BERLinPro. An ERL Demonstration facility at the HELMHOLTZ ZENTRUM BERLIN

Transcription

1 BERLinPro An ERL Demonstration facility at the HELMHOLTZ ZENTRUM BERLIN

2 BERLinPro: ERL demonstration facility to prepare the ground for a few GeV Berlin-Adlershof Goal: 100MeV, 100mA beam Small emittance, rel. short bunches High current: to address needs of storage ring users Show energy recovery Explore limits of ERL (multiturn, injection energy) Show different operational modes: high current (100mA, 2ps), short pulses (10mA, 100fs),??, => superiority of the ERL concept to storage rings Main components: SC-RF gun Booster module Cornell development with minor modifications Merger: C-chicane, 4 rectangular dipoles Linac: based on Tesla technology, modified for high current Return arc: TBA Second loop option 2

3 Finances and time table : go ahead for gun development R&D money for gun development secured Further approval process for entire budget 2010 beam from 1.6 cell gun cavity in HoBiCaT Conceptual design 2011 Technical layout (TDR) 5 years after approval: first recirculated electrons 3

4 GUN DEVELOPMENT SRF Gun 100 MeV Main Linac SRF Module 5-10 MeV Merger Section 1.5 MeV Spent Beam Beam Dump Return Arc SRF Booster Beam Manipulation Undulator tests 4

5 BERLinPro gun: Staged approach A high brightness source which can deliver high average current and short pulses. Stage 1-Beam Dynamics: Produce beam with cold gun in existing HoBiCaT cryomodule. Nb cavity with Pb-coated cathode (J. Sekutowicz & Co), UV laser (MBI), sc solenoid and beam diagnostics. Stage 2-Cathode integration: Extend HoBiCaT bunker, new cryomodule, cathode preparation infrastructure. Produce 1 to 10 ma with CsK 2 Sb cathode, green laser (MBI). In parallel, test gun cavities and new RF coupler (>100kW) in HoBiCaT. Stage 3-High current operation: Build SRF gun for BERLinPro (high rep. rate) From J. Sekutowicz, Proc. of PAC09 Courtesy of Thorsten Kamps 5

6 Stage 1 setup in HoBiCaT 1.6 cell cavity, sc-solenoid, Helium supply Stage 1 diagnostic beam line View screens, stripline, current monitor, emittance measurement, energy measurement 6

7 HoBiCat preparations: 7

8 MERGER DESIGN CONSIDERATIONS SRF Gun 100 MeV Main Linac SRF Module 5-10 MeV Merger Section 1.5 MeV Spent Beam Beam Dump Return Arc SRF Booster Beam Manipulation Undulator tests 8

9 Zigzag chicane: (Brookhaven) Space charge forces: compatible with emittance compensation scheme equal focussing in both planes 2. order dispersion not 0 Small trajectory displacement Fixed relation D1/D2 Geometrically challenging (vertical construction in Brookhaven) C-chicane: Higher order dispersion: intrinsically cancelled by C-chicane with rectangular magnets Easier to incorporate in machine Flexible drift lengths Offset adjustable by drift length Vertical focussing 9

10 ASTRA: Emittance for Zigzag / C- chicane for increasing bunch charge and different energy spread (correlated) C-chicane Zigzag Gaussian bunch: ε x,y = 1.0 π mrad σ x,y = 1.0 mm σ z = 1.0 mm β x,y = 20.0 m α x,y = 0 10

11 Bunch lengthening in merger due to energy spread / space charge Effect is reduced when going to 10 MeV injection energy. 11

12 Emittance vrs. bunch length Emittance depends strongly on bunch length: 77pC Charge σz Compression 77pC 6ps 3 or more 10pC 1ps 10 or more 10pC Gaussian bunch: E = 10 MeV ε x,y = 1.0 π mrad σ x,y = 1.0 mm β x,y = 20.0 m α x,y = 0 σ E = 20keV 12

13 Lambertson magnet: Good idea?? By Lars-Johan Lindgren, MAX-lab Last merger dipole deflects high energy beam by up to 4 => extra chicane necessary Lambertson: High energy beam travels in field free region, injected low energy beam runs parallel Lambertson would reduce 4 to less than 0.14, which is rather an orbit correction 13

14 Last merger dipole Lambertson? Steerer α d L1 α [ ] as a function of d, L1 d \ L2 0.4m 0.8m 1.2m 10mm mm mm rad = 1.432deg. High energy beam deflected by 1/10: 0.14 mean 2.5cm offset after 10m linac Steering for HE beam is necessary Place for HE optical elements before Lambertson 14

15 Linac: SRF Gun 100 MeV Main Linac SRF Module 5-10 MeV Merger Section 1.5 MeV Spent Beam Beam Dump Return Arc SRF Booster Beam Manipulation Undulator tests 15

16 100 MeV Linac: 1.3 GHz Start with multicell TESLA and adapt this for CW and high current Single cryomodule with 6-7 cavities 7 cells/cavity (?) Application Verbundforschungsantrag : federal funding for a collaboration with Univ. Rostock and Dortmund for the calculation of HOM Options for HOMs: Ferrite loads, waveguide dampers HoBiCaT test 16

17 RECIRCULATOR - ARC SRF Gun 100 MeV Main Linac SRF Module 5-10 MeV Merger Section 1.5 MeV Spent Beam Beam Dump Return Arc SRF Booster Beam Manipulation Undulator tests 17

18 Path length management: Short bunches require pathlength adjustment Second loop option: 100MeV: 1. turn: L=(n+1/2) λ rf 200MeV: 1. turn: L= n λ rf (λ rf /2=12cm) Variable injection energy alters path length in merger & splitter for HE beam 20 o 5-20MeV = MeV => 0.5cm E = E 0 cos (ωt +φ 0 ) head with higher E gives compression with normal arc R 56 E φ = π L = 2 φ 0 /2π λ rf =2-3cm φ 0 =20deg. t φ = π 2 φ 0 X chirp at deceleration doubles inacceptable energy spread Courtesy of Michael Abo-Bakr 18

19 3 Approaches to pathlength adjustment: 1 - Brookhaven: Build arc on sledge, mechanical adjustment very precise expensive slow 2 - C-chicane 100MeV: 2-3m CSR bunches are short 3 - Incorporate into the arc S B D D 0 Angle and offset for 6cm additional pathlength ϕ 1, 3 [ ] ϕ 2 [ ] ψ K [ ] x max /cm ψ K ρ 1 φ 1 φ 0 ρ 0 X 1 X 0 Courtesy of Michael Abo-Bakr 19

20 Radiation safety requirements: Different league than storage rings Drive costs =>drive beamloss requirements Permissable beamloss:<1e-5? => Too little space for shielding above ground => Consider construction underground reduced shielding, vibrations and temperature fluctuations at comparable costs 20

21 Cryogenic plant BESSY II 21

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23 Building: All dimensions preliminary Storage Ring Hall 55m 6.4m 15m 6.0m 23