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Positron Source and Injector

Positron Source and Injector. Variola – LAL, Orsay Elba Meeting 2011. Actual status with open points Positron source Scheme Linac To do List. Injector :. 1) Positron source 2) Polarimetry 3) Linac lattice 4) Scheme

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Positron Source and Injector

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  1. Positron Source and Injector Variola – LAL, Orsay Elba Meeting 2011

  2. Actual status with open points • Positron source • Scheme • Linac • To do List

  3. Injector : • 1) Positron source • 2) Polarimetry • 3) Linac lattice • 4) Scheme • We lost the only researcher at (quasi) full time on SuperB. We are replacing him but needs time…

  4. Preger – Guiducci Scheme Diag line Energy, spread, beam size current “new” scheme Separator e+-e- Monitor Size and position En spread 300 MeV CAPTURE SECTION THERMIONIC GUN SHB PC 0.6 GeV 0.7 GeV HE diag Emittance,,En spread 0.6 GeV (safety) monitor combiner DC dipole Bunch length Emittance e+ BUNCH COMPRESSOR Moller polarimeter 4 GeV (straight line) 5.7 GeV e+ 4.0 GeV e- B graded S band Sections 50 MeV 0.2 GeV POLARIZED SLAC GUN e- SHB 250 MeV matching We propose to stay with the SLAC gun in the positron line and to have a custom Polarised, low charge electron sources in the electron line Diag lina Polarization, en spread Emittance bunch length HE diag Emittance,,En spread Proposal for Vacuum regions

  5. Positrons (thanks to Freddy) - 1) Target production and optimization • 2) AMD vs QWT, Parmela, Geant4 and Astra ok • 3) Polarization studies (Geant4) – not needed • 4) Capture in 4 different scenarios : • S band acceleration + S band • S band deceleration + S band • L band deceleration + L band • L band TM020 deceleration + L band • 5) Transport (FODO design) up to 1 GeV in the 4 cases • 6) Coupling studies • 7) 1.428 GHz cavity design • 8) TM020 cavity design : 4 cells will be prototyped in Aluminium • 9) Comparison with Dafne source (~ok). Experiment soon?

  6. RF in tanks • P.Lepercq (LAL) has calculated the Travelling Wave Fields in SuperFish and adapted them for ASTRA’s simulation: Field line in a 6 cells TW cavity 2π/3 mode Longitudinal field in a single tank (2.856 GHz): Seen by ref. particle 25 MV/m Adaptation and normalisation 1 tank = ~3.054 m P.Lepercq

  7. Realisations:Design Study of Travelling wave Section (1) • Design of RF structure (using Superfish) • Structure with 6 cylindrical cavities • Using TM020-2/3 • Operating at 3 GHz • Design Parameters: • Cell dimensions: Rcell ~ 9 cm Lcell ~ 3.331cm • Irises dimensions: Riris=1.5 cm Liris= 0.8 cm E-field TM020-2/3 Ez along z-axis P.Lepercq

  8. Design Study of Travelling wave Section (2) • 3D Structure (Under study) • Structure will include reduced height waveguides for matching • The goal is to realize a low power demonstrator in aluminum material (and if it is ok a copper one) S11 (dB) Mode  Mode 0 Mode 2/3 HFSS Simulation • Simulations show the good separation of the TM020 -2/3 E.Mandag

  9. Target Yields Studies Target Geant 4 simulation (O. Dadoun – LAL): 1.7 If we increase the energy of the drive beam, the positron yield goes up. For a 600 MeV e- beam, the optimum yield is 1.7 e+/e- with a W-target thickness of 1.04 cm O.Dadoun

  10. Stress and thermal effects • PEDD • @200 MeV Pedd 1.7 10-12 J/g/e- • @ 300 MeV Pedd 2.5 10-12 J/g/e- • @ 500MeV Pedd 3.3 10-12 J/g/e- • 6.6e10*5 = 3.3 1011 e- (10nc 5 bunch) • So (max limit 35 J/g) • 200 MeV on a PEDD= 0.55J/g • 300 MeV on 0.85 J/g • 500MeV 1 J/g • AVERAGE deposited energy: • @200 MeV 52.5 MeV/e- / @ 300 MeV 77.6 MeV/e- / @ 500MeV 120 MeV/e- • Tungsten density 19.25 g/cm3 • So for the different cases in a cubic cm target we have to multiply for 25 (Hz) and ~20 (density) • So in the worst case (500 MeV) we have 160W (70 W@200 and 100W @300). Not so hard to cool O.Dadoun

  11. The ACS • Accelerating / Deceleration • depending on the type of RF cavities within the ACS • 1st scenario = 2.846 GHz full acceleration • 2nd scenario = 2.846 GHz deceleration + acceleration • 3rd scenario = 1.428 GHz deceleration + acceleration • 4rd scenario = combination of RF types (using 3 GHz TM020 mode for deceleration and 1.428 GHz TM010 for downstream acceleration).

