FAIR accelerator R&D Oliver Kester GSI Helmholtzzentrum für Schwerionenforschung Darmstadt and IAP Goethe-Universität Frankfurt

Introduction Outline Accelerator challenges and R&D Outlook Challenges FAIR heavy ion accelerators Preparation of the injectors at GSI Accelerator challenges and R&D High current ion sources Beam dynamics and cavities Injection / Extraction Cryomodules SIS100 Outlook

FAIR accelerator challenges Diagnostic and XHV at highest intensities Superconducting magnets FLAIR Rf-cavities Beam cooling

Preparation of the injector chain Exchange of 35 years old Alverez accelerator With modern interdigital H-type structures Higher intensities  28 GHz ECRIS SIS 18 upgrade Fast ramping, enhanced intensity per pulse Increase of injection acceptance Improvement of lifetime for low-charged U-ions Increase of beam-intensity per time due to reduction of SIS18- cycle time UNILAC upgrade High power (high intensity), short pulses Increase of beam brilliance (Beam current / emittance) Increase of transported beam currents Improvements of high current beam diagnostics / operation

GSI high current sources Filament driven Vacuum Arc driven High Duty factor Now let me switch to the main Point of my talk… By the plasma generation process, HC IS can be devided by… The Filament dr are… They produce the gaseous ions And work with chemically not agressive gases They desing to produce ME beams Both types are pulsed and have own advantages and disadvantages. MUCIS, MUCIS New, CHORDIS MEVVA, VARIS PIG Working material: Gases Metalls and Gases Metalls and Gases

Vacuum Arc Driven Sources VARIS (Vacuum Arc Ion Source) Optimized for Uranium (67% of 238U4+) Emission current density 170 mA/cm2  156 mA @ 32 kV 55 mA @ 131 kV 20 mA in front of the RFQ 9 mA behind the RFQ Improving the beam quality at plasma extraction Improvement of beam transport Lifetime of cathodes 3 Hz operation Another modification of Vac Arc S is VARIS It was designed by R. Holl And optimized for U-beam For the optimum working conditions it must be HOT

UNILAC modifications and the HE-linac Ion source and beam transport upgrade 4 Alvarez tanks, almost 40 years old  exchange by modern IH-structures Charge state stripper technology  higher charge states (high intensities) High intensity beam diagnostics

H-Mode Resonators for LINACs IH-RFQ 4-vane RFQ B-Field B-Field E-Field E-Field IH-Structure (interdigital H-type) CH-Structure (cross bar H-type)

The FAIR Proton Injector Beam Energy Beam Current (design/oper.) Beam Pulse Repetition Rate Frequency Norm. Emittance at output Momentum Spread Beam Loading (peak) RF Power (peak) Klystron (3 MW Peak Power) Solid State Amplifier (50 kW) Total Length (RFQ + CH) 70 MeV 70 / 35 mA 36 µs 4 Hz 325.224 MHz 2.1 / 4.2 µm ≤ ± 10-3 4.9 MW 2.5 MW 7 3 ≈ 27 m CH-DTL Klystron

Charge state stripper for intense heavy ion beams Plasma stripper - Need to increase the gas density – plasma window for differential pumping - Or dense plasma channel separated by plasma windows C-foil stripper - short lifetime at highest intensities, but highest charge states gas stripper - High intensity capabilities, but lower charge states - Equilibrium charge state (efficiency) MIT Plasma window in a test setup at BNL

Emittance transfer Reminder: Bx/y:= (q/A)*Current / Emittancex/y emittance transfer from horizontal to vertical plane should help to increase the injection efficiency  transfer should preserve ex*ey

The Synchrotron Magnetic field and rf-frequency are ramped synchronous Dipole Magnetic field and rf-frequency are ramped synchronous to the particle energy. Quadrupole Sextupole bending correction focusing Magnets

SIS100 Quadrupole modules SIS100 169 high current (> 4 kA) quadrupoles SIS100 Injection/Extraction 4 low current (< 1 kA) quadrupoles A modules comprises: two quadrupoles, multipole corrector, steerer, chromaticity sextupole cryocollimator beam position monitor (BPM) Main Characteristics of the SIS100 quadrupole: B‘ = 27 T/m, Effective length = 1,3 m Complex system concerning: Girders, bus bars helium headers thermal shield, cryostat vacuum chamber

Cold BPMs Cold beam position monitors In SIS100 quadrupole modules Signal transfer from 4 K level to room temperature level QD BPM ST

Cryocatcher in Quadrupole Module L. Bozyk SIS100 Qaudrupole Cryostat

Dynamic Vacuum effect and collimation P. Puppel

Stacking of particles in the FAIR storage rings ptrans circulating, cooled beam t Circulation time rf-Barriers Creation of a gap for injection of additional particles New injected bunch Cooling

Fast bunch rotation in the CR Challenges: Short bunch from SIS100 (50 ns) For stochastic cooling de-bunching required High voltage (200 kV) required for fast rotation and reduction of momentum spread after production target Gap voltage 40 kV Length 1 m Rotation time ~ 100 ms

Summary FAIR accelerator developments High current ion sources and optimized beam transport Cavity development for LINACS – H-type cavities  p-Linac and HE-Linac Charge state stripper technologies Emittance transfer – injection into synchrotrons Cryogenic SIS100 modules and dynamic vacuum effect Accumulation of secondary particles via barrier bucket injection