R.F. Fnqudncy major development is required to equip the 4-ring PS Booster with adequate beam conu ols. These needs add to the DAU 0, ; I it u;re1i requirements for filling the LHC [2] and for maximum compatibility with the already installed equipment in the six zi.. Revolution Frequency "" T zg T Lc synchrotrons of the PS complex. ih DFP Freq. correction A A Direct digital synthesis is the obvious choice for the RF - rl mk u hue LO: Local Oscillator source, based upon the experience gathered on its use in our M l ~ el machines since 1980, and on its ease of use with modem tts:. lzégraisttzz Rate 0,,, L, integrated circuits. Consequently, only digital technology is rmt. used in the cascade of modules generating the open loop RF... tr. ANALOGUE sine wave from real-time measurement of the B Held. Standard RF techniques are applied for the processing of beam and cavity retum signals. A high speed ADC (12 10 Ms/s) makes the link between the phase loop analogue correction Figure 1. Generic beam control system. signal and the digital frequency modulation input. 2.2 Built-in facilities provide easy means to correct the Analogue functions frequency programme and to change the harmonic number. The beam and cavity retum signals are translated to a fixed Special care is taken to ensure and to verify error-free data intermediate frequency of 10.7 MHz using standard super uansmission between modules. heterodyne techniques. Commercially available FM receiver components are used when possible. A phase-locked loop 2. SYsrEM generates the local oscillator signal at fm: MHz. Global electrical characteristics of the processing chain are 2.1. Description given in Table 1. A generic beam control system was first designed including Table l all the capabilities needed in the PS synchronous complex. Characteristics of RF analogue processing (Figure 1). A construction standard was selected based on NIM mechanics and front panel coaxial connectors of Lemo OO 0.4 to 10 MHz type. No radial loop is represented as the digitally generated Input level 0.1 mv to 1 V frequency is sufficiently accurate to cenue the beam in the IF band-width 200 khz vacuum chamber. Correction signals can be entered into the summing node of the beam phase loop, to implement other Signal/Noise at 0.1 mv pp 23 db input level (2 khz bw functions, e.g. synchronization to an extemal source. Overall delay for phase < 5 its demodulation OCR Output DDS RF sine wave l I IE -{CAvITY{ pu Mix II Mj.X&I AVC I I AVC phase 2 Vpp MHZ Disc. PLA

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4 OCR OutputInternal logic gates the injection of the error signal, and triggers an auto-zero process during dead times. 1 RF Output for bunch lengthening and the 9th harmonic cavity for 40 MHz T'I L >ECL controlled blow-up, and (2) in the PS to provide both harmonic 8 and 16 for bunch splitting and acceleration. new hardware performed reliably in all these uses, and DDS Q 2220 (Qualcomm) 'I`he FREQ4 2; contributed in a decisive way to the success of the test [4, 5]. x4 Other applications are being treated, like the beam controls for lead ion acceleration in the PSB and the upgrade of existing 23 $ R.F. Frequency systems in the PS. The number of modules built is now greater than 200. lg ->]1.Ar c1 t s FILTER] (Low-Pass / fc:l5 MHZ) DAC AD 9720 (Analog Devices) The analogue input signal is convened by a 12-bitADC, and scaled to the beam revolution frequency using the harmonic number applied in the "Leam" phase and the setting 3.4 Direct Digital Synthesizer (DDS) (Figure 5) of the DLP gain. The resulting digital word is stored in memory when in "Leam mode. A commercial integrated circuit (Qualcomm Q2220) implements the direct digital synthesis technique [3]. I`he RF 4. Exr>EruENcE AND FOREcAsr sine wave is obtained by digital-to analoguc conversion of its 10-bit oumut. The distributed 10 MHz clock is multiplied by 4.1 U1C injectors test and other applications 4 to provide the intemal clock required for the generation of New low level RF systems for the PSB and for the PS sine waves up to 14 MHz. were built for the needs of the LHC injectors test at the end of 1993, using the new standard modules and based on the generic beam control" described in section 2.1. The "main harmonic numbu was l in the PSB (0.6 to 1.8 MHz) and 16 in the PS (- 7.6 MHz). Additional capabilities were implemented (1) in the PSB to drive the 2nd harmonic cavity Figure 5. Direct Digital Synthesizer. 4.2 Future evolution 3.5 Digitizing Recorder (DR) The present frontier between analogue and digital technologies was dictated by the limitation in resources. The The DR (Figure 6) has 2 modes of operation. In the intention is to evolve in the direction of digital technology, mode (beam phase loop "on"), it records the error but in progressive steps, when clear advantages can be signal fed into the DLP, at a memory address given by the B expected, and at a rhythm governed by the means available. train counter. Nothing is sent to the DAU. In the "Replay" An obvious first candidate for such an evolution is the mode, the recorded data are sent into the frequency correction synchronization loop, where flexibility in the implementation input of the DAU. With beam phase loop "oft", and for the of non linear transfer functions is very important and where same magnetic conditions, beam position in the vacuum digital technology can drastically reduce the amount of chamber is the same in "Replay mode as it was when the hardware. Promising results have already been obtained, using Leam" mode was triggered. developments done for the low level RF of SSC injectors [6]. [1] D. Warner (editor), "CERN Heavy-Ion Facility Design 16 Frequency Report", CERN tcorrec ion Lean / Replay [2] The LHC Study Group, "Design Study of the Large Hadron Collider (LHC)", CERN DAC[ > Monitoring [3] S. Tumer (editor), "RF Engineering for Particle Accelerators" (CAS), CERN 92-03, pp [4] R. Cappi, R. Garoby, M. Martini, J.P. Ritmaud, K. Schindl, "The PS as LHC Proton Source: Results of t.he Two-week 1 22 i ;?; ; )? T Engg] km K X it bt; u ADC fl 7 ssétigrigss " 1 <=)Gain Control UP-DOWN 1/H COUNTER (H as for DAU) T B Ewdom Longitudinal Density in a Proton Synchrotron", These Analogue input Figure 6. Digitizing Recorder MH lc? 5. R12r=12ru;NcEs Beam Test in December 93", These Proceedings. [5] R. Garoby, S. Hancock, "New Teclmiques for Tailoring Proceedings. [6} l...k. Meshta, V. Brouk, R.C. Webber, I. Mangino, T. Uher, "A Digital Beam Phase Loop for the Low Energy Booster" Proceedings of the 1993 Particle Accelerator Conference, May 1993, pp OCR Output

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