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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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