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High resolution drift chambers

Description: High precision drift chambers capable of achieving less than or equal to 50 ..mu..m resolutions are discussed. In particular, we compare so called cool and hot gases, various charge collection geometries, several timing techniques and we also discuss some systematic problems. We also present what we would consider an ''ultimate'' design of the vertex chamber. 50 refs., 36 figs., 6 tabs.
Date: July 1, 1985
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

Review of wire chamber aging

Description: This paper makes an overview of the wire chamber aging problems as a function of various chamber design parameters. It emphasizes the chemistry point of view and many examples are drawn from the plasma chemistry field as a guidance for a possible effort in the wire chamber field. The paper emphasizes the necessity of variable tuning, the importance of purity of the wire chamber environment, as well as it provides a practical list of presently known recommendations. In addition, several models of the wire chamber aging are qualitatively discussed. The paper is based on a summary talk given at the Wire Chamber Aging Workshop held at LBL, Berkeley on January 16-17, 1986. Presented also at Wire Chamber Conference, Vienna, February 25-28, 1986. 74 refs., 18 figs., 11 tabs.
Date: February 1, 1986
Creator: Va'Vra, J.
Partner: UNT Libraries Government Documents Department

Search for the best timing strategy in high-precision drift chambers

Description: Computer simulated drift chamber pulses are used to investigate various possible timing strategies in the drift chambers. In particular, the leading edge, the multiple threshold and the flash ADC timing methods are compared. Although the presented method is general for any drift geometry, we concentrate our discussion on the jet chambers where the drift velocity is about 3 to 5 cm/..mu..sec and the individual ionization clusters are not resolved due to a finite speed of our electronics.
Date: June 1, 1983
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

Measurement and simulation of the drift pulses and resolution in the micro-jet chamber

Description: We have tested a prototype of a micro-jet chamber, using both a nitrogen laser and a 10GeV electron beam. The achieved resolution in the particle beam was sigma = 18..mu..m for a lmm impact parameter and 22..mu..m when averaging over the entire beam profile. The experimental results were compared to a Monte Carlo program which simulates the pulse shapes and resolution in drift chambers of any geometry. The main emphasis in our simulation analysis was to study various strategies for drift chambers in order to achieve the best possible timing resolution.
Date: January 1, 1983
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

Wire aging of hydrocarbon gases with TMAE additions

Description: We report on experimental results describing wire aging properties of the CRID/RICH detectors in the TMAE gas environment. This test used 7 ..mu..m and 33 ..mu..m diameter carbon fibers, and 20 ..mu..m diameter gold-plated tungsten wires as sense wires, and operated in gas mixtures of either CH/sub 4/ or C/sub 2/H/sub 6/ at 1 atm, together with 0.6 Torr of the photoionizing vapor TMAE (tetrakis dimethylamino ethylene), which serves as a photocathode in the CRID detectors. The wires were damaged by the /sup 55/Fe x-rays. This paper is based on irradiation of 20 wires, each being a separate test. The gas purity was consistent with requirements of CRID detectors (<1 ppM of oxygen, <1 ppM of water). The test explored the aging as a function of wire diameter, wire material, gas flow, gas temperature, rate of radiation and gas type. Several chemical analyses of the deposit samples were performed (FTIR, ESCA and GC-MS techniques).
Date: October 1, 1986
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

Use of nitrogen laser for observation of space-charge effects in drift chambers

Description: A two-stage nitrogen laser has been built and is presently being used to investigate properties of drift chambers. In this paper we present the measured parameters of this laser, the results of a study of the double track separation in a drift chamber of jet design and a measurement of the saturation effects in this chamber as a function of total gain. An understanding of the saturation effects is important for drift chambers with multiple hit capability. The laser technique reported here represents a major improvement in the simplicity of investigation of the double track separation and saturation effects.
Date: October 1, 1982
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

