Minutes from weekly target meeting held 30th of November 2001 in 892

a) Kaori had done first TE-calibration signal analysis for D at 1.44 K in
both positive and negative fields. TTH1, TTH4 and baratron were in good 
agreement during the TE-calibration. TTH2 showed 0.14 K lower temperature
at 1.44 K and 0.03 K lower at 0.97 K. Possible reasons for discrepancy: 
temperature difference between the upstream and downstream ends, bad 
calibration of TTH2 (from Dubna), heat leak from the microwave stopper 
to centre of mixing chamber (this is not likely due to low base temperature
of the mixing chamber) or there was still some 3He left inside. Thermometry
needs to be improved. One option is to buy a new calibrated thermometer to
down stream end. The other possibility is to buy a small primary thermometer
like Coulomb Blockage Thermometer based on single electron transistors
( http://www.nanoway.fi/ ).

b) Yuri gave brief summary of his recent analysis of the EPR-data. The 
first theory of DNP in good agreement with experiment had been done by 
Borghini in 1968. Yuri calculated the EPR-line and inverse spin temperature
1/Tss against detuning of the microwave frequency for our case based
on theory of Buishvili, Giorgadze and Davituliani from 1974. To explain
the asymmetric line shape it was assumed that the EPR-line consists
of moving polarisation dependent part and of stationary polarisation 
independent part. This would be natural for spin I = 1, since even in
high polarisation case many of the sublevels m = 0 (m = -1, 0 , +1)
are occupied. For these no shifting of the EPR-line can be assumed, since
they don't change the local field seen by the electrons. These results
were criticised by Naoki, who pointed out that magnetic surface oxygen 
could also explain asymmetric line shapes. Possible improvements to EPR-
measurements were discussed.

c) Jean-Marc LeGoff did MC simulations of the target using Aroma. He estimated
the D0 mass resolution comparing the 21	mm radius and 36 mm radius mixing
chambers. The results are:

> When the mixing chamber radius is decreased two effects occur:
> - The amount of He seen is smaller.
> - A fraction of the tracks which used to go through the hemispherical
> part of the mixing chamber wall start to go trough the cylindrical part,
> and they go at small angle so they see a lot of material.
> 
> The two effects essentially cancel:
> 
> radius        He      Epoxy   He+Ep   target  total
> 21    1.88    5.17    5.62    10.94   17.17
> 36    3.13    4.21    5.48    10.87   17.14
> 50    3.72    3.52    5.41    10.84   17.12
> 
> The computation of the amount of epoxy seen is approximative,
> but the qualitative answer, that the 2 effects cancel, should remain.

Thus from the particle physics point of view new mixing chamber is not needed.
This conclusion is quite different from what can be found from the COMPASS
proposal, where the helium was the most important "extra material" in target.
The difference can be explained by the smaller angle trajectories which are
taken into account in Jean-Marcs calculations and the radiation length that
was neglected in the analysis of COMPASS proposal. It is still a good idea
to buy a new smaller diameter mixing chamber to have a spare if the
present one is broken and to reduce amount of 3He needed inside the mixing
chamber. But for the run 2002 we can keep the system as it is and modify only
the target cells inside the Kevlar-tube.

d) For the DCS we need to make a network connection to the NMR PC. This 
connection is used to communicate the measured polarisation and solenoid
and dipole currents to DCS. In addition we want to start to register
the PT100 temperature sensors that are already mounted to pump room
control panel, many of the roots blower motors and to the top of the cryostat.
This kind of monitoring is useful during beam time especially in the
experimental zone due to limited access. We could include into this list
the vacuum pressure, cooling water pressure, pumps status, NMR-rack
temperature, magnet current lead temperatures and other parameters.

e) The pump room and control room doors have to be kept locked. Gerhard
Mallot made a report to fire brigade about the stolen Iseki IG500 diesel
generator. He was not in favour of changing the pump room lock. We could
get a lock to the door between DAQ-room and target control room.