Layout of VEPP-5 injection complex

Main parameters of linear accelerators. Max. beam energy 510 MeV Max. number of electrons in the bunch 1011 Max. number of positrons in the bunch 109 Max. pulse repetition rate 50 Hz Energy spread: in electron bunch 1% in positron bunch 3% Longitudinal bunch sigma 6 mm RF 2856 MHz Klystron pulsed power ~63 MW Total number of klystrons 4 + 1 Total power consumption 1 MW

Linacs hall

300 MeV driving electron linac

Positron linac

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.

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.

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

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:

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.

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

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.

VEPP-5 positron production system assembly.

FC magnet

Movable positron target

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Pulsed shifting magnet

HV feedthroughfor FC magnet

First cell ofacc. structure

Positron production system of Injection complex

Positron production target assembly.

VEPP-5 FC magnet

The dependence of positrons number upon the maximum field in FC.

Driving electron beam energy - 265 MeV.Number of electrons in primary electron beam -

101.8 10

Y=0.1 1/GeV

Рис. CCD. Изображение на люминофоре

PositronsElectrons

Damping ring

Designed parameters of damping ring Output beam energy 510 MeV Max. number of particles in the bunch 2.0 1010 Max. beam current 35 mA Max. extraction rate 1 Hz Energy spread 0.07% Vertical emittance 0.005 mm mrad Horizontal emittance 0.023 mm mrad Longitudinal bunch sigma 0.4 cm RF 700 MHz Dumping time (vert.) 17.5 ms Circumference of dumping ring 27.4 m Beam power loses 5.3 keV

SR light from damping ring (electrons, 300 MeV)

Injection and extraction of 300 MeV electron beam.

Electron beam before DR. Electron beam after DR.

Designed values of Injection Complex outgoing beam parameters.

Beam energy 510 MeV Max. number of electrons in the bunch 2.0 1010 Max. number of positrons in the bunch 2.0 1010 Extraction rate 1 Hz Energy spread in the bunch 0.07% Longitudinal bunch sigma 0.4 cm Vertical emittance 0.005 mm mrad Horizontal emittance 0.023 mm mrad

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.

e+

e-

Damping ring with injection and extraction channels

e+

e-

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.

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.

Bypass scheme for electron beam

Movable positron production target holder.

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.

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.

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

Distribution of transverse momentum for positrons at the target exit. This distribution obtained by GEANT code for 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 from the target is equal to 2,4·105. This distribution has a

weak dependence upon the incoming electron beam energy.

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.

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.

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

1

Detector of electron and positron beams.

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