ICFA Instrumentation Bulletin

The publication of the ICFA Instrumentation Bulletin is an activity of the Panel on Future Innovation and Development of ICFA (International Committee for Future Accelerators).

The illustration depicts L. J. Waghenaer's marine atlas

The illustration depicts L. J. Waghenaer's marine atlas, "The Mariner's mirror", published in 1588. Lucas Janszoon Waghenaer> was born in Holland in the 1530s. He became a famous ship pilot of his time. In 1584 he published the atlas ("Spieghel der Zeevaerdt"), which was greatly valued among mariners for centuries. This was not only because of its map content, but also because of a detailed knowledge of navigation techniques of that time. When it was translated from Dutch to English, the atlas appeared with a title page we are using on our home page.

ICFA Instrumentation Bulletin Issues

Volume 27, Spring 2005

D. Allspach, D. Ambrose, M. Binkley, C. Bromberg, K. Burkett, R. Kephart, R. Madrak, T. Miao, A. Mukherjee, R. Roser, R.L. Wagner

Aging in the Large CDF Axial Drift Chamber

The Central Outer Tracker (COT) is a large axial drift chamber in the Collider Detector at Fermilab operating with a gas mixture that is 50/50 argon/ethane with an admixture of 1.7% isopropanol. In its first two years of operation the COT showed unexpected aging with the worst parts of the chamber experiencing a gain loss of ~50% for an accumulated charge of ~35 mC/cm. By monitoring the pulse height of hits on good tracks, it was possible to determine the gain as a function of time and location in the chamber. In addition, the currents of the high voltage supplies gave another monitor of chamber gain and its dependence on the charge deposition rate. The aging was worse on the exhaust end of the chamber consistent with polymer buildup as the gas flows through the chamber. The distribution in azimuth suggests that aging is enhanced at lower temperatures, but other factors such as gas flow patterns may be involved. Elemental and molecular analysis of the sense wires found a coating that is mostly carbon and hydrogen with a small amount of oxygen; no silicon or other contaminants were identified. High resolution electron microscope pictures of the wire surface show that the coating is smooth with small sub-micron nodules. In the course of working with the chamber gas system, we discovered a small amount of O2 is enough to reverse the aging. Operating the chamber with ~100 ppm of O2 reversed almost two years of gain loss in less than 10 days while accumulating <= 2 mC/cm. 

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R. Bellazzini and G. Spandre

Gas Pixel Detectors

We present a new class of Micro Pattern Gas Detectors in which a complete integration between the gas amplification structure and a pixelized read-out electronics has been reached. We call this device the Gas Pixel Detector (GPD). For this purpose we have developed and built two generations of an Application-Specific Integrated Circuit (ASIC) in deep sub-micron VLSI technology. The CMOS chip has the top metal layer patterned in a matrix of 80痠 pitch hexagonal pixels used as charge collecting pads and directly connected to the underneath electronics chain which has been realized using the remaining five layers of the 0.35痠 VLSI technology. In this way gas detectors performances approach solid state device standards in terms of spatial resolution (~30痠) and rate capibility (a few MHz/mm2). Results from tests on a first prototype of such detector with 2k pixels and on its further implementation to 22k pixels are presented. An application of this device for Astronomical X-Ray Polarimetry is discussed.

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Volume 26, Spring 2004

A. Boyarski

Model of high current breakdown from cathode field emission in aged wire chambers

Observing single electron pulses provides insight into the mechanism that leads to sudden high current jumps (breakdown) in aged wire chambers. This single electron activity is found to be consistent with the Fowler-Nordheim equation for field emission of electrons from a cathode surface in a high electric field. The high electric field arises from the positive ion buildup on a very thin insulating layer on the cathode surface. A model is presented to explain the transient behavior of single electron pulses in response to abrupt changes in chamber ionization, as well as the steady state rate during a long term aging run. The model is based on properties of the insulating layer (dielectric constant, conductivity, and hole-mobility) as well as the Fowler-Nordheim equation.

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M. Titov

Radiation Damage and Long-Term Aging in Gas Detectors

Aging phenomena constitute one of the most complex and serious potential problems which could limit, or severely impair, the use of gaseous detectors in unprecedented harsh radiation environments. Long-term operation in high-intensity experiments of the LHC-era not only demands extraordinary radiation hardness of construction materials and gas mixtures but also very specific and appropriate assembly procedures and quality checks during detector construction and testing. Recent experimental data from hadron beams is discussed. It is shown that the initial stage of radiation tests, usually performed under isolated laboratory conditions, may not offer the full information needed to extrapolate to the long-term performance of real and full-size detectors at high energy physics facilities. Major factors, closely related to the capability of operating at large localized ionization densities, and which could lead to operation instabilities and subsequent aging phenomena in gaseous detectors, are summarized. Finally, an overview of aging experience with state-of-the-art gas detectors in experiments with low- and high-intensity radiation environments is given with a goal of providing a set of rules, along with some caveat, for the construction and operation of gaseous detectors in high luminosity experiments.

