Minutes from weekly target meeting held 18th of July 2002 in 888

a) Jaakko added three more pt100s during the MD to monitor: magnet gHe outlet 
pipe, top of the still pumping line bellows connection (rubber o-ring) and 
thermalised Q-meter boxes.

b) The solenoid PSU current lead connectors were inspected visually. They were
ok and no sign of excessive heating was observed.

c) Yuri and Gerhard found that the modulation frequency of microwaves 
affects the noise seen in the polarisation measurement. Changing frequency
from 500 Hz to 1000 Hz makes the polarisation measurement more stable
due to the thermal inertia of thermometers.

d) Fabrice is trying to find a way to communicate the solenoid current
value during field rotation to the spectrometer data stream. Jaakko suggested
to use the magnet parameter data stored on the Sun disk, but for the 
online monitoring this possibility is not so practical.

e) Norihiro made a new interlock to the still heater. If still pressure
PV8 > 10 mbar, the still heater is switched off automatically. This helps to 
keep the polarisation in case the roots blowers are stopped. The dilution 
cryostat interlock scheme needs to be updated. For better automatisation a 
PLC is needed. Jaakko and Norihiro are investigating this possibility.
This would mean starting with simple system of CERN IT/CO supported PLC
Simatic S7-300, which could later be expanded if needed. Good human
interface (preferably flexible) would also be necessary. More info
http://itcowww.cern.ch/plc-web/plcpage.html . 

f) During the MD the NMR signals of D, 6Li, 7Li, 3He and p were taken by Kaori
both in positive and negative fields. There was also discussion about more
systematic study of the effect of microwave power on the polarisation 
measurement. Gerhard presented idea of doing check after the beam time at high
temperature around 1 K. The polarisation loss due to short spin relaxation
time is monitored continuously. Finally polarisation should reach the thermal
equilibrium value close to zero. For near future, the checks that can be
done during MDs were discussed. In addition to the NMR frequency shift,
the ESR shift could also be used to verify the polarisation difference
between upstream and downstream target cells. For this the IMPATT diode 
microwave source is preferred due to its lower noise although the ESR lines
can also be measured with the EIO tubes. In any case the corrections
and verification methods to the 2002 polarisation data need to be discussed 
and investigated more deeply.

g) Jaakko is looking for a spear oil filter and exchange oil for Alcatel rotary
pump 3631B used to pump the evaporator. The oil is now a little brownish and 
the power consumption of the pump may have increased from last year (we had 
the fuse problem in the pump room). Thus the oil filter may have to be to be 
changed during the beam time. At least this should be done after the beam 
time due to the continuous operation exceeding 3000 h.