1. FToF wall TDR review
D.VeretennIkov
GSI

2. Content Requirements and design MonteCarlo simulation Count rates
 benchmark
PID and T0 determination
Test of prototype
PMT check
Plastic scintillator measurement
Time resolution
Summary
Cost matrix
Conclusion & Outlook

3. Overview of FToF detector
66 scintillation counters: 20 counters in the central part and 46 counters in the side parts (23 counters in each side part)
FToF dedicated to measure the time of flight of forward particles emitted within the forward spectrometer acceptance with −5°< 𝜃 𝑦 <5° and −10°< 𝜃 𝑥 <10°

4. Forward TOF wall functions
PID of forward emitted particles using time-of-flight information for low momentum hadrons:
p/K separation at momenta < 4 GeV/c
K/ separation at momenta < 3 GeV/c
close to or below forward RICH threshold
PID obtained using hits time correlations, without start counter
Event start stamp reference time T0
provided a particle independently identified e.g. with FRICH or EMC(FSC) or Forward muon system
Provide energy deposition information
expected energy deposition range from 5 to 50 MeV

5. Technical requirements for the FTOF wall
Time resolution better then 100 ps
FToF wall positioned at 7.5 m downstream the target
Sensitive area of the scintillation wall is 5.6 m (width) x 1.4 m (height)
Thickness of the scintillator not more then 2.5 cm need by forward EMC
Operate with counting rate about 1 MHz at PANDA high luminosity regime
Dynamic range corresponds energy deposition from 5 to 50 MeV
Operate at dipole fringe field of Bz < 80 G
The opening in the wall for the vacuum beam pipe foreseen

6. FToF wall hadron PID 𝑚= 𝑝 𝑐 𝑡 2 𝑡 𝑐 2 −1 , 𝑡 𝑐 =𝐿/𝑐 σ = 50 ps
𝑚= 𝑝 𝑐 𝑡 2 𝑡 𝑐 2 −1 , 𝑡 𝑐 =𝐿/𝑐
σ = 50 ps
p/K separation < 4.5 GeV/c
K/ separation < 3 GeV/c
𝛿𝑚 𝑚 = 𝛿𝑝 𝑝 𝛾 𝜎 𝑇𝑂𝐹 𝑡 2
σ = 100 ps
p/K separation < 3.5 GeV/c
K/ separation < 2.5 GeV/c
ToF resolution σTOF = 50 or 100 ps
FS momentum resolution Δp/p = 0.01

7. FToF wall design Side part 23 slabs 10 cm width Central part
The wall can be built of commercially available plastic scintillation slabs and fast photodetectors. Sensitive area is 560 cm (width) x 140 cm (height) x 2.5 (thick)
Granularity : counting rate below 1 MHz at PANDA HL regime

8. Properties of plastic scintillators
BC-400
BC-404
BC-408
BC-412
BC-416
Light Output, % anthracene 65 68 64 60 38
Rise Time, ns
0.9
0.7
1.0 -
Decay Time, ns
2.4
1.8
2.1
3.3
4.0
Pulse Width FWHM, ns
2.7
2.2
2.5
4.2
5.3
Light Atten. Length, cm
160
140
210
Wavelength of max. emission, nm
428
408
425
434
Principal uses
General purpose
Fast counting
Large area
Large area
Peak of light output at 425 nm well corresponds to most of fast PMTs

9. Attenuation length and rise time for BC408
GEANT4 calculations for BC408 scintillator 10x140x2.5 cm3
Light pulse detected at one end
Beam of 500 MeV proton
Depending on hit position
BC408
Number of photons degrades by a factor of 3 while rise time is practically unchanged (about 1.3 ns)
Time resolution is very sensitive to number of photons
For long scintillators σ~ 1 𝑁 𝑝ℎ𝑜𝑡𝑜𝑛     𝑁 𝑝ℎ𝑜𝑡𝑜𝑛 > 10 4