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L. Latronico

MicroPattern Gas Detectors with Pixel Read-Out

MicroPattern Gas Detectors with pixel read-out are position-sensitive proportional counters obtained by coupling a gas amplifying stage, provided by a GEM detector, to a charge collection plane patterned with pixel electrodes. Advanced PCB techniques, offering typical feature size of the order of a few microns, are used to construct both stages of these detectors, which show high detection efficiency, excellent spatial resolution and fast charge collection. In this paper it is shown how the design of the read-out system can maximize the intrinsic performance of these devices for two practical implementations, in the field of X-Ray Astronomy and Plasma Imaging.

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Volume 25, Fall 2002

Priscilla B. Cushman and Adriaan H. Heering

CMS HCAL Hybrid Photodiode Design and Quality Assurance Stations

The hadronic calorimeter for the CMS experiment requires photodetection in a 4 Tesla magnetic field. This, plus high neutron radiation and a 25 ns bunch-crossing, necessitated the development of a new type of high-rate multi-channel hybrid photodiode. As our specifications became tighter, design changes in the diode structure and surface treatment became necessary, resulting in a better product with very low crosstalk in both AC and DC modes. The specifications are rigorous and are maintained by a set of automated Quality Assurance stations which will process 570 tubes over 2 years.

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G. D. Hallewell

Technology Developments for Deep Underwater Neutrino Telescopes

The July-2002 report of the High Energy Neutrino Astrophysics Panel (HENAP) recommended the construction of a km3-scale Northern hemisphere neutrino observatory to complement a large-scale under-ice observatory (IceCube) in the Southern hemisphere. Such an observatory would study cosmic neutrinos with energies in excess of a few hundred GeV, which arrive undeviated from a variety of galactic and extragalactic sources of astrophysical interest, and which might be produced in the possible annihilation of dark matter particles, including neutralinos. Future developments in technology from that being presently implemented by the Lake Baikal, Nestor, and Antares collaborations toward that necessary for a much larger km3-scale array are discussed. In January 2000, a part of the Nemo collaboration, engaged in studies for a km3 scale detector close to the Sicilian coast, joined Antares in the development of a 0.1km2 detector. The two collaborations have formed a common working group to coordinate the effort toward the construction of a km3-scale detector. The great depth presents numerous technical challenges in the construction, deployment and interconnection of such detectors, and may require the involvement of industrial contractors with experience in fields including deep-sea oil exploitation, submarine telecommunications cable deployment, underwater acoustic navigation and communication, and in the operation of manned or remotely-operated submarine vehicles. This paper reviews the status of some of the technologies for underwater neutrino detector arrays.

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Volume 24, Spring 2002

J. Va'vra

Physics and Chemistry of Aging - Early Developments

The aging phenomena are very complex physical and chemical processes. The author attempts to qualitatively discuss various physical processes contributing to aging. The satisfactory quantitative explanation is not presently available. In this sense, there is little progress made since the 1986 LBL Aging Workshop. However, what was accomplished during the past decade is a heighten awareness from the research and management sides to pay more attention to this problem, and as a result a number of aging tests have increased in quantity and quality. These efforts will undoubtedly yield some new results in the future. Examples in this paper are mainly from a pre-LHC and pre-HERA-B era of aging, where the total charge doses is limited to much less than one C/cm.

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M. Titov, M. Hohlmann, C. Padilla, N. Tesch

Summary and Outlook of the International Workshop on Aging Phenomena in Gaseous Detectors (DESY, Hamburg, October, 2001)

High Energy Physics experiments are currently entering a new era which requires the operation of gaseous particle detectors at unprecedented high rates and integrated particle fluxes. Full functionality of such detectors over the lifetime of an experiment in a harsh radiation environment is of prime concern to the involved experimenters. New classes of gaseous detectors such as large-scale straw-type detectors, Micro-pattern Gas Detectors and related detector types with their own specific aging effects have evolved since the first workshop on wire chamber aging was held at LBL, Berkeley in 1986. In light of these developments and as detector aging is a notoriously complex field, the goal of the workshop was to provide a forum for interested experimentalists to review the progress in understanding of aging effects and to exchange recent experiences. A brief summary of the main results and experiences reported at the 2001 workshop is presented, with the goal of providing a systematic review of aging effects in state-of-the-art and future gaseous detectors. 

