1 Input e beam from Monte Carlo EGS simulation s Field RF cavity PoissonSuperfish Focusing solenoid PoissonSuperfish Beam dynamics General Particle Tracer Marcin Staszczak ID: 472859
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Slide1
6-th GBAR collaboration meeting, 18-19 April 2012
1
Input e+ beam from Monte Carlo (EGS) simulations - Field RF cavity – Poisson/Superfish- Focusing solenoid – Poisson/Superfish- Beam dynamics – General Particle Tracer
Marcin StaszczakNational Centre for Nuclear Research (Poland)Division of Accelerator Physics and Technology
Positron deceleration using RFSlide2
6-th GBAR collaboration
meeting, 18-19 April 2012
2 e+ production from primary e- 10 MeV beam on 1mm W target
- e+ production from primary e- 5 MeV beam on 0.5mm W target
Results of Monte
Carlo simulations
:Slide3
6-th GBAR collaboration meeting, 18-19 April 2012
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e+ production (10 MeV)
Mean energy ~ 2 MeVMost probable energy ~ 0.9 MeV
Primary beam e
-
- energy 10 MeV hits 1mm W target.
The total production efficiency ~ 0.16%
Energy spectrum of produced e+ after living the target:
Energy [MeV]
NSlide4
6-th GBAR collaboration meeting, 18-19 April 2012
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e+ production (10 MeV)
Angle distribution of e+ behind the target:
Spatial distribution of e+ behind the target. Almost identical as the primary electron beam:
N
x coordinate
(for y=0) [cm]Slide5
6-th GBAR collaboration meeting, 18-19 April 2012
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e+ production (5 MeV)Primary beam e- - energy 5 MeV hits 0.5mm W target.
The total production efficiency ~ 0.012%Energy spectrum of produced e+ after living the target:
Mean energy ~
1
MeV
Most probable energy ~ 0.
6
MeV
Energy [MeV]
NSlide6
6-th GBAR collaboration meeting, 18-19 April 2012
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RF cavities2 or 3 cavities (gap/L = 0.54) placed one after another were considered.
Different positions of cavities and focusing solenoid were tested.
L=45.7mm
L=41mm L=18mmSlide7
6-th GBAR collaboration meeting, 18-19 April 2012
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Focusing solenoidThere were analyzed 2 versions - shorter and longerMax Bz field ~ 0.7 T
Lower and higher values of magnetic field were also considered.
Additional compensating
coil was usedSlide8
6-th GBAR collaboration meeting, 18-19 April 2012
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Focusing solenoidSlide9
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationTo set the proper values of decelerating E field one can start from mono-energetic e+ beam 0.9MeV
Deceleration and acceleration by 2 RF cavitiesSlide10
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationThe goal is to decelerate as many positrons as possible,
close to the peak energy 0.9MeVUnfortunately the beam is divergent in all directions. Slide11
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationFocusing solenoid (without RF field) – shorter version
Bz ~ 0.7T
B
z
~ 7T
Slide12
6-th GBAR collaboration meeting, 18-19 April 2012
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Bz ~ 7T
Bz ~ 0.7T
RF positron deceleration
Focusing solenoid (without RF field)
–
longer
version Slide13
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationPositron energy along the z axis
Bz ~ 0.7T
B
z
~ 7T
Slide14
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationBz ~ 0.7T, cavities start 100mm after the targetSlide15
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationBz ~ 0.7T, cavities start 1mm after the targetSlide16
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationEnergy spectrum, bin width E = 40 keVSlide17
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron deceleration
Eav
N
before deceleration
N
after deceleration
20
keV
0
6
60 keV
0
4
100 keV
0
4
140 keV
0
5
180
keV
270
7
220 keV
702
4
260 keV
1368
8
Only about 10
-4
of all positrons are decelerated below 100keV
.
To get more accurate data of deceleration efficiency further optimizations of decelerating and focusing fields with higher number of initial particles have to be performed.Slide18
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationThe beam aperture was small about 10mm
After increasing the radius acceptance more
positrons
are focused and decelerating cavities can be
placed farther
.
This is the next step
that
will
be considered Slide19
6-th GBAR collaboration
meeting, 18-19 April 2012
19RF positron deceleration
First results with wider aperture at the beginning
and RF cavities at the end
:Slide20
6-th GBAR collaboration meeting, 18-19 April 2012
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RF positron decelerationCONCLUSIONS
Preliminary studies have been performed.Deceleration has been observed. Pulsed positron beam in effect.
Efficiency is still low.
Main problem is geometry and positron divergence living the target.
More optimizations and further simulations must be performed.
Higher initial electron energies should be considered
.