Search

In the first production run of the WASA experiment at COSY, the eta decay into three neutral pions was measured in proton-proton interactions at a proton beam kinetic energy of 1.4 GeV. The Dalitz ...

For the operation of the WASA (wide angle shower apparatus) detector system at the Cooler Synchrotron COSY in Forschungszentrum Julich (FZJ) a new DAQ system has been developed, which conforms to the third generation of the DAQ systems at COSY. This comprises new readout electronics based on an optimized parallel bus with LVDS technology and FPGA-controlled event and buffer management. The new DAQ system has been successfully commissioned in autumn 2006. Further developments aiming at performance optimizations are in progress. The implementation status is presented and performance issues are discussed.

The polarized internal target for the ANKE experiment at the Cooler Synchrotron COSY of the Forschungszentrum Julich utilizes a polarized atomic beam source to feed a storage cell with polarized hydrogen or deuterium atoms. The nuclear polarization is measured with a Lamb-shift polarimeter. For common control of the two systems, industrial equipment was selected providing reliable, long-term support and remote control of the target as well as measurement and optimization of its operating parameters. The interlock system has been implemented on the basis of SIEMENS SIMATIC S7-300 family of programmable logic controllers. In order to unify the interfacing to the control computer, all front-end equipment is connected via the PROFIBUS DP fieldbus. The process control software was implemented using the Windows-based WinCC toolkit from SIEMENS. The variety of components, to be controlled, and the logical structure of the control and interlock system are described. Finally, a number of applications derived from the present development to other, new installations are briefly mentioned.

Today, most slow control systems for physics experiments at Forschungszentrum Ju/spl uml/lich are implemented with Programmable Logic Controller (PLC) technology and fieldbus systems. In many cases, even deterministic response is required from the PLCs. This raises the question about the real-time performance that can be expected from a PLC. Response-time measurements of Simatic/spl reg/ PLCs-manufactured by the world market leader Siemens-are presented. Influence of program structure and hardware configuration on performance and deterministic behavior of a PLC is discussed.

A study of the deuteron breakup reaction $pd \to (pp)n$ with forward emission of a fast proton pair with small excitation energy $E_{pp}, Comment: 17 pages including 6 figures and 1 table v2: minor changes; v3: minor change of author list; v4: changes in accordance with referee remarks

A stack of annular detectors made of high purity germanium was used to measure p + d → 3 He + π 0 and p + d → 3 H + π + differential and total cross sections at beam momenta from 900 to 1050 MeV/c. The total cross sections are consistent with ∆-excitation. The differential data consist of two components. One corresponds to large momentum transfer from the projectile to the pion, the other to small momentum transfer. The former shows an independence of the slope as function of the momentum transfer t (scaling). The scale parameter is different for π + and π 0 emission which violates isospin symmetry. The second component which is almost isotropic is in agreement with isospin symmetry. It is approximately a quarter of the total yield in the ∆ resonance region.  2002 Elsevier Science B.V. All rights reserved.

We performed a series of experiments employing the two pion production reactions p + d → 3 He + π 0 and p + d → 3 H + π + . The two isopin related reactions differ by a Clebsch Gordan coefficient of 2. We searched for deviations in this ratio in complete angular distributions in the range of the Δ excitation as well as in the vicinity of the η production threshold.

Using Java for real world I/O requires its availability in real-time (RT) systems. It is widely accepted that in a plain Java environment, RT characteristics get lost and the required programming interfaces are missing. So there are several ongoing standardization efforts for RT Java. An essential aspect (also important for non-RT systems) is the access to external I/Os. The Siemens product Java for process control (JFPC), which is based on the ideas of OLE for process control (OPC) addresses this aspect. It is available under the proprietary RT kernel RMOS and under Windows NT. Forschungszentrum Julich developed different JFPC providers in order to access industrial components via PROFIBUS DP using an experimental version of JFPC under Linux. The paper presents the status of the different standardization efforts for RT Java and the key features of JFPC. It describes the implementation of a JFPC provider for PROFIBUS DP and shows how it can be used to access industrial sensors and actuators. Experiences and performance results are discussed.

