S700X SQUID Magnetometer

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Click image to enlarge

The S700X SQUID Magnetometer is the most sensitive instrument for DC and AC measurement of magnetic properties as a function of magnetic field and temperature. The SQUID sensor at the heart of the system has an input noise power sensitivity of approximately 10-30 Joules per root Hz. This energy sensitivity is 108 better than any semiconductor device and accounts for the instrument's ability to resolve extremely small magnetic signals with accuracy and speed.

The S700X has several modes of operation. The most widely used is the measurement of total magnetic moment made by moving the sample through a set of pick-up coils. During the measurement the sample temperature and applied magnetic field are precisely controlled. The second order gradiometer configuration used for the pick-up coils is insensitive to the externally applied field but allows samples of 10-11 Am2 total moment to be resolved with ease.

The superconducting magnet for the system is produced at Cryogenic’s in-house facilities using our proven technology for high field superconducting magnets. These magnets are manufactured using copper stabilised filamentary superconductor which is then vacuum impregnated with epoxy resin to form a composite structure of excellent mechanical strength and electrical insulation. The pick-up coil set is attached as part of the magnet structure.

A built-in magnetic shield made of mu-metal reduces the earth’s field providing a sample environment of typically 10 milligauss. The combination of these two features with the low current option allows accurate measurements in the range of 10 milligauss to 150 gauss.

The system also has a full magnetic shield built into the cryostat to protect the measurement system from external influence and provide a background field of typically 100 micro-tesla at the sample measurement point

Re-condensing cryostat with integrated VTI and high homogeneity magnet (R-S700X).

  • No liquid helium refills
  • 1 Watt Pulse Tube cryocooler for true Zero boil-off system.
  • Sample sits in liquid helium   
  • Requires a 7.0 kW compressor which is water cooled
  • Initial cool down time: 36 litres for 12 litre reservoir
  • Liquid helium reservoir: 25, 18, 12 litres
  • Helium liquefaction rate: Around 8 liters/day

CRYOGENIC Ltd. offers its closed cycle SQUID Magnetometer. The S700X-R Susceptometer has a cryostat incorporating a 1 Watt 4K cryocooler so that it never requires liquid helium refilling. The cryocooler chosen for this system has the virtue of a long maintenance interval and low maintenance cost, therefore reducing the cost of ownership to the minimum.

The pulse tube cryocooler is very quiet in operation. Vibration is insignificant and careful patented internal design keeps the magnet and SQUID circuit at constant temperature. This gives the very best signal sensitivity with very low drift making it the most sensitive magnetometer available.

Measurement Options

Helium-3 Insert for sub-Kelvin measurements

The Helium-3 probe is built to allow the standard system to measure samples down to below 300 mK. The miniature helium-3 pot fits inside the standard variable temperature sample space, and using only the cooling power of the VTI and two internal temperature-controlled sorption pumps, the sample can be maintained at any temperature from below 300mK to above 300K. A working volume of 0.9cc of liquid Helium-3 is sufficient to maintain temperatures in the 300mK range for up to 12 hours.

Linear Motor

A miniature linear motor of total travel 40 mm is used to move the sample; typical measurements are made with a 25mm total movement at 1 – 3 Hz. The signal from the moving sample is detected and measured by the SQUID connected to the pickup coil. The sample displacement is also measured to allow a phase and position lock of the detected signal. The sample can be positioned and moved over the full 150mm range with the stepper motor driven sample platform. This head is the same as in the S700X SQUID Systems and long movement measurements can be made as in the normal detection mode.

The SQUID-LM (Linear Motor Technology) offers fast and accurate measurement using the linear motor drive. The measurements are made by using a repeated rapid sample movement over 20mm pick up coil set. This gives the advantages of increased speed and higher precision with the full analysis power of the system using the standard 2nd order pick-up coil.

Dynamic Range Extender

The standard measurement range (106 total dynamic range) is from 10-11 to 10-5 Am2 can be extended to measure signals as large as 5 x 10-3 Am2. The extender is automatically activated during measurement if the sample moment is above the standard dynamic range. This option may be retro-fitted to an existing insert.

Oven Insert for Extended Temperature Range (<1000K)

In normal operation, the S700X SQUID system has a continuous temperature range of 1.6 to 400K. With the Oven Insert option this is complemented by allowing measurements to be performed in the high-temperature range 300K-1000K.

Transverse Measurement Facility

Simultaneous multiple axis measurements are possible by the addition of secondary (and optionally tertiary) pick-up coils in the main magnet assembly. This enables measurements of sample anisotropic effects. Included with the transverse axis facility is a motor which permits rotation of the sample, controllable to 0.1 degree. This facility allows simultaneous measurement in two or three axes.  

Horizontal Rotating Sample Platform

For materials that may exhibit anisotropy or other angular magnetic property behaviour, Cryogenic offers a rotation option to permit the sample to be rotated and evaluated by the operator under computer control.

A single-axis configuration, the sample is rotated through 360 degrees around the horizontal axis.