Subject: HRI-SIM TV1 Flash Report                                             
Date: Wed, 26 Jun 2002 20:30:14 -0400 (EDT)                                   
From: Dennis Wellnitz <wellnitz@astro.umd.edu>                                
                                                                              
This is a daily flash report on the progress of HRI-SIM TV1.  If              
you would prefer not to receive future flash reports of HRI-SIM               
ThermoVac 1, please let me know by return e-mail.                             
                                                                              
After all equipment passed checks on Tuesday, June 25, the door of            
the Ball 8 ThermoVac chamber was closed and pump-down began at about          
2:00 pm MDT.  After the pressure had dropped sufficiently, the cooling        
of the shroud with liquid nitrogen was begun at about 7:00 pm MDT.            
With the pressure at about 7.7 x 10^-7 torr, the cooling of the of the        
liquid helium plate with liquid nitrogen was started at about 8:30 pm         
MDT.  As the temperature of the inlet of the liquid helium plate dropped      
to about 190 K, the pressure in the chamber rose to about 1.1 x 10-6 torr.    
When the inlet temperature dropped to about 85 K, the pressure in the         
chamber rose rapidly so high that the ion gauges turned themselves off.       
                                                                              
We turned off the liquid nitrogen supply to the liquid helium plate, and      
the pressure in the chamber began dropping again as soon as the inlet         
temperature had risen above 200 K.  We once again applied liquid              
nitrogen and again saw a leak as the inlet temperature dropped.  We           
decided that there was a temperature-induced leak in one of the supply        
fittings of the liquid helium plate and starting warming the chamber          
to permit servicing of the fittings.                                          
                                                                              
The chamber was returned to ambient temperature and pressure, and then        
opened at about 7:00 am MDT on Wednesday, June 26.  Three accessible          
fittings (two inlet and one outlet) were serviced, with replacement of        
the copper bushings.  One of those bushings showed evidence of                
insufficient applied torque for sealing at low temperatures.  The             
serviced liquid helium plate and fittings were subjected to a leak            
test, which they passed.  The IR FPA was again warm clocked to check          
that it was still working, and then the chamber door was closed at            
8:30 am MDT and the vacuum pumps were turned on.                              
                                                                              
                                                                              
At about 10:00 am we started cooling the liquid helium plate with             
liquid nitrogen to check for temperature-dependent leaks of the               
fittings.  At about 10:20 am we achieved 85 K at the inlet, without           
detectable leakage (no change in chamber pressure).  We cut off the           
liquid nitrogen supply and monitored for 10 minutes, with no sign of          
a leak.  We then started cooling the shroud with liquid nitrogen at           
about 10:30 am, and then started re-warming the liquid helium cold            
plate.  At 2:00 pm, with the shroud nearly full of liquid nitrogen,           
we began cooling the liquid helium plate with liquid nitrogen,                
carefully monitoring the chamber pressure.  There was no sign of              
any leakage as we cooled it down to liquid nitrogen temperature.              
                                                                              
The instrument and chamber are being cooled overnight.  We expect             
them to reach temperatures at which we can detect photons with the            
detector by around 9:00 am Thursday, June 27.  We plan to meet                
at 9:00 am to map out the activities for the day, which are expected          
to include operation of the detector, alignment of the external               
telescope and light source to the SIM slit and detector, and                  
(once the temperature has dropped far enough) switch-over from                
cooling the liquid helium plate with liquid nitrogen to cooling               
with liquid helium.                                                           
                                                                              
In spite of the loss of about 14 hours in the cooling schedule, we            
are still planning to finish alignment, focus measurements, and               
spectral and spatial registration by 5:00 pm on Monday, July 1,               
and thermal balance and all calibration sequences before Thursday,            
July 4.                                                                       
                                                                              
Please let me know if you have any questions or comments.                     
                                                                              
        Dennis