Channeling Experiments with Electrons at the Mainz Microtron MAMI

1. Motivation2. Channeling Experiments with Positrons @BTF Frascati3. Channeling Experiments with Electrons @MAMI Mainz4. Measurements of the Dechanneling Length5. A Planar Channeling Experiment with Electrons using a

Periodic Graded Composition Strained Layer SiGe Target6. Conclusions

Channeling 2008, Erice, Italy, Oct. 2008 W. Lauth, University of Mainz, Germany

Undulator Radiation at Positron/ElectronChanneling in a Single Crystal

A. Solov’yov, A. Korol, W. Greiner et al.

Positron Channeling in Si-Undulator Crystal

2cos

U

x A z

A = 9 Ǻ, U = 50 µm,

20.133

U

K A

U

e+

600 MeV

x

z

2

2 2 2 2

4

(1 / 2 ( ))

at 0, and first order 1

67.9 keV U x y

x y

ck

K

k

Photon energy

NU = 4

Beam Energy E = 600 MeV, = 1175.2

Channeling Experiments withPositrons @BTF Frascati

Beam Test Facility (BTF)

Emittance: x = y = 10 mm mrad

Divergence: 'x = 'y = 2 mrad

Beam Spot Size: x = y = 5 mm (rms)

Energy: 25 – 600 MeV

Particles: 1 – 1010 per pulse

Repetition rate: 50 Hz

Slit for Energy Definition

ConversionTarget

800MeVElectrons, Positrons from Linac

(See Poster Lina Quintieri)

( 0.27 mrad)C

ExperimentalHall

250 mm

2" NaI Detector

e+

Pb beam dump

Pb shield

Be Window d = 0.5 mm

Mylar Window d =0.04 mm

Goniometer

with Si-

Crystal

Plastic Scintillator

d = 2600 mm

350 m

m

Experimental Setup @ BTF

Experimental Result

0 20 40 60 80 100 120 140 1600

2

4

6

8

10

12

14

NaI S

ignal [a

.u.]

(norm

aliz

ed o

ver

beam

inte

nsity)

[mrad]

Target Chamber

DetectorsTo Beam Dump

BTF HallAdditional

45° Magnet

Existing 45° Magnet

Improvement of the Beam line

Experiments with Electrons

Dechanneling Length

Parameter:Energy: 180 MeV – 1507 MeVEmittance x=9 nm rad, y=0.5 nm rad

Energy Stability:

100µA cw e- - beam

X-ray

Research

The Mainz Microtron MAMI

Phase Contrast (Beamspot ~1µm)X-ray Interferometry (Magnetic circular Dichroism)PXR, TR, Channeling

W. Lauth et al., Coherent X-Rays at MAMI, Eur. Phys. J. A 28, (2006) 185.

57 10

ZnSScreen

Beam Dump

Top View

Experimental Setup (855 MeV e-)

-e44°

Si Target BM1

NaI Detector

(10" 10" length)

7.633 mPb 100 mm

20mm

Ionization

Chamber

Camera

Rad. Length

X0=10

Target Setup and Definition of Angles

-e

y y

x x

Top View

Azimuth

Polar Angle

Tilt Angle

-e

Video of the Beam Spot at the Dump Screen

Dum

pphot

os

NaI Raw Spectra

0 2 4 6 8

0,0

0,1

0,2

0,3

0,0

0,1

0,2

0,3

0,0

0,1

0,2

0,3

(111)

Eve

rnts

[1

/s]

[MeV]

(110)

(100)

0 2000 4000 6000 8000

0,01

0,1

1

(100)

(110)

Eve

rnts

[1

/s]

[keV]

<111>

<100>

<110>

off Channeling

(111)

Off Channeling

174µm Si Crystal

-20 -10 0 10 20 30 40 50 600

1000

2000

3000

4000

5000

6000

Eve

nts

Angle [mrad]

Energy – angle dependence of the radiation

ChannelingandQuasichanneling

E [MeV]

10

20

0.6 MeV

6 MeV

(011

)