10. Fast PMT properties R4998 R9800 R2083 R5505 R7761 R5924 PMT type
R4998
R9800
R2083
R5505
R7761
R5924
PMT type
linear-focused
fine-mesh
Tube diameter 1” 2”
1.5”
No.stages 10 8 15 19
Q.E. at peak
0.2
0.25
0.23
0.22
Gain (x106)
5.7
1.0
2.5
0.5
10.0
E.Transit Time, ns 11 16
5.6
7.5
9.5
Rise Time, ns
0.7
1.5
2.1
TTS, ns
0.16
0.27
0.37
0.35
0.44
HVmax, V
2500
1500
3500
2300
Time Transition Spread TTS: inherent PMT time uncertainty in response to a single photoelectron
R4998 and R2083 easily protected with -metal against dipole fringe field of Bz ≈ 70 G

11. Supporting frame, mechanical components
Supporting frame are made of duralumin HX4080E-8 profile
Frame sitting on a rail and horizontal position of the wall can be fixed after alignment
Frame is movable to the service position
Expected total weight is about 800 kg

12. Due to cable length limitation need 4 TRB3 with 18 PADIWA 2 modules
Front End Electronics. Connectivity
TRB platform Trigger and Readout Board
with on-board DAQ functionality fed with LVDS signal (cable < 200cm)
TDC channels .………………… (8 ps)
Max hit rate …………………..… 50 MHz
Connectivity ……………………. 95 Mbytes
PADIWA2 16 channel discriminator - fed with PMT analog signals, produces the LVDS signals both by the front and trailing part of analog signal and use Time Over Threshold TOT method of amplitude correction
PADIWA3 AMPS contains ADC -> direct amplitude measurement
Due to cable length limitation need 4 TRB3 with 18 PADIWA 2 modules

13. HV power supply Two HV patch panels, for left and right side
Power supply, HV negative max 3500 V
Worked out in PNPI for NUSTAR R3B 1000 PMT channels [L. Uvarov, “HVDS the distributed high volt age system for Neuland spectrometer.”]
Active dividers 200 μA current consumption (x 132 ch.)
Produced in PNPI similar to [V. A. Kalinnikov, ” Low powered transistor divider for PMT (in Russian)”]

14. MonteCarlo simulation. Count rates at PANDA HL regime
Total rate
𝐩 elastic peak
𝐩 total
All particle produced in vacuum pipe
e+ e- produced in vacuum pipe from 0 →2
Pbeam, GeV 
MHz K p
MHZ
𝐩 MHz 2
0.39
0.002
0.012
1.07 5
0.6
0.008
0.038
0.95 15
0.96
0.047
0.032
0.82
!! Binning is 10 cm (width of slabs in the wall side part), including central part !!

15. Detection efficiency for different type of particles
Number of detected particles for 107 interactions
Detected by BToF
Detected by DToF
Detected by FToF
N, x106
eff π-
4.08
0.36
0.14
0.01
2.59
0.23 π+
5.03
0.44
0.03
0.002
2.07
0.18 K-
0.09
0.0004
0.001
0.1
0.26 K+
0.25
0.003
0.046
0.12 𝐩
0.04
0.007
0.0002
3.24
0.62 p
3.19
0.61
0.012
0.35
0.07

16. Hit distributions for different type of particles

17. 𝚲 detection Event selection criteria
Pair of opposite charged hadron in events
𝑚( ℎ − )= 𝑚 𝑝 , 𝑚( ℎ + )= 𝑚 𝜋
𝑚( ℎ − )= 𝑚 𝑝 , 𝑚( ℎ + )= 𝑚 𝜋 , ToF criteria 𝛥 𝑡 𝑠𝑡𝑎𝑟𝑡 𝑝 𝜋 +  > 100 𝑝𝑠
Λ detected with high efficiency (~20%) at weak selection criteria
 events also well detected
At 106 interactions/s (normal luminosity mode) N Λ ≈4× s-1 !!!

