New design studies have been carried out for a readout plane for gas electron multiplier detectors using zigzag patterns that can significantly reduce the readout channel count while preserving ...excellent spatial resolution for tracking detectors. While zigzag patterns have been used in a number of applications, these studies were designed to investigate the fundamental limits of charge sharing between the electrodes to optimize the spatial resolution and minimize the nonuniformities across the readout plane, while exploring the limits of manufacturing capabilities for producing the readout board. Simulation studies were carried out to optimize the readout electrode structure, and readout boards were produced with similar zigzag designs that were tested in the laboratory using a scanning X-ray source. These studies were aimed at developing a readout board for the new time projection chamber for the sPHENIX experiment at relativistic heavy ion collider, but can readily be used in other applications, including various micropattern gas detectors, such as Micromegas.
A Hadron Blind Detector (HBD) has been developed, constructed and successfully operated within the PHENIX detector at RHIC. The HBD is a Cherenkov detector operated with pure
CF
4
. It has a 50
cm ...long radiator directly coupled in a windowless configuration to a readout element consisting of a triple GEM stack, with a CsI photocathode evaporated on the top surface of the top GEM and pad readout at the bottom of the stack. This paper gives a comprehensive account of the construction, operation and in-beam performance of the detector.
Due to their simplicity and versatility of design, straight strip or rectangular pad anode structures are frequently used with micropattern gas detectors (MPGDs) to reconstruct high-precision space ...points for various tracking applications. The particle impact point is typically determined by interpolating the charge collected by several neighboring strips. However, to effectively extract the inherent positional information, the lateral spacing of the straight strips must be comparable to or preferably smaller than the full extent of the incident charge cloud. In contrast, highly interleaved anode patterns, such as zigzags, can adequately sample the incident charge with a pitch appreciably larger than the charge cloud. This has the considerable advantage of providing the same performance while requiring far fewer instrumented channels. Additionally, the geometric parameters defining such zigzag structures may be tuned to provide a near-uniform detector response along and perpendicular to the sensitive coordinate, without the need for so-called "pad response functions," while simultaneously maintaining excellent position resolution. We have measured the position resolution of a variety of zigzag-shaped anode patterns optimized for various MPGDs, including gas electron multiplyer (GEM), Micromegas, and micro-resistive-well (<inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>RWELL) and compared this performance with the same detectors equipped with straight strips of varying pitch. We report on the performance results of each readout structure, evaluated under identical conditions in a test beam.
We have developed highly interleaved zigzag-shaped electrodes for collecting charge on the readout plane of various micropattern gaseous detectors (MPGDs), including gas electron multiplier (GEM) and ...micromega detectors. An optimized zigzag pad (or strip) anode can greatly enhance charge sharing among neighboring pads compared to traditional straight strip or rectangular pad designs and as a result can deliver excellent position resolution with minimal channel count, while exhibiting a virtually uniform response across the detector. We have systematically studied the effects of varying the parameters that define the zigzag geometry using simulations and have measured several printed circuit boards (PCBs) comprising a range of zigzag designs. Recently, we have employed laser ablation to generate zigzag patterns with pad-to-pad gaps smaller than 1 mil (or 25 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula>). Reducing the gap well below the 3-mil limit imposed by traditional chemical etching has allowed the production of zigzag electrodes with unprecedentedly small feature sizes. In turn, laser-etched zigzag PCBs were shown to exhibit markedly improved performance over earlier generation PCBs, with position resolutions below 50 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> for a 2-mm pitch. This article will explore in detail the dependence of the position resolution on the structural parameters of a zigzag-shaped anode, specifically for the case of a quadruple GEM detector.
A combined time projection chamber-Cherenkov (TPCC) prototype detector has been developed as part of the detector research and development program for a future electron-ion collider (EIC). The ...prototype was tested at the Fermilab test beam facility (FTBF) to provide a proof of the principle to demonstrate the ability to measure particle tracks and provide particle identification (PID) information within a common detector volume. The time projection chamber (TPC) portion consists of a <inline-formula> <tex-math notation="LaTeX">10 \times 10 \times 10 </tex-math></inline-formula> cm 3 field cage, which delivers charge from tracks to a quadruple gas electron multiplier (GEM) with zigzag-shaped charge collection anodes. The Cherenkov portion consists of a photosensitive quadruple GEM detector with a CsI photocathode. As tracks pass through the drift volume of the TPC, the generated Cherenkov light is able to escape through sparsely arranged wires making up one side of the field cage, facing the CsI photocathode. The Cherenkov detector is thus operated in a windowless, proximity focused configuration for high efficiency. Pure CF 4 is used as the working gas for both detector components, mainly due to its transparency into the deep UV, as well as its high N 0 . Results from the beam test, including the position resolution as well as the particle id capabilities of the detector, are discussed in this paper.
