integrator - Instituto de Plasmas e Fusão Nuclear
integrator - Instituto de Plasmas e Fusão Nuclear
integrator - Instituto de Plasmas e Fusão Nuclear
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Magnetics Diagnostics<br />
2 nd Advanced Course on Diagnostics and Data Acquisition<br />
Bernardo Brotas Carvalho<br />
bernardo@ipfn.ist.utl.pt<br />
http://ipfn.ist.utl.pt/EU-PhD/<br />
<strong>Instituto</strong> <strong>de</strong> <strong>Plasmas</strong> e <strong>Fusão</strong> <strong>Nuclear</strong><br />
<strong>Instituto</strong> Superior Técnico<br />
Lisbon, Portugal<br />
http://www.ipfn.ist.utl.pt<br />
B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
General Principles<br />
• Magnetic measurements provi<strong>de</strong> some of the<br />
most fundamental and essential information<br />
about a fusion plasma:<br />
– Iplasma, internal inductance, position and speed of<br />
current centroid, shape of boundary, thermal energy,<br />
currents in the magnet coils, and the strength of the<br />
magnetic fields confining the plasma<br />
– information about the internal characteristics of the<br />
plasma and about asymmetries caused by large-scale<br />
MHD instabilities<br />
– Halo Currents<br />
Author’s name | Place, Month xx, 2007 | Event<br />
2 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
General Principles<br />
• Essential for equilibrium reconstructions<br />
– Post-discharge full equilibrium co<strong>de</strong>s<br />
– Real-time Plasma Shape and position control<br />
• Magnetic diagnostics are external, passive<br />
and ROBUST<br />
– The measurements remain valid and useful<br />
over the full range of plasma <strong>de</strong>nsity and<br />
temperature as well as during large transient<br />
events (disruptions)<br />
Author’s name | Place, Month xx, 2007 | Event<br />
3 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Measurement of Magnetic Fields<br />
in Axisymmetric Configurations<br />
• The axisymmetric magnetic field in a<br />
cylindrical coordinate system (R, Z ,ϕ) can<br />
be expressed in terms of two scalar<br />
functions F and ψ:<br />
• This field can be separated in<br />
• Toroidal Field<br />
• Poloidal Field<br />
Author’s name | Place, Month xx, 2007 | Event<br />
4 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Magnetic and Current<br />
Poloidal Fluxes<br />
• The function ψ , “poloidal<br />
flux” (PF) is related to the<br />
magnetic field flux over<br />
one major circle at (R,Z)<br />
ψ R,Z = Ψ R,Z<br />
B<br />
Ψ R,Z =<br />
2π = R A φ (R, Z)<br />
B ∙ dS<br />
Z<br />
Flux per radian,<br />
also related to the<br />
toroidal component<br />
of the magnetic<br />
vector potential<br />
J pol<br />
• The function F, “poloidal<br />
current function” is related<br />
to the total current crossing<br />
a major circle at (R,Z)<br />
F R,Z = μ I pol R,Z<br />
I pol (R,Z)=<br />
Z<br />
2π = R B φ (R, Z)<br />
J pol<br />
∙ dS<br />
R<br />
R<br />
Author’s name | Place, Month xx, 2007 | Event<br />
5 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Toroidal Magnetic Field<br />
• Ampere’s Law<br />
• Poloidal component:<br />
• In vaccum =0 so Bϕ<br />
varies only with 1/R<br />
(no information from the<br />
plasma with external<br />
measurements)<br />
• Within plasma, Bϕ <strong>de</strong>pends<br />
on poloidal currents internal<br />
to the plasma<br />
– A “diamagnetic loop” can<br />
measure changes in the total<br />
toroidal field<br />
Bϕ = F/R<br />
Diamagnetic<br />
Plasma<br />
Paramagnetic<br />
Plasma<br />
Author’s name | Place, Month xx, 2007 | Event<br />
6 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Poloidal Magnetic Field<br />
• Toroidal Component<br />
• Using Green’s Theorem<br />
∂Ω<br />
Z<br />
x’<br />
r<br />
Plasma<br />
