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The project of Super-ct-factory with Crab Waist in Novosibirsk
E.Levichev Budker Institute of Nuclear Physics, Novosibirsk Japan-Italy Collaboration Meeting “Crab Factories”, Frascati, December 10, 2008
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Contributors to the report
A.Blinov A.Bogomyagkov A.Bondar V.Kiselev I.Koop G.Kurkin E.Levichev P.Logachev S.Nikitin I.Okunev V.M.Petrov P.Piminov Yu.Pupkov S.Sinyatkin A.Skrinsky D.Shatilov V.Smaluk P.Vobly
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C-tau Conceptual Design Report in Novosibirsk
History C-tau Conceptual Design Report in Novosibirsk ► E = 700 – 2500 MeV ► Round beams L=1034 cm-2s-1 ► Monochromatization L~1032 cm-2s-1 ► Long. Polarization L~1034 cm-2s-1 ► Transverse polarization for precise energy calibration 1995
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Motivation of restart ► Invention of the crab waist collision scheme (P.Raimondi, March 2006; demonstration: DAFNE, 2007) ► Exciting results of B-factories ► Russian Government is ready to support ambitious modern projects in fundamental science
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Processes at tau-charm factory
Ds D
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Tau-charm physics Charm Charmonia Spectroscopy Spectroscopy, BFs
(Semi)leptonic decays Rare decays Mixing CP violaton … Charmonia Spectroscopy, BFs Light hadron spectroscopy J/ rare decays … Tau Spectral functions, BFs Lorentz structure CP violation LFV decays … Charm baryons BFs Semileptonic decays … Requirements: L > 1034 cm-2 s-1, longitudinal polarization
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Specifications ► Variable energy Ecm= 3 – 4.5 GeV (from J/psi to charm baryons) ► L = 1÷2×1035 cm-2s-1 ► At least one beam (e-) should be polarized longitudinally ► No energy asymmetry is needed ► No beam monochromatization is needed ► Energy calibration with medium accuracy (Compton backscattering)
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Facility key features and principles
► Two rings with a single interaction point ► Crab waist collision extreme importance of the FF design ► Polarized e- injector and longitudinally polarized electron beam at IP ► Wigglers to keep the same damping and emittance in the whole energy range (optimal luminosity) ► Low emittance arc cell ► A wide adaptation of the existing injection complex, construction facilities (tunnels, halls, etc.) and elements (wigglers, etc.) for cost effectiveness Both CT project in Novosibirsk and SuperB in Tor-Vergata exploit the Crab waist approach similar problems and solutions good background for collaboration
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Layout Injection facility exists
Tunnel for the linac and the technical straight section of the factory is ready
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Specification for the FF design
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FF based on telescope design
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Final focus trajectories
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Betatron frequency bandwidth
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Main accelerator parameters
8 m of the SC wigglers with 20-cm-period are used to control the beam parameters at different energies
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Lattice Interaction region betas Dispersion function
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Lattice Technological section
Arc cell (FODO but close to the theoretical minimum emittance) Transverse DA is a crucial problem !!! Betatron tune bandwidth 1%
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Damping wigglers The damping wigglers keep the damping time Tau_x =30 ms and the horizontal emittance (10 nm) in the energy range 1.5 – 2.5 GeV Field amplitude at 1.5 GeV 4.3 T Period length 0.2 m Total length 8 m Damping integral i2 at 1.5 GeV 2.76 m-1 Excitation integral i5 at 1.5 GeV 0.01 m-1 Wiggler with similar parameters produced by BINP Wiggler field amplitude vs energy
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Luminosity
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Longitudinal polarization at IP
Schematic view of the longitudinally polarized e- at IP Degree of the LP at IP as a function of the beam energy
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Integration of polarization insertion
into the current variant of the Super C-Tau magnetic structure
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Polarized electrons source
Beam polarization % Polarization lifetime – 4500 s Cathode voltage (pulsed) kV Photocathode type Strained InGaAsP Laser type Ti – Sapphire Light wavelength – 850 nm Laser energy in a pulse mkJ Pulse duration ns Repetition rate Hz Number of electrons/pulse *10^10 Photocathode quantum efficiency 1% Photocathode recesiation time (depends on laser power) – 560 hours
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Injection facility
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Positron production High positron yield Y = 0.1 e+/e-/GeV
Positron conversion target Positron production section High positron yield Y = 0.1 e+/e-/GeV 10 T pulsed magnet positron concentrator
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Injection facility upgrade
Today: 21010 e-/pulse (1.5% conversion) 3 108 e+/pulse 50 Hz = 1.51010 e+/s Upgrade: e- current increase ( 3) Better focusing in positron linac ( 1.5) Debuncher usage ( 2) = 1.351011 e+/s Reserve: electron energy can be increased by 100 MeV ( 1.3)
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2.5 GeV linac ► Using the same accelerating structure as for the existing injection facility ► 13 accelerator modules (200 MeV, 16 m) each of 4 accelerator structures. Totally 208 m ► In a 1-m straight section between the accelerator structures there are two quadrupoles, BPM and vacuum valve ► Four accelerator structures (one module) are fed by one 5045 klystron (SLAC) ► Repetition frequency is 50 Hz
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Energy calibration Compton backscattering E calibration (~10-410-5)
CBS vs RD for 3 months Sigma = 42 keV Spectrum edge
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SCT location FF region Technical reg. (RF and injection)
Damping wiggler sections Hall is ready
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Summary C-tau factory with L = 1035 cm-2 s-1 seems to be an extremely attractive facility for HEP experiments Crab-waist approach allows us to obtain such luminosity with achievable machine parameters: required beam intensity, low emittance, injection efficiency, polarization features have been already obtained in B- and Phi-factories, light sources, etc. First test of the crab-waist approach was successfully passed in Frascati We are in the beginning now and there are many things have to be done (further optimization of the FF design, the DA optimization, Touschek lifetime increase, etc.). But at the same time we have an advantage-ground to start the project: injection facility is under commissioning, tunnels for linac and injection lines are ready, a lot of the facility solutions are based on existing wares and technologies.
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