Specifications_v.2_8-24-2023.pdf

SPECIFICATIONS

NB687080-23-01212

Horizontal dry dilution refrigerator for synchrotron spectrometer

Background The NIST Quantum Sensors Group develops arrays of superconducting sensors for applications in metrology, materials analysis, and astrophysics. These sensors typically operate at temperatures in the milliKelvin range which requires specialized refrigeration technology. We are developing a soft x-ray spectrometer to be mated to a synchrotron beamline. The requirements to house our sensors while being compatible with the beamline lead to many physical constraints on shape and size. The spectrometer will have optical access port facing sideways into a sample chamber under separate vacuum, which leads to the requirement of a horizontal design.

Minimum Specifications The following is a list of required features:

1.1 Programmatic

- This refrigerator will be dedicated to a single project, housing a soft x-ray spectrometer mated to a specific synchrotron beamline. There is only on location at the beamline where this mating can occur, and that location has many limitations that put strict requirements on the size and shape of the dilution refrigerator. The refrigerator must be horizontal, in that the central axis of the circular vacuum cans and radiation shields is perpendicular to gravity. The refrigerator must be compact. The most critical dimension is the distance from the front of the vacuum can to the back of the cryostat, including any rigidly attached items. All other dimensions should be minimized to the extent reasonably possible.

1.2 Physical

- To have multiple internal temperature stages between room temperature and the mixing chamber, with radiation shields, heat sinking of wiring, thermal breaks between stages. In this document we will refer to the stages nominally as 40K, 4K, still and mixing chamber and understand that the operating temperatures will vary slightly from these values.

- Horizontal, the central axis of the cylindrical vacuum cans, radiation shields as well as the mixing chamber flange, the still flange, the 3K flange and a 40K flange are perpendicular to gravity when operated.

o Removal of vacuum cans and radiation shields such that all internal wiring can be reached for modification must be easily achieved without disassembly of any of the cryostat internals.

o Robust against applied force: when up to 1000 of lbs of force is applied that pulls the vacuum can along the central axis away from the rest of the cryostat, the cryostat has minimal deformation and maintains cooling performance.

Cylindrical shields at each temperature stages remain concentric. The central axis of each shield should vary by less than 0.5 mm with applied force.

- Compact, in that the distance from the front of the vacuum can to the back of the refrigerator, including other items rigidly attached to the cryostat must be less than 4.5 feet. No other dimension of the refrigerator may exceed this dimension.

o To achieve a shorter overall length, we prefer to have less separation between temperature stages than is commonly provided. For example, between 4K and 40K we need only enough room to mount the requested Low Noise Amplifier brackets and populate them with wire up Low Noise Amplifier. To be finalized in discussion post-contract.

Generic Specifications Template o Flexible still line pumping tube, so the refrigerator may be translated by up to 4 feet along the axis of the vacuum can be relative to the gas handling system while operating.

- Extensive vibration isolation. The Vendor shall provide documentation demonstrating that vibration amplitudes on all flanges are < 0.1 microns over the frequency range 0-200 Hz while operating.

o Use of a remote motor for the pulse tube cooler.

o Spring/bellows pulse tube mount

- Mixing chamber plate diameter large enough to accommodate all wiring specified below with 4 inch or greater diameter clear area in the middle to which we can mount our devices.

- Radiation shields shall be provided for 40K, 4K, the still, and the mixing chamber.

- The vacuum shell shall be constructed of aluminium for ease of handling.

- To enable detector development applications, provisions shall be made in the radiation shields and vacuum shell to attach NIST-supplied optical ports. These provisions shall consist, at a minimum, of a hole for each port and a bolt circle to attach each port. The port in the vacuum shell shall be o-ring sealed to maintain vacuum integrity. NIST seeks to develop detector packages up to 200 mm in diameter and preference will be given to refrigerator designs compatible with this size detector package.

1.3 Performance of the refrigerator

- Cryogen-free operation, i.e., pulse tube cooler is used instead of liquid helium to cool down to 4 K.

- Ability to operate for at least 2 months without use of liquid nitrogen cold trap.

