1. SBS Coll. Meeting - Front Tracker GEM
BB / SBS Front-Tracker GEM & Electronics
E. Cisbani / INFN-RM-Sanità
P. Musico / INFN-GE
and the other JLab12 members of Catania, Bari, Genova ed Rome-Sanità
involved in the Front-Tracker GEM Project
SBS Collaboration Meeting
7-8/July/ JLab
7 July JLab
SBS Coll. Meeting - Front Tracker GEM
Overview
Production, latest improvements
Analysis of DESY test beam data
Tracking algorithm and first simulated results
Project status
MPD Electronics status

2. SuperBigbite Spectrometer in Hall A
Large luminosity
Moderate acceptance
Forward angles
Reconfigurable detectors
Background:
photon ( MHz/cm2) charged ( kHz/cm2)
Physics:
Nucleon Form Factors
SIDIS – TMD’s
... Nucleon structure
Front tracker reused in BigBite
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

3. SBS Coll. Meeting - Front Tracker GEM
Workforce and funding
INFN Group
Researcher
(Unit / FTE)
Tech.
Role
Bari
2 / 0.5
Gas system and beam test
Catania
3* / 1.5
3 / 2
GEM module assembling, mechanics, beam test, analysis
Genova
1** / 0.5
Electronics design and test
Rome/Sanità
1 / 0.5
Coordination, design, test, chamber integration, analysis, DAQ and reconstruction
Total
7 / 3.0
6 / 4
Other support: CERN / UVa / JLab
*) one mechanical engineer
**) electronic engineer
INFN/Funding:
Prototyping and Production ( ): 800 kUSD
Production and Maintainance ( ): ~50 kUSD/year
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

4. Front Tracker Chamber: 40x150 cm2
Main Technical solutions
Use the COMPASS approach: 3xGEM, 2D readout - one significant difference: use new single mask GEM foil (instead of double mask) – cheaper and faster production
Modular design: chambers consists of 3 independent GEM modules (40x50 cm2) with thin dead area
Electronics around the module, direct connection; 90 degree bending between modules
External support frame in carbon fiber (long bars) to minimize thermal deformation
40x50 cm2
module
Front Tracker Chamber: 40x150 cm2
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

5. GEM Module construction process
Module production fully established in INFN-Catania
Electronics preliminary QA in Genoa
Module integration and characterization in INFN-Sanità
GEM Foils
HV curing and
quality test
Permaglas Frames
Visual Inspection
Ultrasound bath
cleaning
Production rate
2 module in 3 months
Stretching
Gluing
Assembling
gas lines
Put together
(align on reference pins)
Electronics
Test
Clean room
Glue Curing
(>24 h)
Finalization
(solder resistor, check HV)
Electronics integration
Test and characterization by rad. source and cosmics
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

6. Assembling Improvements in Catania
Several small but effective impromevents during last 2 years; one of the most relevent is the compression system during glue curing --- From Lead to vacuum ---
Current System based on vacuum bag
Very uniform pressure for glue degassing
Old System based on Lead Bricks
Original idea from LNF- Bencivenni Group
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

7. HV divider and new GEM foils
HV connector
«spike» signal output
HV Divider and spike monitor circuit
Protective SMD
resistors
Reasonably compact,
Easy to change
Include output signal for «spike» detection
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

8. Test and characterization setup
Almost finalized Use small 10x10 GEM as «reference» (in series) Large scintillation pads for cosmic Test up to 3 large GEM simultaneously
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

9. SBS GEM Tracker - Test Beam / Jan 2014
Small scale final system (gas, LV, HV monitored)
Main Goals:
Characterize chambers in terms of charge sharing, efficiency and spatial resolution at different HV, gas mixture.
Figure out the gain variation of the previous test
Reference
Small GEM
3 Big GEMs
DESY/EUDET
Pixel Telescope
1-4 GeV
Electron
Beam
AIDA-EUDET support
→ Got lot's of good data with high spatial resolution information from pixel telescope
→ Stable performance (“all” conditions carefully monitored)
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

10. SBS Coll. Meeting - Front Tracker GEM
Spacers shadow
Cluster distributions of 9 cumulated runs
Spacer
Spacer shadow of ≈ 2 mm
→ 2.2% of total dead area of a single GEM module
(Cluster finding not optimized for spacer border)
Masked
channels
Spacer
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

11. SBS GEM Test: typical event (single module)
T0+25ns
(A1)
T0+50ns
(A2)
cluster
T0+125ns
T0 (A0)
y - Strip
x - Strip
Combination of T0, T0+25ns, T0+50 ns
Fit of hit
signal
evolution
Readout dual layer
(x bottom and y top) strip plane
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

12. SBS GEM Test: measured quantities (run 499)x y
x/y
cluster
charge
max strip
beam
position
width
max peak
sample #
clusters
Note: beam cross-section ≈ 3x2 mm2, approx. 30% with 2 or 3 hits in beam pulse
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