Ω<br />
External<br />
Coils<br />
Author’s name | Place, Month xx, 2007 | Event<br />
7 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Basic restrictions of the magnetic<br />
diagnostics for equilibrium reconstruction<br />
• Green’s Theorem with Ω<br />
boun<strong>de</strong>d by the plasma and<br />
r→∞<br />
1) Currents external to the<br />
plasma in coils or other<br />
conductors.<br />
2) Poloidal flux at the plasma<br />
boundary (constant)<br />
Z<br />
x’<br />
Ω<br />
∂Ω<br />
r<br />
Plasma<br />
r→∞<br />
K φ<br />
⨂<br />
B t<br />
External<br />
Coils<br />
3) Normal <strong>de</strong>rivative of Poloidal<br />
flux at the plasma boundary (B t )<br />
ψ = Cnst<br />
External magnetic<br />
Term “3” is equivalent The surface current K φ measurements can <strong>de</strong>termine<br />
to a given surface<br />
is itself equivalent to<br />
the poloidal flux anywhere in Ω<br />
current distribution K φ<br />
many internal current<br />
and on the equivalent surface<br />
at the plasma<br />
distribution insi<strong>de</strong> the<br />
current K. BUT can NEVER<br />
boundary: μ 0 K φ = B t Plasma J φ (r)<br />
distinguish different internal<br />
current distributions<br />
8 B. Carvalho| Lisbon, February 2, 2010 | Author’s Diagnostics name | Place, & Data Month Acquisition xx, 2007 | Event
Electrostatics Case<br />
The Electric Field outsi<strong>de</strong> the Sphere is the same for a given surface charge <strong>de</strong>nsity<br />
or other infinite volume charge distributions<br />
Plasma<br />
ω<br />
K(ω)<br />
Author’s name | Place, Month xx, 2007 | Event<br />
9 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Grad-Shafranov Equilibrium Equation<br />
• Combining equation for PF with magnetic<br />
force balance gives G-S equation<br />
insi<strong>de</strong> the plasma:<br />
• GS gives additional constraint on the<br />
magnetic field within the plasma but also<br />
introduces another unknown scalar function:<br />
the pressure<br />
• We need to make some assumptions<br />
p(ψ) and F(ψ) to obtain full plasma<br />
equilibrium solution<br />
10 B. Carvalho| Lisbon, February 2, 2010 | Author’s Diagnostics name | Place, & Data Month Acquisition xx, 2007 | Event
Determination of Plasma<br />
Shape and position<br />
• Taking measurements of the Poloidal Flux and poloidal<br />
Magnetic fields near the Wall, plus the currents in external<br />
Coil allows extrapolation of ψ(R,Z) until the plasma<br />
boundary<br />
• Plot the contours of ψ(R,Z)=Cte and then find the Last<br />
Closed Flux Surface (LCFS), or the the separatrix in divertor<br />
tokamaks<br />
Flux Loops<br />
LCFS<br />
Magnetic Probes<br />
Divertor Tokamak<br />
Author’s name | Place, Month xx, 2007 | Event<br />
11 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Other Integral quantities given<br />
from Magnetics measurements<br />
• Total plasma current I p<br />
• Poloidal beta:<br />
– Proportional to the thermal energy of<br />
the plasma!<br />
• Plasma Normalized Internal<br />
inductance:<br />
– related to the first moment of the<br />
current <strong>de</strong>nsity distribution<br />
• “Shafranov shift”<br />
-length of a poloidal<br />
contour at the plasma<br />
surface<br />
Plasma LCFS<br />
“Shafranov Shift”<br />
Author’s name | Place, Month xx, 2007 | Event<br />
12 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Inductive Sensors<br />
(Basic types)<br />
Mag. Flux on the Sensor Loop<br />
Signal on Sensor<br />
Signal from sensor must be integrated<br />
Author’s name | Place, Month xx, 2007 | Event<br />
13 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Axisymetric Poloidal Flux Loops<br />
Bp<br />
In Iron Core Tokamak<br />
with Ohmic Heating most<br />
of the poloidal flux is on<br />
the core itself<br />