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Y. Bagaturia, et al.

Studies of aging and HV break down problems during development and operation of MSGC and GEM detectors for the Inner Tracking System of HERA-B

The results of five years of development of the inner tracking system of the HERA- B experiment and first experience from the data taking period of the year 2000 are reported. The system contains 184 chambers, covering a sensitive area of about (20* 20) cm2 each. The detector is based on microstrip gas counters (MSGCs) with diamond like coated (DLC) glass wafers and gas electron multipliers (GEMs).

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M. Capeans

Aging of Gaseous Detectors: assembly materials and procedures

Aging of gaseous detectors is known as the degradation of their performance under the exposure to ionizing radiation. It is a complex phenomenon that depends on many parameters. Among others, aging depends on the gas mixture and may be enhanced by the presence of pollutants in the gas. The origin of the impurities is diverse and includes outgassing from assembly materials and the gas system components, and contamination of the detector during the assembly process. Systematic studies on this topic have been carried out. Methods used to ascertain the outgassing properties of materials are described and compared. Materials that might be used for assembling gaseous detectors and associated gas systems are catalogued according to their outgassing rate. Some factors affecting the aging rate in some fast gases are presented. Finally, a set of recommendations to build and operate gaseous detectors in high luminosity experiments is given.

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Volume 23, Fall 2001

A. Blanco, R. Ferreira-Marques, Ch. Finck, P. Fonte, A. Gobbi, A. Policarpo, M. Rozas

A Large Area Timing RPC

A large area Resistive Plate Chamber (RPC) with a total active surface of 160*10 cm2 was built and tested. The surface was segmented in two 5 cm wide strips readout on both ends with custom, very high frequency, front end electronics. A timing resolution s = 50-75 ps with an efficiency for Minimum Ionizing Particles (MIPs) larger than 95% was attained over the whole active area, in addition with a position resolution along the strips of 1.2 cm. Despite the large active area per electronic channel, the observed timing resolution is remarkably close to the one previously obtained (s = 50 ps) with much smaller chambers of about 10 cm2 area. These results open perspectives of extending the application of timing RPCs to large area arrays exposed to moderate particle multiplicities, where the low cost, good time resolution, insensitivity to the magnetic field and compact mechanics may be attractive when compared with the standard scintillator-based Time-of-Flight (TOF) technology.

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P. Fonte

Applications and new developments in Resistive Plate Chambers

Resistive Plate Chambers are rugged and affordable gas detectors that have found extensive use in High Energy Physics and Astroparticle experiments. The main features of these counters are the very large pulse height, reduced cost per unit area and good (about 1ns) time resolution. The field has enjoyed very lively progress in recent years, including the introduction of a new (avalanche) mode of operation, extension of the counting rate capabilities to levels around 10MHz/cm2, improvement of the time resolution for MIPs to 50 ps sigma and the achievement of position resolutions of a few tens of micrometer. These new developments have extended the range of HEP applications and promise new applications in medical imaging.

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P. Buzhan, B. Dolgoshein, A. Ilyin, V. Kantserov, V. Kaplin, A. Karakash, A. Pleshko, E. Popova, S. Smirnov, Yu. Volkov, L. Filatov, S. Klemin, F. Kayumov

The Advanced Study of Silicon Photomultiplier

The advanced study of new photo detector - Silicon Photomultiplier (SiPM) is presented. SiPM consists of many (~103 mm-2) silicon micro pixels, which are independent photon micro counters working in limited Geiger mode with a gain of 106. The SiPM output signal is a sum of the signals from a number of pixels fired by photons. The main features of SiPM are: low excess noise factor, the photon detection efficiency at the level of vacuum PMT, low bias voltage (~24V). The timing of the SiPM is about 30 ps for 10 photoelectrons. The possibilities of SiPM applications based on experimental tests are demonstrated: sci fiber readout, scintillator-shifter system readout, possible application for hadron calorimeters.

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Volume 22, Spring 2001

A. Sharma

Gaseous Micropattern Detectors: High Energy Physics and Beyond

Multiwire gaseous detectors have matured in the last few decades with major implications in particle physics experiments. They have also been successfully refined for use in other fields: X-rays for medical imaging, UV and single photon detection, neutron and crystal diffraction studies etc. Their major limitation has been a modest rate capability (103/mm2). In the last decade several micropattern position sensitive gas devices have been introduced with an inherently improved rate capability (few MHz/mm2) and a localization accuracy of 40-50 µm. They are being extensively pursued for their application in several fields. The state of the art of this new generation of gaseous detectors will be reviewed. 

