Amendment 2 to Solicitation for Ultra-High Vacuum Sample Backout Chamber Extension of Time 1333ND26QNB030068

As defined in the attached Combined Synopsis Solicitation, Statement of Work and applicable Clauses and Provisions.

AMENDMENT TO SOLICITATION FOR VENDOR QUESTIONS Solicitation 1333ND26QNB030068 Ultra High Vacuum Sample Backout Chamber Vendor Question 1: To accurately provide a quote for the chamber and frame, I would need a drawing, STEP file, and/or sketch, as a written description alone is not sufficient for an accurate quote. NIST Response: There are many ways to design and assemble a system with the capabilities that we are requesting. We have not provided a technical drawing to allow the vendor the flexibility to design a system to meet our specifications as they see fit. We will evaluate on conformance to specifications, not a particular design. Vendor Question 2: Regarding Technical Specification b. Partial pressure for masses >44 AMU: <5e-11 Torr : How is this intended to be controlled / measured with a base pressure of 1e-8 Torr. NIST Response: We will verify the stated specification with an RGA unit in our lab. Ultimately, this specification is to ensure that the UHV system is not contaminated with higher amu contaminants. The overall pressure is allowed to be 1e-8 Torr due to lower amu components (e.g. water) that we can more readily get rid of with a bake-out. We are not equipped to do the requisite UHV cleaning for higher mass contaminants (silicones, oils, etc.) so this requirement ensures the vendor provides us with a UHV-clean system. Vendor Question 3: Will a cylindrical chamber work rather than a cube or a sphere, so long as the volume requirements are met and there are enough ports? NIST Response: A cylindrical chamber with the same 12 opening dimensions would also suffice. Vendor Question 4: What is the geometry of the sample types to be going into the chamber? Is it like a wafer? NIST Response: We will be using this chamber on a variety of sample sizes and shapes. As defined in the attached Combined Synopsis Solicitation, Statement of Work and applicable Clauses and Provisions.

AMENDMENT 2: Extension of time 1 week from February 25,2026 to new date for responses March 4,2026. AMENDMENT TO SOLICITATION FOR VENDOR QUESTIONS Solicitation 1333ND26QNB030068 Ultra High Vacuum Sample Backout Chamber Vendor Question 1: To accurately provide a quote for the chamber and frame, I would need a drawing, STEP file, and/or sketch, as a written description alone is not sufficient for an accurate quote. NIST Response: There are many ways to design and assemble a system with the capabilities that we are requesting. We have not provided a technical drawing to allow the vendor the flexibility to design a system to meet our specifications as they see fit. We will evaluate on conformance to specifications, not a particular design. Vendor Question 2: Regarding Technical Specification b. Partial pressure for masses >44 AMU: <5e-11 Torr : How is this intended to be controlled / measured with a base pressure of 1e-8 Torr. NIST Response: We will verify the stated specification with an RGA unit in our lab. Ultimately, this specification is to ensure that the UHV system is not contaminated with higher amu contaminants. The overall pressure is allowed to be 1e-8 Torr due to lower amu components (e.g. water) that we can more readily get rid of with a bake-out. We are not equipped to do the requisite UHV cleaning for higher mass contaminants (silicones, oils, etc.) so this requirement ensures the vendor provides us with a UHV-clean system. Vendor Question 3: Will a cylindrical chamber work rather than a cube or a sphere, so long as the volume requirements are met and there are enough ports? NIST Response: A cylindrical chamber with the same 12 opening dimensions would also suffice. Vendor Question 4: What is the geometry of the sample types to be going into the chamber? Is it like a wafer? NIST Response: We will be using this chamber on a variety of sample sizes and shapes. As defined in the attached Combined Synopsis Solicitation, Statement of Work and applicable Clauses and Provisions.