High Intensity Positron source

1. High Intensity Positron source Pavel Logachev, BINP, Novosibirsk.

4. Linacs hall 300 MeV driving electron linac

5. Positron linac

6. Conventional positron production system layout. 1 — electron source, 2 — RF accelerating structure, 3 — triplet of quadrupoles, 4 — positron production target, 5 — matching device, 6 — first accelerating structure of positron linac, 7 — quadrupole lens.

7. Positron system testing:1 — electron gun, 2 — sub harmonic bunching system, 3 — focusing coil, 4 — accelerating structure, 5 — solenoid coil, 6 — quadrupole lens, 7 — corrector, 8 — spectrometer, 9 — bending magnet, 10 — positron production system and first accelerating structure of positron linac.

8. Positron bunch profile at different moments of time. Results of simulation.

9. Phase space diagrams for positron beam (black contour lines): a) just after the target, b) after the matching device. White zone corresponds to the acceptance of further linear accelerator. These results of simulation were obtained for axial-symmetric magnetic field of matching device:

10. Results of magnetic measurements for matching device of VEPP-5 Injection Complex: upper curve – longitudinal magnetic field on the geometrical axis of the device, lower curve – transverse component of magnetic field on the geometrical axis Z.

11. Examples of positron trajectories in matching device with axial symmetry of magnetic field:

12. Positron production test bench: 1 — main DC solenoid, 2, 3, 4 — quadrupole lenses, 5 — steering magnet, 6 — separating magnet. Positron beam intensity as a function of distance from the target in the positron production test bench. Designed positron beam intensity at the end of linac.

13. VEPP-5 positron production system assembly. Movable positron target - e Pulsed shifting magnet FC magnet HV feedthrough for FC magnet First cell of acc. structure

14. Positron production system of Injection complex

15. Positron production target assembly.

16. VEPP-5 FC magnet

17. The dependence of positrons number upon the maximum field in FC. Driving electron beam energy - 265 MeV. Number of electrons in primary electron beam - Y=0.1 1/GeV

18. Electrons Positrons Рис. CCD. Изображение на люминофоре

19. Damping ring

21. SR light from damping ring (electrons, 300 MeV)

22. Injection and extraction of 300 MeV electron beam. Electron beam before DR. Electron beam after DR.

26. Transverse positron beam sizes in 500 MeV linear accelerator of VEPP-5 Injection complex. Simulations were done using ELEGANT code. Positron bunch intensity in positron linac as a function of distance from positron production target simulations were done using ELEGANT code.

27. Damping ring with injection and extraction channels + e e + - e - e

28. Present status and plans: • Positron production system was successfully tested at designed parameters. • Damping ring is ready for commissioning with 500 MeV electron beam. • 500 MeV electron beam will be available from linac in December 2008. • 500 MeV positron beam will be available from linac in 2009.

29. 11 Our goal is 10 positrons per second at 500 MeV from damping ring

30. Isochronous achromatic U-turn of electron beam: 1 — phosphor screen, 2 — focusing triplet, 3 — Faraday cup, 4 — positron target, 5 — quadrupole lens, 6 — bending magnet.

31. Bypass scheme for electron beam Movable positron production target holder.

32. Scheme of VEPP-5 matching device. Arrows show the surface current directions. 1 — water cooling channels; 2 — vacuum insulating gap (gap width is 0,2 мм); 3 — primary coil; 4 — positron production target, 5 — input aperture of the first accelerating structure.

33. Schematic surface current distributions(i)on the one of the surfaces of insulating gap (3) for two different variants of matching magnet design: a) with big transverse component of magnetic field on the axis, b) with small transverse component of magnetic field on the axis. Different length of primary coil (2) and conical cavity (4) helps to reduce the magnetic field asymmetry.

34. Рис. Distrib.Энергетическое (а) и угловое (б) распределение позитронов, родившихся в конверсионной мишени. Спектры получены с помощью программы GEANT […] (кол-во падающих на мишень электронов — 2·105, энергия электронов — 280 МэВ, длина танталовой мишени — 12 мм). Общее число вышедших из мишени позитронов — 2,4·105 (расхождение с формулой 2 объясняется тем, что приблизительно половина родившихся в ливне позитронов анигилирует внутри мишени). Спектры слабо зависят от энергии первичного электронного пучка

35. Distribution of transverse momentum for positrons at the target exit. This distribution obtained by GEANT codefor 12 mm length of tantalum target, 280 MeV of incoming electron beam energy. For 2·105 electrons in the bunch, the number of positrons produced at the exit fromthe target is equal to 2,4·105. This distribution has a weak dependence upon the incoming electron beam energy.

36. Phase space plot for positron beam at the exit of solenoid. White area corresponds to acceptance of solenoid. (Results of simulation for typical parameters of VEPP-5 Injection Complex). Horizontal momentum distribution for positrons: a) at the beginning of solenoid, b) at the solenoid exit. Results of simulation for typical parameters of VEPP-5 Injection Complex.

37. Positron system with first accelerating structure. 1 — positron production target, 2 — DC solenoid, 3 — AMD, 4 — DC coil, 5 — main solenoid external coil, 6 — main solenoid internal coil, 7 — accelerating structure, 8 — matching quadrupole, 9 — ion pump, 10 — , 11 — steel girder, 12 — support.

38. 1 Accelerating structure. 1 — regular cell, 2 — RF coupling device 3 — joint cell, 4 — joint diaphragm, 5 — stainless steel frame.

39. Detector of electron and positron beams.

40. Standard element of accelerating system: 1 — quadrupole lens, 2 — accelerating structure, 3 — girder, 4 — ion pump, 5 — support.