H. Yaver

Coplanar-grid CdZnTe detector with three-dimensional position sensitivity

A 3-dimensional position-sensitive coplanar-grid detector design for use with compound semiconductors is described. This detector design maintains the advantage of a coplanar-grid detector in which good energy resolution can be obtained from materials with poor charge transport. Position readout in two dimensions is accomplished using proximity-sensing electrodes adjacent to the electron-collecting grid electrode of the detector. Additionally, depth information is obtained by taking the ratio of the amplitudes of the collecting grid signal and the cathode signal. Experimental results from a prototype CdZnTe detector are presented.

Data Acquisition and Trigger System of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), capable of determining the energy and position (within 2 mm) of each gamma-ray interaction point and tracking multiple gamma-ray interactions, has been designed. GRETINA will be composed of seven detector modules, each with four highly pure germanium crystals. Each crystal has 36 segments and one central contact instrumented by charge sensitive amplifiers. Two custom designed modules, the Digitizer/Digital Signal Processing (DSP) and the Trigger Timing and Control, compose the electronics of this system. The digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions with the crystal. Each Digitizer/DSP is controlled by and sends trigger information to the Trigger Timing & Control system through a bidirectional Gbit link. Presently four different trigger algorithms are planned for the trigger system and can be selected for trigger decision. In this paper the details of the electronics and algorithms of the GRETINA data acquisition and trigger system are presented and the performance is reviewed.

GAMMASPHERE-elimination of ballistic deficit by using a quasi-trapezoidal pulse shaper

Gammasphere uses an spherical array of very large (7.2 cm dia.) germanium detectors and only high-multiplicity events are studied. To achieve a reasonable coincidence rate, the individual detector channels must handle high rates with minimum pile-up losses. Ten microseconds was chosen as the total processing time for a signal which means that the shaped signal peaks in about 4 us. The combination of short pulse shaping and the fluctuating long charge collection times (up to 400 ns) in the detectors exaggerates the energy resolution degradation due to ballistic deficit effects. We describe a method of producing a flat-topped pulse with a simple time-invariant network that satisfies GAMMASPHERE requirements and eliminates ballistic deficit effects. >

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.

Determining the drift time of charge carriers in p-type point-contact HPGe detectors

Abstract An algorithm to determine the drift time of charge carriers in p-type point contact (PPC) high-purity germanium (HPGe) detectors from the signals processed with a charge-sensitive preamplifier is introduced. It is demonstrated that the drift times can be used to estimate the distance of charge depositions from the point contact and to characterize losses due to charge trapping. A correction for charge trapping effects over a wide range of energies is implemented using the measured drift times and is shown to improve the energy resolution by up to 30%.

Implementation and performance of the electronics and computing system of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), a germanium detector system capable of measuring energy and position (within better than 2 mm rms) of gamma-ray interaction points and tracking multiple gamma-ray interactions, has been built. GRETINA is composed of seven detector modules, each with four high purity germanium crystals. Four custom designed electronics support the operation of the detectors: Digitizer/Digital Signal Processing (DSP), Trigger/Timing, Breakout Chassis and the Detector Interface Box. The Digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions within a crystal. The computing system is composed of VME readout CPUs running VxWorks, which communicate with 62 dual-processor farm (each processor with four cores) through a 10 Gb/s Ethernet switch. The CPUs read out the digitizer/DSPs and send the data to the farm. The processors compute the position and track of the interactions of the gamma-ray inside the crystals. The processor farm is capable of processing in real-time the position of 20 000 gamma-ray/s. In this paper we will present the details of the implementation and performance of the electronics and computing system of GRETINA.

Silicon array detector system for high-rate, low-noise X-ray spectroscopy

A silicon array detector system is being developed for X-ray fluorescence applications at synchrotron light sources. The detector is wire-bonded to integrated circuits which features 32 channels of charge-sensitive preamplifiers followed by variable-gain pulse shaping amplifiers. The ICs directly drive CAMAC-based A/D boards designed for this application. The data are transferred from the custom designed 16-channel ADC modules via FERABUS readout to commercially available histogramming modules and memory lookup units. The system features fully parallel signal processing to maintain high count rate capability and to preserve the position information. Special LabVIEW-based software has been developed for data acquisition and analysis. The system, currently being assembled for 64-channels, can easily be expanded by increasing the number of detection channels and hardware modules.

A/D processing system for 64-element pixel detector

A new, 8/spl times/8-element pixel detector array for time resolved protein crystallography has been developed at the Lawrence Berkeley National Laboratory (LBNL). Each element has its own on-chip charge sensitive preamplifier and shaper with a peaking time of 100 ns. A total of 64 parallel analog to digital processing channels are required to support the detector. We describe a low-cost, low-power AD processing system, comprising a fast peak-sensing amplifier/stretcher, followed by a slower 12-bit ADC. Each channel also includes a histogramming memory for a fully stand-alone operation of the system. Circuit performance and test data are also presented.

Data acquisition and trigger system of the Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA)

The Gamma Ray Energy Tracking In-Beam Nuclear Array (GRETINA), capable of determining the energy and position (within 2 mm) of each gamma-ray interaction point and tracking multiple gamma-ray interactions, has been designed. GRETINA will be composed of seven detector modules, each with four highly pure germanium crystals. Each crystal has 36 segments and one central contact instrumented by charge sensitive amplifiers. Two custom designed modules, the Digitizer/Digital Signal Processing (DSP) and the Trigger Timing and Control, compose the electronics of this system. The digitizer/DSP converts the analog information with 14-bit analog to digital converters operating at 100 MS/s, and digitally processes the data to determine the energy and timing information of the gamma interactions with the crystal. Each Digitizer/DSP is controlled by and sends trigger information to the Trigger Timing & Control system through a bidirectional Gbit link. Presently four different trigger algorithms are planned for the trigger system and can be selected for trigger decision. In this paper the details of the electronics and algorithms of the GRETINA data acquisition and trigger system are presented and the performance is reviewed.

The luminosity monitoring system for the LHC: Modeling and test results

Simulation results of the Beam Rate of Neutrals (BRAN) luminosity detector for the CERN Large Hadron Collider are presented. The detectors are intended to measure the bunch-by-bunch relative luminosity at the ATLAS and CMS experiments. Building up from experimental results from test runs at the SPS, RHIC and ALS we extend the simulated setup to the TAN neutral absorbers located at 140 m at both sides the IP1 and IP5 interaction points. The expected signal amplitudes are calculated for pp-collisions energies between 450 GeV and 7 TeV using the Monte Carlo package FLUKA and its graphical user interface FLAIR.