Aging of gaseous detectors

Description: This paper makes an overview of developments in the wire chamber aging field since the wire chamber aging workshop held at the Lawrence Berkeley Laboratory, Berkeley, California on January 16--17, 1986. The author discusses new techniques to analyze the gas impurities and the wire aging products, wire nonaging'' in clean systems, wire aging in systems containing various impurities, various examples of problems which can prime'' surfaces prior to the occurrence of the aging, and some recent aging experience with the SSC micro-straw tubes.'' 35 refs., 10 figs., 2 tabs.
Date: March 1, 1990
Creator: Va'Vra, J.
Partner: UNT Libraries Government Documents Department

dE/dx prototype test

Description: A small prototype of a multiwire dE/dx detector was tested in SLAC's test beam. The basic concept of the detector was similar to the JADE drift cell design. The purpose of the test was to decide on some design parameters for a full size prototype, which is now in construction.
Date: October 1, 1980
Creator: Va'vra, J. & Rust, D.
Partner: UNT Libraries Government Documents Department

Focusing DIRC Design for Super B

Description: In this paper we present a new design of the Focusing DIRC for the Barrel PID to be used at the proposed Super-B factory. The new imaging optics is made of a solid Fused Silica block with a double folded optics using two mirrors, one cylindrical and one flat, focusing photons on a detector plane conveniently accessible for the detector access. The design assumes that the BaBar bar boxes are re-used without any modification, including the wedges and windows. Each bar box will have its own focusing block, which will contain 40 H-9500 (or H-8500) MaPMTs according to present thinking. There are 12 bar boxes in the entire detector, so the entire SuperB FDIRC system would have 480 MaPMTs. The design is very compact and therefore reduces sensitivity to the background. The chosen MaPMTs are fast enough to be able both to reject the background and to perform the chromatic correction. The 3D optics simulation is coded with the Mathematica program. The work in this paper was a basis of the LDRD proposal made to SLAC in 2009 [1].
Date: December 17, 2009
Creator: Va'Vra, J.
Partner: UNT Libraries Government Documents Department

Simulation of the Focusing DIRC Optics with Mathematica

Description: The Focusing DIRC is considered for the Barrel PID at a possible Super-B factory. To reduce sensitivity to background, it would be desirable to reduce a size of the present BaBar photon detector. One way to do it is to replace it with a focusing optics and use smaller photon detector pixels. We have simulated the focusing optics with simulation software based on a 3D calculation performed with the Mathematica program. The software does not use Optica package, instead, it uses its own 3D algorithm. The advantage of the presented method is that it is transparent, fast and that it uses a full backing of the Mathematica graphics, and it does not require expertise to run Geat4 MC software.
Date: February 15, 2010
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

Can TMAE photocathode be used for high rate applications?

Description: The paper explores the problems associated with wire aging, charging effects and self-sustaining cathode currents in the TMAE based photo-detectors. It is generally believed that anode wire aging is the most serious problem encountered in TMAE (tetrakis dimethylamino ethylene)-based Cherenkov ring imaging detectors. Although charging effects and self-sustaining cathod currents have not been studied systematically, there is concern that they too could become significant over a long period of time.
Date: March 1, 1995
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

Photon detectors

Description: J. Seguinot and T. Ypsilantis have recently described the theory and history of Ring Imaging Cherenkov (RICH) detectors. In this paper, I will expand on these excellent review papers, by covering the various photon detector designs in greater detail, and by including discussion of mistakes made, and detector problems encountered, along the way. Photon detectors are among the most difficult devices used in physics experiments, because they must achieve high efficiency for photon transport and for the detection of single photo-electrons. For gaseous devices, this requires the correct choice of gas gain in order to prevent breakdown and wire aging, together with the use of low noise electronics having the maximum possible amplification. In addition, the detector must be constructed of materials which resist corrosion due to photosensitive materials such as, the detector enclosure must be tightly sealed in order to prevent oxygen leaks, etc. The most critical step is the selection of the photocathode material. Typically, a choice must be made between a solid (CsI) or gaseous photocathode (TMAE, TEA). A conservative approach favors a gaseous photocathode, since it is continuously being replaced by flushing, and permits the photon detectors to be easily serviced (the air sensitive photocathode can be removed at any time). In addition, it can be argued that we now know how to handle TMAE, which, as is generally accepted, is the best photocathode material available as far as quantum efficiency is concerned. However, it is a very fragile molecule, and therefore its use may result in relatively fast wire aging. A possible alternative is TEA, which, in the early days, was rejected because it requires expensive CaF{sub 2} windows, which could be contaminated easily in the region of 8.3 eV and thus lose their UV transmission.
Date: October 1, 1995
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

