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Optics Measurements, Corrections and Modeling for High-Performance Storage Rings

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6/2-024 - BE Auditorium Meyrin (CERN)

6/2-024 - BE Auditorium Meyrin

CERN

6-2-024
114
Show room on map
Frank Zimmermann (AB/ABP), Massimo Giovannozzi (CERN), Rama Calaga (BNL), Rogelio Tomas (CERN)
Description

The LHC, its luminosity upgrade HL-LHC, its injectors upgrade LIU and other high performance storage rings around the world are facing challenging requirements for optics measurements, correction and modeling. This workshop aims to do a review of the existing techniques to measure and control linear and non-linear optics parameters. The precise optics determination has proven to be a key ingredient to improve the performance of the past and present accelerators.
The goal of the workshop is to assess the limits of the present techniques and evaluate new paths for improvement.
Slides
Secretary: Delphine Rivoiron
  • Monday 20 June
    • Motivation for HE machines, colliders, HI machines, light sources and damping rings

      Guidelines & requests for techniques and instrumentation from the future challenges

      Convener: Jean-Pierre Koutchouk (CERN)
      • 1
        Welcome
        Speaker: Jean-Pierre Koutchouk (CERN)
      • 2
        Collider challenges
        Current and future circular colliders aim at breaking the current luminosity records. This requires the use of elaborated lattice designs, combining innovative accelerator concepts with pushed IR optics. In addition, the particle detectors in the forward scattering region require a very precise control and knowledge of the optics along the interaction region. All these requirements set new challenges in the optics measurements and adjustments. New or upgraded techniques possibly in combination with higher resolution instrumentation should be envisaged for the current and future colliders.
        Speaker: Rogelio Tomas (CERN)
        Slides
      • 3
        Light sources challenges
        The next generation of storage ring based light sources is approaching the diffraction limit in hard X-Ray range of the wavelengths. A factor of ten lower equilibrium horizontal emittance poses substantial challenges to the designers and builders of these rings. Specifications on the building blocks of the rings rely on advanced modeling of not only the non-linear optics but also of the main collective effects that contribute to the blow-up of the emittance. The talk will outline some of the challenges that are being faced by the ultimate storage ring based light source designs as well as by the damping rings designs for the future linear colliders.
        Speaker: Prof. Leonid Rivkin (Paul Scherrer Institute & EPFL)
        Slides
      • 4
        High intensity challenges
        High intensity rings such as those found at the Oak Ridge and J-PARC spallation neutron sources have unique challenges compared to other types of rings. Examples include the importance of low beam loss throughout the entire cycle (including injection); and the effects of fringe fields and magnetic field overlap caused by large aperture, low-aspect-ratio, closely packed magnets. Of course high intensity rings also share many challenges with other types of rings, including collective effects such as instabilities and space charge tune shift, and the need for more accurate simulations. This presentation will discuss the challenges facing high intensity rings, and also suggest areas that could benefit from further development.
        Speaker: Michael Plum
        Slides
    • 10:30
      Coffee Break
    • Experience from colliders, high energy and intensity machines - I
      1. Achieved measurement resolution
      2. Achieved optics quality (initial starting point and final achievement)
      3. Major breakthroughs
      Convener: Oliver Bruning (CERN)
      • 5
        RHIC Experience
        The optics measurement of RHIC polarized protons at 250 GeV with squeezed beta* at IP6 and IP8 showed as large as +-40% horizontal beta beat in the sector between IP6 and IP8. This is a concern for further reducing beta* in RHIC to increase luminosity. Inspired by the success of LHC optics correction, RHIC has the Sector-by-Sector Technique(SBST) installed during 2011 RHIC polarized proton run. The commissioning of this technique was first started in one of the RHIC two accelerators, Blue ring. With a total of about 12 hour beam time, we were able to reduce the high horizontal beta beat in the sector between IP6 and IP8 by a factor of two. Fractional reduction of horizontal beta beat was also observed in other sectors, except the sector between IP4 and IP5. And the vertical beta beat was barely impacted. This talk presents the status of current SBST commissioning in RHIC along with future plan.
