Searcharxiv⌕ Search

arXiv subjects

V. Dangendorf

Publications and source records attributed to V. Dangendorf.

36 records · Page 2Linked to original sources
arXiv2007

Investigations of a THGEM-based imaging detector

We present the results of our recent studies on a Thick Gas Electron Multiplier (THGEM)-based imaging detector prototype. It consists of two 100x100 mm^2 THGEM electrodes in cascade, coupled to a resistive anode. The event location is recorded with a 2D double-sided readout electrode equipped with discrete delay-lines and dedicated electronics. The THGEM electrodes, produced by standard printed-circuit board and mechanical drilling techniques, a 0.4 mm thick with 0.5 mm diameter holes spaced by 1 mm. Localization resolutions of about 0.7 mm (FWHM) were measured with soft x-rays, in a detector operated with atmospheric-pressure Ar/CH4; good linearity and homogeneity were achieved. We describe the imaging-detector layout, the resistive-anode 2D readout system and the imaging properties. The THGEM has numerous potential applications that require large-area imaging detectors, with high-rate capability, single-electron sensitivity and moderate (sub-mm) localization resolution.

physics.ins-det↗
arXiv2007

Operation of a Thick Gas Electron Multiplier (THGEM) in Ar, Xe and Ar-Xe

We present the results of our recent studies of a Thick Gaseous Electron Multiplier (THGEM)-based detector, operated in Ar, Xe and Ar:Xe (95:5) at various gas pressures. Avalanche-multiplication properties and energy resolution were investigated with soft x-rays for different detector configurations and parameters. Gains above 10E4 were reached in a double-THGEM detector, at atmospheric pressure, in all gases, in almost all the tested conditions; in Ar:Xe (95:5) similar gains were reached at pressures up to 2 bar. The energy resolution dependence on the gas, pressure, hole geometry and electric fields was studied in detail, yielding in some configurations values below 20% FWHM with 5.9 keV x-rays.

physics.ins-det↗
arXiv2007

A Compact High-Energy Neutron Spectrometer

A compact liquid organic neutron spectrometer (CLONS) based on a single NE213 liquid scintillator (5 cm diam. x 5 cm) is described. The spectrometer is designed to measure neutron fluence spectra over the energy range 2-200 MeV and is suitable for use in neutron fields having any type of time structure. Neutron fluence spectra are obtained from measurements of two-parameter distributions (counts versus pulse height and pulse shape) using the Bayesian unfolding code MAXED. Calibration and test measurements made using a pulsed neutron beam with a continuous energy spectrum are described and the application of the spectrometer to radiation dose measurements is discussed.

physics.ins-det↗
arXiv2007

A position- and time-sensitive photon-counting detector with delay-line read-out

We have developed image intensifier tubes with delay-anode read-out for time- and position-sensitive photon counting. The timing precision is better than 1 ns with 1000x1000 pixels position resolution and up to one megacounts/s processing rate. Large format detectors of 40 and 75 mm active diameter with internal helical-wire delay-line anodes have been produced and specified. A different type of 40 and 25 mm tubes with semi-conducting screen for image charge read-out allow for an economic and robust tube design and for placing the read-out anodes outside the sealed housing. Two types of external delay-line anodes, i.e. pick-up electrodes for the image charge, have been tested. We present tests of the detector and anode performance. Due to the low background this technique is well suited for applications with very low light intensity and especially if a precise time tagging for each photon is required. As an example we present the application of scintillator read-out in time-of-flight (TOF) neutron radiography. Further applications so far are Fluorescence Life-time Microscopy (FLIM) and Astronomy

physics.ins-det↗
arXiv2006

Neutron imaging with a Micromegas detector

The micropattern gaseous detector Micromegas has been developed for several years in Saclay and presents good performance for neutron detection. A prototype for neutron imaging has been designed and new results obtained in thermal neutron beams are presented. Based on previous results demonstrating a good 1D spatial resolution, a tomographic image of a multiwire cable has been performed using a 1D Micromegas prototype. The number of pillars supporting the micromesh is too large and leads to local losses of efficiency that distort the tomographic reconstruction. Nevertheless, this first tomographic image achieved with this kind of detector is very encouraging. The next worthwhile development for neutron imaging is to achieve a bi-dimensional detector, which is presented in the second part of this study. The purpose of measurements was to investigate various operational parameters to optimize the spatial resolution. Through these measurements the optimum spatial resolution has been found to be around 160 microns (standard deviation) using Micromegas operating in double amplification mode. Several 2D imaging tests have been carried out. Some of these results have revealed fabrication defects that occurred during the manufacture of Micromegas and that are limiting the full potential of the present neutron imaging system.

physics.ins-det↗
arXiv2006

Advances in imaging THGEM-based detectors

The thick GEM (THGEM) [1] is an "expanded" GEM, economically produced in the PCB industry by simple drilling and etching in G-10 or other insulating materials (fig. 1). Similar to GEM, its operation is based on electron gas avalanche multiplication in sub-mm holes, resulting in very high gain and fast signals. Due to its large hole size, the THGEM is particularly efficient in transporting the electrons into and from the holes, leading to efficient single-electron detection and effective cascaded operation. The THGEM provides true pixilated radiation localization, ns signals, high gain and high rate capability. For a comprehensive summary of the THGEM properties, the reader is referred to [2, 3]. In this article we present a summary of our recent study on THGEM-based imaging, carried out with a 10x10 cm^2 double-THGEM detector.

physics.med-ph↗
arXiv2006

Thick GEM-like (THGEM) detectors and their possible applications

Thick GEM-like (THGEM) electrodes are robust, high gain gaseous electron multipliers, economically-manufactured by standard drilling and etching of thin printed circuit board or other materials. Their operation and structure are similar to that of standard GEMs but with 5 to 20-fold expanded dimensions. Due to the larger hole dimensions they provide up to 10^5 and 10^7 charge multiplication, in a single- and in two-electrode cascade, respectively. The signal rise time is of a few ns and the counting-rate capability approaches 10 MHz/mm^2 at 10^4 gains. Sub-mm localization precision was demonstrated with a simple, delay-line based 2D readout scheme. These multipliers may be produced in a variety of shapes and sizes and can operate in many gases. They may replace the standard GEMs in many applications requiring very large area, robust, flat, thin detectors, with good timing and counting-rate properties and modest localization. The properties of these multipliers are presented in short and possible applications are discussed.

physics.ins-det↗
arXiv2006

Amplification and Scintillation Properties of Oxygen-Rich Gas Mixtures for Optical-TPC Applications

We studied electron amplification and light emission from avalanches in oxygen-containing gas mixtures. The mixtures investigated in this work included, among others, CO2 and N2O mixed with Triethylamine (TEA) or N2. Double-Step Parallel Gap (DSPG) multipliers and THick Gas Electron Multipliers (THGEM) were investigated. High light yields were measured from CO2+N2 and CO2+TEA, though with different emission spectra. We observed the characteristic wave-length emission of N2 and of TEA and used a polymer wave-length shifter to convert TEA UV-light into the visible spectrum. The results of these measurements indicate the applicability of optical recording of ionizing tracks in a TPC target-detector designed to study the cross section of the 16O(g,a)12C reaction, a central problem in nuclear astrophysics.

physics.ins-det↗
arXiv2004

A time projection chamber with optical readout for charged particle track structure imaging

We report about a nuclear track imaging system which is designed to study in detail the ionization topology of charged particle tracks in a low-pressure gas. The detection method is based on a time projection chamber (TPC) filled with low-pressure triethylamine (TEA). Ionization electrons produced by energetic charged particles are three-dimensionally imaged by recording light from electron avalanches with an intensified CCD system. The detector permits to inves-tigate the spatial ionization distributions of particle tracks in gas, of equivalent length and resolution in tissue of 4 mm and 40 nm (RMS), respectively. We explain the relevance of this technique for dosimetry, describe the experimental method and the basic operation parameters. First results of the chamber response to protons and alpha particles are presented.

physics.ins-det↗
arXiv2004

Detectors for Time-of-Flight Fast-Neutron Radiography: 1. Neutron Counting Gas Detector

One of our two methods for fast-neutron imaging with spectrometric capability is presented here. It is a neutron-counting technique based on a hydrogenous neutron converter coupled to Gaseous Electron Multipliers (GEM). The principles of the detection techniques and the optimization of the converter, electron amplification and the readout are described. Evaluation of the properties are derived from a experiment in a pulsed neutron beam of spectral distribution between 2 and 10 MeV

physics.ins-det↗
arXiv2004

Time-resolved fast neutron imaging: simulation of detector performance

We have analyzed and compared the performance of two novel fast-neutron imaging methods with time-of-flight spectroscopy capability. Using MCNP and GEANT code simulations of neutron and charged-particle transport in the detectors, key parameters such as detection efficiency, the amount of energy deposited in the converter and the spatial resolution of both detector variants have been evaluated.

physics.ins-det↗
arXiv2004

Detectors for Energy-Resolved Fast Neutron Imaging

Two detectors for energy-resolved fast-neutron imaging in pulsed broad-energy neutron beams are presented. The first one is a neutron-counting detector based on a solid neutron converter coupled to a gaseous electron multiplier (GEM). The second is an integrating imaging technique, based on a scintillator for neutron conversion and an optical imaging system with fast framing capability.

nucl-ex↗
arXiv2003

Recent Investigations of Cascaded GEM and MHSP detectors

We present results from our recent investigations on detectors comprising cascaded gas electron multipliers (GEM) and cascaded GEMs with micro-hole and strip (MHSP) electrodes. We discuss the factors governing the operation of these fast radiation imaging detectors, that have single-charge sensitivity. The issue of ion-backflow and ion-induced secondary effects is discussed in some detail, presenting ways for its reduction and suppression. Applications are presented in the fields of photon imaging in the UV-to-visible spectral range as well as x-ray and neutron imaging.

nucl-ex↗
arXiv2003

High Resolution Heavy Ion Track Structure Imaging

The difference in the relative biological efficincy (RBE) of ions of same linear energy transfer (LET) but different atomic number (Z) can be attributed to the difference in the radial ionisation distribution. In this contribution we present data from measurements of the spatial ionisation pattern of heavy ions of various Z but similar LET and compare the results with track structure data obtained by Monte Carlo simulations. The measurements were made with a time projection chamber with optical readout (Optical Avalanche Chamber, OPAC) which is able to quantitatively capture the spatial ionisation pattern of an ion traversing the chamber

nucl-ex↗
arXiv2003

Fast Neutron Resonance Radiography in a Pulsed Neutron Beam

The feasibility of performing fast neutron resonance radiography at the PTB accelerator facility is studied. A neutron beam of a broad spectral distribution is produced by a pulsed 13 MeV deuterium beam hitting a thick Be target. The potential of 3 different neutron imaging detectors with time-of flight capability are investigated. The applied methods comprise wire chambers with hydrogenous converter layers and a fast plastic scintillator with different optical readout schemes. We present the neutron facility, the imaging methods employed and results obtained. in beam experiments where samples of carbon rods with various length and diameter were imaged to study resolution and sensitivity of the method.

nucl-ex↗