Glass GEM Research Articles

Commissioning of the MIGDAL detector with fast neutrons at NILE/ISIS

Many dark matter experiments are exploiting the Migdal effect, a rare atomic process, to improve sensitivity to low-mass (sub-GeV) WIMP-like dark matter candidates. However, this process is yet to be directly observed in nuclear scattering. The MIGDAL experiment aims to make the first unambiguous measurement of the Migdal effect in nuclear scattering. A low-pressure optical Time Projection Chamber is used to image in three-dimensions the characteristic signature of a Migdal event: an electron and a nuclear recoil track sharing a common vertex. Nuclear recoils are induced using fast neutrons from a D–D source, which scatter in the gaseous volume of the detector. The experiment is operated with 50 Torr of CF4 using two glass GEMs for charge amplification. Both light and charge are read-out, and these measurements are combined for track reconstruction. Commissioning data has been recorded with fast neutrons at the Neutron Irradiation Laboratory for Electronics (NILE) at Rutherford Appleton Laboratory in the UK. Results of the experiment’s commissioning and the performance of the detector with a high rate of highly ionising nuclear recoils are presented, along with results from low energy electrons. Initial results of light and charge read-out with low pressure noble gas mixtures are also presented.

High-tolerance nickel metalized glass gas electron multiplier: development and performance evaluation

Micro-patterned gas detectors (MPGDs) are an important type of gaseous detector that can amplify and detect a small amount of electric charge generated by the interaction between radiation and gas. These detectors have high gain and high spatial resolution, making them useful in various applications ranging from high energy physics to medical instrumentation. However, one of the most widely used MPGDs, Gaseous Electron Multipliers (GEMs), may often experiences electrical discharges due to excessive electric field in the small space, which reduces their durability. To address this issue, we previously have developed a new type of GEM that uses glass as the insulator instead of conventional materials. Our glass GEM demonstrated excellent gas gain and energy resolution characteristics. In this work, we used nickel as the electrode, which has a higher melting point than copper and showed higher durability against arc discharges. Moreover, the nickel glass GEM performed comparably to conventional Cu-based glass GEMs in evaluation using radiation isotopes. Our findings suggest that our new glass GEM with nickel electrodes is a promising solution to the durability problem of conventional GEMs. This could lead to improvements in the performance and longevity of MPGDs, which could have significant implications for various applications in the fields of physics, engineering, and medicine.

3D track reconstruction of low-energy electrons in the MIGDAL low pressure optical time projection chamber

We demonstrate three-dimensional track reconstruction of electrons in a low pressure (50 Torr) optical TPC consisting of two glass GEMs with an ITO strip readout in CF4 and CF4/Ar mixtures. The reconstructed tracks show a variety of event topologies, including short tracks from photoelectrons induced by 55Fe 5.9 keV X-rays and long tracks from gamma ray interactions and beta decays. Algorithms for event identification and track ridge detection are discussed as well as multiple methods for integrating information from the camera image and ITO waveforms with the goal of full 3D reconstruction of the track.

Development of a Novel Fabrication Process for Application in Glass Gas Electron Multiplier Detectors

Gas electron multipliers (GEMs) have been widely used for particle collection and signal amplification. Because of the advantages of glass, such as high hardness, aging resistance, and dielectric strength, research into its application as a substrate material in GEM design and process has attracted extensive attention in recent years. This paper compares two commonly used glass GEM structural designs and shows that the optical transparency of the hexagonal symmetric structure is superior to that of the rectangle structure. An electric field model is developed to characterize the negative correlation between the hole diameter and the electric field strength. The structure of glass GEM is designed according to the feasibility of the process. A new process method of surface metal patterning using hole filling to form a mask is proposed, which can meet the high alignment and shaping requirements of the perfect match between the opening of metal layer and the aperture shape of the substrate. Combined with the advanced laser hole modification process, a glass GEM sample with a hole diameter of 70 μm, a spacing of 140 μm, a substrate thickness of 240 μm, and a metal thickness of 13 μm is obtained. Finally, particle trajectories, avalanche region coverage, and electron energy are discussed based on the prototype structure.