(01

0)

(00

1)

(01

3)(0

11

)

-20 -10 0 10 20 30 40 50 60

350

400

450

500

550

600

650

Eve

nts

Angle [mrad]

Energy – angle dependence of the radiation

Pulser

High energyBremsstrahlung

E [MeV]

50

100

Coherent

Bremsstrahlung

Dechanneling length @ Ee =855 MeV

Photon energy: > 100 MeV (Bremsstrahlung)

(19.6 1)d µm

0 50 100 150

0

200

400

600

800

Eve

nts

Crystal Thickness [µm]

/

0( ) (1 )x df x f e

0 50 100 150 200 250 300

0

400

800

1200

1600

2000

Events

[1/p

A]

Crystal Thickness [µm]

Dechanneling length @ Ee =195 MeV

Photon energy: > 12 MeV (Bremsstrahlung)

/

0( ) (1 )x df x f e

(18.5 3)d µm

Dechanneling length @ Ee =855 MeV

Photon energy: < 5 MeV (Channeling Radiation)

0 50 100 150 200 250 3000,00

0,05

0,10

0,15

0,20

0,25

0,30

U [

a.u

.]

Thickness x [µm]

No saturationCan be explainedwith channeling /rechannelingprocesses

Fokker-PlanckEquation ->

18d µm

H. Backe et al. NIM B 266(2008) 3835

0 500 1000 15000

10

20

30

40

50

Dechannelin

g L

ength

[µ

m]

Electron Beam Energy [MeV]

Dechanneling Length versus Electron Energy

21.3 µm/GeV

Channeling with periodically bent crystals

Beam DumpIonization

Chamber

Top View

Experimental Setup @1.5GeV

-e

Si-Crystals

NaI Detector

(10" 10" length)

7.633 m

Pb 100 mm

45mm

Goniometer

2.7 m

Tagger

Magnet

Undulating crystal

Flat crystal

Aperture

3mm

Scan around the vertical axis Φ

Bent crystal

-5 0 5 10-4,5

-4,0

-3,5

-3,0

-2,5

-2,0

-1,5

(11

1)

(10

0)

(110)Aarhus-Kristall

28-08-08

wipp=-1.8°

Psi=178°

Phi:-10°->10°

0.1°/s

S

ign

al Io

nis

atio

n C

ha

mb

er

(lo

g)

[V]

[Degree]

no

Ch

an

ne

ling

Scan around the vertical axis Φ

Flat crystal

-5 0 5 10-4,0

-3,5

-3,0

-2,5

-2,0

-1,5

-1,0

no

Ch

an

ne

ling

(10

0)Flat Crystal

200 µm

28-08-21

wipp=-1.8°

Psi=178°

Phi:-10°->10°

0.1°/s

S

ign

al Io

nis

atio

n C

ha

mb

er

(lo

g)

[V]

[Degree]

(11

1)

(110)

Raw Data

0 5000 10000 15000 20000

0,1

1

10

100

Dir

ekto

ry:

C:x

1m

essp

c2

\Str

ah

lze

itd

ate

nX

-Str

ah

lze

ite

n\C

U-b

eiA

2-2

6-0

8-0

8u

sw

ert

un

g\,

F

ile

: O

nlin

e-2

8-0

8-0

8-n

ew

.op

j

Wo

rksh

ee

t: D

at1

_B

, G

rafikfe

nste

r: R

oh

sp

ektr

en

P

Events

[1/s

]

Energy [keV]

Aarhus 110

Aaarhus No-Channeling

200mu 110

200mu No-Channeling

Ro

hsp

ektr

en o

hn

e S

kal

ieru

ng

nu

r Z

eitn

orm

iert

Raw Data

0 500 1000 1500 20000

1

2

3

4

5

6

7

8

9

10

Dir

ekto

ry:

