Overview of the GRETINA Auxiliary Detector Interface

Transcription

1 28 Jan 2006 Aux.Det.Wkshp 1 Overview of the GRETINA Auxiliary Detector Interface David Radford ORNL Auxiliary Detectors Workshop Washington Universtity 28 Jan 2006

2 28 Jan 2006 Aux.Det.Wkshp 2 Outline The Plan from the point of view of GRETINA (Requirements document) The needs of the Aux Detector builders Can we arrange some way(s) to make the interface easy? Lots of overlap with following talks by Sergio and Mario

3 28 Jan 2006 Aux.Det.Wkshp 3 Data Acquisition system Local Trigger Module Signal Digitizers Readout Computer 2.2 MB/s 66 MB/s Global Trigger Module 30 Crystals Network Switch Processing Farm 75 dual Processors Aux. Det. Trigger 6.9 MB/s Workstations, Servers Aux. Det. Data Data Storage 2.3 MB/s + Aux. Data

4 28 Jan 2006 Aux.Det.Wkshp 4 Event Processing Event Building Data Flow: Data from Germanium Detectors Segment events Crystal Event Builder Crystal events 36 segments per detector Signal Decomposition Data from Auxiliary Detectors Interaction points Global Event Builder Global Events 1 30 crystals Tracking Analysis & Archiving

5 28 Jan 2006 Aux.Det.Wkshp 5 Data Merging Event building is done on the basis of timestamps. In order to merge the two data streams, the Aux. Det. data must include the same timestamps as the Ge data. This is really the only constraint on the Aux. Det. data stream. Is there an easy way to implement it?

6 28 Jan 2006 Aux.Det.Wkshp 6 The Trigger The Global Trigger Module will provide for general purpose input + output lines for the aux. detectors. The details of the implementation have not been finalized yet Will it be synchronous or asynchronous (timestamps)? If asynchronous, how will the timestamps be made? How much latency will be allowed?

7 28 Jan 2006 Aux.Det.Wkshp 7 Easiest Solution? One easy solution for both the data stream and the trigger is simply to use the GRETINA digitizers for your auxiliary detectors. Identical timestamps, clock synchronization Easy integration into the trigger system Don t (usually) have to worry about trigger latency Digital pulse processing is ideal for e.g. CsI, neutron detectors, etc. anything requiring Pulse Shape Analysis Flexible preprocessing: no need to read out waveforms

8 Data Acquisition system Local Trigger Module Signal Digitizers Readout Computer 2.2 MB/s 66 MB/s Ge detectors Global Trigger Module Network Switch Processing Farm 75 dual Processors 6.9 MB/s Workstations, Servers Aux. detectors Data Storage Local Trigger Module Signal Digitizers Readout Computer 2.3 MB/s + Aux. Data 28 Jan 2006 Aux.Det.Wkshp 8

9 28 Jan 2006 Aux.Det.Wkshp 9 Easiest Solution (cont d) Should we ask DOE for money for some number (~ ?) channels of digitizer to be reserved for auxiliary detectors?

10 28 Jan 2006 Aux.Det.Wkshp 10 Next Easiest Solution? Use at least one GRETINA digitizer, to digitize anything, even a logic signal Use VME ADCs / interfaces / bridges for remaining signals GRETINA digitizer provides timestamps, clock synchronization Trigger system not quite as easy; will need to generate gates and read out triggers for the other modules Therefore we have to worry about trigger latency

11 28 Jan 2006 Aux.Det.Wkshp 11 Data Acquisition system Local Trigger Module Signal Digitizers Readout Computer 2.2 MB/s 66 MB/s Ge detectors Global Trigger Module Network Switch Processing Farm 75 dual Processors Signal ADCs / Digitizer Interface 6.9 MB/s Workstations, Servers Aux. detectors Readout Computer Data Storage 2.3 MB/s + Aux. Data

12 28 Jan 2006 Aux.Det.Wkshp 12 Next Easiest Solution (cont d) Could replace the GRETINA digitizer with a special timestamp / clock synchronization module Another option for high channel counts (Lee Sobotka et al.): Shaper + peak detect and hold on each channel time slice multiplex multiple channels a single analog pulse train for multiple channels digitize in a GRETINA digitizer channel

13 28 Jan 2006 Aux.Det.Wkshp 13 Trigger Latency? GRETINA needs to know about the Aux Det event in order to decide on the master trigger How much time do we have to provide that information? The Aux Det modules need gates and validation signals, generally provided by the master trigger How quickly do we need that information? i.e. How much time do we have to collect all the master trigger info, make a decision, and generate synchronous logic signals for gates?

14 28 Jan 2006 Aux.Det.Wkshp 14 Trigger Latency? E.g.: Microball Trigger info available from µball at ~ 0.5 µs First gates needed for µball ADCs at ~ 0.8 µs Max. trigger latency Could GRETINA meet this schedule? What if it couldn t? Alternative mode: Fast Clear ; increases dead time significantly

15 28 Jan 2006 Aux.Det.Wkshp 15 Readout Bandwidth VME 64x Bus Bandwidth In principle ~ 160 MB/s Readout CPU to Farm GigE ~ 120 MB/sec Readily achievable ~ 60 MB/s? High enough for all aux. detectors?

16 28 Jan 2006 Aux.Det.Wkshp 16 Two Important Types of AuxDet To help determine t 0 for the event May be important for signal decomposition Improve position resolution E.g. BaF 2, LaCl To determine recoil direction, velocity For Doppler correction Energy resolution Need 10 mrad

17 Doppler Broadening Moving nucleus θ V± V θ Ν θ D E =E 0 Doppler shift 1 V 2 c 2 γ ray detector 1 V c cos Broadening of detected gamma ray energy due to: 3.00% 2.50% angle Spread in speed V 2.00% 1.50% 1.00% Distribution in the direction of velocity θ Ν Resolution 0.50% velocity Detector opening angle θ D 0.00% Lab Angle (degree) Need accurate determination of V and θ. 28 Jan 2006 Aux.Det.Wkshp 17