Gas-filled Detectors Research Articles

The output factor correction as function of the photon beam field size – direct measurement and calculation from the lateral dose response functions of gas-filled and solid detectors

The first aim of this study has been to extend the systematic experimental study of the field size dependence of the output factor correction for three micro-ionization chambers (PTW 31014, PTW 31022 and IBA Razor chamber), two silicon diodes (PTW 60017 and IBA Razor Diode) and the synthetic diamond detector microDiamond (PTW 60019) in a 6 MV photon beam down to an effective field side length of 2.6mm, and to summarize the present knowledge of this factor by treating it as a function of the dosimetric field size. In order to vary the dosimetric field size over this large range, output factors measurements were performed at source-to-surface distances of 60cm and 90cm. Since the output factors obtained with the organic scintillation detector Exradin W1 (Standard Imaging, Middleton, USA) at all field sizes closely agreed with those measured by EBT3 radiochromic films (ISP Corp, Wayne, USA), the scintillation detector served as the reference detector. The measured output correction factors reflect the influences of the volume averaging and density effects upon the uncorrected output factor values. In case of the microDiamond detector these opposing influences result in output factor correction values less than 1 for moderately small field sizes and larger than 1 for very small field sizes. Our results agree with most of the published experimental as well as Monte-Carlo simulated data within detector-specific limits of uncertainty. The dosimetric field side length has been identified as a reliable determinant of the output factor correction, and typical functional curve shapes of the field-size dependent output factor correction vs. dosimetric field side length have been associated with gas-filled, silicon diode and synthetic diamond detectors.The second aim of this study has been a novel, semi-empirical approach to calculate the field-size dependent output correction factors of small photon detectors by convolving film measured true dose profile data with measured lateral response functions of the detectors. To achieve this, the set of previously published 2D lateral dose response functions was complemented by those of the novel detectors PTW PinPoint chamber 31022 (PTW Freiburg, Freiburg, Germany), Razor chamber and Razor Diode (IBA Dosimetry, Schwarzenbruck, Germany). The output correction factors calculated from the lateral dose response functions closely fit with the directly measured output correction factors, thus supporting the latter by an independent method.

WITHDRAWN: Testing CuO Nanowires as a Novel X-ray to Electron Converter for Gas-filled Radiation Detectors

WITHDRAWN: Testing CuO Nanowires as a Novel X-ray to Electron Converter for Gas-filled Radiation Detectors

Bulk Crystal Growth, and High-Resolution X-ray Diffraction Results of LiZnAs Semiconductor Material

LiZnAs is being explored as a candidate for solid-state neutron detectors. The compact form, solid-state device would have greater efficiency than present day gas-filled 3He and 10BF3 detectors. Devices fabricated from LiZnAs having either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) as constituent atoms may provide a material for compact high efficiency neutron detectors. The 6Li(n,t)4He reaction yields a total Q-value of 4.78 MeV, an energy larger than that of the 10B reaction, which can easily be identified above background radiations. LiZnAs material was synthesized by preparing equimolar portions of Li, Zn, and As sealed under vacuum (10−6 Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace (Montag et al. in J Cryst Growth 412:103, 2015). The raw synthesized LiZnAs was purified by a static vacuum sublimation in quartz (Montag et al. in J Cryst Growth 438:99, 2016). Bulk crystalline LiZnAs ingots were grown from the purified material with a high-temperature Bridgman-style growth process described here. One of the largest LiZnAs ingots harvested was 9.6 mm in diameter and 4.2 mm in length. Samples were harvested from the ingot and were characterized for crystallinity using a Bruker AXS Inc. D8 AXS Inc. D2 CRYSO, energy dispersive x-ray diffractometer, and a Bruker AXS Inc. D8 DISCOVER, high-resolution x-ray diffractometer equipped with molybdenum radiation, Gobel mirror, four bounce germanium monochromator and a scintillation detector. The primary beam divergence was determined to be 0.004°, using a single crystal Si standard. The x-ray based characterization revealed that the samples nucleated in the (110) direction and a high-resolution open detector rocking curve recorded on the (220) LiZnAs yielded a full width at half maximum (FWHM) of 0.235°. Sectional pole figures using off-axis reflections of the (211) LiZnAs confirmed in-plane ordering, and also indicated the presence of multiple domains. The LiZnAs bulk crystals exhibited a Primitive Cubic Bravais lattice instead of the commonly reported Face-centered Cubic Bravais lattice. The lattice constant was determined to be 5.5146 ± 0.0003 A.