In order to provide the experimental tools necessary to carry out few-nucleon reaction studies with polarized beams and targets at the medium energy storage ring COSY at Julich, our group is currently developing a polarized internal storage-cell gas target for first use at the magnetic spectrometer ANKE. In this paper we give an overview about currently relevant aspects of the polarized deuteron breakup experiment.

Total and differential cross sections for the reactions p + d → 3He + m 0 with m=π, η and p + d → 3H+π+ were measured with the GEM detector at COSY for beam momenta between threshold and the maximum of the corresponding baryon resonance. For both reactions a strong forward-backward asymmetry was found. The data were compared with model calculations. The aspect of isospin symmetry breaking is studied.

A new two-dimensional position-sensitive detector system for small-angle neutron scattering experiments is under development. It is based on a 60/spl times/60 cm/sup 2/ large /sup 6/Li-glass scintillator for the neutron capture and dispersion of the emitted light on an array of photomultiplier tubes for the derivation of the event position. For subthermal neutrons of 8 /spl Aring/, an efficiency of 96% and a spatial resolution of 8 mm are to be achieved. Major improvements have been made in the signal- and data-processing branch, which aims at an electronic dead time of 1 /spl mu/s. A fast digitalization method using free-running analog-to-digital converters for each photomultiplier combined with field-programmable gate arrays for a parallel event detection in all channels has been applied. A subsequent farm of up to 16 floating-point digital signal processors is used to provide enough computing power for an improved reconstruction of the event position according to a maximum likelihood method.

The production of neutral and charged pions as well as eta mesons is studied in the Delta and N* resonance region, respectively. Heavy A=3 recoils were measured with the GEM detector. The differential cross sections covering the full angular range are compared with model calculations., Comment: 4 pages, latex, 4 figures, talk presented at the XVIIth European Conference on Few-Body Problems in Physics, Evora, Portugal, September 2000; to be published in Nucl. Phys. A

ANKE is a new experimental facility for the spectroscopy of products from proton-induced reactions on internal targets. It has recently been implemented in the accelerator ring of the cooler synchrotron COSY of the Forschungszentrum Julich (FZ-Julich), Germany. The device consists of three dipole magnets, various target installations and dedicated detection systems. It will enable a variety of hadron-physics experiments like meson production in elementary proton–nucleon processes and studies of medium modifications in proton–nucleus interactions.

The database system for the storage and retrieval of experimental and technical data at TEXTOR-94 has to be revised. A new database has to be developed, which complies with future performance and multiplatform requirements. The concept, to be presented here, is based on the commercial object database Objectivity. Objectivity allows a flexible object oriented data design and is able to cope with the large amount of data, which is expected to be about 1 TByte per year. Furthermore, it offers the possibility of data distribution over several hosts. Thus, parallel data storage from the frontend to the database is possible and can be used to achieve the required storage performance of 200 MByte per min. In order to store configurational and experimental data, an object model is under design. It is aimed at describing the device specific information and the acquired data in a common way such that different aproaches for data access may be applied. There are several methods forseen for remote access. In addition to the C++ and Java interfaces already included in Objectivity/DB, CORBA and socket based C interfaces are currently under development. This could also allow an access by non-supported platforms and enable existing legacy applications an integration of the database for storage and retrieval of data by a minimum of code changes. (C) 2000 Elsevier Science S.A. All rights reserved.

We present a method to determine precisely the absolute momentum of the external proton beam from the Julich Cooler Synchrotron COSY near 1930 MeV /c . In the pp → d π + reaction at 1930.477 MeV /c incident beam momentum, the forward going pions ( θ c.m. =0° ) and the backward going deuterons ( θ c.m. =180° ) have the same laboratory momentum. Such coincident pion–deuteron events are detected in the focal plane of the magnetic spectrometer BIG KARL located at θ lab =0° . Using the nearly linear dependence of the difference between the measured pion and deuteron momenta as a function of the proton beam momentum, the absolute momentum of the external proton beam from COSY near 1930 MeV /c was determined with a precision of 5.2×10 −5 .

