Andreas Gerhardt, GSI Darmstadt, Barrel DIRC – Material Screening Test Set-Up
The setup aims for the detection of possible impacts on the bar surface caused by
out-gassing of bar box materials. It consists of four independent container for
the radiator bars and material. The system monitoring and data logging is done
by a Siemens SPS S7-1500. The containers can be flooded by an adjustable
nitrogen flow rate in range 0.002…0.1 l/min. Measurements started end of January 2023.
Georg Schepers, GSI Darmstadt, Preliminary Bar Measurement Results during Material Screening
The reflectivity of the radiator bars which go to the material screening setup are
measured by laser reflections before and after exposure to the possible contaminants.
One bar serves as reference bar and is exposed to the nitrogen flow only, two other
bars to samples of CFRP-material. After 14 days of exposure, no drop of the
laser reflectivity was noted.
Carsten Schwarz, GSI Darmstadt, Status of Picosecond Measurements
The talk was originally foreseen in the October meeting last year and skipped due to
organizational issues. The picosecond measurements with the DiRICH give now consistent
timing precision with the results from Erlangen. The FEE-chain is capable of measuring
a timing precision of 50 ps for the single photon signals of a MCP-PMT. The failure in
the past was due to the triggering on the overshoot of the signal due to the wrong
polarity of the discriminator within the DiRICH. This behavior is the consequence of a wrong
message of one of the software tools. The work with the summer students in 2023 have
addressed and solved the problem.
Steffen Krauss, FAU-Erlangen, Status of Escalation Measurements
The so-called escalation of MCP-PMTs was observed the first time in 2020. It is at high gain
the sudden increase of the current with a drop of the gain. While the escalation takes place
photons are emitted by the tubes. It concerns only the latest PHOTONIS tubes with ALD-coating.
By optimizing the ALD process PHOTONIS was able to shift the escalation
starting point to higher gains for newest MCP-PMTs. Steffen observed that the generation of
photons starts already well below escalation of 10^6 gain. Photek & Hamamatsu tubes do not
have this photon creation effect at all. The dark count behavior seen in LAPPD tubes look very
familiar to escalation effect from Photonis.
Daniel Miehling, FAU-Erlangen, Update on CE and Lifetime Measurements
As usual, the lifetime measurement results were shown. The best tube is the PHOTONIS 9001393,
a 2 ALD-layer tube, with ~ 70 years of PANDA integrated illumination (>5C/cm2) and no visible gain drop.
He measured the collection efficiency of the tubes. There is a dependence
of CE value on the voltage divider configuration. Both, gain and number of photoelectrons depend on PC-MCP
voltage (energy of initial electron) and, therefore, the CE is dependent on PC-MCP voltage.
Below a Voltage of 200 V the CE drops significantly. A HV-divider ratio of 4-10-1 instead of 1-10-1 yields
slightly higher CE. The CE measurements are now between 95% and 100% instead of ~90%.
Katja Gumbert, FAU-Erlangen, Results of Measurements of tubes 9002225-9002231
The QA of the latest PHOTONIS MCP-PMTs was done. All reach a gain of 10^6 some even 10^7. At the highest gain
still escalation was observed. The gain uniformity is better than 3 for > 90% active area for all tubes.
The quantum efficiency and its uniformity was measured and found to be less than 1.5
with the exception of one tube. Two of the tubes showed micro leaks and will be returned to PHOTONIS.
The timing precision of the tubes is 115-130 ps RMS for a 4:10:1 HV-divider. Also the dark count rate and
the after pulsing were measured.
Yannic Wolf, GSI Darmstadt, Machine learning algorithms for PID
Simulations provide space and time coordinates of photons for the ML input. He used an 1D image-vector with
time information and shows the result as ROC-curve (Receiver Operating Characteristic). Each angle was trained
separately. The networks were NN, CNN and CNN with time (NN=Neutral Network, C=Convoluted). The goal is to find
the best network for PID.
Ahmed Ali, GSI Darmstadt, Gluing Lab Status at HI Mainz
A radiator bar from Nikon Corp. was sliced into 53 mm-wide pieces using laser ablation.
The gluing results are highly dependent on the quality and alignment of the two
surfaces. Mechanical strength tests were conducted. Shear and peel testing are two common
methods used to evaluate the mechanical strength of adhesives. The tests confirmed the mechanical
strength of the glue joints.
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