International Linear Collider Damping Ring Research and Development Projects

1. Strawperson list of design and engineering tasks for the ILC damping rings, as a starting point for discussion. (Current draft: 15 December 2005. Thanks to Andy Wolski for generating this.)

2. At our meeting at CERN in November we had discussed the possibility of creating a global R&D plan sooner, rather than later, so that we could describe our views to the GDE in time for its early December meeting. Here are some of the questions we might address: What sorts of damping ring work will you, and your colleagues at your home institution, be pursuing during the next year or two? If your home institution is an accelerator lab, how do you think the global damping ring effort might best take advantage of your facilities for damping ring work? Whether or not you are based at an accelerator lab, how do you think we should use the existing accelerator infrastructure in a globally coherent way to develop the damping ring design? How do you think we should go about organizing a global damping ring R&D effort?

3. Here is a table of comments, interests, and planned activities from some of our damping ring colleagues.

Category HV pulse drivers for stripline kickers Organization Diversified Technologies, Inc. (USA) Author of comments Floyd Arntz Ph.D. arntz@divtecs.com +1 (781) 275-9444 x204 Diversified Technologies, Inc. 35 Wiggins Avenue Bedford MA 01730 Description of interests We at Diversified Technologies, Inc (DTI) are particularly interested in developing HV pulse drivers for stripline kickers. Our principal product family relates to HV and high-current modulators, and we would like to stretch this family into the 4-nanosecond FWHM HV pulse regime. (We also manufacture beastly HVDC supplies.) Regarding the many, many other challenges relating to the ILC damper rings, we stand back and watch in awe! Of course, please call on us if you should encounter other issues on which we might possibly help.

Category Fast kickers Organization University of Illinois (USA) Author of comments George Gollin g-gollin@uiuc.edu +1 (217) 333-4451 Description of interests In collaboration with Cornell and Fermilab, we will continue our studies of a stripline kicker in Fermilab's 16 MeV electron beam at A0. Our primary interests are in understanding timing and amplitude stability issues, and learning how well these can be studied at Fermilab. We will finish our modeling of a Fourier Series kicker and, in collaboration with Fermilab's RF group, develop a prototype module for further studies.

Categories Demonstration of the fast kicker with real beam Fast feedback study for the extracted beam Wiggler dynamics study Fast Ion instability study Precise BPM development for 1pm emittance Organization KEK-ATF (Japan) Author of comments Masao Kuriki masao.kuriki@kek.jp How do you think the global damping ring effort might best take advantage of your facilities for damping ring work? KEK-ATF is a test facility dedicated to ILC DR development. Since it is a prototype of LC DR, various studies other than listed, are possible. How do you think we should use the existing accelerator infrastructure in a globally coherent way to develop the damping ring design? After the conceptual design is fixed, the engineering design is rather important. To establish the reliability of devices and systems, total demonstrations as real as possible, is necessary in an existing facility. How do you think we should go about organizing a global damping ring R&D effort? Some duplications might be OK. The most important thing is to encourage their own efforts as ILC R&D. If there are any issues uncovered by existing activities, it is better to promote them if possible.

Category beam dynamics issues:  - design and optimization of lattices  - characterization of collective effects  - CSR effects  - low-emittance tuning techniques  - nonlinear dynamics. kickers: physics design for a stripline kicker Organization LBNL (USA) Author of comments Andy Wolski awolski@lbl.gov +1 (510) 486-6549 Description of interests Over the coming year, our studies at LBNL will focus on beam dynamics issues in the damping rings, specifically: - design and optimization of lattices; - characterization of collective effects, including space-charge, IBS and microwave instability; At the KEK-ATF, we plan to pursue studies of relevant beam dynamics, including CSR effects, low-emittance tuning techniques and nonlinear dynamics. We shall also contribute to kickers R&D at the KEK-ATF, by developing a physics design for the stripline kicker for single-bunch extraction. How do you think the global damping ring effort might best take advantage of your facilities for damping ring work? Our main accelerator facility at LBNL is the ALS. We have used this in the past for studies related to the damping rings, in particular for looking at low-emittance tuning, IBS and ion effects. Recently, we have not been so active in these studies, because the ATF is able to achieve lower emittance and make better measurements because of their advanced diagnostics; also, the effort we have here to apply to these studies is limited, as is the time available on the machine. If there is a real need for studies at the ALS that cannot be done elsewhere, we can take another look, but we do not have plans for any such studies at present. How do you think we should use the existing accelerator infrastructure in a globally coherent way to develop the damping ring design? I would like to see the GDE taking more of a lead, but in a way that fully involves the community.

