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L a y o u t o f V E P P -5 in je c tio n c o m p le x
M ain p aram eters of lin ear accelerators.
M ax. beam energy
M ax. num ber of electrons in the bunch
M ax. num ber of positrons in the bunch
M ax. pulse repetition rate
E nergy spread:
in electron bunch
in positron bunch
L ongitudinal bunch sigm a
RF
K lystron pulsed pow er
T otal num ber of klystrons
T otal pow er consum ption
510 M eV
11
10
9
10
50 H z
1%
3%
6 mm
2856 M H z
~ 63 M W
4+ 1
1 M W
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.
Movable positron target
Pulsed shifting
magnet
FC magnet
HV feedthrough
for FC magnet
First cell of
acc. 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.
10
1.8
10
Number of electrons in primary electron beam 5.0
4.5
4.0
N e+ *10
8
3.5
3.0
2.5
2.0
1.5
Y=0.1 1/GeV
1.0
0.5
0.0
0
10
20
30
40
50
BMAX (kG)
60
70
80
Electrons
Positrons
Рис. CCD. Изображение на люминофоре
Damping ring
Designed parameters of damping ring
Output beam energy
Max. number of particles in the bunch
Max. beam current
Max. extraction rate
Energy spread
Vertical emittance
Horizontal emittance
Longitudinal bunch sigma
RF
Dumping time (vert.)
Circumference of dumping ring
Beam power loses
510 MeV
2.0 1010
35 mA
1 Hz
0.07%
0.005 mm mrad
0.023 mm mrad
0.4 cm
700 MHz
17.5 ms
27.4 m
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.
D esign ed valu es of In jection C om p lex ou tgoin g b eam
p aram eters.
B eam energy
M ax. num ber of electrons in the bunch
M ax. num ber of positrons in the bunch
E xtraction rate
E nergy spread in the bunch
L ongitudinal bunch sigm a
V ertical em ittance
H orizontal em ittance
510 M eV
10
2.0 10
10
2.0 10
1 Hz
0.07%
0.4 cm
0.005 m m m rad
0.023 m m m rad
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.
Damping ring with injection and extraction channels
e+
e-
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.
1
Accelerating structure. 1 — regular cell, 2 — RF coupling device 3 — joint cell,
4 — joint diaphragm, 5 — stainless steel frame.
Detector of electron and positron beams.
Standard element of accelerating system: 1 — quadrupole lens, 2 —
accelerating structure, 3 — girder, 4 — ion pump, 5 — support.
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