Algorithms of data
processing and
controlling experimental
equipment
Magnetic Resonance Spectroscopy
Popov Timophey
Komolkin Andrey, Sukharjevskiy Stanislav
1. Principles of Magnetic Field
Resonances
2. Radio Frequency Pulse Method
3. Continuous Wave Method
4. Real-time Operating Systems Review
5. Why QNX?
6. Current ESR-project
Nuclear Magnetic
Resonance
Electron Spin
Resonance
Continuous Wave
Method
Radio Frequency Pulse
Method
Nuclear Magnetic Resonance
Before and after energy absorption
z
z
B
B
hn
y
x
M
Relaxation
x
z
high
energy
low
energy
N
M
y
z
z
p
p/2
• Spin-spin relaxation
• Spin-lattice relaxation
M
y
x
S
y
M
M – magnetization vector
M
y
Nuclear Magnetic Resonance
NMR condition
hn  g N  N H
•
Field-frequency correlation for 1H-nucleus
 Magnetic field: ~ 10 000 oersted
 Resonance frequency: ~ 42.5 MHz
Electron Spin Resonance
Electron Spin:
Sz
1
 
2
1
 
2
3

2
Electron magnetic momentum :
e   g B S
Total angular momentum :
S
11 
3
1
 Sz   
  1 
22 
2
2
Magnetic potential energy of
electron spin in magnetic field:
1
U    B   g B B
2
Splitting
Energy

1
g B B
2
RF-induced
transition
hn
B0

1
g B B
2
H0
Increasing magnetic field B
Electron Spin Resonance
Integral intensity – proportional to quantity of unpaired
electrons in a sample.
Width of spectral line – characteristic of RF-energy absorption
conditions.
G-factor – using to initialize optional particles, participating in
reactions with free radicals.
•
X-band spectrometers (wavelength 3 cm)
 Magnetic field: ~ 3 400 oersted
 Resonance frequency: ~ 9,5 GHz
•
Q-band spectrometers (wavelength 8 mm)
 Magnetic field: ~ 15 500 oersted
 Resonance frequency: ~ 35 GHz
Continuous Wave Method
Sweep Coils
Sweep
Generator
S
Receiver &
Amplifier
RF
Generator
N
The oscillation of
sweeping magnetic field
must be far less then
increasing of external
field
Altering Magnetic Field
We have to solve
magnetic field scan
linearization problem
Continuous Wave Method
Magnetic Field Scan Linearization
H
H
I
I
t
t
Sweep Magnetic Field Scan
Signal
dA
t
dH1
H
1. First scan cycle: linearization
2. Second cycle: Slow H-field
scan with sweeping H1-field and
continuous transmission data to
computer.
dH 1
dH
Major condition:

dt
dt
First derivative
t
Continuous Wave Method
Double Integrating
Evening-out
Trend line
Fourier Transform
w
w0 2w0 3w0 4w0
Noise reduction
Fast Fourier Transform
If we have 2k measurements:
sin 2x  2  sin x  cos x
Method is usually used for wide spectral
lines and in ESR-spectrometry
RF-pulse Method
Interhardware
communication
We need guaranteed fast
communication between all
nodes in this experiment
Smart Pulse
Generator
S
Receiver &
Amplifier
N
Features:
• Constant strong external
magnetic field
• Free induction decay (FID)
time ~ 10 s – 1 s
• Short RF-pulses (10-100 ms)
RF-pulse Method Realization
t
Data processing
Data processing
Controlling
Smart
Pulse
Generator
Generating pulse
sequence
Receiver
Amplifier
ADC
FID-waiting &
Data buffering
!!! Other processes are sleeping !!!
Time to data
processing and
updating visual
information
RF-pulse Method features
Fourier Transform of nuclear echoes (FID)
FT
w
w0
Data Collecting
•
•
•
•
•
Data Collecting
Signal-to-noise ratio reduction
Evening-out
Real time visualization
Characteristic decay time 10s – 1s
2w0
3w0
4w0
Real Time Review
Real-time Review
Criteria & Requirements:
•
•
•
•
•
Interrupt latency (less than 1 ms)
Context-switch time
System Size
Rebooting time
Development and execution division
Hard Real Time Systems – any delays and interrupts are not allowed
on any conditions (e.g. aircraft navigation system)
Soft Real Time Systems – some delays are allowed, but it results in
increase production cost and decrease of system efficiency as a whole
(e.g. computer network)
Real-time Review
RT mechanisms:
• Priority system
• Scheduling algorithms
• Interprocess
communication (IPC)
• Operating with timers
and interrupts
RT-System classes:
• Embedded systems
(VXWorks, RTEMS)
• Real-time kernels (QNX,
OS9)
• Real-time UNIXes (RTLinux,
LynxOS)
• Real-time Windows
(Windows Embedded)
Fundamental Principles
• microkernel architecture
• message-based interprocess
communication
Kernel Architecture
• message passing – the Kernel
handles the routing of all messages
among all processes throughout the
entire system
• scheduling – the scheduler is a part
of Kernel and is invoked whenever a
process change state as the result of
a message or interrupt
System & Users’ Processes
• Process manager
• Filesystem manager
• Device Manager
• Network Manager
Device drivers
• choose to disappear at standard
processes, simply becoming extensions
to the system process they’re
associated with
• retain their individual identity as
standard process
File system
manager
microkernel
Process
manager
Device
manager
Network
manager
Interprocess communication (IPC)
Single-computer model
• QNX is message-based OS
• Message – a packet of bytes passed
from one process to another
• All messages contains information
about its state and priority, runtime
information, synchronizing the
execution and so on.
• Entire process and message space
among all incorporated QNXcomputers
• Sensible distribution network
resources amount executing real-time
processes
My Current ESR Project
Wave
conductor
Klystron
S
Detector
(high radio frequency
generator)
Strong
magnetic
field scan
Receiver
Amplifier
ADC
Resonator
with sample
Credits & References:

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

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Komolkin Andrey V.
Sukharjevskiy Stanislav M.
Quantum Magnetic Phenomena Department of
Physical Faculty SPbSU
SWD Software
http://hyperphysics.phyastr.gsu.edu/hbase/molecule/esr.html
http://www.cem.msu.edu/~reusch/VirtualText/Sp
ectrpy/nmr/nmr1.htm