13. SBS GEM Test: signal evolution fit (run 499)
6 sample fit! x y
x/y
Integral
Start time (t0)
Leading Const.
Trailing Const.
Chi2
tau0 ≈ 20 ns, tau1 ≈ 90 ns, RMS(t0) ≈ 4-5 ns
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

14. GEM Beam Test / Time resolution
Excellent (surprising ?) start time spread (from fit) < 5 ns
expected at the level of 25/sqrt(12) ≈ 4 ns (in case of negligible contribution from electron drifting in GEM)
x/y start time reasonably correlated
no apparent effect of MPD clock synch
time spread depends on choice of APV latency (see next slide)
Time spread < 5 ns!
Test beam pulse period 160 ms,
multiple of APV clock period
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

15. Simulated Start Time Reconstruction
Zoom
Reconstructed Start Time (t0)
Use double exponential function to fit 6 samples extracted with uniform random jitter (±12.5 ns) and poissonian amplitude distribution + gaussian noise.
Optimal latency setting:
first sample around the beginning of the signal
Error on t0
Chi2 of the fit
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

16. GEM Beam Test: Spatial Scan – Start Time
Gas flow rate: 54.3 ccm (0.5V/h)
Peak Sample
Start Time (fit)
Look reasonably consistent
Peak Sample vs V/h:
2 V/h: 1.2 ±0.4
1 V/h: 1.2 ±0.4
0.5 V/h: 1.3 ±0.5
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

17. GEM Beam Test: Spatial Scan – Start Time
Start time increase slightly
(but within uncertienties)
Start time basically constant or sligtly decreasing (opposite to y ?)
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

18. GEM Test Beam: spatial uniformity – Charge Sharing
Charge asymmetry = 2 (Cx-Cy)/(Cx+Cy) ≈ 0.4÷0.5
HV=4100
Ar/CO2=70/30 y x
→ x/y Charge Sharing ≈
NOTE: some x/y hits can be not correcly associated or have pileup due to events with 2 or 3 particles/pulse
Charge asymmetry spread ≈ 0.3
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

19. GEM Test Beam: spatial uniformity – Hit Cahrge
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

20. Reconstruction Efficiency vs #Event
Efficiency holes in some of the runs: beam instability ? Lost synch with trigger ?
Good run
Analysis work in progress, recently master student from Catania joint.
Several data to be analyzed
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

21. SBS Coll. Meeting - Front Tracker GEM
Three steps track reconstruction:
Suppress accidentals and ghost with time and charge correlation
Associate hits with global analysis (neural network approach)
Precise track reconstruction on remaining candidate tracks by Kalman filter method
Background level of:
400 MHz/cm2 photons
200 kHz/cm2 charged
Signal width ≈ 250 ns
→ Hits/cm2/trigger ≈ 0.1
→ Ghosts/cm2/trigger ≈ !
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

22. SBS Coll. Meeting - Front Tracker GEM
Sij – neuron (0 or 1) – connection between two points
(to be minimized)
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

23. Track Association by NN / Simulation
Energy
Vij
Neuron changing rate
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

24. Kalman Filter Reconstruction: simulation
Residues
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

25. Material Procurement Status
Front Tracker
Module
Chamber
In house
Ordered 1 6 3 18
GEM Foils (CERN)
Drift Foil
GEM foils 9 54 51
Readout 15
Honeycomb
Mechanics (RESARM)
Frame 0 – Cover 20
Frame 1 – Top
Frame 2 – Drift
Frame 3 – GEM 2 36 40
Frame 4 – Readout
External Frame (Plyform) 1*
Electronics (EES) FE
324
250
100
MPD 4 24 26
Backplane 12 72 80
Patch Panel (digital + analog) 8 48 50
Electronics Cabling (LINDY)
HDMI 3m cable
144
HDMI 20m cable 5 90 45
LV cable **
HV cable 7 21
126
HV Divider
LV Power Supply (6Vx20 Amp)
HV Power Supply
Gas System
Controller + Flowmeters (MKS)
Connectors (Legris) 10
212
Patch Panel Gas
General Patch Panel
Most of the material already in house or procured Remaining parts will be procured in 2014 Assembling line operational Testing line under finalization *) Design completed, waiting first proto **) 2014 funding
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

26. GEM Production and Test Status
Produced or Assembled
Tested
NOT Accepted
Degradation after first test
GEM foils 51 25 7
Readout+Honeycomb
15 / 18 1
GEM Module 5+ 3 2
Front End Electronics
250* 50 -
VME Modules 26
Backplane 80
12+
Patch Panel
many
returned to company***
The very first 4 GEM foils did not pass the original quality checks, 3 recent GEM foils of the same bunch did not pass the quality check
One readout + honeycomb suffered bad gluing (probably still usable)
2 of the GEM modules passed preliminary tests but then degraded significiantly (large dark current due to (? gas contamination ?); still chance to fix them.
*** soldering problem, bug fixed
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

