1. 22nd February 1999Ian Lazarus NPG, CLRC1 TDR for data processing 22nd February 1999 Ian Lazarus Nuclear Physics Group CLRC, Daresbury Lab

2. 22nd February 1999Ian Lazarus NPG, CLRC2 TDR for data processing Introduction Delayed coincidence setup problems: Dead time time of flight from target to focal plane high rate of gammas (singles/doubles) Correlation between detectors

3. 22nd February 1999Ian Lazarus NPG, CLRC3 TDR for data processing An example: Jurosphere and RITU Picture taken from University of Liverpool NS web pages, http://ns.ph.liv.ac.uk/posters/ptg/poster1.html

4. 22nd February 1999Ian Lazarus NPG, CLRC4 TDR for data processing Why TDR? Rate at target for VEGA running singles. for 15k rate on Ge centre contacts is: 4 x 4 x 15k = 240k i.e. ave. one  every 4  s. Recoil-gamma coincidence rate: CDT dead time is T.O.F ( 1-5  s) (rejected) or peak+convert+read (12  s) (accepted). CDT loses data significantly in both cases.

5. 22nd February 1999Ian Lazarus NPG, CLRC5 TDR for data processing What is TDR? TDRTDR TDR isTotal Data Readout No hardware trigger Uses a global timestamp Reads virtually all data. Limited only by shaping/conversion time

6. 22nd February 1999Ian Lazarus NPG, CLRC6 TDR for data processing GREAT electronics Target Ge array PIN diodesSi strip Ge strip Seg clover NIM and CAMAC shape amps and CFDs VXI time stamping ADCs (13 x 32 channels in, 13 links out)Metronome Data Acquisition system 356 energy signals388 gates32 TACs

7. 22nd February 1999Ian Lazarus NPG, CLRC7 TDR for data processing What do we need? Time stamp everything @ 100MHz (10ns) New VXI ADC (32 channels, 32 gates, 5us 14bit pk sensing ADC per channel, data link.) New “Metronome” for synchronisation Correlate later in software using temporal and spatial association

8. 22nd February 1999Ian Lazarus NPG, CLRC8 TDR for data processing How does it work? Simple example: Accept gammas detected at the target only if: 1) There is a recoil at the focal plane with timestamp T  +3000ns (+/-200ns) or 2) There are 4 other gammas with timestamps within +/- 50ns of T 

9. 22nd February 1999Ian Lazarus NPG, CLRC9 TDR for data processing TDR data rates. Target position rate: 15kHz per channel: TDR: sensitive to only channel dead time = 5  s pk det + 5  s convert =10  s (15%) Pileup loss (2  s shaping) is 19.5%. So TDR doesn’t cause any  data loss. Focal plane rates are lower. FP Channels will be free for rare events and  emissions from implanted recoils.

10. 22nd February 1999Ian Lazarus NPG, CLRC10 TDR for data processing Total Data Readout Summary. TDR solves recoil-  problems of dead time from high rate gamma singles and T.O.F. TDR allows us to collect and correlate all available data, limited only by pileup. TDR is now feasible because of increased processing power for reconstruction on-line.