Solar-blind Photomultiplier Tube Research Articles

Preparation and properties of solar-blind photomultiplier tube

The photocathode of solar-blind photomultiplier tube is Te-Cs, and the glass tube is synthetic quartz. We use special oven with two lights to prepare solar-blind photomultiplier tube. We test the performance of solar-blind photomultiplier tubes. Results show that CR340 has good solar-blind characteristic, cut-off wavelength at 320 nm, and output sensitivity can reach 5×105 A/W (250 nm), and gain can reach 1.3×107, and life is more than 1000 h. Solar-blind photomultiplier tubes are evaluated by several domestic analytical instruments manufacturers, all feedback are very good.

First Demonstration of a Scintillating Xenon Bubble Chamber for Detecting Dark Matter and Coherent Elastic Neutrino-Nucleus Scattering.

A 30-g xenon bubble chamber, operated at Northwestern University in June and November 2016, has for the first time observed simultaneous bubble nucleation and scintillation by nuclear recoils in a superheated liquid. This chamber is instrumented with a CCD camera for near-IR bubble imaging, a solar-blind photomultiplier tube to detect 175-nm xenon scintillation light, and a piezoelectric acoustic transducer to detect the ultrasonic emission from a growing bubble. The time of nucleation determined from the acoustic signal is used to correlate specific scintillation pulses with bubble-nucleating events. We report on data from this chamber for thermodynamic "Seitz" thresholds from 4.2 to 15.0keV. The observed single- and multiple-bubble rates when exposed to a ^{252}Cf neutron source indicate that, for an 8.3-keV thermodynamic threshold, the minimum nuclear recoil energy required to nucleate a bubble is 19±6 keV (1σ uncertainty). This is consistent with the observed scintillation spectrum for bubble-nucleating events. We see no evidence for bubble nucleation by gamma rays at any of the thresholds studied, setting a 90%C.L. upper limit of 6.3×10^{-7} bubbles per gamma interaction at a 4.2-keV thermodynamic threshold. This indicates stronger gamma discrimination than in CF_{3}I bubble chambers, supporting the hypothesis that scintillation production suppresses bubble nucleation by electron recoils, while nuclear recoils nucleate bubbles as usual. These measurements establish the noble-liquid bubble chamber as a promising new technology for the detection of weakly interacting massive particle dark matter and coherent elastic neutrino-nucleus scattering.

Lyman Alpha Photometer: a far-ultraviolet sensor for the study of hydrogen isotope ratio in the Martian exosphere

The Lyman Alpha Photometer (LAP), developed for flight on the Mars Orbiter Mission (MOM) spacecraft in 2013, is primarily designed to measure deuterium to hydrogen abundance ratio of the Martian exosphere over a 6-month period from a 263 km × 71,358 km elliptical orbit around Mars. A set of ultrapure (99.999%) hydrogen and deuterium gas-filled cells comprising tungsten filaments, a 25 mm diameter collection lens and a solar-blind photomultiplier tube together with an 8 nm bandpass Lyman alpha filter are the principal electro-optical assemblies of the instrument. This article presents scientific objectives of LAP and its performance specifications along with details of instrument design. The ground characterization techniques to assess LAP operational performance are also presented. End-to-end test results and evaluation matrix of LAP were satisfactory, well within the desired specifications. The first LAP onboard operation was carried out during the cruise phase of MOM spacecraft journey to verify its functionality and all recorded on-board health parameters were satisfactory.

Silver doped lithium tetraborate (Li2B4O7) single crystals as efficient dosimeter material with sub-micro-Gy sensitivity

Single crystals of Li2B4O7 (LTB) with varying Ag content were grown using the Czochralski technique and studied for their optical absorption, photo-luminescence (PL) and thermally stimulated luminescence (TSL) properties. The optimum Ag concentration in the LTB was found to be about 500ppm for the best TSL properties. A TSL readout set-up has been described that uses a solar blind photo-multiplier tube (PMT) to match the emission from Ag which is in the UV region (peak at 270nm). This has significantly improved the performance of the TSL set-up by lowering dark counts and enhancing the signal due to a better matching between the emission from Ag ions and PMT response. In addition, the use of the solar blind PMT also minimized the thermal noise generated from heating of sample in the TSL set-up. Radiation doses lower than 5μGy could be measured using this set-up with small LTB:Ag crystal samples (100mg). The lower detection limit has been estimated to be 500nGy.

Shaper-assisted ultraviolet cross correlator

We successfully demonstrate the characterization of phase- and amplitude-modulated broadband UV pulses with a shaper-assisted cross-correlation setup. A two-dimensional pulse modulator, operated in the diffractive shaping mode, is used to generate an inherently temporally overlapped reference beam. To greatly improve the usability of this method, we combined this setup with a split-mirror UV autocorrelator based on a solar-blind photomultiplier tube as sensitive nonlinearity. This allows sensitive characterization of the Fourier-limited pulses down to a few picojoules, as well as complex-shaped ultrashort UV pulses, typically occurring in coherent control experiments.