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B. N. Ratcliff

DIRC Dreams Redux: Research Directions for the Next Generation of Internally Reflected Imaging Counters

Some general conceptual design features of total internally reflecting, imaging Cherenkov counters (DIRCs) are described. Limits of the DIRC approach to particle identification and a few features of alternative DIRC designs are briefly explored. 

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P. Bourgeois and J. Va'vra

Corrosion of Glass Windows in DIRC PMTs

The DIRC photon detector contains ~11,000 photomultipliers (PMTs), which are submerged in ultra-pure water. This note reports on glass corrosion R&D conducted with PMTs in pure water. We conclude that only limited number (~50) of the PMTs in water are affected by rapid corrosion, while a majority of the 11,000 PMTs should last, according to our measurements, for another ten years. The observation of PMT glass corrosion is based on visual observations, X-ray surface analysis, ESCA surface analysis, weight analysis, transmission measurement, as well as detailed water trace element analysis. We also correlate these observations with DIRC measurements of water pH factor, resistivity, temperature, transmission, and BaBar analysis of Bhabha and di-muon events. We also compare DIRC water purity with that of the Super Kamiokande and K2K experiments, which also use ultra-pure water. We provide empirical proof that corrosion, in our particular Borosilicate type of PMT glass window, occurs at high rate when the glass has no Zn content.

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Volume 21, Fall 2000

Richard Wigmans

Thin Calorimetry for Cosmic-Ray Studies Outside the Earth's Atmosphere

Cosmic ray experiments outside the Earth's atmosphere are subject to severe restrictions on the mass of the instruments. Therefore, it is important that the experimental information that can be obtained per unit detector mass is maximized. In this paper, tests are described of a thin (1.4 lambda_int deep) hadron calorimeter that was designed with this goal in mind. This detector was equipped with two independent active media, which provided complementary information on the showering hadrons. It is shown that by combining the information from these media it was possible to reduce the effects of the dominant leakage fluctuations on the calorimeter performance. 

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E. Aprile et al.

Spectroscopy and Imaging Performance of the Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT)

LXeGRIT is a balloon-borne Compton telescope based on a liquid xenon time projection chamber (LXeTPC) for imaging cosmic gamma-rays in the energy band of 0.2- 20 MeV. The detector, with 400~cm2 area and 7 cm drift gap, is filled with high purity LXe. Both ionization and scintillation light signals are detected to measure the energy deposits and the three spatial coordinates of individual gamma -ray interactions within the sensitive volume. The TPC has been characterized with repeated measurements of its spectral and Compton imaging response to gamma -rays from radioactive sources such as Na, Cs, Y and Am-Be. The detector shows a linear response to gamma -rays in the energy range 511 keV -4.4 MeV, with an energy resolution (FWHM) of Delta E/E=8.8% : sqrt(1MeV /E). Compton imaging of Y gamma -ray events with two detected interactions is consistent with an angular resolution of ~ 3 degrees (RMS) at 1.8 MeV.

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J. Cohen-Tanugi, M. Convery, B. Ratcliff, X. Sarazin, J. Schwiening, and J. Va'vra

Optical Properties of the DIRC Fused Silica Cherenkov Radiator

The DIRC detector is successfully operating as the hadronic particle identification system for the BaBar experiment at SLAC. The production of its Cherenkov radiator required much effort in practice, both in manufacture and conception, which in turn required a large number of R&D measurements. One of the major outcomes of this R&D work was an understanding of methods to select radiation hard and optically uniform fused silica material. Others included measurement of the wavelength dependency of the internal reflection coefficient, and its sensitivity to the surface pollution, selection of the radiator support, selection of good optical glue, etc. This note summarizes the optical R&D test results.

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Volume 20, Spring 2000

G. Hall

Front End Electronics Developments for Particle Physics: Paradigm or Paradox?

Recent years have seen much dedicated work on front end electronics for hadron colliders, with an strong emphasis on radiation hardness and low cost. This has been challenging for a number of reasons, some of which are discussed further below. The developments also suggest opportunities and constraints for the development of such electronics in proton beam.

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Takayoshi Ohshima

Time-Of-Propagation Counter - A New Cherenkov Ring Imaging Detector

A new particle identification detector based on measurements of both Time-of-Propagation (TOP) and horizontal emission angle of Cherenkov photons is proposed here. Some R&D results are also reported. 

