Model VCblue is a low-TC dc SQUID current sensor with low input inductance and moderate current sensitivity. It is designed as an amplifier SQUID in double-SQUID systems suitable for readout signals form separate SQUIDs placed at extremely low temperatures or from SQUIDs in multiplexing schemes.

The Model VCblue integrates an input coil, a feedback coil, and a heater on the chip. The adaptation of the number of turns in the input coil allows a perfect matching of the first stage SQUID.

For mechanical protection and easy handling the SQUID Model VCblue is placed inside a glass fiber package and magnetically shielded by niobium screen. It has four pairs of solder terminals with metal wire bond connections to the chip: one is for the SQUID output, one for the feedback coil, one for input coil, and one for the heater resistor. This resistor allows easy expelling of frozen flux in the SQUID loop.  

SQUID model VCblue parameters
Size of superconductive screen in mm	24×ø10
Working temperature in K	<5
SQUID-Inductance LS in pH	~50
mutual inductance Feedback coil–SQUID MFB in pH	140
Feedback coupling 1/MFB in µA/Ф	14.5
mutual inductance Feedback–input coil MFB-IN in pH	<1
White noise (typical)in µФ0/Hz1/2	<2.5

Optional input coil parameters
VCblue-Nr.	VC1	VC2	VC3	VC4	VC5	VC6
Lin in nH	4.5	3.3	2.0	1.1	1.2	0.9
Minin pH	380	310	240	170	150	130
Coupling in µA/Ф0	5.5	6.3	8.7	12	13.5	16