1. WHAT COMPONENTS ARE INCLUDED WITH THE SYSTEM?
The Cryostation includes the cold head and sample chamber, which is all fixed to the optical table. The Cryostation Control Unit, with the electronics and the vacuum pump, and the Variable Flow Helium Compressor are also included. These units generally sit on the floor under the optics table. There is also a small laptop provided for user control with a user interface specifically for the Cryostation.
2. DO I NEED TO PURCHASE A TEMPERATURE CONTROLLER SEPARATELY?
No, the Cryostation electronics include both system and user thermometry which is fully functional and calibrated. Utilizing this thermometry, the system will automatically stabilize at the input temperature set point, based off of the PID of the platform thermometer.
3. DOES THE CRYOSTATION INCLUDE A VACUUM PUMP?
Yes, the Cryostation includes a Control Unit which includes a diaphragm pump which automatically pulls a vacuum prior to the cool down. The pump and other controls may be operated manually as well, from the manual operations tab of the control interface.
4. WHAT TYPE OF CRYO-COOLER IS THE CRYOSTATION?
The cryo-cooler is an SHI RDK-101D, which is a Gifford-McMahon style. There are a couple advantages to the GM machines. One is that they are more efficient than pulse tube cryo-coolers, and can be run on approximately 1kW of input power. Also, the operating frequency can be varied for faster cool down. Since the cryo-cooler is isolated from both the optical table and the sample, vibrations are dampened.
5. HOW DO YOU GET THE VIBRATIONS SO LOW?
To address the challenges of moving components due to vacuum, the Cryostation uses symmetric bellows to create a net zero force on the sample chamber due to the vacuum inside the flexible bellows, see Figure 1. In the center is the tall cryo-cooler assembly, with a horizontal cold finger reaching into the sample chamber on the right. Two bellows are placed symmetrically at the base of the cooler support in the direction of the cold finger axis. If the system had a single bellows on the right, the drop in pressure to a vacuum would compress the bellows and exaggerate the motion of the cold finger laterally. This not only would cause a displacement of thermal components, but would also require an equal and opposite force from springs or dampers, which only add to the force transmission across the bellows and increases vibration of the sample chamber. With two bellows in place, the pressure differential is balanced such that there is no lateral force on the sample chamber, no displacement of thermal components even when vacuum levels change, and minimal force transmission across thin bellows. The patent claims are detailed more in US patent 8746008 B1, “Low vibration cryo-cooled system for low temperature microscopy and spectroscopy applications.”
Figure 1: Symmetric bellows to reduce effects of thermal contraction
6. WHAT IS THE COOLING POWER?
The power the system can dissipate depends on the temperature of the platform. We typically see about 100mW of cooling power with the sample platform at 4K, and a base temperature of approximately 2.9K even with all 5 cold windows installed. At higher temperatures, 15K, the system can handle about 2W of thermal load. Contact our engineers for assistance in estimating the working temperatures with your anticipated loads and/or see our Cryostation Heat Load Map.
7. HOW LONG WILL IT TAKE TO COOL FROM 300K TO 4K?
The Cryostation reaches 4K in about 110 minutes for a standard system. If your system has added options such as RF coax, wiring, or positioners, it will take longer to reach base temperature depending on the heat load added. The Nanoscale Workstation reaches 5K in about 9 hours with no extra options.
8. WHAT IS THE SIZE OF THE SAMPLE SPACE, AND HOW DOES IT INTEGRATE WITH THE SYSTEM?
The size of the sample area in the Cryostation is 53mm in diameter by 63mm high, however there are several options for the Cryostation housing, please see Housing and Window Options. The Nanoscale Workstation sample area is 195mm in diameter and 71mm high. Please see the dimensions in the Nanoscale Workstation datasheet. For access to the sample area, electrical connections and thermal lagging locations, the user removes the lid, vacuum housing, and radiation shield. The lower half of the housing contains the vibration isolation, temperature stabilization, and rigid sample mounting which allows for near-zero drift over the entire temperature range. There is a lot of technology sitting below the sample area!
9. IS A SAMPLE MOUNT INCLUDED?
A versatile sample mount is included in the standard system, which allows adjustable sample position for spectroscopy or microscopy through any of the 5 windows. The sample may be mounted in the center for transmission applications, or adjusted up close to one of the windows for reflection experiments. The sample mount may also be positioned at 45 degrees to the windows for scattering or reflection. Please see the article on Various Sample Mounting Configurations for Optical Access. For systems with options, Montana Instruments offers several customized sample mounts for various applications; for an idea of these sample mounts please see Sample Mounting Options. Our design engineers are available to discuss your sample mounting needs.