To improve the sensivity one loop is<br />
chosen as reference and is subtracted<br />
from other loops: Φ net = 2π(ψ − ψ ref )<br />
The unintegrated voltage<br />
signal from a flux loop<br />
is the local one-turn<br />
loop voltage, V loop , driving<br />
the plasma current<br />
14 B. Carvalho| Lisbon, February 2, 2010 | Author’s Diagnostics name | Place, & Data Month Acquisition xx, 2007 | Event
Magnetic Field Probes<br />
• Probe measures components of the<br />
local magnetic field strength<br />
• Usually solenoidal, with dimensions<br />
small compared to the gradient scale<br />
length of the magnetic field<br />
Probes should be located on the plasmafacing<br />
si<strong>de</strong> of the vacuum vessel wall.<br />
Must be oriented to measure the field<br />
tangential to the wall; otherwise, eddy<br />
currents in the wall will attenuate the<br />
high-frequency part of the signal.<br />
Φ probe<br />
= N A B ∥<br />
Shielding of the tangencial field<br />
by the conductive wall.<br />
is the characteristic time for the<br />
magnetic flux to diffuse through<br />
wall<br />
15 B. Carvalho| Lisbon, February 2, 2010 | Author’s Diagnostics name | Place, & Data Month Acquisition xx, 2007 | Event
Saddle Loops<br />
Legs in toroidal<br />
direction<br />
Legs in poloidal<br />
direction<br />
• Can be viewed as a<br />
large-scale magnetic<br />
probe for the magnetic<br />
field normal to the<br />
surface:<br />
• Or as probes measuring<br />
flux difference:<br />
Often used for <strong>de</strong>tecting nonaxisymmetric<br />
fields caused by nonrotating MHD<br />
instabilities.<br />
This measurement is most sensitive to<br />
instabilities with low frequencies since at<br />
high frequencies the normal component of<br />
the field is shiel<strong>de</strong>d by the wall<br />
• Also used for active<br />
control of MHD plasma<br />
mo<strong>de</strong>s (eg. RFX,<br />
Padova)<br />
Author’s name | Place, Month xx, 2007 | Event<br />
16 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Diamagnetic Loops<br />
At low beta the change in the total<br />
toroidal flux is small.<br />
• A diamagnetic loop measures the<br />
toroidal magnetic flux for the<br />
purpose of estimating the thermal<br />
energy of the plasma.<br />
• Normally located in a poloidal<br />
plane in or<strong>de</strong>r to minimize<br />
coupling to the poloidal field.<br />
A reference signal equal to the vacuum<br />
magnetic flux is usually subtracted,<br />
with<br />
Author’s name | Place, Month xx, 2007 | Event<br />
17 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Rogowski Coil<br />
Ip<br />
The Conducting path from one end of the<br />
coil returns along the axis to the other<br />
end<br />
• The Rogowski coil measures<br />
electric current flowing through<br />
the enclosed surface<br />
(e.g. plasma, plasma + vessel,<br />
external coils, passive<br />
conductors, Halo Currents, etc.)<br />
• The total flux linked by all turns is<br />
proportional to the contour<br />
integral:<br />
Φ Rog ~ B dl = μ 0 I<br />
• Signal is proportional to current<br />
time <strong>de</strong>rivative<br />
V = −Nμ 0 n A dI<br />
dt<br />
Author’s name | Place, Month xx, 2007 | Event<br />
18 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Integration of signals from<br />
inductive sensors<br />
• To obtain the fluxes and magnetic field values<br />
from inductive sensors we must integrate the<br />
signal in time:<br />
V out = − 1 τ<br />
V in dt = − Φ τ<br />
• Typical loop flux values vary from few mV.s to<br />
few V.s (eg. Iron core), so <strong>integrator</strong> circuits are<br />
used with τ equal to 1 ms to 1 s<br />
Simple Passive Integrator<br />
The approximation fails for timescales<br />
comparable to or longer than τ<br />
