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BackgroundThere are no commercially available channel electron multipliers (CEMs) made of glass in domestic market of China; more complex CEMs with helix channels are scarcer.PurposeThis study aims to develop a CEM with a single helix channel, and test its performace for satisfying the requirements of high-end users of such products.MethodsFirst of all, a series of manufacturing process designs and improvements were made on the basis of the formula of microchannel sheet glass, resulting in the production of a single spiral channel electron multiplier with suitable performance. Then, a CEM analog mode test device with a disc-incense type tantalum filament as the input current and a CEM pulse-counting mode test device with an ultraviolet light-emitting diode combined with a gold cathode as the input signal were set up to conduct comprehensive testing of the device's performance parameters.ResultsThe newly developed CEM with single helix channel achieves gains of 1×104~1×106 in the analog mode and 1×107~1×108 in the pulse-counting mode. The gain value increases with the increase of the working voltage, and the rise time of the output pulse is 2~3 ns.ConclusionsThe overall performance of the developed CEM is close to that of foreign counterparts, and the CEM can be used in related instruments.

Carbon nanotube (CNT)-based field emission X-ray source with the advantage of fast start-up response offers the chance to achieve high-frequency X-ray emission. In this study, a high-frequency random pulse X-ray source of CNT cold cathode combined with a channel electron multiplier (CEM) was built, and its direct current (DC) and pulse emission characteristics were tested. The DC measurement results were used for parameter selection for performing pulse experiments. During the DC test, with the conditions of 2.2 kV CEM bias voltage and 25 kV anode voltage, the anode currents are 141, 250, and 300 μA at grid voltages of 290, 387.6, and 432.2 V, respectively; the corresponding grid field values are 1.45, 1.94, and 2.16 V/μm. During the pulse test, the amplitude–frequency response of the X-ray source reaches 3.58 MHz at 3 dB. The developed pulse X-ray source was introduced into the X-ray communication (XCOM), and the experimental communication rate reached 6 Mbps with the bit-error-rate of 1.1 × 10−3. The developed high-frequency pulse CNT-CEM X-ray source has potential applications in XCOM, high-speed X-ray imaging, and other fields. • Proposed a high-frequency pulse CNT X-ray source combined with channel electron multiplier at low grid voltage. • Direct current and pulse emission characteristics were tested, respectively. • Frequency response of the CNT-CEM X-ray source is 3.58 MHz at 3 dB. • Communication rate reaches up to 6 Mbps with the bit-error-rate of 1.1 × 10−3. [ABSTRACT FROM AUTHOR]

The IBEX Background Monitor (IBaM) provides a small and lightweight method for independently measuring IBEX’s high-energy proton background by integrating the flux of >∼14 keV protons over a ∼7° conical FOV. The IBaM is part of the IBEX-Hi sensor and has a co-aligned look direction. This paper describes the principle of the IBaM and details its design and responses. In particular, we show the response of major components to both ions and ultraviolet (UV) light background. We also provide the geometric factor and calculate expected count rates. [ABSTRACT FROM AUTHOR]

An electron detector containing channel electron multipliers was built and tested in the range of low-voltage scanning electron microscopy as a detector of topographic contrast. The detector can detect backscattered electrons or the sum of backscattered electrons and secondary electrons, with different amount of secondary electrons. As a backscattered electron detector it collects backscattered electrons emitted in a specific range of take-off angles and in a large range of azimuth angles enabling to obtain large solid collection angle and high collection efficiency. Two arrangements with different channel electron multipliers were studied theoretically with the use of the Monte Carlo method and one of them was built and tested experimentally. To shorten breaks in operation, a vacuum box preventing channel electron multipliers from an exposure to air during specimen exchanges was built and placed in the microscope chamber. The box is opened during microscope observations and is moved to the side of the scanning electron microscope chamber and closed during air admission and evacuation cycles enabling storing channel electron multipliers under vacuum for the whole time. Experimental tests of the detector included assessment of the type of detected electrons (secondary or backscattered), checking the tilt contrast, imaging the spatial collection efficiency, measuring the noise coefficient and recording images of different specimens. [ABSTRACT FROM AUTHOR]

The channel electron multiplier (CEM) current flicker noise was examined for different parameters of its operation. In particular, the dependence of CEM power spectral density function on its output current value has been verified. Also the dependence of the CEM power spectral density function on the input electron energy was investigated. [Copyright &y& Elsevier]

We have investigated channeltron operating in coincidence with silicon surface barrier detector for detection of extreme low energy particles. By use of Po-209 radionuclide and silver backing, a radioactive source was prepared as a fine emitter of released α particles, conversion electrons, recoil Pb-205 ions and knock out silver ions. To avoid parasite coincidence events mainly from channeltron anode RC circuit, we have applied appropriate Faraday screens. After getting proper counting rates, composite spectra were recorded. Based on time-of-flight and secondary electron emission coefficient arguments, particular spectra of mentioned particles were extracted. Final experimental data analysis enabled us to found channeltron efficiency curves for electrons, lead ions and silver ions with low detection thresholds at 40 eV, 4 keV and 1.7 keV, respectively. [Copyright &y& Elsevier]

A compact mono-energetic positron beam system has been constructed at The University of Hong Kong in order to perform positron re-emission measurements, after fast positrons from a radioactive 22Na source moderated by a variety of samples. The positron re-emission measurements are performed at a vacuum of 10−8 Torr. Re-emitted slow positrons are guided by longitudinal magnetic fields provided by three field coils located outside the vacuum tank and are detected by a gamma photon insensitive channel electron multiplier (CEM). The radioactive source, the sample, the focusing grid, the retarding-field energy analyzer (RFA) and the CEM detector were put into a compact assembly having a length of 33 cm and a diameter of 6 cm. Positron re-emission from W(1 1 1), GaN/SiC, Ga/GaN/SiC, 4H and 6H–SiC surfaces have been studied. The moderator conversion efficiencies of these samples are reported. [Copyright &y& Elsevier]