        Speaker: Mei Bai (BNL)
        Slides
      • 6
        Tevatron Experience
        The talk will present the experience accumulated in the course of Tevatron Run II on the optics correction and improvement. Both the transfer lines and circular machines are discussed. This work minimized the emittance growth related to ring-to-ring transfers to the level acceptable for collider operation. It also resulted in an acceptance increse required to boost the antiproton production and to minimize beam loss at transfers as well as to optimize operation of each machine and the entire complex.
        Speaker: Mr Valeri Lebedev (FNAL)
        Slides
      • 7
        LHC Experience
        Since the LHC start-up in 2009, numerous optics measurement and correction campaigns were conducted at various energies of the LHC energy cycle. Meticulous local optics corrections for each interaction region, subsequently followed by global corrections enabled to reach a record low beta-beating for hadron colliders below 10% during the squeeze sequence from beta* of 10m to 1.5m. The accurate magnet model, precise field quality specification, careful construction and installation strategy were key for the rapid convergence to be well within optics tolerances. However, the further reduction of beta* by factor 3 to reach the design value at 7 TeV and a much greater reduction of up to a factor 10 for the IR upgrade pose a challenging path to maintain this low beta-beating levels. An overview of the optics performance and the techniques employed at the LHC will be presented together with an outlook to the future.
        Speaker: Glenn Vanbavinckhove (Technische Universiteit Delft)
        Slides
      • 8
        KEKB Experience
        We present optics measurements and corrections in the KEKB commissioning. Beta functions, dispersions, X-Y coupling corrections have been applied to achieve higher luminosity. In addition to the linear optics, chromatic behaviours have been measured and corrected. Chromatic X-Y coupling correction by using skew sextupole magnets helps to increase luminosity by about 20% than before the correction.
        Speaker: Yukiyoshi Ohnishi (KEK)
        Slides
      • 9
        PEPII Experience
        Starting from brief review of driving modified betatron oscillation to show that resonance driving leads to non-modified betatron oscillation, we will review how we made measurement, modeling, and correction of the PEP-II low-energy ring and high-energy ring optics for improving luminosity. We will emphasize on that matching essentially unlimited number of Green’s functions had very much helped PEP-II optics modeling. We may also briefly discuss its implication to model non-modified LHC optics.
        Speaker: Dr Yiton Yan (SLAC)
        Slides
    • 12:45
      Lunch
    • Experience from colliders, high energy & intensity machines - II
      1. Achieved measurement resolution
      2. Achieved optics quality (initial starting point and final achievement)
      3. Major breakthroughs
      Convener: Roland Garoby (CERN)
      • 10
        DAFNE Experience
        DAΦNE, the Frascati lepton collider working at the c.m. energy of the Φ meson resonance (1020), consists of two independent rings. Each one is a quite short structure (~97 m) with many magnetic elements and no periodicity at all and is strongly affected by the detector solenoidal field (∫Bds = 2.4 Tm, to be compared with a magnetic rigidity Bρ = 1.7 Tm). As a consequence the model parameters are far from being independent from each other. The optics model is based on beam measurements, which have been essential in remarking the collider limiting factors as well as in defining the strategy for the upgrades that have been implemented in the last years.
        Speaker: Catia Milardi (INFN - LNF)
        Slides
      • 11
        Linear Optics Measurements by TBT Analysis at Fermilab Booster
        Fermilab Booster accelerate protons from 0.4 to 8 GeV kinetic energy in 33 ms. The analysis of TBT data give a relatively straightforward mean of measuring linear optics and coupling. Results obtained by various analysis method are presented.