Wire chamber gases

Description: In this paper, we describe new developments in gas mixtures which have occurred during the last 3--4 years. In particular, we discuss new results on the measurement and modeling of electron drift parameters, the modeling of drift chamber resolution, measurements of primary ionization and the choice of gas for applications such as tracking, single electron detection, X-ray detection and visual imaging. In addition, new results are presented on photon feedback, breakdown and wire aging.
Date: April 1, 1992
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

SLAC Cosmic Ray Telescope Facility

Description: SLAC does not have a test beam for the HEP detector development at present. We have therefore created a cosmic ray telescope (CRT) facility, which is presently being used to test the FDIRC prototype. We have used it in the past to debug this prototype with the original SLAC electronics before going to the ESA test beam. Presently, it is used to test a new waveform digitizing electronics developed by the University of Hawaii, and we are also planning to incorporate the new Orsay TDC/ADC electronics. As a next step, we plan to put in a full size DIRC bar box with a new focusing optics, and test it together with a final SuberB electronics. The CRT is located in building 121 at SLAC. We anticipate more users to join in the future. This purpose of this note is to provide an introductory manual for newcomers.
Date: February 15, 2010
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

Wire ageing with the TEA photocathode

Description: Recently several RICH protypes successfully tested a gaseous TEA photocathode. However, its wire ageing behavior is unknown. In principle, TEA is a more strongly bonded molecule than TMAE, and, as a result, one would expect better wire ageing behavior. This paper explores this question.
Date: June 1, 1996
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

ICFA instrumentation bulletin, Volume 15, Fall 1997

Description: The Bulletin reports on research and progress in the field of instrumentation with emphasis in the field of high-energy physics. This volume contains the following four papers: (1) Streamers in MSGC's and Other Gaseous Detectors; (2) Soft X-Ray Production in Spark Discharges in Hydrogen, Nitrogen, Air, Argon, and Xenon Gases; (3) Beam Tests of the CLEO III LiF-TEA Ring Imaging Cherenkov Detector; and (4) Electron Multiplication and Secondary Scintillation in Liquid Xenon: New Prospects.
Date: December 1, 1997
Creator: Va'vra, J.
Partner: UNT Libraries Government Documents Department

Photon detectors with gaseous amplification

Description: Gaseous photon detectors, including very large 4{pi}-devices such as those incorporated in SLD and DELPHI, are finally delivering physics after many years of hard work. Photon detectors are among the most difficult devices used in physics experiments, because they must achieve high efficiency for photon transport and for the detection of single photoelectrons. Among detector builders, there is hardly anybody who did not make mistakes in this area, and who does not have a healthy respect for the problems involved. This point is stressed in this paper, and it is suggested that only a very small operating phase space is available for running gaseous photon detectors in a very large system with good efficiency and few problems. In this paper the authors discuss what was done correctly or incorrectly in first generation photon detectors, and what would be their recommendations for second generation detectors. 56 refs., 11 figs.
Date: August 1, 1996
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

Wire chamber gases

Description: In this paper, we describe new developments in gas mixtures which have occurred during the last 3--4 years. In particular, we discuss new results on the measurement and modeling of electron drift parameters, the modeling of drift chamber resolution, measurements of primary ionization and the choice of gas for applications such as tracking, single electron detection, X-ray detection and visual imaging. In addition, new results are presented on photon feedback, breakdown and wire aging.
Date: April 1, 1992
Creator: Va`vra, J.
Partner: UNT Libraries Government Documents Department

FDIRC design for SuperB

Description: We describe a new design of a focusing DIRC (FDIRC) for the barrel PID at SuperB. The new FDIRC will use a new detector camera attached to the existing BaBar DIRC bar boxes. The camera's double-folded optics, made of solid fused silica, uses two mirrors, one cylindrical, and one flat. The camera's volume is 25-times smaller than the BaBar DIRC stand-off box, and its photon detectors will be 10-times faster than the BaBar DIRC PMTs, ensuring a good protection against backgrounds at SuperB, which is designed to operate at {approx}100-times higher luminosity than BaBar. The detector plane consists of a matrix of H-8500 MaPMTs.
Date: March 1, 2011
Creator: Va'vra, J.; /SLAC; Roberts, D.; U., /Maryland; Ratcliff, B. & /SLAC
Partner: UNT Libraries Government Documents Department