18. PID in event base simulation
p = 5 GeV/c
p.d.f for different particle types
p = 0.5 GeV/c
Track length and momentum from FTS
ToF time from FToF
Velocity 𝛽= 𝐿 𝑡 𝑇𝑜𝐹
Separate particle by 
p.d.f for different particle types

19. T0 and PID determination
𝑡 1 𝑇𝑂𝐹 = 𝑡 0 + 𝐿 1 𝑐 𝛽 1 = 𝑡 0 + 𝐿 1 𝑐 𝑝 𝑚 𝑝 1
𝑡 2 𝑇𝑂𝐹 = 𝑡 0 + 𝐿 2 𝑐 𝛽 2 = 𝑡 0 + 𝐿 2 𝑐 𝑝 𝑚 𝑝 2
………
𝑡 𝑛 𝑇𝑂𝐹 = 𝑡 0 + 𝐿 𝑛 𝑐 𝛽 𝑛 = 𝑡 0 + 𝐿 𝑛 𝑐 𝑝 𝑛 2 + 𝑚 𝑛 2 𝑝 𝑛
n equations and n+1 unknown variables 𝑡 0 , 𝑚 1 , …, 𝑚 𝑛
𝑚 can be only 𝑚 𝑝 , 𝑚 𝐾 , 𝑚 𝜋 , 𝑚 𝜇 or 𝑚 𝑒
𝐿 and 𝑝 provided by tracking
Loop over all possible ( 5 𝑛 ) combination and find right one
TOF hits
Need N ≥ 2 hits and can be done only offline, additionally provide T0
𝑡 𝑜 𝑒
𝑡 𝑜 𝜇
𝑡 𝑜 𝜋
𝑡 𝑜 𝐾
𝑡 𝑜 𝑝
time
1st hit, p = 5 GeV
2nd hit, p = 1.5 GeV
3rd hit, p = 0.5 GeV

20. No dedicated start counter. Hit multiplicity distributions
Pbeam = 10 GeV
Pbeam = 5 GeV
Condition for ToF analysis (Nhits ≥ 2) at 10 GeV
εBToF = 48%, εFToF = 38% and εBToF or FToF = 80%

21. T0 and PID algorithm with PandaROOT
Events with only 3 FToF hits and beam momentum 15 GeV/c, ToF = 70 ps
PID calculated using combinatory algorithm, colors correspond MC particle type
PID quality (separation power) for all particle momentum
~20% for p/K separation
~10% for /K separation
T0 resolution 90 ps

22. Prototyping. Test stand layout for PMT measurments
2 MeV energy deposition
2x104 photons
Measured are TDC_1, TDC_0
Common start for all TDCs, QDC_1, QDC_0

23. Anode pulse rise time (ns)
PMT characteristics
PMT
Photocathode
diameter (mm)
Anode pulse rise time (ns)
Transition time (ns)
TTS (ps)
Gain / 106
Typical voltage (V)
R4998
25 (1 inch)
0.7 10
160
5.7
2250
R9800
1.0 11
270
1.1
1300
R2083
51 (2 inch) 16
370
2.5
3000
R9779
1.8 20
250
0.5
1500
XP2020
1.6 28 ?? 30
2000

24. Test station results TDC1 gives raw t1 – t0 distributions
Typical σTDC1 (raw) about 160 ps
Offline amplitude correction 𝑇𝐷 𝐶 𝑐𝑜𝑟𝑟𝑒𝑐𝑡𝑒𝑑 =𝑇𝐷 𝐶 𝑟𝑎𝑤 −𝐴 1 𝑄𝐷 𝐶 1 − 1 𝑄𝐷 𝐶 2
Corrections for start uncertainty, track walk and electronics 2𝜎 2 𝑅2083 =𝜎 2 𝑇𝐷 𝐶 1 𝑐𝑜𝑟𝑟 − 𝜎 𝑠 2 − 𝜎 𝑒𝑙 2 , 𝜎 𝑡𝑟𝑎𝑐𝑘 2 =15.8  𝑝𝑠, 𝜎 𝑒𝑙 2 =31.5 𝑝𝑠
PMT_1
σTDC_1 (ps)
σPMT (ps)
R4998 (4998/4998)
72.
44.4
R9800 (4998/9800)
86.
64.6
R2083 (2083/2083)
72.6
44.9
R9779 (2083/9779) 64
56.5
XP2020 (2.5, 2.36kV) 82
52.3
σTDC_1 after offline amplitude corrections
σPMT after corrections for start uncertainty, track walk and electronics