        Speaker: Eliana Gianfelice (Fermi National Accelerator Lab. (Fermilab))
        Slides
      • 12
        Experience with low emittance tuning tool for SuperB, Diamond, SLS, and Dafne
        The Low Emittance Tuning (LET) algorithm, developed for the SuperB project, allows to obtain low emittance, correcting simultaneously orbit, dispersion, coupling and beta-beating using correctors and skew quadrupoles. The technique determines an orbit that takes advantage of the passage off axis in sextupoles and quadrupoles lowering emittance of a factor almost ten (in simulations for SuperB) respect to Dispersion Free Steering. BPM tilts are also estimated from the measurements and considered for correction. The technique has been tested at Diamond and at SLS, and is currently under test at Daphne. Preliminary results are presented in this talk
        Speaker: Simone Liuzzo (INFN)
        Slides
      • 13
        HERA experience
        HERA was designed as electron (or positron) - proton collider for maximum energies of 30 GeV for the leptons and 920 GeV for the proton beam. Due to this large difference in beam energy, the machine had to be built as two independent storage rings with common interaction regions at the collision points. As a special feature of the machine, the different characteristics of the lepton and proton beams had to be considered: The electron beam - due to synchrotron radiation strongly determined by its emittance and thus characterized by a flat aspect ratio in the transverse planes, had to be well matched to the “round” proton beam at the two interaction points. In addition, the dynamic influence of the electron mini beta magnets at the interaction region on the proton optics and orbit, as well as the effect of the stray fields of the proton magnets on the electron beam dynamics had to be compensated carefully to establish well defined beam optics during the complete machine cycle and to guarantee matched beam sizes of the electron and proton beam during beam collisions. Starting from very basic measurements of the beta function in the beginning of the HERA runperiod, modern tools have been developed over the years and applied to measure and optimise the optical parameters like beta function, dispersion and effective beam size at the IP. The talk will give an introduction into the lattice of the two HERA storage rings, present an overview about the historical development of the optics measurements and summarise the results.
        Speaker: Bernhard Holzer (Deutsches Elektronen-Synchrotron (DESY)-Unknown-Unknown)
        Slides
    • 15:40
      Coffee Break
    • Experience from light sources and damping rings
      1. Achieved measurement resolution
      2. Achieved optics quality (initial starting point and final achievement)
      3. Major breakthroughs
      Convener: Dr Dieter Einfeld (cells)
      • 14
        LOCO Overview
        The LOCO (Linear Optics from Closed Orbits) algorithm is used to find and correct errors in the linear optics of storage rings. This technique has been used to correct the optics of many storage rings. I will give examples of using LOCO to correct beta functions and dispersion, correct coupling, measure impedance, and correct transport line optics. I will describe constrained fitting, which improves the quality of LOCO fitting results for many storage rings.
        Speaker: James Safranek (SLAC)
        Slides
      • 15
        Linear lattice errors at the ESRF, measurement and correction
        ESRF machine modeling based on beam orbit measurements will be reviewed. Beta beating, coupling and vertical dispersion are corrected from this model. The minimization of the coupling resonance driving terms (RDT) allowed to reduce vertical emittance to record low values for the ESRF. Vertical dispersion then becomes a key parameter for any further reduction of vertical emittance: Its links to closed orbit errors and chromaticity will be discussed.
        Speaker: Dr Thomas Perron (ESRF)
        Slides
      • 16
        SLS Experience
        SLS storage ring optics reaches the state-of-the-art through more than ten years operation as providing high quality synchrotron light to about 20 beam lines. The linear optics has been measured with the response of the tune to small variation of quadrupole strength and corrected based on SVD. The corrected optics allows us to employ the model response matrix for the orbit correction/feedback and the linear coupling correction. The nonlinear optics has been corrected using pre-defined theoretical knobs to surppress relevant resonances. The beam life time can then be sufficiently long. One of the highlights of SLS performance is the small vertical emittance ~2 pm thanks to the well corrected betatron coupling and vertical dispersion with dispersive and non-dispersive skew quadrupoles. Recently, we introduced two more optics measurements, namely LOCO and turn-by-turn BPM. The idea is to compare the results from independent measurements. This resulted in better understanding the machine and we achieved further small vertical emittance <2 pm. Girder re-alignment is also underway to challenge even smaller vertical emittance for future accelerators.
