PID Cherenkov Session at CM 20/3

Minutes of the PID-Cherenkov group

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

The Barrel DIRC has received 90 of 98 ordered bars ~5 months ahead of schedule.
All bars meet the fabrication specs. Procurement of 8-14 additional bars is
in preparation. The closer inspection in the GSI-Laser lab reveal
shape deviations and striae which are minor and are no reason not to
accept the bars.

Sophie Kegel, JLU, Quality measurements of the EDD radiator

The measurement of a laser going through the prototype radiator horizontally
show a displacement between observed and expected position of less than 0.5 mm.
It is not clear if this is a surface or bulk effect.
Inclined angles show the expected positions.

Simon Bodenschatz, JLU, Giessen Cosmic Station - Current Measurements

The plan to measure the prototype radiator within the Giessen Cosmic Station
is followed up. Several little problems like light tightness,
clean room temperature and stability of low power supplies were identified and
will be solved soon. The cooling of the readout board will be done in future
by a liquid coolant, first planning and design has started. 

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

Most sensors with ALD coated MCPs have lifetime > 5 C/cm², the requirement for
10 years of PANDA operation. The Photonis and Hamamatsu tubes meet this
requirement, the Photek tubes show cathode damages probably caused by micro
leaks.

Steffen Krauss, FAU, Results of the B-field measurements

MCP-PMTs from Photonis (9002192, 9002193) and Photek (A1200107, A1200116,
A2200606, A3191220) were measured in a dipole magnet in Juelich
up to a magnetic field of 2 Tesla. Up to 1 Tesla all tubes show a gain
larger than 1e6 even when inclined up to 20 degree which is sufficient
for the Barrel DIRC. Unfortunately, an accident occurred measuring the
Photek A1200107 in the magnetic field. The rate increased to few MHz and the 4
DIRICH readout boards have been destroyed. The measurements done later with
PADIWA discriminators are not yet understood and the analysis of this accident
is going on.

Merlin Boehm, FAU, TRB3 linear vs. DCDC Power

Merlin changed the DC-DC converters of the TRB3 to linear voltage regulators and
observed better timing precision for timings measured with TRB3. With
the signal from a laser measured by the MCP-PMT attached to the DIRICH and the
laser trigger measured by the TRB3 the timing improved from 65 ps to 38 ps.
That is about the same timing precision when measuring trigger and signal
both with the DIRICH. Using a DIRICH with 10 pF integrating capacitor,
the signal decrease to 25% compared to the 1 pF integrating capacitor.
The timing precision did not improve.