Method and apparatus for processing detector signals

The invention relates to a method for processing Detector signals and a device for carrying out the Process.

The German patent DE 42 26 175 C2 describes a Method for evaluating the detector signals, in which detectors generate detector signals via preamplifiers amplified and then transferred, for example, about 2 feet up to 200 meters long, analog signal transmission cable Scanning analog-to-digital converter to be transmitted. Behind the Scanning analog-to-digital converters (ADU) are digital Signal processing units connected. The digital Signal processing units to process, depending on Performance the continuous stream of single or multiple scanning analog-to-digital converter (ADU). Data of various digital Signal processing units are then in these known methods by a central DAQ data acquisition unit detected.

Further, it is known, the detector signals by handsets to capture. The handsets each have a single Detector. A data transmission path is not here provided since the detecting and sensing means in a Housing are summarized.

The invention is based on the object of a generic Process further so that an influence of Interference is avoided.

This object is achieved in that analog measuring signals immediately after a pre-amplification by a scanning analog-to-digital converter (ADC) to digital Signals are converted to digital signals, and that the then via a digital data link a digital signal processing unit and a Data acquisition unit (DAQ) are transmitted.

The invention provides for analogue signals from detectors in the convert to digital signals range of detectors and Subsequently, the digital signals over a to transmit data transmission path.

It is possible both the digital signals to transmit unchanged or processed.

The to digital by converting the detector signals in Signals resulting digital signal stream may further varied are processed.

The further processing of the digital signals can both before the data transmission path in the field of Detectors and after the data transmission path in the effected area of ​​the data acquisition unit (DAQ).

A first advantageous embodiment of the invention is characterized is characterized in that the digital signals are substantially unchanged to the digital signal processing unit and Data acquisition unit (DAQ) are transmitted.

A further advantageous embodiment of the invention is characterized in that the digital signals prior to Transmission over the data transmission path at least subjected to digital signal processing step will.

The digital signal processing step in many done manner, for example by a programmable Logic device (PLD).

The implementation of the digital signal processing step, prior to data transmission via the data transmission path makes it possible, on the number of the Data link data to be transmitted to to reduce.

A particularly effective reduction of the data stream can be be achieved if the signal processing step a includes triggering of the digital signals. triggering means that the areas scanned by the ADU and digitized waveform are marked, which Information about the detection event included.

This makes it possible that each of first to examined event - in particular a detection event - Filtering out from the data stream and then the to transmit information about the particular event.

Further, it is for reducing the data stream appropriate that in one or more signal processing steps, a Energy information about the detection event from the digital samples is extracted.

This is due to the characteristics of the detector signals particularly advantageous to use a moving window deconvolution technique use.

Furthermore, it can reduce the data stream advantageously achieved in that by further Processing steps about interaction Places be determined by detecting events in the detector.

Another object of the invention is to provide an apparatus for processing of detector signals with preamplifiers for Amplifying the detector signals, scanning analog-to-digital converters (ADU) for converting the detector signals into digital signals, with a signal processing unit and in such a way with a data transmission path that the scanning analog-to-digital converter (ADC) between the Preamplifiers and the data transmission path are.

A particularly compact and convenient design of the Device can advantageously be achieved if that between the scanning analog-to-digital converters (ADU) and the data transmission path signal processing units . are

Here is an account of the flexibility of their Programmability and its compactness particularly suitable embodiment is that in which at least part the digital signal processing units using digital Signal processors (DSP), programmable logic devices (PLD), or field programmable gate arrays (FPGA) is trained.

A reduction in the number of required Data transmission links and digital Signal processing units is in a particularly advantageous embodiment of the invention achieved by that a plurality of scanning analog-to-digital converter (ADC) with Inputs are connected to a multiplexer, the signals, the summarizing and a common digital Signal processing unit transmits.

