Bulletin of the American Physical Society
2006 Division of Nuclear Physics Annual Meeting
Wednesday–Saturday, October 25–28, 2006; Nashville, Tennessee
Session BD: Mini-symposium on Applications of GEM Technology |
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Sponsoring Units: DNP Chair: Howard Fenker, Thomas Jefferson National Accelerator Facility Room: Gaylord Opryland Hermitage A |
Thursday, October 26, 2006 2:00PM - 2:36PM |
BD.00001: Development and Applications of the Gas Electron Multiplier Invited Speaker: Detectors based on the Gas Electron Multiplier (GEM), introduced a few years ago, have excellent high rate capabilities and are used for fast tracking in several HEP experiments. After a brief general introduction on gaseous micro-pattern devices, I will describe the major operating characteristics of GEM-based detectors, and provide examples of implementation and performances in running and proposed experiments. Novel developments include the use of GEMs as end-cap detectors in Time Projection Chambers for the Linear Collider and for a Hadron-Blind detector at BNL. Coating the first GEM in a cascade with a photosensitive layer permits to detect and localize single photons; recent developments in view of applications in Cherenkov Ring Counters will be described. The excellent micro-pattern imaging characteristics are exploited for neutron detection and for measurement of X-ray polarization in astrophysics. Operation in cryogenic conditions has also been demonstrated, opening the way to new possibilities in detection of WIMPs and dark matter. [Preview Abstract] |
Thursday, October 26, 2006 2:36PM - 2:48PM |
BD.00002: Advances in Thick GEM-like (THGEM) multipliers Amos Breskin, Rachel Chechik, Marco Cortesi, Volker Dangendorf The concept and properties of the novel and robust Thick GEM-like (THGEM) hole-multiplier, economically produced by standard printed-circuit techniques, is presented. It has a GEM-like structure and operation mode, with dimensions expended to the sub-mm to mm scales, and mechanically-drilled holes etched at their rim. Very high electron multiplication, 10$^{5}$ and 10$^{7}$ in single- and double-THGEM elements were reached; very efficient electron transport into and out of the holes permits efficient multi-element cascading. The fast avalanche buildup leads to ns timing properties and rates exceeding MHz/mm$^{2}$. The THGEM can efficiently detect single gas-ionization electrons or radiation-induced electrons from a solid converter -- e.g. a photocathode deposited on its top surface. The former is important for particle tracking, x-ray imaging etc, and the latter has important applications in photon and neutron imaging. The results of recent studies will be presented, including sub-mm imaging properties of a 100x100 mm$^{2}$ detector prototype. Potential applications will be discussed: UV-photon imaging in RICH, moderate-resolution tracking, TPC read out, sampling elements in calorimetry, x-ray and neutron imaging, charge and light detection in 2-phase noble-liquid detectors etc. [Preview Abstract] |
Thursday, October 26, 2006 2:48PM - 3:00PM |
BD.00003: The BoNuS GEM-Based Radial Time-Projection Chamber Howard Fenker A special-purpose detector for measuring low-momentum spectator protons from e-d collisions has been developed. It is a radial time-projection chamber in which the gas-amplification elements are GEM foils formed into cylinders. This is believed to be the first application of curved GEMs. In a 4T magnetic field, this low-mass detector allows tracking of spectator protons with momentum as low as 70 MeV/c while covering a large solid angle. Physics data were taken using the system in late 2005. We report on the development of the detector, experience with operating it, and the data coming out of it. [Preview Abstract] |
Thursday, October 26, 2006 3:00PM - 3:12PM |
BD.00004: A novel idea for an ultra-light cylindrical GEM based vertex detector Danilo Domenici, Giovanni Bencivenni, Enzo Iacuessa, Stefano Lauciani, Fabrizio Murtas An ultra-light cylindrical triple-GEM detector for vertex purposes is being developed. The cathode, the three GEMs and the anode are five concentric cylinders, obtained winding parallelogram-shaped foils, with a resulting helicoidal junction overlap ($<$3 mm wide). The result is a wholly cylindrical GEM, almost free of dead-zones and without support frames inside the active area, fruitfully usable as a vertex detector. The detetector is also extremely light: considering that the material used is mainly kapton, and the possibility to reduce the copper layer thickness to 2$\mu$m, a single tracking