Development of a Bragg-edge Neutron Transmission Imaging Detector Combined with Micro-structured Boron Cathode and Glass Gas Electron Multiplier

Development of a Bragg-edge Neutron Transmission Imaging Detector Combined with Micro-structured Boron Cathode and Glass Gas Electron Multiplier

Gas gain measurement for charged particle spectroscopy using glass GEM in low-pressure P-10 gas

A glass gas electron multiplier (GEM) was tested to evaluate performance for charged particle spectroscopy in a gas chamber. The test was done with varying low-pressure Ar/CH4 mixture gas (9:1, P-10) for evaluation of effective electron multiplication gain (gas gain) with the relationship between supplied voltage to GEM (GEM ΔV), energy and timing resolution of signals. The GEM ΔV is parameterized as a function of gas gain and pressure from experimental results. The signal-to-noise ratio on the anode signal was significantly improved due to electron multiplication by the glass GEM in comparison with traditional grid gas ionization chamber. A test using Ar/CO2 mixture gas (9:1) shows that GEM ΔV is successfully reduced with keeping gas gain and energy resolution comparable. Time difference between anode and cathode signals behaves reasonably with drift time of initial electrons. We conclude that charged particle spectrometer using glass GEM can be designed by using obtained parameter. The spectrometer is useful especially for low energy charged particle due to the gas gain.

Two-Sided Glass Gems from the Sarmatian Burials of the Lower Volga Region

Two-Sided Glass Gems from the Sarmatian Burials of the Lower Volga Region

Двусторонние геммы-литики из погребения № 13 кургана № 1 могильника «Богомольные пески-I»

The article examines five double-sided glass gems found as elements of a bracelet on the left wrist of a child aged 2,5–3 years in the burial no. 13 of the kurgan no. 1 of the “Bogomol’nye peski-I” group near the village of Nikol’skoe, Enotaevskiy District, Astrakhan Region. The inventory of the burial gives grounds for its dating within a broad frame of the 1st – first half of the 2nd century AD. As in the Scythian burials of the Dnieper region, glass gems in the kurgan of the “Bogomol’nye peski-I” group were found in a child’s burial. They were considered by their owners as items of jewelry and amulets, and not as a means for imprinting images. It is worth noting that the images on the sides of the same gem are rarely semantically related to each other, but rather give the impression of a rather random choice of subjects. In many cases, the motives go back to gems of the late Classical and Hellenistic periods. Given the fact that the images on the glass gems were mechanically reproduced from intaglios, there is reason to suppose that these were works of glyptics from the late Hellenistic period, which could theoretically be used for making glass gems at a later period. The uniqueness of double-sided glass gems, on the one hand, and their distribution in the North Pontic region in the 6th–4th centuries BC, on the other hand, give grounds to suggest the possibility of the origin of finds originating from the Sarmatian burials of the Lower Volga region from the workshops of the North Black Sea region, possibly of the Bosporan Kingdom.

Energy-resolved neutron imaging with glass gas electron multiplier and dynamic time-over-threshold method

Energy-resolved neutron imaging with pulsed neutron source provides quantitative neutron imaging techniques such as Bragg-edge imaging, resonance absorption imaging, and polarized neutron imaging. Micro-pattern gaseous detectors (MPGDs) such as gas electron multipliers (GEMs) are widely used in neutron detection. In this research, we will report on the first demonstration of energy-resolved neutron imaging with a glass gas electron multiplier (G-GEM) and the dynamic time-over-threshold (dToT) signal processing method. We successfully performed energy-resolved neutron imaging at J-PARC MLF by measuring incident position and the Time-of-Flight (TOF) of each neutron simultaneously.

A glass Gem Depicting a Dying Niobid From the National Museum in Warsaw

The National Museum in Warsaw holds a diverse collection of glass gems, both ancient and modern. One of these, a specimen depicting a dying Niobid supported by his sister, belongs to a wider group of objects scattered throughout various European museums. Such gems were mainly produced during the 1st century BC and their decoration is derived from a fragment of a relief carved by Pheidias on the statue of Zeus in Olympia which portrays the massacre of the Niobids. The fact that these gems were made of glass indicates that objects with such decorations were appreciated and popular. The myth of Niobe, in both Greek and Roman art, served multiple purposes highlighted by the choice of the story’s motives most often used in decorations. However, the reason for the use of this particular fragment of Pheidias’s relief to decorate gems as well as their popularity require additional explanation.