A stack of annular detectors made of high-purity germanium was developed. The detectors are position sensitive with radial structures. The first one (“Quirl”) is double-sided position sensitive defining 40 000 pixels, the following three (E1, E2 and E3) have 32 wedges each. The Quirl acts as tracker while the other three act as calorimeter. The stack was successfully operated in meson production reactions close to threshold.

Differential and total cross sections of the p + p → π+ + d reaction close to threshold were measured employing a magnetic spectrograph with track reconstruction, a very thin liquid hydrogen target and an accelerated proton beam with high phase space density. The data resolve a previous discrepancy between the n + p → π0 + d and the π+ + d → 2p reaction close to threshold indicating that isospin symmetry may be broken in the s-wave part of the cross section.

At the Julich Cooler Synchrotron COSY several experiments are running based on a modular, flexible system design in hardware and software. Future data acquisition experiments should use PC-technologies as far as possible. For the intelligent units initially passive backplanes with Single Bord Computers (SBCs) have been chosen as defined by the PCI Industrial Computer Manufacturing Group (PICMG). For future applications the CompactPCI is considered which combines the IBM PC electrical and software standards with the Eurocard mechanical standards. Connection of the front-end modular systems (CAMAC, VME, FASTBUS) is performed by transparent controllers with PCI compliant interfaces, already available on the market or home made developments. As far as operating systems are concerned UNIX like systems are used. An object oriented, client-server based Experiment Messaging System (EMS) establishes the communication on the application layer between the experiment control, the event builder and different front-end systems. The design criteria for the second generation DAQ-Systems, a first experiment layout, interconnectivity questions and necessary component developments will be described, as well as the problems we have found turning a PC into a diskless system. Important results of performance measurements concerning the DAQ requirements will be given.

The ATM technology for high speed serial transmission provides a new quality of communication by introducing novel features in a LAN environment, especially support of real time communication, of both LAN and WAN communication and of multimedia streams. In order to evaluate ATM for future DAQ systems and remote control systems as well as for a high speed picture archiving and communications system for medical images, Forschungszentrum Julich has build up a pilot system for the evaluation of ATM and standard low cost multimedia systems. It is a heterogeneous multivendor system containing a variety of switches and desktop solutions, employing different protocol options of ATM. The tests conducted in the pilot system revealed major difficulties regarding stability, interoperability and performance. The paper presents motivations, layout and results of the pilot system. Discussion of results concentrates on performance issues relevant for realistic applications, e.g., connection to a RAID system via NFS over ATM.

At the Julich Cooler Synchrotron, COSY, the magnetic spectrometer ANKE (Apparatus for Studies of Nucleon and Kaon Ejectils) is installed. Reaction products emitted by an internal target in the forward direction are measured. About 11000 channels are read out. This requirement justified the design of a VLSI based readout system. For this, an analog chip (RAL 118)-a low power high speed eight channel amplifier and discriminator-is used. Digital delay, zero suppression and address encoding are performed by the digital chip RAL 111 from the Rutherford Appleton Laboratory. A scalable and flexible array of chamber mounted front end boards may be adapted to instrument detectors of any size. Readout is performed by serializing hit addresses over a high speed optical link to a CAMAC readout module which serves for additional data reduction, subevent building and a number of test functions. Furthermore, subevent data are transferred using a front panel ECLbus (FERAbus*) to a crate controller with PCI-interface. An industrial PC with diskless UNIX-compatible operating system (NetBSD) is responsible for controlling the CAMAC crate, processing the event data and connecting to a central event builder.

The GEM detector, a hybrid system consisting of the Germanium Wall and the magnetic spectrometer BIG KARL, was developed to investigate meson production and meson-nucleus interaction with cooled external proton beams from the COSY accelerator at Julich. The Germanium Wall is a stack of up to four annular position-sensitive semiconductor detectors made from high-purity germanium. Its special structure allows experiments with high counting rates. Design features and results from first test runs with the uncooled COSY beam are presented.

For the first time the reaction pp → dπ + was measured close to threshold. A magnetic spectrometer (3Q2DQ) which allows ray tracing was applied to detect the recoiling deuterons and reconstruct their momenta. The measured anisotropies are between 0.008 and 0.29, indicating the importance of p -wave amplitudes even close to threshold. The presented data support the validity of isospin and time reversal symmetries.

