CAMAC Modules Research Articles

32-Channel All-in-One CAMAC Module as a Basic Element of Anode Wire Read-out Systems for Proportional Chambers

A special feature of the system is the integration of the amplifying section, signal delay unit, and digital section for the data outputting to computer into a common АДД-32 module (CAMAC). The 1-M-size АДД-32 module contains the electronics for 32 wires, which makes it possible to place up to 672 data channels in the CAMAC crate with a standard bus. To amplify signals, Ampl 8.3 eight-channel microcircuits are used. The output logic signals are delayed by 9-channel IDT72421 FIFO microcircuits enabling us to obtain a total signal delay of up to hundreds of microseconds and longer. The digital section of the system is based on ALTERA programmable logic arrays. At present, this system with a total of 576-channels is used in the PIBETA experiment to study rare pion decays on the PSI accelerator (Switzerland).

Data acquisition system for MEGHA

A multi-channel data acquisition system has been commissioned for the Charissa “MEGHA” detector array. It is designed to read multiparameter events where there are many potential channels (320) but where only a fraction of these are active in any typical event. Custom-built pre- and main amplifiers process the amplitude (energy) signal from each detector and the system records both amplitude and time of arrival for each signal within an event. The signal amplitude is converted to time using the standard Wilkinson technique and then combined with its time of arrival into a single time trace. These traces are converted by multi-hit TDCs, which only convert the active channels and thus reduce the processing load. Additional custom-built CAMAC modules organise the TDC output into a suitable form for storage and transmission to a network of processor terminals over standard ethernet. This paper presents a description of the data acquisition system from preamplifier through to final storage in a VME-based system and subsequent distribution to a network of Sun terminals over ethernet. The system performance is illustrated with results from heavy-ion elastic scattering recorded with position sensitive strip detectors.

Digital pulse processing: new possibilities in nuclear spectroscopy

Digital pulse processing is a signal processing technique in which detector (preamplifier output) signals are directly digitized and processed to extract quantities of interest. This approach has several significant advantages compared to traditional analog signal shaping. First, analyses can be developed which take pulse-by-pulse differences into account, as in making ballistic deficit compensations. Second, transient induced charge signals, which deposit no net charge on an electrode, can be analyzed to give, for example, information on the position of interaction within the detector. Third, deadtimes from transient overload signals are greatly reduced, from tens of μs to hundreds of ns. Fourth, signals are easily captured, so that more complex analyses can be postponed until the source event has been deemed “interesting”. Fifth, signal capture and processing may easily be based on coincidence criteria between different detectors or different parts of the same detector. XIAs recently introduced CAMAC module, the DGF-4C, provides many of these features for four input channels, including two levels of digital processing and a FIFO for signal capture for each signal channel. The first level of digital processing is “immediate”, taking place in a gate array at the 40 MHz digitization rate, and implements pulse detection, pileup inspection, trapezoidal energy filtering, and control of an external 25.6 μs long FIFO. The second level of digital processing is provided by a digital signal processor (DSP), where more complex algorithms can be implemented. To illustrate digital pulse processing’s possibilities, we describe the application of the DGF-4C to a series of experiments. The first, for which the DGF was originally developed, involves locating gamma-ray interaction sites within large segmented Ge detectors. The goal of this work is to attain spatial resolutions of order 2 mm σ within 70 mm × 90 mm detectors. We show how pulse shape analysis allows ballistic deficit to be significantly reduced in these detectors. A second experiment involves studying exotic nuclei by observing their 1 MeV direct proton decays following implantation in a Si crossed stripe detector at 35 MeV. Whereas the implantation paralyzes analog electronics for almost 10 μs, the DGF allows the study of decay times as short as 1 μs. Initial energy and time resolution results are presented. Finally, we show how the DGF’s precise timing and coincidence capabilities lead to significant experimental simplifications in dealing with phoswich detectors, low background counting work, and trace Pb detection by coincident photon detection.

Fast wire per wire X-ray data acquisition system for time-resolved small angle scattering experiments

Most of the X-ray multi-wire gas detectors used at the EMBL Hamburg outstation for time-resolved studies of biological samples are readout, using the delay line method. The main disadvantage of such readout systems is their event rate limitation introduced by the delay line and the required time to digital conversion step. They also lack the possibility to deal with multiple events. To overcome these limitations, a new approach for the complete readout system was introduced. The new linear detection system is based on the wire per wire approach where each individual wire is associated to a preamplifier/discriminator/counter electronics channel. High-density, front-end electronics was designed around a fast current sensitive preamplifier. An eight-channel board was designed to include the preamplifiers-discriminators and the differential ECL drivers output stages. The detector front-end consists of 25 boards directly mounted inside the detector assembly. To achieve a time framing resolution as short as 10 /spl mu/s, very fast histogramming is required. The only way to implement this for a high number of channels (200 in our case) is by using a distributed system. The digital part of the system consists of a crate controller, up to 16 acquisition boards (capable of handling fast histogramming for up to 32-channels each) and an optical-link board (based on the Cypress 'Hot-Link' chip set). Both the crate controller and the acquisition boards are based on a standard RISC microcontroller (IDT R3081) plug-in board. At present, a dedicated CAMAC module which we developed is used to interface the digital front-end acquisition crate to the host via the optical link.

A Fast Analog-to-Digital Converter

A CAMAC module is described, which contains four independent 8-bit fast analog-to-digital converters. This module is intended for recording digital input signals with a minimal sampling period of 10 ns and a maximal number of samples of 512. Each analog-to-digital converter operates in the external and internal synchronization modes. In the first mode, input processes are digitized after a START signal; in the second mode, a signal exceeding a preset threshold is uninterruptedly sought for and recorded. In this case, its prehistory can be recorded.

Hardware trigger system for Fermilab E866

E866 is the fourth experiment to be performed with the Fermilab Meson East spectrometer. Originally constructed in 1980 for E605, this spectrometer has since been used for E772 and E789. During these three experiments, the hardware trigger depended on components dating from the early 1970s. The trigger system was rebuilt for E866 to improve its reliability and increase its flexibility. The new system incorporates several new modules designed and built specifically for this experiment. Notably, a custom Track Correlator combines the features of a 16-bit memory lookup and a 12-bit prescaler into a single extremely fast CAMAC module. The new hardware trigger system and modules are described, and the system performance during E866 is discussed.

SYRMEP front-end and read-out electronics

The SYRMEP approach to digital mammography implies the use of a monochromatic X-ray beam from a synchrotron source and a slot of superimposed silicon microstrip detectors as a scanning image receptor. The microstrips are read by 32-channel chips mounted on 7-layer hybrid circuits which receive control signals and operating voltages from a MASTER-SLAVE configuration of cards.The MASTER card is driven by the CIRM, a dedicated CAMAC module whose timing function can be easily excluded to obtain data-storage-only units connected to different MASTERs: this second-level modular expansion capability fully achieves the tasks of an electronics system able to follow the SYRMEP detector growth till the final size of seven thousands of channels.

A digital readout system for the SYRMEP silicon strip detectors

The SYRMEP project (SYnchrotron Radiation for MEdical Physics) intends to improve mammography performances using two non-traditional means: synchrotron radiation and silicon detectors. A silicon crystal (the monochromator) allows to choose the optimal beam energy that leads to the maximum signal to noise ratio, while the detectors are arranged to form a matrix of pixels and coupled to low noise high-gain VLSI integrated circuits making the single photon counting technique possible. We present the data acquisition system implemented to read out the VLSI circuit with particular emphasis on two dedicated CAMAC modules that generate the control signals and store the chip digital output on memories that can be accessed via the CAMAC bus. It has been useful in testing the chip performances and can be considered a prototype of the final SYRMEP data acquisition system.

Development of a high mass-resolution TOF-ERDA system for a wide mass range

A high mass-resolution TOF-ERDA system installed at RILAC of RIKEN is presented. The target chamber was designed for TOF-ERDA. A charged-particle detector and a time detector for TOF measurements were installed in the chamber. The data-acquisition system, comprising CAMAC modules, is controlled by a personal computer. The analysis of the spectra is performed off-line. The mass resolution of the system for masses of around A = 28 was evaluated to be 1.9. H, C, N and O in a PIQ film could be measured simultaneously, and the peaks of C, N and O were separated.

