Superconducting nano-stripline detectors (SSLDs) are promising for realizing ideal ion detection in mass spectrometry. We have investigated the ion detection efficiency of a niobium nitride (NbN) SSLD, measuring the bias current dependence of the detection efficiency for Ar þ , Ar 2þ , and Ar 3þ ions accelerated by static voltages between 0.5 and 3 kV. The bias current dependence exhibited a distinct plateau in a high bias region and an abrupt reduction at a certain bias current (threshold bias current) that decreased with increasing kinetic energy. It was found that the kinetic energy dependence of the threshold bias current is consistent with a hot-spot model. #

Fluorescence-yield X-ray absorption fine structure (FY-XAFS) is extensively used for investigating atomic-scale local structures around specific elements in functional materials. However, conventional FY-XAFS instruments frequently cannot cover trace light elements, for example dopants in wide gap semiconductors, because of insufficient energy resolution of semiconductor X-ray detectors. Here we introduce a superconducting XAFS (SC-XAFS) apparatus to measure X-ray absorption near-edge structure (XANES) of n-type dopant N atoms (4 ×1019 cm−3) implanted at 500°C into 4H-SiC substrates annealed subsequently. The XANES spectra and ab initio multiple scattering calculations indicate that the N atoms almost completely substitute for the C sites, associated with a possible existence of local CN regions, in the as-implanted state. This is a reason why hot implantation is necessary for dopant activation in ion implantation. The SC-XAFS apparatus may play an important role in improving doping processes for energy-saving wide-gap semiconductors and other functional materials.

We propose a prime factorizer operated in a frame work of quantum annealing (QA). The idea is inverse operation of a multiplier implemented with QA-based Boolean logic circuits. We designed the QA machine on an application-specific-annealing-computing architecture which efficiently increases available hardware budgets at the cost of restricted functionality. The invertible operation of QA logic gates consisting of superconducting flux qubits was confirmed by circuit simulation with classical noise sources. The circuits were implemented and fabricated by using superconducting integrated circuit technologies with Nb/AlO x /Nb Josephson junctions. We also propose a 2.5-dimensional packaging scheme of a qubit-chip / interposer / package-substrate structure for realizing practically large-scale QA systems.

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Mass spectrometry (MS) is a method of analyzing ions based on their mass/charge (m/z) ratios. The m/z peak identification requires speculation on the ionic charge states. This problem can be solved by using superconducting junction devices to measure the kinetic energies of single molecules. However, the kinetic energy measurement is followed by the dead time of 1-20 ms, which is fatally slow for modern high-resolution time-of-flight (TOF) analyzers. In this paper, we demonstrate that a superconducting nano-stripline detector (SSLD) composed of a 10-nm-thick and 800-nm-wide NbN strip realizes the charge-state derivation, and furthermore satisfies the ideal MS detector specifications such as a nano-second response, a short recovery time, a wide mass range, and no noise. Copyright # 2010 John Wiley & Sons, Ltd.In mass spectrometry (MS), ionized analytes are accelerated by a static voltage (V ¼ 3-30 kV), acquiring a kinetic energy of zeV, where e is the elementary charge and z is the unit-charge number. The ions are separated either spatially or temporally, and are detected by an ion (particle) detector. The spatial or temporal separation by an electromagnetic force leads to the same result for any ion species having the same mass/charge (m/z) ratio. Therefore, it is impossible to distinguish between different ion species with the same m/z.One type of the modern MS analyzers is based on time-offlight (TOF) spectroscopy, which measures time lags between the acceleration and detection after field-free flight for a certain distance (l). The relationship between TOF and m/z is expressed as TOF ¼ (m/z2eV) 1/2 l. Detectors in the ion counting mode generate an electric pulse, enabling the measurement of each instance of ion arrival. Some specifications for an ideal MS detector are listed in Koppenaal et al., 1 although the charge-state derivation is unlisted because it is essentially impossible by using conventional MS instruments. Satisfying these specifications as well as determining the charge states is a challenging task.Widely used ion detectors such as microchannel plates (MCPs) or secondary electron multipliers (SEMs) have a nano-second ion-counting capability necessary for a resolving power (m/Dm) over 10 000, and a cm size covering the molecular beam. The keV molecular ions induce soft impact and stop on the detector surface.2 Under this soft impact, the ion detection must rely on the emission of one or a few secondary electrons, in contrast to the generation of millions of charge carriers in kinetic-energy-sensitive semiconductor detectors used in nuclear physics. In a mass range over 4000, the quantum efficiency of the secondary electron emission is less than unity when singly charged ions are accelerated at 20 kV, and this efficiency decreases as molecular weight (MW) increases. 3,4 At this low number of secondary electrons, MCPs and SEMs cannot distinguish between every charge state, although rough discrimination between ions with 10þ (e.g., 200 keV) and 50þ (e.g., 1 MeV) is possible by analyzing the pulse he...