From: ames!FNALD.FNAL.GOV!DROEGE
Subject: Replys to calorimeter questions.
Reply-To: ames!FNALD.FNAL.GOV!DROEGE
Organization: Sci.physics.fusion/Mail Gateway
Date: Tue, 6 Oct 1992 00:31:23 GMT

This is reply to all the calorimeter questions:

Dick Blue is worried that the calorimeter response will not be good for 
pulses.  Thanks to fellow electrical engineer David Cyganski for coming to my 
rescue here.  David has it right.  Not only did we design the calorimeter to 
absorb a large pulse, but we tested it with pulses.  I think we could stand a 
10,000 joule or so pulse with little transient induced error if it just made 
things hot and did not do physical damage.  The internal heat capacity is 2500 
joules per C.  There is a nice curve to look at on page 247 of the Como 
proceedings.  In figure 4 we show the drift for 10 hours, then show the effect 
of 5, 10, 20, 40 and 80 joule impulses.  There have also been some 
improvements since figure 3 which shows 50 joules drift over 10 hours.  
Principally the shell servo was added since the data of this figure.  

Dick, you need to read the description again.  There are four servos of 
interest, not two.  They all do different things.  Two servos doing the same 
thing is the closest thing to a guaranteed oscillator that I know.  The puck-
plate TEC servo just holds constant current.  The plate base servo holds the 
puck-plate temperature difference to zero - it does not care what the 
temperature is.  The heater servo, a very slow servo, drives the heaters to 
maintain a constant puck temperature.  The shell servo drives an aluminum 
shell outside the dewar to hold the same temperature as the inside of the 
dewar.  The shell and plate-base servos are relatively fast.  Thus if the 
inside of the calorimeter gets hot from an impulse, the outside environment of 
the calorimeter just tracks it.  This reduces greatly the radiation losses 
which would otherwise occur.  There are actually more servos in the system.  
A fifth holds constant cell current.  A sixth is usually used for the dummy.  
In fact, there are 12 things we could call servos in the system if we call 
closed loop power amplifiers ( good for about 50 watts ) servos.  For example 
two others hold the electronics and the shunts at constant temperature. 

Dick, it is hard to understand how the whole thing works without the picture.  
There is a very nice engineering drawing made by Cam Tibbals on his fancy CAD 
machine in the Como proceedings ISBN 88-7794-045-X.  Send me your address and 
I will send you a paper.  But give me some time.  It may be faster to get the 
Como proceedings from your library as I do not have a convenient secretary to 
give a note to.  

Sorry, I cannot follow your logic as you have it all wrong.  We measure 
everything so if "there may have been a net heat input into the calorimeter 
during this excursion" we measure it.  If after reading the Como paper you 
think my calorimeter still has a problem I have a nice bet for you.  At 
$10,000 a crack, even money, I will bet you that I can tell when you are 
putting 10 mw into my calorimeter.  You will be given two sets of leads into 
heaters in the calorimeter.  One set which I will measure, will allow you to 
insert a background "noise" to try to confuse the calorimeter, any value up to 
one watt, changed any time except that the last 3 hours before the measurement 
is taken must be fixed.  On the other leads you will be allowed to apply any 
fixed power level up to 1 watt.  After a 24 hour test period I will tell you 
the input power to 10 mw or you will win the bet.  We can repeat this bet 
every 24 hours.  I will guarantee you at least 10 shots at me.  Runs void if 
power fails over 5 minutes, or for power failure in last 3 hours of a bet.  
Please come, bring lots of money.  Room and board included as long as you are 
willing to keep betting.  About two weeks of calibration time with the planned 
heaters will be required before starting the betting. 

Thomas H. Kunich worries about such a complicated system working.  I do too.  
But if we allow complexity to negate experimental results, then we better 
throw out all high energy physics since they stopped using cloud chambers.  I 
too worry about damage to the Peltier devices.  I broke a few on the early 
calorimeter.  Now I do my best to mount them in a configuration that provides 
strain relief.  I give up some on efficiency to provide a soft mounting.  But 
that is what calibration detects.  We have been able to use the same 
calorimeter constant for about a year.  So either the shunts and the ADC is 
tracking the refrigerator TED or they are not drifting.  

Chuck Harrison worries about barometric pressure changes affection the gas 
measurement.  The cell is inside the 2 liter dewar, and is sealed.  The dewar 
is also partially sealed, to that it is hard for it to breathe gas in and out.  
There is only about 50 cc of gas in the 100 cc cell after we subtract the 
space taken up by the 33 cc of electrolyte, the catalyst, the plug, and the 
support structure.  So 3% * 50 cc is 1.5 cc.  We measured about 108 cc of 
left over O2 during charging.  I would be happy with a 1.5% D/Pd measurement.  
There is also anywhere between 0 and 60 cc in the motor driven syringe.  This 
suffers from both barometric and temperature effects.  We can indeed see the 
effect on the gas measurement when the furnace turns on.  But all these 
effects are small compared to what we typically measure.  Something else 
causes gas volume changes over long time periods.  We keep looking. 

Chuck Harrison asks "What is the temperature of the "inside of the dewar"? 
You have to look at the drawing, Chuck, to really answer your question.  I 
will send you paper copies, just have not got to it yet.  There is a 1/16" 
copper inner heat shell that follows the inside surface of the dewar.  It 
makes thermal contact only with the puck.  The paper shows a layer of 
insulation between this heat shell and the inside of the dewar, we now leave 
this out as it is a pain in the neck to install each time a change is made.  
The whole idea is to try to keep a uniform temperature over the inside of the 
dewar.  If all 10 watts were injected at the top of the heat shield, there 
would be about a 10 C drop between the top of the shell and the puck.  So much 
for copper being a "good" thermal conductor.  But most of the power goes into 
the spool which holds the cell, it is 5/8" thick aluminum and makes direct 
thermal contact with the puck.  So in practice, only the catalyst heat is seen 
by the inner heat shield, and it is about 1 watt.  So in the very worst case, 
I would expect about 1 C between the top and the bottom of this shield.  We 
have not measured the inner shield but we did measure the gradient over the 
shell.  This inner shield gradient will cause small changes only with large 
changes of electrolysis current.  For the most part, we expect this error to 
calibrate out.  The radiation loss is not all that large to start with as the 
dewar has an inner radiation shield. (Made in Japan.  I actually had my 
Japanese colleague call and check up on how the dewar was made.) 

John Logajan worries about the long term failure modes of gismoids.  I am 
being straigt up with all of you, so you will note that recently when the 
shell servo failure caused several days data to be larger, it was put up here 
immediately.  I keep looking and worrying.  But I have began to notice that I 
have a lot of runs just like the current one.  These going back as far as the 
summer of 1989.  So it is not new stuff that I am getting excited about.  It 
is the same old stuff that is breaking through my skepticism.  So when I 
finally decipher that gizmiod fracture is the cause of all of this, you will 
hear it.  Meantime, I have started to act as if "anomalous heat" exists.

Tom Droege

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