Development of a High Mass-Resolution TOF-ERDA System for a Wide Mass Range from Hydrogen to Middle Heavy Elements.

A new ERDA system using time of flight (TOF) detection was set up to realize both higher mass resolution and lower detection limit in RIEKN. The TOF spectrometer using a charged-particle detector and a time detector, and the data-acquisition system comprising CAMAC modules and a personal computer were installed. The mass resolution and the depth resolution of the system for a Si wafer have been determined using 20 Ne, 40 Ar and 136 Xe ions as probes. The incident energies were 20.0 MeV for Ne, 41.5 MeV and 22.6 MeV for Ar and 138.1 MeV for Xe, respectively. The mass resolutions of Si were found to be from 1.90 for 41.5 MeV Ar to 3.32 for 22.6 MeV Ar. Also, the depth resolutions were determined from 1.67 x 10 17 atoms/cm 2 for 20.0 MeV Ne to 2.67 x 10 17 atoms/cm 2 for 138.1 MeV Xe near to the sample surface. A PIQ film and a superconductor sample, YBa 2 Cu 3 O 7 - x , were measured using Ar accelerated to 41.5 MeV. H, C, N and O in the PIQ film and Y, Ba, Cu and O in the superconductor sample could be measured simultaneously and were clearly separated.

Digital x-ray processing electronics for fluorescence EXAFS and spectroscopy

We have developed a digital x-ray processor (DXP) for x-ray fluorescence spectroscopy, implemented in a 4-channel CAMAC module, which accepts inputs of either polarity from reset or tail preamplifiers, and outputs one spectrum per channel. Digital trapezoidal shaping and efficient pileup rejection are implemented in dedicated logic, with programmable peaking times from 0.5 to 20 msec. The energy resolution is comparable to good analog units at equivalent peaking times. A maximum input count rate (ICR) of 500,000 cps per channel can be accomodated at a peaking time of 0.5 msec. A digital signal processor on each channel is used to collect the data, apply corrections, and update the spectrum. The capabilities of the DXP prototype at high rates was tested at SSRL. Using an Ortec single-element germanium detector, the resolution was seen to degrade somewhat with increasing ICR above 150,000 cps, due to effects that we are still investigating. Collaborating with Hewlett-Packard and SSRL, the DXP was also used with a Kevex Si(Li) detector for trace element detection on silicon wafers in comparison with Kevex readout electronics. At 4 msec peaking time, DXP’s resolution was slightly worse (10–15 eV) due to some excess noise pickup, though the background levels in the spectra were essentially identical in the two systems and the DXP’s maximum count rate was several times higher.

A sixteen channel peak sensing ADC for singles spectra in the FERA format

To read out multi-element small X-ray detectors for X-ray fluorescence applications with synchrotron radiation one needs the capability to record multiple singles spectra for each detector element at high rates. We have developed a sixteen channel 11 bit peak sensing ADC in a CAMAC module. We use the FERA readout bus to place the data into a commercially available histogramming module developed to generate multiple histograms from FERA ADCs. The sixteen channels digitize shaped pulses from the detectors without external gating. The digitizing time is 8 /spl mu/sec, the peak acquisition time is /spl ges/2 /spl mu/sec. The module contains a LIFO to permit block transfers in order to minimize dead times associated with the readout. There is a common CAMAC controlled analog threshold for noise suppression and a 16 bit mask to enable or disable individual ADCs. Differential non linearity is less than +8%/-4%. A /spl gamma/-ray spectrum collected using this ADC is presented.

Intelligent CAMAC crate controller incorporating a transputer

A CAMAC crate controller module having a built-in transputer was developed, being named the “Intelligent CAMAC Crate Controller (ICCC)”. Due to the transputer's architecture, multiple ICCCs can be networked by simple serial link connections. The control programs are developed in Occam or C language, which support conccurrent argorithms and their implementation in transputer networks. Each ICCC controls the front-end CAMAC modules in the crate, operates in parallel, and interpretes commands from the host computer. Data read from the modules is concurrently and autonomously processed, and then transmitted to the network where it is gathered into the host computer file system. The present paper describes the ICCC's hardware and software using a simple configuration network. Our particular device application for a balloon-borne experiment is also discussed, i.e., a data acquisition system networking twenty-seven transputers.

