D. Briggs

Studies of helium gas mixtures in drift chambers

Some properties of gas mixtures composed predominately of helium and lesser amounts of CO2 and isobutane were measured in a prototype drift chamber. The studies are motivated by the desire to reduce the multiple scattering inside the drift chamber at future high-luminosity, low-energy facilities such as φ factories, τ/charm factories, and B factories. The low atomic number of helium greatly reduces the multiple scattering contribution to the momentum resolution compared to an argon-based gas mixture. The position resolution, pulse height, efficiency, and breakdown characteristics were measured for various gas mixtures. A mixture of 83% He, 10% CO2, and 7% isobutane gives comparable results to that of an argon-based gas commonly used in drift chambers.

The SLAC Mark II Upgrade Drift Chamber Front End Electronics

The SLAC Mark II detector is being improved by the addition of a new main drift chamber and associated electronics to prepare it for operation as the first detector at SLC. Presented here are the initial signal processing electronics, the preamplifiers, amplifiers and discriminators for the 5832 sense wires, which are located on the detector itself. The performance of the detector is established almost entirely by the drift chamber and this electronics.

Design of a wire imaging synchrotron radiation detector

The design of a detector invented to measure the positions of synchrotron radiation beams for the precision energy spectrometers of the Stanford Linear Collider (SLC) is described. The energy measurements involve the determination, on a pulse-by-pulse basis, of the separation of pairs of intense beams of synchrotron photons in the megaelectronvolt energy range. The detector intercepts the beams with arrays of fine wires. The ejection of Compton recoil electrons results in charges being developed in the wires, thus enabling a determination of beam positions. >

A CDU-based data acquisition system for the energy spectrometer at the Standard Linear Collider

The authors discuss the design and performance of a system using the calorimetry data unit (a 32-channel multisample analog integrated circuit) to read out the charge ejected by secondary emission of a synchrotron beam from wires lying in its path. The wires comprise the wire-imaging synchrotron radiation detector in the SLC (Stanford Linear Collider) extraction-line spectrometer. The primary module in the system is a board containing 24 channels of charge-sensitive amplification, shaping, sampling, multiplexing, and digitization. This board also provides a fast analog measure of the charge distribution across the wires. The time between the beam crossing and completion of data acquisition into CAMAC is shown to be 1.1. ms, providing beam pulse energy measurements at the maximum accelerator repetition rate of 180 Hz for every event logged by the Mark II detector. >

Design of a trigger and data acquisition system for a detector at PEP-II

This paper proposes a design of a trigger and data acquisition system for a detector at the PEP-II B Factory. The system is asynchronous, data-driven, and scalable. Design goals include orthogonal tracking and calorimetric triggers, minimal dead time, graceful degradation, high efficiency, and useful performance in the face of backgrounds so high as to overwhelm reconstruction. Also described are instrumentation of the Drift Chamber, based on 8-bit FADCs, and of the Calorimeter, based on a new custom integrated circuit, the Charge Amplifier with Range Encoding (CARE), and 10-bit ADCs. This design employs commercial embedded CPUs in VME and VXI crates. >

Studies of helium based drift chamber gases for high-luminosity low energy machines

Future high luminosity low energy machines will need low mass tracking chambers to order to minimize multiple scattering of the relatively low momentum tracks produced at these facilities. A drift chamber using a helium based gas rather than a conventional argon based gas would greatly reduce the amount of multiple scattering. This paper summarizes measurements of the drift velocity and position resolution for gas mixtures of helium with CO{sub 2} and isobutane and helium with DME. Good spatial resolutions are obtained. A design of a drift chamber with only 0.12% of a radiation length (gas plus wire) over a 60 cm tracking distance is presented.

The electronics and data acquisition system for the wire imaging synchrotron radiation detector at the SLC

The Stanford Large Collider (SLC), located at the Stanford Linear Accelerator Center, collides electrons and positrons produced in the linear accelerator pulse by pulse. The energy of each beam is determined by measuring the angle of deflection of the beam in the SLC extraction lines. Each extraction line consists of two bending magnets that produce synchrotron radiation, and a spectrometer analyzing magnet that deflects the beam. The synchrotron light is detected by using the emission of electrons produced by Compton scattering off Cu-Be wires. The electronics used to detect the approximately 180 fC of charge on the wire is described. The performance of the system, including the equivalent noise charge, crosstalk stability, and reliability are discussed. >

Initial performance of the Wire Imaging Synchrotron Radiation Detector

The initial performance of a novel detector (called the Wire Imaging Synchrotron Radiation Detector) that measures the positions of intense synchrotron-radiation beams with high precision is described. Two detectors of this kind are used for the precision energy spectrometers of the Stanford Linear Collider (SLC). The detectors accurately determine the distance between pairs of intense synchrotron beams of typically 1-MeV photons, which are emitted by the primary electron and positron beams of the SLC. The detectors intercept the synchrotron beams with arrays of fine wires. The ejection of Compton-recoil electrons leaves positive charges on the wires, enabling a determination of beam positions. Preliminary measurements indicate that it is possible to determine the synchrotron stripe positions to better than 25 mu m. >