The {ital p}+{ital p}{r_arrow}{pi}{sup +}+{ital d} reaction is studied at excess energies between 0.275 and 3.86 MeV. Differential and total cross section were measured employing a magnetic spectrometer with nearly 4{pi} acceptance in the center of mass system. The measured anisotropies between 0.008 and 0.29 indicate that the {ital p} wave is not negligible even so close to threshold. The data are compared to other data offering no evidence for charge symmetry breaking or time reversal violation. The {ital s}-wave and {ital p}-wave contributions at threshold are deduced. {copyright} {ital 1996 The American Physical Society.}

The COSY-11 installation is an internal experiment at the cooler synchrotron and storage ring COSY Julich. It has been designed for full geometrical acceptance close to threshold for meson production studies, especially in the 1 GeV/c2 mass range. The experimental setup makes use of a regular C-type COSY dipole magnet, following a cluster target, to separate reaction products from the beam and to analyze their momenta, thus allowing the observation of charged reaction products at small angles with beam energies close to threshold. Resonances will be identified by missing mass reconstructions from measured four-momenta of two outgoing protons in the predominantly studied pp → ppX reaction. In addition, charged mesons either produced directly or from decays of X will be detected. The different components of the experimental facility are presented.

We plan to investigate sub-threshold K+ production in proton bombardment of atomic nuclei in order to study the reaction mechanism through a measurement of the double differential cross section and of K+ p and K+ d coincidences. The status of the theoretical studies is summarized, and the spectrometer to be installed in the COSY ring is briefly described.

For the KFA Julich cooler synchrotron COSY a general data acquisition system was developed. Its architecture is based on available standards (VME, FASTBUS, CAMAC, VICbus) and UNIX workstations forming a distributed processor system. Based on this hardware a flexible and modular data acquisition software was designed allowing the configuration of various experiment arrangements. The software design for run control is arranged according to a client server connectivity model as well as to an object oriented structure. It is logically based on MAP/MMS (ISO9506), a powerful application layer protocol for distributed automation systems in industry. In our application servers are implemented on the mProcessor controller boards at the frontend. On the workstation side the experiment control client consists of dedicated processes with access to the configurable experiment data base. The user interface is realized by OSF/Motif. Established software standards for online data analysis high energy physics are employed. We discuss the most important design decisions mainly focusing on the software aspects. >

The motivation for the experiment is shortly discussed. In contrast to the classical method of π− absorption we will produce a π− directly in a bound state employing the COSY Julich proton beam. A special choice of the underlying kinematics favors the cross section. The considerations from these constraints for the detector will be given together with its status. An outlook is given on further possible activities.

For nuclear physics experiments at the Julich Cooler Synchrotron COSY, a data acquisition system is under development. With this background, and in order to enhance existing CAMAC systems, an intelligent CAMAC crate controller with CC-A2 functionality was developed. The main enhancement is the replacement of the Branch Highway with a new standard of intercrate connection: the VICbus. The other highlights are the optional use of Motorola 68030 microprocessor as CAMAC list-processor and optimization of CAMAC block transfers, optional Ethernet or Cheapernet connection. >

A three-level data processing and acquisition system is being developed. Signals from various detector arrangements are digitized and preprocessed by CAMAC, FASTBUS, and VME modules. A multiprocessor system based on VMEbus is used for event building, data recording, and buffered data transfer to the host computer. All crates are connected by parallel VICbus. For this, an intelligent CAMAC rate controller with VICbus is under development. Microcomputer-based VME modules are equipped with CPUs of the 680X0 family, working under the OS-9 real-time operating system. The data acquisition system is mainly based on commercially available modules. >

A discussion is presented of the performance of the MAP protocol profile, which is a typical example of a layered OSI protocol profile in a local area network environment, and the results of a number of measurements are given. Static aspects of performance, which are dominated by the implementation, are covered. The main issue is the examination of dynamic aspects, which are dominated by the transport layer. >

