Cryogenics play a vital role in building a Dynamic Nuclear Polarization (DNP) target for electron scattering experiments. The target material temperature was monitored using thermometry in order to evaluate their stability for use in the low temperature cryogenic bath of a DNP target. In this project, I investigated there solutions and accuracies of carbon ceramic, Cernox, Allen-Bradley, and thermocouple sensors at five known temperatures

Abbas, Zain

English

UNH Scholars' Repository

Understanding Thermometry at Low TemperatureZain Abbas. Advisors  Prof. K. Slifer and Dr. E. Long  Department of Physics, University of New Hampshire, Durham NH, 03824AbstractCryogenics play a vital role in building a Dynamic Nuclear Polarization(DNP) target for electron scattering experiments. The target materialtemperature was monitored using thermometry in order to evaluate theirstability for use in the low temperature cryogenic bath of a DNP target.In this project, I investigated the resolutions and accuracies of carbonceramic, Cernox, Allen-Bradley, and thermocouple sensors at fiveknown temperatures.All the sensors except thermocouple are Negative TemperatureCo-efficient (NTC). NTC sensors are made from pure metal oxides.They are inversely proportional to temperature changes.Carbon Ceramic Resistors:• The temperature range is1.5 - 300K .• Resistant to magnetic fieldsCernox:• Cernox temperature ranges from 100 mk to 420 K.• They are high sensitive at low temperature and good sensitivity over a broad range.Thermocouple (type K):• This thermocouple is madeof nickel-chromium and nickel-aluminum.• The temperature range is 73.15 K to 1533 K.• They have good corrosion resistance.BackgroundThe UNH Nuclear Physics Group is building a dynamic nuclearpolarization (DNP) target to spin-polarize protons in solid NH3 atcryogenic temperatures. DNP is capable of producing nearly 100%proton polarization, but its accuracy is dependent on that of thetemperature. The temperature of the DNP, shown below, is measurednear the 5T magnet where the NH3 will be located.At thermal equilibrium the spin polarization of protons in NH3 have aknown dependence on temperature and magnetic field:𝑃𝑇𝐸 = tanh𝜇𝐵𝑘𝑇To keep the uncertainty of the polarization under 1%, we can solvefor the required uncertainty in the thermometry.𝛿𝑃 =𝛿𝑃𝛿𝑇. 𝛿𝑇2𝛿𝑃 =−𝜇𝐵𝑠𝑒𝑐ℎ2𝐵𝜇𝑘𝑇𝑘𝑇2𝛿𝑇2where 𝛿𝑃 = 0.01, 𝜇 = −9.2𝑥10−24J/K, k = 1.38x10−23J/K, T = 1K, B= 5T. Solving for 𝛿𝑇gives us 𝛿𝑇 = 0.62𝐾. It shows that uncertainty intemperature must be less than 0.62K to achieve less than 1% relativeuncertainty in polarization.MethodThe Cernox was connected tothe Mercury ITC which is capableof automatic data logging.Carbon Ceramic Resistors (CCS):The two terminals of the sensor were solderedwith magnetic wire.The output terminals were connected to ohmmeter.Cernox:The two terminals of the Cernox were soldered with four magneticcopper wires. The inner two measures the voltageand outer two provides the current.The current and voltage was measured through ITC.Allen Bradley Resistors:The two terminals of Allen Bradley resistorswere soldered with magnetic copper wire.The resistance was measured using ohmmeter.Thermocouple (Type K):The positive nickel-chromium andnegative nickel-aluminum were connectedto the multimeter.Allen Bradley:• They are also known ascarbon resistors.• There temperatureranges is below 1K-100K.• Insensitive to nuclear radiations.Conclusions and future plans:This project will establish an accurate thermometry system to be usedin the polarized target lab. The calibration data indicates that CCS andCernox perform with sufficient accuracy and precision in LHe in giventemperatures, however AB responds poorly in LHe and does not matchour calibration curve, thus we can’t use it. For future measurements allof the thermometry data will go through the Mercury ITC and will beoperated by Labview.05001000150020002500300035004000450050000 100 200 300 400Carbon Ceramic Sensor (CCS)TheoreticalExperimentalResistance (Ω)Temperature (K)050010001500200025003000350040000 50 100 150 200 250 300Resistance (Ω)Temperature (K)TheoreticalExperimentalCernoxAB2Cernox& CCSAll the sensors were placed in liquid nitrogen, liquid helium,room temperature and ice water.AB1MagnetΩITCΩV-7-6-5-4-3-2-1012-250 -200 -150 -100 -50 0 50Voltage (mv)Temperature (K)ThermocoupleTheoreticalExperimental2002503003504004505005506000 50 100 150 200 250 300 350Allen Bradley TheoreticalAB1 experimentalAB 2Temperature (K)Resistance (Ω)

