Further progress in ion back-flow reduction with patterned gaseous hole-multipliers

A new idea on electrostatic deviation and capture of back-drifting avalanche-ions in cascaded gaseous hole-multipliers is presented. It involves a flipped reversed-bias Micro-Hole & Strip Plate (F-R-MHSP) element, the strips of which are facing the drift region of the multiplier. The ions, originating from successive multiplication stages, are efficiently deviated and captured by such electrode. Experimental results are provided comparing the ion-blocking capability of the F-R-MHSP to that of the reversed-bias Micro-Hole & Strip Plate (R-MHSP) and the Gas Electron Multiplier (GEM). Best ion-blocking results in cascaded hole-multipliers were reached with a detector having the F-R-MHSP as the first multiplication element. A three-element F-R-MHSP/GEM/MHSP cascaded multiplier operated in atmospheric-pressure Ar/CH4 (95/5), at total gain of ~10^{5}, yielded ion back-flow fractions of 3*10^{-4} and 1.5*10^{-4}, at drift fields of 0.5 and 0.2 kV/cm, respectively. We describe the F-R-MHSP concept and the relevance of the obtained ion back-flow fractions to various applications; further ideas are also discussed.Comment: 17 pages, 11 figures, published in JINS

A Comparative Numerical Study on GEM, MHSP and MSGC

In this work, we have tried to develop a detailed understanding of the physical processes occurring in those variants of Micro Pattern Gas Detectors (MPGDs) that share micro hole and micro strip geometry, like GEM, MHSP and MSGC etc. Some of the important and fundamental characteristics of these detectors such as gain, transparency, efficiency and their operational dependence on different device parameters have been estimated following detailed numerical simulation of the detector dynamics. We have used a relatively new simulation framework developed especially for the MPGDs that combines packages such as GARFIELD, neBEM, MAGBOLTZ and HEED. The results compare closely with the available experimental data. This suggests the efficacy of the framework to model the intricacies of these micro-structured detectors in addition to providing insight into their inherent complex dynamical processes

Simulation of VUV electroluminescence in micropattern gaseous detectors: the case of GEM and MHSP

Electroluminescence produced during avalanche development in gaseous avalanche detectors is an useful information for triggering, calorimetry and tracking in gaseous detectors. Noble gases present high electroluminescence yields, emitting mainly in the VUV region. The photons can provide signal readout if appropriate photosensors are used. Micropattern gaseous detectors are good candidates for signal amplification in high background and/or low rate experiments due to their high electroluminescence yields and radiopurity. In this work, the VUV light responses of the Gas Electron Multiplier and of the Micro-Hole Strip Plate, working with pure xenon, are simulated and studied in detail using a new and versatile C++ toolkit. It is shown that the solid angle subtended by a photosensor placed below the microstructures depends on the operating conditions. The obtained absolute EL yields, determined for different gas pressures and as functions of the applied voltage, are compared with those determined experimentally.Comment: Accepted for publication in Journal of Instrumentatio

MHSP in reversed-biased operation mode for ion blocking in gas-avalanche multipliers

We present recent results on the operation of gas-avalanche detectors comprising a cascade of gas electron multipliers (GEMs) and Micro-Hole and Strip Plates (MHSPs) multiplier operated in reversed-bias (R-MHSP) mode. The operation mechanism of the R-MHSP is explained and its potential contribution to ion-backflow (IBF) reduction is demonstrated. IBF values of 4E-3 were obtained in cascaded R-MHSP and GEM multipliers at gains of about 1E+4, though at the expense of reduced effective gain in the first R- MHSP multiplier in the cascade.Comment: 23 pages, 8 figure

Kesan latihan dalam perkhidmatan ke atas kualiti pengajaran dam pembelajran dalam bidang teknik dan vokasional

