Bremsstrahlung polarization correlations and their application for - - PowerPoint PPT Presentation

Bremsstrahlung polarization correlations and their application for polarimetry of electron beams

n = 2 l = 1 j = 3/2 j = 1/2 Gross structure l s l s l s F1

The Spin-Orbit interaction

★ modifies the effective binding potential ★ causes the Fine Structure splitting

l s F2

Stanislav Tashenov Physikalisches Institut of Heidelberg University

Fine structure

H H

Spin dynamics in Coulomb scattering and bremsstrahlung

The spin-orbit interaction causes the Mott scattering asymmetry when l || s

l s F2 l s F1

Vso ∝ ~ L · ~ S

Spin dynamics in Coulomb scattering and bremsstrahlung

The spin-orbit interaction causes the Mott scattering asymmetry when l || s Similar asymmetry is observed in the emitted bremsstrahlung photons

l s F2 l s F1

Vso ∝ ~ L · ~ S

When the spin and the orbital momentum are not parallel, they both precess about the total orbital momentum J

s F l

H

Spin dynamics in Coulomb scattering and bremsstrahlung

Vso ∝ ~ L · ~ S

When the spin and the orbital momentum are not parallel, they both precess about the total orbital momentum J

s F l

H

Spin dynamics in Coulomb scattering and bremsstrahlung

Vso ∝ ~ L · ~ S

d~ S dt ∝ ~ L × ~ S

When the spin and the orbital momentum are not parallel, they both precess about the total orbital momentum J

s F l

• H

Spin dynamics in Coulomb scattering and bremsstrahlung

Vso ∝ ~ L · ~ S

d~ S dt ∝ ~ L × ~ S

When the spin and the orbital momentum are not parallel, they both precess about the total orbital momentum J

s F l

The scattering plane at any moment is defined by the orbital momentum L

• Precession of L corresponds to the

precession of the instantaneous scattering plane

• H

Spin dynamics in Coulomb scattering and bremsstrahlung

Vso ∝ ~ L · ~ S

d~ S dt ∝ ~ L × ~ S

Polarization of bremsstrahlung radiation

Bremsstrahlung photon is:

★ emitted close to the nucleus ★ polarized within the scattering plane at that moment

Bremsstrahlung studies at electron accelerators with polarised beams

Mainz University

• S. Tashenov et al., PRL 107, 173201 (2011)
• S. Tashenov et al., NIM A 600 (2009) 599

X-rays scatter predominantly perpendicular to the polarization plane

• Planar segmented germanium detector
• Rayleigh and Compton polarimetry techniques

(Electron energy 100 keV)

Rayleigh and Compton polarimetry techniques

(Electron energy 100 keV)

• S. Tashenov et al., PRL 107, 173201 (2011)
• S. Tashenov et al., NIM A 600 (2009) 599

Polarization angle resolution 0.3 deg

Experiment at the polarized electron injector of S-DALINAC accelerator in TU-Darmstadt

60 120 180 240 300 360

• 6
• 4
• 2

2 4 6 electron spin angle (deg) photon polarization angle (deg)

c

Measurement of bremsstrahlung polarization correlations (Electron energy 100 keV)

60 120 180 240 300 360

• 6
• 4
• 2

2 4 6 electron spin angle (deg) photon polarization angle (deg)

c

Summary of the results (Electron energy 100 keV)

• S. Tashenov et al., Phys. Rev. Lett. 107, 173201 (2011)
• S. Tashenov et al., Phys. Rev. A 87, 022707 (2013)
• R. Märtin et al., Phys. Rev. Lett. 108, 264801 (2012)
• V. Yerokhin and A. Surzhykov, Phys. Rev. A 82, 062702 (2010)

transverse spin longitudinal spin

Stokes parameters

• S. Tashenov et al., Phys. Rev. A 87, 022707 (2013)

e l e c t r

• n

photon

a

p

• l

a r i z a t i

• n

p l a n e

χ

z x y

reaction plane

θ

S

3.5 3.0 2.5 2.0 1.5 1.0 0.5

(k/Z

2

)d

2σ/(dkd Ωκ)

180 150 120 90 60 30 photon emission angle θ (deg) 0.8 0.6 0.4 0.2 0.0

P1

180 150 120 90 60 30 0.30 0.25 0.20 0.15 0.10 0.05 0.00

P2

180 150 120 90 60 30 photon emission angle θ (deg)

• 0.20
• 0.15
• 0.10
• 0.05

0.00 0.05 0.10

C20 dσ

(0,1,0) (0,0,0) (1,0,0) (0,0,1) 100 keV C20 photon emission angle θ (deg) 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

(k/Z

2)d 2σ/(dkd Ωκ)

