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Superconducting Memory Cell Using Metastable States

IP.com Disclosure Number: IPCOM000091598D
Original Publication Date: 1968-Mar-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

McLachlan, DS: AUTHOR

Abstract

Hysteresis of phase transition in a superconducting sphere is used for binary storage. This is realized by turning it into a supercooled or a superheated metastable state, respectively. A small sphere, e..g., In, with 2% Pb, is inserted into the area common to crossed pairs of drive lines. Writing is accomplished by applying respective magnetic fields Hsc or Msh to the sphere to cause a phase transition. The presence or absence of flux penetration in the sphere when it is in the normal or superconducting state is used for reading. The radius of the sphere must be smaller than its normal skin depth and it must be larger than its penetration depth in the superconducting state. Hence, a suitable sphere diameter is about 10 mu m for drive pulses of about 500 ma with 1 ns risetime at a rate of 300 MC.

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Superconducting Memory Cell Using Metastable States

Hysteresis of phase transition in a superconducting sphere is used for binary storage. This is realized by turning it into a supercooled or a superheated metastable state, respectively. A small sphere, e..g., In, with 2% Pb, is inserted into the area common to crossed pairs of drive lines. Writing is accomplished by applying respective magnetic fields Hsc or Msh to the sphere to cause a phase transition. The presence or absence of flux penetration in the sphere when it is in the normal or superconducting state is used for reading. The radius of the sphere must be smaller than its normal skin depth and it must be larger than its penetration depth in the superconducting state. Hence, a suitable sphere diameter is about 10 mu m for drive pulses of about 500 ma with 1 ns risetime at a rate of 300 MC. The DC bias field Hb is slightly lower than the thermodynamic critical field Hc at the well stabilized operation temperature, e.g., 4.2 degrees K. Nondestructive readout is accomplished by sensing the presence or absence of coupling over a sphere between the pair of sense lines when applying drive pulses to the respective pair of drive lines.

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