1. LAV front-end board test
Silvia Martellotti, Francesco Gonnella
Photo Veto Working Group
3 September 2014
Silvia Martellotti - Laboratori Nazionali di Frascati

2. LAV front-end 9U board Inputs Type Outputs Power connection VME J1
16ch IN
Analog
32ch OUT
LVDS
CANopen or USB
IN OUT
VME custom power
ToT mezzanine card (16 x)
2 channels and 2 threshold per board.
Includes the circuits for: Clamp, Amplifier, Comparator & LVDS driver.
Sum mezzanine card (16 x)
Sum 4 analog channels (8 x)
Sum 16 analog channels (2 x) Connected to a 50W LEMO out
Test pulse controller (1 x)
Can set for each channel:
Pulse height (set/read)
Pulse width (set/read)
Pulse rate (set/read)
Board controller (1x)
Communicate using CAN or USB Allows setting and reading:
Thresholds (set/read)
Power connection (read)
Inputs
Type
Outputs
Power connection
VME J1
64 LVDS output
2 x SCSI2
32 analog signals
2 x DB37
8 analog sums of 4 ch
8 x LEMO-00
2 analog sum of 16 ch
2 x LEMO-00
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

3. LAV front-end electronics
LAV electronics channel working principle
High threshold
Clamp
Amp 6x
Compare
threshold
Low
LVDS
Split
to analog sum
To TDC
To TDC
16ch IN
Analog
32ch OUT
LVDS
CANopen
IN OUT
VME custom power
Split the input signal into two copies: 1 copy to comparator + 1 copy to analog sums
Clamp the signal preserving its width, wide dynamical range is expected (MIP 70 MeV ~ 10 mV, high energy γ ~ 1V)
Amplify the signal and compare with 2 thresholds
Each threshold is independently adjustable up to 250 mV
Produce an LVDS signal and send the signal to the digital read out board
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014
Charge reconstruction algorithm
The actual dependence of Q on ToT can be obtained using a fit to the distribution of Q vs. ToT. This relation is in principle the same for all the LAV PMTs. The sensitivity of the method is reduced at high charge due to the exponential dependence of Q on ToT.
Measure ToT vs. charge using QDC and TDC
only during calibration not during experiment
Fit the function Q(ToT) (i.e. polynomial function)
During data taking, measure the time using a TDC only
Charge reconstruction in NA62 LAV

4. Test setup Hardware setup Hardware layout Software flaw chart LAV FEE
x 16
LAV FEE
Board
TDC CAEN
V1190B
VME Bridge V1718
Linux PC
x 2
32 ch
VME
Pulser
32 ch
x 16
GPIB programming
repeat n times
Store serial ID DB
repeat n times
Repeat n’ times
Set FEE
Threshold
Program
pulser
Run Daq
binary raw to .root
.root storage
Data analysis
Log File
Borad report
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

5. Test stand at CERN
The LAV front-end electronic test stand has been moved to CERN to allow in situ calibration and testing of the boards
Test of all the 86 boards have been performed at CERN by F. Gonnella, V. Kozhuharov, S. Martellotti, M. Moulson
The facility will be also used to characterize the boards we have provided to CHOD and CHANTI
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

6. Board modification is done
All modified boards have been delivered, mounted and tested.
5 boards have problems, 1 is still in Frascati
83/89 boards are ready
81/81 are installed
we have only 2 fully working spares
Investigations to fix problems on the remaining 5 spare is ongoing
Thanks to Katelyn Fariss and Mia de los Reyes!
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

7. Hysteresis (histə’ri:sis)
Time of threshold is measured with two different pulse setups:
The mean values of the ToT distributions in the two setups are evaluated
Hysteresis is evaluated with the following formula:
Note that this strategy does not imply any knowledge on the threshold.
threshold
5ns
20ns
Francesco Gonnella - Laboratori Nazionali di Frascati
11 February 2014

8. Hysteresis The hysteresis has been correctly modified
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

9. Threshold offset The new threshold offset is lower
we gain some mV in sensitivity
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

10. Threshold offset channel by channel
The offset is independent from the channel number
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

11. Calibration slope vs channel
The amplification is dependent on the channel number, i.e. on the track length
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

12. Calibration-line slope
The calibration-line slopes were not altered by the hysteresis modification
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

13. Strange Time-over-Threshold
In few channels we have a peculiar ToT
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

14. Time resolution
The time resolution is not effected from the hysteresis modification
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

15. Time resolution vs channel
There is a clear dependence of the time resolution on the channel number and not on the mezzanine. This is under investigation.
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

16. Efficiency drop
Before hysteresis modification: there were a drop in the efficiency curve for 18% of channel in leading only and 20% of channel in leading and training
After hysteresis modification: the drop in all the efficiency curves disappeared!
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

17. Conclusions Boards were modified, re assembled and tested in time
We have 81/81 installed boards and 2 spares
We will work to repair the 5 boards with some problems
The performance is improved, not only the hysteresis:
Efficiency drops disappeared
We can now safely go down in threshold to 5 mV (even 4 if we smartly swap high and low threshold)
Silvia Martellotti - Laboratori Nazionali di Frascati
3 September 2014

18. Thank you for your attention
3 September 2014