1. Mitglied der Helmholtz-Gemeinschaft Automated adjustment of the electron beam line of the 2 MeV Electron Cooler at COSY March 11, 2015 | 17:15 | A.Halama Arbeitskreis Beschleunigerphysik 10: Beam and Accelerator Control

2. Mitglied der Helmholtz-Gemeinschaft Cooler Synchrotron COSY Protons/Deuterons Unpolarized and polarized Stochastic and electron cooling 2 Source: COSY operating documents Up to 2,8 GeV 184 m circumference

3. Mitglied der Helmholtz-Gemeinschaft Basics of Electron Cooling Principle analog to the thermodynamics of gas 3 Ion beam with a given temperature/ velocity distribution Ion beam and electron beam overlap in cooling section of cooler Temperature exchange via coulomb interaction Velocity distribution of ion beam decreases -> beam size decreases

4. Mitglied der Helmholtz-Gemeinschaft 2 MeV Electron Cooler Energy range: 25 keV – 2 MeV Max. Design Current: 3A Magnetic guiding field throughout entire beam line 4 Source: Proceedings of COOL2013, Mürren, Switzerland TUPM2HA01

5. Mitglied der Helmholtz-Gemeinschaft Heating Effects on Electron Beam Slight mismatched settings of magnetic elements and inhomogeneity due to manufacturing tolerances Effects on the beam are localized Cause change of transversal velocity (called Kicks) Kicks accumulate i.e. sum up with passage through the cooler 5

6. Mitglied der Helmholtz-Gemeinschaft Slight mismatched settings of magnetic elements and inhomogeneity due to manufacturing tolerances Effects on the beam are localized Cause change of transversal velocity (called Kicks) Kicks accumulate i.e. sum up with passage through the cooler 6 Heating Effects on Electron Beam

7. Mitglied der Helmholtz-Gemeinschaft Kick Transmission by Dipole Correctors (EDIPs) 7 Source: Proceedings of COOL2013, Mürren, Switzerland TUPM2HA01

8. Mitglied der Helmholtz-Gemeinschaft Larmor Radius Measurement Electron trajectory with larmor rotation 8 Logging beam position at a localized BPM Increase of magnetic field strength leads to compression of larmor spiral Phase of spiral at BPM is changing accordingly

9. Mitglied der Helmholtz-Gemeinschaft Larmor radius equals 0 at the ideal dipole setting. 9 Model of Larmor Radii Distribution vs Dipole Setting

10. Mitglied der Helmholtz-Gemeinschaft Experimental Verification of the Model 10 96 Larmor radii measured for different dipole settings Absolute minimum can be seen clearly. Determination coeffizient of model fit: R² = 0.988

11. Mitglied der Helmholtz-Gemeinschaft Algorithmic Compensation Strategy Example of the procedure „strict“. Used setting: 2 Iterations with 5 different dipole settings 11

12. Mitglied der Helmholtz-Gemeinschaft Test of the adjustment procedure 12 Duration of the procedure: 8 minutes r 1 = 379 µm | r 6 = 59,1 µm | r 11 = 11,8 µm Beam position data from the procedure

13. Mitglied der Helmholtz-Gemeinschaft Conclusion Heating effects cause larmor motion development Given larmor radius can be measured in the main solenoid Pair of dipole magnets transmit properly designed kick Model to describe radii distribution was proposed and successfully tested Compensation procedures were algorithmic developed Procedure was tested and proves reliability 13

14. Mitglied der Helmholtz-Gemeinschaft Outlook Up until now: Manual orbit adjustment Larmor rotation compensation only for one beam line section Goal: Automated beam line adjustment for all magnetic elements Automated orbit adjustment Automated larmor rotation compensation Also by decreasing/ removing heating effects directly Therefore utilize approx. 30 corrector magnets and the guiding magnets 14

15. Mitglied der Helmholtz-Gemeinschaft Sources: Acknowledgement: V. Parkhomchuk, V. Reva, M. Bryzgunov et. al, Proceedings of COOL2013, Murren, Switzerland (TUPM2HA01) The author is greatful for the advice and fruitful discussions with V.Reva, M.Bryzgunov and his supervisor V.Kamerdzhiev. Further the author thanks the COSY operatiors for the cooperation. 15

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18. Mitglied der Helmholtz-Gemeinschaft 18 Formulas:

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21. Mitglied der Helmholtz-Gemeinschaft Accumulation and Compensation of the Larmor Rotation: 21

22. Mitglied der Helmholtz-Gemeinschaft 22 Numerical result of the automated procedure FolgeI EDIP,VER / AI EDIP,HOR / Ar Larmor / µm 1-0,014-0,016379,39 2-0,0281,487242,27 31,473-0,015364,01 4-0,028-1,519500,44 5-1,528-0,016424,65 60,8963,65159,11 70,8975,15557,41 82,3983,652111,35 90,8972,148178,09 10-0,6053,652134,25 111,074,5811,80

23. Mitglied der Helmholtz-Gemeinschaft Reduction of velocity distribution Beam envelope without cooling 23 Beam envelope with coolingLongitudinal velocity destributions

24. Mitglied der Helmholtz-Gemeinschaft Measuring the larmor radius (Animation) 12

25. Mitglied der Helmholtz-Gemeinschaft Table of Contents  Introduction to COSY and the 2 MeV electron cooler  Basics of electron cooling  Difficulties and motivation  Kicks causing larmor rotation  Measuring the larmor radius  Kick compensation using dipoles  Model of larmor radii distribution vs. dipole currents  Experimental test of the model  Proceeding of the automated adjustment  Test and results  Conclusion  Outlook 25