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P. Rehak, G.C. Smith, J.B. Warren and B. Yu

MIPA: A new Micro-Pattern Detector

An anode-cathode array is being developed for electron multiplication in gas that lends itself to easy fabrication with lithographic techniques. Comprising an assembly of anode pins that are recessed into a closely-packed hexagonal cathode, the MIcro-Pin Array (MIPA) represents a promising addition to micro-pattern detectors with two-dimensional sensitivity. We describe the electrostatic rationale behind the MIPA detector's design, the fabrication technique, and X-ray results that illustrate electrical stability and high rate capability.

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Volume 19, Fall 1999

I. Giomataris

MICROMEGAS: results and prospects

A lot of effort has been invested in the development of the Microstrip Gas Chamber (MSGC) in order to be used as tracker for the LHC project. This technique allows good localization accuracy and double track resolution. However, it is necessary to operate it with a relatively low gas gain because of the presence of the insulator near the amplification region and because of the fragility of the structure. Recently a new preamplification structure, called GEM has been introduced which can give an additional gas gain, and compensates the lack of gain of the original MSGC. Other concepts of novel proportional counters have been proposed recently: CAT, MICRO-DOT. A review of recently developed gaseous detectors can be found in reference. MICROMEGAS is a high gain gaseous detector, which can stand up alone without a need of an additional preamplification. It combines high accuracy, high rate capability, excellent timing properties and robustness. These results were confirmed by a similar structure having wider amplification gap and thicker metallic grid.

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Archana Sharma

A How-to Approach for a 3d Simulation of Charge Transfer Characteristics in a Gas Electron Multiplier (GEM)

In this paper a detailed description of how to simulate charge transfer processes in a gaseous device is presented, taking the Gas Electron Multiplier (GEM) as an example. A 3-dimensional simulation of the electric field and avalanche is performed. Results on charge transport are compared to experiment and agree within experimental errors; avalanche mechanism and positive ion feedback are studied. The procedures used in the simulation are described in detail, and program scripts are appended.

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P. Krizan

Detection of photons in the HERA-B RICH

The tests carried out with the photon detector of the ring imaging Cherenkov detector for the HERA-B experiment are reviewed. Results of on-the-bench tests of the employed photomultiplier tubes are reported together with early commissioning measurements with the HERA proton beam.

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Volume 18, Spring 1999

T. Sumiyoshi

Production of a New Generation of Silica Aerogel and its Application for the KEK B-factory Experiment

Low-refractive index silica aerogel is the most convenient radiator for threshold-type Cherenkov counters, which is used for particle identification in high-energy physics experiments. For the BELLE detector at the KEK B-Factory, we have produced about 2 m3 of hydrophobic silica aerogels of n = 1.01 - 1.03 using a new production method. The particle identification capability of the aerogel Cherenkov counters was tested and 3 sigma pion/proton separation has been achieved at 3.5 GeV/c. Radiation hardness of the aerogels was confirmed up to 9.8 Mrad. Thanks to the improved transparency, aerogels prepared by the two-step method can be used as radiators for not only threshold-type, but also for Ring Imaging-type Cherenkov counters. The newly developed aerogels will be used extensively for particle identification devices in future high-energy physics experiments.

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P. Fonte, A. Smirnitski, and C. Williams

A New High-Resolution Time-OF-Flight Technology

In the framework of the ALICE Collaboration, we have recently studied the performance of the multigap Resistive Plate Chambers, which were operated in avalanche mode and at atmospheric pressure for Time-Of-Flight measurements. The detector provided an overall (detector plus electronics) timing accuracy of 120 ps sigma at an efficiency of 98% for MIP's. The chambers had four 0.3mm gas gaps, limited by both a metallised ceramic plate and a glass plate, with an active dimension of 4x4cm2. The gas mixture contained C2H2F4 +5%isobutane+10%SF6 . The streamer discharges, at a rate level of a few percent, each releasing about 20pC, were tolerated without any noticeable problem. This detector opens the perspectives for affordable and reliable, high-granularity large area TOF detectors, with efficiency and time resolution comparable to existing scintillator-based TOF technology, but with significantly, up to an order of magnitude, a lower price per channel.

