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Infrared Radiation Detector

IP.com Disclosure Number: IPCOM000077587D
Original Publication Date: 1972-Aug-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Hodgson, RT: AUTHOR [+3]

Abstract

An infrared radiation bolometer detector is described which is based on the observed 13 order of magnitude resistivity decrease in ferro magnetic, europium rich EuO when it is cooled from its magnetic ordering temperature (69.3 degrees K) to 40 degrees K. This large decrease in the resistivity, which is caused by the increase in magnetization, which in turn is caused by the decrease in temperature, is the basis for bolometer action in this device. Radiation incident on the EuO in either single crystal or thin film form is absorbed, either by the crystal or by a thin absorbing coating. The temperature of the EuO rises and the subsequent decrease in resistivity is measured by standard methods. The EuO is weakly connected to a thermal reservoir held in the range of 50-70 degrees K.

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Infrared Radiation Detector

An infrared radiation bolometer detector is described which is based on the observed 13 order of magnitude resistivity decrease in ferro magnetic, europium rich EuO when it is cooled from its magnetic ordering temperature (69.3 degrees
K) to 40 degrees K. This large decrease in the resistivity, which is caused by the increase in magnetization, which in turn is caused by the decrease in temperature, is the basis for bolometer action in this device. Radiation incident on the EuO in either single crystal or thin film form is absorbed, either by the crystal or by a thin absorbing coating. The temperature of the EuO rises and the subsequent decrease in resistivity is measured by standard methods. The EuO is weakly connected to a thermal reservoir held in the range of 50-70 degrees K. These temperatures are easily accessible by pumping on liquid nitrogen, a much more convenient and efficient refrigerant than liquid He.

The large thermal coefficient of resistance parameter alpha = 1 over R dR over dT approx. 0.5-1 is due to operating the device in the region of a phase transition, here a magnetic phase transition, in a material in which the resistivity is strongly coupled to the change in phase.

Using parameters suitable for this device (See the figure), the expected noise equivalent power (NEP) is NEP approx. 3 x 10/-11/ over B/1/2/ watts/H(z)/1/2/ where B is the bandwidth of the amplifier and detector used to measure the bolometer resistanc...