Ion Feedback Suppression Using Inclined MCP Holes in a _Single-MCP+Micromegas+Pads_ Detector

Description: We show that the ion backflow to photocathode can be completely suppressed if one uses inclined MCP holes in a presence of magnetic field. The inclined hole angles are chosen to be aligned with the Lorentz electron angle allowing the electron transmission and amplification, while positive ions, traveling along a different angle, are caught on the MCP hole walls. The detector under investigation is a new gaseous detector structure based on a tandem of two parts, a single MCP (Microchannel) plate, a Micromegas with pad readout. We are aiming to develop a gaseous photon detector with the Bialkali photocathode, however, one could use some ideas in the paper for other types of detectors.
Date: September 30, 2005
Creator: Va'vra, J.; /SLAC; Sumiyoshi, T. & U., /Tokyo Metropolitan
Partner: UNT Libraries Government Documents Department

A High-resolution TOF Detector _ A Possible Way to Compete with a RICH Detector

Description: Using two identical 64-pixel Burle/Photonis MCP-PMTs to provide start and stop signals, they have achieved a timing resolution of {sigma}{sub Single{_}detector} {approx} 7.2 ps for N{sub pe} {approx} 50 photoelectrons (N{sub pe}) with a laser diode providing a 1 mm spot on the MCP window. The limiting resolution achieved was {sigma}{sub Single{_}detector} {approx} 5.0 ps for N{sub pe} {approx} 180, for which they estimate the MCP-PMT contribution of {sigma}{sub MCP-PMT} {approx} 4.5 ps. The electronics contribution is estimated as {sigma}{sub Electrons} = 3.42 ps. These results suggest that an ultra-high resolution TOF detector may become a reality at future experiments one day.
Date: July 25, 2008
Creator: Va'vra, J; /SLAC; Ertley, C.; /Argonne; Leith, D.W.G.S.; Ratcliff, B. et al.
Partner: UNT Libraries Government Documents Department

A 30 ps Timing Resolution for Single Photons with Multi-pixel Burle MCP-PMT

Description: We have achieved {approx}30 psec single-photoelectron and {approx}12ps for multi-photoelectron timing resolution with a new 64 pixel Burle MCP-PMT with 10 micron microchannel holes. We have also demonstrated that this detector works in a magnetic field of 15kG, and achieved a single-photoelectron timing resolution of better than 60 psec. The study is relevant for a new focusing DIRC RICH detector for particle identification at future Colliders such as the super B-factory or ILC, and for future TOF techniques. This study shows that a highly pixilated MCP-PMT can deliver excellent timing resolution.
Date: July 5, 2006
Creator: Va'vra, J.; Benitez, J.; Coleman, J.; Leith, D.W.G.S.; Mazaheri, G.; Ratcliff, B. et al.
Partner: UNT Libraries Government Documents Department

Development of a Focusing DIRC

Description: Benefiting from the recent introduction of new fast vacuum-based photon detectors with a transit time spread of {sigma}{sub TTS} {approx} 30-150 ps, we are developing a novel RICH detector capable of correcting the chromatic error through good time measurements; we believe that this is the first time such a technique has been demonstrated. We have built and successfully tested a particle identification detector called ''Focusing DIRC''. The concept of the prototype is based on the BaBar DIRC, with several important improvements: (a) much faster pixelated photon detectors based on Burle MCP-PMTs and Hamamatsu MaPMTs, (b) a focusing mirror which allows the photon detector to be smaller and less sensitive to background in future applications, (c) electronics allowing the measurement of single photon timing to better than {sigma} {approx} 100-200ps, which allows a correction of the chromatic error. The detector was tested in a SLAC 10GeV/c electron test beam. This detector concept could be used for particle identification at Super B-factory, ILC, GlueX, Panda, etc.
Date: December 12, 2006
Creator: Benitez, J.; Bedajanek, I.; Leith, D.W.G.S.; Mazaheri, G.; Ratcliff, B.; Suzuki, K. et al.
Partner: UNT Libraries Government Documents Department