  12. Recap 25MV/m for acceleration • 4 Scenarios under investigation With a positron injection of 10 nC and a yield of 3.9%, we will have 2.43 109 positrons at 300 MeV ±10MeV(scenario 2 – 2.8 GHz)

  13. End of 1st Tank – 3000 MHz Scenario 4 • Length of 1st tank = ~2.93 m • Cell length= 3.331cm • Tank Phase f1= 280o • Tank Gradient G1=10MV/m Gaussian Fit sz = 3.66 10-3 m Energy (MeV) Energy (MeV) Z (m) Z (m)

  14. Layout Example Up to ~1050 MeV Acc. Cavity 1.428 GHz, Peak gradient= 13MV/m 3 GHz 10 MV/m Fodo cells 38  ~160 m Solenoid 0.5 T 0.534.1 m Matching section 34.3 ~38 m

  15. At end of the fodo accelerating section 3.0 GHz tank (deceleration), ~1050 MeV At ~160 m, after the target. At exit of last cavity, Particles within a cut radius: Yield (e+/e-) Total yield Yield ± 10 MeV Energy (MeV) 1050 ±10 MeV Radius (m) Z (m) 240 pC F.Poirier

  16. Further studies at 1 GeV Example from 1.428 GHz (scenario 3) • Emittance matching • En Spread matching • Coupling correction • Linearization • Matching with the transfer line • Injection in DR Y (m) X (m) Cross-plane Coupling !!! use cross plane correction

  17. New idea- Linearization in `TM 012/030 L Band (but canworkalso in S…) Use of SW 4.284GHz cavities for longitudinal beam shaping • At the exit of 1st cavity • Eavr = 954.7MeV • dE = 22.4MeV • At the exit of 3rd cavity • Eavr = 927.3MeV • dE = 14.9MeV • At the exit of the Conventional Linac • Eavr = 967.3 MeV • dE = 26.4 MeV • At the exit of 5th cavity • Eavr = 898.1MeV • dE = 8.4MeV • At the exit of 7th cavity • Eavr = 868.8MeV • dE = 5.6MeV Feasible, but $ and cavities. Can be interesting for S band, but see before… Thalia.Xenophontos

  18. LINAC

  19. First order linear design for the main linac, considerations. Exit from the damping ring : H plane => e= 3.3 10-8 a= 0.47 b = 11.81 V plane =>e = 1.8 10-8 a = 0.52 b =16.14 Use of commercial Qpoles

  20. Tested: • Both quadrupoles • 1 / 2 / 3 SLAC cavity period 3,5 / 7 / 10,5 m • Doublet lattice • Best solution found => 2 cavity period FODO, ~ 4.5 T/m • Matching line simple (3 quads)

  21. Period, 2 Slac S Band cavities / EMQO-01-200-340 Beam envelope. Final energy 5 GeV H Pascal

  22. Non exhaustive to do list

  23. SIMULATIONS : • 1) L Band Scheme, positron capture • - Coupling compensation • - Emittance matching in the damping ring • - L Band solution with 1.5 cm aperture cavities (to increase the gradient) • - Hybrid Linac (starting from the end change the L Band with S Band) • 2) S Band Scheme, positron capture • - Capture with 1.5 and 2 cm aperture • - Final linearization with 0.9, 1.5 and 2 cm aperture. Cavities in TM 012 or 030 modes • - Deceleration with large aperture • 3) Possible experiment on DAFNE Linac with deceleration • 4) 0.6-1 GeV drive beam Linac for positron production (based on DAFNE Linac design?) • 5) Positron target • - PEDD from 10 to 16 nC • - Thermal budget from 10 to 16 nC • - Neutrons • 6) Main Linac • - C band solution? • - Validation of the geometry (distance between cavities, integration of Qpoles, diagnostics and pumps) • - Full tracking simulation • - Alignment errors • - Matching section after the Transfer line • - Check that the actual FODO can provide transport for 0.2 and 1 GeV (new Preger and Guiducci scheme) • 7) Electron source • - Gun (recover the SLAC results) • - 200 MeV Linac simulation • - Matching and deflector for 0.2 and 1 GeV beams • - Diagnostics and polarimetry • 8) Damping ring • - Injection and injection losses

  24. TECHNICAL DESIGN • RF design and prototyping • L Band cavity with 1.5 cm aperture (grad maximization) • S Band cavity with 1.5 and 2 cm aperture • TM 012,030 cavities for linearization (s band and L?) • Prototyping: TM020 L band, High gradient L band, Large aperture S band, Linearization S Band. • QWT Engineering • Design and pulsed magnet engineering • Vacuum chamber and permanent magnet • Vacuum • Vacuum design for all the linacs systems, integration • RF system • Rf klystrons for S and L band • Sled (L band design) • Network • Integration of everything!!!

  25. Conclusions • 1) Scheme ready (guns?...) • 2) A lot of work has been done to find a cheap solution • 3) Technical constraints must be solved by prototyping. $? • 4) We miss manpower (end of the year +1). Other French labs? Frascati or Italy? Who else? • 5) Also at the Lab support level we need a project. • We are ready to pursue our effort but in a well defined scheme and with the necessary manpower • Thanks to everybody providing me slides

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