11.3 MuTRiG Performance
11.3.4 Time Resolution measured with MuTRiG
The cluster time resolution, extracted as described in Figure 11.2.3 and Figure 7.3.4, at different
SiPMarray bias voltages are summarized in Table 11.4. The extracted time resolutions for all clusters (cl ≥ 1) and for clusters consisting of at least two (cl ≥ 2) column hits per side are quoted. Figure 11.21 shows an example time difference distribution for clusters with a minimum size of 2, obtained with a sensor biased at 58.2 V. It agrees very well with the time resolution extracted by theDRS4basedDAQof the same ribbon. For example, theFWHM/2.35
7nPS= 1.6.
8Hamamatsu S10362-11-050P.
CHAPTER 11. MUTRIG
right side fit mpv: 2.88 left side fit mpv: 3.20
0 2 4 6 8 10 12 14
cluster size [col]
0.5 1.0 1.5
model/data counts
Figure 11.20:distribution of cluster sizes of a 4 layerSCSF-78ribbon without additional TiO2in the glue measured withMuTRiG. Note that on the right side one channel (27) is missing.
11.3. MUTRIG PERFORMANCE
Table 11.4:Scintillating fibre prototype time resolutions at different sensor bias voltages for all clusters (cl ≥ 1) and for clusters consisting of at least twoSiPMcolumn hits per side (cl ≥ 2).
Furthermore, the time resolution at different threshold levels is presented. If noσbaseis given, it con-verged to 1 ns used as lower bound to prevent dilution ofσcore. Fibre type 78 in the table corresponds to KuraraySCSF-78, NOL toNOL-11.
ribbon th cl bias FWHM2.35 σsingle σcore,σbase Ncore/Nbase
type layers [phe] ≤ [V] [ps] [ps] [ps]
78 4 0.5 1 57.2 391±20 420±2 388±7, 1524 16.14 78 4 0.5 1 58.2 380±18 409±3 382±6, 2054 19.60 78 4 0.5 1 59.2 368±9 405±2 376±4, 3612 19.79 78 4 0.5 1 60.2 376±15 403±2 366±3, 1e5 15.02
78 4 0.5 2 57.2 379±18 398±2 373±4 15.59
78 4 0.5 2 58.2 366±13 389±3 366±5 16.89
78 4 0.5 2 59.2 358±7 386±2 366±7, 1101 19.95 78 4 0.5 2 60.2 366±14 385±2 368±8, 1642 29.66
78 4 0.5 1 58.2 356 403 363 9.80
78 4 ≈1.0 1 58.2 371 415 369 8.54
78 4 DAC0 1 58.2 431 472 401 5.5
78 4 0.5 2 58.2 345 383 360 16.43
78 4 ≈1.0 2 58.2 372 396 365 12.44
78 4 DAC0 2 58.2 403 435 390 8.74
78 3 0.5 1 58.2 413±13 456±1 409±5, 1674 11.74 78 3 0.5 2 58.2 374±19 385±2 363±4, 2792 24.21 NOL 4 0.5 1 58.2 381±4 424±1 385±4, 1000 10.14 NOL 4 0.5 2 58.2 360±17 367±2 353±6, 1081 27.28
CHAPTER 11. MUTRIG
mean 0 ps
core 359 ps
base 811 ps Ncore/Nbase 10.54
single 389 ps
exp gauss 2984 ps
exp gauss 300 ps fwhm/2.35 366 ps
4 2 0 2 4
tleft tright [ns]
5 0 5
modeldata datamax [%] counts
Figure 11.21:Time Resolution of a 4 layerSCSF-78ribbon without additional TiO2in the glue ex-tracted from clusters with at least 2 active columns. No channel by channel time offset correction is applied.
11.3. MUTRIG PERFORMANCE
400 420
single [ps]
cl 1
cl 2
57.0 57.5 58.0 58.5 59.0 59.5 60.0
bias voltage [V]
360 380 400
fwhm 2.3 [ps]5
Figure 11.22:Measured time resolution as a function of the sensor’s bias voltage.
obtained in the MuTRiG measurement of (366±13) ps lies very well inside the uncertainty of (361±23) ps obtained in the full waveform test beam analysis.
Bias Voltage Dependency
A small improvement of the time resolution with increasedSiPMbias voltage is observed. Fig-ure 11.22 illustrates the effect which is of the order ofO(10 ps).
