relativistic spin-polarized positron beam at mll filepolarization of betas: christoph hugenschmidt 5...
TRANSCRIPT
![Page 1: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/1.jpg)
Relativistic Spin-Polarized Positron Beam at MLL
Christoph Hugenschmidt
Technische Universität München
MLL2020 16 December 2015
![Page 2: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/2.jpg)
Christoph Hugenschmidt 2
Outline
NEPOMUC & Limits
Polarized e+
e+ beam at MLL
![Page 3: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/3.jpg)
Christoph Hugenschmidt 3
Positron Sources & Beams
+ isotopes p n e+ e high e+ yield long t
lab beams
pair production e+ e– E > 2mec2
high Z
large scale facilities
Ee+ ~keV
DE < 2 eV
NEPOMUC: Pt as converter AND moderator f+
Pt = -1.95(5) eV
1 eV
C. H. et al. NIM B 198 (2002) 220
+ spin polarized !
![Page 4: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/4.jpg)
Christoph Hugenschmidt 4
+ Sources
Nuclide Half-life Emax [MeV] Em [MeV] v/c f [%] E[MeV] Appl. Prod.
22Na 2.6 y 0.546 0.20 0.70 90 1.275 t, S, Beam Zyc
64Cu 12.7 h 0.653 0.27 0.76 19 - S, Beam Reac
68Ge/68Ga 271 d 1.90 0.99 0.94 90 - t, S Zyc
Polarization of betas:
![Page 5: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/5.jpg)
Christoph Hugenschmidt 5
Polarized Positron Beam
M. Maekawa et al.; NIM B 308 (2013) 9–14
68Ge production using p beam Beam flux: 104 e+/s (max) Polarization: 0.47 (max)
![Page 6: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/6.jpg)
Christoph Hugenschmidt 6
Spin Currents at Surfaces
Zhang et al. PRL 114, 166602 (2015)
Change relative spin orientation of e+ & e- Polarization dependent annihilation rate Spin currents at surface
![Page 7: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/7.jpg)
2D-ACAR Spectrometer at MLL/TUM
Ceeh et al. Rev. Sci. Instrum. 84, 043905 (2013)
ACAR
Angular Correlation of Annihilation Radiation
Electronic structure
Spin channels of DOS
Christoph Hugenschmidt 7
Features of ACAR:
special conditions not required
T >> 0, “no“ B-field
e+ beam surface, interface, thin layers, bulk
+ source bulk spin-polarized ACAR
![Page 8: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/8.jpg)
Spin Polarized ACAR
22Na , mean longitudinal polarization:
P = vm/c = 0.67
Measured polarization: P = 0.368(5)
Ceeh et al. Rev. Sci. Instrum. 84, 043905 (2013)
Christoph Hugenschmidt 8
![Page 9: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/9.jpg)
Motivation: Ferromagnetic Materials
FRM II News 8
Christoph Hugenschmidt 9
Nickel
Magnetic FCC metal
One unpaired 3d-electron
"simple" test case for theory and experiment
Theory
6eV satellite peak arises when correlations are included (DMFT)
Electron states are relocated
Effect of correlation change the appearance of the Fermi surface
http://www.phys.u.edu
J Kolorenc, et al., arXiv:1202.6595v1
![Page 10: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/10.jpg)
Prime Example: Ni
Christoph Hugenschmidt 10
Electron-electron interaction strength in ferromagnetic Ni determined by spin-polarized positron annihilation
H. Ceeh, J. Weber, P. Böni, M. Leitner, D. Benea, L. Chioncel, D. Vollhardt, H. Ebert, J. Minar, C. H.; arXiv:1501.02584
Result
Best agreement between experiment and theory DMFT(U) for U = 2.0eV
![Page 11: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/11.jpg)
Heusler Compounds: Cu2MnAl
Christoph Hugenschmidt 11
Cu2MnAl:
• L21-structure
• Prototype of Heusler alloys
• Ferromagnetic with no
ferromagnetic element
![Page 12: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/12.jpg)
Heusler Compounds: Cu2MnAl
Christoph Hugenschmidt 12
Individual contribution of each Fermi sheet to magnetisation !