        Speaker: Masamitsu Aiba (Unknown)
        Slides
      • 17
        SOLEIL Experience
        The SOLEIL 2.75 GeV third generation synchrotron light source has been delivering photon beam to users since January 2007. The storage ring optics is based on a DBA lattice, very compact and strongly focusing to accommodate a 3.7 nm.rad horizontal emittance and a 1020 ph/s/mm2/mrad2/0.1*BW brilliance for a 354 m circumference storage ring. As of today 24 beam-lines are provided with a top-up 400 mA electron beam with an orbit stability as low as 300 nm RMS in the vertical plane in the frequency range 0-150 Hz and a beam lifetime greater than 10 h. . To achieve such performance carefully modeling and optimization of the linear and non-linear optics are required. In this talk results will be presented based on beam measurements. Examples of characterization of the non-linear dynamics perturbations driven by insertion devices (22 IDs already installed) will be shown as these latter have complex magnetic fields and may have strong impacts of the facility performance. Standard techniques and their limitations for high performance synchrotron light source will also be discussed.
        Speaker: Laurent Nadolski (SOLEIL)
        Slides
      • 18
        DIAMOND Experience
        The beta beating at the diamond storage ring has been reduced to less than 1% peak-to-peak and the linear coupling to 8e-4 at the source point, providing a vertical emittance of about 2pm. Building upon this excellent control of the linear optics, we have developed various techniques for the calibration of the nonlinear model of the storage ring. Experimental results based on FMA and driving terms analysis show that the calibrated nonlinear model reproduces with very good accuracy the main quantities characterising the nonlinear beam dynamics.
        Speaker: riccardo bartolini (Diamond Light Source and John Adams Institute)
        Slides
  • Tuesday 21 June
    • Techniques review - I
      1. Merits of the different techniques
      2. Do the available techniques match the future challenges?
      3. Could LOCO be applied to the LHC as for light sources?
      Convener: Dr James Safranek (SLAC)
      • 19
        LOCO for LHC
        The LOCO principle is based on measuring orbit corrector responses and fitting numerical models to the measured data. This principle is very well known and successfully applied in many fields. To be prepared for the commissioning of the LHC and its transfer lines, a dedicated software project, Aloha (Another Linear Optics Helper Application), was launched to cover the requirements for the LHC: Aloha is a Java reimplementation of the LOCO principle with many extensions. This software was used extensively during the commissioning of the transfer lines and the LHC injection tests to identify optics errors and to verify corrector- and monitor polarities with circulating beam in the LHC. In this talk, an overview of the used principles will be given, results of several example use cases during LHC commissioning will be presented and the pros and cons of using the LOCO principle in the LHC will be sketched.
        Speaker: Kajetan Fuchsberger
        Slides
      • 20
        Optics Diagnostics with AC Dipoles (CANCELLED)
        An AC dipole is an exciter of a beam bunch for optics measurements based on observation of turn-by-turn orbits with beam position monitors. By driving the bunch with a sinusoidally oscillating dipole magnetic field, whose frequency is close to betatron frequency and amplitude is adiabatically ramped up and down, the AC dipole can produce a sustained large oscillation with almost no emittance growth. Non-destruction nature of the AC dipole is particularly useful for slow cycled hadron rings with no dumping from synchrotron radiation and effectiveness of the AC dipole has been demonstrated in AGS, SPS, RHIC, Tevatron, and LHC. This talk presents a basic concept and operational experience of the AC dipole based optics measurement as well as address statistical and systematic limitation of this method.
        Speaker: Ryoichi Miyamoto (Brookhaven National Laboratory)
      • 21
        Action-Phase analysis
        Action and phase analysis on turn by turn BPM data in the LHC show visible variation of action and phase variables in the LHC interaction regions. Linear optic errors are deduced from these quantities. Local skew quadrupole correctors and quadrupole triplets at each interaction region can be set according to such error estimations. This work show the procedure to establish the relationship between the two of them.