180 150 120 90 60 30 photon emission angle θ (deg) 0.6 0.4 0.2 0.0

• 0.2

P1

180 150 120 90 60 30 photon emission angle θ (deg) 0.4 0.3 0.2 0.1 0.0

• 0.1
• 0.2

P2

180 150 120 90 60 30 photon emission angle θ (deg) 0.8 0.6 0.4 0.2 0.0

• 0.2

C20

2 MeV

100 keV 2 MeV

• S. Tashenov et al., Phys. Rev. A 87, 022707 (2013)

3.5 3.0 2.5 2.0 1.5 1.0 0.5

(k/Z

2

)d

2σ/(dkd Ωκ)

180 150 120 90 60 30 photon emission angle θ (deg) 0.8 0.6 0.4 0.2 0.0

P1

180 150 120 90 60 30 0.30 0.25 0.20 0.15 0.10 0.05 0.00

P2

180 150 120 90 60 30 photon emission angle θ (deg)

• 0.20
• 0.15
• 0.10
• 0.05

0.00 0.05 0.10

C20 dσ

(0,1,0) (0,0,0) (1,0,0) (0,0,1) 100 keV C20 photon emission angle θ (deg) 10

• 4

10

• 3

10

• 2

10

• 1

10 10

1

(k/Z

2)d 2σ/(dkd Ωκ)

180 150 120 90 60 30 photon emission angle θ (deg) 0.6 0.4 0.2 0.0

• 0.2

P1

180 150 120 90 60 30 photon emission angle θ (deg) 0.4 0.3 0.2 0.1 0.0

• 0.1
• 0.2

P2

180 150 120 90 60 30 photon emission angle θ (deg) 0.8 0.6 0.4 0.2 0.0

• 0.2

C20

2 MeV

e l e c t r

• n

photon

a

p

• l

a r i z a t i

• n

p l a n e

χ

z x y

reaction plane

θ

S

100 keV 2 MeV

Electron polarimetry with bremsstrahlung

• S. Tashenov et al., Phys. Rev. A 87, 022707 (2013)

Electron polarimetry with bremsstrahlung

• S. Tashenov et al., Phys. Rev. A 87, 022707 (2013)

Electron polarimetry with bremsstrahlung

χ α α

χ

• S. Tashenov et al., Phys. Rev. A 87, 022707 (2013)

Electron polarimetry with bremsstrahlung

transverse polarization longitudinal polarization

Transverse polarization Longitudinal polarization Mott polarimetry

Measurement of bremsstrahlung polarization correlations at 2 MeV

electron beam gold target bremsstrahlung photons

Radiation background suppression via Compton Imaging First-time use of the Compton Imaging in a laboratory physics experiment

Bremsstrahlung + background Background suppressed preliminary preliminary

Experiment at Mainz Microtron MAMI

+

• guard ring

segment (cathode) Right segment Middle segment Left segment

Charge collection and transient detector pulses

Charge collection signal Transient signal Transient signal

Typical pulse pattern for 25-pixel detector and a Pulse Shape Analysis technique

5x5 matrix of 10x10x20 mm pixels

• 3D Position resolution

single interactions - 1x1x1 mm double interactions - 3x3x3 mm

Charge collection pulse Transient pulse

45 90 135 180 225 270 315 360

• 0.3
• 0.2
• 0.1

0.0 0.1 0.2 0.3

• 0.3
• 0.2
• 0.1

0.0 0.1 0.2 0.3 normalized intensity azimuthal scattering angle, deg helicity + helicity - normalized intensity

Preliminary results

electron spin electron spin

• 180 -135 -90 -45 0 45 90 135 180

45 90 135 180 225 270 315 360

• 0.3
• 0.2
• 0.1

0.0 0.1 0.2 0.3

• 0.3
• 0.2
• 0.1

0.0 0.1 0.2 0.3 normalized intensity azimuthal scattering angle, deg helicity + helicity - normalized intensity

Preliminary results

The polarization plane rotates by tens

• f degrees
• Dramatically enhanced effect of

the spin-orbit interaction

electron spin

• electron spin
• 180 -135 -90 -45 0 45 90 135 180

Currently developed large germanium spectrometers

AGATA (Europe) GRETA (USA)

Capable of Pulse Shape Analysis, Compton imaging and polarimetry

ASTRO-H X-ray Observatory (to be launched in 2015)

The largest x-ray observatory in a decade, built by Japanese space agency with participation of NASA, ESA and a number of Universities Soft gamma-ray detector

• Narrow Field of View Compton Telescope

25-pixel planar germanium detector

Shockley-Ramo theorem

+

Weighting potential

• I = q~

V × ~ Ew

Pulse Shape Analysis: The Matrix Method

M × x = s x = M −1 × s

List of energies from all possible locations

• Combined signal waveform

is a matrix of signal waveforms for every potential interaction position

• A. Khaplanov, PhD thesis, KTH Stockholm (2010)

Parity conservation in bremsstrahlung

Sy Sy 0o 0o 45o 135o Sx,z Sx,z * *

χ

c

Parity-allowed correlations Parity-forbidden correlations

COMPTEL telescope

• n board of the Compton Gamma Ray Observatory (1991-2000)