Superconducting NbN microstrip detectors

Abstract

SummarySuperconducting NbN strip transmission line counters and coupling circuits were processed on silicon wafers using thin film techniques, and they were characterized with several methods to verify the design principles. The stripline circuits, designed using microwave design rules, were simulated using a circuit design tool enhanced to include modelling of the superconducting lines. The strips, etched out of the 282 nm thick top NbN film with resistivity 284 µΩcm at 20 K, have critical temperatures in the range 12 to 13 K and a critical current density approximately J c (0) = 3.3·10 5 A/cm 2 . The linearized heat transfer coefficient between the strip and the substrate is approximately 1.1·10 5 W/(m 2 K) and the healing length is about 1.6 µm between 3 and 5 K temperatures. Traversing 5 MeV α-particles caused the strips to quench. No events due to electrons could be detected in agreement with the predicted signal amplitude which is below the noise threshold of our wideband circuitry. The strip bias current and hence the signal amplitude were limited due to a microbridge at the isolator step of the impedance transformer.

Hybrid superconducting neutron detectors

“…Wedenig et al [9] observed voltage pulse rise-times of the order of 250 ns and amplitudes of 10 mV in NbN, thus confirming the working principle of the detector. The idea herein presented is to use a boron converting layer to coat a superconducting strip.…”

“…Further studies on Sn and In strips [7,8] confirmed the bolometric nature of the process. More recently, Wedenig et al [9] have observed voltage pulses in NbN strips irradiated with  particles from a 241 Am source (E  = 5.5 MeV). The detection scheme, involving the creation of a hot-spot in superconducting strips, has also been explored in the context of x-ray and -ray detection, as discussed in Refs.…”

Electromagnetic models for multilayer superconducting transmission lines

“…Before evaluating equation (9), it is important to note that each half plane of CPW contains a half of total power flow, a half of ground plane loss, and a single unit of upper or lower strip loss. The denominator of ψ can be calculated in the z p -plane, and is given by…”

“…High quality superconducting lines have also been incorporated in electron spin resonance (ESR) systems to drive and detect spin resonance [5], and to achieve quantum limited sensitivity in ESR spectroscopy [6]. In the field of detector physics, applications include travelling wave parametric amplifiers [7], tunnel junction detectors [8], particle detectors in accelerators [9], and kinetic inductance detectors (KIDs) for astronomy observations [10], neutrino decay identifications [11], and dark matter searches [12].…”

Superconducting Strips: A Concept in Thermal Neutron Detection

“…A proper understanding of all details of the heat pulse propagation (related to pulse rise-time) is beyond the scope of the present work, but essentially the behaviour of these transient phenomena is explained in terms of equilibrium or non-equilibrium models depending on the relative coupling between electron and phonon populations of the superconducting material [19,20]. An interesting and extensive discussion of the two approaches related to the operation of superconducting strip particle detectors can be found in [21], where the situation is described in some detail and estimates are made of the various time scales involved. For quite recent work on this subject, see also [22].…”