Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Closed Cycle Refrigerators (CCR)

System Description Temperature Range(K) Other Capabilities Available Instruments
Low T Low Power CCRs 6-325 High Voltage (6kV) All
Low T High Power CCRs 3 - 325 Electromagnet Mountable All except HFBS
High T High Power CCRs 14 - 800 High Voltage(6KV) All except HFBS
Top Loading CCR 5-700 Gas Handling, High Pressure All

General CCR Information

How They Work

 

  • Our CCRs use the Gifford-McMahon Refrigeration Scheme
    • Helium gas is the refrigerant
    • The gas compressor (operating near room temperature) and the cryogenic expansion cylinder (cold head) are thermally linked by a regenerator or thermal storage device
    • The gas is driven through the 4-step cycle shown below
Working principles of CCRs
  • Temperature Sensors

    Tempeature sensors are a standard item in the CCR systems. Silicon diode DT670 sensor is the most common and is used for low temperature measurements. Platinum sensor is used for high temperature measurements. Cernox sensors are used for CCR tails in magnetic fields. Thermocouples are sometimes used in rare cases. Temperature sensor information for individual systems is available in the booklet attached to each system. The information includes the type, temperature range, corresponding controller curve and physical location. Be sure to verify this information before starting the system.
  • Temperature Controllers

    These are another standard piece of the CCR system. We use Lakeshore 340/331/335/336 controllers on all of the systems and they all use identical cabling. This allows us to easily diagnose problems and have plenty of spare parts on hand. The main difference between these controllers is that the 340/336 can supply 2 amps of heater output and the 331/335 can supply only 1 amp. For this reason the 340/336 are used on all of the high temperature systems which require more heater power. Be sure to verify that all sensors are reading at room temperature and contact a sample environment team member if you have problems.
  • Sample Space and Sample Mounting

  • PID Parameters

    In general PID parameters should be determined and loaded into the controller before a CCR system is put into service. However, sometimes parameters get changed by users and are not returned to the standard values. Double check that PID values are correct by comparing those stored in the controller with those in the system manual.
    Note: These new PID values take advantage of a feature called a PID zone table. Below you will find a link to a one page manual on how to load a PID zone table.

Setup

Many of the different items that make up the CCR systems are standard and interchangable among the different systems, somtimes even the different types of systems. These items include the sample block, heat shield cans, temperature controller, sensor and heater cables and vacuum can. New systems are generally bought to conform to the standard setup to make integration easier. This also makes going in-between the different systems easier for experienced and novice users. Another important aspect of a CCR system are PID parameters. These parameters vary depending on the setup of each type of CCR and sometimes even on the exact system in use.

Contacts:

 

  • tanya.dax [at] nist.gov (Tanya Dax)
  • qiang.ye [at] nist.gov (Qiang (Alan) Ye)

 

 

Created June 6, 2017, Updated December 17, 2019