A GEM tracking detector with an extended drift region has been studied as part of an effort to develop new tracking detectors for future experiments at RHIC and for the Electron Ion Collider that is ...being planned for BNL or JLAB. The detector consists of a triple GEM stack with a 1.6 cm drift region that was operated in a mini TPC type configuration. Both the position and arrival time of the charge deposited in the drift region were measured on the readout plane which allowed the reconstruction of a short vector for the track traversing the chamber. The resulting position and angle information from the vector could then be used to improve the position resolution of the detector for larger angle tracks, which deteriorates rapidly with increasing angle for conventional GEM tracking detectors using only charge centroid information. Two types of readout planes were studied. One was a COMPASS style readout plane with 400 μm pitch XY strips and the other consisted of 2 × 10 mm 2 chevron pads. The detector was studied in test beams at Fermilab and CERN, along with additional measurements in the lab, in order to determine its position and angular resolution for incident track angles up to 45 degrees. Several algorithms were studied for reconstructing the vector using the position and timing information in order to optimize the position and angular resolution of the detector for the different readout planes. Applications for large angle tracking detectors at RHIC and EIC are also discussed.
A hadron blind detector for the PHENIX experiment at RHIC Fraenkel, Z.; Kozlov, A.; Naglis, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2005, Letnik:
546, Številka:
3
Journal Article
Recenzirano
Odprti dostop
A Hadron Blind Detector (HBD) is being developed for the PHENIX experiment at RHIC. It consists of a Cherenkov radiator operated with pure
CF
4
directly coupled in a windowless configuration to a ...triple-GEM detector element with a CsI photocathode and pad readout. The HBD operates in the bandwidth 6–11.5
eV (110–200
nm). We studied the detector response to minimum ionizing particles and to electrons. We present measurements of the CsI quantum efficiency, which are in very good agreement with previously published results over the bandwidth 6–8.3
eV and extend them up to 10.3
eV. Discharge probability and aging studies of the GEMs and the CsI photocathode in pure
CF
4
are presented.
Positron Emission Tomography is a powerful imaging technique used for humans and animals that can also be used to study plant biology. However, since many of the structures found on plants (e.g., ...leaves) are very thin, a large portion of the positrons emitted from PET isotopes escape before annihilation, leading to low efficiency and quantification inaccuracies. In this study, a gas tracking detector was used to measure escaping positrons from PET radiotracer isotopes which has the ability to reconstruct three dimensional tracks that can be used to form an image of the emitting object. This device uses a triple GEM detector with a short drift region and an XY strip readout plane to measure a vector for positrons passing through a drift gap. By projecting each particle track back to the object surface, a 2-D image of the spatial distribution of the positrons that escaped from that surface can be reconstructed. In this paper, we will describe the basic principle of the GEM detector and present results on its performance using various types of phantoms and actual plant specimens. Monte Carlo simulations are also used to better understand the detector performance and compare to actual measurements.
A study has been made of the parameters affecting the extraction and collection of photoelectrons from the surface of a CsI photocathode in a triple GEM detector. The purpose of this study was to ...optimize the photoelectron collection efficiency and GEM operating conditions for the PHENIX Hadron Blind Detector (HBD) at RHIC. The parameters investigated include the electric field at the surface of the photocathode, the voltage across the GEM, the electric field below the GEM, the medium into which the photoelectrons are extracted (gas or vacuum), and the wavelength dependence of the extraction efficiency. A small, calibrated light source, or ldquoscintillation cuberdquo was used to illuminate a GEM CsI photocathode with a known photon flux produced by the scintillation light from 5.48 MeV alpha particles in CF 4 . The photoelectron collection efficiency was calculated by comparing the number of photoelectrons produced to the number collected at the GEM readout pad. Results are presented on the study of the parameters affecting the photoelectron collection efficiency and the construction and calibration of the scintillation cube.
The planned tracking upgrade of the STAR experiment at RHIC includes a large-area GEM tracker used to determine the charge sign of electrons and positrons produced from W +(-) decays. For such a ...large-scale project commercial availability of GEM foils is necessary. We report first results obtained with a triple GEM detector using GEM foils produced by Tech-Etch Inc. of Plymouth, MA. Measurements of gain uniformity, long-term stability as well as measurements of the energy resolution for X-rays are compared to results obtained with an identical detector using GEM foils produced at CERN. A quality assurance procedure based on optical tests using an automated high-resolution scanner has been established, allowing a study of the correlation of the observed behavior of the detector and the geometrical properties of the GEM foils. Detectors based on Tech-Etch and CERN produced foils both show good uniformity of the gain over the active area and stable gain after an initial charge-up period, making them well suited for precision tracking applications.
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