7 research outputs found
The scintillating fiber focal plane detector for the use of Kaos as a double arm spectrometer
The upgrade of the Mainz
Mikrotron (MAMI) electron accelerator facility in 2007 which raised the beam energy up to 1.5,GeV, gives the opportunity to study strangeness production channels through electromagnetic process. The Kaon Spectrometer (KAOS) managed by the A1 Collaboration, enables the efficient detection of the kaons associated with strangeness electroproduction. Used as a single arm spectrometer, it can be combined with the existing high-resolution spectrometers for exclusive measurements in the kinematic domain accessible to them.rnrnFor studying hypernuclear production in the ^A Z(e,e'K^+) _Lambda ^A(Z-1) reaction, the detection of electrons at very forward angles is needed. Therefore, the use of KAOS as a double-arm spectrometer for detection of kaons and the electrons at the same time is mandatory. Thus, the electron arm should be provided with a new detector package, with high counting rate capability and high granularity for a good spatial resolution. To this end, a new state-of-the-art scintillating fiber
hodoscope has been developed as an electron detector.rnrnThe hodoscope is made of two planes with a total of 18432 scintillating double-clad fibers of 0.83 mm diameter. Each plane is formed by 72 modules. Each module is formed from a 60deg slanted multi-layer bundle, where 4 fibers of a tilted column are connected to a common read out. The read-out is made with 32 channels of linear array multianode photomultipliers. Signal processing makes use of newly developed double-threshold discriminators. The discriminated signal is sent in parallel to dead-time free time-to-digital modules and to logic modules for triggering purposes.rnrnTwo fiber modules were tested with a carbon beam at GSI, showing a time resolution of 220 ps (FWHM) and a position residual of 270 microm m (FWHM) with a detection efficiency epsilon>99%.rnrnThe characterization of the spectrometer arm has been achieved through simulations calculating the transfer matrix of track parameters from the fiber detector focal plane to the primary vertex.
This transfer matrix has been calculated to first order using beam transport optics and has been checked by quasielastic scattering off a carbon target, where the full kinematics is determined by measuring the recoil proton momentum. The reconstruction accuracy for the emission parameters at the quasielastic vertex was found to be on the order of 0.3 % in first test realized.rnrnThe design, construction process, commissioning, testing and characterization of the fiber hodoscope are presented in this work which has been developed at the Institut für Kernphysik of the Johannes Gutenberg - Universität Mainz.Der Erweiterung des Elektronenbeschleunigers Mainzer Mikrotron (MAMI) im Jahrern2007 auf Strahlenergien bis 1.5~GeV erlaubt es, Kanäle mitrnStrangeness-
Produktion durch elektromagnetische Prozesse zu untersuchen. DasrnKaonenspektrometer KAOS, welches von der A1-Kollaboration betrieben wird,rnermöglicht einen effizienten Nachweis von Kaonen aus Elektroproduktion. AlsrnEinarm-Spektrometer kann es zusammen mit den bestehenden hochauflösendenrnSpektrometern benutzt werden, um exklusive Messungen im zugänglichenrnkinematischen Bereich durchzuführen.rnrnUm die Hyperkernproduktion in der Reaktion ^AZ(e,e'K^+)^A_ Lambda(Z-1) zurnuntersuchen, ist der Nachweis von Elektronen unter sehr kleinenrnVorwärtswinkeln erforderlich. Hierfür ist die Verwendung von KAOS alsrnZweiarm-Spektrometer für den gleichzeitigen Nachweis von Kaonen und Elektronenrnunerläßlich. Daher wurde der Elektronarm mit einem neuen Dektektorsystemrnausgestattet, das hohe Zählraten verarbeiten kann und über eine großernGranularität verfügt, um eine gute Ortsauflösung zu erzielen. Zu diesem Zweckernwurde als Elektrondetektor ein Hodoskop aus szintillierenden Fasernrnentwickelt.rnrnDas Hodoskop besteht
aus zwei Ebenen mit insgesamt 18432 szintillierendenrnDoppelkernfasern mit einem Durchmesser von 0.83 mm. Jede Ebene besteht ausrn72 Modulen. Jedes Modul wiederum besteht aus einem Bündel aus mehreren Lagen,rnwelche um 60deg versetzt sind. Jeweils vier Fasern sind zu einerrngemeinsamen Auslese zusammengefasst. Die Auslese erfolgt über 32-kanaligernLinear-Array-Multianoden-Photomultiplier. Die Signale werden mit einem neurnentwickelten Zwei-Schwellen-Diskriminator verarbeitet und parallelrnweitergeleitet zu totzeitfreien TDC-Modulen und Logikmodulen zurnTriggerzwecken.rnrnTests mit Fasermodulen an einem Kohlenstoffstrahl an der GSI ergaben einernZeitauflösung von etwa 200 ps (FWHM) und eine Ortsauflösung von etwarn270 micro-m bei einer Nachweiseffizienz von epsilon>99%.rnrnDie Beschreibung dieses Spektrometerarms wurde über Simulationenrnerreicht. Die Transfermatrix für die Spurparameter von der Fokalebene desrnFaserdetektors bis zum primären Vertex wurde in erster Ordnung mittelsrnStrahl-transport-Optik
