Status of Hybrid target R&D at KEK-LINAC

T.TakahashiHiroshima University

March 2011ALPG11 Eugene

Collaborators:V. Strakhovenko O. Dadoun, R. Chehab, A.Variola, L. Rinolfi, O. Dadoun,T.Kamitani, T.Suwada, T.Omori, J.Urakawa,K.Furukawa, K.Umemori,M.Satoh,T.Sugimura,S.Kawada, T.Akagi, Y. Uesugi

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+

experimental site KEKB LINAC

Switch yard

８ GeV　 e-～ nc/bunchupto 25Hz single bunch

Setup

8GeV e- 1mm W crystal

Sweeping Magnet0.96T 0.75m

amorphous W8 mm18 mm

Analyzing magnet5 ~ 30MeV

pictures

e- 8GeV

W Crystal on the goniometer

Sweeping magnet

pictures

movable stage

amorphoustargets

thermocoupolesattached back end

The data• Hybrid

• Conventional

e 8GeV sweep mag

1mm W Crystal on axis (aligned to the beam) off axis (not aligned to the beam)

e 8GeV

amorphous W 1.75, 3.5, 5.25, 8, 18mm

temperatureat the end of the targets by thermocouplesand infrared camera

positrons fromthe targetmomentumanalyzed

g

posit

ron

yiel

d (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 0.117.7 0.4

1 2

2 22 21 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.

e+ yield

amorphous thickness [mm]

e+ d

etec

ted

[a.u

]P=20MeV

simulation and data normalized at 8mmneed to correct acceptance for precise analysis

0 2 4 6 8 10 12 14 16 180

5

10

15

ConventionalSimulationHybrid ON axisSimulationHybrid OFF axis

Temperature measurement w/ thermocouples

back plane of amorphous target thermocouple

approximately 1mm x 1mm

to fast data loggerread temperature each 10ms

bunch by bunch temperature variationPEDD information by thermocouple

temperature at equilibriumtotal energy deposit

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

Celsi

us)

Base temp. 23.3℃

DT～32℃

Preliminary

T vs total energy deposit

hybrid　 on axis

conventional

18mm

8mm

T at equilibrium has information for total energy deposit except for 18mm hybrid

target is thicker than shower max

hybrid off axis

T at

equ

ilibr

ium

(deg

)

bunch by bunch temperature rise

• bunch repetition 1Hz

combine all bunches to for statistics

~ 60 pulses for one data set

time , base T. adjustment

1sec

0 1 0 2( )/ ( )/0( ) (1 )sin(2 ( ))

t t t tT t T ae eb f t

Beam profile on amorphous

sx=2.0mmsy=2.3 mm

beam profilescrystal amorphous

3.2m

sx=2.0mmsy=2.3 mm

sx=0.42mmsy=1.54mm

beam divergencex～ 0.5mry～ 0.24mr PEDD estimation

bunch by bunch temp.• dT provides a measure of PEDD

hybrid　 on axis

conventional

hybrid off axis

Simulation

Measured

summary• we took systematic data for hybrid target R&D

– yield from various target thickness– momentum 5, 10, 20 MeV– energy deposit/temperature

• at equilibrium • single bunch variation• beam profile

• Correction for detector acceptance – hopefully next a couple of months

Evaluation of the hybrid scheme as a positron source

Data analysis Done

supplements

momentum dependence

e+ momentum[MeV]

e+ d

etec

ted

[a.u

.] hybrid on axis conventional

0 5 10 15 200

5

10

0 5 10 15 200

5

10

18mm

8mm

5.25mm

3.5mm

1.75mm

Beam profile on the cryltal

sx=0.42mmsy=1.54mm

adjust time and base line

Time

Tem

p

Time

Tem

p.

variation base temp. for 1 min.

clock difference

just overlay 50 pulses

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

KEKB LINAC• KEKB LINAC

• E(beam) : 8GeV Bunch Charge: ~nC

• Ideal for R&D for hybrid target

Experiences with crystal targets for KEKB