Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session HH: GLUEX Instrumentation |
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Chair: Curtis Meyer, Carnegie Mellon University Room: Jewett Ballroom F |
Saturday, October 25, 2008 2:00PM - 2:12PM |
HH.00001: A Novel Design of a High-Resolution Hodoscope for the Hall D Tagger based on Scintillating Fibers Richard Jones, Igor Senderovich, Carl Nettleton The tagging spectrometer designed for Hall D is instrumented with two hodoscopes, a low-resolution array spanning the full photon energy range from 3 to 11.6 GeV, and a high-resolution ``microscope'' covering just the region of the primary peak in the coherent bremsstrahlung spectrum in the range 8.4 - 9.0 GeV. The microscope is constructed of a two-dimensional array of square scintillating fibers several cm in length, whose axes are aligned with the tagging electron trajectories. The motivation for the segmentation in both x and y is presented. Various components of the detector have been prototyped and tested on the bench, including in particular the silicon photomultiplier (SiPM) that will be used to detect the scintillations. Custom electronics for this readout have been designed that are adapted to the peculiar features of the SiPM devices. A small-scale prototype of the microscope is under construction, to be tested in an electron beam in the near future. [Preview Abstract] |
Saturday, October 25, 2008 2:12PM - 2:24PM |
HH.00002: Flash ADC readout of the GlueX forward electromagnetic calorimeter Mihajlo Kornicer The GlueX experiment at Jefferson Lab will use a 9 GeV high-rate ($10^7 -10^8/s$) photon beam, incident on a liquid hydrogen target, to search for hybrid-meson production in the mass range of 1.5-2.5 GeV/$c^2$. Abundant photon production from neutral meson decays is expected in the decay chains of hybrid mesons, which will result in several photons in the forward region. The forward electromagnetic calorimeter (FCAL) of the GlueX detector is designed to reconstruct final state photons using an array of 2800 lead-glass blocks. The FCAL will employ flash analog-to-digital converter (FADC) technology to measure both deposited energy and photon arrival time using pulses from FEU-84-3 photomultiplier tubes. A real-time sum of the total calorimeter energy will be used as an input to the trigger. Timing information from individual crystals will be used to suppress the expected high-level of electromagnetic background from the photon beam and forward-going charged particles. We present the performance characteristics of the calorimeter readout based on simulation and data taken with a prototype 12-bit, 250 MHz flash ADC. [Preview Abstract] |
Saturday, October 25, 2008 2:24PM - 2:36PM |
HH.00003: The GlueX Central Drift Chamber Yves Vanhaarlem The GlueX Central Drift Chamber (CDC) is a cylindric detector located close to a liquid hydrogen cell as a part of the GlueX spectrometer in Hall-D at Jefferson Lab. It is designed to track charged particles originating from a 12 GeV polarized photon beam impinging on a liquid hydrogen target. One of the main goals of the GlueX experiment is to map out the hybrid meson spectra. The CDC has to be able to track charged particles with relative large polar angles (6-165 degrees) in a solenoid magnetic field of 2.24 T. Also, this detector has to perform particle identification: to separate pions from protons in a momentum range up to 450 MeV/c. To fulfill these tasks the GlueX collaboration opted for a straw tube chamber because this option minimizes the material in the tracking region. The straw tubes will be 1.5~$m$ long and the chamber will consist of 24 layers (16 axial + 8 stereo). The current status of this detector and test results obtained with a full scale prototype will be presented. [Preview Abstract] |
Saturday, October 25, 2008 2:36PM - 2:48PM |
HH.00004: Level-1 Trigger and DAQ system of the GlueX experiment Alexander Somov The goal of the GlueX detector at Jefferson Lab is to study fundamental questions of the quantum chromodynamics, i.e., the nature of confinement of gluons and quarks. The detector's design is optimized to measure the spectrum of exotic mesons that are expected to be produced in interactions of 8.4 - 9.0 GeV linearly polarized photons with a liquid hydrogen target. The GlueX trigger and DAQ electronics is based on pipelined TDC boards and FADC boards running at a 250 MHz clock. The trigger logic is implemented on special purpose programmable electronics boards with Field-Programmable Gate Array chips. Two types of boards are used: Crate Trigger Processors and Global Trigger Processors. All trigger electronics is hosted in VXS crates. The Level-1 trigger should reduce the 200 MHz electromagnetic rate and the 400 kHz hadronic rate to 200 kHz total rate. The trigger algorithm makes use of a measurement of the energy deposition in two electromagnetic calorimeters and hit counts in the time-of-flight detector and the tagger hodoscopes. We will present the trigger and DAQ design of the GlueX experiment and describe the Level-1 trigger algorithm in detail. [Preview Abstract] |