Author’s name | Place, Month xx, 2007 | Event<br />
19 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Active Integration<br />
V offset<br />
But now a new pratical problem:<br />
“Integrator drift”<br />
Exemple: for RC = 10ms a 100 μV offset<br />
integrates to a 0.1 V after 10 s<br />
The gain is similar to the passive<br />
<strong>integrator</strong> but now the timescale is<br />
increased for ~RC to ~G* RC ( 1 to 10 s)<br />
Feedback<br />
Filter<br />
Basic compensation circuit<br />
Author’s name | Place, Month xx, 2007 | Event<br />
20 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Pick Up Coil<br />
Advanced Analog Integrators<br />
Automatic drift-compensation: Measurement<br />
of drift before integration, store and<br />
compensate offset during integration<br />
Drift can be reduced down to<br />
several 0.1mVs / 1000s<br />
Reset<br />
But worse values if signal<br />
is applied during drift<br />
compensation!<br />
Common mo<strong>de</strong> rejection<br />
Asymmetric input!<br />
-<br />
+<br />
S/H<br />
ADC<br />
Drift achieved in Tore Supra:<br />
< 135 μVs / 1000 s<br />
Auto Offset Correction<br />
Author’s name | Place, Month xx, 2007 | Event<br />
21 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Pick Up Coil<br />
Digital (chopper) <strong>integrator</strong><br />
Clock<br />
ADC<br />
Digital Input<br />
Chopper<br />
Num. Rectifier<br />
+ Integration<br />
Amp<br />
ADC<br />
AC coupling allowed!<br />
• Dynamic range limited by input stage<br />
• Not affected by input stage semiconductors<br />
• No 1/f noise<br />
• Complex offset correction algorithms feasible<br />
• Very simple consumer electronics!<br />
Author’s name | Place, Month xx, 2007 | Event<br />
22 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Pick Up Coil<br />
W-7X prototype Integrator schematic<br />
Low pass<br />
(avoid resistors,<br />
huge thermovoltage)<br />
1<br />
2<br />
Clock<br />
Butterworth low pass,<br />
removes spikes by charge injection<br />
2<br />
1<br />
-<br />
+<br />
+<br />
1<br />
2<br />
+<br />
-<br />
-<br />
Input Chopper<br />
Symmetric chopper stage based<br />
on CMOS switch MAX4644<br />
R on < 3Ω<br />
Instrumentation<br />
Amplifier<br />
Clock<br />
USB Power Supply<br />
Low charge injection<br />
Prototype (still in use)<br />
23 B. Carvalho| Lisbon, February 2, 2010 | Author’s Diagnostics name | Place, & Data Month Acquisition xx, 2007 | Event
W-7X prototype Integrator drift<br />
• 100 s drift<br />
compensation<br />
• 1000 s run<br />
“Cold Integrator”<br />
• Drift:<br />
< 70 μVs / 1000 s<br />
Author’s name | Place, Month xx, 2007 | Event<br />
24 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Diagnostics with non-Integrated<br />
signal from Inductive probes<br />
• Vertical Speed of Plasma current centroid<br />
– Linear combinations of flux and field probes<br />
– Used as controllabe variables for active control<br />
• MHD Instabilities <strong>de</strong>tection and control<br />
– “Mirnov coils”, poloidal or toroidal arrays of<br />
probes oriented to measure poloidal<br />
component, insi<strong>de</strong> the vacuum vessel<br />
Differential connection of<br />
magnetic probes, for<br />
<strong>de</strong>tection of nonrotating<br />
MHD mo<strong>de</strong>s or .<br />
Array of 12 Mirnov Coils in<br />
ISTTOK<br />
Author’s name | Place, Month xx, 2007 | Event<br />
25 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
MHD Instabilities diagnostics<br />
• Analyses Techniques:<br />
– Spectrogram (Fourier analysis of sucessive<br />
short-time windows<br />
Spectrogram of magnetic probe signals in JET, showing the time<br />
evolution of the amplitu<strong>de</strong>s and frequencies of several tearing<br />
mo<strong>de</strong>s.<br />