25. Beam tests at 1 GeV PNPI SC
1 GeV proton beam and polyethylene target
Scattered protons
Count rate 103 to 106 /s cm2
Energy Ep=740 and 920MeV, σ(Ep) about 0.5%
S3S4 scintillation slabs B408:
Size (140)x(5/10)x(1.5/2.5) cm3
Energy deposition ≈ 5 MeV
S1 and S2 size 2 x 2 x 2 cm3
Scintillation efficiency ~104 photons/MeV
PMTs R4998, R2083, Electron187

26. Prototyping using proton beams
PNPI 1 GeV synchrocyclotron
740 and 920 MeV protons selected with magnetic spectrometer
COSY test beam in Juelich 2 GeV MIP protons
Slab put horizontally in spectrometer focal plane at movable frame
MWPCs provide hit position with σt = 1.8 mm precision
1 mm → 5.9 ps time uncertainty

27. Offline time resolution
“Raw” time resolution can be substantially improved due to time-hit position and time-amplitude correlations
Correction is done on event-by-event basis using correction function:
𝑡 𝑖𝑘 = 𝑡 𝑖𝑘 𝑟𝑎𝑤 − 𝑓 𝑐𝑜𝑟𝑟
𝑓 𝑐𝑜𝑟𝑟 = 𝑡 𝑖𝑘 𝑟𝑎𝑤 −𝐴𝑥−𝐵( 1 𝑄 𝑖 − 1 𝑄 𝑘 )−𝐶
tik , tikraw corrected and raw TDCi-TDCk distributions, x hit position, A,B,C constants to minimize functional:
𝑡 𝑖𝑘 2 − 𝑡 𝑖𝑘 2 = 1 𝑁 𝑛=1 𝑁 𝑡 𝑖𝑘,𝑛 2    − 1 𝑁 𝑛=1 𝑁 𝑡 𝑖𝑘,𝑛     2
TDC Hit position correlation
hit position
correction
pulse amplitude
correction
TDC QDC (amplitude) correlation

28. Offline time resolution
920 MeV, position x = 60cm, Scintillator 2.5x5x140 cm3, R4998
Raw spectra
After amplitude and hit position correction

29. Timing resolution results from 1 GeV PNPI SC
1 𝜎 𝑇𝑂𝐹 2 = 1 𝜎 𝑇𝐷𝐶 𝜎 𝑇𝐷𝐶4 2
σTOF vs hit position

30. Scintillation slab dimensions (cm) Timing resolution σ (ps)
Time resolution on beam tests
Scintillation slab dimensions (cm)
PMT
Timing resolution σ (ps)
Comment
140 × 10 × 2.5
Hamamatsu R2083
(both ends) 63
Recommended for a prototype for the FTOF wall.
140 × 5 × 2.5
Hamamatsu R4998 (both ends)  60
Recommended for a prototype for the FTOF wall
140 × 2.5 × 2.5
Hamamatsu R4998 43
a variant of a prototype with smaller scintillator width
140 × 5 × 1.5
Hamamatsu R4998 (both ends) 88
projected originally for the FTOF wall
Electron PMT 187 (both ends) 78
magnetic field protected
1 × 1 × 1
Electron PMT 187, Hamamatsu R4998 49
“net” timing resolution of one PMT