Threshold Dependency
In addition to the time resolution at different bias voltages, Table 11.4 lists the time resolution at different threshold levels. In addition to the default 0.5 pheT-threshold level,≈1 pheand allT-thresholdDACsat a value of 0 are used. Increased thresholds worsen the time resolution.
Position Dependency
Table 11.5 lists the measured time resolution and the time offset of the time difference peak as a function of the source position along the fibre ribbon. A linear fit determines a propagation speed in the fibre ribbon of (0.255±0.003) c. The time resolution shows no source position dependency.
Channel Rate Dependency
Figure 11.23 shows the cluster time resolution of clusters with at least two hits from a 4 layers
NOLfibre ribbon prototype as a function the mean rate per MuTRiG channel caused by passing particles. The horizontal error bars correspond to the rateRMSbetween all channels. For such
CHAPTER 11. MUTRIG
Table 11.5:Time resolution and time difference offset for different source position along the fibre ribbon.
th cl position meanµ FWHM2.35 σsingle σcore Ncore/Nbase [phe] ≤ [mm] [ps] [ps] [ps] [ps]
0.5 1 0 -18 371 403 365 9.98
0.5 1 44 545 385 405 363 9.18
0.5 1 70 921 381 405 362 9.00
0.5 1 100 1275 366 402 364 10.15
0.5 2 0 -24 358 384 360 16.32
0.5 2 44 538 369 384 361 16.36
0.5 2 70 913 363 383 361 17.03
0.5 2 100 1267 355 380 361 20.36
Figure 11.23:Cluster time resolution of clusters with at least two columns extracted from a 4 layer
NOLfibre ribbon prototype as a function of the mean rate perMuTRiGchannel caused by passing particles. The horizontal error bars in rate correspond to the rateRMSbetween all channels.
370 380
single [ps]
340 360 380
fwhm 2.3 [ps]5
0 50 100 150 200 250 300 350
mean signal rate per channel [kHz]
340 360 380
core [ps]
11.3. MUTRIG PERFORMANCE
mean 333 ps
core 341 ps
base 788 ps Ncore/Nbase 10.36
single 370 ps
exp gauss 3094 ps
exp gauss 284 ps fwhm/2.35 355 ps
4 2 0 2 4
tleft tright [ns]
5 0 5
modeldata datamax [%] counts
Figure 11.24:Time resolution of a 4 layerSCSF-78ribbon without additional TiO2in the glue ex-tracted from clusters with at least 2 active columns. Channel by channel time offsets are corrected for.
signal rates up to≈300 kHz/channel no significant degradation of the time resolution is ob-served with the scintillating fibre detector prototypes. This behaviour differs from measure-ment forPETapplications which utiliszeLYSOcrystals. Due to the raised number of photons, about 1000, the increasedSiPMsignals lead to larger currents through theASIC. A strong coin-cidence time resolution dependency on the channel rate in the order of 2 ps/kHz with an energy cut right below the Compton edge is observed [148]. This effect is believed to be caused by the internal feedback (see subsection C.1.1).
Further Improvements
The cluster time resolution be can further improved by a channel by channel offset correction.
This method is described in Figure 11.2.3. Figure 11.24 shows the improved result with respect to Figure 11.21. The improvement ofO(10 ps) is negligible.
Summary
The time resolutions of the fibre ribbon prototypes obtained by the digitization of the full waveform with aDRS4-based DAQare reproduced by reading out the sensors with MuTRiG (see Table 11.4). The performance dependency on the sensor’s bias voltage (see Figure 11.22),
CHAPTER 11. MUTRIG
threshold levels, particle crossing position (see Table 11.5) and event rates (see Figure 11.23) are presented. Up to an event rate of 300 kHz/channel no performance degradation is observed.
Furthermore, a preliminary channel by channel calibration scheme based on crosstalk in the sensor arrays, as well as crosstalk which is mediated by the fibres between the two ribbon sides, is outlined.
Mechanical and Electrical Integration 12
The sub-detector has to fit into the experiment’s base structure, supplies and constraints from the silicon pixel tracker. In a first part, this chapter summarizes the mechanical constraints and requirements of the sub-detector. In a second part, a sub-detector integration concept including the electrical connectivity, the components of the readout board and detector cooling is proposed.
12.1 Constraints and Reqirements
The limited space for detector mechanical support structure and readout electronics is one of the main challenges of the Mu3e fibre detector. Furthermore, also the volume available for supplies and signal lines is very restricted.