        Speaker: Javier Fernando Cardona (Departamento de Fisica-Universidad Nacional de Colombia)
        Slides
      • 22
        Model-Independent Analysis of Turn-by-Turn BPM Measurements in Storage Rings
        Coherent transverse beam oscillations in the Tevatron were analyzed with the Model-Independent Analysis (MIA) technique. This allowed to obtain the model-independent values of coupled betatron amplitudes, phase advances and dispersion function around the ring from a single kick measurement. In order to solve the MIA mode mixing problem a new criterion of betatron mode independence was proposed. Furthermore, we describe a MIA-based technique to locate vibrating magnets in a storage ring. Also MIA data analysis was applied to the data from LHC dipole kick measurements (at injection optics). In order to identify focusing errors the measurements were compared to the LHC design MAD-X model via calculation of local transport matrix elements and initial Twiss parameters for every pair (or triplet) of BPMs in the LHC. This allowed to obtain beta-functions not only in BPMs but everywhere in several long sections of LHC which are free of large focusing errors.
        Speaker: Alexey Petrenko
        Slides
    • 10:40
      Coffee Break
    • Techniques review - II
      1. Merits of the different techniques
      2. Do the available techniques match the future challenges?
      3. Beta* leveling, blind optimization of non-linear correction
      Convener: Catia Milardi (INFN - LNF)
      • 23
        Refined techniques for phase measurements
        Extracting the phase from signals in beam position monitors is a common operation in accelerator facilities and can be used to reconstruct many optics parameters as well as the impedance distribution in the machine. The main limit in these operations is set by the accuracy of the phase measurement. On this topic we will present a recently developed algorithm, named all-phase FFT (apFFT), which allows reaching better accuracies in the case of simulations or measurements for which the noise level is low. Comparisons with typical FFT and SUSSIX will also be presented as well as an application to the localization of transverse beam coupling impedance sources.
        Speaker: Nicolo Biancacci (Universita di Roma I 'La Sapienza'-Universita e INFN, Roma I)
        Slides
      • 24
        Beta* measurement and adjustment
        Good understanding of Tevatron optics was absolutely essential to maximize the Tevatron luminosity and performance. The talk discusses optics measurements used to build the Tevatron optics model and steps which were required to correct optics. A comparison of optics measurements with the orbit responce and the turn-by-turn measurements is also discussed.
        Speaker: Dr Valeri Lebedev (FNAL)
        Slides
      • 25
        Probing non-linear fields with orbit bumps
        The nonlinear tune response matrix (NTRM) method was developed to diagnose the lattice nonlinear components. It explores a nonlinear tune response to a controlled closed orbit deformation (COD). The details and challenges of the experimental application of the NTRM method are discussed. Status of experimental reconstruction of controlled sextupolar errors and natural sextupolar components of the SIS18 Synchrotron are presented.
        Speaker: Angelina Parfenova (GSI)
        Slides
      • 26
        Chromatic measurements in RHIC and LHC
        In RHIC, the phase advance between the two interaction points is optimized for an initial design beta*. This may not hold true as RHIC presently operates with a considerably reduced beta*. Chromatic optics measurements from RHIC are presented the enlarged beating is evident for reduced beta*. Phase advance changes between the IPs are proposed as a first attempt to reduce the model chromatic beta-beating. Recent measurements are performed to investigate the impact on the single beam lifetime and momentum aperture for the "modified" lattice. Measurements from the LHC are also discussed.
        Speaker: Rama Calaga (BNL)
        Slides
      • 27
        RHIC non-linear chromaticity and IR corrections
        In this talk we will review the measurement, modeling and correction of second order chromaticities, the interaction region multipole errors, and the third order resonance driving term in RHIC. We will focus on second order chromaticity modeling and correction. With a low beta* at IP6 and IP8, the second order chromaticities have to be corrected for successful RF re-bucketing and good beam-beam lifetime at store. We find that the sources of second order chromaticities are mostly localized in the IR6 and IR8. Therefore, it is possible to minimize them by adjusting the betatron phase advances between the two IPs.
