J.A. Garzón

Performance of the Low-Jitter High-Gain/Bandwidth Front-End Electronics of the HADES tRPC Wall

A front-end electronics (FEE) chain for accurate time measurements has been developed for the new Resistive Plate Chamber (RPC)-based Time-of-Flight (TOF) wall of the High Acceptance Di-Electron Spectrometer (HADES). The wall covers an area of around 8 m2, divided in 6 sectors. In total, 1122 4-gap timing RPC cells are read-out by 2244 time and charge sensitive channels. The FEE chain consists of 2 custom-made boards: a 4-channel DaughterBOard (DBO) and a 32-channel MotherBOard (MBO). The DBO uses a fast 2 GHz amplifier feeding a dual high-speed discriminator. The time and charge information are encoded, respectively, in the leading edge and the width of an LVDS signal. Each MBO houses up to 8 DBOs providing them regulated voltage supply, threshold values via DACs, test signals and, additionally, routing out a signal proportional to the channel multiplicity needed for a 1st level trigger decision. The MBO delivers LVDS signals to a multi-purpose Trigger Readout Board (TRB) for data acquisition. The FEE allows achieving a system resolution around 75 ps fulfilling comfortably the requirements of the HADES upgrade .

Front-End electronics development for the new Resistive Plate Chamber detector of HADES

In this paper we present the new RPC wall, which is being installed in the HADES detector at Darmstadt GSI. It consists of time-of-flight (TOF) detectors used for both particle identification and triggering. Resistive Plate Chamber (RPC) detectors are becoming widely used because of their excellent TOF capabilities and reduced cost. The wall will contain 1024 RPC modules, covering an active area of around 7 m2, replacing the old TOFino detector at the low polar angle region. The excellent TOF and good charge resolutions of the new detector will improve the time resolution to values better than 100 ps. The Front-End electronics for the readout of the RPC signals is implemented with two types of boards to satisfy the space constraints: the Daughterboards are small boards that amplify the low level signals from the detector and provide fast discriminators for time of flight measurements, as well as an integrator for charge measurements. The Motherboard provides stable DC voltages and a stable ground, threshold DACs for the discriminators, multiplicity trigger and impedance matched paths for transfer of time window signals that contain information about time and charge. These signals are sent to a custom TDC board that label each event and send data through Ethernet to be conveniently stored.

Conductivity and charge depletion aging of resistive electrodes for high rate RPCs

Development of new electrodes is a key element for the improvement of high rate Resistive Plate Chambers (RPC). In the particular case of resistive electrodes, the fabrication of these elements is a challenging problem from a material science point of view. The combination of resistivity, permittivity and stability requirements is really hard to satisfy for any known material. Only a few materials have been found to be suitable for fabrication of resistive plates. In this work, we have carried out electrical characterizations of some of the materials that are currently used in RPCs or are solid candidates to be used as resistive plates in high rate RPCs. As a result, we have found strong evidences that ion conduction processes under moderate to high electric fields are able to drift high amounts of charge which allow to understand the degradation nature of the involved processes.

Performance of the HADES-TOF RPC wall in a Au + Au beam at 1.25 AGeV

In this work we present results concerning in beam operation of the new Resistive Plate Chamber (RPC) Time of Flight (TOF) wall for the High Acceptance DiElectron Spectrometer (HADES) at the Society for Heavy Ion Research (GSI), Darmstadt, Germany. The new RPC-TOF wall, fully integrated in the spectrometer, has been successfully operated under final conditions corresponding to collision of Au + Au at 1.25 AGeV.Results confirm an intrinsic uniform average time response of about 66 ps σ along with an intrinsic average longitudinal position resolution better than 8 mm σ, for particles with a momentum above 300 MeV/c selected with the tracking system of the spectrometer. The multihit capability of the system has also been investigated showing a slight degradation of time resolution when particles hit the detector at neighbouring cells. The matching efficiency of the RPC-TOF wall is quite homogeneous over the whole area showing an average value of about 95%

Performance of the HADES-TOF RPC wall in a Au-Au beam

In this work we present results concerning in beam operation of the new Resistive Plate Chamber (RPC) Time of Flight (TOF) wall for the High-Acceptance DiEl ectron Spectrometer (HADES) spectrometer at GSI. The new RPC-TOF wall, fully integrated in the spectrometer, has been successfully operated under final conditions corresponding to collision of Au + AU @ 1.25 GeV. Results confirm an uniform average time response below 80 ps σ along with an average longitudinal position resolution better than 12 mm σ . The multihit capability of the system has also been investigated showing a slight degradation of time reso lution when particles hit the detector at neighbouring cells, which demonstrates the multihit capability of the concept (individually electrically shielded RPCs).

