Wire Plane Research Articles

Breast conservation, the problem of treating the excision site effectively: Physical criteria for the choice of technique used

This paper examines how physical factors such as the depth of the excision cavity below the skin surface and its distance from the underlying lung may impact upon the choice between the use of an electron field (from a Varian Clinac 1800) or an implant (using a double plane of iridium-192 wires). Data have been derived from a phantom dosimetry experiment simulating different permutations of breast size and depth of excision cavity. An anthropomorphic female phantom with two different-sized wax breast phantoms has been used to simulate the clinical circumstances envisaged and iso-dose distributions have been estimated from an array of TLD readings. The biological significance of doses measured in skin and lung have been examined using the linear-quadratic (LQ) model. Both on physical and biological grounds, the results favour the implant under the experimental conditions adopted. The use of the electron beam to definitively treat the excision cavity (omitting breast tangents) to 60 Gy would result in unacceptable late effects in the skin and an observable incidence of pneumonitis if the excision cavity were near the chest wall. Small carcinogenic risks, particularly to the lung, are apparent with each modality, but may be moderated for the iridium-192 implant by a reduced carcinogenic potential associated with low-dose rate radiation. The use of the newer radionuclides iodine-125 and samarium-145, with less penetrating gamma ray emissions, might be preferred to iridium-192 from the point of view of bronchial carcinogenesis if definitive treatment of the exision cavity became widespread practice.

A DSP-based VME system for event selection

We describe a system based on several DSPs and the algorithm used to perform a fast one-pass track analysis of particles flowing through detectors composed of large planes of wires built for the ZEUS area of the HERA storage ring in Hamburg. The reasons for choosing DSPs for this modern solution are also given.

Intravaginal iridium-192 in the management of embryonal rhabdomyosarcoma

Three patients with vaginal rhabdomyosarcoma and residual vaginal disease following surgery and chemotherapy have been treated using high dose irradiation with vaginal moulds loaded with iridium-192. These patients remain well and disease-free seven years, 30 months and 18 months after their initial presentations. This paper describes a technique for local vaginal irradiation with individualized vaginal moulds made using a rapid-setting silastic foam impression and loaded with a single plane of iridium wires. Details of the dosimetry are also included.

Intravaginal iridium-192 in the management of embryonal rhabdomyosarcoma

<h2>Abstract</h2> Three patients with vaginal rhabdomyosarcoma and residual vaginal disease following surgery and chemotherapy have been treated using high dose irradiation with vaginal moulds loaded with iridium-192. These patients remain well and disease-free seven years, 30 months and 18 months after their initial presentations. This paper describes a technique for local vaginal irradiation with individualized vaginal moulds made using a rapid-setting silastic foam impression and loaded with a single plane of iridium wires. Details of the dosimetry are also included.

The Laser Beacon: A survey system for the torsion-free alignment and monitoring of the L3 Muon Spectrometer octants

Given the small sagitta of a few millimeters of high energetic muons in the L3 Muon Spectrometer at LEP (CERN) and the enormous dimensions (75 m 2 × 14 m) of this instrument, it is evident that alignment is the most critical task for its proper evaluation. In the chambers of each of the sixteen modules (“octants”), which form the spectrometer, wire planes are precisely positioned with respect to the front side and the rear side centerlines. A novel system - the Laser Beacon System - allows to make these centerlines coplanar within 25 μ rad by the aid of a reference plane defined by a sweeping laser beam. This restricts a possible torsion induced systematic momentum error for a 50 GeV/ c muon to 0.25%. The main design and production features of the Laser Beacon System are described. Results of measurements in test assemblies and in the octants are given.

Determination of the magnitudes and signs of flow parameters by hot-wire anemometry. Part II. Measurements using a triple hot-wire probe

This article deals with the determination of the magnitude and sign of the three components of the instantaneous velocity vector from the output signals of a triple-sensor hot-wire probe. All three sensors lie in the same plane with a given angular orientation. Measurements with this triple probe are performed with the wire plane inclined at an angle of about 45° to the main transport direction of the fluid, thus ensuring high sensitivity of the probe and the determination of the three components of the instantaneous velocity of the flow in magnitude and sense. Furthermore, the region of applicability and the accuracy of the values of the flow parameters of the method are discussed.

