Tc/Jc measurement system

Umberto (update October 2018)

COMPONENTS

Cryostat and Compressor:

Sumitomo RDK-101D cold head (two stages) and CNA11C helium compressor.

First Stage: 36 K

Second Stage: 2.1 K

On the 40 K stage:

1 DT-670 Silicon diode temperature sensor in a gold-plated copper bobbin uncalibrated

On the 4 K Stage:

Gold support with 32 pogo pins (0933-0-15-20-75-14-11-0 - SPRING LOADED PIN, 2A) installed in an insulant material

Gold support with 8 slots for 15x15mm

Samples are connected to the pins by contact

1 DT-670 Silicon diode temperature sensor in a gold-plated copper bobbin calibrated 1.4 K to 325 K.

On top of the sample holder:

1 DT-670 Silicon diode temperature sensor in a gold-plated copper bobbin calibrated 1.4 K to 325 K.

1 THS resistor 1kOhm (heater function)

Wiring:

The pogo pins are connected to a 12-way receptacle with pins - hermetic connector (CMR-DIRECT) by 2-pair Constantan wires

The Si Diode sensors are connected to a 12-way receptacle with pins - hermetic connector

The wires are attached at the arm of the cryostat in a spiral way by a polyimide tape to reduce thermal effects.

Shields:

Mu-metal installed on the 4 K stage to protect samples by electric interference (IT NEEDS TO BE CHANGED)

Thermal shield (gold)

Vacuum shield (aluminium)

Electrical Setup:

4-probe method:

- two probes are connected to a voltage source (with a resistor in series) through a relay

- two probes are connected to a voltmeter to measure the voltage of the samples.

The electrical setup is composed of 8 INPUT RELAYS (GEN8PRMx-EasyDaq) and it communicates to PC by a Labjack U6

The electrical setup is installed in a metallic box

Instrument:

SRS SIM900 Mainframe (8 Slots)

Slot 1 - SIM922A Diode Temperature Monitor

Slot 2 - SIM928 Isolated Voltage Source

Slot 3/4 - SIM970 Quad Digital Voltmeter

Slot 5/6 - SIM970 Quad Digital Voltmeter

Slot 7/8 - SIM960 Analog PID Controller

P200 Voltage Amplifier (x10) connected to the heater (THS 1kOhm) to heat the cryostat at different temperature

2 Keithley 2000 Multimeters

Software:

The system is controlled by programs written in Python Code (compatible in Python 2.x):

- RT program

This program record the signals of the voltage VL across the load resistor R by the Keithley 2000, the voltage measured by voltmeters SIM970 and the temperature measured by controller SIM922A. The resistance is then computed by the relation:

R = V*R/VL

- IV program

This program bias the sample by a periodic current bias and record the signals of the voltmeters to plot the IV characteristic of the sample

Sheet Resistance

Reference:https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6773368

R = C*(V/I)

C is a geometric correction factor. It depends on the dimensions of the sample and the distance of probes.

Square sample (a/d = 1)

d = 15mm

s = distance of probes = 2.7mm

C = 3.5

2104 - 2017

Based around SHI RDK101D cold head and CNA11C compressor.

Two Stages(1st 40K and 2nd 4K)

3 Lakeshore DT670 Si diode sensors

Space for 8 1.5cm x 1.5cm samples

Each space is contacted with 4 pogo pins (0933-0-15-20-75-14-11-0 - SPRING LOADED PIN, 2A)

Isolated voltage source (SRS SIM unit), LabJack switch, SRS SIM Voltmeter readout.

DAQ via laptop PC (Python)

10/2016 - upgrade to low T I-V measurement

07/2017 - added heater 1000 ohm controlled by PID (SRS SIM unit).