Analysis of the space-time microstructure of cosmic ray air showers using the HADES RPC TOF wall

Cosmic rays have been studied, since they were discovered one century ago, with a very broad spectrum of detectors and techniques. However, never the properties of the extended air showers (EAS) induced by high energy primary cosmic rays had been analysed at the Earth surface with a high granularity detector and a time resolution at the 0.1 ns scale. The commissioning of the timing RPC (Resistive Plate Chambers) time of flight wall of the HADES spectrometer with cosmic rays, at the GSI (Darmstadt, Germany), opened up that opportunity. During the last months of 2009, more than 500 millions of cosmic ray events were recorded by a stack of two RPC modules, of about 1.25 m2 each, able to measure swarms of up to ~ 100 particles with a time resolution better than 100 ps. In this document it is demonstrated how such a relative small two-plane, high-granularity timing RPC setup may provide significant information about the properties of the shower and hence about the primary cosmic ray properties.

Low noise Power Supply System for the Front-End Electronics of the HADES RPC detector

This contribution presents the Power Supply System designed for the Front-End Electronics of the HADES RPC detector, installed at GSI (Darmstadt, Germany). The system is designed as a distributed architecture and contains custom Low Voltage boards based on DC-DC switching converters to obtain high efficiency and reduce spacing. The switching converters are conveniently filtered to reduce EMI, obtaining very low output noise. Experimental results with the RPC detector prove that the low noise levels achieved at the output of the switching converters behave as good as laboratory power supplies, not producing any worsening in the response of the Front-End Electronics.

Analysis of the front structure of EAS with the HADES tRPC wall

Alberto Blancoa, Daniel Belverb, Pablo Cabanelasb, Jose Diazc, Paulo Fontea,d , Juan A. Garzonb, Alejandro Gilc, Diego Gonzalez-Diaze, Wolfgang Koenig f , Georgy Kornakov∗a,b, Burkhard Kolb f , Luis Lopesa, Marek Palkag, Americo Pereiraa, Michael Traxler f , Peter Zumbruch f aLaboratorio de Instrumentacao e Fisica Experimental de Particulas, LIP, Coimbra, Portugal bLabCAF, Universidade de Santiago de Compostela, USC, Santiago de Compostela, Spain cInstituto de Fisica Corpuscular, IFIC, Valencia, Spain dISEC-Instituto Superior de Engenharia de Coimbra, Coimbra, Portugal eLaboratorio de Fisica Nuclear y Altas Energias, Universidad de Zaragoza, Zaragoza, Spain f GSI Helmholtzzentrum fur Schwerionenforschung GmbH, Darmstadt, Germany gSmoluchowski Institute of Physics, Jagiellonian University of Cracow, Poland

Control and Monitoring System for the HADES RPC detector

The Control and Monitoring System designed for the Front-End Electronics of the HADES RPC detector, installed at GSI Helmholtz Centre for Heavy Ion Research GmbH (Darmstadt, Germany), is described. This new detector for the Time-of-Flight detection system of HADES contains 1116 electrically shielded RPC cells and covers an active area of about 8m2. The slow control system controls/monitors about 6500 variables and is being implemented using the Experimental Physics and Industrial Control System (EPICS) Software tool kit. A MEDM graphical interface is being developed for the client system. The Control and Monitoring System attends four different systems: Front-End Electronics, Low Voltage System, Detector and Gas System. Each system communicates the control/monitoring system via a different and independent hardware interface, but the user interacts with a common software application that interfaces all systems. The Front-End Electronics has 2232 electronic channels that require threshold setting of the LTC2620 chips via Serial Peripheral Interface (SPI). The Low Voltage System monitors currents and voltages via 1-Wire bus. The detector is equipped with controllable switches and the Gas System requires the control and monitoring for the gas flows. Temperature of all systems is sensed using the DS18B20 chip. The Data Acquisition System interacts with the main part of the systems via system-on-chip ETRAX computers (equipped with Ethernet port) that run EPICS IO servers over an embedded LINUX kernel.

Front-end electronics of the HADES RPC wall: Full sector test

Results from the test of a full sector of the front-end electronics developed for the Resistive Plate Chamber of HADES are presented. This new detector for the Time-of-Flight detection system contains 1116 electrically shielded RPC cells read by 2232 electronic channels, covering a total active area of nearly 8 m2. The front-end electronics consist of custom-made boards that allow achieving a time resolution better than 100 ps to fulfill the new HADES requirements.