J. Weber et al. PRL 115 (2015) 206404
![Page 13: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/13.jpg)
NEPOMUC
Cd Pt
fast e+
slow e+
n therm
n capture
emission
e+ e- conversion e+ moderation e+ emission
Neutron Source
FRM II
Positron Beam
NEPOMUC
Principle:
NEutron induced POsitron Source MUniCh
Christoph Hugenschmidt 13
C. H. et al. Appl. Phys. A 74 (2002) 295; Nucl. Instr. Meth. A 593 (2008) 616
![Page 14: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/14.jpg)
Christoph Hugenschmidt 14
NEPOMUC NEutron induced POsitron Source MUniCh
e+
Intensity: > 109 e+/s
C. H. et al. New J. Phys. 14 (2012) 055027; J. Phys. Conf. Ser. 443 (2013) 012079
![Page 15: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/15.jpg)
Christoph Hugenschmidt 15
PAES
Remoderator
Open beam port
CDBS PLEPS
SR 11 Switch
SPM interface
Positron Beam Facility at NEPOMUC
C. H. et al. NIM A 593 (2008) 616 New J. Phys. 14 (2012) 055027
J. Phys. Conf. Ser. 443 (2013) 012079
![Page 16: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/16.jpg)
What we Measure:
ideal crystal
crystal with defects
Doppler-Broadening Spectroscopy – DBS
Positron Lifetime Spectroscopy – PLS
Coincident Doppler-Broadening Spectroscopy – CDBS
Cr
Christoph Hugenschmidt 16
Angular Correlation of Annihilation Radiation – ACAR
![Page 17: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/17.jpg)
Christoph Hugenschmidt 17
What are the Limitations at NEPOMUC ?
Maximum beam energy
NEPOMUC provides a dedicated low-energy beam of high brightness
Maximum beam intensity
NEPOMUC provides highest beam intensity – can we do better?
Spin polarization
Pair production without distinct spin polarization
![Page 18: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/18.jpg)
z0(n,m,A, E): n,m,A material dependent parameters
Makhovian implantation profile:
Puska et al. Rev. Mod. Phys. 66 (1994) 841
Christoph Hugenschmidt 18
From the Surface to the Bulk
e+ Mean implantation depth (Al):
20 eV surface
10 keV layers 600 nm
30 keV bulk 4 µm 22Na: 200 keV bulk 150 µm
MLL: 10 MeV bulk 19 mm
![Page 19: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/19.jpg)
Christoph Hugenschmidt 19
(n, ) Reaction: 113Cd
Full absorption in W 75% NOT used for PP
114Cd: - spectrum
Solution: – “Beam“
Predicted spectrum of MEGa-ray source at ~2.54 MeV
![Page 20: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/20.jpg)
Positron Source Based on Inverse Compton Scattering
nsc ~ 2n0
~ 1000
Christoph Hugenschmidt 20
e+
C. H. et al. Appl. Phys. B: 106 (2012) 241 see White Book ELI
![Page 21: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/21.jpg)
Christoph Hugenschmidt 21
Beam Based e+ Source at ELI-NP
Features at first stage:
beam diam.: few mm
E = 3.5 MeV
I = 2.4 x 1010 γ/s
Expected key values:
slow positron intensity 1.9 x 106 s-1
spin polarization 31%
First user facility offering a polarized positron beam
ELI-NP/TDR/RA2/G2P/3/Jan2015
![Page 22: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/22.jpg)
Christoph Hugenschmidt 22
New Positron Beam at MLL
Idea: Put + emitter & e+ moderator inside the HV terminal of the tandem and apply a couple of MV !
![Page 23: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/23.jpg)
Christoph Hugenschmidt 23
New Positron Beam at MLL
Layout of terminal with positron source section:
![Page 24: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/24.jpg)
Christoph Hugenschmidt 24
New Positron Beam at MLL
Some numbers for 22Na and W moderator:
A= 50mCi Ye+ = 0.9 emod = 5(1)x10-3
etrans = 3(1)x10-1
Ie+ > 106 s-1 moderated & polarized !
Maximum beam energy
MeV range
Maximum beam intensity
Lower than NEPOMUC
Spin polarization
Almost 100% longitudinal spin polarization
![Page 25: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/25.jpg)
Christoph Hugenschmidt 25
Experiments with Relativistic Spin Polarized Positrons
Bulk studies:
Spin 2D-ACAR
AMOC
Spin CDBS
Spin lifetime
![Page 26: Relativistic Spin-Polarized Positron Beam at MLL filePolarization of betas: Christoph Hugenschmidt 5 Polarized Positron Beam M. Maekawa et al.; NIM B 308 (2013) 9–14 68Ge production](https://reader033.vdocuments.mx/reader033/viewer/2022050718/5e175696a1c2c52b8c4f4787/html5/thumbnails/26.jpg)
Christoph Hugenschmidt 26
Summary
Positron Beam at MLL
easy to realize
high-energy polarized positron beam
Spin Dependent Positron Beam Experiments
bulk electronic structure spin channels of DOS in correlated systems
spin dependent positron lifetime complementary to spin-ACAR
AMOC simultaneous measurement of momentum & e+ lifetime
Unique positron beam facility for polarized positrons
Thank you !