Bulletin of the American Physical Society
2017 Fall Meeting of the APS Division of Nuclear Physics
Volume 62, Number 11
Wednesday–Saturday, October 25–28, 2017; Pittsburgh, Pennsylvania
Session NJ: Nuclear Instrumentation IV |
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Chair: Adam Fritsch, Gonzaga University Room: City Center A |
Saturday, October 28, 2017 8:30AM - 8:42AM |
NJ.00001: The ALICE TPC Upgrad Andrew Castro The Time Projection Chamber (TPC) currently used for ALICE (A Large Ion Collider Experiment at CERN) is a gaseous tracking detector used to study both proton-proton and heavy-ion collisions at the Large Hadron Collider (LHC) In order to accommodate the higher luminosit collisions planned for the LHC Run-3 starting in 2021, the ALICE-TPC will undergo a major upgrade during the next LHC shut down. The TPC is limited to a read out of 1000 Hz in minimum bias events due to the intrinsic dead time associated with back ion flow in the multi wire proportional chambers (MWPC) in the TPC. The TPC upgrade will handle the increase in event readout to 50 kHz for heavy ion minimum bias triggered events expected with the Run-3 luminosity by switching the MWPCs to a stack of four Gaseous Electron Multiplier (GEM) foils. The GEM layers will combine different hole pitches to reduce the dead time while maintaining the current spatial and energy resolution of the existing TPC. Undertaking the upgrade of the TPC represents a massive endeavor in terms of design, production, construction, quality assurance, and installation, thus the upgrade is coordinated over a number of institutes worldwide. The talk will go over the physics motivation for the upgrade, the ALICE-USA contribution to the construction of Inner Read Out Chambers IROCs, and QA from the first chambers built in the U.S [Preview Abstract] |
Saturday, October 28, 2017 8:42AM - 8:54AM |
NJ.00002: STAR beam energy scan phase II and the iTPC upgrade Flemming Videbaek The second phase of the Beam Energy Scan at RHIC will occur in 2019-2020 and will explore with precision measurements in the part of the QCD phase diagram where baryon densities are high. The measurements will be possible with an order of magnitude better statistics thanks to the electron cooling upgrade of RHIC, and the addition of STAR upgrades. One of these upgrades is the replacement of the STAR inner TPC sector (iTPC). The upgrade will increase the rapidity acceptance for identified hadrons by about 40\%. The talk will discuss progress for the iTPC construction, both mechanical and electronics development and the current schedules. Some of the key physics measurements Expected results of some of the key measurements, kurtosis of net-protons that could pinpoint the position of a critical point, measurements of directed flow of baryons vs. energy that might prove a softening of the EOS , and chiral restoration in the di-lepton channel will be presented. [Preview Abstract] |
Saturday, October 28, 2017 8:54AM - 9:06AM |
NJ.00003: Construction of the STAR Event Plane Detector Joseph Adams The Event Plane Detector (EPD) is an upgrade to the STAR experiment at RHIC, providing high granularity and acceptance in the forward (2.2 < |eta| < 5.1) region. This will improve the resolution of the event plane determination and allow selection on the collision centrality at rapidities well-separated from the midrapidity region measured by the STAR Time Projection Chamber (TPC). The EPD consists of two scintillator discs, one at positive and one at negative rapidity, 3.75 m from the center of the TPC. Each disc is segmented into 372 optically isolated tiles, read out by wavelength shifting fibers coupled to silicon photomultipliers. One quarter of a single disc was installed in STAR for the 2017 run for commissioning. In this talk I will discuss the construction of the EPD, the installation of the quarter wheel, and plans for full installation in 2018. [Preview Abstract] |
Saturday, October 28, 2017 9:06AM - 9:18AM |
NJ.00004: Optical fibers and electronics for the STAR Event Plane Detector Catherine Tomkiel The Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider has shown hints of a critical point and first order phase transition at the BES energies. Key measurements for locating the critical point and determining the first order phase transition are limited by poor event plane resolution, limited statistics and a TPC-only centrality determination. A new event plane and collision centrality detector (EPD) is planned to replace the existing detector, the Beam-Beam Counter (BBC), with higher granularity and acceptance. The design of the EPD consists of two scintillator discs at z$=$ \textpm 3.75m from the center of STAR, covering 2.2 \textless $\eta $ \textless 5.1. The signal from the scintillator is carried by wave-length shifting fibers, to clear fibers to be read out by silicon photomultipliers (SiPM) - an inexpensive and magnetic field insensitive replacement for the traditional phototube. In this talk we will discuss the construction of the fiber bundles, their installation and performance as well as their integration into the STAR electronics system. [Preview Abstract] |
Saturday, October 28, 2017 9:18AM - 9:30AM |