31. Cost matrix 471k€ In Russian list of expression interest Item cost, €
Plastic scintillator EJ x10x2.5 cm3, 46+4(spare) units
33 800
Plastic scintillator EJ x5x2.5 cm3, 20+5(spare) units
11 500
PMT Hamamatsu R2083 (2”), 92+8(spare) units
PMT Hamamatsu R4998 (1”), 40+10(spare) units
83 600
Light guides, optical cement
16 500
Supporting frame
15 000
Readout electronics, TRB-3, Padiwa-3
25 000
Active dividers (80€/unit)
10 500
HV power supply (90€/unit)
12 000
LV power supply
2 900
Laser calibration system
20 000
Mechanical components (PMT housing, μ-metal)
9 000
Transportation, custom taxation
Equipment for tests and mass production
Total
471k€ In Russian list of expression interest

32. Conclusion
Size of wall is 5.6 m (width) x 1.4 m (height) x 2.5 cm (thick)
Bicron BC408 plastic scintillator
Hamamatsu PMT R4998 (1 inch) and R2083 (2 inch)
MC simulation demonstrates important functions of FTOF wall:
PID of forward emitted particles with momenta below GeV
determination of event start time stamp
possibility to use Λ for detector calibration
Maximum count rate in central part of FToF wall at L = 1032 cm-2 s-1 is below 3x106 s-1 . Background related to e+e- pairs production peaked at very low momenta is small.
Measured timing resolution on prototype with 920 MeV protons (offline, after hit position and amplitude corrections)
Only PMTs and front-end electronics  = 45 ps
140 cm x 10 cm x 2.5 cm BC408 scintillator + PMT + FEE  = 60 ps
Without hit position information, timing resolution of 80 ps has been obtained.

33. Outlook and milestones
TDR approved (M3) …………………………………………………………….…
Working place for assembling and tests of scintillation
counter modules organized ………………………………………………..…
Funding established ..………………………………………………………..…
Contract is signed …………………………………………………………………
Tender completed ………… ………………………………
Procurement of necessary equipment for tests and
calibrations (components not yet available) completed .……
Procurement materials for mass production
(scintillators, PMTs, etc) completed …………………………………..…
Fabrication of mechanical items completed ……………
Assembly, tests and calibration of scintillation modules ………
Preassembly of the FToF wall …………………………………………………
Shipment to GSI ……………………………………………………………………
Integration in PANDA detector (M11) ……………………………………
Pre-tests, on beam tests (M12) …………

34. Supporting slides

35. Risk assessments Risk item Probability Impact Mitigation measures
Lack of manpower after 2016
not small
Worsening detector tests and calibration. Extra time for mass production
Search for additional funding. Search for PhD students
Not sufficient financing for detector fabrication
Not full scale detector (e.g. less FToF wall sensitive area) or worse timing resolution
Search for additional funding like grants etc. Procurement of less expensive PMTs
Timing resolution is worse than 100 ps
Low
Low PID quality
Thorough tune and calibration using picosecond laser setup
Lack of travel money
high
Problems with detector installation, maintenance and data taking
Try to find additional financial support

36. Prototyping summary
The time resolution of 60–65 ps was obtained for the scintillation counters recommended for prototypes for the FTOF wall.
The time resolution of 50 ps was obtained for the slabs of 2.5 cm width. Practical application of such slabs however would result in increase of number of channels which may confront the detector cost limitation.
The time resolution of 80 ps was obtained for the scintillation counter based on the slab of 2.5 cm width viewed with the Electron PMT 187. These mesh PMTs can operate in magnetic fields up to 0.5 T without deterioration of time resolution.
Samples with slabs of 1.5 cm thickness originally projected for the FTOF wall showed essentially worse time resolution than those of 2.5 cm thickness.
A precise measurement of the hit position seems crucial to get the timing resolution on the level of 60 ps. Without independent information on hit position, the timing resolution of 80 ps has been measured. .
A satisfactory result was obtained for KETEK PM6660 samples at test station. A raw timing resoluton of σ = 71 ps (per a SiPM sample) was directly measured , and after corrections it was obtained σPM6660 = 66 ps. The measurements with large scintilltors has not yet been done.
A very tentative test of radiation hardness of SiPMs has been made in PNPI using not powered S p SiPM (3x3 mm2) sample exposed to 1 GeV proton beam. It was found that the radiation dose equivalent to x protons having passed through the active area of the sample is crucial for its operation capabilities.