Category Pol. Positron generation R&D at EXT Laser wire R&D in Damping Ring High quality electron beam generation by photo-cathode RF Gun X-SR Monitor R&D ODR R&D Beam Based Alignment R&D Nano-BPM project of SLAC, LLNL and LBNL Nano-BPM project of KEK FONT project Laser Wire project at EXT Fast Kicker Development project Fast Ion Instability Research Multi-bunch Instability Study Dynamic aperture study with/without wigglers High resolution BPM circuit R&D for 1 pm vertical emittance development (single pass BPM system) Low level signal generation for FS kicker Precise alignment study with electron beam and laser beam Compton based positron generation study Transverse and longitudinal instability study in the DR, feedback system development for such instabilities Feedforward system development for the stabilisation of the extracted beam Organization KEK-ATF (Japan) Author of comments Junji Urakawa junji.urakawa@kek.jp Comments and more information Since Kuriki already replied, I only mention about the ATF International Collaboration. Following is the announcement on ATF International Collaboration. Please see our URL to get a password. We are preparing the new ATF web site for the ATF International Collaboration: see http://atf.kek.jp. You may register at http://atf.kek.jp/collab/modules/profile/register.php. After your account is activated you will receive an email notification from the system. In case of problems please contact nobuhiro.terunuma@kek.jp.

Organization KEK (Japan) Author of comments Nobu Toge (KEK, Accelerator Lab) email: toge@lcdev.kek.jp voice: +81-29-864-5224 fax: +81-29-864-3182 Comments I would strongly support and endorse your proposal for in-depth, true-to-the-facts discussion on ILC DRs. May I suggest the following - To make it into a reality, for instance for people to actually spend ~30 minutes at Frascati on this in ways you outlined and so on, it might help if you communicate on this matter (e.g. discussion proposal) with Tor Raubenheimer, Gerry Dugan and Barry Barish, who do not appear to be on your email list, and win their support beforehand. ps. We need to do something similar for SRF and cavities, too.

Categories Electron cloud Fast ion instablity Wigglers Dynamic aperture studies Organization CERN (Switzerland/France) Author of comments Frank Zimmerman Frank.Zimmermann@cern.ch Description of interests Electron cloud simulations and benchmarking on SPS and DAFNE. Development of new 3-D electron cloud simulation code. Theoretical investigations of fast beam-ion instability. Contributions to ATF and ATF-2 (hardware and simulations). Wiggler technology. Dynamic aperture studies. Electron cloud studies can be performed with or based on SPS measurements. The SPS is eqipped with numerous e-cloud diagnostics (e.g., spatial and energy distribution of electrons, in situ SEY measurement, heat-load detectors, etc.) I think a lot can be learnt from and done at the ATF, which is open for international collaborators or groups, and which is a 100% R&D facility. Some studies can be done at user facilities. Maybe some work should be done on large rings, e.g. HERA e- ring, which has the circumference of the recommended ILC damping rings.