Saturday, October 25, 2008 2:48PM - 3:00PM |
HH.00005: Optimization of Performance Parameters for Large Area Silicon Photomultipliers Kathryn Janzen The goal of the GlueX experiment is to search for exotic hybrid mesons as evidence of gluonic excitations in an effort to better understand confinement. A key component of the GlueX detector is the electromagnetic barrel calorimeter (BCAL) located immediately inside a superconducting solenoid of approximately 2.5T. Because of this arrangement, traditional vacuum photomultiplier tubes (PMTs) which are affected significantly by magnetic fields cannot be used on the BCAL. The use of Silicon photomultipliers (SiPMs) as front-end detectors has been proposed. While the largest SiPMs that have been previously employed by other experiments are $1\times1$~mm$^2$, GlueX proposes to use large area SiPMs each composed of 16~-~3$\times$3~mm$^2$ cells in a $4\times4$ array. This puts the GlueX collaboration in the unique position of driving the technology for larger area sensors. In this talk I will discuss tests done in Regina regarding performance parameters of prototype SiPM arrays delivered by SensL, a photonics research and development company based in Ireland, as well as sample $1\times1$~mm$^2$ and $3\times3$~mm$^2$ SiPMs. [Preview Abstract] |
Saturday, October 25, 2008 3:00PM - 3:12PM |
HH.00006: The GlueX Forward Drift Chambers Simon Taylor The 12 GeV upgrade program at Jefferson Laboratory calls for the construction of a new experimental hall that will house a large-acceptance detector designed to study the excitation of the gluonic field binding quark--anti-quark pairs into mesons produced by a photon beam running at a tagged rate of $10^7\gamma/s$. The GlueX detector is based on a large solenoid magnet that will enclose a lead--scintillating fiber calorimeter for detection of photons and drift chambers for tracking charged particles. The paths of particles traveling in the $1^{\circ}-20^{\circ}$ angular range downstream of the target will be measured by a set of cathode strip chambers consisting of wire planes flanked by cathode planes divided into strips, enabling precision measurements of avalanche positions along the wires. The coordinate transverse to the wire is determined using the drift time. The combination of wire and cathode readout allows for reconstruction of ``space points'' at several positions along the beam line. I will present results from extensive studies of a small-scale prototype of one cathode strip chamber unit and discuss issues arising from operation within a large magnetic field. [Preview Abstract] |
Saturday, October 25, 2008 3:12PM - 3:24PM |
HH.00007: Performance of the prototype module of the GlueX electromagnetic barrel calorimeter Zisis Papandreou, Blake Leverington, George Lolos A photon beam test of the 4~m long prototype lead/scintillating fibre module for the GlueX electromagnetic barrel calorimeter was carried out in Hall B at the Thomas Jefferson National Accelerator Facility with the objective of measuring the energy and timing resolutions of the module as well as the number of photoelectrons generated. Data were collected over an energy range of 150 to 650 MeV at multiple positions and angles along the module. Details of the analysis at the centre of and perpendicular to the module will be presented. [Preview Abstract] |
Saturday, October 25, 2008 3:24PM - 3:36PM |
HH.00008: Beam Position Stabilization Using an Active Collimator in Hall D at Jefferson Lab Richard Jones, Igor Senderovich The GlueX experiment planned for Hall D at Jefferson Lab relies on the process of coherent bremsstrahlung by 12 GeV electrons in a diamond crystal to produce a secondary beam of 9 GeV photons with a high degree of linear polarization. To achieve optimum polarization, the photon beam must be collimated to a half-angle of 20 $\mu$r, which requires a long flight path of 75 m between the radiator and collimator and a means to keep the beam spot centered on the collimator aperture with an accuracy of a few $\mu$r. A active collimator has been designed which is capable of monitoring the centroid of the photon beam to within $\pm 200$ $\mu$m, with a sampling frequency of up to several hundred Hz. A prototype of this this device has been tested in the photon beam in Hall B. Results from this test are presented. [Preview Abstract] |
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