berechnet und überprüft durch eine Messung derrnquasielastischen Streuung an einem Kohlenstofftarget, wobei die Kinematikrnvollständig bestimmt wurde durch Messung des Impulses desrnRückstoßprotons. Bei diesem erste Test wurde festgestellt, dass die Genauigkeitrnfür die Rekonstruktion der Parameter am quasielastischen Vertex etwa 0.3%rnbetragt.rnrnDer Entwurf, der Aufbau, die Inbetriebnahme, die Tests und diernCharakterisierung des Faserhodoskops werden in dieser Arbeit vorgestellt, diernam Institut für Kernphysik an der Johannes Gutenberg-Universität Mainzrndurchgeführt wurde
Status of the BONuS12 Radial Time Projection Chamber
International audiencePart of the experimental program in Hall B of the Jefferson Lab, Virginia, USA is dedicated to studying neutron structure functions using deep inelastic scattering on nuclei. For this purpose, the BONuS12 experiment will detect low momentum recoil protons in coincidence with scattered electrons. The protons will be detected by a second-generation Radial Time Projection Chamber (RTPC) using triple Gas Electron Multiplier foils for amplification while the scattered electrons will be detected by the CLAS12 spectrometer installed in Hall B. The following article presents the status of the BONuS12 RTPC detector that will take data within the next 2 years. The main improvements made from the previous BONuS RTPC: the new electronics and mounting process are presented. We also detail some aspect of the gas simulation
Revealing the structure of light pseudoscalar mesons at the electron-ion collider
How the bulk of the Universe's visible mass emerges and how it is manifest in the existence and properties of hadrons are profound questions that probe into the heart of strongly interacting matter. Paradoxically, the lightest pseudoscalar mesons appear to be the key to the further understanding of the emergent mass and structure mechanisms. These mesons, namely the pion and kaon, are the Nambu-Goldstone boson modes of QCD. Unravelling their partonic structure and the interplay between emergent and Higgs-boson mass mechanisms is a common goal of three interdependent approaches -- continuum QCD phenomenology, lattice-regularised QCD, and the global analysis of parton distributions -- linked to experimental measurements of hadron structure. Experimentally, the foreseen electron-ion collider will enable a revolution in our ability to study pion and kaon structure, accessed by scattering from the ``meson cloud'' of the proton through the Sullivan process. With the goal of enabling a suite of measurements that can address these questions, we examine key reactions to identify the critical detector system requirements needed to map tagged pion and kaon cross sections over a wide range of kinematics. The excellent prospects for extracting pion structure function and form factor data are shown, and similar prospects for kaon structure are discussed in the context of a worldwide programme. Successful completion of the programme outlined herein will deliver deep, far-reaching insights into the emergence of pions and kaons, their properties, and their role as QCD's Goldstone boson modes
Kaon Tagging at 0° Scattering Angle for High-Resolution Decay-Pion Spectroscopy
At the Mainz Microtron hypernuclei can be studied by (e,e’K) reactions. By detecting the kaon which is emitted in forward direction, with the KAOS spectrometer placed at 0° scattering angle, reactions involving open strangeness production are tagged. High-resolution magnetic spectrometers are then used to coincidentally detect the monoenergetic decay-pions from mesonic two-body weak decays of light hypernuclei at rest.
As a pioneering experiment has confirmed, the KAOS spectrometer is exposed to a large flux of background particles, mostly positrons from bremsstrahlung pair production. In order to increase the effciency of kaon identification the KAOS spectrometer was modified to suppress background particles at the cost of a high momentum resolution, which is less important for this experiment. This was achieved by placing up to 14 cm of lead absorbers in front of the detectors, in which positrons are blocked by forming electromagnetic showers while the effect on kaons is limited. An additional time-of-flight wall and a new threshold Čerenkov detector help to increase the detection effciency of kaons
Kaon Tagging at 0° Scattering Angle for High-Resolution Decay-Pion Spectroscopy
At the Mainz Microtron hypernuclei can be studied by (e,e’K) reactions. By detecting the kaon which is emitted in forward direction, with the KAOS spectrometer placed at 0° scattering angle, reactions involving open strangeness production are tagged. High-resolution magnetic spectrometers are then used to coincidentally detect the monoenergetic decay-pions from mesonic two-body weak decays of light hypernuclei at rest.
As a pioneering experiment has confirmed, the KAOS spectrometer is exposed to a large flux of background particles, mostly positrons from bremsstrahlung pair production. In order to increase the effciency of kaon identification the KAOS spectrometer was modified to suppress background particles at the cost of a high momentum resolution, which is less important for this experiment. This was achieved by placing up to 14 cm of lead absorbers in front of the detectors, in which positrons are blocked by forming electromagnetic showers while the effect on kaons is limited. An additional time-of-flight wall and a new threshold Čerenkov detector help to increase the detection effciency of kaons