        Speaker: Dr Yun Luo
        Slides
    • 12:30
      Lunch
    • Modeling
      1. Is it desirable to converge to one optics code?
      2. Collaborative approach to optics code?
      3. Is on-line modeling really on-line?
      4. Differences between Tevatron and LHC magnet modeling
      Convener: riccardo bartolini (Diamond Light Source and John Adams Institute)
      • 28
        LHC magnet modeling
        We give an overview of the strategy used for the magnetic modeling of the LHC. Magnetic measurements are fit with a set of parametric equations (FiDeL) based on decomposition of the main components of the magnetic field. These equations are impelmented in the LHC control system LSA,which is the tool used to power the magnets. A dedicated code (WISE) creates the input files for tracking codes (MAD), providing the best knowledge of the accelerator field quality. An overiview of the main results of the early phase of LHC beam commissioning and the main critical issues are outlined.
        Speaker: Dr Ezio Todesco (CERN)
        Slides
      • 29
        Optics codes
        For the design and layout of accelerators "Beam-Dynamics" calculations have to be performed in order to show the functionality of the machine and to determine the specifications and requirements of the different accelerator components (vacuum-system, magnets, power supplies, correctors, etc.). For these calculations the so called "Beam-Dynamic-Codes" are used, as for example: MAD, DIMAD, BETA, OPA, AT, TRACY, ELEGANT, ACCELERATICUM. In a collaboration of SLS, SOLEIL, SPEAR III, APS, BINP and ALBA a comparison of these codes has been made for the lattices of SOLEIL, APS and ALBA. In a first step the linear lattice parameters have been calculated and in a second step the nonlinear parameters as tune shifts with energy and amplitude as well the dynamic aperture including energy deviations. Within this seminar the results of this comparison will be presented and discussed.
        Speaker: Dr Dieter Einfeld (CELLS)
        Slides
      • 30
        RHIC online modeling and experience with feedbacks
        The RHIC online model is made of a lattice and energy ramp design used as inputs to two computation servers, RampManager and OptiCalc, each with their own dedicated purpose. In the past, the RHIC energy ramp was based entirely on stepstones to allow for orbit and tune control and beta* squeeze schemes evolving throughout the energy ramp. RampManager loads all required databases, services all incoming requests and calls the corresponding functions. OptiCalc is the optics calculation and matching module which provides also dedicated algorithms for each requested task. In this presentation we first review the various components of both of these servers. Next we show how the online model has evolved to interface with multiple feedback loops now used routinely at RHIC to accelerate, squeeze, and steer the beams into collisions and for periodic orbit control during normal physics stores. Dedicated accelerator physics experiments profit also from these enhanced capabilities; for example controlling these beam properties using feedback while dynamically squeezing the beta-star(s).
        Speaker: Dr Guillaume Robert-Demolaize (BNL)
        Slides
      • 31
        LHC Online Modeling
        The Large Hadron Collider (LHC) at CERN is a particular challenging high energy, superconducting machine with respect to the design as well as to the operation. That requires a sophisticated software environment and a good collaboration of the teams involved to transfer the simulation output for desired beam configurations into the control system, verify and check the control system settings, drive the machine to arrive at the desired configuration and to provide an online simulation of the current status of the machine. To support the operation and the progress of comissioning of the LHC, efforts were recently devoted towards the design and implementation of a software framework aimed to use the computing power of the beam dynamics code MAD-X in the framework of the java-based LHC control and measurement environment. In this talk the basic architecture of the online modeling, existing applications and their usage for operation will be presented.
        Speaker: Gabriel Johannes Mueller (Technische Universitaet Dresden-Unknown-Unknown)
        Slides
      • 32
        Non-linear modeling of accelerators
        Only very recently it became possible to even contemplate about effective non-linear modeling of accelerators, on the other hand modern superconducting require such modeling for proper correction of nonlinear effects. In recent years, one has begun to carefully measure harmonics and misalignments of all magnets of an accelerator and to provide transfer functions for the control system, reliable 1000 turn BPM systems have been made available including appropriate beam exciters, optics codes have reached a new level of sophistication and new analysis tools have been developed for a direct measurement of nonlinear components. In essence, non-linear modeling has become equivalent to linear modeling.