It is also appropriate that outputs a plurality of digital Signal processing units connected to a multiplexer are, the multiplexer of the digital Signal processing units outputted signals in a Data transmission channel transmits. This makes it possible, in data transmission lines with a smaller number of but data transmission channels complete information to transmit on the detection signals.

A reduction of interference can be in a particularly advantageous and expedient manner by ensure that the transmission path at least one Light guide contains. This addition takes place isolation between the signals acquisition and the Data recording.

Further advantages, special features and practical Further developments of the invention result from the Claims and the presentation of preferred Embodiments.

The invention is exemplified by detectors for γ-radiation explained.

However, the invention is not limited to the illustrated Detectors limited because the signal processing illustrated can be carried out regardless of the type of the detectors.

In the figure below, the Detection events with energy values, timings detected and location information and processes.

It is expedient that digital signal processing steps be applied and combined.

A signal processing step is the trigger. By Triggering is preferably a first significant reduction achieved of the data stream, in particular by the suppression sampled the areas of the ADC and digitized Signal path that does not have the relevant information Detection event included.

In one implementation of the trigger in a programmable device, the triggering by a Reprogramming of the block are varied.

Thus, it is possible, for example the device for Processing the detection signals and the corresponding Method to each experimentally desired parameters adapt.

Another advantageously acquired information is the Energy of the detection event.

In order to derive energy information are various process steps of a reduction full data stream from one sample per sampling on only one energy value per detection event include.

In order to reduce the required data transfer and Computing power, it is possible, prior to determination of the energy a sub-sampling (decimation) and averaging over several samples of the digitized detector signals perform.

For the detection of time information, it is expedient, to take into account process steps, the determination of a allow time information.

Here, preferably, the knowledge is used that it sufficient only selected samples, particularly those from the region of the rising edges of the digitized Detector signals to evaluate at the time of to determine detection event.

To determine the interaction of cities Detection events is also a variety of Method, or process steps suitable.

Preferably also in this case the shape of the rising edges the digitized signals of the detection events evaluated. It is also advantageous, wavelet transforms to extract the relevant properties the signal to use.

In the determination of the interaction sites of Detection events the data more combined signal processing channels, so that a further data reduction results.

In the illustrated examples, a combination of Preamplifier and scanning analog-to-digital converter (ADC) as a digital preamplifier referred to as this from the won originally analog measurement signals digital signals will.

When transferring the digitized signals, it is in the Usually possible to be limited to areas of the signal, containing relevant information, or the signals in preprocess digital signal processing units, in a reduction of via the data transmission path data to be transmitted in detector arrays with a Plurality of detectors makes it particularly noticeable.

To illustrate examples are mentioned below, in which concrete numbers (ND: = Number of Detectors) of Detectors are known, the invention is not limited certain numbers is limited.

A detector array for example 180 segmented Detectors each example, 32 segments (NS: = exhibit Number of segment) and a central contact, results by way of example, the number of 5,940 Data processing channels (NC: = Number of Channels). The other values ​​given below are also by way of example to illustrate the calculation examples to understand.

In the calculation examples, the scanning analog-to-digital converter (ADU), a data width of 14 bits vo (CR: = Conversion Range) and a sampling rate (SF: = Sampling Frequency) of 50 MSPS on.

Further, in the examples, a maximum Detection event rate (EN: = Detector Event rate) of 20,000 Hz count events, an average number of 4 Interactions per detection event (NI: = Number of Interactions), a number of 10 active segments per Detection event (NA: = Number of Active segments) each Detector and an external trigger rate (TR: = trigger rate) of for example, 100 kHz or 1 MHz adopted.

Furthermore, in the examples of a for Pulse shape analysis relevant charge accumulation time of the detector starting with about 400 ns, a maximum number of 25 samples for the rising edge of the signal range the detection event corresponds (NL: = Number od Leading Edge samples).