layer can have a material budget as low as 0.2\% of X$_0$. The readout of the detector is performed with large stereo angle U-V strip layers: one directly realized on the anode electrode, and the other onto the bottom side of the third GEM foil. Considering a large stereo angle of about 40 degrees and a strip pitch of 400$\mu$m, the spatial resolutions achievable are $\sigma$$_{r\phi} \simeq \sigma_z \sim 200 \mu$m. In order to avoid ambiguity in the position reconstruction the right strips crossing angle, corresponding to the winding angle, must be tg$\theta$ = L/$\pi$R (where L is the lenght of the vertex detector and R its radius). The mechanical assembly of one single layer is described and preliminary results obtained with an Ar/CO$_2$ = 70/30 gas mixture are discussed. [Preview Abstract] |
Thursday, October 26, 2006 3:12PM - 3:24PM |
BD.00005: Development of tracking detectors for STAR with industrially produced GEM foils Frank Simon, Bernd Surrow The planned tracking upgrade of the STAR experiment at RHIC includes a large-area GEM tracker used to determine the charge sign of electrons and positrons produced from W+(-) decays. For such a large-scale project commercial availability of GEM foils is necessary. We report first results obtained with a triple GEM detector using GEM foils produced by TechEtch Inc of Plymoth, MA, USA. Measurements of gain uniformity, long-term stability as well as measurements of the energy resolution for X-Rays are compared to results obtained with an identical detector using GEM foils produced at CERN. A quality assurance procedure based on optical tests using an automated high-resolution scanner has been established. Comparative measurements for CERN and TechEtch produced GEM foils will be presented. [Preview Abstract] |
Thursday, October 26, 2006 3:24PM - 3:36PM |
BD.00006: A Hadron Blind Detector for the PHENIX experiment at RHIC Takao Sakaguchi The thermal dileptons emitted from a hot and dense nuclear matter are an important probe to understand the quark deconfinement transition because they reflect the initial temperature and the degree of freedom of the matter. The measurement of dileptons is, however, very challenging due to a huge combinatorial background. With the present set-up of the PHENIX detector, a signal to background ratio is expected to be $\sim$1/500, and therefore an efficient rejection of the background is necessary. The background mainly arises from random combinations of electrons and positrons originating from dalitz decays of neutral pions and conversion photons. A Hadron Blind Detector (HBD) is planned to be installed close to the beam pipe inside the PHENIX detector to identify and reject such electrons by looking at Cherenkov light emitted by them. The detector consists of a 50cm long radiator and triple-GEM detector modules with pad readout. The detector is operated in pure-CF4 in a windowless configuration. A CsI photo-cathode is evaporated onto the top GEM of each stack, which converts Cherenkov photons into photoelectrons. The whole detector system covers 3/4 of full azimuth and rapidity of $|$y$|$$<$0.45. In the RHIC year-2006 run, a prototype HBD with limited acceptance was successfully installed, and tested using particles emerged from p+p collisions at $\sqrt{s}$ =200GeV. The basic characteristics of GEMs in the detector and the overall performance of the detector will be presented and discussed. [Preview Abstract] |
Thursday, October 26, 2006 3:36PM - 3:48PM |
BD.00007: Cargo Container Imaging with Gaseous Detectors Tony Forest The gas electron multiplier (GEM) , developed at CERN by Fabio Sauli, represents the latest innovation in micropattern gaseous detectors and has been utilized as a preamplification stage in applications ranging from fundamental physics experiments to medical imaging. Although cargo container inspection systems are currently in place using gamma-rays or X-rays, they are predominantly designed with a resolution to detect contraband. Current imaging systems also suffer from false alarms due to naturally radioactive cargo when radiation portal monitors are used for passive detection of nuclear materials. Detection of small shielded radioactive elements is even more problematic. Idaho State University has been developing a system to image cargo containers in order to detect small shielded radioactive cargo. The possible application of an imaging system with gas electron multiplication will be shown along with preliminary images using gaseous detectors instead of the scintillators currently in use. [Preview Abstract] |
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