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A. Braem, E. Chesi, F. Filthaut, A. Go, C. Joram, P. Weilhammer, P. Wicht, W. Dulinski, J. Seguinot, H. Wenzel, T. Ypsilantis

Highly Segmented Large-Area Hybrid Photodiodes with Bialkali Photocathodes and Enclosed VLSI Readout Electronics

We report on the principles, design, fabrication, and operation of a highly segmented, large-area hybrid photodiode, which is being developed in the framework of the LHCb RICH project. The device consists of a cylindrical, 127mm diameter vacuum envelope capped with a spherical borosilicate UV-glass entrance window, with an active-to-total-area fraction of 81%. A fountain-focusing electron optics is used to demagnify the image onto a 50mm diameter silicon sensor, containing 2048 pads of size 1 * 1mm2. The sensor pads are read out by 16 analogue multiplexed readout chips enclosed in the vacuum envelope. A large ultra-high vacuum plant for the evaporation of visible-light transmittive bialkali (K2CsSb) photocathodes and subsequent tube encapsulation has been built and successfully operated. The characteristics and performance of the first HPDs have been measured to be in full agreement with expectations.

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Volume 17, Fall 1998

A.Bressan, A.Buzulutskov, L.Ropelewski, F.Sauli, L.Shekhtman

High gain operation of GEM in pure argon

We study the operation of the Gas Electron Multiplier (GEM) in pure Ar, in comparison to that in Ar-CO2 mixture. In pure Ar, high GEM gains, of above 700 and 3000 for single and double GEM structures correspondingly, have been obtained. It is observed that the GEM effective gain and its charging-up are strongly affected by electric field values above and below the GEM. Applications to the development of non-ageing gas photomultiplier are discussed.

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G. Carugno

Infrared Emission: a New Possible Approach to Particle Detectors

A brief review on the infrared concepts and photodetectors will be summarized. Emission of infrared photons has been observed in an ionization chamber filled with standard gases and some results are reported. Light produced by the electron drifting in the gaseous media has also been observed. Results are presented as a function of the electric drift field.

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E. Nappi

Aerogel and Its Applications to RICH Detectors

Beam test results show that the ''new generation" aerogel has attractive features and appears an interesting candidate as radiator in Ring Imaging Cherenkov (RICH) detectors. The challenging applications envisaged in the LHCb experiment at CERN and in the HERMES experiment at DESY will be reviewed.

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Volume 16, Summer 1998

P.Fonte, N.Carolino, L.Costa, R.Ferreira-Marques, S.Mendiratta, V.Peskov, A.Policarpo

A New Type of Spark-protected Parallel Mesh Chamber

We developed a very low resistivity RPC-type detector, the anode of which was a plate made from materials with resistivity up to 5x107 Wcm, the cathode being a metallic mesh preceded by a drift region. In such detector it was actually possible to combine the versatility and high counting-rate capability of metallic PPACs with the extreme robustness and "protectiveness" of Resistive Plate Chambers. Occasional discharges triggered by large deposits of primary ionisation or by extreme counting rates are quenched by the resistive anode and are constrained to the glow discharge phase of the sparking process. The study shows that this discharge affects the detector only locally and the charge released is limited to a few tens of nC. Proportional counting rates up to 105 Hz/mm2 were achieved at gains above 104. The energy resolution at 6 keV was 20% FWHM. The observed gain-rate trade-off is well described by an analytic model and further improvements may be expected by lowering the resistivity of the anode material. The properties of several custom-made, controllable resistivity, anode materials are described and perspectives of improvement in the performance of the detector are discussed.

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P. Fonte, V. Peskov, B.D. Ramsey

Which Gaseous Detector is the Best at High Rates?

We report results from a systematic study of breakdown limits for various high rate gaseous detectors: PPAC's, MGC's, diamond-coated MSGC's, MICROMEGAS, CAT. It was found that for all these detectors, the maximum achievable gain, before breakdown appears, drops dramatically with incident flux, and is sometimes inversely proportional to it. Further, in the presence of alpha particles, typical of the backgrounds in high-energy experiments, additional gain drops by 1-2 orders of magnitude were observed for some detectors. We discovered that breakdowns at high rates occur through what we have termed an "accumulative mechanism", which does not seem to have been previously reported in the literature. Results of these studies may help to choose the optimum detector for given experimental conditions.

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A. Sharma

Properties of some gas mixtures used in tracking detectors

This report summarizes some useful data on the transport characteristics of gas mixtures which are required for detection of charged particles in gas detectors. The requirements for high luminosity tracking are stringent and different at low and high momenta, representing a compromise between a fast gas mixture, small diffusion properties and having a small Lorentz angle, but high primary ionization. With the advent of a host of computing programs available the transport parameters are rather well estimated and corroborated by experiment. Mixtures of some noble gases with popular quenchers are considered, with some emphasis on low mass gases. Pure noble gases for example argon and xenon are also presented with single photon detection and medical imaging applications in view respectively.

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Volume 15, Fall 1997

P. Fonte, V. Peskov, B.D. Ramsey

Streamers in MSGC's and other gaseous detectors

In this paper we describe the formation and propagation of streamers under different conditions and in different gas mixtures. We discuss how streamers may limit the operational capabilities of various gaseous detectors.