Device fabrication, characterization, and thermal neutron detection response of LiZnP and LiZnAs semiconductor devices

Nowotny-Juza compounds continue to be explored as candidates for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q-value of 4.78MeV, larger than 10B, an energy easily identified above background radiations. Hence, devices fabricated from semiconductor compounds having either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) as constituent atoms may provide a material for compact high efficiency neutron detectors. Starting material was synthesized by preparing equimolar portions of Li, Zn, and As sealed under vacuum (10−6Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace [1]. The raw synthesized material indicated the presence high impurity levels (material and electrical property characterizations). A static vacuum sublimation in quartz was performed to help purify the synthesized material [2,3]. Bulk crystalline samples were grown from the purified material [4,5]. Samples were cut using a diamond wire saw, and processed into devices. Bulk resistivity was determined from I–V curve measurements, ranging from 106–1011Ω cm. Devices were characterized for sensitivity to 5.48MeV alpha particles, 337nm laser light, and neutron sensitivity in a thermal neutron diffracted beam at the Kansas State University TRIGA Mark II nuclear reactor. Thermal neutron reaction product charge induction was measured with a LiZnP device, and the reaction product spectral response was observed.

Ultracold neutron detector for neutron lifetime measurements

The gas-filled detector of ultracold neutrons has been designed and constructed for the spectrometer of the neutron lifetime measurements at the ILL, Grenoble, France. The detector has been successfully tested and is currently being used at this spectrometer. We could show that minimization of the “wall” effect is a key factor to ensure efficient background suppression and to maximize the detection efficiency. This effect is primarily related to the composition of the gas mixture, which crucially depends on the neutron velocity spectrum.

Static sublimation purification process and characterization of LiZnAs semiconductor material

Refinement of the class AIBIICV materials continue as a candidate for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q value of 4.78MeV, larger than 10B, and easily identified above background radiations. Hence, devices composed of either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) may provide a semiconductor material for compact high efficiency neutron detectors. A sub-branch of the III–V semiconductors, the filled tetrahedral compounds, AIBIICV, known as Nowotny–Juza compounds, are known for their desirable cubic crystal structure. Starting material was synthesized by equimolar portions of Li, Zn, and As sealed under vacuum (10−6Torr) in quartz ampoules with a boron nitride lining, and reacted in a compounding furnace [1]. The synthesized material showed signs of high impurity levels from material and electrical property characterization. In the present work, a static vacuum sublimation of synthesized LiZnAs loaded in a quartz vessel was performed to help purify the synthesized material. The chemical composition of the sublimed material and remains material was confirmed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Lithium was not detected in the sublimed material, however, near stoichiometric amounts of each constituent element were found in the remains material for LiZnAs. X-ray diffraction phase identification scans of the remains material and sublimed material were compared, and further indicated the impurity materials were removed from the synthesized materials. The remaining powder post the sublimation process showed characteristics of a higher purity ternary compound.

Testing the prototype detectors for the muon tracking system of the CBM experiment at the CERN PS accelerator

Performance of the gas-filled detector prototypes based on the GEM, TGEM, and Micromegas technologies was studied on the test beam of the CERN PS accelerator. Three-component mixtures based on Ar and He were used as the working gas. For all tested detector prototypes, the gas amplification factors were measured, and the detection efficiencies, cluster distributions, and the radii of the charge cloud collected on the readout electrode were estimated.