- Guaranteed base temperature of 10 mK or below with all vendors supplied wiring installed and, on any vendor supplied stand.

- Cool-down time to 10 mK of less than 22 h with the requested flexible still line.

- Cooling power of at least 40 W at 45 K, at least 1.0 W at 4.2 K, and at least 250 microwatts at 100 mK.

1.4 Gas handling system

- No membrane pump shall be used in the 3He—4He mixture circulation since they have short service periods, and the rupture of the membrane leads potentially to loss or contamination of the mixture.

- The dilution unit shall not have any soft solders. Soft solders are known to develop micro-fractures and cold leaks overtime.

- All pumps and compressors in the mixture circulation system shall be oil-free.

- All control functionality integrated into the gas handling system unit, meaning no separate user interface unit. Preference will be given to refrigerators with smaller amount of required floor space.

1.5 Operation and Software

- Heat-exchange-gas-free operation, i.e., the Device shall have only a single vacuum feedthrough stage at room temperature, which implies that no heat exchange gas can be used in the large vacuum can.

- Fully automated operation with computer-controlled valves and pumps. Press-of-a-button vacuum can pump out and cool-down control.

o User extensible control of cooldown process, for example user could remove a step, make a step longer, or change the end criteria for a step.

o Preference will be given to refrigerators with more extensible control. The ability to control or query additional user supplied hardware during the cooldown process is highly desired. For example, the user may want to control an additional vacuum valve, or condition cooldown progress on external interlocks or external pressure readings.

o An option may appear on the contract control to offer soft-pump out and venting of the vacuum can. The maximum pressure rate of change permissible is 1 torr/sec.

One method to achieve this is to first rough pump the vacuum can through a needle valve until a threshold pressure is achieved, then switch to full speed pump out and proceed with cooldown of the cryostat as normal. When venting the system, it would first vent through the same needle valve until a threshold pressure is reached, then vent through a larger conductance valve.

- Documented method to the control temperature setpoints for temperature control circuits or heater circuits as well as to query temperatures from a python script while temperatures are also being recorded and displayed by vendor supplied software.

- An interface with possibility to override the automation and to fully control the Device manually.

- Fully automated preparation to separate the cryostat from the gas handling system that protects the He3 mixture. Preference will be given to refrigerators that provide more automation when reconnecting the gas handling system to the refrigerator.

1.6 Experimental wiring

- All wiring to be included in contract as an optional purchase, valid for at least 6 months after contract signing. Our intention is to execute the option in a timely fashion so that the wiring is installed when the refrigerator is delivered.

- DC Wiring o QTY3 sets of 36 AWG phosphor-bronze 12 twisted pair to 4K, continuing with the same number of NbTi/CuNi superconducting twister pairs from 4K to the mixing chamber. To include a break-out box with fisher connector at room temperature and appropriate thermalization.

o QTY1 set of 36 AWG phosphor-bronze 12 twisted pair to 4K, to include break-out 40K. To include a break-out box with fisher connector at room temperature and appropriate thermalization.

- Amplifier Wiring Wiring, mounting brackets, etc for mounting QTY20 low noise amplifiers (for example the LNF-LNC4 from Low Noise Factory) at 4K. To include wiring to room temperature and connectors at both room temperature and 4K, as well as necessary coaxial sections and DC sections of wiring to go to the LNA at 4K.

These amplifiers should reach as low temperature as reasonably achievable.

o Wiring, mounting brackets, etc for mounting QTY20 low noise amplifiers (for example the LNA-20-04000800-07-10P from Narda-MITEQ) at 40K. To include wiring to room temperature and connectors at both room temperature and 40K, as well as necessary coaxial sections and DC sections of wiring to go to the LNA at 40K. These amplifiers need to reach a temperature somewhat above 40K, so they should be mounted between 40K and room temperature.

o The mounting scheme must allow for the LNAs to be installed on the coaxial lines with superconducting segments described below.

- Microwave wiring o Use SMA connectors.

o Rotation resistant hermetically sealed at room temperature, preference will be given to welded connectors.

o To include appropriate thermalization.

o QTY 20 coaxial wires from room temperature to the mixing chamber, with superconducting sections below 4K.

