Cherenkov group meeting, Stockholm, 5-June-2018

Roman Dzhygadlo, GSI, Update on the Barrel DIRC Prototype Test @
CERN Aug 23 – Sep 13, 2017

Results from the prototype test with the 33 degree prism, an arrangement of
3x4 MCP-PMTs and the 3-layer lens from eRD14 were shown. The timing resolution
for laser runs was 250ps after walk correction. The geometrical reconstruction
for the bar with the 3-layer lens yields a single photon resolution of 9.1 mrad
corresponding to 4.25 sigma separation power at 20 degree for pi/p.

Erik Etzelmüller, Giessen, Update on the Endcap Disc DIRC

Erik showed results for the gluing tests with APM Epicol, Epotek 301-2, and
NOA-61. Loads with 15 Nm lead to deformations of 80 um. NOA-61 failed
even at low loads. The transmission curves of the glues were measured. NOA-61
showed a clear drop below 400 nm. Also the transmission curves of
dichroic filters were taken. They show a shift depending on the incident angle
which becomes larger if the filters are placed between fused silica pieces.
A setup for measuring the focusing elements is being prepared, the
cosmic test stand further equipped. A front end electronics board for the
TOFPET chip is being developed. The electronic setup for the next test beam
2018 at CERN was introduced.

Markus Pfaffinger, Erlangen, Results with Gießen Sensors and
update on lifetime measurements

Markus showed an update of the aging tests for the MCP-PMTs.
The Hamamatsu YH0250 was added. Most sensors with ALD coating have life times
larger than 5 C/cm2 while the non ALD devices have smaller 0.2 C/cm2. The
double ALD Photonis tube (1393) has now 19 C/cm2 without damage.
Tests in Juelich for the behavior in magnetic fields are prepared.

Merlin Böhm, Erlangen, Update for quality assurance measurement setup
for MCP-PMTs

Merlin prepares the setup for the quality assurance of the MCP-PMTs for PANDA.
An x-y-table allows for the scanning of the devices with 5 um position
accuracy. He showed the scan of the Hamamatsu  R13266-07 YH0245. He observed a
huge noise of 15 mV which needs to be closer investigated. Also cross-talk
and after pulsing measurements were performed. The time resolution
measured with the TRB and PADIWAmp2 was in the order of 130 ps similar to
results with PADIWA1 and PADIWA3.

Albert Lehmann, Erlangen,Origin of time-over-threshold multi-peaks

Albert looked to coherent excitations of MCP-PMTs which were already known
from the PLANACON MCP in 2005. He showed that with increasing photon
illumination pixels start to coherently ring. Also Hamamatsu YH0250 shows
this effect. The ringing starts if ~6-8 photons hit the detector.
When ringing is there low thresholds create multi-peaks in TRB
ToT and osci pulse heights