A secondary-emission gaseous chamber

A gas-filled secondary emission detector with a gap of ~100 μm wide and a field strength of ~50 kV/cm is considered as a possible active element of the hadron calorimeter. The detector must be fast, radiation-hard, and easy to manufacture. A detector model has been produced and tested. Its characteristics are presented.

Testing the prototype detectors for the muon tracking system of the CBM experiment on the proton beam of the PNPI accelerator at high counting rates

Performance of the gas-filled detector prototypes based on the GEM, TGEM, and Micromegas technologies was studied with the aim of selecting variants for tracking detectors of the muon system for the CBM Experiment. The study was performed on the test beam of the proton accelerator at the Petersburg Nuclear Physics Institute (PNPI). Three-component mixtures based on Ar and He were used as the working gas. For all tested detector prototypes, the detection efficiencies were measured, and the modification of the amplitude spectra as a function of the incident beam intensity was investigated.

Азотна кріосистема з регулюванням температури для охолодження газонаповнених детекторів іонізуючого випромінювання

Азотна кріосистема з регулюванням температури для охолодження газонаповнених детекторів іонізуючого випромінювання

A study of the coordinate gas-filled detectors based on the Micromegas and Micromegas + GEM/TGEM technologies for the muon tracking system of the CBM experiment

Prototypes of the gas-filled detectors produced on the basis of the Micromegas technology, as well as in combination with the Micromegas + GEM/TGEM structures in the multistage gas amplification circuit have been investigated with the aim of selecting variants for tracking detectors of the muon system designed for operating at high counting rates in the Compressed Baryonic Matter (CBM) experiment. Two- and three-component Ar- and He-based mixtures have been tested as the working gas. Their key characteristics are presented. The gas amplification factors are measured for various high-voltage modes, and the charge collection times determining the response speed of the tested detectors are estimated.

Investigating the lifetime of bromine-quenched G.M. Counters with temperature

The amount of halogen quench gas as a percentage of the total fill gas contained within a gas-filled Geiger–Müller detector is directly linked to its operational characteristics. Preserving this halogen gas will help maintain the operating lifetime of the detectors. Such halogen gases are highly corrosive and the small quantities within a gas-filled detector can deplete rapidly via interactions with surrounding materials. The rate of interactions is thought to be proportional to not only temperature, but also to the current initiated by ionisation events associated with the formation of each signal pulse. As all pulses are of similar magnitudes, GM detector operational lifetimes are quantified in accumulated counts rather than a given operating time. We have studied three different types of corrosion-resistant mechanisms to protect the bromine halogen gas from any interactions with 446 stainless steel detector components of ZP1200 Geiger–Müller tubes at temperatures up to 125°C. Three types of surface treatments for these detectors used were labelled as “raw” using only an oxygen-plasma-bombardment process, “passivated” using a combination of nitric acid passivation followed by an oxygen plasma-bombardment process, and thirdly plating with a few micron thickness of chromium followed by an oxygen plasma-bombardment process. 32 detector samples were irradiated at room temperature with a Caesium-137 source at dose rates of approximately 1.3mSv/hr up to 5.7×1010 accumulated counts; another 32 detector samples were aged to 3.3×1010 counts at 125°C. At room temperature, the chromium-plated samples exhibited an initial rise in their starting voltage readings. All other detector performance characteristics, for all detector types, did not change significantly during the ageing process, and the surface morphology of the detector cathodes was unaffected. At 125°C, the chromium-based plating produced the most stable long-term response. These chromium-plated samples showed no evidence of bromine deposits on the cathode samples investigated via Energy-Dispersive X-ray Spectroscopy. The raw and passivated samples, however, did show traces of bromine independent of the age of the detector. Preliminary investigations we have carried out at 175°C highlight the importance of the chromium plating layer in preserving long-term detector performances at elevated temperatures.