Demonstration of three-dimensional imaging with a germanium Compton camera

A proof-of-concept experiment was performed to demonstrate the three-dimensional imaging capabilities of an all-germanium Compton camera for near-field sources. Eight high purity germanium (HPGe) coaxial detectors were configured in two planes of four detectors each. The data acquisition system was assembled from available hardware and off-the-shelf electronics using standard NIM and CAMAC modules. Sixteen-parameter data were recorded event-by-event for later analysis and image reconstruction. The energy resolution of the system was 0.3% at 1333 keV. Preliminary analysis indicates the position resolution for a source at one meter and a specific detector geometry was less than a centimeter. >

Multi-agent CAMAC crate controller with Trident 32-bit transputers

A CAMAC crate controller is developed where three T425-25S 32-bit transputers are installed. The crate controller (CC) conforms to the specifications of the EUR 6500e CAMAC standard. It can be used as a stand-alone CC and also as an auxiliary crate controller (ACC). The transputers on the CC are enabled to execute CAMAC dataway operations independently under the supervision of an arbitration logic. Each transputer is provided with an independent register set. Owing to the transputer, the CC's can be easily networked through the connection of serial links. The CC's in the network make accesses to front-end CAMAC modules in the individual crates in parallel, communicating with each other. Data are read from front-end CAMAC modules, stored into large memory, processed and then submitted to the network concurrently and autonomously.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The second level TOF trigger for the Obelix experiment

We describe a CAMAC module, named TRIGGERK, performing the function of second level trigger in the TOF apparatus of the PS201 experiment at CERN. The module is realized on a single board and is implemented by using three XILINX PGAs. The internal architecture of the module as well as its programming capabilities and mode of usage is described. >

Instrumentation of double-sided silicon strip detectors for multi-particle detection

A compact, modular, low-cost, high-density readout system for double-sided silicon strip detectors (DSSD) has been developed. The system, composed of a customized high-density, multi-channel preamplifier unit combined with commercial CAMAC modules, provides for the individual readout of each of the 32 segments in a 16 × 16 crossed-strip DSSD. This system permits X– Y position sensitivity to be achieved for multiple-particle events, making double-sided silicon strip detectors powerful tools for the study of nuclear reactions leading to many-charged-particle final states.

An improved data acquisition system at the Saskatchewan Accelerator Laboratory

An improved data acquisition system has been in service at the Saskatchewan Accelerator Laboratory for the past 14 months. The system has shown itself to be reliable and easy to use having collected over 800 gigabytes of data for a number of experiments. The system is based on a VME front end computer acquiring data from CAMAC and FASTBUS modules and forwarding the data via an Ethernet connection to an acquisition workstation for archiving and on-line analysis. A multiprocessor real-time operating system in the front end computer makes increasing the performance of the system a simple matter of adding an additional processor to the VME chassis. Experimenters need only write a high-level description of their experiment which is transformed into a C program for the front end computer by a translation program. Special requirements are met by facilities for direct inclusion of user C or FORTRAN code.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The sixteen-channel APEX constant fraction discriminator

A sixteen-channel constant fraction discriminator (CFD) has been constructed for the ATLAS Positron EXperiment (APEX). An integrated circuit, recently introduced commercially, contains all the electronic building blocks required to construct a CFD and makes it possible to fit sixteen CFD channels into a single-width CAMAC module. An important new feature is the time-to-charge converter that is part of each CFD channel. Its calibration constant is controlled via CAMAC. The time-to-charge converter allows the use of low-cost charge-sensitive analog-to-digital converters for timing measurements.

A CAMAC 32-channel pile-up detection and rejection module

A specially developed CAMAC module for detection and rejection of analog pile-up in multiparameter, nuclear spectroscopy experiments is described.