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Status of Hybrid target R&D at KEK-LINAC
T.TakahashiHiroshima University
LCWS/ILC10Beijing
Collaborators:V. Strakhovenko O. Dadoun, R. Chehab, A.Variola, T.Kamitani, T.Suwada, T.Omori, J.Urakawa,K.Furukawa, K.Umemori,Sugimura,M.Satoh,T.Sugimura,S.Kawada, T.Akagi
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Outline
• Introduction– motivation– Principle
• Facility– KEKB linac – Setup
• Preliminary Results• Outlook
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Channeling Radiation e-
Crystals: converter from high energy electrons to low energy photons
photon energy (MeV)
#g crystal#g amorphous
relative intensity of phtons fromcrystal and amorphous tungsten
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Hybrid target for positron source
• Chehab, Variola, Strakhovenko Scheme for LC positron sources
Experimental study for further development
e-e+, e-, g g
e-
e+
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KEKB LINAC• KEKB LINAC
• E(beam) : 8GeV Bunch Charge: ~nC
• Ideal for R&D for hybrid target
Experiences with crystal targets for KEKB
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experimental site KEKB LINAC
e+ source
Switch yard
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Set up SiteLooking up from Down stream
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Setup
8GeV e- 1mm W crystal
Sweeping Magnet0.96T 0.75m
amorphous W8 mm18 mm
Analyzing magnet5 ~ 30MeV
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Around the crystal target
15f hole in the lead shielding
gs
All charged particles aredumped here when the Sweeping magnet ON
Shielding lead bricks
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pictures
e- 8GeV
W Crystal on the goniometer
Sweeping magnet
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pictures
movable stage
amorphoustargets
analyzer magnetand detector behindthis lead briks
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data shown today• Hybrid
• Conventional
e 8GeV sweep mag
1mm W Crystal on axis (aligned to the beam) off axis (not aligned to the beam)
8mm W amorphous
e 8GeVW amorphous 8mm or 18mm
temperatureat the end of the targets by thermocouples
positrons fromthe targetmomentumanalyzed
g
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posi
tron
yie
ld (a
rb. u
nit)
angle of crystal w.r.t. beam (mr)
rot. in vertical plain
esweep mag
8 mm
Rocking curve
1
2
3.4 0.1
17.7 0.4
1 22 22 2
1 2
( )f A B Const
same for horizontal rotation
Preliminary
factor 3 enhancement
it was 1.2 in 2009 Sep datawe found the detector was saturated in previous exp.
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e+ yield (20MeV)
hybridon axis
hybridoff axis
conventional8mm
conventional18mm
3.4 enhansement
e+ yield (ADC counts)
black: 1mm W crystal + 8mm W amorphous
red: conventional
Preliminary
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e+ yield (10MeV)
hybridon axis
hybridoff axis
conventional8mm
conventional18mm
3.4 enhancement
e+ yield (ADC counts)
black: 1mm W crystal + 8mm W amorphous
red: conventional
Preliminary
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Temperature measurementsAttach thermocouples behind the target.
Tthermal diffusion ~ 100ms for Tungsten
Slower diffusion via target holders
only recorded temperature after reaching equilibrium
Corresponds to TOTAL energy deposit on the targets
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Example ofTemperature Measurement
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30202530354045505560
Temperature of the 8mm amorphous target for the hybrid case
Time from Beam On (Minutes)
Tem
pera
ture
(deg
ree
Cels
ius)
Base temp. 23.3℃
DT ~32℃
Preliminary
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How they look like• e+ detected in hybrid configration
– on axlis/off axis ~ 3.5• hybrid on axis and conventional with 8mm W
– e+s are almost same• temperature rise of amorphous targets
– For 8mm tungsten• hybrid 32.1 ℃• conventional 24.7℃
– for 18 mm tungsten• hybrid 110.0 ℃• conventional 130.0 ℃
• e+ at 20 MeV and 10MeV– 20MeV/10MeV ~ 3.9Can we understand the these?
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Geant4 Simulation
• gs from crystal– put simulation date to Geant4
• crystal off aligned – 8GeV e- to 1mm amorphous + 8mm amorphous
off aligned case
lead bricks
B field8GeV e-
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G4 simulation: ALL e+ from targetscorresponds to 1000 e- injunction
P ( MeV)
# e+
/MeV
hybrid aligned
e- on 8mm target
hybrid not aligned
~ 3 enhancements
pt/pz ( mr)
hybrid aligned
e- on 8mm target
hybrid not aligned
hybrid v.s. conventional total number of e+ is larger for hybrid (factor 2) -> larger dEdX and then larger temperature rise for hybrid
lager angular distribution fof hybrid # of e+ in detector depends on acceptance of the detection system
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e+ after acceptance cut
p( MeV)
# e+
/MeV
e- on 8mm targethybrid not aligned hybrid aligned
# of e+ is same for hybrid and conventional consistent with the experiment
deffernece for on/off aligned crystal is about factor 3 almost same as the exp.
pt/pz < 50mr
hybrid not aligned
enha
ncem
ent
e+ yield at 20MeV and 10Mev
p( MeV)
factor 2 ~ 3 difference by simulation factor 4 difference in the exp.
no discrepancy asthe detection systemhas p dependent acceptance
hybrid aligned
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Positron Momentum AcceptancePe+ MeV/ c( ) × 10‐4 MeV/ c Sterad.( ・ )
5 1.08± 0.0310 2.47± 0.0715 3.80± 0.1020 4.81± 0.12
acceptance of the spectrometer has been studied with Geant simulation by colleagues of Tokyo Metropolitan University
0
1
N
NPP
0 ≤θ≤ 0.08 , 0 ≤φ≤2π , 0.8 P0≤ P ≤1.2P0
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Temperature and Energy Deposit
• Too soon for conclusion– consideration for heat dissipation is necessary
Total energy Deposit on Amorphous target [MeV/e]
Tem
pera
ture
rise
[K]
8 mm conventional
8 mm hybrid
18 mm hybrid
18 mm hybrid
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Summary• e+ detected in hybrid configration
– on axlis/off axis ~ 3.5• e+ yield for hybrid on axis and conventional
– e+s are almost same• e+ at 20 MeV and 10MeV
– 20MeV/10MeV ~ 3.9
• temperature rise of amorphous targets– energy deposit - temperature ,,, yet to be studied
Appeared to be understandable
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Status and outlook
• We successfully demonstrated positron generation with hybrid target
• Simulation study is underway • To understand feasibility for positron soucre
– Comprehensive understanding is necessary theoretically as well as experimentally
• Peak Energy Deposit Density as well as total energy loss• Positron yield with capture system• dependences on beam energy target thickness (crystal and
amorphous)
next beam time on April 10 , 11