Development of compact high efficiency microstructured semiconductor neutron detectors

Semiconductor diode detectors coated with neutron reactive materials are generally fashioned as planar diodes coated with 10B, 6LiF, or Gd. Planar detectors coated with 10B or 6LiF are limited to less than 5% intrinsic thermal neutron detection efficiency. Detectors coated with Gd can achieve higher efficiencies, but the low-energy signatures are problematic in the presence of background radiations. Microstructured semiconductor neutron detectors (MSNDs) can now achieve a tenfold increase in neutron detection efficiency over the planar diode designs. These semiconductor neutron detectors are fashioned with a matrix of microstructured patterns etched deeply into the semiconductor substrate and, subsequently, backfilled with neutron reactive materials. Intrinsic thermal-neutron detection efficiencies exceeding 35% have been achieved with devices no thicker than 1 mm while operating on less than 5 V, now allowing for instrumentation to be realized with similar performance as 3He gas-filled detectors.

Static sublimation purification process and characterization of LiZnP semiconductor material

Refinement of the class AIBIICV materials continue as a candidate for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q value of 4.78MeV, larger than 10B, and easily identified above background radiations. Hence, devices composed of either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) may provide a semiconductor material for compact high efficiency neutron detectors. A sub-branch of the III–V semiconductors, the filled tetrahedral compounds, AIBIICV, known as Nowotny–Juza compounds, are known for their desirable cubic crystal structure. Starting material was synthesized by combining equimolar portions of Li, Zn, and P sealed under vacuum (10−6Torr) in quartz ampoules, having boron nitride liners, and subsequently reacted in a compounding furnace (Montag et al., 2015, J. of Cryst. Growth). A static vacuum sublimation in quartz was performed to help purify the synthesized material. The chemical composition of the sublimed material and remaining material was confirmed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Lithium was not detected in the sublimed material, however, approximately stoichiometric concentrations of each constituent element were found in the remaining LiZnP material. X-ray diffraction phase identification scans of the remains material and sublimed material were compared, and further indicated the impurity materials were sublimed away from the synthesized materials. The resulting material from the sublimation process showed characteristics of a higher purity ternary compound.

Bulk crystal growth, and high-resolution x-ray diffraction results of LiZnP semiconductor material

Nowotny–Juza compounds continue to be explored as a candidate for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q-value of 4.78MeV, larger than 10B, an energy easily identified above background radiations. Hence, devices fabricated from semiconducting compounds containing either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) may provide a semiconductor material for compact high efficiency neutron detectors. Starting material was synthesized by preparing equimolar portions of Li, Zn, and P sealed under vacuum (10−6Torr) in quartz ampoules lined with boron nitride and subsequently reacted in a compounding furnace [1]. The synthesized material showed signs of high impurity levels from material and electrical property characterizations. A static vacuum sublimation in quartz was performed to help purify the synthesized material [2]. Bulk crystalline samples were grown from the purified material. An ingot 9.6mm in diameter and 4.0mm in length was harvested. Individual samples were characterized for crystallinity on a Bruker AXS Inc. D2 CRYSO, energy dispersive x-ray diffractometer, and a Bruker AXS D8 DISCOVER, high-resolution x-ray diffractometer with a 0.004° beam divergence. The (220) orientation was characterized as the main orientation with the D2 CRYSO, and confirmed with the D8 DISCOVER. An out-of-plane high-resolution rocking curve yielded a 0.417° full width at half maximum (FWHM) for the (220) LiZnP. In-plane ordering was confirmed by observation of the (311) orientation, where a rocking curve was collected with a FWHM of 0.294°.

A study of the coordinate gas-filled detectors based on the GEM and TGEM technologies for the muon tracking system of the CBM experiment

Prototypes of the gas-filled detectors based on the GEM and TGEM technologies have been studied in the multistage gas amplification circuit with the aim of selecting variants for tracking detectors of the muon system capable of operating at high counting rates in the CBM experiment. Two- and three-component mixtures based on Ar and He are used as the working gas. Their key characteristics are presented. The gas amplification factors are measured for various high-voltage modes. The charge collection times determining the response speed of the tested detectors are estimated.

