Asymmetric response of superconducting niobium-tunnel-junction x-ray detectors

Ohkubo, M.; Martin, J.; Drachsler, K.; Gross, Rudolf; Huebener, R. P.; Sakamoto, Isao; Hayashi, Naoaki

doi:10.1103/physrevb.54.9484

Cited by 15 publications

(6 citation statements)

References 45 publications

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“…6 The base and counterelectrodes of another junction on the same wafer were separately stimulated by short electron beam pulses, and the decay times of the junction response were measured at a bias voltage of 1.3 mV and at 2.1 K. The details of LTSEM can be found in other publications. 7,8 The decay time constants were 0.21 and 0.15 s for the base and counterelectrodes, respectively. On the other hand, in the scatter plots of the signal heights against the charge sensitive preamplifier rise times, the x-ray events were classified into two groups having mean rise times ͑20%-80%͒ of 0.15 and 0.11 s. 6 When we take a qp loss time and a tunneling time, which are described in Sec.…”

Section: Resultsmentioning

confidence: 99%

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Double peak phenomenon in superconducting tunnel junction x-ray detectors

Ohkubo¹,

Fukuda²,

Sakamoto³

et al. 1999

Journal of Applied Physics

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Tunneling of nonequilibrium quasiparticles excited by x-ray quanta in a nonsymmetric superconducting tunnel detector Low Temp.It has been normally observed that superconducting tunnel junction x-ray detectors produce a double peak originating from different absorption events in two electrodes. The double peak is associated with the dynamics of quasiparticles created by x-ray absorption events. In this study we have found that the double peak phenomenon depends on both bias voltage and magnetic history. On the events in the base and counterelectrodes the detector exhibits dissimilar signal-height versus bias-voltage characteristics, which suffer a large change when a small number of Abrikosov vortices corresponding to even a terrestrial magnetic field are frozen during cooling. These observations are explained by a multiple quasiparticle tunneling model with quasiparticle trapping in the vortices.

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Section: Resultsmentioning

confidence: 99%

“…In fact, the countersignal of the present junction is much larger than that of a junction with no Al cap layer. 7 Nevertheless, it is possible that the contamination prevention was not perfect.…”

Section: A Multiple Quasiparticle Tunneling Modelmentioning

confidence: 99%

Double peak phenomenon in superconducting tunnel junction x-ray detectors

Ohkubo¹,

Fukuda²,

Sakamoto³

et al. 1999

Journal of Applied Physics

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“…Nevertheless, in a low energy range of less than 2 keV, our STJ detectors exhibit a linear relation between deposited energy and output pulse height, and therefore are applicable to soft X-ray spectrometry or low energy particle detection. For practical use, the surface of the top Nb electrode is bare so that soft X-ray photons, atoms, and molecules impinge on the Nb surface directly, although the Nb surface exposed in air may be contaminated by oxidization and the detector response is slightly degraded [19]. STJ detectors use 2Δ as a scale for measuring the energy deposited upon a single-photon absorption event or a singleparticle surface impact event.…”

Section: Operating Principle Of Stj Detectorsmentioning

confidence: 99%

Superconducting Tunnel Junction Detectors for Analytical Sciences

Ohkubo

Shiki²,

Ukibe³

et al. 2014

IEEE Trans. Appl. Supercond.

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Superconducting tunnel junction (STJ) detectors exhibit superior detection performance for photons and particles at a high spectroscopic resolution of ∼10 eV, a short dead-time (decay time) of ∼μs, a high quantum efficiency of ∼100%, and a low detection threshold energy of less than 1 eV, which cannot be achieved by conventional detectors. The outstanding detection performance originates from a small superconducting energy gap of ∼meV, which is three orders of magnitude smaller than ∼eV in semiconductors. This paper reports our recent progress in two applications of STJ detectors to fluorescence-yield X-ray absorption fine structure (XAFS) spectrometry for trace light elements in matrices and mass spectrometry (MS) for ions with the same mass/charge-number ratio (m/z) but different charge states and neutral fragments.Index Terms-Mass spectroscopy (MS), superconducting devices, superconducting tunnel junction (STJ), X-ray absorption fine structure (XAFS), X-ray detection. I. INTRODUCTIONS UPERCONDUCTING tunnel junction (STJ) detectors have a sandwich structure of superconductor-insulatorsuperconductor with an insulator thickness of ∼1 nm. The device structure is the same as that of Josephson junctions. For detecting photons or particles, the STJ detectors are operated in the so-called Giaever mode [1], in which the dc Josephson effect is suppressed by applying a small magnetic field of 10-100 G so that the change of quasiparticle tunnel current can be measured. The junctions are biased within the sub-gap region to observe the change of quasiparticle tunnel current.

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“…This results in the difficulty of observing the signals from two electrodes separately, except for measurements at junction edges, time-resolved measurements, and dependence on the electron energy. 7 Furthermore, at a LT-SEM base temperature of 1.6-2 K, the electron beam perturbation can be small, in other words, the number of the electron-beam induced quasiparticles could be smaller than that of the thermally excited quasiparticles. The situation in the real detector operation is opposite.…”

Section: ͓S0003-6951͑00͒01650-8͔mentioning

confidence: 99%

Experimental imaging diagnosis of superconducting tunnel junction x-ray detectors by low-temperature scanning synchrotron microscope

Preßler¹,

Ohkubo²,

Koike³

et al. 2000

Applied Physics Letters

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Imaging diagnosis of superconducting tunnel junction x-ray detectors has been performed by an apparatus called the low-temperature scanning synchrotron microscope (LTSSM) using an x-ray microbeam with a diameter of 5–10 μm originated from synchrotron radiation. Quasiparallel intense synchrotron radiation enables one to obtain the full two-dimensional images of junctions with dimensions of 200×200 μm2 in about 1 h. The LTSSM results indicate that the standard quasiparticle diffusion and edge loss model for the spatial distribution of the junction response to x rays is evidently inadequate for intermediate or large junctions (with respect to a Josephson penetration depth). On this basis, it is argued that the models proposed for the signal creation and loss mechanism should be reconsidered.

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Asymmetric response of superconducting niobium-tunnel-junction x-ray detectors

Cited by 15 publications

References 45 publications

Double peak phenomenon in superconducting tunnel junction x-ray detectors

Double peak phenomenon in superconducting tunnel junction x-ray detectors

Superconducting Tunnel Junction Detectors for Analytical Sciences

Experimental imaging diagnosis of superconducting tunnel junction x-ray detectors by low-temperature scanning synchrotron microscope

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