Physics with Neutrons WS 2012/2013 - E21 - Technische Universität ...

e21.ph.tum.de

Physics with Neutrons WS 2012/2013 - E21 - Technische Universität ...

Physics with Neutrons

WS 2012/2013

Peter Böni

Physik-Department E21

Technische Universität München

D-85748 Garching

E-mail:Peter.boeni@frm2.tum.de

Web: www.e21.ph.tum.de

https://campus.tum.de/tumonline/lv.detailclvnr=950011566

13/11/2012

VL5, Physics with Neutrons I, Nov. 12, 2012


2

Seminar Methoden und Experimente in der Neutronenstreuung

Date Topics Contact

17 Oct. 12 Kick-Off Meeting

7 Nov. 12 Scheduling of presentations

Time: 10:00 (st) – 11:30

Place: PH 2224

28 Nov. 12 Larmor techniques NSE/NRSE Simone Sala, simone.sala@tum.de

5 Dec. 12 Quasielastic neutron scattering:

TOF-technique

Luca Braglia, luca.braglia@tum.de

12 Dec. 12 Positron Lifetime Javier Puertas Martinez, jpuertas_m@hotmail.com

19 Dec. 12 Magnetic Excitations Ibrahima Diallo, dialloib@msu.edu

9 Jan. 13 Flux Line Lattices in Superc. Jing Gong, happykissvicki@gmail.com

16 Jan. 13 Neutron optics Tianyi Wang, tianyi.wang@tum.de

23 Jan. 13 Strain measurements Rafael Cabello Portela, papelo72@hotmail.com

30 Jan. 13 Atomic force microscopy Christina Psylla, xripsy@hotmail.com

6 Feb. 13 Extreme conditions Wenbin Wu, wenbin.nj@gmail.com

Feb. 2013 Visit FRM II To be arranged.


Exercises

3

No exercises this week!


4

Scattering of Plane Wave by Spherically Symm. Potential

i

e

ik r

i


s


ik

(

rr')

f

e

r r'

d

detector

k i

k f

R’ = r – r’

r = 0

r’


r

k f

Q

V

( r r'

)


k i


Fermi Potential

5

R nuc 10 -15 m

n >> R nuc

s-wave scattering

Potential well for neutrons and protons in

an heavy nucleus, showing the Fermi level.


Neutron Scattering Lengths and Cross Sections

6


f(Q)

X-Ray Scattering: Form Factor

7

Aluminum (Z = 13)

Form factor:


f ( ) e Q r

q (

r)

d


atom


e

atom

i 3

1


2

2

e iQrp (

r)

r dpdr

0 1

r

iQr cosq

2

r

sinqdqddr


iQrp iQrp

e e

1

2


| (

r)

r

iQr 1

0



sin

4 Qr (

r)

r

2 dr

Qr

0

Q = 0 q = 0 0 :

2

dr

sinq/ (Å -1 )



0

f ( 0) 4

(

r)

r

2

dr Z

forward scattering Z


Bound and Free Scattering Length of Hydrogen

8

bound

free


free





A

A 1

2


bound

solid state:

H is bound

10 meV

Emendörfer/Höcker: „Theorie der Kernreaktoren Teil 1“, page 73, Bibliographisches Institut, Mannheim, 1969.

Originalquelle: Neutron cross sections, BNL-325, Sec. Ed., incl. Suppl. (1958-1966).


9

Absorption Cross Section of Natural Boron (B)

B

a (25 meV) = 767.8 barn

(barn)


a


1

E

2 meV

10 meV 100 meV 1 eV

For isotopes 10 B and 11 B see: http://atom.kaeri.re.kr/endfplot.shtml (it is best to choose MCNP)


Some Interesting Materials

soft matter

detectors

weapons

absorbers

monochromators

http://www.ncnr.nist.gov/resources/n-lengths/

10

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