***THIS IS A COMBINED SOURCES SOUGHT NOTICE AND NOTICE OF INTENT TO SOLE SOURCE*** The National Institute of Standards and Technology (NIST) is seeking information from sources that may be capable of providing a large sample stage cryostat. If no alternate sources are identified, the Government intends to issue a Sole Source Award to Four Nine Design LLC, 3485 AJ Way, Unit 112, Billings, MT 59106 (UEI: Q1XUK2M6CJ77) under the authority of FAR 12.102(b) The North American Industry Classification System (NAICS) code for this acquisition is 334516. The National Institute of Standards and Technology (NIST) requires a large sample stage cryostat to support advanced cryogenic characterization of mixed-signal digital and analog circuits, as well as semiconductor devices, at temperatures down to 4.2 K. This system will be used to enable low-temperature testing of integrated circuits, interconnects, and device-level structures relevant to cryo-electronics for quantum information science, high-performance computing, and cryogenic sensor applications. The cryostat will support simultaneous DC, RF, and optical access to accommodate realistic operating conditions for complex electronic subsystems. The system is critical to sustaining and expanding NIST's cryo-electronics measurement capabilities and to providing a robust, measurement-driven foundation for cryogenic circuit and system development. NIST has a need for a Large Sample Stage Cryostat that meets or exceeds the following draft minimum specifications: Contract Line Item Number (CLIN) 0001 Description: Large Sample Stage Cryostat Quantity: One (1) Cooling Performance Shall provide a minimum cooling power of 2 W at 4.2 K. Cold Plate Size and Geometry Shall include a 4 K cold plate with diameter greater than Ø250 mm. Shall provide a 4 K cold plate height of approximately 200 mm to accommodate large circuits, probe assemblies, and fixtures. Thermal Cycling Performance Shall have a cool-down time of less than 90 minutes from room temperature to base temperature. Shall have a warm-up time of less than 120 minutes from base temperature to room temperature. Electrical Access Shall support a minimum of 50 DC lines suitable for low-temperature device and circuit biasing and control. Shall support a minimum of 30 RF lines, suitable for high-frequency (>18 GHz) characterization of mixed-signal circuits. At least two RF lines shall support frequencies above 60 GHz. If direct support above 60 GHz is not available, the system shall include physical provisions for future >60 GHz integration along with vendor recommendations for compatible upgrades. The system shall include provisions for future expansion of electrical feedthrough capacity, including at least 4 additional reserved or blank feedthrough ports that can be configured for either DC or RF use without major system modification. Optical and Fiber Access Shall support more than one fiber-optic feedthrough for optical excitation, readout, or synchroniz…