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

2. 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.

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

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

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

6. 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 mm
* Extraction is performed by ramping of one quadrupole
family to move the betatron tune from to
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

7. 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 MeV/u
7. Ramping of sextupole magnets
8. Ramping of one quadrupole family to get Qx=2.3333

8. 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

9. (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.

10. 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

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

12. 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)