No additional attenuation.

Room temp – 4K: 2.19mm SCuNi-CuNi coax 4K – mixing chamber 0.86 mm NbTi-NbTi coax o QTY20 coaxial wires from room temperature to the mixing chamber, with resistive section below 4K.

With cryogenic compatible attenuators of 3 dB, 10 dB, 6 dB, 6 dB at the 40K, 4K, still and mixing chamber plates.

Room temp – 4K: 2.19mm SCuNi-CuNi coax 4K – mixing chamber 0.86 mm SCuNi-CuNi coax

1.7 Diagnostic wiring and thermometry

- The refrigerator shall be provided with a complete set of diagnostic wiring and thermometry consisting, at a minimum, of heaters and resistive thermometers on the 60 K, 4 K, still, and mixing chamber stages. Electrical connections to the resistive thermometers shall be filtered to prevent electromagnetic interference. All wiring shall be heat sunk at each successive stage of the refrigerator.

- Temperature measurement and control equipment including thermometers and a high-level resistance bridge with a PID controller such as Lakeshore 372S/AC. The resulting temperature stability at the mixing chamber plate must be stable to better than the 100 uK level below 100 mK, <5 uK level preferred.

- A warm-up heater shall be included to enable fast warm-up of the refrigerator without the use of exchange gas. The warm-up heater must include at least one heating element on the 4 K plate and a programmable power supply, and full integration with the control software. Preference will be given to refrigerators with a warm-up time of 13 hours or less.

- An option may appear in the contract for an additional mixing chamber thermometer, valid for at least 6 months.

o An additional thermometer on the mixing chamber, readout on another channel on the temperature controller.

o Easily relocatable to user installed sample boxes thermally sunk to the mixing chamber, but up to 18 inches beyond the mixing chamber plate.

o Excess wiring coiled in a compact and easily repeatable fashion when mounted directly on the mixing chamber.

o Capable of uK temperature resolution on timescales less than 10 s o Documented method of use with PID temperature control achieving similar stability to the primary mixing plate thermometer

1.8 Documentation

Full technical documentation and user manuals in English must be included as pdf-files and in printed format.

Delivery

• The Vendor must deliver the dilution refrigerator, gas handling unit, mechanical support, all pumps, and Helium-4. We will supply the necessary Helium-3.

• Delivery shall be complete by no more than 8 months ARO.

• Delivery will be to NIST, 325 Broadway, Boulder, CO 80305 POB 5000, Rm. 111, Bldg.

743, NSLS-II, Upton, NY 11973, United States.

Installation

• The Vendor must install the dilution refrigerator, gas handling unit, mechanical support, all pumps, and Helium-3/Helium-4 gas mixture.

• Installation shall be complete by no more than 8 months ARO.

• Installation will occur in in a lab space at the NIST Boulder Laboratories. Beamline ID7 at the National Synchrotron Light Source-II at Brookhaven National Laboratory in Upton, NY. This a ground floor laboratory with a large floor with various pieces of experimental equipment. The space is not electrically shielded.

• The installation site can be examined by the Vendor beforehand. Detailed requirements for the site must be supplied by the Vendor at least 3 months before delivery.

Testing and Acceptance

• Vendor shall perform factory testing that demonstrates the desired performance specifications prior to delivering the unit.

• Vendor shall perform testing at the NIST Boulder Laboratories. NSLS-II that demonstrates the desired performance specifications prior to acceptance.

• Vendor shall provide no less than 2 days of training for at least 2 NIST personnel at the

NIST Boulder Laboratories prior to acceptance.

Warranty Warranty period of at least two years for the components manufactured by the supplier and for the installation of third-party components. Third-party components shall be covered by a warranty not shorter than 12 months. Warranty shall cover all labour, travel, parts, and other costs required for maintaining the guaranteed performance of the device. Warranty shall take effect on the day of final acceptance. In case of warranty repair, the service shall begin no later than three business days from the moment the customer notifies the supplier.

Security N/A