Beam test of slow extraction from the ESR A. Dolinskii, July 5th

The goal is slowly to extract decelerated beam (at energy of 2-5 MeV/u) from the ESR. Ion-optical simulations have been done to find out which manipulations are needed for slow extraction. Test run with Ar beam at energy of 100 MeV/u has been performed to proof the principle possibility of the slow extraction from the ESR.

ESR layout Circumference, C, m.............................108 E01KS3 E01KS2 E01KS1 E01KS4 Circumference, C, m.............................108 Max.rigidity, Tm......................................10 Transition energy,.................................2.7 Tunes, Qx/Qy..........................2.27 / 2.23 Trans.acceptance (mm mrad) ....................................300 / 100 Mom. acceptance, %...................................3 Num. superperiods......................................2 Lattice type....................Doublet / Triplet Vacuum chambers h/v mm in dipoles.............................. 220 / 70 in quadrupoles...................300 / 300 Ext.septum Inj.septum Electrostatic septum E02KS4 E02KS1 E02KS2 E02KS3

Particle trajectories between ES and MS Extraction septum magnet Injection septum magnet Electrostatic septum

Equilibrium orbit for dp/p=-0.8% ex = 1 mm mrad E01KX4 Inj.septum Ext.septum E.septum

Resonance conditions * The ESR optic is set to have tune Qx=2.325 sextupole setting * The ESR optic is set to have tune Qx=2.325 * Two sextupole magnets are activated to excite 3rd order resonance (the other 6 sextupoles are used to restrain the chromaticity to small values; step size on the ES is 7 - 9 mm * Extraction is performed by ramping of one quadrupole family to move the betatron tune from 2.325 to 2.3333 E01KS3 E01KS4 E02KS1 E02KS2 E02KS3 E02KS4 E01KS1 E01KS2 -0.065 +0.103 0.230 -0.230 k=0.5(B''Leff)/BR Monte-Carlo particle tracking by the PTRACK code

Cycle for the slow extraction 40Ar+18 1. Electron cooling is off 2. Set the electrostatic septum to have a kick angle of in between (-1.5, -3) mrad 3. Set corrector magnet E01KX4 to -1 mrad 4. Set the ESR optic to have tune Qx=2.325, Qy=2.29 5. Beam Injection at E=100 MeV/u 6. Shift orbit to dp/p=-0.8% by magnet ramping to energy 103.6 MeV/u 7. Ramping of sextupole magnets 8. Ramping of one quadrupole family to get Qx=2.3333

Nonlinear field influence To direct particles to the Extraction Septum Magnet (ESM) the Electrostatic Septum (ES) magnet was adjusted to 0.8 mrad kick instead of 2 mrad as it was predicted by calculations ESM 6 dipole magnets have strong nonlinear field components, which influence on the particle trajectories. ES

(with field errors in the ESR dipole magnets) Nonlinear simulation (with field errors in the ESR dipole magnets) the ESR dipole sextupole component of B''Leff=0.543* T/m is used in the MIRKO and PTRACK simulation.

Nonlinear approximation Kick angle by the Electrostatic Septum Theory: -1.5 – 3 mrad Measured -0.8 – 1.5 mrad The sextupole field of ESR dipole magnets changes the slope of the separatrix. In our case the separatrix slope is changed from -1 mrad to -2 mrad. This leads to the smaller kick angle, which the E.Septum should provide. without dipole sextupole field with dipole sextupole field

The test run extracted beam is seen on the illumination screen beam current during slow extraction

Further steps The efficiency of extracted beam must be defined Chromaticity correction is needed to minimize the beam loss. The extracted spill structure should be optimised in order to achieve the needed extraction particle rate (may be we can try to use knock-out method instead of quadrupole ramping). The slow extraction has to be performed for decelerated beam (energy of 2 – 5 Mev/u)