The data width of the output data is in the Examples 48 bit for the timestamp (WTS: = Word width of Timestamp), 16 bit for the energy (WEN: = Word width of Energy), 8 bits for specifying the exact time point within a sample interval (WTI: = Word width of timing) and 32 bits for the position data (WPO: = Word width of Position).

Here, the 32 bits for the position data distributed on 8 bit for the detector number and each 6 bit for Segment number, the radius, the associated azimuthal and for the axial z-coordinate of a detector.

Example 1:

In a preferred embodiment of the invention takes the digital preamplifier only pre-amplification and Digitization of the detector signal, while the other Signal processing steps only after transfer of the data via the data transmission path in an Signal processing unit are made.

The data transfer rate is for each Data transmission channel CR * SF = 87.5 MByte / s.

The data of the individual data processing channels can individual data links are issued. Alternatively, through the use of one or more Multiplexer multiple data links with a lower bandwidth to a data transmission path with high bandwidth are summarized.

In the illustrated case where the data channels of a 32-fold segmented detector are combined, is the required bandwidth of the overall transmission path a detector 2.89 Gbyte / s plus transmission protocol data. For higher sampling rates and / or a higher number of detector segments, the required be considerably higher bandwidth. Suitably, the Bandwidth characteristics of the respective detector array adjusted.

is a result of the combination of data transmission links the scope of the actual transfer of the self reduced employed digital components, particularly for the data format matching, protocol adaptation and for Line driver.

In contrast to the known methods in which analog Signals over the data transmission path to be transmitted, This system is far less sensitive towards Noise.

To further reduce interference, it is advantageous the analog processing of the signals in sensitive analog portion of the preamplifier of its digital to separate processing. This is particularly useful characterized in that the digital data transmission path at least one light guide, or otherwise galvanic decoupling contains.

In a further preferred embodiment of the invention be additional signal processing steps in the integrated digital preamp.

The following examples include a broad application of signal processing steps prior to the transmission of Data on the data transmission path, so that the Data stream, and thus the required bandwidth of the Data links and the burden on reduces subsequent signal processing units will.

These signal processing steps as effective and to perform flexible, it is appropriate, in the field the digital preamp Programmable Logic Devices (PLD), Field Programmable Gate Arrays (FPGA), or digital signal Processors (DSP) to use.

Example 2:

For signal processing steps such as the Moving Window Deconvolution (MWD) for the extraction of energy of Detection events, which are not the full range of Detector signal require, a sub-sampling (Decimation) carried out by an appropriate factor. in the Illustrated case, the factor is 8, but this is only meant to be exemplary. This reduction factor results CR '* SF / 8 = 13.3 MByte / s as required bandwidth per Signal processing channel for the transfer of the Energy information.

To further reduce the data stream, in this Process triggering the digitized detector signals be used.

The triggering of the signals can be modified by a self-triggering on channel or detector plane, as well as by a trigger carried out on a global scale with an external trigger signal, wherein the different trigger methods arbitrarily together can be combined.

The Selbsttriggerung is particularly suitable, the to reduce the data stream in the sense that only a few Samples from the region of the rising edge of the signals be taken into account of detection events, while the Most of the remainder is not transmitted.

Since a Selbsttriggerung control by the data carried himself, this depends of the resulting data stream on the number of detection events from DE.

In a Selbsttriggerung on detector plane is required, all data channels NC 'of a detector, ie the the 32 segments plus the central contact to read. In the case illustrated applies NC '= NC / ND = 33rd

This produces for each 25 samples from the NL Leading edge area of ​​the signals of the detection events DE a data rate of NC '* DE * NL * CR = 28.9 MByte / s per Detector.

For the samples (decimated) for power provision applies NC '* 13.3 = 438.9 MB / s.

DE For the stream of time marks * WTS = 12:12 MByte / s.

The total data stream each detector is shown in Example 468 MByte / s, which corresponds to a reduction by a factor of 6.2 compared to the Example 1 corresponds.

