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The DoD’s Defense Advanced Research Projects Agency (DARPA) has released that it will continue to fund its Low Power Micro Cryogenic Coolers (MCC) Program, which aims to attain superior performance in micro-scale devices, including superconducting circuits, by cooling selected portions to cryogenic temperatures. DARPA will provide the program with $1.81 million for FY2009 through its Research Development Test & Evaluation (RDT&E) funds. The program received $3.45 million in FY2008 and is budgeted to receive $1.48 million for FY2010.
“This is an example of program funding with uneven levels intended to best meet the financial needs of the program,” said Dennis Polla of DARPA’s Microsystems Technology Office and MCC Program Manager. “Upcoming MCC development will involve non-public institutions: as the program enters its third phase this fall, BAE Systems, of Nashua, NH, will collaborate with the University of Colorado, Boulder and National Institute of Standards and Technology (NIST), Boulder. NIST, Boulder has a very specific superconducting Hot Electron Bolometer that will require cryogenic cooling.”
MCCs may be Commercially Available
Polla added that the miniaturization of the systems would lead to greater efficiency: “Miniaturizing these systems will make them more efficient as solid state micromachining methods have been designed to provide excellent thermal isolation from heat dissipative paths such as through the substrate; active cooling methods can successfully target only the electronic component that will actually benefit from cooling. This leads to both high efficiency Joule Thompson cryogenic cooling and a significant reduction in power consumption.
“DARPA expects to demonstrate the new MCC on a common HgCdTe medium wavelength infrared (MWIR) focal plane array used in helicopter threat warning applications. Commercial use should be ready as early as 2012. However, at this time we will not release the significant benefits of active cooling time, size, and minimally-achievable temperature.”
Program Employs MEMS-enabled
The program’s key approach, and one that it hopes will allow orders of magnitude power savings, is to selectively cool only the needed volume/device via Micro-Electro-Mechanical Systems (MEMS)-enabled isolation technologies. Such an approach could benefit a large number of applications where performance is determined predominately by only a few devices in a system, such as communications where the front-end filter and LNA often set the noise figure and sensors where the transducer and input transistor in the sense amplifier often set the resolution.
MEMS technology will also be instrumental for achieving micro-scale mechanical pumps, valves, heat exchangers, and compressors, all needed to realize a complete cryogenic refrigeration system on a chip. DARPA intends for transition of the technology through industry, which will incorporate elements of the technology in current and future weapon system designs. NIST is reportedly currently making technical evaluations on whether these miniaturized pumps, valves, heat exchangers and compressors will have application for devices utilizing superconducting components.
The current funding builds off of several years of MCC development. In FY2007, the program demonstrated thermal isolation of >10,000K/W in a silicon micromachining process chip cooling to 77kilo using a photonic fiber heat exchanger and localized on-chip cooler approaches using integrated thermoelectric coolers and photonic heat exchangers. In FY2008 the program displayed micro-scale coolers capable of providing the needed cryogenic temperature while still fitting into a miniature size and with sufficient efficiency for low power operation, and showed the operation of the heat exchangers, Joule-Thompson plugs, valves and pumps needed for cryo-cooler implementation.
“We successfully realized all of our 2008 program goals,” said Polla. “In 2009 we have a number of targets we’d like to achieve, including getting total size down to under 3.5cm3, thermal isolation down to under 100,000K/W, total input power to under 100mW, display heat lift up over 20W and T over 216K from room temperature. We would also like to perform operational cooling to 145K of a HgCdTe MWIR focal plane array.”