Cryostation FAQ

Glad You Asked!
Here are answers to some Frequently Asked Questions about the Cryostation:

1. How do you keep contaminants out of the chamber?

-The system will purge the cryostat with dry nitrogen gas automatically. The user connects his nitrogen tank to the Cryostation Control Box, 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.

2. I am not familiar with cryogenics systems; How much learning is required?

-Having an instrument you could simply bolt to an optics bench, insert a sample, push "cooldown" and not even think about vibrations, temperature stability or liquid cryogens was the goal. This makes it simple and efficient for both the researcher or grad student who is new to cryogenics and the “hardened criminal” in cryogenics. There are a few basics to learn about mounting a sample so that it has good thermal communication with the sample mount, but again, you’re not on your own. The experts at Montana Instruments Corporation or their worldwide network of trained technicians can help you.

3. Is it possible for the users to change the window material themselves?

-Yes. Both the vacuum windows and the cold radiation windows are 30mm and 20mm diameter substrates, so the user can choose any material or AR coating. The Cryostation uses a cold window holder system which allows the user to easily exchange windows. The cold window holder supports the 20mm diameter windows substrate by grasping the outer surface gently and evenly enough to not create stress-induced birefringence, but firmly enough to cool the window and protect the sample from 300K radiation. The cold window holder position is also adjustable such that the user can locate the cold window and the sample close to the warm window for microscopy or high angle reflectance applications. The warm window holders simply use an o-ring seal and a lock-ring to mount a 30mm diameter substrate. Please see the associated photo of the warm window, cold window adjusted close, and empty adjustable sample holder.

Warm window, adjustable cold window, and adjustable sample holder.

4. 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 4.2K, and a base temperature of approximately 2.85K even with all 5 cold windows installed. At higher temperatures (15K), the system can handle about 2 watts of thermal load. Contact our engineers for help in estimating the working temperatures with your anticipated loads.

5. How long will it take to cool from 300K to 4K?

- The Cryostation surpasses 4K in about 108 minutes. The system achieves this by automatically running the compressor at higher and higher flow rates as the helium gas cools, maximizing its cooling rate.

6. Will the system work on both a floating or non-floating table?

-For best vibration results, a floating bench is recommended. However, a floating bench is not necessary and it will work fine on a rigid bench. It is important, however, to bolt the system down to the bench.

7. What is the size of your sample enclosure, and how does it integrate with the system?

- The size of this sample area is 53mm in diameter by 40mm high. For access to the sample area, electrical connections and thermal lagging locations, the user removes the lid and the top half of the sample stage, which can be removed by simply lifting it off (in the photo below, this is the upper half black portion, and the lower half stays bolted rigidly to the table). The lower half of the sample area contains all of the vibration isolation, temperature stabilization, rigid sample mount, near-zero drift over entire temperature range, instrument control, and user electrical feedthroughs. There is a lot of technology sitting below the sample area! Please see the line drawing of the Cryostation standard sample chamber here: Cryostation Line Drawing

The sample and electrical connections are accessible by lifting off the lid and top section of the sample housing.

8. Is a sample mount included?

- A versatile sample mount is included which allows adjustable sample position for spectroscopy or microscopy through any of the 5 windows. The sample may be mounted in the center with access from all 5 windows for transmission applications, or adjusted up close to one of the windows for high angle reflectance or microscopy applications. The sample mount may also be positioned at 45 degrees to the windows for further reflectance angles.

9. How can the user connect sensors and devices into the sample area?

- The user is provided with 9 electrical connections into the sample area, including 4 miniature connectors and thermal lagging locations for wires provided. The user plugs into these outside the vacuum space with a standard 9 pin D-shell. Once the radiation shield is removed, there are small grooves in the flange which supports the radiation shield. For thermal lagging, the user lays the wire into one of the grooves with a small amount of low temperature thermal grease. We anticipate these electrical feedthroughs will be used for piezo positioners, cooled IR sensors, thermometers, heaters, motors, solenoids, diodes and more. There is ample space on the 3K stage for positioning devices. This is a flexible instrument that can be used for many types of applications.

10. Are other window coatings available? How about from 200nm to 2microns?

-Yes, we can provide windows with specific AR coatings, and specific substrate materials. The product includes fused silica windows with an AR coating from 400 – 1000nm. We can add a set of warm and cold windows coated at 1200-1600nm to cover the range close to 2um. There is not a good single coating to cover the entire range, so multiple windows are necessary. Additionally a set of windows from 250 – 700nm could be used to get closer to 200nm.

11. What is the communication interface of the system? USB?

-Yes, USB. A mini 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 an expert from Montana Instruments or our worldwide service network the ability to troubleshoot the system online rather than needing to have a technician travel on-site or send the system back.

12. The system comes with Windows based software; can I take control of the Cryostation for automating my experiment.

-The Cryostation is controlled by Windows-based software which has been developed specifically for the system. An OLE interface is built into the application to enable external control of the system.

13. Does the Cryostation stand freely on the optical table or does it require some kind of external support from off the table? Is the Cryostation compatible with a floating table?

-Yes, the Cryostation simply bolts to the floating optical bench in the same way other optics do. We have gone to great lengths to ensure that the engineered (patents pending) system does not impart vibrations to either the optics on the floating table or to the sample. We used a capacitive displacement sensor with picometer resolution referenced to the optical table to measure vibrations both cold and warm. Vibrations have also been tested on a small 3'x5'x4" floating table to ensure that vibrations will not be a problem on smaller optical tables. Typical measured sample vibrations on this table are approximately 1.6 nanometers peak to peak, and 0.26 nanometers RMS.

14. Does the Cryostation include a vacuum pump?

-Yes, the Cryostation includes a Control Unit which automatically pulls a vacuum before the automatic cooldown. The pump and other controls may be operated manually as well, from the manual operations page of the control interface.

15. Do I need to buy a temperature controller separately?

-No, the Cryostation electronics includes both system and user thermometry which is fully functional and calibrated. Utilizing this thermometry, the system will automatically stabilize at the input temperature setpoint.

16. What components are included with the system?

-The main Cryostation unit is typically mounted to a floating or fixed lab table. There are two additional units, the Cryostation Control Unit, and the Variable Flow Helium Compressor which sit on the floor separately and can be pushed under a table out of the way. A small laptop is also provided for user control with a user interface designed specifically for the Cryostation.

17. What is the type of the cryocooler? PT or GM?

-The cryocooler is an SHI RDK-101D, with a Gifford-McMahon cycle (GM). There are a couple advantages of the GM machines. One is that they are more efficient, and can be run on approximately 1kW of power input. Also, the operating frequency can be varied for faster cooldown, standby low power mode, and other features that are valuable for researchers. These cannot be accomplished with a pulse tube (PT). Also since the cryocooler is isolated from both the optical table and the sample, vibrations are no longer a consideration.

18. 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 to 3kW. As part of the automatic cooldown sequence it will run at higher flow rates during cooldown and then back off to operating conditions necessary to maintain your setpoint 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 that 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 warmup.