        Speaker: Frank Schmidt (CERN)
        Slides
    • 15:50
      Coffee Break
    • Beam diagnostics
      1. Is current instrumentation adequate for future challenges?
      2. Progress with bunch-by-bunch instrumentation?
      3. How to incorporate detector techniques and data into the accelerator optics model?
      Convener: Dr Jorg Wenninger (CERN)
      • 33
        LHC Instrumentation & future developments
        Speaker: Dr Rhodri Jones (CERN)
        Slides
      • 34
        Light Source Instrumentation
        Third-generation light sources have reached a very mature state of development, with lattice measurement and correction performed routinely at the level of 1% or better. High-resolution beam position monitoring coupled with high-speed data acquisition and processing have made this possible. At x-ray free electron laser facilities such as LCLS, resonant cavity beam position monitors with sub-micron single-shot resolution allow sophisticated beam-based alignment and optics measurement capability. In addition to beam position monitoring, synchrotron light diagnostics provide powerful tools in the determination of emittance, coupling, dispersion, and time structure. An overview of the different diagnostics in use at light sources with an emphasis on application to lattice measurement and correction will be presented.
        Speaker: Glenn Decker (ANL)
        Slides
      • 35
        Roman pots for beam diagnostics
        The physics programme of the TOTEM experiment requires the detection of very forward protons scattered by only a few microradians out of the LHC beams. Therefore, the experiment has inserted stacks of planar Silicon detectors in moveable near-beam telescopes (so called Roman Pots) located along the beam-line on both sides of the interaction point IP5. The precise knowledge of the LHC optics expressed by the beam transport matrices between the interaction point and the detectors’ location is of the key importance for the proton kinematics reconstruction after the collision. The talk will report the optics measurements performed by the TOTEM experiment based on the proton tracks reconstructed in the Roman Pots and will summarize the estimated corrections of the LHC triplets of the IP5 sector for beta*=3.5m fills.
        Speaker: Hubert Niewiadomski (Brunel University)
        Slides
      • 36
        Beam based gain calibration (CANCELLED)
        Good quality beams, for example, extremely low emittance beams or beams with very low emittance ratio, are required in present-day accelerators, in which quite sometimes strong nonlinear optics elements are needed. Since, in such cases, the optics is dependent strongly on beam orbit deviation from the designed orbit, the orbit stabilization is one of essential issues to realize good quality beams. It should be pointed out that a BPM usually detects beam position relative to the electric monitor center, not the geometrical center, and that the electric center likely drifts due to unexpected variation of imbalance, or gains, among the output signals from its electrodes. The imbalance is often introduced by drifts on transfer impedance through cables, connectors, attenuators and switches. This talk proposes a method to calibrate the imbalance by beam measurements and to detect the beam position relative to the stable geometrical monitor center. The talk also covers the demonstration of the method in the KEKB.
        Speaker: Kotaro Satoh (KEK)
  • Wednesday 22 June
    • LHC complex present and future plans
      1. Introduce the planned upgrades and future projects new challenges for optics modeling and beam instrumentation?
      2. Are the optics challenging enough?
      Convener: Dr Massimo Giovannozzi (CERN)
      • 37
        LHC Operations
        The present challenges in terms of measurement, correction and modelling for LHC operations are briefly summarized. There is potential for pushing the performance in the next couple of years - the options and the implications of these for operations are discussed. In the longer term, operational challenges will include the move to higher energy, the potential squeeze to nominal beta* and the push to nominal beam intensity. The demands that these will make on the operational measurement, correction and modelling strategies are outlined.
        Speaker: Mike Lamont (CERN)
        Slides
      • 38
        Machine Development plans at the LHC
        Since spring 2011 regular machine development (MD) periods are scheduled for the LHC. Presently a year of LHC running features about five blocks of 5 days each of dedicated machine studies, which are aimed at calibration and validation, at improving operational procedures, or at preparing for future operation modes as well as for future upgrades. An overview is given of the LHC MDs performed so far, including a few key results, and the future plan is described, with particular emphasis on items related to optics control.