26 B. Carvalho| Lisbon, February 2, 2010 | Author’s Diagnostics name | Place, & Data Month Acquisition xx, 2007 | Event
MHD Instabilities diagnostics:<br />
Other techniques<br />
• Wavelet analysis<br />
• Hilbert transform<br />
• Singular Value Decomposition (SVD)<br />
Experimental data from T-10 shot no.<br />
21576:<br />
(a) Hilbert spectrum;<br />
(b) Spectrogram<br />
(c) wavelet scalogram.<br />
a)<br />
c)<br />
b)<br />
Author’s name | Place, Month xx, 2007 | Event<br />
27 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
MHD mo<strong>de</strong> <strong>de</strong>tection<br />
• Mo<strong>de</strong> number are <strong>de</strong>termined by the<br />
phase shift, (by Fourier Analysis) between<br />
equally or varied separated Mirnov coils<br />
I<strong>de</strong>ntification of the mo<strong>de</strong> number<br />
and polarization of a compressional<br />
I<strong>de</strong>ntification of poloidal mo<strong>de</strong><br />
Alfvén eigenmo<strong>de</strong> in NSTX,<br />
number m=4 for a tearing<br />
showing phase shift and amplitu<strong>de</strong><br />
mo<strong>de</strong> in TFTR, showing the<br />
versus toroidal angle.<br />
phase shift of Mirnov loop<br />
The phase shift between toroidally<br />
separated coils gives a toroidal<br />
signals versus poloidal angle.<br />
mo<strong>de</strong> number n = 7<br />
28 B. Carvalho| Lisbon, February 2, 2010 | Author’s Diagnostics name | Place, & Data Month Acquisition xx, 2007 | Event
Nonrotating Mo<strong>de</strong>s<br />
• Nonrotating mo<strong>de</strong>s are most<br />
commonly <strong>de</strong>tected with toroidal<br />
arrays of saddle coils (loops<br />
oriented to measure the radial<br />
field)<br />
– Low frequencies involved and the<br />
field perturbation of the mo<strong>de</strong><br />
penetrates the vacuum vessel<br />
Time evolution of an RWM in<br />
JT-60U, showing contours of<br />
the time <strong>de</strong>rivative of the<br />
radial field perturbation<br />
measured with a uniformly<br />
spaced toroidal array of eight<br />
saddle coils<br />
Author’s name | Place, Month xx, 2007 | Event<br />
29 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Non Inductive Sensors<br />
• Hall Probes<br />
– relatively simple and inexpensive<br />
• Resistive Shunts<br />
– measuring “halo” currents flowing between the plasma and<br />
plasma-facing components<br />
• Faraday rotation current measurements<br />
Example of Hall<br />
Probe for ITER<br />
V H = 1 I B<br />
qn a<br />
Schematic overview of a fiber-optic<br />
Schematic figure of a Hall probe in a Hall coefficient, is a Faraday rotation measurement<br />
magnetic field B,<br />
property of the <strong>de</strong>vice, to be used for the<br />
with I the injected current and V H the material<br />
measurement of the plasma current<br />
resulting Hall<br />
in ITER<br />
30 voltage.<br />
B. Carvalho| Lisbon, February 2, 2010 | Author’s Diagnostics name | Place, & Data Month Acquisition xx, 2007 | Event
Burning plasma experiments/ITER<br />
ITER will be the burning plasma experiment where<br />
all the knowledge on burning plasma diagnostics<br />
will converge<br />
Relative to existing machines, on ITER diagnostic<br />
components will be subjected to (relative to JET)<br />
• High neutron and gamma fluxes (up to x10)<br />
•Neutron heating (essentially zero)<br />
•High fluxes of energetic neutral particles<br />
from charge-exchange processes (up to x5)<br />
•Long pulse lengths (up to x100)<br />
•High neutron fluence (>10 6 !)<br />
Author’s name | Place, Month xx, 2007 | Event<br />
31 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
ITER diagnostics<br />
Functional requirements<br />
“to provi<strong>de</strong> accurate measurements of plasma behaviour and<br />
performance.”<br />
