S700X SQUID Magnetometer
Introduction
The S700X SQUID Susceptometer is the most sensitive instrument for DC and AC measurement of magnetic properties as a function of magnetic field and temperature. Numerous different experiments may be performed with this unique instrument.
The SQUID sensor at the heart of
the system has an input noise power sensitivity of
approximately10-30 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.
Key Benefits
The following competitive features are provided in the basic system package free of charge.
Continuous Measurements
To make continuous measurements in a changing background field, we include the Oscillating Mode facility. Under this condition the sample is oscillated vertically over a distance of few millimeters. The detected sinusoidal signal from the SQUID is proportional to the magnetic moment of the sample.
Fast Temperature Changes
The ultra light design of the sample chamber allows fast temperature changes and stabilizes quickly, because there is hardly any heat capacity to overcome other than that from the sample holder and the sample. A second temperature control loop regulates the temperature of sample space tube in order to enhance the performance at higher temperatures.
Any temperature within the wide range of 1.6K to 370K can be kept continuously, as long as there is liquid helium in the main reservoir.
Magnetic Shielding
Based on the experience in the field of Rock Magnetometers, the S600's shield system consists of a mumetal can and a niobium shield, which reduces the background field to as little as 0.5 mG. The system is fully shielded against external noise and changes in the background field.
Data Acquisition
The 16 bit DAQ with software controlled preamplifiers can cope with signals of 130dB dynamic range. An optional range changer widens this span to 190dB.
User Friendly
Great care has been taken to make the system as user friendly as possible. The new LabVIEW software provides an open software environment that allows the user direct control of all features of the system with real-time graphical displays of all the relevant functions.
The data gained during a measurement are analyzed in terms of magnetic multipoles. This unique feature gives a dipole moment independent of the sample shape and is error tolerant in respect to sample position. A feature which allows inexperienced users to perform reliable measurements.
An on-line help feature, which is available at any stage of the experiment, provides support to newcomers making their first measurements and allows advanced users to optimize the system performance according to their requirements.
Optional Features
AC Mode Measurement Facility
An AC measurement option is
available as a complement to the standard DC method to
study the magnetic susceptibility of materials directly.
We offer the facility to perform direct susceptibility
measurements in AC magnetic fields from 10-2 to 500Hz.
The magnet is fitted with a separate superconducting
coil for the AC field, providing up to 5 Gauss AC field,
and is driven by the main system electronics. With this
option, the total sensitivity is maintained at up to
10-8
emu in a 1T background field.
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.
Extended Temperature Range
An extension of the standard temperature range to high temperature is available using the oven insert. In normal operation, the system has a continuous temperature range of 1.6 to 370K. With the oven insert this is complemented by allowing measurements in the range 200- 700K.
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.
Transverse Field Saddle Coil
A small transverse field (~ 1 Gauss) may be applied using an optional saddle coil mounted around the main superconducting magnet. The saddle winding is energised using an independent power supply. A persistent mode switch is an optional feature. The transverse field option is offered for use with the transverse pick-up coil sets.
Fluxgate Field Measurement System
For some
applications it is very important to verify the magnet
field at very low applied fields. The fluxgate option
allows field measurements within the sample column up to
a limit of 20 Gauss with a resolution of 10-5
Gauss.
Hall Probe Field Measurement
To
compliment the fluxgate option, Cryogenic offers the
Hall probe facility to enable measurement of magnetic
field in the range 0.1 Gauss to 105
Gauss.
Oscillating Mode
The software allows magnetic measurements by a continuous oscillating mode moving the sample 2mm to 5mm peak to peak. The signal is detected synchronously and the moment displayed. This method permits measurements to be made without the need to stabilise the background field.
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