Progress report on Cerenkov ring imaging detector development

The authors present recent progress on the construction and testing of the first drift boxes and single-electron detectors as they come from the production line. These detectors will be used for particle identification using the ring imaging technique in the SLD (Standard Linear Collider Large Detector) experiment. Various experimental results are presented, including single-electron pulse height measurements as a function of gas gain, detector gating capability, uniformity of response across the wire plane, charge division performance of a single-electron signal, average pulse shape and its comparison with predicted shape, and crosstalk. >

Right-left ambiguity resolution in a time expansion chamber

In a Time Expansion Chamber two high resolution drift volumes on both sides of a small detection gap are separated from the gap by a fine grid wire plane. The charge asymmetry induced on the grid wires in the vicinity of an anode is used to resolve the right-left ambiguity. It is the only method which is fast enough for a first level trigger and which does not deteriorate the necessary field homogeneity.

Analytic solution of the potential and electric field of a jet type drift chamber

Starting from the known two-dimensional potential of a multiwire proportional chamber, the analytic expressions of the potential and the electric field are derived for a jet type drift chamber with a central wire plane of alternating sense and potential wires. The design goal of any jet chamber, namely the periodicity of the electric drift field, is imposed as a boundary condition at the beginning. In this way, the formulae are short and can be easily evaluated. In particular, expressions are given for the mean potential of the central wire plane, the drift field and the wire surface fields. Moreover, wire cathodes frequently used in jet chambers are described by analytic expressions. For a given drift field the difference of the potential as compared to a continuous metal cathode is presented. These results allowed to construct a two-dimensional computer simulation of the full OPAL jet chamber with no explicit periodicity but all its boundaries. Using field shaping electrodes a geometrically short yet quite satisfactory termination of a sense wire plane is demonstrated. Finally an example is presented, which is calculated in detail.

Test results from a precision drift chamber vertex detector prototype using dimethylether

Results of beam tests of a prototype drift chamber vertex detector developed for the D-Zero experiment at the Fermilab collider are reported. The chamber design emphasizes dual goals of high accuracy position measurement and excellent two track resolution. These requirements are met by using a slow gas, dimethyl ether, in a jet chamber geometry with a double plane of field-shaping wires near the anodes. Resolution of nearby hits is facilitated by 100 MHz flash digitization of the signal pulses. The prototype tested consisted of a full-length (97 cm) model of one azimuthal sector of the innermost layer of the detector, with 8 anode wires. Position measurement accuracy of 30–80 μm for drift distances of 2–11 mm and pulse pair resolution of 0.7 mm (for 90% of all pulses) is achieved.

Pulse shape simulation for drift chambers with long drift paths

A detailed Monte Carlo program for the simulation of drift chamber pulse shapes is described. It has been applied to the case of a jet chamber with drift paths up to 24 cm. Results on pulse shapes and corresponding spatial and double hit resolution are discussed and compared to recent measurements of the OPAL central detector jet chamber full size prototype and to measurements of a small 20-wire prototype, which was designed to study the pulse shapes generated by tracks in a magnetic field. Simulated pulse shapes and spatial resolutions agree well with the experimental data. Clustering, saturation and wire crosstalk are shown to be necessary ingredients in the simulation. A deterioration in resolution due to the influence of crosstalk signals is correctly reproduced, as well as the cancellation of this effect by a hardwired first and second neighbour crosstalk compensation. The simulation correctly describes the asymmetry in spatial resolution observed for tracks with positive or negative inclination against the wire plane when a magnetic field is present. The effect of saturation on double hit resolution is found to be small. The magnetic field is predicted to improve the double hit resolution.

A Novel Unidimensional Position Sensitive Multiwire Detector

A detector was developed to image large objects with neutral particles by a scanning technique. Hard X-rays are detected using a Tantalum converter plane placed at a grazing angle of 1 degree in respect to the incoming particles. The resulting electrons are detected by two planes of wires, one on each side of the converter plane. The detection efficiency is -- 30% for 400 keV ..gamma.. rays. Imaging of various objects was performed. Image resolution is better than 5 mm.

The L3 high-resolution muon drift chambers: Systematic errors in track position measurements

A prototype of the L3 muon chamber module, designed for measuring muon track positions, was built and tested. Measured simulated tracks made by an UV laser beam used for the internal alignment of the chambers in the module appeared to display a systematic positional error. The module measures the slope of laser tracks with high precision. The induced charge mechanism of proportional chambers creates an error in the slope of the same track if measured using a single wire plane. A simulation of the wire signals resulted in a good description of the error; also the calculated decrease in the signal size for tracks parallel to the wire plane tallied with the measurements.