C:x

1m

essp

c2

\Str

ah

lze

itd

ate

nX

-Str

ah

lze

ite

n\C

U-b

eiA

2-2

6-0

8-0

8u

sw

ert

un

g\,

F

ile

: O

nlin

e-2

8-0

8-0

8-n

ew

.op

j

Wo

rksh

ee

t: D

at1

_B

, G

rafikfe

nste

r: G

rap

h3

E

ve

nts

[1

/s]

Energy [keV]

Aarhus 110

Aaarhus No-Channeling

200mu 110

200mu No-Channeling

Rohsp

ektr

en o

hne

Skal

ieru

ng n

ur

Zei

tnorm

iert

Channeling Spectra (110) Plane

0 5000 10000 15000 20000

0

1

2

3

4

Dir

ekto

ry:

C:x

1m

essp

c2

\Str

ah

lze

itd

ate

nX

-Str

ah

lze

ite

n\C

U-b

eiA

2-2

6-0

8-0

8u

sw

ert

un

g\,

F

ile

: O

nlin

e-2

8-0

8-0

8-n

ew

.op

j

Wo

rksh

ee

t: D

at2

_B

, G

rafikfe

nste

r: C

ha

nn

elin

gstr

ah

lun

g

Eve

nts

[1/s

]

Energy [keV]

Diff-Aa-110-U

Diff-200mu-110-U

Dif

fere

nze

n P

eak

- A

ulß

erh

alb

oh

ne

Sk

alie

run

g

0 5000 10000 15000 20000

0,0

0,5

1,0

Dir

ekto

ry:

, F

ile

: .o

pj

Wo

rksh

ee

t: d

at3

_C

, G

rafikfe

nste

r: G

rap

h1

E

ve

nts

Energy [keV]

Diff:Aa-200mu:<110>

Diff:Aa-200mu:<U>

rot:

Dif

fere

nz

<1

10

>

Aar

hu

s -

20

0µ

m

bla

u:

Dif

fere

nz

auß

erh

alb

Aar

hu

s -

20

0µ

m

20

0 µ

m K

rist

all

* 0

.73

Difference Spectra Bent-Flat

0 1000 2000 3000 4000 5000

0,0

0,5

1,0

Dir

ekto

ry:

C:x

1m

essp

c2

\Str

ah

lze

itd

ate

nX

-Str

ah

lze

ite

n\C

U-b

eiA

2-2

6-0

8-0

8u

sw

ert

un

g\,

F

ile

: O

nlin

e-2

8-1

0-0

8.o

pj

Wo

rksh

ee

t: d

at3

_C

, G

rafikfe

nste

r: G

rap

h5

Eve

nts

Energy [keV]

Difference Spectra Bent-Flat

0 500 1000 1500 2000

0,0

0,5

1,0

Dir

ekto

ry:

C:x

1m

essp

c2

\Str

ah

lze

itd

ate

nX

-Str

ah

lze

ite

n\C

U-b

eiA

2-2

6-0

8-0

8u

sw

ert

un

g\,

F

ile

: O

nlin

e-2

8-0

8-0

8-n

ew

.op

j

Wo

rksh

ee

t: d

at3

_C

, G

rafikfe

nste

r: G

rap

h4

Eve

nts

Energy [keV]

Diff:Aa-200mu:<110>

Diff:Aa-200mu:<U>

rot:

Dif

fere

nz

<110>

A

arhus

- 200µ

m

bla

u:

Dif

fere

nz

außer

hal

b A

arhus

- 200µ

m

200 µ

m K

rist

all

* 0

.73

Conclusions

• For Positron channeling a suitable machine is missing(Upgrading of BTF)

• Dechanneling length of Electrons have been measured

• With a 4 period Crystal Undulator an enhancement of radiation has been observed

21.3 µm/GeV

B. BuonomoS.B. DabagovG. Mazzitelli INFN Lab. Naz. di Frascati L. Quintieri

J. Esberg Department of Physics and AstronomyKim Kirsebom University of AarhusUlrik I. Uggerhøj

H. BackeM. El-Ghazaly Institute for Nuclear PhysicsP. Kunz University of Mainz W. LauthA. Rueda

G. Kube DESY Hamburg