Category Wiggler design Kicker/Pulser Electron cloud Lattice Evaluation Superconducting RF CESR Test Facility Design Studies Organization Cornell/CESR (USA) Author of comments Dave Rubin dlr@cesr10.lns.cornell.edu Description of interests 1.Wiggler Design Evaluation of dynamic aperture for permanent magnet wiggler Optimization of design of superconducting wiggler (in particular tolerable roll off of vertical field in horizontal plane) 2.Kicker/Pulser – Plan for A0 test beam experiment 3.Electron cloud – simulation and measurement of E-cloud density in special vacuum chambers, and in wigglers, and instability threshold vs bunch configuration/current in CESR 4.Lattice Evaluation – especially dynamic aperture and space charge 5.Design of high gradient, superconducting RF cavity. Evaluation of 2-cells per coupler concept. 6.CESR Test Facility Design Studies a)Lattice and configuration study to provide for tests over energy range 1.5-5.5 GeV of:  -Prototype wiggler  -Prototype SRF cavity  -Electron cloud in chambers, wigglers, and instability threshold  -Extraction kicker b)Instrumentation for minimzation of vertical emittance  -Beam based alignment (BPM)  -Beam size measurement c)Development of algorithms for beam-based alignment, coupling and dispersion correction d)Feedback systems We plan to make CESR available to the community for tests of instrumentation, investigation of electron cloud and ion physics, development of beam based alignment algorithms, etc.

Categories ultra-high resolution BPMs fast kickers electron cloud suppression instability control via bunch-by-bunch feedback simulation tools development Organization SLAC (USA) Author of comments Yunhai Cai yunhai@slac.stanford.edu Description of interests Intentions of R&D for ILC damping rings at SLAC for the next two years... here is roughly what I know: 1. Develop ultra-high resolution beam monitors by Mark Ross in collaboration with ATF at KEK. 2. Develop a fast kicker for injection and extraction by Mark Ross in collaboration with ATF at KEK. 3. R&D of a grooved metal surface by Mauro Pivi for reducing the secondary emission yield and control electron cloud. It will be tested in the Low Energy Ring (LER) at PEP-II. 4. R&D of electrode by Lanfa Wang to clear the electrons near the beam inside the dipole and wiggler magnets. It also can be test in the LER at PEP-II. 5. R&D of a faster bunch-by-bunch feedback system by John Fox to handle the multi-bunch instabilities caused by fast ions and electron cloud. The goal is to control the instability that grows at rate of a few turn. Also study feasibility to damp the single-bunch head-tail mode as well. 6. Develop computational tools to simulate both fast ions and electron cloud effects and benchmark codes against controlled experiments at PEP-II or other accelerators. There are things that may be missing from this list. But it is a good start. We are writing detailed proposals for these programs.

Categories Lattice optimization Simulation tools Vertical emittance and coupling correction algorithms Single bunch limit studies Ion instability Hybrid wigglers Organization Argonne National Laboratory (USA) Author of comments Louis Emery emery@aps.anl.gov Aimin Xiao xiaoam@fnal.gov Description of interests 1) Lattice optimization. Add details to the design: various errors, optics correction scheme and regions for rf, injection and extraction. An electron ring, which have different objectives than the positron ring, should be designed to check the consequences of a longer damping time. Search design variable space with multi-objective evolutionary algorithms. 2) Simulation Tools: Add to tracking code elegant space charge forces (done), vertical emittance with synchrotron radiation, SVD for orbit correction. 3) Develop an algorithm and scheme on vertical emittance and coupling correction. 4) Study single bunch limits with particle tracking with wakefields modeled from 3D codes. 5) Study ion instability on APS ring. (answers question 2 of your email) Once we observed ion instability only when a vacuum leak occured. 6) Design a hybrid wiggler which would meet the field quality tolerance of the OCS reference lattice design. This is for cost estimation.

Category Electron cloud issues Organization DESY Author of comments Rainer Wanzenberg Description of interests DESY has closely collaborated with CERN on this subject. Recently a PHD student at the University of Rostock has started to work on eclouds in collaboration with DESY.