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J. Va'vra, J. A. Maly, and P. M. Va'vra

Soft X-Ray Production in Spark Discharges in Hydrogen, Nitrogen, Air, Argon, and Xenon Gases

We describe a generator of soft X-rays of energy between 2 and 10 keV by sparking in hydrogen, air, nitrogen, argon and xenon gases at low pressure with a sparking voltage as low as ~0.8 kV, which can be used as a simple monitor of the gaseous detectors. The X-ray production mechanism is discussed, including the possibility of a new process.

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M. Artuso et.al.,

Beam Tests of the CLEO III LIF-TEA Ring Imaging Cherenkov Detector

We present preliminary results from a test beam run of CLEO III RICH modules. The system consists of LiF radiators and multiwire proportional chambers containing a mixture of CH4 and TEA gases. The radiators were both flat and "sawtooth." The data were taken in a beam dump at Fermilab. We will discuss the chamber stability, electronics, the number of photons observed for both radiators, the angular resolution per photon and the angular resolution per track.

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A.J.P.L. Policarpo, et.al.,

Electron Multiplication and Secondary Scintillation in Liquid Xenon: New Prospects

The history, present situation and prospects on electron multiplication and secondary scintillation in liquid xenon and their application to radiation detectors are shortly discussed.

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Volume 14, Spring 1997

C. J. S. Damerell,

Radiation Damage in CCDs used as Particle Detectors

The CCD detectors have proven to be extremely usefull devices used for the precision 3-dimensional vertexing in the e+e- collider experiments such as the SLD experiment operating with the linear collider (SLC) at SLAC. The paper describes the radiation damage sensitivity of such detectors. The issue of the radiation damage is relevant especially for the future experiments running with the next liner colliders.

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Hartmut F.-W. Sadrozinski,

Silicon Microstrip Detectors in High Luminosity Application

The development of silicon microstrip detectors for high luminosity application at the Large Hadron Collider (LHC) is described. The technical choices are most severely restricted by the anticipated radiation damage. The arguments are presetned which led to the selection of the base-line detectors for the silicon tracker of the LHC detector ATLAS: sandwiches of single-sided detectors of n-strips in n-type bulk.

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Sherwood I. Parker, Christopher J. Kenney and Julie Segal

3D-A new architecture for solid-state radiation detectors

A proposed new architecture for solid-state radiation detectors using a th ree-dimensional array of electrodes that penetrate into the detector bulk is described. Proposed fabrication steps are listed. Collection distances and calculated collection times are about one ord er of magnitude less than those of planar technology strip and pixel detectors with electrodes confi ned to the detector surface, and depletion voltages are about two orders of magnitude lower. Maximum substrate thickness, often an important consideration for x-ray and gamma-ray detection, is con strained by the electrode length rather than by material purity or depletion-depth limitations d ue to voltage breakdown. Maximum drift distance should no longer be a significant limitation for Ga As detectors fabricated with this technology, and collection times could be much less than one ns. The ability of silicon detectors to operate in the presence of the severe bulk radiation damage e xpected at high-intensity colliders should also be greatly increased.

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Volume 13, Fall 1996

H. Pruchova and B. Franek,

3-Dimensional Simulation of Electron Avalanches in Low Pressure Wire Chambers and Proportional Counters

Monte Carlo code AVALAN was designed to simulate an electron avalanche development under any operating conditions of a proportional counter such as different gas pressures and electric fields. It alows to study any temporal and space aspects of the avalanche development. Initial simulations were performed for low pressure cylindrical counter filled with methane gas. Some results from these simulations are discussed.

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G. Comby,

Ceramic Electron Multiplier

The Ceramic Electron Multipliers (CEM) is a compact, robust, linear and fast multi-channel electron multiplier. The Multi Layer Ceramic Technique (MLCT) allows to build metallic dynodes inside a compact ceramic block. The activation of the metallic dynodes enhances their secondary electron emission (SEE). The CEM can be used in multi-channel photomultipliers, multi-channel light intensifiers, ion detection, spectroscopy, analysis of time of flight events, particle detection or Cherenkov imaging detectors.

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A. Bamberger et al.,

The Presampler for the Forward and Rear Calorimeter in the ZEUS Detector

The ZEUS detector at HERA has been supplemented with a presampler detector in front of the forward and rear calorimeters. It consists of a segmented scintillator array read out with wavelength-shifting fibers. We discuss its design, construction and performance. Test beam data obtained with a prototype presampler and the ZEUS prototype calorimeter demonstrate the main function of this detector, i.e. the correction for the energy lost by an electron interacting in inactive material in front of the calorimeter.

