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To: Mani1 who wrote (35768)	4/14/2001 6:09:46 PM
From: fyodor_	Read Replies (2) \| Respond to of 275872

Mani: Cryo temperatures changes the physical characteristics of solid state device, and allows them to run faster. It basically allows the electrons to move "easier" than they would at room temps. Or, put differently, it allows the transistor to switch faster ;-) (transistors switch faster at lower temperatures. period. as you correctly state, this actually shortens the data path (in the time domain)). Additionally, the thermal conductivity of silicon is much better at lower temperatures (peaks at around 20 Kelvin). This helps minimize "hot spots" on the die, again allowing the chip to run at higher frequencies. -fyo

To: Mani1 who wrote (35768)	4/15/2001 3:21:08 AM
From: Bilow	Read Replies (3) \| Respond to of 275872

Hi Mani Ahmadi; Re: "At cryo temps all materials have less electrical resistance, and as you probably know some material are super conductive." I guess there's a bunch of guys out on the internet that have it all wrong: ... The resistance of most common types of thermistor decreases as the temperature rises. They are called negative temperature coefficient, or ntc, thermistors. Note the -t° next to the circuit symbol. A typical ntc thermistor is made using semiconductor metal oxide materials. (Semiconductors have resistance properties midway between those of conductors and insulators.) As the temperature rises, more charge carriers become available and the resistance falls. ... users.dircon.co.uk ...It consists of a normal composite resistor (NTC) as temperature sensing element, a cryogenic valve and a box containing the hardware. ... As a sensing resistor we use a resistor of nominal 1000 ohm at room temperature, going to over 1350 ohm at liquid nitrogen temperature. ... nmr.de ... According to our senior sensor R engineer, Lake Shore's Cernox? ceramic oxynitride thin film over sapphire negative temperature coefficient (NTC) resistance temperature detectors (RTDs) are the best thing to happen to cryogenic thermometry in decade. With High Temperature Cernox?, a good product is now even better in the development of a cryogenic sensor that can withstand vacuum chamber bake-out temperatures to 140 °C. Cernox? RTDs combine small size, fast thermal response time, and a wide useful temperature range with excellent resistance to repeated thermal cycling, ionizing radiation, and magnetic fields; flexible packaging options are also available. With these features, Cernox? RTDs offer significant advantages over comparable bulk or thick film resistance sensors at comparable cost for applications from below liquid helium to room temperature, from 0.3 to 325 K. ... lakeshore.com -- Carl