Kajian ini bertujuan untuk mengenalpasti keberkesanan latihan dalam perkhidmatan yang dihadiri oleh guru-guru teknik dan vokasional dan sejauh mana hubungannya dengan keberkesanan pengajaran mereka dan pencapaian pelajar. Kajian ini merupakan kajian kuantitatif yang turut disokong dengan maklumat daripada data kualitatif. Maklumat dikumpulkan melalui dua set soal selidik, set A dan set B. Set A diberikan kepada 43 orang guru sekolah menengah teknik (SMT) di Kluang, Batu Pahat, Muar, Segamat dan Pontian, Johor. Kajian ini mempertimbangkan empat mata pelajaran elektif utama bagi pelajar-pelajar aliran teknikal iaitu Pengajian Kejuruteraan Awam (PKA), Pengajian Kejuruteraan Mekanikal (PKM), Pengajian Kejuruteraan Elektrik (PKE) dan Lukisan Kejuruteraan (LK). Antara maklumat yang diperolehi adalah latar belakang responden, keberkesanan latihan yang diikuti dan juga keberkesanan pengajaran guru. Manakala soal selidik set B pula diedarkan kepada 1225 orang pelajar yang diajar oleh guru-guru di atas. Maklumat mengenai keberkesanan guru-guru teknik dan vokasional pada pandangan pelajar diperoleh melalui soal selidik ini. Kaedah temu bual telah dilakukan ke atas Penolong-penolong Kanan SMT untuk mendapatkan maklumat umum daripada pihak pengurusan yang boleh membantu kajian. Di samping itu, data markah peperiksaan pelajar juga diambil dan dianalisis. Semua data telah dianalisis menggunakan pakej SPSS versi 12. Antara analisis yang dilakukan adalah taburan kekerapan bagi data latar belakang responden, nilai purata bagi data latihan dalam perkhidmatan dan guru berkesan, ujian-? untuk mengkaji perbezaan pencapaian pelajar yang diajar oleh guru yang mengikuti latihan dan tiada latihan dalam perkhidmatan dan pekali korelasi Pearson bagi mengkaji hubungan antara latihan dalam perkhidmatan dengan keberkesanan pengajaran guru dan pencapaian pelajar. Kajian membuktikan bahawa latihan dalam perkhidmatan yang dihadiri oleh guru SMT mempunyai tahap keberkesanan yang tinggi. Latihan dalam perkhidmatan yang menitikberatkan kemahiran guru menjadi ciri utama yang dipersetujui oleh para guru di SMT. Namun begitu, ada juga aktiviti-aktiviti pembangunan staf bagi guru-guru teknikal yang dilaksanakan secara kurang berkesan dari segi tempoh yang tidak mencukupi dan perlaksanaan yang tidak berterusan. Kajian juga membuktikan bahawa guru-guru SMT mempunyai kecekapan profesion yang tinggi dari segi kemahiran dan ilmu pengetahuan tetapi tahap keberkesanan sederhana dari segi hubungan interpersonal dan kemahiran kaunseling. Kajian mendapati terdapat hubungan yang signifikan di antara latihan dalam perkhidmatan dengan keberkesanan pengajaran guru, keberkesanan pengajaran guru dengan pencapaian pelajar dan juga antara latihan dalam perkhidmatan dengan pencapaian pelajar

Advances in the Micro-Hole & Strip Plate gaseous detector

We report on the performance of a new gaseous electron multiplier: the Micro-Hole & Strip Plate (MHSP). It consists of two independent charge-amplification stages in a single, double-sided micro-structured electrode, deposited on a thin insulating substrate. Charge gains in excess of 103 were obtained in a MHSP operated with soft X-rays in Ar/CO2 (70/30). We present the results of a systematic study of the MHSP properties and those of a double-stage GEM+MHSP multiplier. Applications to gaseous photomultipliers are discussed.http://www.sciencedirect.com/science/article/B6TJM-48GF7W8-1/1/9ca82a7819a2c55a59c29ed0a8803a9

Recent advances in X-ray detection with micro-hole and strip plate detector

We report on the performance of a micro-hole and strip plate, fabricated with standard gas electron multiplier-production procedures, presenting 40-[mu]m hole-diameter and 30-[mu]m wide anode strips. Multiplication factors of 5×104 were reached in an Ar/Xe (95/5) atmosphere at about 1 bar; the energy resolution is of the order of 14% (FWHM) for 5.9-keV X-rays.http://www.sciencedirect.com/science/article/B6TJM-4BRJY00-1/1/d80a918485bf806c1feae6bbd514d4e

Periodic nano/micro-hole array silicon solar cell

In this study, we applied a metal catalyst etching method to fabricate a nano/microhole array on a Si substrate for application in solar cells. In addition, the surface of an undesigned area was etched because of the attachment of metal nanoparticles that is dissociated in a solution. The nano/microhole array exhibited low specular reflectance (<1%) without antireflection coating because of its rough surface. The solar spectrum related total reflection was approximately 9%. A fabricated solar cell with a 40-μm hole spacing exhibited an efficiency of 9.02%. Comparing to the solar cell made by polished Si, the external quantum efficiency for solar cell with 30 s etching time was increased by 16.7%

Micro-Hole and Strip Plate (MHSP) operation in CF4

The Micro-Hole and Strip Plate (MHSP) is a hybrid electron multiplier which combines the working principles of a Gas Electron Multiplier (GEM) and a Micro-Strip Gas Counter (MSGC). The compact double stage electron multiplication processes found in the MHSP enables the realisation of higher gas gain than the lone GEM operation. Thermal neutron detection using gas detectors involves the use of gas with another suitable stopping gas, operated at elevated pressure to confine the products of the neutron- reaction. It is, however, well known that the gain of GEMs drops too sharply with increasing chamber pressure.http://www.sciencedirect.com/science/article/B6TJM-4NS2G9V-D/1/497af6476b376b1c2f407a3fa7ff735