Categories Electron cloud Ion effects Organization DESY Author of comments Guoxing Xia Deutsches Elektronen-Synchrotron DESY FLC Group Notkestrasse 85 22607 Hamburg, Germany Email: guoxing.xia@desy.de Tel: +49-40-8998-3856 Description of interests We will concentrate the research work on damping ring R&D as follows: 1. Electron cloud effect in positron damping ring 2. Ion effects including fast ion instabilities Rainer mainly simulates the electron cloud effects in OCS and alternative TESLA positron damping rings in different cases (different sections: straight section, wiggler section and arc section; different SEY, from 1.0 to 2.0; different photoelectron yield, from 0.1 to 0.01 with antechamber). Eckhard and I will continue our work on ion effects in damping rings. We will theoretical study on some issues as following: Minitrains in the bunch train to mitigate the ion effects; Ion-induced vacuum pressure instabilities in the positron damping ring; Further simulation of fast ion instability with different models and comparision of the output results; Collaboration with KEK-ATF colleagues on research work on fast ion instability. If possible, do some experiments on fast ion instabilities in ATF Damping ring (including the minitrain effects, mixture gases effects, lattice-related FBII growth time variations, etc; Ion-induced beam lifetime reduction, ion clearing electrodes in the damping rings etc. We are now thinking about what we can do in our existing machines for damping ring R&D. If possible, we would like to carry out some research work in DESY. I think it is quite fine that we can organize a global damping ring R&D effort. The above-mentioned contents will be added by other colleagues of DESY ILC Damping Ring Community if they are not complete yet.

Categories Lattice design Simuations of microwave instability; Impedance modeling Organization SLAC Author of comments Yunhai Cai (yunhai@slac.stanford.edu) Description of interests For SLAC, I would like to add two more items related to the design of damping rings: Lattice design: optimize a lattice for damping ring to achieve the specified parameters and with adequate dynamic aperture. Simulation of microwave instability and develop a realistic impedance model for the damping rings by Sam Heifets and Gennady Stupakov.

Categories Fast kicker system: design and test with beam Electron cloud Wigglers Feedback systems RF separators Organization INFN-LNF (Italy) Author of comments Susanna Guiducci (Susanna.guiducci@lnf.infn.it) Description of interests The design of a fast stripline kicker is ready; we plan to build and test a prototype and to install a pair of kickers (180 degree phase advance apart) at DAFNE and test with beam. Electron cloud measurements and code benchmarking at DAFNE: installation of electron detectors, vacuum chamber coating. Study the possibility of modifying the DAFNE wiggler pole shape to follow beam trajectory and reduce the effect of field nonlinearities on the beam. Design the longitudinal feedback kicker cavity (DAFNE type), study possible effects of the vertical feedback on the low vertical emittance. Study the possibility of pushing the bunch distance to very small values by using RF separators. How do you think the global damping ring effort might best take advantage of your facilities for damping ring work? The DAΦNE φ-factory has for some aspects characteristics similar to DR: High current electron and positron rings, very short bunch distance, powerful digital feedback systems, high percentage of radiation emitted in wiggler magnets. It can be used for tests and measurements on DR related issues.

Categories lattice e-cloud effects collective effect connected with impedance Organization IHEP (China) Author of comments Gao Jie Description of interests We have worked on a 7 GeV TESLA type ring. IHEP is a high energy phyics lab with an e+e- collider (BEPC-II) to be built in two years (now under construction). What we hope to work on are the lattice, e-cloud effects, and collective effects connected with impedance.

Category Permanent magnet wiggler optimization Organization YerPhI (Armenia) Author of comments Albert Babayan (babaian@yerphi.am) Description of interests In YerPhI already is performed the work on the magnetic design optimization of the TESLA TDR permanent magnet wiggler. This work is executed within of the cooperation agreement between DESY and YerPhI. Field map of optimized permanent magnet wiggler was placed on the ILCDR web site: http://www.desy.de/~awolski/ILCDR/DRConfigurationStudy_files/Task1.htm We will continue development and magnetic design optimization of PM wiggler according to ILC DR Baseline Configuration Document. In collaboration with LNF we plan study the effect of wigglers on beam dynamics of damping ring for the International Linear Collider.