27. SBS Coll. Meeting - Front Tracker GEM
Schedule and Status
2009
2010
2011
2012
2013
2014
2015
Preliminary design (include MC study)
Prototyping
Procurement
Pre-Production
(1st chamber)
Production
Beam Test
Dec
DESY
Sept
Mainz
June
CERN
May
Jan
Development phases in part affected by constraints in the flow of funding
Delivery delay of the GEM foils from CERN for prototyping and pre-production
(no significant impact in SBS, we started erlier)
During pre-production we made some fine optimization:
GEM foil, details in construction procedure;
one drastic change in foil quality check.
Development includes: GEM chambers, readout electronics (and related software)
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

28. SBS Coll. Meeting - Front Tracker GEM
Main Open Issues
Long cable noise
If no fix available: change cabling topology
Readout plane manufacturing
Test in high bck needed !
GEM modules «aging»
To be investigated
Data rate / VME Crates (?)
Implement optical fiber and SSP communication (?)
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

29. SBS Coll. Meeting - Front Tracker GEM
GEM Tracker Activity
Continue Production
Test, Characterization and Calibration of GEM and electronics
Fix damaged modules/material, replace if no fix possible
Finalization of a rubust and efficient track reconstruction algorithm
Complete and test the complex firmware of the DAQ
Study (and solve) open issues
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

30. Working Space @Jlab needed
GEM chamber assembling and testing need space at JLab (layout sent in 2010)
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

31. GEM Electronic System Status
Production status of electronic boards
Firmware Update on MPD v 4.0
VME intrerface
Event Builder
7-8 July 2014
Paolo Musico and Evaristo Cisbani
SBS JLAB

32. Production Status APV Front-End cards
210 delivered (some used for DESY test)
140 in progress (SMD ok, to be bonded)
Backplanes
74 delivered (some tested)
MPD
28 delivered and tested: 2 with marginal problems (to be fixed)
Patch Panels
25 Analog Patch Panels delivered
35 Digital Patch Panels delivered
7-8 July 2014
SBS JLAB

33. MPD v 4.0 firmware update Revised memory mapping
D64 read only cycle implemented: MBLT, 2eVME, 2eSST
2eSST simulated peak speed: 148, 222, 296 MB/s
Event builder implemented and simulated
TBD
Multiboard block transfer
Analyze use of fiber optic protocol
7-8 July 2014
SBS JLAB

34. MPD v 4.0 VME interface testing
2eSST cycles tested with STRUCK SIS-3104
2eSST supported by new firmware release
Readout speed measured by software: 100 transfer 4MB each. Data integrity checked for each block. Speed limited by SIS3104 2Gb/s fiber connection
Bus speed is measured directly on VME bus
7-8 July 2014
SBS JLAB
CYCLE
DATA period
Bus Speed
Readout Speed
2eSST160
6 ck = 54 ns (3s/3h)
142 MB/s
117 MB/s
2eSST267
4 ck = 36 ns (2s/2h)
213 MB/s
124 MB/s
2eSST320
3 ck = 27 ns (2s/1h)
284 MB/s

35. Event Builder
Implemented multi event block structure as suggested by DAQ people.
Native data width: 24 bit, packed to 32 bit on 64 bit boundary for efficiency.
Implemented 128MB FIFO data buffer using DDR2 SDRAM.
Quite complicate machinery used to arbiter read and write to/from DDR2.
Output can be read in 32/64 bit format in any of the supported VME cycles, including 2eSST.
Performed functional simulation (FPGA + DDR2 + ADC) of quite simple events to follow all the signals.
Some effort has to be put in DAQ driver to recover packed data.
7-8 July 2014
SBS JLAB

36. Next Steps
Analyze a possible implementation of fiber optic data link to be connected to the SSP
Implement Multi Board block transfer (some hints needed)
Deep debug and test (implies rewriting of some DAQ code)
7-8 July 2014
SBS JLAB

37. Support Slides

38. “Residual Noise” on first APV channels
Condition:
4 cards connected to chamber (one by flat adapter)
Cards connected to VME by 20 m long HDMI cables
Evident noise on first few (up to 8) channels of each card;
This noise is somehow masked in the card with adapter (this is way we never put great attention to it in the past)
Baseline noise at the level of 7 ADC channel.
Pedestal
Strips, physics order
RMS of Pedestal
Card + Flat Adapter
GEM
VME
HDMI cable
MPD
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

39. Electronics Misconfiguration Issue
Electronics Low Voltage monitor
2 power lines for 2 groups of cards
Small current drop during APV configuration; the “normal” level must restore
In case of proper configuration; otherwise the electronics does not work properly
Chamber appears inefficient → this likely explain the gain issue in 2013 DESY test
7 July JLab
SBS Coll. Meeting - Front Tracker GEM

40. BARI Gas System w/Humidity Sensor and Absorber
< 100 ppM of H2O
Series operation
Series operation or
GEM_50x40 or
GEM_50x40
~ 20 m long pipe
~10 m
~10 m
~ 20 m long pipe
7 July JLab
SBS Coll. Meeting - Front Tracker GEM