Eddy current evaluation of airframes using refrigerated SQUIDs

Author

Podney, W.N.

Author_Institution

SQM Technol. Inc., La Jolla, CA, USA

Volume

5

Issue

2

fYear

1995

fDate

6/1/1995 12:00:00 AM

Firstpage

2490

Lastpage

2492

Abstract

A superconductive quantum interference device, RF SQUID, fixed to the cold pad of a Heliplex HS-4 refrigerator shows a baseline noise of 1.6/spl times/10/sup -4/ flux quanta in a one hertz bandwidth at frequencies above about 25 Hz. The refrigerator adds noise below 25 Hz. Remote pickup loops couple flux to the SQUID through a cryogenic umbilical, 500 mm long, attached to the cold pad. It enables scanning a 100/spl times/100 millimeter section of airframe without moving the expander, which connects to compressors through flexible gas lines 3 m long. Thermal conduction through copper braiding in the umbilical keeps pickup loops at 5.5 K, 3 mm from an airframe at ambient temperature. Drive currents of a few amperes, oscillating at one to three hundred Hertz enable identifying 5 to 10 percent material loss through 10 to 15 mm of aluminium.<>

Keywords

SQUID magnetometers; SQUIDs; aircraft testing; eddy current testing; refrigeration; 25 Hz; 5.5 K; Heliplex HS-4 refrigerator; airframes; baseline noise; eddy current evaluation; flexible gas lines; refrigerated SQUIDs; remote pickup loops; superconductive quantum interference device; thermal conduction; Bandwidth; Compressors; Cryogenics; Eddy currents; Radio frequency; Radiofrequency interference; Refrigeration; SQUIDs; Superconducting device noise; Superconductivity;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/77.403096

Filename

403096