High-efficiency microstructured semiconductor neutron detectors for direct 3He replacement

High-efficiency Microstructured Semiconductor Neutron Detectors (MSNDs) have been tiled and arranged in a cylindrical form factor in order to serve as a direct replacement to aging and increasingly expensive 3He gas-filled proportional neutron detectors. Two 6-in long by 2-in diameter cylinders were constructed and populated with MSNDs which were then directly compared to a 4atm Reuter Stokes 3He detector of the same dimensions. The Generation 1 MSND-based 3Helium-Replacement (HeRep Mk I) device contained sixty-four 1-cm2 active-area MSNDs, each with an intrinsic neutron detection efficiency of approximately 7%. A Generation 2 device (the HeRep Mk II) was populated with thirty 4-cm2 active-area MSNDs, with an intrinsic thermal neutron detection efficiency of approximately 30%. The MSNDs of each HeRep were integrated to count as a single device. The 3He proportional counter and the HeRep devices were tested while encased in a cylinder of high-density polyethylene measuring a total of 6-in by 9-in. The 3He counter and the HeRep Mk II were each placed 1m from a 54-ng 252Cf source and tested for efficiency. The 3He proportional counter had a net count rate of 17.13±0.10cps at 1m. The HeRep Mk II device had a net count rate of 17.60±0.10cps, amounting to 102.71±2.65% of the 3He gas counter while inside of the moderator. Outside of moderator, the 3He tube had a count rate of 3.35±0.05cps and the HeRep Mk II device reported 3.19±05, amounting to 95.15±9.04% of the 3He neutron detector.

Position-sensitive soft X-ray detectors and their application

The designs and characteristics of linear and curved position-sensitive gas-filled detectors of soft X rays are described. The best result obtained with a gas mixture based on xenon is near 40 μm (CuKα). The information of their use in X-ray scientific equipment is presented.

Thermoregulated Nitric Cryosystem for Cooling Gas-Filled Detectors of Ionizing Radiation

Thermoregulated Nitric Cryosystem for Cooling Gas-Filled Detectors of Ionizing Radiation

Synthesis and characterization of LiZnP and LiZnAs semiconductor material

Research for a reliable solid-state semiconductor neutron detector continues because such a device has not been developed, and would have greater efficiency, than present-day gas-filled 3He and 10BF3 neutron detectors. Further, a semiconductor neutron detector would be more compact and rugged than most gas-filled or scintillator neutron detectors. The 6Li(n,t)4He reaction yields a total Q value of 4.78MeV, a larger yield than the 10B(n,α)7Li, and is easily identified above background radiation interactions. Hence, devices composed of either natural Li (naturally 7.5% 6Li) or enriched 6Li (approximately 95% 6Li) may provide a semiconductor material for compact high-efficiency neutron detectors. A sub-branch of the III-V semiconductors, the filled tetrahedral compounds, known as Nowotny-Juza compounds (AIBIICV), are desirable for their cubic crystal structure and semiconducting electrical properties. These compounds were originally studied for photonic applications. In the present work, Equimolar portions of Li, Zn, and P or As were sealed under vacuum (10−6Torr) in quartz ampoules with a boron nitride lining, and loaded into a compounding furnace. The ampoule was heated to 200°C to form the Li-Zn alloy, subsequently heated to 560°C to form the ternary compound, LiZnP or LiZnAs, and finally annealed to promote crystallization. The chemical composition of the synthesized starting material was confirmed at Galbraith Laboratories, Inc. by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES), which showed the compounds can be reacted in equal ratios, 1-1-1, to form ternary compounds. Recent additions to the procedure have produced higher yields, and greater synthesis reliability. Synthesized powders were also characterized by x-ray diffraction, where lattice constants of 5.751±.001Å and 5.939±.002Å for LiZnP and LiZnAs, respectively, were determined.