1. PHYSICAL PROJECT OF BOOSTER FOR NICA ACCELERATOR COMPLEX Alexey Tuzikov, Nikolay Agapov, Andrey Butenko, Alexey Eliseev, Viktor Karpinsky, Hamlet Khodzhibagiyan, Alexander Kovalenko, Grigory Kuznetsov, Igor Meshkov, Vladimir Mikhaylov, Valery Monchinsky, Anatoly Sidorin, Alexander Smirnov, Grigoriy Trubnikov, Bogdan Vasilishin

2. 2 Introduction Booster is a standard element in the schemes of the synchrotron facilities of heavy ions. In our case its objectives are as follows.  1. Acceleration of the beams to an energy sufficient for the complete stripping of the ions Au 32+.  2. The accumulation of Au 32+ ions in different modes of ion source operation.  3. The relief of requirements for vacuum system in Nuclotron.  4. The increase of ion phase density in the Booster using electron cooling at the optimum energies close to 100 MeV / nucleon.  5. The refusal of the acceleration in collider. It should be noted that Nuclotron designed as an accelerator for nuclei up to calcium therefore these features can only be implemented in a synchrotron built for heavy ions like Au 32+.

3. 3 Position The iron yoke of the Synchrophasotron after the magnet winding is removed, gives a free tunnel of 4 x 2.3 m 2. The present layout of the Nuclotron and existing injection and extraction systems make it possible to place the Booster having 211.2 m circumference and four fold symmetry inside the Synchrophasotron yoke.

4. 4 Position Synchrophasotron yoke

5. 5 Main parameters Fold symmetry4 Quadrupole periodicity24 Injection/extraction energy Au 32+ 6.2/600 MeV/u Magnetic rigidity 2.2  25.0 T·m Dipole field 0.16  1.8 T Pulse repetition rate0.25 Hz Magnetic field ramp1 T/s Intensity limit2.5∙10 9 particle per pulse Au 79+ beam intensity (after stripping)1.5×10 9 Vacuum10 -11 Torr

6. 6 Main parameters Cycle diagram

7. 7 Lattice FODO lattice Dipoles Number of dipoles40 Maximum magnetic field, T1.8 Effective field length, m2.2 Bending angle, deg9.0 Curvature radius, m14.09 Booster superperiod lattice Quadrupoles Number of quadrupoles48 Field gradient, T/m19.7/-20.3 Effective field length, m0.4

8. 8 Lattice FODO lattice Booster superperiod lattice functionsWorking diagram

9. 9 Superconducting magnets Dipole magnet in cryostatHollow superconducting cable 1 - copper-nickel tube, 2 - NbTi strands, 3 - strands binding by wire, 4 - kapton tape, 5 - glassfiber tape

10. 10 Injection The injection scheme supposes few modes of ion accumulation depending on operation mode of ion sources:  One turn injection  Four (three) turn injection  Twice (triple) repeated one turn injection  Multi turn injection with coupling resonance and electron cooling

11. 11 Injection Four turn injection

12. 12 Acceleration №Parameter 1.RF range0.5 – 2.4 MHz 2.Harmonic4/1 3.3.Cavity count2 4.4.Minimum voltage amplitude at adiabatic capture100 V 5.5.Voltage amplitude at acceleration10 kV The Booster RF cycle is composed of four parts:  the adiabatic trapping at fixed frequency (flat bottom),  the beam acceleration at the forth harmonics of the revolution frequency up to 100 MeV/u and debunching,  the beam bunching at the first harmonics of the revolution frequency together with the electron cooling,  the beam acceleration at the first harmonics of the revolution frequency up to 600 MeV/u.

13. 13 Acceleration II IV Е k /u (MeV) Time III 0.48 s~ 1.0 s0.98 s I 6.2 100 600

14. 14 Electron cooling The Booster electron cooling system is aimed to form required optimal phase volume of the bunch for their further acceleration in Nuclotron. The maximum designed electron energy is 60 keV. Numerical simulations of the cooling process showed that the cooling section of 4 m of the total length and electron current of 1 A provides required ion beam parameters at the ion energy of 100 MeV/u. The parameters are typical for conventional electron cooling systems, the energy corresponds to minimum range of the RF frequency variation (0.6  2.4 MHz) during the Booster working cycle. To adjust the cooling section with the SC magnetic system at minimum length, one plan to use a superconducting solenoid for the electron beam transportation, that is main technical peculiarity of the Booster cooler.

15. 15 Electron cooling Electron cooler: working design Electron gun Electron collector General view of the electron cooler 1945

16. 16 Extraction  Fast extraction system consists of kicker magnet and superconducting Lambertson Magnet (steel septum).  Slow extraction includes 4 quadrupole and 4 sextupole lenses, electrostatic septum and septum magnet. Minimum emittance of extracted beam will be provided by Hardt condition and dynamic bump.

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