Prototype results of a high resolution vertex drift chamber for the Mark II SLC upgrade detector

Test results from a full-length prototype of the drift chamber vertex detector for the Mark II SLC Upgrade detector are presented. The 22 cell jet chamber employs planes of grid wires above and below the sense wire plane to increase the electrostatic stability of the sense wires and to narrow the electron arrival time distribution. Two different grid designs have been investigated. The spatial resolution and pulse widths have been measured at a variety of operating points and for different timing schemes in a mixture of 92% CO 2 and 8% isobutane. Typical results at 3 atmospheres pressure give an average resolution over a 2 cm drift distance of 30 μm for both designs. Efficient double track detection is achieved for tracks separated by 500 μm for one design and by 1000 μm for the other.

Pulse shape analysis for a jet chamber with long drift paths in the presence of a magnetic field

A drift chamber with 20 anode wires was built in the style of a jet chamber, which allowed drift paths up to 25 cm. Pulses are digitized by means of a 100 MHz FADC-system. Variation of pulse shapes with track angle and drift distance are studied with and without magnetic field and related timing accuracies are calculated. A detailed program for the simulation of FADC pulse shapes has been developed. Pulse shapes and timing accuracies, derived from simulated pulses shown to compare well to data. It is also shown, that one has to expect a significant loss in space resolution for tracks parallel to the anode wire plane, if no hardwired cross talk compensation is applied.

The development of high-efficiency cathode converters for a multiwire proportional chamber positron camera.

A high-efficiency cathode converter for 511-keV photons has been developed for incorporation into a multiwire proportional chamber (MWPC) positron camera. The converter consists of a honeycomb pattern produced in a 1-mm-thick lead sheet to leave lead walls with a thickness of approximately 60 micron. The converter also serves as the cathode of an MWPC, the gap between the converter and the anode wire plane being 2.5 mm. This small gap results in a high secondary electron extraction efficiency without the need for additional drift voltages. Measurements of the efficiencies of a plane converter and of two types of structured converters in a single section MWPC are described and the efficiency is found to increase in proportion to the converter surface area. This result justifies the use of a simple theoretical model whereby an extrapolation to the efficiency of a detector consisting of a stack of 20 MWPC sections, each section having two converters, is made. The efficiency of this proposed system is calculated to be 17% for 511-keV photons.

Development of a tapered cell drift chamber II: Operation in high magnetic fields and different gas pressures

Several designs for drift cells have been constructed and tested in an electron beam at DESY. The designs tested consisted of pairs of adjacent tapered cells, of eight sense wires each, to simulate a portion of a layer of drift cells in a central tracking detector. For operation in a magnetic field three different tilts for the plane of the sense wires (0°, 20° and 45°) were used. Tests were made to study the operation and resolution of the drift cells under a variety of conditions. Ar:C 2H 6 (50:50) and Ar:CO 2:CH 4 (90:9:1) gas mixtures were used at absolute pressures of 1 to 4 bar for the former and at 1 bar for the latter. Measurements were made at different electric drift fields in conjunction with magnetic fields varying from 0 to 1.82 T. Aspects of the construction, electronics and operation are discussed and results regarding the resolution as a function of drift distance and operating conditions are presented with some model calculation.

A new detection system for backscattering Mössbauer spectroscopy

The construction and characteristics of a new detection system are described in the paper. This new detector consists of five wire planes, two of which are anode planes and three of which are cathode planes. Because two MWPC's with different parameters are adopted, the Mossbauer spectra of the conversion electron, resonance scattering γ-ray, Kx-ray and their coincidence spectrum can be recorded separately. The multiple Mossbauer spectra of the surface layer of several samples is shown.

A Multiwire Secondary Emission Profile Monitor for Small Emittance Beams

A secondary emission monitor using two multiwire grids separated by a positively biased collector has been constructed and tested with a 1 GeV electron beam at the Orsay Linac. The monitor installed just before the electron-positron converter has 8 gold-plated-tungsten wires of 0.1 mm diameter equally spaced 0.2 mm apart in each plane. Each wire is connected with an integrator using a low-bias current operational amplifier. The wire planes and the collector are moved into the beam by a stepping motor : that allows beam-position verification. We measured narrow profiles for 1 Amp peak current pulses of 30 nanoseconds width. Profiles are displayed on a scope and allow emittance determination by the three gradient method. Such a monitor is very useful to control the electron beam position and dimensions on the converter, because the positron source dimensions are rather bigger than those of the incident beam and the geometrical acceptance of the positron Linac is limited.

A system of large multiwire proportional chambers for a high intensity experiment

We describe a system of three multiwire proportional chambers used in the experiment NA24 at CERN. Each chamber consists of four wire planes (2 × 2 m 2 sensitive area), packed together in the same mechanical frame with only five cathode foils. All planes are electrically independent and can be operated individually although each of the three inner cathode foils is used for two adjacent wire planes. Another feature of the chamber is that an area around the beam can be desensitized to allow operation in a high intensity beam.