chris swank, bob golub - oak ridge national laboratoryΒ Β· 2012. 12. 31.Β Β· [1] c. swank and r....
TRANSCRIPT
-
Chris Swank, Bob Golub
-
Geometric phase from magnetic gradients
Gradients natural to coil geometry
Magnetic impurities in cell walls, cell coatings, magnetic dust on coatings.
SQUID pick up leads distort d-c fields
-
Geometry Rectangular cell Assume Spin Starts on the Left wall.
( )y y yB L B(0)y yB B
β’y rotation from small field in y β’x rotation from vΓE field.
Slower Rotation about y
Faster Rotation about y
0 1/ wall x
z
y
y
z
z
y
x
yB
v E
yB
E
-
yB
E
Spin Starts
Phase after one length
Spin Reflects and Travels Back
Phase after 1 round trip.
z
0.0005
0.001
0.0015
0.002
0.0025
30
210
60
240
90
270
120
300
150
330
180 0
x
y spin
0.001
0.002
0.003
0.004
0.005
30
210
60
240
90
270
120
300
150
330
180 0
yB
E
-
Derived from 2nd order density matrix formalism Spectrum of the field-position correlation function
field-position correlation function
field-position volume average
-
When the diffusion equation does not accurately describe the correlation function
Accurate description of correlation function necessary.
Simulation of the continuous time random walk
OR
Exact solution of the continuous time random walk.
Ξ»~L
-
Solution to the telegraphers equations satisfies isotropic Boltzmann transport in 1D
[1] C. Swank and R. Golub. arXiv:1012.4006 2010.
Valid for Diffusion Valid for Ballistic motion
π(π₯, π‘|π₯0, 0) =1
πΏ πβπ‘2ππ cosπππ₯0πΏβππ ππ‘
2ππ+π
π πsinπππ₯0πΏβππ ππ‘
2ππ
β
π=ββ
π π = 1 β 4ππ2ππ2, βββββππ =πππ£
πΏ
π»π₯(π‘)π₯(π‘ + π) = ππ₯0πΊπ₯π₯0π(π₯0, π‘) π₯π(π₯, π‘ + π|π₯0, π‘)ππ₯πΏ
0
πΏ
0
π»π₯π₯(π) =2πΊπ₯π£2ππ3
π2
1
12+ π2
π2 β ππ2 2ππ4 +π2
ππ2
β
π=ββ
http://arxiv.org/abs/1012.4006
-
Spectrum for the infinite region continuous time random walk in 2D
The infinite region 3D spectrum
3D
2D
-
Therefore the solution to the restricted conditional probability is defined from
And 3D (will be used.)
-
Define the spectrum.
Written in terms of the 3D conditional probability.
One can take advantage of the periodicity of the variables via Fourier series, Simplifying the integration.
-
The integration is a sum over the Fourier components of the field.
The position autocorrelation function spectrum in different dimensions
-
X=10.2 cm Y=40 cm
-
FID Measured Relaxation is Given by:
Where the Pulse loss is calculated from
The error propagates like
1
π1ππππππππ‘=πΎ2πΊπ§2
2
2ππ₯π₯(π0) + ππ¦π¦(π0
-
Assume vΒ² distribution
165 neV maximum energy
Completely ballistic motion
xwallv
π£ππ¦βπ€πππ
Specular wall reflections?
-
π = 1 ππ
π€ = .1 ΞΌπ
From AFM setting
[M. Brown, R. Golub, J. M. Pendelbury. Vacuum Vol. 25 num 2, 1974] [V. K. Ignatovich, JINR, p4-7055, 1973] [A Steyerl, Z Physic, 254, 1972]
π(β₯) βΌ 1%
-
For (small) magnetic impurities the correlation time is small
πΏπ = βπΎ2πΈ
ππ΅π₯π₯ + π΅π¦π¦
β 0
-
M= 0.2 π
-
https://nedm.bu.edu/twiki/pub/NEDM/Collab021011Agenda/dipole_detection.pdf
40nG sensitivity is required to detect micron sized
magnetic saturated particles. (Byung Kyu Park)
Cs NMOR magnetometer for testing.
https://nedm.bu.edu/twiki/pub/NEDM/Collab021011Agenda/dipole_detection.pdf
-
3mm OD round wire
(Bob Golub)
-
Thin film deposition
-
Deuterium Source at NCSU PULSTAR reactor
Correlation function studies via helium scintillation from
Critical Dressing Studies.
Effects of magnetic impurities/gradients
-
C. Crawford Magnetic Mirror
-
Geometric phase from magnetic gradients
Gradients natural to coil geometry
βͺ PULSTAR Experiment
Magnetic impurities in cell walls, cell coatings, magnetic dust on coatings.
βͺ Cs NMOR cells prior to fabrication
-
3D FEM
D(0.4)=977 cmΒ²/s D(0.45)=428 cmΒ²/s