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Ultrasensitive broadband electrical measurement instruments utilising superconducting quantum interference devices


The objectives of this project are to develop ultra-low noise, wide bandwidth SQUID amplifiers to demonstrate their utility by incorporating them into five different demonstrator instruments and two practical measurement applications. SQUIDs based on low temperature superconductors (LTS) and high temperature superconductors (HTS) will serve as the key elements in these systems. Instrumentation will be developed around the SQUIDs to ensure practical measurements of electric quantities. The performance and limits of these demonstrators will be evaluated and compared to conventional technologies, e.g. semiconductors.

State of progress
The programme is currently running in its final year. Several deliverables have been completed, partly well exceeding the specifications given in their Work Package description. The LTS picovoltmeter reached a bandwidth of 12 MHz (target was 5 MHz); the LTS noise thermometer was proved to work down to well below 280 mK (target range was 1-4 K); the related work packages have been completed. The HTS picovoltmeter has been used for transient measurements, currently the performance is optimised by the use of integrated input coils in the HTS SQUIDs. The HTS noise thermometer system has been experimentally proven to work qualitatively, currently the resistive SQUIDs as well as the readout SQUIDs are being optimised. SQUID NMR measurements have been successfully demonstrated with the completed NMR amplifier. All project partners are determined to work together in close and constructive scientific collaboration to finish the programme successfully on time.

Superconducting Quantum Interference Devices (SQUIDs) are the most sensitive sensors for magnetic flux. By variation of the input circuitry to the SQUIDs, they can be used for electrical measurements, where resolutions down to 10-12 V and 10-14 A have been achieved in laboratory environment. In this configuration, SQUIDs can be seen as a basic device, similar to the transistor, to be incorporated in amplifiers and systems with noise levels impossible to achieve with any other technology.
The programme is divided into the development of:
* SQUID amplifiers for LTS and HTS SQUIDs as a base for the programme,
* picovoltmeters, incorporating LTS and HTS SQUIDs,
* noise thermometers, incorporating LTS and HTS SQUIDs and
* a nuclear magnetic resonance (NMR) amplifier, based on LTS SQUIDs.
Successful completion will be shown by demonstrators used for electrical measurements. The HTS picovoltmeter will be used as a transient detector from high-voltage components, the NMR amplifier will be integrated in an instrument for practical NMR measurements. All demonstrators will be developed and built in close collaboration by the different project partners.

Funding Scheme

CSC - Cost-sharing contracts


Oxford Instruments plc
Cowley Road
CB4 4WZ Cambridge
United Kingdom

Participants (5)

Asea Brown Boveri AB
2,Gideonsbergsgatan 2
721 78 Västeras
Bundesrepublik Deutschland
100,Bundesallee 100
38116 Braunschweig
Chalmers University of Technology AB
1,Kemigarden 1
412 96 Göteborg
11,Priorparken 878
2605 Brondby
National Physical Laboratory (NPL)
United Kingdom
Queen's Road
TW11 0LW Teddington