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S.F.Biagi et al.,

The Microdot Gas Avalanche Detector

The microdot gas avalanche detector is introduced and experimental measurements from the laboratory are described. Two separate batches of detector have been produced and results are presented showing the detectors gain dependence on cathode and drift voltage and the performance of such detectors to high intensity x-ray fluxes. The energy resolution at high rate and gain is also shown along with preliminary ageing measurements. Results obtained from single photo electron extraction by a UV source from the aluminium support of the drift cathode are presented at avalanche gains of up to 30000.

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R. Bouclier et al.,

The Gas Electron Multiplier (GEM)

We describe operating principles and results obtained with a new detector element: the Gas Electrons Multiplier (GEM). Consisting of a thin composite sheet with two metal layers separated by a thin insulator, and pierced by a regular matrix of open channels, the GEM electrode, inserted on the path of electrons in a gas detector, allows to transfer the charge with an amplification factor approaching ten. Uniform response and high rate capability are demonstrated. Coupled to another device, multiwire or micro-strip chamber, the GEM electrode permits to obtain higher gains or less critical operation; separation of the sensitive (conversion) volume and the detection volume has other advantages: a built-in delay (useful for triggering purposes), and the possibility of applying high fields on the photo-cathode of ring imaging detectors to improve efficiency. Multiple GEM grids in the same gas volume allow to obtain large amplification factors in a succession of steps, leading to the realization of an effective gas-filled photomultiplier.

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Volume 12, Spring 1996

J. Va'vra,

Editorial Comment

The ICFA Instrumentation Bulletin is intended to be a forum for people interested in generic instrumentation. The articles should be short, typically a few pages long, and describe either a novel technique or a previously unpublished measurement. We also intend to provide a forum for speculative ideas and not yet proven concepts. We invite articles from industry that describe novel instrumentation techniques. We especially encourage students to try to publish in this Bulletin and hope that their professors will be supportive. However, we discourage "system" descriptions, or papers describing lengthy analysis or software concepts. We believe that such work is already supported by a number of other periodicals and conferences.

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F. Sauli, RD28 Collab.,

Development of Micro-Strip Gas Chambers for Radiation Detection and Tracking at High Rates

The article describes the final conclusions of the RD-28 collaborative effort to develop the Micro-Strip Gas Chambers (MSGCs). The MSGCs have attracted a lot of interest due to many promising features: good position accuracy and two-track resolution, high rate capability and low cost. The article describes solutions to many difficulties, such as stability problems observed at high radiation rates attributed to substrate charging up and modifications, and ageing due to gas polymerization.

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E.C. Zeballos et al.,

The Multigap Resistive Plate Chamber

This paper describes the multigap resitive plate chamber (RPC). This is a variant of the wide gap RPC. However it has much improved time resolution, while keeping the other advantages of the wide gap RPC design.

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A.Breskin, A.Buzulutskov, R.Chechik, E.Shefer,

Towards gaseous detectors for visible photons

NaI protective coatings on visible cesium-antimony photocathodes have been studied. Protected photocathodes are shown to withstand exposure to considerable doses of oxygen and dry air. This opens ways to their handling and operation in gaseous detectors for visible photons.

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A. Pansky, A. Breskin and R. Chechik,

A new technique for studying the Fano factor and the mean energy per ion pair in counting gases

A new method is presented for deriving the Fano factor and the mean energy per ion pair in the ultrasoft x-ray energy range. It is based on counting electrons deposited by a photon in a low-pressure gas, and is applicable for all counting gases. The energy dependence of these parameters for several hydrocarbons and gas mixtures is presented.

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El-Mul Technologies Ltd.,

The Micro Sphere Plate: a novel electron multiplier

The paper describes the Microsphere Plate (MSP), which is a compact electron multiplier. MSPs are used in vacuum systems for the detection of charged particles. Applications include particle-imaging, time-of-flight mass spectroscopy, particle counting, ion-beam monitoring, and electron microscopy. MSPs are also used for UV and X-ray imaging and in photomultipliers.

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Karl M. Ecklund, Keith W. Hartman, Michael J. Hebert, Stanley G. Wojcicki,

Etching of Copper Coated Mylar Tubes with CF4 Gas

Using 5 mm diameter copper coated mylar straw tubes at a potential of 2.30 KV relative to a concentric 20 micrometer diameter gold-plated tungsten anode, it has been observed that with very low flow rates of CF4-based gases the conductive copper cathode material may be removed entirely from the mylar surface.

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