4Thermal design Inputs for CZT-Imager Power generated by each channel of CZT ASIC3 mWNumber of channels in each CZT Module256Power generated by each CZT Module768 mWNumber of CZT in each quadrant16Power generated by each quadrant12.3 WNumber of quadrants4Power generated by the CZT-Imager49.2 WAllowed temperature variation among CZTs of each quadrant5oAllowed temperature difference among quadrantsWorking temperature range of the Instrument0o to – 20o
5TEMPERATURE 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 DETECTORCZT DETECTOR BOARDWITHIN CZT DETECTOR BOARDHEAT PIPERADIATOR5 o4 o5oTEMPERATURE DIFFERENCE BETWEEN DIFFERENT STAGES IN ONE QUADRANT
6If we consider factor of safety 2, it may be about 5 o K. Transfer of heat from CZT Detector to the CZT Detector Boardq = k A ΔTWhereq = Power = W,k = Thermal Conductivity of thermal epoxy= 0.08 W / cm2 oKA = Area = 4 cm2ΔT = / (0.08 * 4)= 2.42 o KIf we consider factor of safety 2, it may be about 5 o K.
8Coefficient of Thermal Expansion PROPERTIES OF CIC LAMINATEMetal /Core/ MetalDensity(g/cm3)Coefficient of Thermal Expansion(ppm/0c)Thermal ConductanceW/m-0cModulus elasticity,GPaTensile strength,MPax, yz20Cu/60In/20Cu8.456.07.71642213512.5Cu/75In/12.5Cu8.313.65.311064140
9Transfer 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.
10Boundary Conditions Temperature at the edges of Detector Board is 0o CZT Power (780 mW) distributed equally in 20mm X 20mm area
18Implications 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.
19CONCLUSIONS Total temperature difference is within 15 o to 20 o . Procuring one Detector Board and measure temperature difference.