Thin cathode glass gas electron multiplier detector for carbon beam dose imaging

ABSTRACT An optically read-out glass gas electron multiplier (G-GEM) detector is expected to simplify complicated quality assurance measurements for hadron therapies by imaging the dose distribution of the incident beam. However, the effect of secondary particles from the detector itself has not been well studied. In this paper, we evaluate a design that reduces the secondary particles from the cathode of a G-GEM detector. Specifically, we assembled detectors with thin cathodes and assessed their effect on the secondary particle production in simulations and experiments. The experiments were carried out under 290 MeV/u 12C ion bombardment at the Heavy Ion Medical Accelerator in Chiba. The clinical intensity of the thin cathode detector was compared with that of a conventional thick cathode G-GEM detector. The improved chamber design reduced the dose contributions of secondary particles from the cathode without degrading the dose imaging performance.

Development and characterization of optical readout well-type glass gas electron multiplier for dose imaging in clinical carbon beams.

The use of carbon ion beams in cancer therapy (also known as hadron therapy) is steadily growing worldwide; therefore, the demand for more efficient dosimetry systems is also increasing because daily quality assurance (QA) measurements of hadron radiotherapy is one of the most complex and time consuming tasks. The aim of this study is to develop a two-dimensional dosimetry system that offers high spatial resolution, a large field of view, quick data response, and a linear dose-response relationship. We demonstrate the dose imaging performance of a novel digital dose imager using carbon ion beams for hadron therapy. The dose imager is based on a newly-developed gaseous detector, a well-type glass gas electron multiplier. The imager is successfully operated in a hadron therapy facility with clinical intensity beams for radiotherapy. It features a high spatial resolution of less than 1mm and an almost linear dose-response relationship with no saturation and very low linear-energy-transfer dependence. Experimental results show that the dose imager has the potential to improve dosimetry accuracy for daily QA.

Demonstration of soft X-ray 3D scanning and modeling with a glass gas electron multiplier

A new detector, based on an optical-readout glass gas electron multiplier was developed for a soft X-ray CT scanner. Soft X-ray imaging (<20 keV) provides high-contrast images of low-Z elements, such as soft tissues. We model a three-dimensional (3D) copy of a low-Z object with a high-resolution gaseous detector and a 3D printer. The detector was used to acquire high-resolution images to reconstruct a 3D computed tomography (CT) image. As an example, a fine 3D X-ray CT image of a hornet was reconstructed with high contrast. The 3D CT data were converted into 3D computer-automated design data, and a copy of the scanned object was printed with a commercial 3D printer. Overall, this work demonstrates a new use of gaseous detectors, rapid and precise soft X-ray 3D scanning, and modeling of soft tissues.

When Glass and Metal Corrode Together, VI: Chalconatronite

ABSTRACTChalconatronite, Na2[Cu(CO3)]2·3H2O, is formed as a corrosion product when copper alloys are exposed to sodium carbonate solutions in the air. This also happens when metals come into contact with corroding soda glass which forms alkaline surface films in reaction with humidity from clean air. More often, substantial amounts of formaldehyde are present indoors which react to formate via the Cannizzarro reaction and accumulate over time in the films. Twenty cases of chalconatronite (including two mentioned in the literature) are reported as occurring on heritage objects with glass in contact with copper alloys: Baroque reliquaries with set glass gems, enamel on metal (sixteenth century and a modern replica of intentionally unstable composition), Christmas tree glass baubles with wires, glass buttons with metal shanks, a glass figure with a wire support, miners’ lamps, and a glass framed daguerreotype. These confirmed identifications might help conservators in investigating similar cases to shed more light on the formation conditions.

X-ray imaging demonstration of glass GEM detector with dynamic time-over-threshold-based readout

Large-scale detection is one of the important roles for gaseous detectors to play in high-energy physics. In many cases, energy resolving multi-channel readout is required. Recent micro-pattern gaseous detectors (MPGDs) have finer pitches or pixels; hence, large-sized detectors have thousands of readout channels. In those cases, it becomes important to reduce the scale and complexity of the readout circuit while keeping its energy resolving capability. The signal processing technique called dynamic time-over-threshold (dynamic ToT, dToT) achieves both the good conversion linearity from analog to digital signal and the compact circuit scale compared with conventional analog-to-digital-converter (ADC)-based readout. In this study, we developed and demonstrated a dToT-based readout circuit for glass gas electron multiplier (glass GEM, G-GEM). The readout circuit showed better linearity than that of normal ToT. We demonstrated the readout circuit by X-ray imaging with the charge-division scheme. The good linearity of the readout circuit enabled imaging over a 100 × 100 mm2 area with small distortion. We expect that the dToT-based readout would be a promising candidate for the future readout of large-scaled MPGDs.

