National SQUID Facility

IIT Delhi


Location: MS-305 Physics Department, IIT Delhi 110016           Email:         Phone: 26596542


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Basic Literature About SQUID National Facility (Funded by DST)


What is Superconducting Quantum Interface Device (SQUID)?


SQUID magnetometer is one of the most effective and sensitive ways of measuring magnetic properties. In particular, it is the only method which allows to directly determine the overall magnetic moment of a sample in absolute units.


The superconducting quantum interference device (SQUID) consists of two superconductors separated by thin insulating layers to form two parallel Josephson junctions. The device may be configured as a magnetometer to detect incredibly small magnetic fields small enough to measure the magnetic fields in living organisms. Squids have been used to measure the magnetic fields in mouse brains to test whether there might be enough magnetism to attribute their navigational ability to an internal compass.


By Brian David Josephson in 1962, the electrical current density through a weak electric contact between two superconductors depends on the phase difference Δφ of the two superconducting wave functions. Moreover, the time derivative of Δφ is correlated with the voltage across this weak contact. In a superconducting ring with one (so-called rf SQUID) or two (dc SQUID, fig. 1, blue) weak contacts, Δφ is additionally influenced by the magnetic flux Φ through this ring. Therefore, such a structure can be used to convert magnetic flux into an electrical voltage.  This is the basic working principle of a SQUID magnetometer.


When the sample is moved up and down it produces an alternating magnetic flux in the pick-up coil .The magnetic signal of the sample is obtained via a Superconducting pick-up coil with 4 windings (fig. 3). This coil is, together with a SQUID antenna (red in fig. 1), part of a whole superconducting circuit transferring the magnetic flux from the sample to an rf SQUID device which is located away from the sample in the liquid helium bath. This device acts as a magnetic flux-to-voltage converter (blue in fig. 2). This voltage is then amplified and read out by the magnetometer’s electronics (green in fig. 2).


Cryocooler Compressor: The MPMS EverCool system features an integrated cryocooler–Dewar System that recondenses the He directly with in the EverCool Dewar.


Oven: For high temperature measurement    300K -800K 


Sample Rod: This is expensive   >$180, if the rod is bent the straw could be lost in side the Dewar.


UPS: An uninterruptible power supply (UPS), also known as a continuous power supply (CPS) or a battery backup is a device which maintains a continuous supply of electric power to connected equipment by supplying power from a separate source when utility power is not available.

Note: Please note that user must be on time and be ready with the sequence before loading the sample


System Specification:



Field Range

± 7.0 Tesla(70,000 Gauss)

Field Stability


Intrinsic Field Uniformity

(4cm:_2cm from center of pickup coil)

0.01% over 4cm

Field setting resolution


2 G to 70,000 G

0.2 G to 6,000 G

Residual field  (Gauss)

                                     Oscillate Mode

                                    No Overshoot Mode


<5 G typical

<30 G typical

Maximum Calibrated Sample Size(Sample Chamber ID)


RSO Measurement

Differential sensitivity (minimum resolvable change in magnetic moment, 1E-4 EMU range)

<1E-8 EMU to 2,500 Oe

£6E-7 EMU to 7 Tesla (STD. ERROR)

Range of measurement

±5.0 EMU

(option to ± 300 EMU)

Temperature range at the sample space (Kelvin)

1.9 K to 330 K Option to 800 K

Temperature calibration accuracy at the sample space

± 0.5% typical

Temperature stability at the sample space (Kelvin)

± 0.5%

Temperature spatial variation in sample chamber (Kelvin)

±0.1 K over 8cm

±1.0 K over 15cm

@235 K

Rate of temperature change (max.)

300 K to 10 K @ 10 K/min

10 K to 2 K @ 2 K/min

Helium capacity (Liters)


Helium usage* Standard Super Insulated Dewar (Liters/day)

Optional Nitrogen Jacketed Dewar (Liters/day)





Some Useful Links:


Figure 1


Figure 2



Figure 3