10. HOW CAN THE USER CONNECT SENSORS AND DEVICES INTO THE SAMPLE AREA?
The user is provided with 27 electrical connections into the sample area. There are 20 user connections at the back of the sample board to connect to your instrumentation outside of the system; these 20 user connections inside the vacuum space are connected to the 20 external user connectors through the sample board, allowing the user to input or output signals. These connectors are typically used for piezo positioners, thermometers, or heaters. There are an additional 7 connections throughout the sample board for user thermometers or/and heaters. Additional wires can be added with a microD25 connector, or RF coaxial cables at a side panel in the base of the housing.
11. WHAT IS THE COMMUNICATION INTERFACE OF THE SYSTEM?
The communication interface of the system is USB. A laptop is included which runs a Windows based utility as the user interface to the system. With internet access, this allows the user to control the Cryostation from another computer via network connection, and also allows a Montana Instruments service engineer to troubleshoot the system remotely.
12. CAN I AUTOMATE MY EXPERIMENT?
Yes, using LabView or any other code, the user can build in temperature control of the system with their other experiments. Montana Instruments provides sample LabView Vis and DLLs for the user.
13. HOW DO YOU KEEP CONTAMINANTS OUT OF THE CHAMBER?
The system will purge the cryostat with dry nitrogen automatically upon warm up. The user connects a nitrogen tank or line to the Cryostation Control Unit and the system will automatically purge and vent with dry nitrogen. A positive flow of nitrogen can also be maintained while changing the sample if the user wishes to keep the system free of moisture and contaminates. When the system is not in use, some users keep the system under vacuum.
14. I AM NOT FAMILIAR WITH CRYOGENICS, HOW MUCH LEARNING IS REQUIRED?
Having an instrument you can simply bolt to an optical table, insert a sample, push “cool down” and not even think about vibrations, temperature stability, or liquid cryogens was the goal when developing the Montana Instruments Cryostation. This makes it simple and efficient for the researcher or graduate student who is new to cryogenics, as well as the expert in cryogenics. There are a few basics to learn about mounting a sample so that there is good thermal contact with the sample mount, but you’re not on your own. The experts at Montana Instruments can help you.
15. HOW DOES THE CRYOSTATION MOUNT TO THE OPTICAL TABLE?
The Cryostation is bolted to the optical table at 45 degrees or 90 degrees to the holes in the table. It is bolted in three places around the sample chamber, two places in the middle, and two at the back. For vibrational considerations, it is important that the system is bolted to the optical table. The user can use either a floated or non-floated optical table. Montana Instruments tests the systems on 3’x5’x4” optical tables and achieves <5nm peak-to-peak in vibrations, although most users mount the system to a large, vibrationally isolated optical table.
16. CAN USERS CHANGE THE WINDOWS?
Yes, both the vacuum windows and radiation shield windows are typical sizes, 50mm, 30mm, or 20mm diameter substrates, so the user can choose any material or AR coating. The inner radiation shield windows are a press fit, and the whole assembly can be unscrewed from the radiation shield, which allows the windows to be easily exchanged and the window distance to change to allow the sample to be closer to the vacuum window. The vacuum window can be exchanged by removing the retaining ring. The standard vacuum windows are 50mm in diameter and 4mm thick, and these can be replaced with any 50mm diameter, 4mm thick windows. If you have specific wavelength needs we will work with you to get the proper material installed or provide the specifications for the system if the user chooses to install their own windows.
17. WHAT UTILITIES ARE REQUIRED (POWER, WATER COOLING) TO RUN THE CRYOSTATION?
The Variable Flow Helium Compressor runs on single phase 220V, is air-cooled and draws between 1kW and 1.8kW of power. As part of the automatic cool down sequence it will run at higher flow rates during cool down and then back off to operating conditions necessary to maintain your set point temperature. This variable flow control reduces power and noise significantly. Between experiments and overnight, you can operate the system in standby mode, which further reduces power consumption. As far as other utilities, we recommend the user connect the Cryostation to a tank of dry nitrogen gas. This will help keep the surfaces and optics clean and free from moisture, as well as facilitate a faster automatic warm-up.
18. DO YOU OFFER A WATER COOLED COMPRESSOR OPTION?
No, we do not offer a water cooled compressor option. Some users prefer to place the compressor in a utility closet or service hall; for this we offer 30 foot helium hoses and communication cables. This places the compressor out of the lab and prevents any warming of the laboratory environment. Some users who do not have access to an external room route the warm air coming from the back of the compressor directly into the HVAC system. Please contact Montana Instruments to explore these solutions.
19. ARE YOUR SYSTEMS CE CERTIFIED?
Yes, our products conform to the following CE directives: 2014/30/EU - Electromagnetic Compatibility Directive and 2014/35/EU - Low Voltage Directive. More information on these directives can be found by following the hyperlinks to the European Commission website. A copy of our Declaration of Conformity is also available upon request.