Understanding Thermometry at Low Temperature

University of New Hampshire

University of New Hampshire
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Spring 4-23-2014
Understanding Thermometry at Low Temperature
Zain Abbas
University of New Hampshire - Main Campus
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Abbas, Zain, "Understanding Thermometry at Low Temperature" (2014). Student Research Projects. 13.
https://scholars.unh.edu/student_research/13
Understanding Thermometry at Low Temperature
Zain Abbas. 
Advisors  Prof. K. Slifer and Dr. E. Long  
Department of Physics, University of New Hampshire, Durham NH, 03824
Abstract
Cryogenics play a vital role in building a Dynamic Nuclear Polarization
(DNP) target for electron scattering experiments. The target material
temperature was monitored using thermometry in order to evaluate their
stability for use in the low temperature cryogenic bath of a DNP target.
In this project, I investigated the resolutions and accuracies of carbon
ceramic, Cernox, Allen-Bradley, and thermocouple sensors at five
known temperatures.
All the sensors except thermocouple are Negative Temperature
Co-efficient (NTC). NTC sensors are made from pure metal oxides.
They are inversely proportional to temperature changes.
Carbon Ceramic Resistors:
• The temperature range is
1.5 - 300K .
• Resistant to magnetic fields
Cernox:
• Cernox temperature ranges 
from 100 mk to 420 K.
• They are high sensitive at 
low temperature and 
good sensitivity over a 
broad range.
Thermocouple (type K):
• This thermocouple is made
of nickel-chromium 
and nickel-aluminum.
• The temperature 
range is 73.15 K to 1533 K.
• They have good 
corrosion resistance.
Background
The UNH Nuclear Physics Group is building a dynamic nuclear
polarization (DNP) target to spin-polarize protons in solid NH3 at
cryogenic temperatures. DNP is capable of producing nearly 100%
proton polarization, but its accuracy is dependent on that of the
temperature. The temperature of the DNP, shown below, is measured
near the 5T magnet where the NH3 will be located.
At thermal equilibrium the spin polarization of protons in NH3 have a
known dependence on temperature and magnetic field:
𝑃𝑇𝐸 = tanh
𝜇𝐵
𝑘𝑇
To keep the uncertainty of the polarization under 1%, we can solve
for the required uncertainty in the thermometry.
𝛿𝑃 =
𝛿𝑃
𝛿𝑇
. 𝛿𝑇
2
𝛿𝑃 =
−𝜇𝐵𝑠𝑒𝑐ℎ2
𝐵𝜇
𝑘𝑇
𝑘𝑇2
𝛿𝑇
2
where 𝛿𝑃 = 0.01, 𝜇 = −9.2𝑥10−24J/K, k = 1.38x10−23J/K, T = 1K, B
= 5T. Solving for 𝛿𝑇gives us 𝛿𝑇 = 0.62𝐾. It shows that uncertainty in
temperature must be less than 0.62K to achieve less than 1% relative
uncertainty in polarization.
Method
The Cernox was connected to
the Mercury ITC which is capable
of automatic data logging.
Carbon Ceramic Resistors (CCS):
The two terminals of the sensor were soldered
with magnetic wire.
The output terminals were connected to ohmmeter.
Cernox:
The two terminals of the Cernox were soldered with four magnetic
copper wires. The inner two measures the voltage
and outer two provides the current.
The current and voltage was measured through ITC.
Allen Bradley Resistors:
The two terminals of Allen Bradley resistors
were soldered with magnetic copper wire.
The resistance was measured using ohmmeter.
Thermocouple (Type K):
The positive nickel-chromium and
negative nickel-aluminum were connected
to the multimeter.
Allen Bradley:
• They are also known as
carbon resistors.
• There temperature
ranges is below 1K-100K.
• Insensitive to 
nuclear radiations.
Conclusions and future plans:
This project will establish an accurate thermometry system to be used
in the polarized target lab. The calibration data indicates that CCS and
Cernox perform with sufficient accuracy and precision in LHe in given
temperatures, however AB responds poorly in LHe and does not match
our calibration curve, thus we can’t use it. For future measurements all
of the thermometry data will go through the Mercury ITC and will be
operated by Labview.
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 100 200 300 400
Carbon Ceramic Sensor (CCS)
Theoretical
Experimental
R
es
is
ta
n
ce
 (
Ω
)
Temperature (K)
0
500
1000
1500
2000
2500
3000
3500
4000
0 50 100 150 200 250 300
R
es
is
ta
n
ce
 (
Ω
)
Temperature (K)
Theoretical
Experimental
Cernox
AB2
Cernox
& 
CCS
All the sensors were placed in liquid nitrogen, liquid helium,
room temperature and ice water.
AB1
Magnet
Ω
ITC
Ω
V
-7
-6
-5
-4
-3
-2
-1
0
1
2
-250 -200 -150 -100 -50 0 50
V
o
lt
ag
e 
(m
v
)
Temperature (K)
Thermocouple
Theoretical
Experimental
200
250
300
350
400
450
500
550
600
0 50 100 150 200 250 300 350
Allen Bradley 
Theoretical
AB1 experimental
AB 2
Temperature (K)
R
es
is
ta
n
ce
 (
Ω
)


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