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 We lost the only researcher at (quasi) full time on SuperB. We are replacing him but needs time…

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

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?

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 P.Lepercq 1 tank = ~3.054 m

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

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

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

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

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).

Recap 4 Scenarios under investigation Scenario 1 2 3 4 25MV/m for acceleration Scenario 1 2 3 4 RF (MHz) – strategy 2856 - acc 2856 – dec (S-band) 1428 – dec (L-band) 3000 dec + 1428 - acc Mean Energy (MeV) 302 287 295 333 Erms (MeV) 21.4 32.3 (12) 16.83 (9.09) 5.2 (3.2) Zrms (mm) 2.7 6.4 8.89 3.5 Xrms (mm) 3.8 4.4 8.0 8.1 X’rms (mrad) 1.02 1.11 1.69 1.4 Ex =X’X (mm.mrad) 4.6 13.0 11.4 Total Yield (%) 2.8 7.53 32.3 31.9 Yield ±10MeV (%) 1.3 3.9 19.6 29.3 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)

End of 1st Tank – 3000 MHz Length of 1st tank = ~2.93 m 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)

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

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: Energy (MeV) Yield (e+/e-) Total yield Yield ± 10 MeV 1050 ±10 MeV Radius (m) Z (m) 240 pC F.Poirier

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

Use of SW 4.284GHz cavities for longitudinal beam shaping New idea - Linearization in `TM 012/030 L Band (but can work also 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

LINAC

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

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)

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

Non exhaustive to do list

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

 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!!!

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