Attachment A - Specifications for a Dilution Refrigerator System.pdf

Specifications for a dilution refrigerator system

This dilution refrigerator system consists of a Gas Handling System Refrigerator (hereafter referred to as GHS) and two identical He3/He4 dilution inserts.

Performance Characteristics

• Base temperature: ≤ 30mK

• Cooling power: ≥ 40 µW at 100mK

• Cool-down time: ≤ 2 hours to base temperature beginning from the start of condensing the mixture.

• Operational temperature range, control, and stability: 30mK ≤ T ≤ 1.5K with 5% temperature control and stability over the entire range.

• Experimental space diameter approx. 28 mm

General Specifications

Operating Features

• The Seller shall supply a sliding seal at the top, so that the vertical position of the

Dilution Refrigerator (hereafter referred to as the “DR”) insert may be adjusted without rotation with respect to a NW50 flange in the host system. We will provide general dimensions of the host systems in the figures below for the purpose of the quotations. These top loading host systems are 2 cryo-magnets, with bore of diameter of 35mm and a liquid helium refrigerator with 45mm bore. The top flange of all these hosts is an ISO NW50.

• Optimized ³He/4He mixture designed to operate with an external dump. These two DR inserts must be designed to operate, with the same performance characteristics as listed above, not only with the provided GHS but also with our existing GHS. Our existing GHSs have a mixture volume of 10.5 liters. 2.8 liters of this volume corresponds to He3.

• Regarding whom provides the He3/He4 mixture: Tests at the manufacturer facility to be done with their own He3/He4 mixture. DRs will be shipped with no mixture to ORNL. ORNL will load its own He3/He4 mixture when the system arrives onsite, with same volume, and same ratio composition.

• One external liquid nitrogen cold trap with one dewar capable of hold times of at least 7 days.

• At a minimum, pressure gauges/transducers on the dump, insert inlet, insert outlet, and pump outlet.

Control System Features The Seller shall provide a complete control system capable of autonomous, local control of the DR system.

• A Lakeshore 372 AC Resistance Bridge controller shall be provided.

• 16 channel Lakeshore scanner

• Auto-cool down and auto-run routines allow unattended operation. Automated cooling capability and manual override option.

• Control system source code shall be provided by the seller to allow for interfacing with our software controls. The local control system shall be capable of communicating both control functions and data logging to a remote computer by using a TCP/IP connection that exports the data.

Sensors The Seller shall provide the following sensors.

• Installed thermometry (Fig 1: location of sensors) including:

Precision-calibrated RuO2 sensor on Mixing Chamber (hereafter referred to as the “MC”) of measuring the temperature over the entire operational temperature range (30mK to 300K) and with resolution (±1–3 mK at 50 mK; ±2–5 mK at 100mK; ±5–10 mK at 300 mK; ±10–20 mK at 1K; ±20–50 mK at 4.2 K).

For diagnostic use, temperature sensors at the Heat Exchange (HX), at the 1K/condensation stage coil and the STILL. One of these sensors needs to be useful for appropriate diagnostics from 0.3K up to 300K across the whole range.

The Seller shall provide calibration curves for all temperature sensors.

Fig 1: Location of sensors

Wiring and Connectors

• In addition to the wiring necessary for the sensors referred to in Section “Sensors”, at least an additional 12 twisted-pair wiring of manganin and/or CuNi clad NbTi shall be provided down to the Mixing Chamber for subsequent consumer use. Ends shall be terminated by an appropriate connector. Mating connectors for these leads shall be supplied (e.g. Micro-D connectors)

• Those connectors related to sensors and those related to heaters should be distinct as should those related to the DR and those related to subsequent consumer installed components.

• Wiring/connectors associated with sensors and wiring/connectors associated with heaters shall be installed in such a way as to maximize electromagnetic isolation.

• The Seller shall provide a toolbox with extra connectors and spools of spare wire.

Warming Heaters

• Three resistive heaters shall be installed in the following locations:

Mixing chamber (two heaters for redundancy) Still

• The heaters shall be chosen to satisfy the operational temperature range and stability criterion.

Physical Characteristics

• Two interchangeable sealed inner vacuum cans (IVCs), relevant dimensions shown in figure 2. Note the inner diameter at the IVC lower end of ID=28mm, for the system to fit in our existing cryomagnets. Option to have a second pair of IVC vacuum cans with larger sample space (ID=45mm) and shorter length, to fit in our helium cryostats. Option to be priced separately.

• Insert probe flange ISO NW50 with sliding seal

• Lifting eyebolt on top of the insert probe

• Pressure gauges/transducers on the He3/He4 reservoir (dump), DR insert inlet, DR insert outlet, and pump outlet at a minimum. Pressure measurements (dump, condensing, still and pump outlet)

• The IVC’s shall be constructed of thin-walled (.010-.020)” aluminum in the neutron-window region below the Mixing Chamber.

• Space below mixing chamber: 60 mm and other relevant dimensions to fit our existing host equipment are shown in Figure 2.

• Lower portion of the Mixing Chamber shall be gold plated.

• Gas Handling system will be located (25-30) feet away from the insert. Try to mount all components in one tower/cabinet not larger than dimensions shown in Figure 3.

• Gas handling system including dry pumps, pneumatic gas handling, PC. Important note:

Seller to provide control system source code.

• Hoses from the gas handling system to the insert shall be 30 feet (9.1m) long stainless-steel flexible hose.

• Gas Handling System (GHS) tower to not exceed dimensions shown on Figure 3.

• Technical drawings: step files with relevant dimensions to incorporate in our own models to be provided later on award if selected with details only to the extent that it does not infringe on proprietary rights.

Figure 2: Dilution refrigerator insert dimensions to fit host cryostat and magnet systems.

Figure 3: Approx dimensions for GHS tower.

FACTORY TEST:

Vendor to report the cryogenic performance, cool-down within time specifications, base temperature and a selection of temperature control points. Tests at the manufacturer facility to be done with their own He3/He4 mixture.

All vacuum components shall be subjected to leak checks. Leak rate shall be < 1E-7mBar-L/Sec Continuous operation of DR refrigerator at base temperature for minimum of 48 hours.

SITE ACCEPTANCE:

As part the installation by vendor, the cryogenic performance of the dilution refrigerator inserts, the base temperature and a selection of temperature control points will be measured using ORNL existing host cryostat and VTI.

ORNL will load its own He3/He4 mixture when the system arrives onsite, with same volume, and same ratio composition.

All vacuum components shall be subjected to leak checks. Leak rate shall be < 1E-7mBar-L/Sec Continuous operation of DR refrigerator at base temperature for minimum of 48 hours.