PID Cherenkov Session at CM 20/2

Minutes of the PID-Cherenkov group

Ilknur Koeseoglu, Giessen, Status of the PANDA Endcap Disc DIRC Project.

The new ASICS from PETsys have arrived. It was tested that they work
with the negative signals of MCP-PMTs. Measurements with the
Photonics-2mm-MCP and an external laser were performed to get the
right thresholds for the ASIC. Some noise issues were addressed.
The tight mechanical constraints can be alleviated by using less
FELs. MC-studies of the impact of the reduction of the FELs on
the EDD performance have started.

Sophie Kegel, Giessen, Quality measurements of the EDD-radiator.

The position of a laser going through the plate varies +- 0.1 mm from
the anticipated position when changing the position in perpendicular
direction. In the horizontal direction deviations of +_0.4mm
were found.  The measurements with the FEL indicate that the angle
preservation inside of the radiator is good enough. 

Avetik Hayrapetyan, Giessen, Upgrading Giessen Cosmic Station (GCS).

One trigger plate of the cosmic station was rebuilt with SiPMs and
tested. It is planned to rebuild and test also the other trigger plate.

Jochen Schwiening, GSI, Status of GSI tendering and procurement.

Jochen gave an update on the situation of the tendering process of the
MCP-PMTs and the status of the radiator bar production at Nikon.

Georg Schepers, GSI, Nikon Bar Production Status of Delivery and
Acceptance

The specs in the data sheets of Nikon QA are met or exceeded.
The delivered bars are visually inspected, the bar shape checked
with the autocollimator and the internal reflection measured with the
laser setup at GSI. Observed “beam steering” are consistent with
reflections from non-flat surfaces and/or steering from layers of
varying refractive indices (striae).  The Nikon CMM data and the
laser measurements show combinations of convex and concave shapes
varying across the length of the bars. But the striae and deformation
of sides are no reason not to accept the bars.

Steffen Krauss, Erlangen, Results of the Photonis XP85112
9002192 & 9002193 2x2 inch² MCPPMTs.

The measured spatial QE distributions are homogeneous within 0.5%
except in the corners. The gain distribution is comparable with
previous Photonis tubes, the 10e6 gain is everywhere reached.
The rate stability for  both tubes reach the Barrel DIRC requirement
but are not good for EDD. With a photo cathode voltage modification 100ps
timing precision was reached. The dark count rate, after-pulse probabilities
and cross talk behaviors are moderate and work for the PANDA-DIRCs.

Daniel Miehling, Erlangen, Update on lifetime measurements of MCP-PMTs

The requirements of > 5 C/cm2 at 10e6 gain are met for the Photonis and Hamammatsu
ALD MCP-PMTs. The best detector of Photonis is now at 26 C/cm2  and for Hamamatsu
the JS0035 is now at 12 C/cm2., the  YH0250’s QE started dropping at ~9 C/cm2.
The three ALD Photek tubes A3191220, A1200107 and A1200116 show already aging
effects below 1 C/cm2.