1. Cadmium Zinc Telluride (CZT) Imager
Thermal Aspects of
Cadmium Zinc Telluride (CZT) Imager
Presented By
M.K. Hingar

2. Plan Configuration Design Inputs Design of the Detector Board
Analysis Results
Radiator & Heat Pipe Design
Critical Elements
Conclusions

3. CONFIGURATION

4. Thermal design Inputs for CZT-Imager
Power generated by each channel of CZT ASIC
3 mW
Number of channels in each CZT Module
256
Power generated by each CZT Module
768 mW
Number of CZT in each quadrant 16
Power generated by each quadrant
12.3 W
Number of quadrants 4
Power generated by the CZT-Imager
49.2 W
Allowed temperature variation among CZTs of each quadrant 5o
Allowed temperature difference among quadrants
Working temperature range of the Instrument
0o to – 20o

5. TEMPERATURE DIFFERENCE BETWEEN DIFFERENT STAGES IN ONE QUADRANT
Thermal Analysis has five Steps:
Transfer of heat from CZT Detector to the CZT Detector Board.
Transfer of heat within the CZT Detector Board.
Transfer of heat from CZT Detector Board to the Heat pipes.
Transfer of heat from Heat pipes to Radiator.
Radiator design.
CZT DETECTOR
CZT DETECTOR BOARD
WITHIN CZT DETECTOR BOARD
HEAT PIPE
RADIATOR
5 o
4 o 5o
TEMPERATURE DIFFERENCE BETWEEN DIFFERENT STAGES IN ONE QUADRANT

6. If we consider factor of safety 2, it may be about 5 o K.
Transfer of heat from CZT Detector to the CZT Detector Board
q = k A ΔT
Where
q = Power = W,
k = Thermal Conductivity of thermal epoxy
= 0.08 W / cm2 oK
A = Area = 4 cm2
ΔT = / (0.08 * 4)
= 2.42 o K
If we consider factor of safety 2, it may be about 5 o K.

7. Design of Detector Board
Cu-In-Cu
Copper Coating

8. Coefficient of Thermal Expansion
PROPERTIES OF CIC LAMINATE
Metal /Core/ Metal
Density
(g/cm3)
Coefficient of Thermal Expansion
(ppm/0c)
Thermal Conductance
W/m-0c
Modulus elasticity,
GPa
Tensile strength,
MPa
x, y z
20Cu/60In/20Cu
8.45
6.0
7.7
164 22
135
12.5Cu/75In/12.5Cu
8.31
3.6
5.3
110 64
140

9. Transfer of heat within the CZT Detector Board
The Detector Board of 20Cu/60In/20Cu.
The thickness of Detector Board is 3mm.
The preliminary analysis give the maximum temperature on the Detector Board of the quadrant is about 4o.

10. Boundary Conditions Temperature at the edges of Detector Board is 0o
CZT Power (780 mW) distributed equally in 20mm X 20mm area

15. Analysis shows
Heat Drain from two opposite sides of the Detector Board is necessary.
Radiation losses not considered.

16. TEMPERATURE DIFFERENCE 5 o
STEPS
TEMPERATURE DIFFERENCE
Transfer of heat from CZT to the Detector Board
5 o
Within Detector Board
4 o
Detector Board to heat pipe
Heat Pipe to Radiator

18. Implications of quadrants failures for thermal design
Suppose one of the quadrants fails then radiator will dissipate about 37 W (50 W ), the Radiator will have temperature of - 27o ( - 20o ).
Suppose two of the quadrants fail then radiator will dissipate about 25 W (50 W), the Radiator will have temperature of - 40o ( - 20o ).
Possible use of heaters to be considered after final simulation.

19. CONCLUSIONS Total temperature difference is within 15 o to 20 o .
Procuring one Detector Board and measure temperature difference.

20. !!!!! THANKS !!!!!