        Speaker: Dr Frank Zimmermann (AB/ABP)
        Slides
      • 39
        HL-LHC project overview
        Speaker: Prof. Lucio Rossi (CERN)
        Slides
      • 40
        The optics challenges of the LHC Upgrade and a novel concept to reach low beta*
        Increasing the integrated performance of the LHC by a factor of 5 to 6, as requested for the exploitation period 2020-2030, cannot only be achieved by playing with one or two parameters in the luminosity formula, but by pushing all of the them at or beyond the limits. Two of them, beta* and/or the beta* aspect ratio can however reduce the requirements, both on the beam parameters and/or on the new technologies needed for the upgrade (e.g. crab-cavity). The reduction of beta*, and a fortiori for a flat optics with a beta* even smaller in one of the two planes, was found however very challenging in the LHC due to very simple reasons: working at more less constant L* unless changing completely the detectors, constant length of the final focus system (the so-called matching section for the LHC insertions) unless “displacing the arcs”, and a priori constant strength budget for the chromatic correction unless changing 500 two-in-one quadrupoles in the lattice. Under these conditions, and applying the classical approach where low-beta insertions with a squeezable optics are interleaved with arcs of machine to transport the beam at constant optics, the minimum possible beta* was found to be about 30 cm. A novel optics scheme called the “Achromatic Telescopic Squeezing (ATS) Scheme has then be worked out in order to reach much lower beta* and bring a touch of realism for the upgrade parameter lists which were proposed so far.
        Speaker: Stephane Fartoukh (CERN)
        Slides
    • 10:30
      Coffee Break
    • Prospects and future developments
      1. Introduce the planned upgrades and future projects new challenges for optics modeling and beam instrumentation?
      2. Are the optics challenging enough?
      Convener: Prof. Lucio Rossi (CERN)
      • 41
        LHC Injectors Upgrade project overview
        The LHC Injectors Upgrade (LIU) project is in charge of making the CERN accelerator complex capable of reliably providing the beam required by the high luminosity LHC until at least 2030. Except for Linac4 which is already in construction, the baseline solution is to upgrade the existing accelerators, PS Booster, PS and SPS. The project is presently in a study phase, the objective being to finalize the implementation of the upgrades during the second long LHC shutdown, probably in 2018. The present limitations of the different accelerators will be described, as well as the improvements under consideration.
        Speaker: Roland Garoby (CERN)
        Slides
      • 42
        Low gamma-t optics in the SPS
        In order to increase the bunch current instability thresholds that limit the LHC bunch intensities in the SPS, several optics were proposed targeting the reduction of the transition energy. In particular, a simple solution by decreasing the integer tunes of the actual working point by 6 units was developed and applied to the real machine, enabling the injection and acceleration up to the flat top of single bunches with 3-fold increase in the intensity, within the nominal LHC-type beam sizes. This talk will review the measurements performed in the SPS for exploring the features of this optics with respect to the nominal ones. Particular emphasis will be given on studies undertaken in order to build and compare a non-linear machine model for the different optics.
        Speaker: Yannis Papaphilippou (CERN)
        Slides
      • 43
        FAIR project and optics challenges
        Beam loss control is an important issue in all superconducting accelerators. In the FAIR project the requirement of beam loss control becomes demanding by the complications created from the high intensity. The response of the beam to the linear and nonlinear machine optics is magnified by the space charge. Issues of optics and resonance control (compensation) during storage and acceleration becomes essential for machine performance. In this talk these issues are addressed.
        Speaker: Dr Giuliano Franchetti (GSI)
        Slides
      • 44
        SuperB project overview
        The SuperB project for an asymmetric e+e- collider at the Y(4S) energy has been recently approved by the Italian Government. The Collider will be built in Italy, but will profit of the work by a large international collaboration. The design is based on the "large Piwinski angle and crab waist" collision scheme already successfully tested at the DAFNE Phi-Factory at Frascati Labs. This talk will review the basic SuperB design principles and the status of R&D.
        Speaker: Marica Biagini (INFN)
        Slides
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