Direct measurement of the metastable3P2decay rate in krypton

We use a magneto-optical trap to isolate ${}^{84}\mathrm{Kr}$ atoms in the metastable ${}^{3}{P}_{2}$ state and then measure the rate of 125.0-nm fluorescence due to spontaneous magnetic quadrupole $(M2)$ decay. We normalize the overall fluorescence rate from the sample using a ``quenching'' process in which laser excitation provides a path for prompt decay to the ground state, with each atom emitting one 123.6-nm photon. A single, solar-blind photomultiplier tube is used to detect both the $M2$ and the quench-induced photons, so that only small corrections relating to spectral response are necessary. We find a spontaneous decay rate of $\ensuremath{\Gamma}=0.0354(22){\mathrm{s}}^{\ensuremath{-}1},$ which translates into a lifetime of 28.3(1.8) s. This result is discussed in the context of previous measurements and calculations of ${}^{3}{P}_{2}$ lifetimes in the rare gases.

Optical design of the Ultraviolet Imaging Spectrograph for the Cassini mission to Saturn

When the Cassini spacecraft arrives at Saturn early in the next century it will carry an Ultraviolet Imaging Spectrograph (UVIS) designed and built by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado. Observations made with the UVIS will support a broad set of scientific investigations including spectroscopy, imaging, and occultations. The UVIS consists of two spectroscopic channels covering the wavelength ranges 56 to 118 and 110 to 190 nm. Each channel has an off-axis parabolic telescope followed by a toroidal grating spectrograph and an imaging microchannel plate-CODACON detector. Mirror coatings and detector photocathode materials optimize the sensitivity of each channel for its particular wavelength range. Spectrograph entrance slit mechanisms provide three independent spectral and spatial resolution modes for each of the three channels. A third optical train consisting of a parabolic telescope and solar blind photomultiplier tube with a CsI photocathode provides a high-sensitivity photometer mode within the UVIS. The UVIS configuration was selected as a balanced solution to a large number of engineering and scientific constraints. We describe these constraints, the optical design, and the anticipated performance of the instrument.

Double-Modulation Technique for a Multielemental Voigt Detector

A double-modulation technique (modulation of light source and magnetic field) was applied to a multielemental detector in the Voigt configuration. This was intended to overcome the problem that even in the absence of analyte atoms source radiation leaks through the polarizers in the orthogonal configuration, resulting in an undesirable offset signal. Four hollow-cathode lamps as light sources were operated with sinusoidal currents at four different frequencies (several hundred Hz) while the magnetic field was modulated at 60 Hz. As a result, side-band waves appeared at f0±60 Hz, where f0 was the frequency of the light source modulation. The signals from a solar-blind photomultiplier tube were converted into a power spectrum in a frequency domain after a fast Fourier transformation (FFT), followed by the detection of each side-band peak. Thus, multielemental Voigt signals were selectively discriminated without interference of the offset signal peaks at the light modulation frequencies.

Laser-excited atomic fluorescence spectrometry using graphite tube electrothermal atomisation and double-resonance excitation

Laser-excited atomic fluorescence spectrometry using double-resonance excitation and graphite tube electrothermal atomisation is evaluated for the determination of trace elements. Two dye lasers pumped by a Nd: YAG laser were used to excite atoms inside a graphite tube furnace simultaneously. Collisional coupling between the highest level reached by the laser excitation and nearby levels resulted in several fluorescence transitions in the ultraviolet region for each specific element. The fluorescence was collected at 90° by combining a pierced plane mirror, a plano-convex MgF2 lens and a double monochromator equipped with a solar blind photomultiplier tube. The detection limits of In, Ga and Yb were 2, 1 and 220 fg, respectively.

A non-dispersive AMOR (atomic magneto-optical rotation) analyzer for multielement trace determination.

A non-dispersive AMOR (atomic magneto-optical rotation) analyzer was tentatively con structed for multielement analysis and its analytical performance was examined for deter minations of Mg and Zn. The hollow cathode lamps of Mg and Zn were modulated at different frequencies. The source radiations from the lamps were merged by a grid mirror. The rotatory radiation emerging from the optical system in the Faraday configuration was received by a solar-blind photomultiplier tube. The signals of Mg and Zn were separated by the fast Fourier transformation (FFT) processing.

Improved Lyman-alpha hygrometer for small-scale atmospheric turbulence measurements. Part II: The O2 filtering technique

The detector of the IMST/SA-CNRS improved Lyman-alpha hygrometer is a solar-blind photomultiplier tube that ensures large signal-to-noise ratio and allows a miniaturization of the sampling volume. This PM tube has a relatively large spectral response and can detect, in addition to the Lyman-alpha line, hydrogen molecular transitions emitted by the discharge source between 120 and 180 nm. In order to avoid a spurious sensitivity to oxygen density fluctuations, an active filtering cell is added to absorb the undesired lines. The instrument sensitivity is calculated with the help of a two-gas, three-spectral-line UV-beam absorption model, fitted to calibration measurements. The technique of the active filtering associated with the three-line absorption model produces the following advantages: (1) reduced sensitivity to oxygen fluctuations, (2) a clear physical meaning to the model terms allowing the sensitivity computation in most conditions, (3) increased signal-to-noise ratio, and (4) in most conditions, improved sensitivity to water vapor compared to the monochromatic Lyman-alpha line.