37. Open questions MC simulation. Related to FSTT.
- time dependent event reconstruction analysis
Related to FSTT.
- FS momentum resolution Δp/p must be 1%
-vertical hit position uncertainty ? Δy=1 mm corresponds 5.3 ps (BC-408)
expected at present design FSTT Δy=5-10 mm → up to Δ(tof) ≈ 60 ps
-uncertainty in track reconstruction? ΔLtrack / Ltrack = 0.1% → Δ(tof) ≈ 30 ps
FTOF wall position behind RICH.
- RICH width is smaller than sensitive area of FTOF wall, deterioration of track information at FTOF wall side slabs
FTOF wall width is 5.6 m while FSTT last station width is 3.9 m, thus side parts of FTOF wall are out of FSTT acceptance.
reduce FTOF wall width ??
Hardware:
- finalize TRB-3 readout tests
- definitive decision on Hamamatsu PMs (type, housing, divider, price,.).
- on-line laser calibration system (??)
- HV-power supply: commercial or
PNPI production HVDS3200 designed for Nustar R3B FAIR (neutron detector)

38. Time resolution without hit position correction

39. SiPM timing tests after corrections σ =103 ps
Amplitude correction
variant A S10931
after corrections σ =103 ps
variant B KETEK 6660
after corrections σ =65 ps

40. PC Application of TRB-3 readout underway in PNPI generatormV
Peak posit. σ ps
100
540
31.5 75
530 50
520
33. 40
34. 30
36. 25
510
Needs more expertise

41. Time and hit position measurements using TDC information onlyx
(T41-T31)/2
σ431-
(T41+T31)/2
σ431+
(T42-T32)/2
σ432-
(T42+T32)/2
σ432+ cm ps 60
1504 99
11950
148,5
1503,5
100,5
11580
120,5 40
2770,5 74
11865
138,5
74,5
11510
102 20
3904
90,5
11975
145,5
11630
114
5025 76
11920
136,5
75,5
103,5
-20
6255
81,5
11940
150
82,5
115,5
-40
7460 84
11895
143,5
6890 85
11560
112,5
-60
8655
93,5
11945
11600
121
vBC408 = 1/59.12 = 0.17mm/ps
speed of light in BC408 = 0.19 mm/ps
hit position resolution
80ps x 0.17mm/ps = 13.6 mm

42. Cost estimation update
FTOF wall Plastic scintillators B408 20u.140x5x2.5cm+46u.140x10x2.5cm 40 k€ PMTs 1” 760 € 40u. +5u.(spare) 42 PMTs, 2” 1270 € 92u.+20u.(spare) 155 FEE+DAQ 35 HV power supply 22 Monitoring/calibration system 25 Supporting structure , mechanical items 75 Test stand for mass production 35 Transportation, custom expenses 42 ……………………………………………………………………… 471 k€
From RRB February k€

43. LIGHT GUIDES FOR 1” AND 2” PMTs
Plexiglas, Mylar
wrapping,
Magnetic field protected housing

44. Dipole TOF positioned inside the dipole magnet gap as planned for TDR
Projected 2x10 scintillation slabs 80÷100x10x2.5cm
readout from each end with Electron PMT 187
Diameter mm
Photocathode mm
Anode pulse rise time ns
TTS ≈500ps
Gain x105
W.m. emission nm
( 80% at 420nm)
HV v
tested in magnetic field up to
0.5T
Not sensitive to mag. F.(!)
SiPMs(hamamatsu)
S p, S p
active area 3x3mm
Pixels
Gain x105 – 2.4x106
W.m. emission nm
TTS ns(FWHM)
Alternative solution SiPMs
provided timing resolution better
than 100ps
radiation hardness??