A compact and flexible low noise control- and readout-system has been developed for a X-ray pnCCD operation. The pnCCD is a new type of CCD originally developed for applications in space for X-ray astronomy. It is designed to perform extremely fast, high resolution spectroscopy of photons in the soft X-ray and infrared region with high efficiency. All interesting parameters of the new readout system like pulse-sequencing and power-up and -down are completely controlled by a front-end system with the help of hardwired interpreters getting their programs from a supervising PC. For adaptation of other CCD devices and optimisation, these parameters can be changed interactively by the PC operator. Coupling of the front-end system to the computer is done via a fiber optic link with PCI bus-interface. A menu driven, interactive program system under Linux serves for generation of timing sequences, experiment setup, visualisation and data storage. The system allows an image repetition rate of up to 220 frames/s which is limited only by the pnCCD readout speed.

A RAM based FPGA can be configured with a bootimage from a local proprietary flash prom, by a JTAG adapter hooked to a local PC interface or any another component, which copes with one of the FPGA configuration protocols. The development of the FPGA code as well as updates of the bootimage can be done by a JTAG adapter. On the basis of a PCB developed in the ZEL we show a first step towards an embedded JTAG adapter for TCP/IP-Ethernet.

A high resolution time to digital conversion (TDC) module has been developed for the time-stamping of plastics scintillator signals in the WASA detector system. The module is designed in 6U Eurocard form factor for a proprietary optimized backplane bus with LVDS technology. It provides 64 channels and is based on the GPX ASIC from acam-messelectronic gmbh. In the selected mode the GPX has 8 input channels with a resolution up to 81 ps. Design issues and preliminary results of the performance of the module are discussed.

For the DAQ in hadron physics experiments at the 3.7 GeV storage ring COSY in FZ Julich a new generation of readout electronics has been implemented. High performance and cost efficiency is achieved by the definition of an optimized parallel backplane bus in the frontend, based on LVDS technology with 80 Mbytes/s nominal throughput. For the readout of the digitizing modules a systemcontroller module has been developed which operates as master of the backplane bus and transfers the acquired data to the upper layers of the DAQ system via optical links. The systemcontroller is based on the Virtex-II Pro Gtsystem on a chipLt-FPGA running embedded Linux on its internal PowerPC CPU. The framework of the third generation of DAQ at COSY is introduced and the architecture of the systemcontroller is described. Measurement-results of the communication link performance are presented

Wide angle shower apparatus (WASA), a detector for charged and neutral particles is currently operated at the CELSIUS storage ring by TSL, Uppsala University. It shall be transferred to the Cooler Synchrotron (COSY) at Forschungszentrum Julich (FZJ) after the anticipated shutdown of CELSIUS in summer 2005. For operation in Julich a new DAQ system is being developed, which conforms to the third generation of the DAQ systems at COSY. This comprises new readout electronics based on an optimized parallel bus with LVDS technology and FPGA-controlled event and buffer management, a synchronization system and a high speed optical link to the readout computer. Architecture of the new DAQ system and the technical issues of subsystems are presented.

To improve existing experiments at COSY a new DAQ system is currently under development. It is also well suited to the requirements of WASA at COSY after its transfer from CELSIUS. The DAQ modules are scattered to about 10..20 crates and are able to digitize and store several thousands events before a computer engagement is required. Therefore we need a purely hardware based synchronisation system. The synchronisation system consists of one master module and several output modules housed in a proprietary LVDS crate. It communicates over point to point links with the crate controllers

During the upgrade of the small-angle neutron scattering instrument KWS-1 at the research reactor FRJ-2, the 15-yr-old detector system has been replaced. While the Anger camera-based concept of the detector remained unchanged, the signal and data processing branch has been completely revised. Because of higher count rate requirements, a highly configurable parallel readout electronics has been developed aiming at counting rates of several hundred kilohertz. The whole detector system has been recently installed at KWS-1 and measurements to study the system performance have been carried out. The linearity and spatial resolution of the new detector have been determined by an analysis of an acquired image taken with a hole diaphragm in front of the scintillator. The overall system dead time has been measured by comparing the detector count rates at several scattering intensities to the count rates achieved with a fission chamber. Finally, scattering patterns of well-known samples have been taken in order to demonstrate the quality of the acquired images.

