Single-layer and integrated YBCO gradiometer coupled SQUIDs

Abstract

For many SQUID applications such as biomagnetism or non-destructive evaluation it is convenient or even necessary to work without the restrictions of a magnetically shielded room. This contribution deals with two sensors appropriate for this purpose.In the first concept we present a flip chip arrangement of a single-layer flux transformer and a single-layer SQUID, taking advantage of a simple technology. The SQUID was prepared on a 15 × 15 mm 2 SrTiO 3 24 • bicrystal and located in the common line of two-parallel-loop arrangements. The flipped antenna was designed as a two-parallel-loop gradiometer with 26 mm baseline on a 10 × 40 mm 2 LaAlO 3 single-crystal substrate. A field gradient sensitivity of 1 nT cm −1 0 was obtained. We could demonstrate a field gradient resolution of 20 fT cm −1 Hz 1/2 at 1 kHz in an unshielded environment.In the second concept we integrated both the flux antenna and the SQUID on a SrTiO 3 bicrystal. The tighter coupling scheme results in smaller devices for similar field gradient sensitivities. The integrated SQUID is designed as a 3 × 8 mm 2 device on a 10 × 10 mm 2 bicrystal substrate. The remaining space is used for test structures and SQUIDs without antennae, in order to control the technology as well as the SQUID design. Parallel processed dummy substrates were used to monitor the quality of film growth by x-ray analysis. The quality of our SQUID design will be discussed on the basis of the measured field gradient sensitivity and noise. The reliability of the devices is demonstrated by an NDE type measurement.

A high-Tcflip-chip SQUID gradiometer for mobile underwater magnetic sensing

“…Peiselt et al [12], after investigating different coupling loops, achieved an overall optimized sensitivity of 12 fT cm −1 Hz −1/2 (white) and 310 fT cm −1 Hz −1/2 at 1 Hz in an unshielded environment. Other flip-chip gradiometer designs have been fabricated by Dantsker et al [13] and Bär et al [14] who demonstrated a gradient sensitivity of 20 fT cm −1 Hz −1/2 at 1 kHz (unshielded). However, this flip-chip design has some advantages over conventional flipchip arrangements (generally inductive coupling to a small dc washer SQUID).…”

A signal-to-noise chart for designing planar high-TcSQUID gradiometers for magnetocardiographs

“…Many planar-type high-T c SQUID gradiometers have been previously reported [4][5][6][7][8][9][10][11][12][13][14][15][16]. The gradient field noise and baseline lengths, which are given in these references, have been collected (figure 2).…”

“…Many planar-type high-T c SQUID gradiometers have recently been developed [4][5][6][7][8][9][10][11][12][13][14][15][16], because they can be operated in liquid nitrogen without adjustments of gradiometric balance. However, their feasibility for detecting P-waves has not been sufficiently evaluated.…”

High-Tc dc-SQUID gradiometers in flip-chip configuration

“…An incoupling antenna with large area on a single crystalline substrate inductively coupled to a read-out sensor on a bicrystal substrate in available size (flip-chip gradiometer or magnetometer) [2] offers a solution. Different groups already realized this concept [3][4][5]. In this paper we are going to discuss a new layout version following this concept.…”