3 categories of measurement parameters<br />
• Group 1 Machine protection and Basic machine control<br />
(machine operation unable without this group)<br />
• Group 1b advanced plasma control<br />
(machine advanced operation unable without this group)<br />
• Group 2 evaluation and physics studies<br />
(machine operation able without this group)<br />
Author’s name | Place, Month xx, 2007 | Event<br />
32 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Magnetic Diagnostic Set for ITER<br />
Total :<br />
Location n g Type Number<br />
In-vessel sensors:<br />
Behind blanket<br />
modules, fixed on<br />
VV inner skin<br />
Divertor<br />
Ex-vessel sensors<br />
Fixed on VV outer<br />
skin<br />
Insi<strong>de</strong> TFC case<br />
(T=4K)<br />
Radiation/Dose<br />
(cm -2 s -1 ) / MGy<br />
3. 10 12<br />
Pick-up coils 186<br />
Rogowski<br />
(halo current)<br />
360<br />
Flux loops 220<br />
High freq<br />
coils<br />
>300<br />
Pick-up coils 72<br />
Rogowski<br />
(halo current)<br />
48<br />
Pick-up coils 360<br />
Steady state<br />
sensors<br />
120<br />
Flux loops 5<br />
Author’s name | Place, Month xx, 2007 | Event<br />
33 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition<br />
500<br />
1. 10 13<br />
1700<br />
1. 10 13<br />
1700<br />
1.5 10 10<br />
2.5<br />
1. 10 10<br />
1.7<br />
1. 10 12<br />
340<br />
3. 10 12<br />
1000<br />
3. 10 12<br />
1000<br />
1. 10 10<br />
3.4<br />
2. 10 9<br />
0.7<br />
Optic fibre 12<br />
Rogowski<br />
(I plasma)<br />
3<br />
~ 1700 sensors, 19 types, >300km of cable
ITER Magnetic Poloidal Set<br />
Author’s name | Place, Month xx, 2007 | Event<br />
34 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
MHD saddle loops mounted on<br />
all 9 machine sectors, ma<strong>de</strong> from<br />
mineral insulated (MI) cable<br />
Author’s name | Place, Month xx, 2007 | Event<br />
35 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Main Technogical Chalenges<br />
• Long plasma pulse length (400s – 3000s):<br />
• Integrator Drift and induced EMF Issues<br />
• Radiation Effects- Prompt:<br />
• RIC - Radiation Induced Conductivity<br />
• Loads the signal during the pulse. Can be mitigated by choice of<br />
material<br />
• RIEMF - Radiation induced electromotive force<br />
• Both neutrons and gammas, induces currents between the sensor wire<br />
and its surroundings. The typical magnitu<strong>de</strong> is in the range 0.1-10 V<br />
• RIED- Radiation induced electrical <strong>de</strong>gradation<br />
• The insulator material, including impurity content, is important and even<br />
different samples of the same material can behave differently<br />
• TIEMF - Thermally induced electromotive force<br />
• Produces a non-zero thermo-electric EMF due to manufacturing<br />
imperfections<br />
Author’s name | Place, Month xx, 2007 | Event<br />
36 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Main Technological Chalenges<br />
• Radiation Effects- Long Term:<br />
• RIED- Radiation Induced electrical <strong>de</strong>gradation<br />
• The insulator material, including impurity content, is<br />
important and even different samples of the same<br />
material can behave differently<br />
• RITES - Radiation Induced ThermoElectric Sensivity<br />
• <strong>Nuclear</strong> heating supplies the temperature differences<br />
• Variety of effects can supply the material propety<br />
changes that generate themocouples<br />
• Installation and Integration problems<br />
• Design qualified for the machine lifetime > 20 years<br />
Author’s name | Place, Month xx, 2007 | Event<br />
37 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition
Author’s name | Place, Month xx, 2007 | Event<br />
38 B. Carvalho| Lisbon, February 2, 2010 | Diagnostics & Data Acquisition