Minutes (Carsten Schwarz)

PID Cerenkov group meeting

Roman Dzhygadlo, GSI: DIRC Prototype Test 2017

Roman showed results of the CERN2017 beam experiment in the T9 area.
A new 33 degree prism as expansion volume was used read out by
12 MCP-PMTs. The MCP and the 4 PADIWA discriminators were combined
in a mechanically stable module. A new 3-layer cylindrical lens (eRD14 funding)
was tested with a narrow bar and a plate as the radiators (plate for the EIC DIRC).
The setup was improved to study the impact of azimuthal angle on hit pattern,
PID performance. In summary, the Time resolution of the system was determined
to be ~250 ps. The pi/p separation has improved compared to 2016.
The cylindrical lens was validated and a good agreement between data and simulations
were observed.

Erik Etzelmueller, Giessen: Gluing Tests for the PANDA Endcap Disc DIRC

Erik showed test results of gluing tests of NOA-61, Epotek301-2 and APM-Epicol.
He presented the setup and the procedures to apply the glue between
fused silica pieces. For the NOA61 he observed the creation of bubbles and
fern-like structures while curing. The UV curing of NOA-61 involves the risk
of defects if curing is not done homogeneously. The other glues did not show this effect,
they cured by time. It is planned to perform radiation hardness tests and to measure
the spectral transmission.

Simon Bodenschatz, Giessen: Construction of a Cosmic Test Stand for Particle Detectors

Simon showed the test stand for muon detection in Giessen. The setup consists of
Two scintillating plates defining a trigger and four layers of
scintillating bars  for the track reconstruction. The energy selection is done by
45 cm of lead between the trigger plates. Simulations show an expected polar angle
of 3.2 mrad an azimuthal angle of 20.4 mrad, and a spatial resolution of 4.5 mm.
First measurements with TOFPET (and TOFPET2 eval.-Kit) have been performed.

Jana Rieger, GSI: Optical measurements of the radiator shape

Jana showed the squareness and parallelism measurements of radiator
bars measured with an autocollimator. Choosing the right mechanical suspension of
the radiator bars, she compared prototypes from different manufacturers.
A very good reproducibility of 0.01mrad was achieved. The Zeiss and Insync bars
fulfill detector specifications, Zygo is close to specifications. Heraeus and
Lytkarino bars did not fulfill the specifications. The measurement setup can be
used in future for quality assurance of mass production detector bars.

Carsten Schwarz, GSI: Next focusing lens for the Barrel DIRC

Between the radiator bar and the readout plane with the photon detectors a lens system
was used to get sharp Cherenkov images. Carsten showed the development of lenses from a
single lens with air gap up to a three layer lens with flat focal plane. The chosen material
LaK33 is radiation hard for the the lifetime of the PANDA experiment. The next iteration of
the design for the lenses is a group of three lenses side at side. This design,
if working, will become the final design for the detector.

Markus Pfaffinger, Erlangen: Update on lifetime measurements and first results with new Photonis tube

Markus showed results of a new Photonis XP85112-Q-HA tube with high collection efficiency.
It has ~20-23 % QE at 300-400 nm. He tried different voltages in HV-divider between
photocathode and first channel-plate. The highest voltage of 750 Volts minimized the
contribution of back scattered electrons to the timing resolution. he also showed the
updated values of lifetimes.

Merlin Boehm, Erlangen: Setup and first results of quality assurance measurements with MCP-PMTs

The quality assurance (QA) of the ~300 MCP-PMTs for the DIRC detectors need a
measurement setup. He showed a setup which uses surface scans using a 3-axis
stepper with a PILAS Laser. A TRBv3 and PadiwaAmp2 DAQ system measures time resolution,
cross talk, dark count rate, and after pulsing, in future  also gain. He measures timing
resolutions with the scope which are is much better compared to the TRB system.
Scope: ~65 ps, timewalk corrected ~50 ps
TRB: ~180 ps, timewalk corrected ~145 ps
for the Photonis XP85012 #1356.

Steffen Kraus, Erlangen: Results with the 2 inch Hamamatsu YH0250

It is  a 2x2 inch 8x8 pixelised MCP-PMT with no Al2O3 foil in front of the first channel-plate.
The QE measurements show a high QE of 26-30%, with the highest QE area between 350 and 450nm.
The gain is 10^6 and the rate capability fullfills the PANDA requirements.
The tube had a timing resolution of sigma=36 ps.

Klaus Foehl, Giessen: Update on MCP-PMT investigations

Klaus inspected Photonis MCP-PMT Photonis, MCP-PMT Hamamatsu YS0026, and MCP-PMT Hamamatsu JH0245.
He observed for the Photonis MCP variations in the current of up to 2%. The Hamamatsu tubes
showed geometrical structures on the photocathode and channel-plate front. He got the
recommendation to test the tubes with carefully increasing the HV with a Pilas-Laser, or
to send back the tubes to the companies for inspection.

Erik Etzelmueller, Giessen: Common Trigger for the 2018 Test Beam

Erik discussed the trigger for the upcoming experiment at CERN. Since the
trigger and timing signals can be splitted it turns out, that there is no problem.