For the ANKE spectrometer at the Cooler Synchrotron COSY-Julich, a vertex detector is under development. Double-sided structured silicon-strip detectors with a thickness from 65 /spl mu/m to 5500 /spl mu/m are used in a telescope-like structure. They allow the /spl Delta/E/E-identification of low energy spectator protons and therefore the use of deuterium as an effective neutron target. As frontend chip the VA32TA2 has been selected. They are connected to both sides of the detector. Because half of them, together with their readout electronics, needs to be operated at the bias voltage of the detectors (10-1000 V), a special system for multiplexed chip readout has been developed. It provides two ADCs per detector, one per each side, and allows for the configuration of all analog voltages by DACs and control timings by programmable sequence generators.

PROFIBUS, being a national German (DIN 19245) and an European (EN 50170) standard, has become the most widely accepted modern fieldbus technology in Europe. It is expected to rake a similar role on the world market, since the IEC standardisation efforts for a common international fieldbus failed recently. A major reason for its success is the technological and functional scalability based on a common core. Now, a wide range of PLCs as well as low cost process I/O is available (also from leading manufacturers like Siemens) which enable easy interfacing. ZEL, the central electronics facility of Forschungszentrum Julich, has decided to use predominantly industrial components (PLCs, I/Os, etc.) in the front end of slow control systems for physics experiments. Interfacing of these devices is accomplished by PROFIBUS controllers, that have been developed for PCI and CompactPCI with device drivers for Linux and LynxOS. Front end PROFIBUS controllers have been developed for integrating dedicated devices. On the base of two case studies-a nuclear experiment and a neutron scattering experiment-the paper describes this approach. Design of the PROFIBUS hardware and software as well as performance results are presented.

Based on thorough experiences with distributed experiment control systems and fieldbus applications we are developing a control system especially targeted at neutron scattering experiments. Main characteristic is that front-end equipment and control machine are coupled by the industrial fieldbus standard PROFIBUS (DIN 19245, EN 50170). This significantly reduces the amount of cabling necessary. Further, it provides the proven error recovery and diagnostic features of an industrial fieldbus to the experiment control area. Front-end equipment comprises industrially available components like SIEMENS "ET200" peripheral devices, PLCs and encoders (Heidenhain). For cost-sensitive stepper motor control a low-end motor controller from University of Gottingen is being interfaced directly to PROFIBUS. Widely available SIEMENS-SMP equipment can be coupled by a PROFIBUS-SMP interface developed at our institute. The controlling master is an Intel PC running a diskless Linux version, equipped with a home-made PROFIBUS controller in CompactPCI formfactor. As software interface to control applications the TACO framework developed at ESRF is employed. "Device servers" in terms of the TACO client-server architecture have been created, allowing access to the functions of the control system at different levels, from raw PROFIBUS accesses up to complete motor control with position encoder feedback.

A stack of annular detectors made of high-purity germanium was used to measure $p + d\to\noindent {^3{\rm He}} + \pi^0$ and $p + d\to{^3{\rm H}} + \pi^ + $ differential and total cross-sections at beam momenta from 900 MeV/c to 1050 MeV/c. The total cross-sections are consistent with $\Delta$ -excitation. The differential data consist of two components. One corresponds to large momentum transfer from the projectile to the pion, the other to small momentum transfer. The former shows an independence of the slope as a function of the momentum transfer t (scaling). The scale parameter is different for $\pi^ + $ and $\pi^0$ emission which violates isospin symmetry. The second component which is almost isotropic is in agreement with isospin symmetry. It is approximately a quarter of the total yield in the $\Delta$ -resonance region.

A stack of annular detectors made of high-purity germanium was used to measure p + d → 3He + π 0 and p + d → 3H + π + differential and total cross-sections at beam momenta from 900 MeV/c to 1050 MeV/c. The total cross-sections are consistent with Δ-excitation. The differential data consist of two components. One corresponds to large momentum transfer from the projectile to the pion, the other to small momentum transfer. The former shows an independence of the slope as a function of the momentum transfer t (scaling). The scale parameter is different for π + and π 0 emission which violates isospin symmetry. The second component which is almost isotropic is in agreement with isospin symmetry. It is approximately a quarter of the total yield in the Δ-resonance region.