All.H'rnet-We report on the performam:� of de SQlll) (Supcrcond urting QUlelltum Tn terference Devi�c) scric:". array amplifiers from de to 500 j\Ulz. The arrays (.on�i8t of up 10 100 de SQUIDs, with �'llryin� dej:!n'es of tn1rafoil dampinp;: tile Onx focusing wal;llcr of each SQUID is electrically isolaterl from the SQUI n II)0p (L,q = 1 R pH). Using .liD rf network aD�lyzt'r, .... . e h!lv� obscn'ed high-frclJ Ul;m��y resonances in thc response flt bill!! points correspondin� to distortions in the de tmnsfu functions. III�rcasillg distancc hctwi:en SQUIDs in the array reduces th.., disturtiuns. Dislur( io ns are a 1m m o roll r rorwunced, It II rI bandwidrh reduced, in de1--'ices jncorporating th .. n1l1-fOtu�ing washer il110 the SQUID bod,·. With intrlicoil dnmping of 0.25 Q per tnrn 00 the input coil, th� volt�ge-flux transfcr characteris tics of the isolated-washer design and 300 ILm , center-to-centu SQIHD spacing arc frce of �ignificant distortions, and the bllndwillth is not degraded COm]):1red to und am ped dcvirc�. The 1 OO-SQ U m array has 150 11 rr in put inductaDce, 500 Y 1_-\ tr� n�imped;1 n��e, l.� [lAf .... . Hz eq uivalcnt ill pllt currcnt noi�c at 4 K, and 120 :\fHz bandwidth.Tna{!x 7'1',.m. _Resnllancc�_ SQU lOs, SQUID series n rrays, ;s Li percond II cting de \'ic e�.· . 1i\TRODUCTIOXA number of detector technologies demand amplifiers or high �ellsitivity, low impedance, and high b,mdwid,h.These wchnologies includ<; m icrocnlorimetric x-ray detectors r 11. infraredisub-mrn imaging detectors [or a�tron()lI1y t2 J, cerrail1 NMR applications [31, [4], cryogenic dark-lTIi1tter delectors [jl, and antennae applicatio,ls [6]; in particular, electrically small antennae require high-frequency (�2 Gllz) low-nu i�e amp Ii fiers. The de supereondllcting q II antI! n1 interference device (SQUID) is arguably the most sensitive detector for magnctic tl e1d�, with sensitivity approaching the quantum lim it [7}. If high-efficiency inductive coupling coils artl used, dc SQl:TDs becomc extremely scnsitive to electric .:urrents. Their intrinsic bandwidth is dc to milny GHz., and their input impedance in the above configuration is low and effectively indw.:: tivc. Thu,;, de SQUIO., have heen seriously

We report on the performance of dc SQUID (Superconducting Quantum Interference Device) series array amplifiers from dc to 500 MHz. The arrays consist of up to 100 dc SQUIDs, with varying degrees of intracoil damping; the fluxfocusing washer of each SQUID is electrically isolated from the SQUID loop (Lqq = 18 pH). Using an rf network analyzer, we have observed high-frequency resonances in the response at bias points corresponding to distortions in the dc transfer functions. Increasing distance between SQUIDs in the array reduces the distortions. Distortions are also more pronounced, and bandwidth reduced, in devices incorporating the flux-focusing washer into the SQUID body. With intracoil damping of 0.25 0 per turn on the input coil, the voltage-flux transfer characteristics of the isolated-washer design and 300 pm center-to-center SQUID spacing are free of significant distortions, and the bandwidth is not degraded compared to undamped devices. The 100-SQUID array has 150 nH input inductance, 500 V/A transimpedance, 2.5 pA/ Hz equivalent input current noise at 4 K, and 120 MHz bandwidth.

No abstract

No abstract

No abstract