Peter Spiller, Heavy Ion Fusion Symposium Princeton June 7-11, 2004

1. Accelerator Plans at GSI for Plasma Physics Applications Peter Spiller, Heavy Ion Fusion Symposium Princeton June 7-11, 2004

2. Plasma Physics Requirements • 1 . Maximum number of particles • : 1-2 x 1012 /cycle) • 2. Beam energy • : 400 – 2715 MeV/u • 3 . Short, single bunch on target • : 25 - 90 ns • Focal Spot • : 1 mm ?

3. The Future Accelerator Facility - FAIR SIS 100/300 SIS18 UNILAC HESR Gain Factors • Primary beam intensiy : x 100 – 1000 • Secondary beam intensiy : x 10000 • Ion energy : x 15 • New: cooled pbar beams (15 GeV) • Special : intense cooled RIBs • Parallel operation and time sharing Super FRS CR NESR

4. Uranium Beam Intensity – Status SIS18 Highest accelerated U73+ - beam intensity : 4.5 x 109 (Dec. 2003 MEVVA ion source and MTI) Limit untill mid of 2002 by low UNILAC beam currents Significant progress with source und UNILAC developments Status of the uranium currents in TK9 (SIS Injection) : U73+1 mA U28+ 2.7 mA Expected number of particles in SIS : U73+ 6 x 109 (MIT x15) U28+4 x 1010 (MIT x15)

5. Two Stage Synchrotron Concept • High Intensity- and Compressor StageSIS100 with fast-ramped superconducting magnets and a strong bunch compression system. BR = 100 Tm - Bmax = 2 T - dB/dt = 4 T/s Intermediate charge state ions e.g. U28+-ions up to 2715 MeV/u Protons up to 30 GeV • High Energy- and Stretcher StageSIS300 with superconducting high-field magnets and stretcher function. BR = 300 Tm - Bmax = 6 T - dB/dt = 1 T/s Highly charges ions e.g. U92+-ions up to 34 GeV/u Intermediate charge state ions U28+- ions at 400 to 2715 MeV/u with 100% duty cycle

6. SIS100/300 Design Parameters SIS100 SIS300 First Stage Second Stage Acceleration + Acceleration + Compression Stretcher

7. SIS100/300 Underground Tunnel -24 m 5 m

8. SIS100 Magnet R&D Nuclotron Cable Nuclotron Dipole • Bmax = 2 T – B’ = 4T/s • Window frame magnet with s.c. coil • Main task : Reduction of AC losses during ramping by improved iron yoke design (40 W/m > 13 W/m) Significant R&D progress achieved on dynamic losses and field quality > Talk G. Moritz

9. Power Net Connection Step 1 : (summer 2005) : Separate 110kV connection to Urberach - upgrade Leonhardstanne Today : GSI in series connection with Darmstadt Step 2 : upgrade Leonhardstanne by an additional 63 MVA Transformer Contracts prepare

10. Power Oscillations Torsion resonance nucl. power plant Biblis B (monitoring and forced disconnection)

11. RF Systems in SIS100 • Dual Harmonic Acceleration Systems SIS100 21 ferrite loaded Cavities - Va,tot 400 kV Frequency Range : 1.15 – 2.67 MHz (h=10) • Compression Systems SIS100 25 MA-loaded Cavities - Vc,tot = 1 MV Frequency Range : 465 kHz (±70) (h= 2) • Barrier Bucket Systems SIS100 (precompression and stacking) Broad band MA-loaded Cavities - Vb = 2x 15 kV Frequency = 2.4 MHz Total Length of RF-Systems ~ 150 m ( 14 % of circumference )

12. Bunch Compression in SIS100 Short pulses for optimum target matching PP and Super-FRS and fast cooling in CR on Target Phase space tomography of compression experiments in SIS18

13. Bunch Compression Studies

14. Magnetic alloy R&D Amorphous, cobalt based MA core Nanocrystalline, iron based MA core 40 KV per gap In order to minimize the visible impedance, semi conductor high power switched must shorten the gap Prototype cavity for SIS18 In order to optimize shunt impedance and inductivity a large variety of scaled (1:5) nanocristaline (Fe based) and amorphous (Co based) core materials were investigated

15. MA-material Properties Space limitation enforce high voltage per meter length high power requirements high performance MA-cores R&D with : Honeywell, Vakuumschmelze, Hitachi and Radiotechnical Institute Improved ribbon thickness, filling factor and manufacturing techniques 20 amorphous (Vakuumschmelze VITROVAC 6030F) and 20 nanocrystalline (Hitachi FT-3L) cores ordered Significant improvement of quality factor Qf from 3.6 to 5.5 GHz !

