Minutes from weekly target meeting held 11th of July 2002 in 892

a) Kaori took the NMR signals of 6Li, 7Li, p and 3He during the MD of 
Wednesday both in positive and negative solenoid fields. Jaakko suggested that
the system spin temperature could be used to check or correct the polarisation
results for upstream target cell coils. For this reason regular checking of
NMR signals of all spin materials is useful. This could be done during the
MDs once a week or during the field rotations.

b) Yuri reported that the average polarisation for upstream or downstream does
not depend on the sign of the solenoid field. When polarising the material,
a 3 % drop is observed in measured polarisation. This could probably be 
attributed to change in baseline, thus using parabolic baseline fit the 
problem is expected to diminish or disappear. The difference between upstream
and downstream polarisation is constant between 100 - 104 %.

c) Yuri raised question about the frequency drift of NMR signals observed 
after field rotation. The drift corresponds to change of 20 mA maximum in the
current to the solenoid. Different possibilities including slowly drifting
magnetisation currents inside the material were discussed. Kenneth asked
how stable is the current measurement system. Jaakko said that the 
"shunt-DVM" is measured by using Danfysik Ultrastab 860R current transducer
converting 0 - 600 A to 0 - 10 V. Stability of this device is < 1 ppm/K,
< 1 ppm/month and noise < 2 ppm (there might be influence from external
field though). More careful checking of the drift indicates that it is due to
inherent drift of solenoid PSU, which seems to have stability of about 
10 - 20 mA. According to report by N. Bourgeois from EP/TA3 about the
preparation of the magnet with Naoki from 29 April to 6 May, the cable 
connections from solenoid PSU should be checked regularly (these had melted
during the operation of last year). Thus this should be done during the next
MD.

d) Jaakko fixed one Eurotest trim PSU that could not be controlled from 
external voltage source. The problem was an oxidised soldering of one 
opamp on the PCB.

e) Two pt100s were installed during the MD. One is on the outlet of horizontal
screen. The second is on the top flange of the dilution cryostat. These
should stay between 10 - 60 C in normal operation. They should be checked
regularly for normal operation of heaters and hot air blowers. More 
pt100s will be installed during next MD.

f) Kenneth asked when the LN2 trap should be purged again. Jaakko said that
there is no need to purge it if the pressure drop between the roots outlet P3
and condensation pressure P10 does not start to increase. The ice on the top
of the LN2 trap should be checked regularly, since it might block free 
evaporation of the N2 gas.

g) Kenneth asked if the NMR or dilution monitoring PCs should be rebooted 
regularly for more stable operation. Kaori said that the NMR PC is quite
stable and does not need any special rebooting scheme. Fabrice said that the
problem to the dilution PC comes from the big number of communications.
Gunter asked how to boot the Sun for magnet. Basically one needs to log in
as a superuser (password below the keyboard) and type in "upmagnet". The
VME matrix CPU board should be restarted first. The print out from Falco
terminal tells if everything is ok.

h) The pump room temperature does not need to be set to 16 C (this increases
the power consumption of the ventilation system). Usually 20 C is enough.

g) Gunter proposed a filling list for the LN2 target material dewars.  

i) Ture made the first simulations of the NMR circuit with Aplac student
version.