By selectively trigger on active individual channels and / or by zero suppression, ie suppression of channels do not contain signals of detection events, it is possible to avoid a read-out of channels for no measurement contain relevant information. For reading the samples from the leading edge region of the signals detection of events results in a more Reduction of the data stream by a factor of NA / NC '= 0.3.

With such a reduction must then, however, Identification information on the active segments be mitübermittelt what again slightly by the data stream DE * NA * 6 bit = 0:15 MByte / s.

takes place the generation of a global trigger signal preferably by an external device.

Triggering by an external device requires a Adding to the corresponding inputs and outputs digital preamplifiers, and a galvanic decoupling the lines, transmitted trigger signals over which will.

External triggering has the advantage that the count rate of read out detection events on the effective Trigger rate divided by the total number of detectors, that is, for example, to DE_H = (TR_H * 30) / ND = 16.7 KHz for a 100 KHz trigger signal TR_HWhich is based on detectors 30 acts (high multiplicity trigger), or on DE_L = (TR_L * 1) / ND = 5.6 KHz for a 1 MHz trigger signal TR_L. which acts on only one detector (low multiplicity trigger), reduced.

This results in a further reduction of Data transmission rates for the samples from the Leading edge area of ​​the signals of detection events, in the illustrated case to 24.1 MByte / s for the high multiplicity trigger, or at 8.0 MB / s for the low multiplicity trigger.

Example 3:

In Example 3 is illustrated how the Implementation additional functions in the digital Signal processing units in the area of ​​digital Preamplifier, the data transfer rate is further reduced can be.

For this purpose, it is required that the digital Signal processing units complex functions, like use moving window deconvolution technique. The order conducted analysis of the energy of the detection events leads to a particularly drastic reduction of Data transfer rate. In the illustrated case, the Reduction NC '* CR' * SF / 8 = 438.9 MB / s to NC '* DE * WEN = 1:32 MB / s because of several hundred samples only a respective energy value WEN is extracted, the transfer must become.

It is also possible by the energy analysis, Data channels, the energy information included by those contain no energy information to distinguish.

By selectively triggers and reading of energy values ​​from only the data channels, the power information included, the data transfer rate can be further reduce, in the case shown in ((NS / 3) + 1) * DE * WEN = 12:17 MByte / s.

Together with the corresponding data stream for the Leading edge area of ​​the signals of detection events to be transferred from NA * DE * NL * CR = 8.7 MByte and the Information about the points in time of detection events and results for identifying the active detector segments a total data stream of about 9 MB / s per detector.

This represents a very significant reduction compared to Initial situation is, in the overall data stream 2.89 GB / sec per detector.

As described above, can be explained by external triggering the Detektionsereigniszählrate EN further reduce, for example, by a factor of DE_H/ DE = 0.84 respectively DE_L/ DE = 12:28.

The examples presented show preferred Embodiments of the invention. In particular, the Examples advantages arising from the fact that the Detector signals already in the immediate vicinity of Detectors are converted to digital signals. in this connection shows that both the number of required Data links and a hold of Interference is reduced.

To further reduce the number of required Data links and their transmission bandwidths is carried out by reducing the information to be provided in the data Area of ​​the detectors and located there scanning analog-to-digital converter (ADU) in individual examples of Invention, preprocessing the digitized signals.

The pre-processing of the signals is shown only after their digitization possible, but by way of example understand since other preprocessing steps, which an elimination of unimportant for signal processing and a reduction of the important for the signal processing Data enable, can be used.

Particularly preferred embodiments of the invention include the concept, in the region of the scanning analog-to-digital converter (ADU) and associated with them digital already signal processing units, a first evaluation make the data.

is through a selection of suitable electronic components it is possible, the respective processes to experimental adapt needs. Preferably, this programmable digital components used.

It is particularly advantageous that certain elements of Invention can be combined as required.

This is a further adaptation of the method and for performing the method suitable device to different detector arrays and expected Properties of detection events possible.