NJ.00005: Performance of the STAR Event Plane Detector Justin Ewigleben The Beam Energy Scan (BES) program at the Relativistic Heavy-Ion Collider has shown hints of a critical point and first order phase transition at the BES energies. Key measurements for locating the critical point and determining the first order phase transition are limited by poor event plane resolution, limited statistics and a TPC-only centrality determination. A new event plane and collision centrality detector (EPD) is planned to replace the existing detector, the Beam-Beam Counter (BBC), with higher granularity and acceptance. The design of the EPD consists of two scintillator discs at z$= \pm$ 3.75m from the center of STAR, covering 2.2 $< \eta <$ 5.1. One quarter of a single disc was installed in STAR for the 2017 run for commissioning. In this talk we will discuss the detector performance during this commissioning run in both proton-proton collisions at $\sqrt{s}$ = 510 GeV and Au-Au collisions at $\sqrt{s_{NN}}$ = 54.4 GeV. [Preview Abstract] |
Saturday, October 28, 2017 9:30AM - 9:42AM |
NJ.00006: Future Measurements Possible with the NIFFTE fissionTPC Rusty Towell The Neutron Induced Fission Fragment Tracking Experiment (NIFFTE) Collaboration has applied the proven technology of Time Projection Chambers (TPC) to the task of precisely measuring fission cross sections. The exquisite tracking capabilities of the NIFFTE fissionTPC allow the full reconstruction of charged particles produced by neutron beam induced fissions from a thin central target. Precise measurements have been made at the Los Alamos Neutron Science Center with U-235, U-238 and Pu-239 targets. The wealth of information gained from this approach will allow systematics to be controlled at the level of 1%. The large investment of time and money that have been dedicated to the development of the fissionTPC can be leveraged in the future to make a variety of measurements beyond those for which it was originally intended. This presentation will highlight some of the options for extending the fissionTPC program. [Preview Abstract] |
Saturday, October 28, 2017 9:42AM - 9:54AM |
NJ.00007: Extending the Dynamic Range of a Time Projection Chamber Justin Estee The use of Time Projection Chambers (TPCs) in intermediate heavy ion reactions faces some challenges in addressing the energy losses that range from the small energy loss of relativistic pions to the large energy loss of slow moving heavy ions. A typical trade-off can be to set the smallest desired signals to be well within the lower limits of the dynamic range of the electronics while allowing for some larger signals to saturate the electronics. With wire plane anodes, signals from readout pads further away from the track remain unsaturated and allow signals from tracks with saturated pads to be accurately recovered. We illustrate this technique using data from the SAMURAI Pion-Reconstruction and Ion-Tracker (S$\pi$RIT) TPC , which recently measured pions and light charged particles in collisions of Sn+Sn isotopes. Our method exploits knowledge of how the induced charge distribution depends on the distance from the track to smoothly extend dynamic range even when some of the pads in the track are saturated. To accommodate the analysis of slow moving heavy ions, we have extended the Bichsel energy loss distributions to handle slower moving ions as well. In this talk, I will discuss a combined approach which successfully extends the dynamic range of the TPC electronics. [Preview Abstract] |
Saturday, October 28, 2017 9:54AM - 10:06AM |
NJ.00008: Novel Gated Grid Utilization for Time Projection Chambers Gene Van Buren, James H. Thomas Large TPCs, such as STAR or ALICE, have traditionally been built with wire chamber readout using a gated wire grid to trigger the event readout cycle. More modern TPCs, such as the ALICE upgrade and possibly sPHENIX, plan to use GEM chamber readout without a gated grid in order to be able to read events at even higher rates than a continually shuttered gated grid will allow. We are interested in scenarios where an existing TPC with a gated grid structure can be used to acquire events at higher rates by leaving the gated grid open for several events rather than to synchronize the opening and closing of the gate with each event. This mode is enabled by the large difference in drift velocities (approximately four orders of magnitude) between the incoming electrons and the outgoing ions. We will report on our progress in understanding the performance of such an operating mode. [Preview Abstract] |
Saturday, October 28, 2017 10:06AM - 10:18AM |
NJ.00009: Simulation Studies of Drift Gas Mixtures for BONuS12 RTPC Nathan Dzbenski The Barely Off-shell Nucleon Structure experiment at 12 GeV (BONuS12) will use a radial time-projection chamber (RTPC) in a magnetic field to study (nearly-free) neutron structure functions. This RTPC will record slow-moving spectator protons in coincidence with scattered electrons from deuterium. The detector will be installed in the CEBAF Large Acceptance Spectrometer (CLAS12) in Experimental Hall B at Thomas Jefferson National Accelerator Facility (JLab). The original BONuS experiment ran in 2005 with a drift-gas mixture of helium and dimethyl ether (DME). With a new BONuS detector being developed for use in 2019, we have to find an optimal mixture of non-flamable gasses with a fast drift velocity and a small drift angle. I will present simuations performed with Garfield++ to identify such a drift-gas mixture suitable for this RTPC. [Preview Abstract] |
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