16. Lattice Structure of SIS100 General optimization criteria for high current, U28+-operation and compression • Maximum beam acceptance („small“ aperture magnets for fast ramping) • Dispersion free straight sections (no transv. Longit. coupling in rf systems) • Low dispersion in the arcs (momentum spread during compression) Dx = 2.5 m • Six superperiods (space for large tune shift and long storage time)

17. Life Time of U28+- ions High intensity, heavy ion beams require intermediate charge states ( U73+ > U28+ ) • Life Time of U28+ is significantly shorter than of U73+ • Life Time of U28+ depends strongly on the residual gas pressure and gas components • Desorption Processes degenerate the residual gas pressure • Beam losses increase with number of injected ions (vacuum instability)

18. Pressure Dynamics Fast variations (time scale s) Slow variations (time scale sec.)

19. New Design Concepts Principal GOAL : No additional load for the UHV system during beam operation. 1. From all loss mechanisms, only particles which are further stripped by collisions with the residual gas atoms are able to reach the beam pipe within one lattice cell ! Each lattice cell must be designed as a charge separator. The „stripped“ beam (U29+) must be well separated from the reference beam. The low dispersion function in the SIS100 arcs comlicate this issue. 3. The main lattice structure optimization criteria is the collimation efficiency for U29+-ions.

20. New Design Concepts The collimation efficiency for U29+ - ions must be 100%. Mainly single (no multiple) ionized ions are generated. The 100% collimation efficiency must be achieved with collimators at maximum distance from the beam edge. No significant acceptance reduction shall be caused by the collimators. 7. No ionization beam losses shall occure on cold and NEG coated surfaces. 8. By a dedicated design, the effective desorption rate of the collimators shall be almost zero.

21. Multiple Ionisation Ref. : R. Olsen et.al. SIS18 injection energy SIS100 injection energy

22. Lattice Optimization CDR triplet lattice (Acceptance : 100 x 55 mm mrad) Doublet lattice with 3 dipoles per cell (Acceptance : 170 x 50 mm mrad )

23. Collimation Efficiency

24. (Present ) Limits of the Concept • The collimation concept is suitable for uranium operation. • The collimation efficiency for other ions species is lower. • The vacuum pressure is effected by uncontrolled losses and gas desorption. • Therefore beam tubes of the magnets shall be cold and act as cryopumps. • Without active cooling, the dipole tube temperature is about 50K. • Additinal cooling channels must be foreseen at least in the drift- and • quadrupole chambers. • NEG coating of SIS100/300 magnet chambers is not possible since baking would be required. • about 700 m of the chambers will be cold an act as cryo pumps

25. Collimation Concept wedge collimator at 80 K cold, pumping sec. chamber at 4,5 K

26. Prototype Desorption Collimator Wedge collimator, Secondary chamber + cryo pump The collimations system must controle the desorption gases (eff = 0)

27. Vacuum Stabilization • Short cycle time and short sequences SIS12 :10 T/s - SIS100 : 4 T/s (new network connection in preparation) • Enhanced pumping power (Actively cooled magnet chambers 4.5 K (750m), NEG coating (250m) (local and distributed) • Localization of losses and controle of desorption gases Prototype desorption collimator installed in S12 • Low-desorption rate materials Desorption rate test stand in operation cryo pump increased pressure ion beam wedge collimator

28. Summary of UHV issues • A promising concept for the high current U28+ operation exists. • The situation of the SIS12 booster operation is more critical since the lattice • is not optimized for collimation and multiple ionization is more probable. • No consistent concept for the operation with other heavy (e.g. Au, Pb) ions • is worked out. Collimation efficiency is lower and fractions of the beam may • get lost uncontrolled. Ionisation cross section drop for lighter ions.