1. DESY test beam report: March 2019
Morag Williams

2. DESY test beam 24th March – 1st April @ DESY T21 Aims:
- integrate ATLASPix
- integrate Timepix3
- use Corryvreckan with data taken with EUDAQ2
- set up some automisation of data taking
- take data with ATLASPix
- take data with CLICpix2 assemblies 19 and 20

3. Conditions Beam momentum of 5.0 – 5.4GeV
ATLASPix
beam
Beam momentum of 5.0 – 5.4GeV
In Z: 3 mimosa26 planes, DUT, 3 mimosa26 planes, Timepix3 plane
Used custom made mounts for ATLASPix and CLICpix2 devices
Lost some beam time due to beam momentum magnet not working on Thursday morning, and machine development on Wednesday.
Took data for one ATLASPix and three CLICpix2 assemblies.
Timepix3

4. Conditions Beam momentum of 5.0 – 5.4GeV
ATLASPix
Beam momentum of 5.0 – 5.4GeV
In Z: 3 mimosa26 planes, DUT, 3 mimosa26 planes, Timepix3 plane
Used custom made mounts for ATLASPix and CLICpix2 devices
Lost some beam time due to beam momentum magnet not working on Thursday morning, and machine development on Wednesday.
Took data for one ATLASPix and three CLICpix2 assemblies.
CLICpix2

5. Telescope performance

6. Calculated telescope resolution
Calculation from Dominik:

7. Telescope performance
In test beam, achieved hitmaps, correlations with the reference plane, and telescope alignment.

8. Telescope performance
Outer triplet planes have residual radius of ~0.06mm
Inner triplet planes have ~0.02mm, comparable with performance of all planes of SPS CLICdp telescope.

9. CLICpix2, ATLASpix, problems that occurred
Data taking
CLICpix2, ATLASpix, problems that occurred

10. CLICpix2
3 assemblies: assemblies 16,19 and 20; all FBK sensors, 130μm thick.
Took test runs with assembly 16 to make sure the data taking was working correctly. Saw correlations with the telescope planes, correct hitmap, and associated clusters.
Took data with as 19:
nominal conditions of -60V and 1180
threshold scan 1170 – 1270 in steps of 10
threshold scan 1280 to 2280 in steps of 100
bias scan from -5V to -60V

11. CLICpix2 Took data with assembly 20:
nominal conditions of -60v and threshold 1283
threshold scan 1273 to 1373 in steps of 10
threshold scan 1383 to 2383 in steps of 100
bias scan from -5v to -6ov
Threshold scans used automated data taking written by Lennart, increased the amount of data we could take significantly, requires further improvements for full autonomy.
Bias scans currently done by hand as no connection established with the Keithley power supply.

12. CLICpix2: Example plots for assembly 19 (run 321):
Can see good alignment in the telescope from hitmap, can see correlation with reference plane.
Further analysis will continue, pending DUT-telescope association.
(Over 40s)

13. ATLASpix
200 ohm cm assembly ap1b02w23s11, operated at -60V and threshold 0.95.
Plots provided by Jens: chip is covered by beam; cluster size and pixel ToT seems reasonable.
Analysis of ‘hot’ upper edge and ToT spectrum peak will follow.

14. 1) PLL locking problem
DUT loses PLL lock: error seen at configuration “cannot lock to external clock, PLL will continue in freerunning mode”.
Seen during Feb test beam with CLICpix2; during this test beam with CLICpix2 and ATLASPix.
Required TLU reconfiguration to lock again, not just CaRboard or ATLASPix power cycle.
Can lose the lock mid run as well as during configuration.
When checking with oscilloscope, clock is present at the CaRboard PLL even when not locked.
Means that the event times of the DUT will drift with respect to the event times of the mimosa26 planes (from TLU triggers) by a % factor.

15. PLL locking problem
Have been looking into the data for CLICpix2 assembly 19 and how the event times shift compared to those of the mimosa data. Used nominal conditions.
Note on DESY beam structure:
No beam to T21 during filling of Petra ~ every 30 s
DESY filling scheme (energy ramping) of ~80 ms
Gaps in each fill due to unsuccessful particle delivery (~random)
1 bin = one CLICpix2 frame of 2ms

16. Shift of CLICpix2 is -25.3 ms here
Run 321: Uncorrected
Shift of CLICpix2 is ms here
CLICpix2 event times in red ; mimosa26 (1st telescope plane) event times in blue

17. Run 321: Uncorrected Over 40 seconds Over ~3000 seconds (full run)
In some other runs, completely lose the correlation with the reference plane over time.

18. Run 321: Uncorrected CLICpix2 closer to mimosa data at later time
overlapping
CLICpix2 closer to mimosa data at earlier time
overlapping

19. Run 321: Corrected
Calculated the % factor by which the CLICpix2 event times need to be increased.
Applied correction: Tcorrected = T x
Seems to work well, therefore the drift factor is constant for this run and the drift can be corrected.
Is the factor constant over multiple runs?
Correction factor

20. Run 321: Corrected by

21. Run 391: Clock jumps
Looked at another run to see if the same factor could be used.
Same assembly, different time, no correction applied.
Discovered a jump in CLICpix2 event time at ~98.37s.
Magnitude ~0.75ms
If jumps occur, cannot use correction factor.
Suggests problem is on the CLICpix2 (i.e. Caribou) side, as the mimosa data is regular.

22. Run 387: Large overall shifts
Looked at another run to see if more jumps could be seen.
Found a run in which no jumps have been found, but the overall shift in time of CLICpix2 is over 3 seconds to later times after ~190 seconds.
Opposite direction to previously seen drift; much larger magnitude than the previously seen drift.
Behaviour currently cannot be accounted for.
End of mimosa data
End of CLICpix2 data

23. Solution to PLL locking problem
Found the issue with the lock unlocking, still doesn’t explain the ‘jumps’ seen.
OOF = out of frequency, flag on CaR board clock chip
Tolerance limit for difference between TLU and CaR board clock was too low for the conditions at DESY (was okay for SPS, tolerance was 100).
This caused the OOF flag to be raised when the tolerance limit was met, changing the mode to freerunning.
Fix: increase the tolerance or disable check if needed.
Drift observed to change with each configuration, consistent with data seen from test beam. Should be a constant factor, currently unexplained.

24. 2) Problem with Timepix3 readout
From Timepix3 assembly data using EUDAQ2, get pixel hits with ToA values.
Do not get ‘heartbeat’s in the data.
Reference times from which the ToA values are measured.
To be investigated further

25. 3) ATLASPix data has multiple T0 s
4) ATLASPix decoder currently not finished yet for EUDAQ2 – during test beam took data in ‘raw’ and ‘binary’ modes to ensure usable data.
5) Saw cut off region in ATLASPix hitmaps with significantly fewer hits, not due to obstruction. Fixed by setting VDDRAM to 0.
6) Log collector files not stored from run control.

26. Summary Successful DESY test beam:
- integration of ATLASPix and data taking
- automation of data taking, including threshold scans
- use of EUDAQ2 event loader in Corryvreckan for CLICpix2 data
- threshold and bias voltage scans for two CLICpix2 devices
- solved various issues: PLL locking, ATLASPix hitmap behaviour, general debugging
To do:
- increase data taking autonomy
- find and fix problem of multiple T0 in data
- find and fix Timepix3 heart beat problem
- finalise ATLASPix decoder in Corryvreckan and look at the data taken with EUDAQ2