First result of large size Scintillating Glass GEM imager

A large size x-ray imaging gaseous detector, which has 280 × 280 mm2 effective area has been successfully developed and x-ray imaging has been demonstrated. The imaging system consists of a chamber filled with Ne/CF4 scintillating gas mixture, inside of which Glass GEM (G-GEM) is mounted for gas multiplication. In this system electrons are generated by the reaction between x-rays and the gas, and visible photons by excited Ne/CF4 gas molecules during the gas electron multiplication process in the G-GEM holes. These photons are simply detected with CCD-camera and a radiograph is formed. Here, we report on the properties of large size scintillation G-GEM and the results of using it as a digital x-ray imager with a large sensitive area.

Imaging Demonstration of a Glass Gas Electron Multiplier with Electronic Charge Readout

We have developed a Glass Gas Electron Multiplier (Glass GEM, G-GEM), which is composed of two copper electrodes separated by a photosensitive etchable glass substrate having holes arranged in a hexagonal pattern. In this paper, we report the result of imaging using a G-GEM combined with a 2D electronic charge readout. We used a crystallized photosensitive etchable glass as the G-GEM substrate. A precise X-ray image of a small mammal was successfully obtained with position resolutions of approximately 110 to 140 μm in RMS.

When Glass and Metal Corrode Together, V: Sodium Copper Formate

ABSTRACTA sodium copper formate, first described in 2002, can also form on copper alloys with sodium originating from soda glass hydrolysis. The frequent occurrence (50% of 250 cases of glass-induced metal corrosion) is due to the presence of formaldehyde emissions in storage and its direct reaction to formate in the alkaline surface films. The compound can be produced without the presence of acetate when chalconatronite or metal coupons immersed in soda solution are exposed to formaldehyde vapours. The crystal structure, derived from X-ray powder diffraction, yielded the sum formula Cu4Na4O(HCOO)8(OH)2·4H2O. Except for the absence of acetate in the structure, this is in good agreement with the 2002 publication. To assess which kind of combined glass/metal objects are affected, a number of large museum collections were surveyed. Sodium copper formate was detected as a corrosion product using mainly micro-Raman spectroscopy, for instance, on 18 painted Limoges enamels, eight glass vessels with metal mountings, glass beads on metal wire from 11 bridal crowns, nine Christmas tree balls with wire decoration, 40 pieces of jewellery with glass gems, three daguerreotypes, and one miniature with cover glasses.

Gaseous flat-panel detector with glass gas electron multiplier coupled with micro-photodiode array

In this study, we propose and demonstrate a novel imaging system, a gaseous flat-panel detector (FPD). The gaseous FPD consists of a glass gas electron multiplier (G-GEM) with a scintillation gas, which is optically coupled with photodiode panel fabricated with liquid crystal display technology. The G-GEM is ideal as a low energy deposition radiation detector because of its single stage high gas-gain and hence, its high photon yield. We obtained a preliminary X-ray image with the system by using a Ne/CF4 90/10 gas mixture. The typical position resolution was 0.93 mm in FWHM, which was obtained from the fitting of edge profiles

Gas scintillation glass GEM detector for high-resolution X-ray imaging and CT

A high-spatial-resolution X-ray-imaging gaseous detector has been developed with a single high-gas-gain glass gas electron multiplier (G-GEM), scintillation gas, and optical camera. High-resolution X-ray imaging of soft elements is performed with a spatial resolution of 281µm rms and an effective area of 100×100mm. In addition, high-resolution X-ray 3D computed tomography (CT) is successfully demonstrated with the gaseous detector. It shows high sensitivity to low-energy X-rays, which results in high-contrast radiographs of objects containing elements with low atomic numbers. In addition, the high yield of scintillation light enables fast X-ray imaging, which is an advantage for constructing CT images with low-energy X-rays.