Data Acquisition Systems. How I learned to stop worrying and love computers

Transcription

1 Data Acquisition Systems How I learned to stop worrying and love computers

2 Overview Components of data acquisition systems (DAQ) in nuclear/hep physics. Description of what you will be using Side trip to Computer Automated Measurement And Control (CAMAC). Additional Resources.

3 Components of a DAQ system Detectors Trigger subsystems Readout subystems Data flow subsystems Slow controls Online monitoring and analysis

4 Detectors

5 Analog Electronics Amplify detector signals and shape them Discrimination to provide triggers subsystem inputs Make good timing between logic and analog signals

6 Trigger Systems Determine what the DAQ system will accept as potentially useful events. Reduce rates that are potentially too high to record/analyze to something reasonable by accepting only interesting events. Can be: Simple, discriminator and coincidence requirements Complex multilevel systems

7 Simple triggers System at NSCL Detector Trigger

8 LHC ALICE Trigger system block diagram L0 Trigger FPGA 1μSec decision to accept or not 400 computers to for final trigger decision and event building Here a mere 40 Global data collectors and 20 global data storage servers.

9 Readout Systems Digitize analog signals Read digitized data Buffering/formatting Present data to dataflow subsystem.

10 Readout System Types Stop to digitize Conceptually simple dead-time for each trigger while digitization and readout are performed Continuously digitizing More complex Deep buffering often required dead-time free system.

11 Data Flow Architectures Responsible for getting data that has been read-out to consumers: Data recording Online analysis/monitoring Two classes: General purpose special purpose Two strategies: Push architectures Pull architectures Most common flow control - backpressure flow control.

12 Slow controls Detector/electronics systems are not readonly devices Bias supplies Moveable parts Discriminator settings Calibration systems. Monitoring systems for failure

13 Online Monitoring and Analysis Functional detector diagnostics. Experiment level diagnostics. Online physics if possible.

14 What you ll be using NSCL Data Acquisition System Trigger system entirely NIM electronics Readout CAMAC via CC-USB module Data flow via spectrodaq server No slow controls Online monitoring/analysis via SpecTcl/Xamine

15 CAMAC (Computer Automated Measurement And Control) Old bus standard for digitizer modules (1972) A set of IEEE standards (583, 683, 596, 595, 726, 765, 758) CAMAC is dead but (SeGA at NSCL uses it shhh) we ll use it for this course. Replaced by FASTBUS in 1984 NSCL has been using VME-bus based electronics since mid 1990 s

16 CAMAC Features 24 bit parallel bus (Dataway) housed in a Crate. Originally 1usec per 24 bit transfer Short cycles added to get 450ns/transfer FASTCAMAC extension draft (Yale) -> 100ns/transfer. Geographical addressing. Modules respond to: Up to 32 function codes (f0-f31) f0-f7 are reads f16-f23 are writes Since these are addressed to a slot (N) collectively an operation is called an NAF Up to 16 subaddresses Bus global (Crate wide) operations like: C Clear Z - Zero. I - Inhibit. Modules may: Raise a Look At Me (LAM) signal if they require services Provide status in response to any NAF (Q response). Must be a double wide controller in slots 24/25. Sole Crate master. Usually interfaced to some host computer.

17 CC-USB CAMAC Crate controller developed by J-TEC, Marketed by Wiener. Xylinx FPGA based module. Trigger input List processor Host downloads trigger response list CC-USB buffers several events Transfer blocks of up to 8kbytes to host USB-2 interface to host computers Supports level 1 FASTCAMAC. Many programmable on board devices Scalers, Gate/delay generator Pulser Dataway display built in.

18 NSCLDAQ Readout GUI Readout (data source) Blocks of events CC-USB CAMAC Blocks of events Spectrodaq Server Spectrodaq Server Client programs

19 Readout GUI Control Status

20 SpecTcl Online histogramming package. Scriptable (Tcl) Extensible C++ event processors Tcl computed parameters Tcl scripts to do application specific functions. Tk for graphical user interfaces (standard and application specific). Xamine visualization Mature products but still being developed Xamine First release 1995 SpecTcl First release 2003 Plugin architecture allows dynamic loading of C++ code extensions: Parmeter calibrations Parameter id mapping (cable untangling) Output to radware spectrum file format Output of filtered events root n-tuples Determination of max value parameter (e.g. position in Si strip detectors).

21 SpecTcl Architecture Spectra Xamine Helper programs User Event Processor User Event Processor User Event Processor Pipe data source File data source P a r a m e t e r s Sorting Kernel Parameter, Spectrum, Gate Definitions SpecTcl and user Tcl command extensions C++ Wrapper library Tcl/Tk Interpreter

22 Configuration Files Text files (Tcl scripts really) Insulate you from having to manually create CC-USB lists Insulate you from having to write SpecTcl event processors to decode your data. Prevent skew between the two of these Get you painlessly from readout raw spectra. Define devices Configure devices (CAMAC modules) Any settable parameters like thresholds The order in which devices are read for a trigger. Define the SpecTcl parameters to expect from a device.

23 Sample Config file the hard way: lrs2249 create qdc -slot 6 -id 3 ad811 create adc -slot 8 -id 4 define/configure a LeCroy chan TDc and an Ortec AD811 8 channel ADC stack create events stack config events -modules [list qdc adc] -type event -delay 108 set parameters(adc) [ list adc.00 adc.01 adc.02 adc.03 \ adc.04 adc.05 adc.06 adc.07 set parameters(qdc) [list qdc.00 qdc.01 qdc.02 qdc.03 \ qdc.04 qdc.05 qdc.06 qdc.07 \ qdc.08 qdc.09 qdc.10 qdc.11 Define Readout list Define the SpecTcl parameters for each channel of each module.

24 Configuration parameters the lrs2249 create qdc -slot 6 -id 3 ad811 create adc -slot 8 -id 4 programmer s way stack create events stack config events -modules [list qdc adc] -type event -delay 108 for {set i 0} {$i < 8} {incr i} { lappend adcparams [format adc.%02d $i] } set parameters(adc) $adcparams for {set i 0} {$i < 12} {incr i} { lappend qdcparams [format qdc.%02d $i] } set parameters(qdc) $qdcparams

25 Additional Resources NSCLDAQ and SpecTcl CAMAC ml IEEE Trans Nucl. Sci. V NS-18 No (CAMAC Tutorial issue) Tcl/Tk: